Category: Science

Science

Feline Reproduction, Part I: Breeding Cycles and Mating

mehshadoweye

Meredith Hemphill

mehshadoweye

Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Cartoon of feline reproductive cycle
Image by Clker-Free-Vector-Images from Pixabay

When I was doing research for a previous article, I learned something that really shocked me. I read two papers about the reasons people gave for surrendering their cats and dogs to shelters. In both, the researchers included some basic pet knowledge questions in the surveys (7, 10). I was floored at how many of the study participants didn’t know the correct answers to some really fundamental questions about canine/feline reproduction and behavior. The surveys addressed a very specific population of people, obviously, but a very important one. If they had known those things before getting a pet, might that have prevented some of those cats and dogs from ending up in a shelter?

I am only one human, but I want to do my part by adding to the available educational resources. One of the knowledge deficits among cat owners surrendering their pets involved feline reproduction (7, 10), so I am going to do a two-part series on that selfsame topic. Throughout, I will bust some commonly-held myths about the feline circle of life.

Female Reproductive Cycle

She-cats, a.k.a. mollies, or queens if they’re mothers, reach sexual maturity at about six months old (2, 6, 8). However, they may hit puberty as early as four months or as late as eighteen (9). The sign that the time has come is that they go into their first estrus, or heat, cycle.

Estrus is a period of sexual readiness during which a she-cat will seek out and accept male cats. In nature, cats usually have a breeding season that is determined by the length of the daylight (5, 9). In the northern hemisphere, it lasts from about January to October (3, 5, 6, 8, 9). However, cats that live in consistently warm climates or indoors-only may experience the breeding season year-round (5, 6, 9). When in season, she-cats go into heat every 2-3 weeks unless they become pregnant (2, 9). Heat lasts an average of six days (6, 8). This pattern of multiple estrus cycles per breeding season is called seasonal polyestry.

So, how do you know if your cat is in heat? It’s unmistakable if you know what to expect, but can actually be pretty alarming if you don’t. She-cats in heat may roll around on the floor, rub up against things, become very affectionate, yowl, and urinate more or mark outside the litter box (2, 3, 5, 6, 8, 9, 12). The yowling of a she-cat in heat is loud, frequent, and unique. Unfamiliar owners often think their cat is ill or in pain. In truth, the crazy sound their cat is making is meant to attract toms from far and wide. She-cats in heat also assume a posture called lordosis, especially when their backs or hindquarters are touched. Lordosis involves lowering their front, raising their rear, treading their hind paws, and moving their tail to the side to indicate receptiveness for mating (9).

If you don’t know what heat looks and sounds like, this is a perfect example.

She-cats are able and willing to mate many times during an estrus cycle, often with multiple toms. Should they become pregnant, they may have kittens with different fathers in the same litter (3, 5, 6). She-cats are fertile from their very first heat and never experience menopause (2, 12). They can also have kittens more than once per breeding season. Basically, cats can have a lot of kittens over their lifetime. The Guinness Book of World Records lists the she-cat with the most kittens as Dusty, a cat from Texas whose last litter in 1952 put her at 420 kittens (12)!

Myth #1 – She-cats should have one heat/litter before being spayed

There is a fairly widespread belief that female cats–and dogs, too–are better off in some way if they have one estrus cycle or one litter in their lives (7, 10). Some people think that she-cats will be healthier if they have one heat or one litter before they are spayed (4). Others believe that she-cats who have kittens are friendlier (6). Neither of these things are true. The evidence shows that she-cats who are spayed before their first estrus are typically healthier (4). And while she-cats do have strong maternal instincts, having kittens does not change a cat’s overall personality (6).

Myth #2 – Cats should not be sterilized at all because it is unnatural/unhealthy.

As my mother always says, “Arsenic is natural.” Natural doesn’t necessarily mean good. Certainly, cats would not undergo surgery of any kind in the wild. Then again, if not for humans enabling their self-domestication, there would be no cats in the wild. I’m pretty sure one could argue what’s natural and what’s not here in circles ad infinitum. What should matter isn’t what’s the most natural but what’s the best for our cats.

In that regard, sterilization is not unhealthy. In fact, it can be quite the opposite. It prevents uterine infections as well as mammary and testicular cancers (1, 8).

Male Reproductive Cycle

Male cats, called toms, reach sexual maturity about the same time as she-cats (2, 13). However, at three months they are producing enough testosterone to start growing their penile spines (13). Yes, you read what you thought you read. Cats have spines on their penises. Quite a few mammals do, actually. There are several possible reasons why this bizarre trait evolved. We will get to why cats are thought to have them later on. The penile spines in cats are testosterone-dependent (9, 13). They finish growing when the tom reaches sexual maturity (9, 13). However, if he is neutered, the spines disappear (9).

Hissing ginger tabby cat
Image by Candid_Shots from Pixabay

The spines aren’t the only sign that a tom is all grown up. Toms begin exhibiting male sexual behavior at puberty, if not earlier. These behaviors include aggression toward other males/fighting, urine spraying to mark territory, and extensive roaming to look for mates (2, 13). Toms that are kept indoors may go to great lengths to escape, especially if there are no eligible she-cats in the household (1, 2). Unlike she-cats, toms don’t exhibit this behavior cyclically. Toms stay interested in mating year-round, although they exhibit decreased interest outside the breeding season if they are exposed to the environmental factors that regulate feline reproductive cycles (13).

Myth #3 – If I neuter my tomcat, he will feel like less of a man.

There is no evidence that cats feel any sexual identity or ego about their reproductive organs (1, 4). Toms do not exhibit an emotional reaction or go into crisis when neutered (4). Neutering does not change their personality (4). It does alter or eliminate the behaviors associate with reproduction, but that does not have a negative impact on a tom’s mental health.

Myth #4 – Sterilizing my cat will make him/her get fat and lazy.

This one came up quite a bit when I was Googling myths about cats to make sure I covered everything. I’ve heard this one before, too. I have to say I wasn’t super satisfied with the answers I saw on some of the other websites. They just said that overfeeding and lack of exercise are the culprits for weight gain, not sterilization. Here’s the thing. There’s a little grain of truth to this myth. Neutering/spaying a cat doesn’t make them fat and lazy, but it does decrease their activity level somewhat, especially for toms.

Cats of both sexes pursue mates. Toms range far and wide searching for she-cats in heat, and may break into or out of houses. That involves a lot of exercise. Once neutered, they have no need to do that. If they are receiving the same amount of food as before, they might gain weight and seem to be getting fat and lazy. The same could apply to she-cats, to a lesser extent. This isn’t to say that sterilization is bad, just that pet parents need to be vigilant about diet and exercise after the procedure.

How Kittens are Made

So Tom and Molly have found each other. Actually, several Toms may have found Molly. Up to six cats may follow a she-cat in heat, but eventually someone will approach her and see if she will accept his advance (13). If she finds him acceptable, she will assume the lordosis position. The tom then bites the scruff of her neck, mounts, mates, and dismounts (5, 8, 13). The whole process takes between 30 seconds and five minutes (8, 13). As the male dismounts, the female gives a yowl, called a copulatory call (8, 9). She then has an “after-reaction,” which frequently includes striking out at the tom, licking her genitals, and rolling around (9).

Two kittens in sexual play
Older male kittens sometimes try to practice mating behavior during play – Image from Veterian Key

No one knows for sure why she-cats often strike at toms after mating (5). It may be that the withdrawal of the male’s penis, covered with backward-facing spines, is painful, but there isn’t any definitive proof one way or the other (5). Those spines are necessary for conception, however. Cats are induced ovulators. This means that the females only release eggs for fertilization in response to a particular stimulus. For cats, that stimulus is mating. The penile spines of the tom stimulating the she-cat’s vagina is the signal for her body to release eggs (9, 12).

One pair of cats is likely to mate about six times within a couple hours before the she-cat declines him, and both may move one to another mate (8, 13). A study at the University of Minnesota found that 73.9% of she-cats who were bred an average of 5.6 times per estrus cycle became pregnant (9). Free-breeding cats are likely to mate many more times than that per heat (5).

Works Cited

  1. American Society for the Protection of Animals. (2017, February 16). Fact or fiction? Spay/neuter myths busted. ASPCA. https://www.aspca.org/news/fact-or-fiction-spayneuter-myths-busted
  2. Bond Vet. (2020, August 12). Cat reproduction: Heat cycles, pregnancies, and more. Bond Vet. https://bondvet.com/b/cat-reproduction
  3. Bukowski, J. A. and Aiello, S. (2011, July). Breeding and reproduction of cats. Merck Veterinary Manual. https://www.merckvetmanual.com/cat-owners/routine-care-and-breeding-of-cats/breeding-and-reproduction-of-cats
  4. Humane Society International. (n.d.). Why spay/neuter is important. https://www.hsi.org/news-media/why_spayneuter_important/
  5. International Cat Care. (2018, July 31). Cat pregnancy. https://icatcare.org/advice/cat-pregnancy/
  6. Llera, R. and Yuill, C. (n.d.). Estrous cycles in cats. VCA Hospitals. https://vcahospitals.com/know-your-pet/estrus-cycles-in-cats
  7. New, J. C., Jr., Salman, M. D., King, M., Scarlett, J. M., et al. (2010). Characteristics of shelter-relinquished animals and their owners compared with animals and their owners in U.S. pet-owning households. Journal of Applied Animal Welfare Science, 3(3), 179-201. http://dx.doi.org/10.1207/S15327604JAWS0303_1
  8. Parrish, J. (n.d.). Reproduction in the canine and feline. Online Reproduction Courses Taught by John Parrish. http://www.ansci.wisc.edu/jjp1/ansci_repro/lec/lec_25_dog_cat/lec25out.htm
  9. Root Kustritz, M. V. (n.d.). Feline reproduction: An overview (proceedings). dvm360. https://www.dvm360.com/view/feline-reproduction-overview-proceedings
  10. Scarlett, J. M., Salman, M. D., New, J. G., Jr., and Kass, P. H. (1999). Reasons for relinquishment of companion animals in U.S. animal shelters: Selected health and personal issues. Journal of Applied Animal Welfare Science, 2(1). 41-57. doi: 10.1207/s15327604jaws0201_4
  11. Syufy, F. (2020, January 7). Guide to cat mating and reproduction. The Spruce Pets. https://www.thesprucepets.com/cat-mating-and-reproduction-555437
  12. Syufy, F. (2020, May 4). Do cats have menopause? The Spruce Pets. https://www.thesprucepets.com/do-cats-have-menopause-555438
  13. Veterian Key. (2016, December 22). Male feline sexual behavior. https://veteriankey.com/male-feline-sexual-behavior/

Published March 7, 2021

Science

Coat Length and Texture Genetics

mehshadoweye

Meredith Hemphill

mehshadoweye

Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

By special request from Emma S.

I am back with the genetics! A friend asked me if I was going to address the genetics of cat fur length in addition to my previous blogs on coat genetics. I wasn’t sure there was enough information to fill up a whole blog, but I dove in anyway. It turns out, there’s plenty. It’s not just the difference between a longhair and a shorthair, but also hairless cats and sort-of-hairless cats and curly-haired cats. Cats are complicated. Genetics is complicated. That’s kind of the fun of it, though. So, this one is for you, Emma. Enjoy.

Longhair ginger tabby cat in autumn woods
Long hair is recessive to short hair – Photo by Steven Iodice from Pixabay

Shorthair vs. Longhair

Let’s start with the basics. If you need a refresher on the principles of genetics, look over the first few paragraphs of my coat color genetics post. Ready? Let’s go. The wild-type, or default, fur for cats is short with no texture modifications. Long hair is recessive to short hair [1-4]. This has been common wisdom for a while, but genetic studies confirmed it in 2007 [1, 2].

The researchers discovered four mutations in the same gene, Fibroblast Growth Factor 5 (FGF5), which cause cats to have long fur [1, 2]. FGF5 mutations were already known to cause hair-length variability in mice and dogs at the time the studies were conducted, so this was not a surprising result [1, 2]. In studies with mice, the FGF5 protein signaled hair to exit the growth phase and enter the static phase [2]. When mutations in FGF5 cause the protein to be nonfunctional, the growth phase of the hair lasts longer [2]. Hence, longer fur.

The four FGF5 mutations in long-haired cats were, creatively, named Mutation 1-4 [2, 3]. Mutation 1 seems to be exclusive to Ragdoll cats [2]. Mutation 2 was only found in Norwegian Forest Cats [1, 2]. Maine Coons are most likely to have Mutation 3, but Ragdolls might as well [1, 2]. Mutation 4 belongs to all long-haired breeds and random-bred longhairs [1, 2]. So far, there is not indication that any gene besides FGF5 contributes to the longhair phenotype. The fact that at least four mutations in this gene exist, three of them breed-specific, suggests that the trait has arisen multiple times through a similar mechanism. This is probably because, in certain environments, long fur is advantageous. It has also sometimes been artificially selected for.

Now, we know that there are not just two lengths of cat fur, one long and one short. There are many variations within both the shorthair and longhair categories, and some cats are kind of in-between. This is because very few things are affected by just one gene. An unknown number of modifier genes determine the exact length of a cat’s hair relative to their genotype at the primary hair length locus [4].

Hairless, or Near Enough

Some cats or breeds are more or less hairless. True hairlessness is almost unheard of. Hairless cats present with a variety of traits that we call “hairless.” Most have very thin coats that look as if they aren’t there at all. Some have fur that thins drastically in only certain places. In either case, the degree of “hairlessness” can vary widely. As one would expect with so much natural variation, more than one mutation causes the different patterns of feline hairlessness. Sometimes the trait is dominant, and sometimes it is recessive [3, 4].

Four cream Sphynx kittens on blue cat bed
The Sphynx trait is caused by the hr mutation – Image by mjlovesmm from Pixabay

A recessive mutation dubbed hr gives the easily-identifiable Sphynx its hairless phenotype [3, 4, 5]. The Sphynx is a typical hairless breed with an extremely thin, downy coat that gives the appearance of baldness [5]. The hr allele is a mutation in the Keratin 71 (KRT71) gene [5]. The keratin 71 protein is expressed in the inner root sheath of the hair follicle and is important for the normal formation of the hair [5]. The hr mutation does not prevent hair from forming, but the hairs are easily dislodged because the hair bulbs are weak, resulting in the distinctive naked appearance of the Sphynx [5].

The Russian hairless breeds, Peterbald and Donskoy, carry the semi-dominant Hp mutation [4, 6]. Other genes affect how strongly the Hp hairlessness allele is expressed [4, 6]. The cats’ coats range from a brush coat–sparse, rigid, curly fur–to hairless all over [4]. Hairless mutations identified in British and French cats, hd and h respectively, are recessive [3, 4]. Sadly, hd is also a lethal mutation [4].

The Lykoi breed displays partial hairlessness. They have a thin coat all over and a hairless face, sometimes with other patches of hairless, especially on the legs. Lykoi molt all of their hair at least once in their life and may molt as often as every shedding season. This arguably makes them a breed that is truly hairless, albeit only for short periods of time. Six different mutations have been found to cause the Lykoi phenotype, but all of them are mutant alleles of the same gene, lysine demethylase and nuclear receptor corepressor, abbreviated HR for “hairless” [7]. Mutations in HR also cause hair abnormalities in humans, mice, sheep, and macaques [7].

Rexoid Variations

Curly fur occurs naturally in quite a few mammals, including dogs, rabbits, and cats. There are five recognized breeds of curly-coated cats, per the Cat Fanciers’ Association and The International Cat Association: American Wirehair, Cornish Rex, Devon Rex, LaPerm, and Selkirk Rex. Several other potential rexoid breeds have been proposed, including the German Rex and Oregon Rex. While all of these cats–and some random-bred cats–have curly coats, there are a lot of different causal mutations.

Remember the KRT71 gene? One kind of mutation in it causes the Sphynx’s hairlessness, but a different KRT71 mutation makes the Devon Rex’s pelt curly [5]. The Devon Rex mutant allele, re, is recessive to the wild-type allele but also to the hr Sphynx allele [5]. Devon Rex cats were used in the early Sphynx breeding programs, so some Sphynx still have one hr and one re allele, but they look just like any other Sphynx [5].

Lilac cat with curly fur on wood table
Selkirk Rexes can have long or short hair – Image by athree23 from Pixabay

A recessive mutation also causes the Cornish Rex’s curly coat, but in their case the gene in question is lysophosphatidic acid receptor 6 (LPAR6) [8]. The mutant allele, known as r, causes the Cornish Rex to only develop an undercoat, one of the three layers of a normal pelt, and a curly one at that [8, 9]. Humans who are homozygous for LPAR6 mutations have a similar phenotype known as “wooly hair” [8]. Because the Cornish Rex was used to found the German Rex, r is in the genetic background of German Rexes, too [8].

Unlike the Devon and Cornish, the Selkirk Rex mutation, Se, is dominant, although incompletely dominant [9]. This means that cats homozygous for the mutation have a more dramatic phenotype: thinner coats, tighter curls [9]. And, wouldn’t you know it, Se is an unique mutation of our old friend, KRT71 [10]. Both KRT71 and LPAR6 are genes that maintain normal hair growth [5, 8]. It makes sense that different mutations in the same or similar genes would cause similar results.

Works Cited

  1. Drögemüller, C., Rüfenacht, S., Wichert, B., and Leeb, T. (2007). Mutations within the FGF5 gene are associated with hair length in cats. Animal Genetics, 38(3), 218-221. https://doi.org/10.1111/j.1365-2052.2007.01590.x
  2. Kehler, J.S., David, V.A., Schäffer, A.A., Bajema, K., et al. (2007). Four independent mutations in the feline Fibroblast Growth Factor 5 gene determine the long-haired phenotype in domestic cats. Journal of Heredity, 98(6), 555-566. https://doi.org/10.1093/jhered/esm072
  3. Basepaws. (2019, July 14). Cat coat genetics. Basepaws, Inc. https://www.basepaws.com/blog/cat-coat-genetics/
  4. Hartwell, S. (n.d.) Genetics of colour and conformation. MessyBeast. http://messybeast.com/cat-genetics-basics.htm
  5. Gandolfi, B., Outerbridge, C.A., Beresford, L.G., Myers, J.A., et al. (2010). The naked truth: Sphynx and Devon Rex cat breed mutations in KRT71. Mammalian Genome, 21, 509-515. https://doi.org/10.1007/s00335-010-9290-6
  6. Zhigachev, A.I., Vladimirova, M.V., and Katser, I. (2000). Phenotypic and genotypic characteristics of Russian hairless cats. Genetika, 36(4), 538-544. https://europepmc.org/article/med/10822817
  7. Buckley, R.M., Gandolfi, B., Creighton, E.K., Pyne, C.A., et al. (2020). Werewolf, there wolf: variants in Hairless associated with hypotrichia and roaning in the lykoi cat breed. Genes, 11(6), 682. https://doi.org/10.3390/genes11060682
  8. Gandolfi, B., Alhaddad, H., Affolter, V.K., Brockman, J., et al. (2013). To the root of the curl: A signature of a recent selective sweep identifies a mutation that defines the Cornish Rex cat breed. PloS One, 8(6), e67105. https://doi.org/10.1371/journal.pone.0067105
  9. Basepaws. (2019, July 15). Curly cat coat: A special kind of eye candy. Basepaws, Inc. https://www.basepaws.com/blog/curly-cat-coat/
  10. Gandolfi, B., Alhaddad, H., Joslin, S.E.K., Khan, R., et al. (2013). A splice variant in KRT71 is associated with curly coat phenotype of Selkirk Rex cats. Scientific Reports 3, 2000. https://doi.org/10.1038/srep02000

Published November 1st, 2020

Updated June 14th, 2023

Science

Through Glowing Eyes: What Do Cats See?

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Meredith Hemphill

mehshadoweye

Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Joon has a strange habit. Well, a lot of strange habits, actually, but I’m thinking of one in particular. She will stare up at the ceiling at night and yowl. At first, I thought she was hearing our upstairs neighbors. Then I remembered that we lived on the top floor. Is my cat insane, or are there demons in the walls? There’s no way to know. I now live in a detached, single-family home, and she still does the same thing. I’ve never known any other cat to do that, but cats are infamous for looking off into space intently and kind of spookily. Obviously, cats and humans see the world very differently. If you have ever wondered what on Earth your cat is looking at, or just how the world appears to them, then you have come to the right place.

Eyeball diagram
Image from Cat-World.com

Let’s start with the basics: eyeballs. The fundamental structure of the cat eye is pretty similar to that of a human, but there are some important differences that affect how they perceive what’s in front of them. If you haven’t taken an anatomy class since high school and need a refresher on what the parts of the eye in the diagram at left do, the National Eye Institute has a short video that goes over the highlights.

Although it doesn’t so much affect the way they see, while we’re on the subject of eyes it bears mentioning that cats, like many other mammals, have a nictitating membrane inside of their eyelids. This membrane, often called the “third eyelid,” is a semi-transparent, whitish color, and cats close it when they need to protect their eyes from scratches, like if they’re squeezing through a bush [1]. The nictitating membrane should not be visible normally; this could be a sign of inflammation or disease and is a reason to visit the vet [1, 2].

As with most things about the cat body, their eyes are exquisitely adapted to the life of a crepuscular hunter. “Crepuscular” means most active at dawn and dusk, when they are able to maximize the proportion of prey animals they have access to. Both cats and humans have forward-facing eyes, but the position of cat eyes gives them a somewhat wider field of view, about 200 degrees to our 180 degrees [3-5]. Cats also have much larger eyes than humans relative to the size of their heads, allowing them to take in more light in the dimmer hours of the early morning and late evening [2].

Another feature that helps cats see in dim light is a layer of reflective cells behind their retinas called the tapetum lucidum, which is Latin for bright/shining carpet. The tapetum lucidum is common in nocturnal and crepuscular mammals. The mirror-like cells reflect light that has gone through the retina back for a second pass. When you take a picture of your cat with the flash or open the door to find them in a dark room and see their eyes seeming to glow like some kind of hellspawn, that’s just their tapetum lucidum reflecting light at you.

Green cat eyes
Elliptical pupils mean more control over light – Image by Christel SAGNIEZ from Pixabay

There is research to suggest that the slit, vertical pupils of cats are also an adaptation to a crepuscular habit. It allows their pupils to change in size drastically for greater control over the amount of light that reaches their retinas [6]. The change in pupil area between the constricted and dilated states is estimated to be 135- to 300-fold, while human pupils can only change in size about 15-fold [6]. Think about how much the amount of sunlight can change around dawn and dusk, versus during the daylight hours when humans are meant to be most active. The ability to significantly adjust the amount of light let into the eye has likely served cats well.

All this means that cats can see much, much better than we can in low light. However, everything in biology involves trade-offs. For one, cats are rather near-sighted. They can only see clearly up to about 20 ft (6 m) away, while humans can resolve details at 100-200 ft (30-60 m) [3-5]. Cats have also prioritized one type of retinal cell, or photoreceptor, over another.

Cone cells help see details and colors. Rod cells are excellent at absorbing dim light and catching quick movements. Humans have lots of cones, including three types that specialize in picking up the colors red, green, and blue. Cats have lots of rods instead, six to eight times as many as humans [1, 4]. This assists in seeing in low light and in picking up the small, rapid movements of prey [3].

This heightened awareness of tiny movements may also explain the way cats seem to look at nothing. They may just have noticed something too small to register with you. Or your house is haunted. Who knows? Although the abundance of rod cells has great advantages for cats, it causes them to have less visual acuity and poorer color vision than humans. Obviously, they have done quite well for themselves even so. After all, did you see that ghost zip through your kitchen? I don’t think so.

There remains some debate as to the color vision of cats. They definitely see some color. According to some scientists, they may see the world in shades of blue, gray, and yellow [4]. A 2014 study found that cats may actually be able to see some colors in the ultraviolet spectrum, so while they can’t see all the colors we can, it’s possible that they can see colors we can’t [7]. This is because the lenses of their eyes don’t remove all the ultraviolet rays before light reaches their retina, unlike ours, which absorb UV [7]. The study found that the lenses of cats allowed 58.9% of UVA radiation through [7]. Whether there is an evolutionary advantage to this remains unknown.

Brown tabby cat face
The feline cornea allows UVA rays through – Photo from Pixabay at Pexels

Perhaps the greatest question of all is, how do our cats see us? A lot of research has been conducted to assess whether animals recognize faces, and a wide variety of species, including wasps and fish, have been demonstrated to recognize the faces of their own species. Recognizing the faces of other species is a much more difficult task, however. I personally couldn’t recognize the face of a wasp, in all fairness, although I do know just about every stripe and speck on my Joon-bug. Then again, it helps that she’s got so many of those. Well, it turns out that to cats, all human people look alike. Fair enough, honestly.

Lomber and Cornwell trained dogs and cats to choose one of two images presented for a treat, regardless of which image they chose [8]. The image pairs were 1) their handler and an unfamiliar human face, 2) an animal they lived with and an unfamiliar animal’s face, 3) a natural scene they’d learned before and a new one, or 4) two unfamiliar natural scenes [8]. Dogs and cats both showed a strong preference for the face of a familiar animal and a familiar natural scene, choosing that which they knew at least 85% of the time [8]. Dogs kept up the preference for the face of their handler, but cats only chose the familiar human face 54.5% of the time, equivalent to a coin flip [8].

Cats are certainly capable of recognizing their people, but they evidently do not recognize our faces, although they can recognize each other’s faces. As animals that are just barely domesticated, and only because they chose to be, perhaps this should be no surprise. What need would a cat have to recognize human faces in its wild state? Cats have met us a lot farther over than the middle. It’s the least we can do to try and see things their way.

If you want to actually see what the world would look like through a cat’s eyes, artist Nickolay Lamm took simple photographs and then manipulated them to appear as they would to a cat, then juxtaposed the two images [3]. You can see the results of the project in the Wired article linked below.

Works Cited

  1. Gelatt, K.N. (2018, August). Eye structure and function in cats. Merck Vet Manual. https://www.merckvetmanual.com/cat-owners/eye-disorders-of-cats/eye-structure-and-function-in-cats
  2. Farricelli, A. (2019, August 12). The anatomy of a cat’s eye. PetHelpful. https://pethelpful.com/cats/The-Anatomy-of-a-Cats-Eye
  3. Drake, N. (2013, October 16). This is how cats see the world. Wired. https://www.wired.com/2013/10/cats-eye-view/
  4. Thrive. (2019, April 12). Can cat’s see color? https://resources.thrivevet.com/can-cats-see-color/
  5. Ghose, T. (2013, October 16). Feline vision: How cats see the world. Live Science. https://www.livescience.com/40459-what-do-cats-see.html
  6. Calderone, J. (2018, June 30). Here’s why cats have such strange, haunting eyes, explained by science. Science Alert. https://www.sciencealert.com/here-s-why-cats-have-such-weird-eyes
  7. Douglas, R.H. and Jeffery, G. (2014). The spectral transmission of ocular media suggests ultraviolet sensitivity is widespread among mammals. Proceedings of the Royal Society B, 281(1780). https://doi.org/10.1098/rspb.2013.2995
  8. Lomber, S.G. and Cornwell P. (2005). Dogs, but not cats, can readily recognize the face of their handler. Journal of Vision, 5(8), 49, 49a. https://doi.org/10.1167/5.8.49

Published September 6th, 2020

Updated September 30th, 2023

Culture, Science

Hemingway’s Cats and Feline Polydactyly

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Meredith Hemphill

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“One cat just leads to another.” –Ernest Hemingway

If you visit the Hemingway House in Key West, Florida, USA, you will find that there is something special about the historic home: it is crawling with cats. This is no feral cat colony run amok. The cats here are friendly and well-cared for, happy to be petted or to sit in the laps of guests (1). But if you do get up close with one of these cats, you may notice something special about them, too. About half of the cats at the Hemingway House have extra toes (1)!

White two-story house with trees
The Hemingway House – Image by Michelle Maria from Pixabay

Polydactyly is Greek for “many fingers.” It is a genetic condition that causes extra digits. The trait has been found in humans, mice, dogs, cats, horses, cattle, goats, sheep, springboks and birds (2). Polydactyly is seen more often in cats than any other mammal, although no one knows exactly why (3). Sailors used to consider cats with extra toes even luckier to have aboard than a normal cat. It was thought that they were better mousers and could keep their balance better on rough seas (4). It’s suspected that sailors and their lucky ship’s cats are the reason that polydactyl cats are particularly common along the northeast coast of North America (4), and the same may explain their prevalence in Key West.

According to legend, a nautical friend of Ernest Hemingway gifted him a white, six-toed cat variously named Snow White, Snowball, or Princess, depending upon who you ask. Snowball then snowballed into up to eighty cats living at his Key West home, many of which inherited her extra toes. Today, many cats around Key West, not just at the Hemingway House, are polydactyl.

The truth of this tale is uncertain. While Hemingway certainly had a fondness for cats, some friends and family members say there was no Snow White/Snowball/Princess, or that he never kept cats in Key West at all. Whatever the truth may be, when the Hemingway House was turned into a museum in 1964, it abounded with cats. The family who kept up the museum chose to care for the cats as well, however they might have come to be there. Hemingway named many of his cats after famous people, and this tradition is kept up with Hemingway’s cats today (1).

Orange and white polydactylcat on pile of shirts
Archie Andrews has taken over the gift shop. Count the toes carefully. He has an extra on each front paw! – Photo by Hemingway Home Museum

In honor of the legendary connection between Hemingway and the lucky six-toed cats, polydactyl cats are often called Hemingway cats no matter where they live. The average cat has five toes on each front paw (including the dew claw) and four toes on each hind paw, for a total of eighteen. Polydactyl cats can have a wide variety of numbers and positions of extra toes. The extras are usually on the front paws or on both the front and back, but rarely on only the hind paws. Two of the most common configurations are called “mitten paw” and “patty paw” (2).

“Mitten paws” have extra toes to the side of the normal toes, causing the cat to look like they have mittens on (4). “Patty paws” have extra toes in line with the other toes, resulting in paws that just appear rather large (2). However, other configurations are possible. Polydactyly is a complex trait. It is caused by a dominant mutation that affects limb development very early on, hence the wide array of possible presentations (3).

Occasionally, polydactyl cats can have health problems such as nail infections, ingrown claws, or bone abnormalities (3, 4). In the vast majority of cases, however, the cats have no difficulty at all. It’s thought that in some environments, polydactyly may even be beneficial. Although the old idea that cats with extra toes are better hunters is generally regarded as myth, it was observed long ago that Maine Coon cats, which evolved as a breed in the wild in New England, had a high incidence of polydactyly. Up to 40% of Maine Coons had extra toes before breeders began to select the trait out (4). It is believed that the extra toes helped give Maine Coons even larger paws than they already have, big paws they use like snowshoes to prevent sinking in deep snow during harsh New England winters (4).

Brown, polydactyl tabby cat in flower bed
An example of “mitten paws” – Photo by Georgy Trofimov on Unsplash

There’s no need for snowshoes in Florida, but the cats at the Hemingway House aren’t required to hunt for themselves, anyway. They are fed, pampered, and seen by a vet once a week. Most are spayed and neutered, with a few left intact to keep the colony at about forty to fifty cats. Although guests are not allowed to sit on the antique furniture, the cats get a pass, because this is their house. I have paid the Hemingway House a visit myself and can vouch for how delightful an experience it is to be surrounded by so many happy cats in a beautiful house. Their unique feet is an added bonus.

If you would like to visit the Hemingway House, the address is 907 Whitehead Street, Key West, FL 33040. They ask that you do not pick up the cats or bring any catnip or catnip toys with you. Apparently this happens a lot and has caused cats to fight over the limited herbal offerings. I imagine the same goes for bringing treats or anything else. No reservations are required, and each ticket includes a 30-minute tour.

Fun Facts

  • US President Theodore Roosevelt kept a polydactyl First Cat named Slippers while he was in the White House.
  • The current World Record for most toes on a cat belongs to Jake, a ginger tabby tom with 28 toes (seven on each paw).
  • There is an unsubstantiated report of a 32-toed cat named Mickey Mouse from 1974 (eight on each paw)!

Works Cited

  1. Hemingway Home Museum: https://www.hemingwayhome.com/cats/.
  2. Hamelin, A., et al. (2016). Clinical characterisation of polydactyly in Maine Coon cats. Journal of Feline Medicine and Surgery, 19(4), 1-12. DOI: 10.1177/1098612X16628920
  3. Basepaws. (2019). Genetics of polydactyly: Celebrating the Hemingway cats. https://www.basepaws.com/blog/genetics-of-polydactyly-celebrating-the-hemingway-cats/.
  4. Manhattan Cat Specialists. (2019). Polydactylism (extra toes). https://www.manhattancats.com/blog/2019/august/polydactylism-extra-toes-/.

Published June 6th, 2020

Updated November 4th, 2020

Behavior, Science

Why are cats crazy for catnip?

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Catnip flowers
Photo by S W Yang from FreeImages

A catnipped cat is a sight to behold. They lick and chew the wondrous herb, rub their faces in it, and roll around on the ground. Sometimes they drool or run screaming through the house. Some cats, on the other hand, don’t seem to care for catnip at all. Cats are truly a never-ending source of entertainment and mystery. Scientists of many stripes have been investigating the relationship between cats and catnip since at least the 1960s, so many questions have been answered, although some still remain.

Catnip, also called catmint or catwort, usually refers to the species Nepeta cataria, but can include any of the 250 or so species in the genus Nepeta. Cats react to quite a few of these species, not only Nepeta cataria, the most well-known catnip. Catnips are members of the mint family. Most of the species are perennials. They have opposite leaves, grey-green foliage, and small flowers in a variety of colors. N. cataria has pink or white flowers. Catnip is aromatic even to humans, smelling minty and perhaps lemony. It is the scent of catnip that attracts felines to the plant so strongly.

Not all cats care for catnip, but it does seem to be the case that all species of cats have the catnip reaction, or at least a lot of them. Wild cats large and small have been observed reacting to catnip in the same way that domestic cats do, although just like housecats, not all of their wild brethren are fond of the stuff, either. The chemical in catnip that causes this more-or-less universal reaction is nepetalactone, a volatile oil produced in glands on the underside of the leaves (1). Nepetalactone repels insects, so it is thought that the plant produces the oil in order to repel herbivorous bugs (2), but the chemical appears to mimic a natural cat pheremone. At least, that’s the theory, given that the behaviors exhibited during the catnip reaction bear a striking resemblance to some of those of a she-cat in heat (3).

Wild cats big and small playing with catnip

When a cat inhales nepetalactone, the volatile oil binds sensory receptors which trigger neurons in the olfactory bulb of the brain (4). These neurons, in turn, relate the message to brain regions that cause an emotional and sexual response to the stimulus (4). Catnip is sometimes called an “euphoriant” for cats, although in truth we can only guess at what they are feeling.

Inhaling the scent of catnip is usually stimulating while eating catnip mellows cats out, although individual cats can react to catnip differently. Some may even become aggressive toward other cats or people, so keep an eye on kitty until you know how they are going to behave under the influence, so to speak. The entire reaction lasts about ten minutes, after which the cat cannot react again for up to two hours. Catnip is considered non-addictive and safe. Too much catnip at once can cause a cat to get sick, like anything else. You might want to store your catnip well out of reach if you buy a large amount. Nepetalactone loses potency over time, so it’s a good idea to keep dried catnip in the freezer to avoid this anyway.

Ginger tabby in catnip plant
Image by CatCrazy from Pixabay

What about cats who are indifferent to catnip? There are two possible reasons. First, kittens, with possibly some rare exceptions, do not react to catnip and may even avoid it (5). Cats begin to experience the excitement of catnip around six months of age, when they reach sexual maturity. Interestingly, this occurs even when cats are spayed or neutered (5). But some cats never do become interested in the herb, and this is due to genetics. There is a dominant allele which confers the catnip reaction on cats who inherit at least one copy of it at that gene (5). Anywhere from 20-50% of cats are estimated not to react to catnip and therefore to have two recessive alleles for that trait. What that means for their biology otherwise is hard to say, as the reason for cats reacting as they do remains a matter of speculation.

If you have a cat that likes catnip, you might consider growing a pot of it yourself. Mint species tend to be sprawling and invasive–catnip has already become weedy and invasive outside its native Eurasia and Africa–so I would recommend confining it to a pot. But then you would always have fresh catnip available for your kitty and, for that matter, yourself. Catnip has been used medicinally for hundreds if not thousands of years. In addition to its repute as a natural bug repellent (albeit only for a few hours at a time), it has a mild sedative effect on the human brain similar to chamomile. Herbal teas of catnip may be good for anxiety or insomnia, or just good for relaxing after a hard day.

Native Americans once used catnip to treat infant colic, and the herb is reputed to be good for migraines, digestive complaints, and as a paste for arthritis (4). I cannot personally vouch for these healing properties, but I can say that I kill every plant I try to grow, and even I managed to grow a nice, healthy catnip plant for several months, which is probably a record for me. The cats loved the fresh catnip, but I did have to move the plant outside to prevent them from just munching the whole thing to the dirt. At least I knew they liked it.

Fun fact: other plants, such as valerian and silver vine, affect cats the same way as catnip!

Catnip bubbles!

Works Cited

  1. John Innes Centre. (2018, December 11). How catnip makes the chemical that causes cats to go crazy. ScienceDaily. www.sciencedaily.com/releases/2018/12/181211103125.htm
  2. Eisner, T. (1964). Catnip: Its raison d’être. Science, 146(3649), 1318-1320. DOI: 10.1126/science.146.3649.1318
  3. Palen, G.F. and Goddard, G.V. (1966). Catnip and oestrous behaviour in the cat. Animal Behaviour, 14(2-3), 372-377. https://doi.org/10.1016/S0003-3472(66)80100-8
  4. Turner, R. (2007, May 29). How does catnip work its magic on cats? Scientific American. https://www.scientificamerican.com/article/experts-how-does-catnip-work-on-cats/
  5. Todd, N.B. (1962). Inheritance of the catnip response in domestic cats. Journal of Heredity, 53(2), 54-56. https://doi.org/10.1093/oxfordjournals.jhered.a107121

Published April 17, 2020

Updated January 30, 2021

Science

Coat Pattern Genetics

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

A few weeks ago I wrote about the genetics of coat color in domestic cats. Now, to follow up, I am going to dive into the wild world of pattern genetics. If you would like a review of basic genetic principles, click the link to the previous article. There is a quick rundown in the beginning.

In genetics, the “wild type” is the genetic profile of an organism that is most common under natural conditions. The wild type ancestral cat was a mackerel tabby with black stripes, short fur, and no white spots [1]. Today, of course, cats come in a wide variety of patterns, even those who live feral and are subject to natural selection. Both human intervention and spontaneous mutations are to credit for this diversity.

Tabby

Let’s start with tabbies, the original cat pattern. Many other cat species share the tabby pattern with domestic cats, usually in the form of rows of spots–spots and stripes are closely related genetically in cats [2, 3]. In order to have a tabby pattern, a cat must first have at least one dominant allele at the agouti locus. The dominant agouti allele causes each individual hair to have bands of darker and lighter pigmentation. This is required for tabby coats and several other patterns which we will come to later.

The wild type mackerel tabby pattern is characterized by thin, parallel stripes darker than the background color. Mackerel tabby is the dominant allele at the Tabby, or Ta, locus, so only one TaM allele is required for the mackerel tabby pattern. The “blotched” or “classic” tabby has large, marbled stripes. This pattern occurs at the same Ta locus. The blotched allele is recessive to the mackerel.

Spotted tabby kitten with toys
Spotted tabby kitten – Photo by Kim Davies on Unsplash

At least two other alleles are involved in tabby patterning, although it was previously thought that there was only one [4]. The Ticked locus has been definitively identified as influencing the type of tabby pattern a cat’s coat has, but another unknown locus or loci may effect how the patterns present [4].

The Ticked locus is epistatic to the Tabby locus, meaning that the genotype at the Ticked locus has an impact on the phenotype coded for by the Tabby locus. If a TiA allele is present at the Ticked locus, the cat will have ticked/agouti fur all over the body, as the TiA allele masks the effect of the Tabby locus. This is usually called an Abyssinian Tabby because the ticked coat is characteristic of the Abyssinian breed. If there are two Ti+ alleles, the cat will not be an Abyssinian tabby, and whatever genotype is at the Tabby locus will show through. Cats with one TiA and one Ti+ allele tend to have some striping on their faces, legs, and tails despite being Abyssinian tabbies.

Tired of talking about tabbies? I hope not, because we still have to go over the special cases! Spotted tabbies have stripes that are broken into spots of varying size. An unknown modifier gene or genes are believed to alter the expression of mackerel tabby stripes to create spotted tabbies [4]. The charcoal Bengal/Savannah patterns are a variety of tabby caused by an agouti gene inherited from the Asian Leopard Cat. Charcoal tabbies have decreased red tones in their coats, giving them a cooler, grayer appearance. They also have a dark nose and “Zorro” mask on the face and a dark cape down the back. There are a shocking number of other types of modified tabby, but the genetics behind them are hazy. I will leave you with a handy infographic showing you what they look like and move on to the next pattern.

Table of tabby patterns
Chart of Tabby Patterns – Image from messybeast.com

Silver and Gold

Agouti hairs would normally have alternating bands of light and dark pigment corresponding to the cat’s coloring, but there are a couple genes, or possibly gene families, which can change the way pigment is deposited on agouti fur. A dominant mutation of the Silver/Inhibitor gene inhibits production of phaeomelanin, the yellow or red pigment in cat hair. This causes the light portions of agouti bands to be very pale or colorless rather than yellow. This mutation, by itself, causes tabbies to be silvery and solid-colored cats to have a pattern known as smoke, where there is a pale/colorless band at the bottom of their hair shafts. Their white undercoats give them a “smoky” appearance when their fur is ruffled.

On the other hand is the Wide-Banding trait, only present in agouti cats. It is thought to be caused by a group of related genes, but this is still unclear, and no one quite knows how they work. Whatever the root cause, wide-banding causes the agouti bands on the hair shaft to be larger and/or more numerous. There is a high degree of variation in the way this can present, lending credence to the idea that there is more than one gene involved.

Silver Persian and kitten in cat tree
Silver shaded Persian (top) – Image by RomeoEbaloo from Pixabay

When Wide-Banding occurs alone, the cats are sometimes referred to as “golden” due to the higher degree of yellow pigment in their coats. However, the Silver and Wide-Banding traits can occur together to create other patterns. In either case, cats with Wide-Banding that leaves only the very tip of the hair shaft to show their normal pigmentation are said to be tipped. Those with more of the darker pigment on the end of the shaft are called shaded. There are even more names among cat fanciers for the many different combinations of these phenotypes, but we have more to cover.

Color-point

We touched on color-pointing in the Siamese breed profile, and we will probably circle back to it with other breeds. It is a popular pattern which has been deliberately bred into quite a few breeds. Color-pointing is a kind of partial albinism. These cats have a mutation in tyrosinase, an enzyme required for the production of melanin. The mutated enzyme will only activate below 33 degrees Celsius. As such, the mutation causes temperature-sensitive pigmentation, with the most color deposited on the coolest extremities of the body. There are actually two color-point alleles that result in three somewhat different phenotypes. Both alleles are recessive to the wild type allele but are codominant to each other.

Brown and cream cat with blue eyes
Tabby Himalayan color-point – Photo by Nathz Guardia on Unsplash

The Himalayan phenotype has the strongest color restriction. It is seen in cats with two cs alleles. These cats have blue eyes and a very light-colored torso, typically cream or ivory. The color-pointing is very high-contrast. The intermediate phenotype is known as Mink and is typical of the Tonkinese breed. They have one cs allele and one cb allele. The eyes are aqua and the torso color is more similar to the points.

The Sepia color-points are not all sepia but are named for the brown Burmese cats wherein the pattern was first identified. This phenotype has copper eyes and is quite low-contrast, with the points and the torso being fairly similar in color. Sepia color-points have two cb alleles. All color-point cats can have points of any color, and the points can also be patterned. Sometimes color-point and white spot patterns can be combined to form new patterns, such as white mittens (characteristic of Birmans) or bicolor. For more on white spots, see the coat color article.

There are a LOT of miscellaneous mutations that I could talk about which are not so widespread or well-documented as the ones I have covered here today. If you would like me to go over them in the future, please let me know. I would be glad to do so. You can also tell me if you never want me to do this again. Feedback is always welcome. :3

Works Cited

  1. Hampton, N. (1998, March 4). Coat color and pattern genetics of the domestic cat (Felis catus) [PowerPoint slides]. The University of Texas at Austin. https://facultystaff.richmond.edu/~lrunyenj/bio554/cat/index.htm.
  2. Thomas, E.M. (1994). The tribe of tiger: Cats and their culture. Simon and Schuster.
  3. Zielinksi, S. (2012, September 20). Same gene guides cheetah and tabby cat coat patterns. Smithsonian Magazine. Link here.
  4. Eizirik, E., et al. (2010). Defining and mapping mammalian coat pattern genes: Multiple genomic regions implicated in domestic cat stripes and spots. Genetics, 184(1), 267-75. DOI: 10.1534/genetics.109.109629

Published April 10th, 2020

Updated June 14th, 2023

Science

Here’s to Your Health

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

As you may have noticed, these are rather trying times. Personally, I’m rather stressed. I have also lost all sense of time and have no idea what day I’m even posting this on. I am very much the type of person to stay in more than I go out, but quarantine measures have their effect on even the most introverted among us. Not to mention the anxiety of, well, everything, really. There’s a lot to worry about these days. However, if you have a cat–or several–there is good news! Scientists have demonstrated that cat ownership is beneficial to both mental and physical health. I could have told them that, and I bet you could have, too, but let’s go over the evidence just to make ourselves feel better, why don’t we?

This is what I’ve been doing for two weeks – Image by balzacan from Pixabay

The first thing I do every morning is spend a few minutes, sometimes longer, petting my cat in whatever fashion she demands. She certainly enjoys it, attention hog that she is, but it also helps me start my day feeling happy and relaxed. For me, merely watching a cat sleep can melt my stress away. It isn’t just me, as studies have found biological markers affected by contact with cats. A study with college students at the University of Northern Iowa determined that the students experienced a “small but significant decrease” in blood pressure immediately after being allowed to hold a cat or dog (1).

A study at Washington State University measured the levels of the stress hormone cortisol in the saliva of students before and after they a) interacted with provided cats or dogs, b) watched other people interact with the animals while standing in line and waiting, c) watched a slideshow with pictures of the pets the lucky experimental group interacted with, or d) sat in a waiting room for 10 minutes (2). The group that was actually able to pet and play with furry friends had significantly lower cortisol levels afterwards, an indicator of lower overall stress (2). Not everyone is a college student, of course, but it goes to show that the presence of a pet, even an unknown one, can demonstrably relieve stress. The next time someone calls you a crazy cat lady (or gent or neither or both), tell them the cats make you less crazy.

Gray and white cat with wooden heart
Cats are good for your heart <3 – Image by pasja1000 from Pixabay

A purring kitty sitting in your lap may be the pinnacle of relaxation, but did you know it may promote physical healing? Purring is one of the great mysteries of the feline family. Cats purr when they are content, but they are also known to purr when ill or injured. A study that aimed to uncover why recorded the purrs of forty-four felids from several species, including the domestic cat, and analyzed the frequencies of the sounds (3). All of the felids purred with strong frequencies in the 25-150 Hertz range (3).

In particular, the researchers noted that the pumas, ocelots, servals, and domestic cats produced “fundamental, dominant, or strong frequencies” at 25 and 50 Hz (3). Studies have found that frequencies between 20 and 50 Hz aid in the growth, healing, and strengthening of human bones (4). The same four species displayed a strong harmonic at 100 Hz, a frequency associated with treating pain, swelling, wounds, and labored breathing (3). Felines may have evolved purring, at least in part, as a mechanism for self-healing, but it now allows our house panthers to heal us as well.

Any cat lover would say that forging a bond with a cat can be healing, and they would probably say that loving a cat is good for the heart. The data would also say that it literally is. Having a cat has been associated with a decreased risk of dying from cardiovascular disease, including heart attack and stroke (5, 6). Even having simply owned a cat in the past conferred these benefits in one study (5). Ogechi et al only found this association with female cat owners. However, an Australian study demonstrated that all cat owners make fewer trips to the doctor and are less likely to be on medication for heart or sleeping problems than those without pets (7). Good news all around!

White and black cat laying beside baby
Preventing cat allergies one nap at a time – Photo by Manja Vitolic on Unsplash

But wait, there’s more! I was surprised by this, but it makes a lot of sense given my own experience. I was born with a cat allergy, but after deciding I wanted a cat anyway at a very young age (about five), I gradually stopped being allergic to cats. They are now almost the only thing I am not allergic to.

Allergies are a mystifying phenomenon. Exposure to something sometimes causes or worsens allergies and sometimes makes them go away. I found two studies that may shed a little light on how cat allergies work, however. Both suggest that exposure to cats early in life can prevent allergies later (8, 9). Like me! One study recruited children when they were 8-10 years old and checked in with them again twenty years later (8). They divided the subjects into groups based on whether they had a cat as a child (less than 18 years old), as an adult (more than 18), or both. Having a cat before adulthood had a protective effect against asthma and outdoor allergies by the time of testing (8). The other study focused on pet allergies specifically and determined that children with exposure to an indoor cat or dog within the first year of life were less likely to become sensitized to that same animal by the age of eighteen (9). New and soon-to-be parents, take note!

Don’t actually take parenting advice from me. I know nothing about children. Just cats. And in that regard, I soundly advise you to snuggle up with the nearest cat, as long as they are willing. After all, it’s good for your health. Stay safe out there, y’all.

Works Cited

  1. Somervill, J.W., et al. (2008). Physiological responses by college students to a dog and a cat: Implications for pet therapy. North American Journal of Psychology, 10(3), 519-528. https://psycnet.apa.org/record/2008-18014-007
  2. Washington State University. (2019, July 15). Stress reduction benefits from petting dogs, cats. ScienceDaily. https://www.sciencedaily.com/releases/2019/07/190715114302.htm
  3. von Muggenthaler, E. (2001). The felid purr: A healing mechanism? The Journal of the Acoustical Society of America, 110(5), 2666. DOI: 10.1121/1.4777098
  4. Klotter, J. (2002). Vibrational frequencies that heal. (Shorts). Townsend Letter for Doctors and Patients, 226, 28. link here
  5. Qureshi, A.I., et al (2009). Cat ownership and the risk of fatal cardiovascular diseases. Results from the second national health and nutrition Examination study mortality follow-up study. Journal of Vascular and Interventional Neurology, 2(1), 132–135. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3317329/
  6. Ogechi, I. (2016). Pet ownership and the risk of dying from cardiovascular disease among adults without major chronic medical conditions. High Blood Pressure and Cardiovascular Prevention, 23(3), 245–253. DOI: 10.1007/s40292-016-0156-1
  7. Headey, B. (1999). Health benefits and health cost savings due to pets: Preliminary estimates from an Australian national survey. Social Indicators Research, 47, 233–243. https://doi.org/10.1023/A:1006892908532
  8. de Meer, G., et al. (2004). Presence and timing of cat ownership by age 18 and the effect on atopy and asthma at age 28. Journal of Allergy and Clinical Immunology, 113(3), 433-438. DOI: 10.1016/j.jaci.2003.10.008
  9. Wegienka, G., et al. (2011). Lifetime dog and cat exposure and dog‐ and cat‐specific sensitization at age 18 years. Clinical & Experimental Allergy, 41(7), 979–986. DOI: 10.1111/j.1365-2222.2011.03747.x

Published March 28, 2020

Updated February 10, 2021

Science

Coat Color Genetics

mehshadoweye

Meredith Hemphill

mehshadoweye

Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Five tabby kittens
Colorful kittens – Photo from Pixabay

I majored in genetics as an undergraduate, so whenever I see a cat with unusual patterning or coloration, I can’t help but wonder what molecular wizardry made that possible. Cat fanciers have long wanted to unlock the mysteries of feline traits. While breeders began to puzzle out the patterns before DNA was determined to be the blueprint of heredity, there are still some mysteries to be solved. However, the more obvious traits have been mapped onto the feline genome, and there are even DNA tests for breeders or uncommonly curious pet owners who want to know what genes their cats carry. Today I want to cover the basics of coat color genetics, but I’ll start with a quick overview of genetics so no one gets lost. Feel free to skip it if you know you don’t need it.

Genetics: A Primer

DNA (deoxyribonucleic acid) is the molecule on which all the necessary information to build an organism is stored. Each unit of storage in the DNA is called a gene, and genes code for proteins. Proteins serve an incredibly wide variety of biological functions in the organism, including providing structure and metabolizing food into energy. There can be multiple different versions of a gene in the gene pool of a species. These different versions are called alleles.

Because an individual inherits half of their DNA from each of their parents, they have two copies of each gene. There are species for which this isn’t true, but it is for most vertebrates, including cats and humans. So each individual should have two copies of every gene, with a notable exception that we will get to later, but some alleles are dominant to others, so not every allele will be expressed. In the case of simple dominance, dominant alleles will be expressed if they are present. However, if the individual has inherited a recessive allele from both parents, they will express the recessive trait.

If you’re confused, I recommend looking up a more thorough overview of basic genetics before proceeding. There is much more to be said on the point, and I will do my best to explain as I go along, but it is only going to be more complicated from here. Now, let’s talk about what makes cats so very colorful!

Tom and the Monochromatic Fur Coat

Cats have two coat color pigments: eumelanin, which is black or brown, and pheomelanin, which is red or yellow. The primary coat color gene produces eumelanin. There are three alleles. The dominant allele, B, leads to black fur. The b allele is recessive to B and produces less pigment, leading to a brown coat, sometimes called “chocolate.” The b1 allele is recessive to both B and b, and it leads to a light brown or “cinnamon” coat.

The pheomelanin gene has a dominant allele, XO, that produces a red/orange coat color instead of or in addition to the color at the black/brown locus. The recessive allele, Xo, produces no reddish pigment. The pheomelanin gene is different in that it is located on the X-chromosome. In mammals, females have two X-chromosomes and males have one X and one Y, with some exceptions because biology is complicated.

So tom cats only have one gene for orange pigment, which they inherit from their mother. That is why toms are either ginger or black, but only very rarely both. But she-cats can have a XO and a Xo allele, causing them to have patches of both orange and black. This pattern is called tortoiseshell, or calico if they also have white patches. Tortoiseshell and calico toms can be born if they have two X-chromosomes and a Y or a similar chromosomal anomaly.

White cat with plush cow
White cat with odd eyes. Also a cow. – Photo by Samson Andreea on Pexels

50 Shades of White

White patches are due to the piebald spotting gene, where the recessive, s, allele codes for no white. If a cat has just one dominant allele, S, less than half of their fur will be white, and the white patches are often restricted to the feet, face, chest, and underside. If they have two dominant alleles, more than half of the cat will be white. It’s possible that they may even be completely white.

There are two other ways that a cat may be white, genetically speaking. The dominant white gene, as the name suggests, produces solid white cats with at least one dominant W allele. These cats are likely to be deaf, especially those with blue eyes and odd eyes. Those with odd eyes tend to be deaf in the ear on the same side as the blue eye. Rarely, white cats may be albino. There are two alleles that cause albinism, both recessive and both defective versions of the allele coding for the tyrosine enzyme. Cats with two c alleles are true albinos and have a translucent white pelt with pink eyes. Two ca alleles produce a white coat with pale blue eyes. There is no association of deafness with albino cats.

A Dilute Shade of Pale

The dilution gene is capable of modifying the appearance of other colors. The dominant allele produces the normal coloration. Two recessive alleles causes the pigment granules to clump in the hair shaft and leave large areas without pigment. The result is a lighter, or diluted, coloring. Black cats become grey, known as “blue” in the breeding world. Chocolate becomes lilac, cinnamon becomes fawn, and ginger, or “red,” becomes cream.

This covers the basics, although certain breeds can have unique alleles, such as the amber allele at the orange locus in Norwegian Forest Cats. I will cover the genetics of coat patterns another week. Until then, enjoy this picture of my gorgeous blue-cream calico.

Published February 20, 2020

Updated June 20, 2022

Science

Music for Cats

mehshadoweye

Meredith Hemphill

mehshadoweye

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Does your cat like to listen to music with you? Some pets do, but it’s more often the case that they seem simply to tolerate our tunes. Or not, if you have a cat that leaves the room when you put on your favorite song. Why don’t our furry friends enjoy music as much as most of us do? David Teie, a cellist, composer, and researcher, wondered if other animals would like music that was composed with their audio processing in mind. He partnered with Dr. Charles T. Snowdon at the Department of Psychology at the University of Wisconsin-Madison to test out his theory of species-specific music [1].

Teie and Snowdon aimed to compose music that would elicit positive emotions in cats, target frequency ranges suitable for feline ears, and make use of sounds natural to cat communication. Teie composed two songs for the study. They had an average pitch of 1.34 kHz, significantly higher than is typical of human music. Sounds within the cat vocal range of 55-200 Hz were a focal point, but frequencies related to howls and frustrated vocalizations were excluded. A large percentage of melodic sliding frequencies were included in the compositions, as cats use a lot of sliding frequencies in their vocalizations. One of the songs, “Cozmo’s Air,” was given a tempo of 1,380 bpm to resemble purring. “Rusty’s Ballad” had a tempo of 250 bpm, reminiscent of the suckling of kittens. To hear a sampling of Teie’s compositions for cats, play the video below.

The researchers paired each of Teie’s species-specific songs with a classical song chosen for its pleasing qualities for human listeners. 47 housecats were played 3 minutes of all four songs with a 3 minute rest period in between. Their behaviors during the music were observed and scored for “orient/approach” or “avoidant/fearful” actions. The time between the beginning of the song and onset of any resulting behavior, termed “latency,” was also measured. Very few fearful behaviors were seen, and there was no difference between cat or human music in the rate thereof. However, significantly more approach behaviors, such as purring or rubbing against the speakers, were observed while playing the cat music. There was also a significantly shorter latency period before the cats began to react, suggesting that the music geared for their ears caught their attention faster.

This research has a lot of possible applications. Teie and Snowdon suggest it may be used for calming cats with separation anxiety while their owners are away or for helping shelter cats to feel less stress. A study at Louisiana State University School of Veterinary Medicine using Teie’s cat-specific music found that it reduced stress during veterinary exams [2]. Personally, I listen to music just because it makes me happy. If this species-specific music brings cats joy, I say that is an end unto itself.

Tortoiseshell cat between speakers
All about that sliding frequency – Image by Anfesamo from Pixabay

Teie has since composed even more songs for cats. You can sample them for yourself–and your cat–at https://www.musicforcats.com/. He has CDs and digital downloads for sale, should your cat respond well and you’d like to buy full tracks to play for them.

Works Cited

  1. Snowdon, C.T., Teie, D., & Savage, M. (2015). Cats Prefer Species-Appropriate Music. Applied Animal Behaviour Science, 166, 106-111. https://doi.org/10.1016/j.applanim.2015.02.012
  2. Hampton, A., et al. (2019). Effects of music on behavior and physiological stress response of domestic cats in a veterinary clinic. Journal of Feline Medicine and Surgery, 22(2), 122-128. https://doi.org/10.1177/1098612X19828131

Published January 6th, 2019

Updated May 12th, 2023