The star coat pattern in foxes: what does it have to do with tameness?

Despite my previous voracious reading about tame foxes, as I settle in to my new lab I’m realizing how much I don’t know about them. For example, one of the most interesting things about the tame foxes is that although they were selected just for behavior (not running away from a human approach), they have physical changes as well, and those changes mimic physical changes between wolves and dogs: the appearance of white patches of coat color, floppy ears, and curly tails. I have learned that this is not an example of white patches related to tameness:

Platinum fox

That is a platinum fox, a color morph unrelated to the white coat markings that seemed to appear with tameness. The white coat markings come from the star gene. So what do we know about the star gene? What do those markings look like?

I started my hunt for information about the star gene in my own reference manager, since I knew I had read about it before. The only paper I had saved about it was from 1981 (!) but it was written by the mastermind of the farm fox project, Dmitri Belyaev, so it seemed like a good enough place to start.

Belyaev D.K. (1981). Inherited activation-inactivation of the star gene in foxes: Its bearing on the problem of domestication., Journal of Heredity, 74 (4) 267-274. URL: http://jhered.oxfordjournals.org/content/72/4/267.short

So back in 1981, when rock music was just starting to get really good, Belyaev was pondering the trickiness of the star gene. At that point, the tame fox project was only 20 years old. In 1969, the first white-spotted fox was born on the tame fox farm, with spots on his head and paws. Other foxes followed. The images from the paper show them looking like this (apologies for the poor image quality — it’s all I have to work with):

Fox kits heterozygous for star allele

This star pattern was not completely new. It had appeared on other fox farms, in foxes that were not selected for tameness. However, it was appearing much more often in foxes on this farm that were selected for tameness. In fact, the three families of foxes that were the most friendly to humans were showing this color pattern the most often. Unselected (not tame) foxes showed this star pattern 1.1% of the time, on multiple farms. (This includes foxes on the experimental farm which were from lines that were not selected for tameness.) Foxes in tame lines showed the pattern 3.7% of the time, or more than three times as often.

By the way, the fox kits shown above have only one copy of the star allele. Animals with both copies of this allele look much more like border collies:

But you can see how the non-white parts of their coats are a dark silver, unlike the platinum fox pictured at the top of this post.

Anyways, the question was: why were the tame foxes showing this pattern more often than conventional foxes? The pattern is particularly intriguing because it looks so much like the patterns we see in coats in domestic dogs, as well as in domestic horses and other domesticated animals. Was it possible that whatever mechanism was making these foxes more friendly to humans was also affecting their coat? The other explanation is just as likely but a lot less interesting: that when foxes were selected for tameness, the ones that were chosen just happened to have more copies of the star allele in their gene pool than average. Inbreeding would then cause this allele to show up more often.

Belyaev looked at family trees of foxes showing this pattern, trying to figure out if the gene for star pattern was recessive or dominant. The genealogy he found was somewhat perplexing. It didn’t follow the structure you'd expect for either a dominant or a recessive trait. The trait appeared to have variable penetrance, meaning that some animals with the star allele showed the star coat pattern, but some didn’t have star patterns, despite having the allele for it. This, of course, begs the question: if you have a group of animals, all of whom have the star allele, why do only some of them actually have the star coat pattern?

There are some possibilities:

• There may be a hormonal difference in the tame foxes which changes the effect of the star allele. In other words, the hormonal soup of a tame fox (less cortisol, less adrenaline) may affect coat color during development, so that those foxes are more likely to express the star allele if they have it. Conversely, the hormonal soup of a conventional fox (more cortisol, more adrenaline) may somehow suppress expression of the white spotting.
• The star allele has been around for a while, but perhaps it appeared in lower numbers in conventional foxes because it was somehow inactivated. Something about breeding for tameness may have activated the gene so that it was not “turned off” as often in tame foxes.

In 1981, no one knew which of these stories was more likely. This was before epigenetics was a hot topic, for one thing. But the nice part about reading historical papers like this one is that sometimes the answers to their questions exist in more recent literature. Which I am going to go hunt down now.

Fox colors

Tame fox kits

We often talk about the tame foxes as “silver foxes,” but in fact there are multiple color morphs in the tame population, not just silver. All of the foxes you’ll see here are the same species, Vulpes vulpes. The silver color morph was the color used for the first foxes which were selected for the creation of the tame population, but other morphs were brought in later.

Here is the silver morph, the color we are all most familiar with as being the color of a tame fox:

Tame silver foxes

My personal favorite fox color is Georgian white. The picture below is the one on my phone background.

Tame Georgian white fox

The ones that look so much like they have border collie markings, which are that lovely lighter silver color, are counterintuitively not called silver; they’re called platinum:

Tame platinum fox

And, of course, there’s the traditional red color, which somehow always surprises me the most to see on a tame animal:

Tame red fox

A rainbow of foxes!

Open access dog salivary cortisol data

I finally got around to sharing the data from my study of dog salivary cortisol levels on figshare. I have meant to do this for months. Particularly, I wanted to do it so that I could wear the cool “I’m a figsharer!” t-shirt that Mark Hahnel gave me at scio13. How embarrassing would it be to wear that shirt and have someone ask what you shared and have to admit that you still haven't actually shared anything? But I am a figsharer now. So if you want numbers, go check it out.

Oh, and in case you’re interested in the associated paper, that’s here (but, sadly, not open access):

Hekman, Jessica P., Alicia Z. Karas, and Nancy A. Dreschel. “Salivary cortisol concentrations and behavior in a population of healthy dogs hospitalized for elective procedures.” Applied Animal Behaviour Science (2012). http://dx.doi.org/10.1016/j.applanim.2012.08.007

Nice to meet you

Having gotten somewhat settled in my new program, I asked my boss how she might feel about my blogging under my real name. She allowed as how that would be just fine. Hi, I'm Jessica. It's nice to meet you.

Which brings me to the really exciting part, which is that I also get to tell you guys that I am privileged to be training in a genetics lab which studies Belyaev's tame foxes! No, really. Where better to be for someone obsessed with the mechanisms behind domestication? We don't have a colony of the foxes here, sadly, but my boss goes to Siberia a few times a year and brings back genetic samples as well as astoundingly cute videos. The lab itself is plastered with photos of foxes playing with things. And the science, obviously, is extremely cool.

I am very lucky to get to work in a lab which works directly with canids. Until very recently, that was nearly impossible to do; in fact, one of the reasons I initially decided to get a DVM instead of a PhD was that I could not find a lab at the time (2007) that would let me work with canids. But dogs are finally getting to be a hot research topic, which has turned out very well for me.

2013 Canine and Feline Genetics Conference

I was privileged to attend the 7th International Conference on Advances in Canine and Feline Genomics and Inherited Diseases this past week at the Broad Institute in Cambridge, Massachusetts. It wasn’t a large conference: about 150 dog and cat genetics researchers who get together every year and a half or so to catch each other up on what they’ve discovered recently, give each other suggestions about how to proceed or where to get good samples, and give their graduate students a chance to give some talks. I took notes on Twitter (#canfelgen) on my favorite talks (er, those of them that were not too technical; there were quite a few talks that I enjoyed hugely but that did not lend themselves to 140 character summaries). My apologies in advance if I got anything wrong; I was typing with my thumbs as fast as I could and may have made some mistakes.

Robert Wayne, Analysis of recent and ancient canine genomes suggest a new hypothesis for dog origins
Robert Wayne of UCLA talked about ancient canid genomes and “a new hypothesis for dog origins.” We are still not sure which gray wolf population was directly ancestral to modern dogs, and his work has shown that in fact no single population appears to fit the bill. Wayne believes that in addition to all the gene mixing between dog and wolves since domestication (which obviously muddies the picture), there was an ancient population of canids that gave rise to both dogs and wolves which we have not yet found samples from.

Wayne explained that ancient populations of wolves were much more diverse genetically than modern day populations, and we will really need to look to those ancient populations to solve the mystery of dog origins. About 10,000 years ago, populations of both wolves and dogs shrank dramatically in size, which explains why wolf populations are less diverse today than before that bottleneck. This was right around the time that domestication may have been happening, but we don’t know if the events are related.

So, based on this information, Wayne Lab embarked on a study of ancient canid DNA, comparing samples from dogs and wolves both from about 15,000-30,000 years ago. They found that the oldest dog populations were in Europe, not Asia. One interesting finding was in the black coat gene, which was relatively recently introduced from dogs into wolves and has swept through wolves. Apparently, being homozygous for black coat reduces fitness in wolves, but being heterozygous increases fitness. They don’t know why yet.

Wesley Warren, Genetic signatures of selection in the domestic cat lineage
Wesley Warren of the Washington University School of Medicine talked about using cats as models to study domestication. Comparing what we know about the behavior of cats to work in other species (dogs, horses, and chickens), he hypothesizes that cats aren’t actually undergoing significant domestication at all, because they are still very competent at living independently from humans and hunting their own prey. He talked about his work developing a SNP chip for cats, to aid in future genomic research in that species. A SNP chip is basically a library of known polymorphisms in the cat genome — single nucleotides that are known to differ between different individuals. Having all of these SNPs cataloged and available for use on a chip makes looking for correlations between these differences and things like behaviors or diseases much easier. At one point, his chip was used to discover the gene for curly coats in cats.

Warren talked about his recent work comparing the genomes of domesticated cats with their nearest wild relative. He found differences in RALY, a coat color gene. He found that cats have fewer receptors for smell than dogs do, but more for pheromones, and he wants to compare both olfactory and pheromone receptor genes in domesticated cats to big cats. He also talked about the 99Lives project, a project to get more cats sequenced (a theme which was returned to later in the conference).

Anna Kukekova, Simple behavioral pattern: is it simple?
Anna Kukekova of the University of Illinois talked about her work with tame foxes (if you don’t know about the Russian farm fox project, check out the excellent summary at the Thoughtful Animal). Kukekova opened by demonstrating the difference between the lines of foxes selected for tameness and the foxes selected for aggression with video in which a researcher performed a behavioral test on one fox from each line: first standing by a fox’s cage, then opening the door and reaching for the fox, then trying to pet the fox. The videos, shown side by side, were dramatically different: on the left, a clearly wild animal, both cowering from and menacing the human who stood near it. On the right, an animal reacting to human presence just as a dog in a shelter might, almost in a spasm of enthusiasm, wagging its tail, soliciting affection, rolling over to let the human pet its belly. Kukekova talked about analyzing the differences in behavior statistically, and how some of the most important behaviors they found for consistent differentiation between the populations were pricking ears forward, wagging tails, and approaching humans.

Kukekova investigated foxes which were second-generation crosses between tame and aggressive lines. The tame behavior was highly heritable, which was already known. Animals with heritage from both lines usually showed intermediate behavior, on the spectrum between tameness and aggression. What was interesting was that some of the crossed animals showed what she called “switching” behavior: the animals showed tame behavior at some points in the test, and aggressive behavior at others. For example, some of these animals were aggressive to humans who stood at their cage doors, but friendly when the door was opened. Others were friendly when the door was closed, but aggressive once it was opened.

Tara Baxter, Genomic approaches to identify putative canine behavior-associated genes
Tara Baxter of Cornell talked about her method of trying to track down some genes that are associated with different behaviors in dogs. This is a tough problem, as behaviors are usually influenced by multiple genes as well as by the environment, so tracking down a gene that influences aggression (for example) is a lot harder than tracking down a gene that is all by itself responsible for a disease. Baxter reviewed test results from owners who filled out a CBARQ (behavioral survey) about their dogs; she had access to a database of 19,000 surveys, so an impressive sample size. Using these tests, she averaged behaviors for each breed, getting a score of how likely animals of a particular breed were to display a particular behavior (for example, “begging”). Then she did an association study, using a canine SNP chip similar to the feline one discussed above. She used the chip to compare the SNPs found in individual dogs from various breeds, and looked for correlations between the average breed behaviors and the SNPs that she found in individuals of those breeds.

She had some interesting results which will benefit from more study. For example, for the behavior of urinating while left alone, she found an association in an area which is related to behavioral disorders in humans. Finding this association in an area which seems to affect behavior suggested to her that she might be on the right track, though of course a lot more work will need to be done. She mentioned some other interesting associations that she found as well. She also, of course, found associations that appear spurious, such as the association between a gene for long hair and chasing behavior. One amusing association she found was a relationship between the gene for short legs, such as you might see in a corgi, and a fear of stairs! She commented that sometimes physical traits explain behavior.

...And that is my smattering of summaries from the conference. Here’s hoping that I will manage to attend the next one, in eighteen months, in the other Cambridge — the one in the UK!

Guessing at the mechanisms of dog aggression

I've been thinking a lot lately about how dog aggression works, since the recent dog fighting bust (second largest in history). Fighting dogs are bred for willingness to attack other dogs, but for docility with humans. You don’t want your fighting dog to turn on you in the training yard or in the ring! Willingness to attack another dog, and to continue to attack when the other dog retaliates, is called “gameness.” Despite intense selection on the part of the dog fighters, the dogs show a lot of variation in levels of gameness: some dogs are very game and some are less so, even with training. But it does seem to be true that gameness is heritable, something you can breed for.

So how do you get aggression which is so specific? And what are the fighting dog breeders actually selecting for? What’s different in the DNA of a game dog and a not-game dog? We don’t have any real idea. Recently I came up with one possibility (too new even to be called a theory). It opens more questions than answers, but here’s the story.

There is a well-studied phenomenon in rats and mice related to the position of the fetuses in the uterus. (I know, uterine position is probably not related to genetics, but bear with me for a minute.)  If a female fetus is surrounded by two males, one on each side, she gets more than her usual dose of testosterone in the uterus. Because testosterone helps the developing fetus know what sex to develop into, this extra testosterone makes her develop some masculine characteristics which will stay with her throughout life: she will be what is referred to as a masculinized female. Among other things, her behavior will be affected. Her play style will change to a more rough and tumble style. And she will be more aggressive towards others of her species.

This phenomenon has been demonstrated in multiple species, including guinea pigs, rabbits, and marmots. It is suspected to be in effect in dogs as well: although there are no published papers reporting on it in dogs (at least none that I could find — please let me know if I’m wrong!) I have heard it discussed at dog training seminars as a possibility. And given the range of species it affects and the similarity of effects of reproductive hormones on development across species, it seems really likely to affect dogs.

The big question is: how could this be a genetic phenomenon? The genders of your neighbors in the uterus are random, right? Well, not completely: one of the differences between masculinized and non-masculinized females is that masculinized females have more male offspring. Really. We don't know how that works, though there are some theories about why it may be a useful adaptation to some environments.

Moreover, testosterone doesn't just come from other fetuses. It comes from the mother as well. Some amount of testosterone is normal in development. What if what dog fighters are breeding for, without knowing it, is mothers who produce more testosterone when they are pregnant? Or maybe fetuses which are worse at transforming testosterone into estrogen (as fetuses like to do)? Or fetuses which are more sensitive to testosterone (maybe have more numerous or more sensitive testosterone receptors)?

These questions lead to even more questions, of course, which is why I haven’t even called these ideas a theory yet. Do the more aggressive masculinized female rodents show more aggression to their own species than to humans (which is my initial question about the fighting dogs)? Do male rodents with more males beside them in the uterus show increased levels of aggression? Do we know anything at all about different levels of testosterone released by the dam, not just by uterine neighbors?

There is a lot known about intrauterine position. It is really well studied, partly because it might help us understand the effects of reproductive hormones on fetuses in general, such as possible effects of artificial hormones which are unintentionally introduced into our diets, like BPA. So as I continue to read about it, I hope I’ll start to figure out if this is an idea with legs or just a passing fancy. In the interests of keeping this post readable, I haven’t written about all the interesting facets that I’ve encountered in this phenomenon, so feel free to ask questions. And there are certainly holes in the idea beyond the ones I mentioned, so feel free to point those out, too!

Edited to add: I messed up in suggesting that intra-uterine position might affect dogs the way it has been shown to affect rats, humans, and cattle. Dog placentas are fundamentally different from rat and human placentas, and also different from cow placentas (which form a third category). In short, it would be pretty unlikely for two fetuses to share hormones in-utero in a dog the way they can in rats, humans, and cows. So while I still think it's an interesting idea that a dog fetus could be exposed to different amounts of testosterone in-utero (probably due to processing of hormones by the placenta) and that this could affect its adult behavior, I want to emphasize that it is actually not likely that these hormones could be from other fetuses in a dog. The hormones would be from some difference in the mother, not from a chance alignment of the offspring. So in summary: if your bitch gives birth to one female and two males, that's not a reason to worry about masculinization and temperament in the female.

References

• Ryan B.C. (2002). Intrauterine position effects, Neuroscience and Behavioral Reviews, 26 (6) 665-678. PMID: 12479841
• Monclus R., Cook T. & Blumstein D.T. (2012). Masculinized female yellow-bellied marmots initiate more social interactions, Biology Letters, 8 (2) 208-210. DOI: 10.1098/rsbl.2011.0754
• Hotchkiss A.K., Lambright C.S., Ostby J.S., Parks-Saldutti L., Vandenbergh J.G. & Gray L.E. (2006). Prenatal Testosterone Exposure Permanently Masculinizes Anogenital Distance, Nipple Development, and Reproductive Tract Morphology in Female Sprague-Dawley Rats, Toxicological Sciences, 96 (2) 335-345. DOI: 10.1093/toxsci/kfm002
• Bánszegi O., Altbäcker V. & Bilkó Á. (2009). Intrauterine position influences anatomy and behavior in domestic rabbits, Physiology & Behavior, 98 (3) 258-262. DOI: 10.1016/j.physbeh.2009.05.016
• Correa L.A., Frugone M.J. & Soto-Gamboa M. (2013). Social dominance and behavioral consequences of intrauterine position in female groups of the social rodent Octodon degus., Physiology & behavior, PMID: 23769692

State of the Zombieverse

I finished my veterinary shelter medicine internship at the end of June. It was a crazy year. I learned so much, and I am so glad that I did it. I do feel that I did what I set out to do: learned a lot about the inner workings of animal shelters and made some very valuable contacts in the field.

I left the South and moved to the Midwest, where this fall I have started a PhD program. I'm working with a lab that focuses on the genetics of canid behavior and domestication (I know, right?). I'm so lucky that a place like this even exists. Sometimes I am frustrated that I found these interests in dog behavior and domestication so late in life, but then I remember that a few years ago, shelter medicine internships didn't exist, and there were no PhD programs studying canid behavior.

My life is very different right now compared to a few months ago. Instead of spending my days at chaotic shelters, I spend them alternating between lab work (so far, running PCRs) and lectures. Instead of having a highly organized schedule, everything is up to me: how many classes to take, how much to work in the lab, even what projects to work on in the lab.

So how will this blog's content change? I'm not sure yet. At a guess, I will write less about shelters, and more about the science behind behavior. I do hope to stay connected to the sheltering world in my Copious Free Time, though, so I may still write about that stuff. I'll see how my career here develops, and of course I am always open to requests from you guys!