Coat colour and behaviour

October 30, 2008, By Jean Donaldson, ARTICLE, BEHAVIOUR

The study of links between coat colour and behaviour has a long and interesting history. Those in volved in the day-to-day husbandry of animals – farmers, those charged with the care of laboratory animals, and pet owners, for instance – have noticed uncanny dif ferences in temperament that seem to correlate with the colour of an animal’s coat. To list just a few examples from the pet lore I’ve heard over the years:

• Chocolate Labrador Retrievers are more juiced up and active than yellows or blacks.
• Orange-and-white cats are laid-back and friendly; tortoiseshell cats are the opposite (“naughty torties”).
• Black-and-tan dogs are inclined to guard resources.
• Longhaired hamsters are more mellow.

No doubt you’ve heard such tales from within your own breed. Or there may be a strong sentiment against coat-colour mattering. In Chows, for example, the party line is that colour makes no difference.

Some experienced people are naturally skeptical of these claims while some with equal experience would bet money there’s something to them. So what does science have to say about all this? Amazingly, even be fore the structure of DNA was discovered and published by Watson and Crick in 1953, there were a couple of seminal experiments done on rats.

A brief history
In 1942, C.E. Keeler put agouti rats (wild type colour – black-tipped hairs with orange-y banding) and black rats through a temperament test with items such as being picked up, and having a little bristle brush run over their noses. He cleverly controlled for their ini ti ally dif ferent strains by breeding them together over two generations and then comparing the third generation offspring. At this point, the rats from both colour groups shared many more genes, with the exception of those coding for colour. He also raised them identically, without handling them until they were weaned.

The agouti rats were not only more cautious and more likely to bite and squeal when picked up, they did so more intensely. Agouti rats delivered rapid-fire multiple bites and loud squeals, whereas what ended up being scored as a “bite” by a black rat was usually one soft nip. As a dog person, I find this fascinating, as there is significant trainer lore regarding not only how likely a breed of dog is to bite but the bite style of that breed: Hard or soft, latch-and-shake or bite-release, multiple bites or single bite. This research seems to sug gest that there may be a genetic component to how exactly a strain (re: breed) bites.

Fast-forward to 1987, when Cottle and Price who, with a more sophisticated knowledge of genetics and more-precise quantification of results, corroborate this same finding. Ten years later, the same is found to be true in deermice – agouties are more skittish than black! So, it looks like there’s something to this, as studies on everything from minks and gerbils to Holstein cows suggest links between coat colour and behaviour.

How can it do that?
How could the system that produces the colour of hairs possibly influence behaviour, you may very well ask? In the case of agouti, it’s partly understood. Pigment is produced by melanocytes located in the deep est layer of skin. They are urged into higher gear by the presence of melanocyte stimulating hormone (MSH). MSH in full gear produces black pigment, resulting in a black rat. The agouti protein puts the brakes on MSH produc tion, and when MSH isn’t present, the same melano cyte produces a reddish-orange pigment. These two pro cesses interacting result in the agouti colouration.

 

 

 

Here’s the amazing part: MSH is also found in the brain, where it modulates the effect of neurotransmitters, notably the catecholamine group (including the glamour neurotransmitter, serotonin), which have been strongly implicated in mood, anxiety and aggression. The agouti-protein MSH brakes are doing their thing in the nervous system! Agouti rats have also been found to have larger adrenal glands, another possible means for a colour/behaviour connection.

 

Another coat-colour-behaviour-connection mechanism well-known to those familiar with the Russian Silver Fox experiments that have been ongoing since the ’50s is that of regional de-pigmentation, or piebalding – the presence of white on the coat. As foxes were selected for increasing tameness generation by generation, white spots began appearing on the animals’ coats far more often than in normal controls.

Lydia Trut, one of the fox researchers, replicated this work in rats. Using strictly tameness as criteria, after generations, three-quarters of the rats had white-patched coats. In neither case was there any attempt to breed for these white patches.

What about dogs?
In 1996, James Serpell and Anthony Podberscek published a study on English Cocker Spaniels in the journal Applied Animal Behaviour Science. They obtained reports from the owners of 1,109 dogs on their dogs’ ag gression in 13 different circumstances, including ag­gression to other dogs, to the owner, when handled, and to strangers. They then looked for correlations be tween the kinds of aggression and the dogs’ sex, reproductive status and coat colour.

There were no surprises when it came to sex: males were more aggressive on four measures, and females were more aggressive to housemate dogs. When it came to coat colour, solid Cockers were more aggressive than parti-colours, and among the solids, the reds were more aggressive than the blacks in 10 of the 13 contexts .

Then in 2006, a new study looked at this same question but in a different way. Rather than collecting owner reports about aggression, Joaquin Perez-Guisado conducted temperament tests on full- and half-sibling En glish Cocker puppies at age seven weeks. The tests were the typical puppy-testing items, such as holding the puppy off the floor, a follow-me test and how the puppy behaved if held down.

These tests purport to “measure” dominance, which is a problematic construct, as is the dismal ability of such tests to predict adult behaviour in routine situations. Nevertheless, it is valid to compare puppy to puppy, and see if coat colour predicts differences on scores within the tests.

Perez-Guisado’s findings were similar to those of Serpell and Podberscek. Red En glish Cockers were the most difficult to handle (even attempting to bite), followed by blacks. Parti-colours were more docile and “seemed to enjoy” the handling.

It is important to note that this finding could use more replication and if true, does not necessarily have any bearing on American Cocker Spaniels, let alone other breeds. Every researcher takes pains to point out the colossal importance of environment in the ultimate phenotype that is behaviour.

As our understanding of developmental pathways increases, there will be more research conducted, so make your bets now on what ef fects there are in your favourite breeds!

By Jean Donaldson
Canadian Jean Donaldson is the founder of the San Francisco SPCA Academy for Dog Trainers. Her books include The Culture Clash, Dogs Are From Neptune and MINE! A Guide to Resource Guarding in Dogs.