The Evolutionary Argument against Wildlife Pets

What do sun bears, slow lorises, bobcats, and pythons all have in common?

They are all part of the global trade of wildlife for use as pets. And these are only a few of the species kept as pets.  There are no shortage of pieces describing the ecological, conservation, and/or ethical impacts of having wildlife as pets.  On the ecological side, wildlife pet trade can introduce non-native species (bird example here) into new environments, where these species may out compete native species.  The most prominent example being pythons in the Everglades ecosystem.  Pythons have been implicated in local extinction of multiple prey species, thereby altering foodwebs and species interactions.  The trade of reptiles and amphibians have increased conservation concerns related to the introduction of disease into new environments.  If native species lack immunity, we may observe population declines.  Last month the US Fish and Wildlife Service prohibited the import of 201 salamander species to limit the threat of salamander chytrid introduction into the USA (which we covered previously).  Another conservation issue is that some species kept as pets are threatened or endangered with extinction.  They really should be in the wild trying to have more babies.  Finally, there are a number of ethical issues with wild pets including the removal of their teeth and/or claws, use of small cages which limit movement, lack of enrichment, and poor diet.

The ecological, conservation, and ethical issues are enough for most people to not want to keep wildlife in their home; however, evolution makes the compelling argument that wild animals just don’t have the brains to be pets.

The intelligent and social African Grey Parrot (Psittacus erithacus) as a pet.

The Evolutionary Argument against Wildlife Pets
The animals we keep as pets were domesticated from wild relatives; for example, dogs were domesticated from a wolf ancestor. Domestication involves a suite of traits commonly referred to as the “domestication syndrome.”  The most prominent trait is increased docility and tameness and a lowered fear response.  These behavioral traits are why humans and our companion animals can live in such close proximity.  An evolutionary change this big, slowly increasing the number of individuals in a population with a particular trait (i.e. tameness), would take many generations. Humans and domesticates did this naturally 1000s of years ago (maybe starting about 27,000 years ago for dogs); more recently experimental evolution studies on foxes and rats have reproduced these results.  In these studies, researchers score animals on behavioral traits then breed the animals with the highest scores for tameness.  After a few generations, most animals in the population are tamer and less afraid of humans than the founding population.

We intuitively know domesticated animals are tame; it’s why rabbits in the wild run away from people so not to be eaten, where my pet rabbit, Sabrina, and I could watch TV and eat cereal together (she was fond of Kix). The evolutionary change which selected for tameness results in other behavioral changes including lower anxiety and fear of humans.  These behavioral traits have been linked to genomic changes, mainly decreased allelic diversity in genes associated with behaviors including genes associated with autism spectrum disorders in humans.  Additionally, genes may be down-regulated, this has been observed with the result of lower levels of stress hormones in domestics. All of this is to say that there have been major genomic changes with resultant neurological phenotypes which make domesticated animals nice to have in our homes.  That wild animals do not have these neurological changes makes them really frightening to have as pets.  One could see how higher fear of people, higher stress, greater behavioral variation, and more hormones leading to fight-or-flight response would make their behavior less predictable compared to domesticated animals.

The domestication syndrome is not limited to behavior. The physical characteristics include: depigmentation (particularly white or brown patches), floppy ears, curly tails, shorter muzzles than wild relatives, smaller teeth, smaller brain capacity, longer juvenile behavior period, and more frequent reproductive cycles.  I think the shortening of muzzles and jaws (which can result in less bite force), and smaller teeth are relevant to thinking about wildlife pets.  Domestic animals may use these traits less, particularly as being given food versus hunting is part of the deal between humans and their commensals.  Wild animals still have their full strength jaws and full size canines and incisors because they need them to hunt and eat.

The perception of luxury or personal satisfaction that comes with “taming” a wild animal are arguments for wild pets simply lost on me. Personally, I associate “pet” with “cuddles,” and no part of me wants to be within cuddle range of an animal with a strong mouth and behavioral inclination to go for the jugular, yikes!



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