Dogs as an Evolved Form of Opportunistic Carnivore

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Edward the Bull Terrier

Courtenay Morgan’s Edward, the Bull Terrier

Discussing the care and feeding of dogs has become highly controversial in recent years, prompted largely by the growing popularity of raw feeding as well as the increasing attention kibble manufacturers have given to grain free and limited ingredient diets. This article will not strictly address the validity of any of these feeding methods, instead in future articles I hope to address some misconceptions and provide some clarity in aiding one to make informed decisions about the care of their pets.  The purpose of this article will be to address the basic anatomy of modern dogs and some adaptations they gained over their wolf ancestors during the process of domestication.

Canis lupus skull

By N. N. Kondakov, via Wikimedia Commons

Before I go any further into discussing care of dogs, it’s important that I discuss their ancestor, the wolf.  Wolves are classified as carnivores and their anatomy supports this – with sharp teeth, jaws that only move vertically, and saliva that does not contain amylase, the wolf’s mouth is designed to be efficient at shredding through flesh and swallowing large chunks of meat.  Any carbohydrates consumed by a wolf may see some digestion thanks to the production of amylase by the pancreas, however the short digestive tract of the wolf further limits its capability to efficiently breakdown grains.  There is some evidence that in the wild wolves may consume some grains during lean times, and there will always be debate over whether wolves consume the stomach contents of their prey.  Our present knowledge of a wolf’s digestive process suggests they would in fact benefit from such practices.  It is because of a wolf’s ability to take advantage of this limited capability to digest starches that many people classify a wolf as an opportunistic carnivore, although a more proper term would be facultative carnivore.

facultative

having the capacity to live under more than one specific set of environmental conditions, as a plant that can lead either a parasitic or a nonparasitic life or a bacterium that can live with or without air (opposed to obligate).

As an opportunistic carnivore, the argument can be made that a very important step in the creation of the domestic dog was the natural selection over time of wolves that were more capable of digesting starches.  The relationship of modern dogs and modern man is one of mutual benefit, with both having developed greatly during the Agricultural Revolution.  Certainly, the wolves more capable of thriving on the castoffs and waste products of human communities would be at an advantage.  A recent study, published in the journal Nature, The genomic signature of dog domestication reveals adaptation to a starch-rich diet, identified dogs as having between 4 and 30 copies of the gene that is responsible for amylase production, while wolves only have 2 copies.  This results in the gene being 28 times more active in dogs, which leads to dogs possibly having five times the effectiveness at digesting starches compared to wolves.  The same study also identifies that dogs produce a type of maltase that differs from that produced by wolves, sharing similarities with omnivores and herbivores.  As such, the study concludes that, “novel adaptations allowing the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in the early domestication of dogs.”

Our results show that adaptations that allowed the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in early dog domestication…The results presented here demonstrate a striking case of parallel evolution whereby the benefits of coping with an increasingly starch-rich diet during the agricultural revolution caused similar adaptive responses in dog and human.

Aussie

Photo credit: Courtney Hurley

So then who is right-  the people claiming that dogs are wolves and should eat a species appropriate diet similar to wild wolves, or the people claiming that dogs are so far removed from the wild that there is no sense in making the comparison? Hopefully if you’ve read up to this point, you can understand my perspective – both points are valid and in fact complimentary. Understanding and appreciating the anatomy of a dog goes a long way towards guiding the decision making process towards providing foods that are appropriate and enriching for the dog. However, to spurn modern scientific understanding of canine nutrition would be foolish.  What generations of living around wolves and selectively breeding of dogs has shown us is that both wolves and dogs are incredibly flexible in what they can adapt to, but scientific studies are what show us the nutritional requirements that dogs truly need in order to thrive.

It’s important to note that anatomy does not always dictate dietary needs.  One only needs to look at human beings, with our wide variety of dietary intolerances appearing in various individuals that are anatomically similar.  Just like certain humans, true omnivores adapted to eat an extreme wide variety of foods, may not be able to properly digest foods containing lactose, gluten, or even red meat; so too are dogs capable of displaying variations in what they are capable of thriving on and it is important that we cater to the specific needs of those animals that are in our care. Recent studies have shown the needs of sled dogs, racing greyhounds, and dogs active in sports such as agility vary greatly.  In my next article, I will discuss the specific nutritional requirements of dogs involved in each of these activities.

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