Dogs versus Wolves

by Dr. Hillary Noyes

wolf

Grain-free! Meat first! Raw! Primal! Biologically appropriate!

How many times have you heard that our pet domestic dogs should be fed like their wolf ancestors? How many glittering pet food packages feature a regal wild carnivore on the bag to imply the same?

Is it true? What’s best? What does the science say?

The science says that there are some fundamental differences between wolves and their subspecies descendants, domestic dogs:

Genetics

While yes, dogs most likely originated from wild wolves, they have been domesticated for an estimated 35,000 years. In that time, they have been selected for a variety of traits that symbiotically benefitted both the canids (better access to easy food, protection) and the humans (protection, vermin-eradication, companionship). Over the past few hundred years, we have escalated that selective breeding into a variety of diverse breeds with relatively closed genetic populations, which increases the rate of genetic drift and change both between the breeds and from their original ancestors.

Because the full genomes of both the wolf and the domestic dog have been decoded, researchers were able to compare the two. They found that major differences exist in two key areas: brain development/ behavioral traits (we certainly wouldn’t want a wild wolf roaming through our house, but many of us allow our dogs to sleep in our beds!) and digestive traits, specifically the ability to digest starches. This increased ability to digest starches mirrors the evolution of humans to do the same thing, further solidifying the co-evolutionary link and similarity in lifestyle between omnivorous humans and dogs.  

Biology

Both wolves and dogs belong to the taxonomic Order Carnivora, which often gets confused with being carnivorous. While these animals all share a dental structure that originally evolved for shearing meat, most of the species in Carnivora are now omnivores (skunks, raccoons, bears, etc.) and a few are completely or almost completely herbivorous (giant panda, binturong).

Obligate carnivores are animals that require meat in their diet, because they can only obtain certain essential nutrients that way. These mammals include wild and domestic cats. Felids require dietary taurine, an amino acid necessary for heart and eye health. Dogs do not. Strict carnivores also require pre-formed Vitamin A in their diet, while omnivores like dogs and humans can form Vitamin A from beta-carotene. Other essential nutrients of carnivores that dogs do not need directly from their diet include arachidonic acid (a fatty acid) and niacin (a B Vitamin).

Lifespan

Possibly the most-overlooked, but potentially most important, difference between wild wolves and our beloved pet dogs, is their expected lifespan. Most people are surprised to hear that the average lifespan of a wild wolf is only 6-8 years. Virtually all people want and expect their pet dogs to live much longer than that. So how do we manage this significant difference in lifespan? Much of it boils down to the kidneys and protein. Animals are born with all of the nephrons (the functional units in the kidneys that filter the blood) they are ever going to have. No new nephrons are made during an animal’s life, so if they get damaged, the kidney loses that filtering function forever. Chronic kidney disease is a leading cause of death in older dogs and cats, often in the top two or three causes each year.

Protein is often at the fulcrum of the argument about the diet of wolves vs dogs. Proteins are large molecules made up of amino acid building blocks. When eaten, these amino acids get separated and reconfigured to build new proteins the animal needs at that moment (muscle tissue, ligaments, hormone molecules, antibodies, etc.). Protein is very important, but unlike excess fat or carbohydrate calories, which can be stored in the body for later use, if an animal eats more protein than it needs, that protein does not get stored in the body. After the protein is metabolized by the liver, the excess gets sent to the kidneys to be excreted. Most of our domestic dogs are not doing nearly as much activity as their wild counterparts and thus aren’t building as much muscle tissue and don’t need as much protein. Excess protein thus passes through those nephrons, putting more stress on the non-renewable resource of their kidneys. In fact, reduction in protein intake has been shown to prevent pathological kidney aging in laboratory animals, and also to postpone end-stage renal failure in dogs, cats and possibly humans.

Why is this a concern for our domestic pets but not their wild counterparts? Wild wolves simply do not live long enough to encounter the problem of aging kidneys. They often die earlier of starvation, trauma, or disease. Wolves in captivity at sanctuaries and zoos can live longer, up to 13 years or so, and interestingly many of these animals are fed a diet significantly comprised of dry kibble dog food!

Nature vs Nurture

The evidence from multiple disciplines of science, combined with our desire to have our pets in our lives for as long as possible, all clearly point toward differentiating their diet from that of wild wolves. Domestic dogs have evolved to eat and live alongside humans for millennia. The very things that wolves die of are things we routinely protect our pets from – we vaccinate to prevent contagious disease, we give them protected sleeping quarters away from the elements and other predators, we treat their wounds and broken bones if needed, we give them medicine to prevent parasites. The natural life of a wild animal is very difficult in many respects, and their diet may not even be optimal for them. They often encounter long periods of no available food, or what they do find is already dead, old or rotten. Those of us unlucky enough to live with dogs who choose to dine on found excrement (or their own!), trash, underwear or other unsavories know that their “natural” menu predilections are not always the wisest or healthiest! Domestic dogs can thrive on a variety of food sources, and for a long, healthy life, should be fed a balanced omnivorous diet.  

 

Resources

  1. Corman B. Normal and pathological renal aging in animals. Presse Med. 1992 Jul 22;21(26):1238-45
  2. Axelsson E, Ratnakumar A, et al. The genomic signature of dog domestication reveals adaptation to a starch-rich diet. Nature 2013 Mar 21;  495: 360-364.
  3. Anderson S. Effects of aging on the renal glomerulus. Am J Med 1986 Mar; 80(3): 435-442.
  4. Eyre S, Attman P, et al. Positive effects of protein restriction in patients with chronic kidney disease. J Ren Nutr. 2008 May;18(3):269-80. doi: 10.1053/j.jrn.2007.11.013.
  5. http://wolfsanctuary.co/faqs/
  6. https://nationalzoo.si.edu/animals/gray-wolf

 

HillaryDr. Hillary Noyes graduated from Michigan State University College of Veterinary Medicine where she participated in research on animal behavior and welfare. She then completed a small animal medicine and surgery internship at VCA Emergency Animal Hospital and Referral Center in San Diego, CA. Dr. Noyes practiced small animal general medicine before joining Hill’s Pet Nutrition as a Professional Consulting Veterinarian. She has served on the AVMA Human-Animal Bond Committee and is passionate about animal rescue.