The possible significance of dietary differences between dog and wolf

Everyone knows that the domestic dog (Canis familiaris), like its close relative the wolf (Canis lupus), is a carnivore. However, how many realise that the capacity for omnivory in the dog is so great that it throws doubt on the assumption that the wolf is its sole ancestor?

In https://www.inaturalist.org/journal/milewski/56803-an-extinct-canid-hiding-in-plain-sight-in-the-domestic-dog#, I pointed out that the wild-type colouration so recurrent and persistent in the domestic dog has no precedent in the wolf.

And so, I imagined an additional (unnamed) ancestral species, which became extinct prehistorically, and may have been ecologically similar to jackals rather than the wolf.

This speculation seems to be supported by differences in diet.

The wolf is unusually specialised for carnivory among canids - most other species of which can be described as omnivores with a preference for vertebrate flesh.

Jackals, foxes, and other canids depend partly on carbohydrate-rich foods such as fleshy fruits, which can be seasonal staples in some cases (e.g. see https://en.wikipedia.org/wiki/Solanum_lycocarpum and https://sciencing.com/do-gray-foxes-eat-8497562.html and https://www.smithsonianmag.com/smart-news/urban-coyotes-eat-lot-garbageand-cats-180974461/ and https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1380&context=hwi and https://threatenedtaxa.org/index.php/JoTT/article/view/2109/3271).

The only canids that hardly ever resort to carbohydrate-rich foods are those most specialised for predation in their respective regions: the wolf over most of the Northern Hemisphere, the dhole in Asia (https://en.wikipedia.org/wiki/Dhole), the bush dog in South America (https://en.wikipedia.org/wiki/Bush_dog), and the African hunting dog (https://en.wikipedia.org/wiki/African_wild_dog).

Dhole, bush dog and African hunting dog all have more specialised carnassial teeth than is typical in their family. The wolf retains flat surfaces on its molars, but these are used for crushing bones, not grinding plant matter.

Unlike the wolf, the domestic dog can eat carbohydrate-rich foods as staples (e.g. https://www.akc.org/expert-advice/nutrition/do-dogs-need-meat-in-their-diets/ and https://www.peta.org/issues/animal-companion-issues/animal-companion-factsheets/meatless-meals-dogs-cats/ and https://en.wikipedia.org/wiki/Potcake_dog).

Green grass is a normal, if minor, part of the diet of the dog (https://www.researchgate.net/publication/228739099_Grass_eating_patterns_in_the_domestic_dog_Canis_familiaris and https://www.une.edu.au/__data/assets/pdf_file/0019/32446/bjone-brown-price-grass-eating20patterns-raan-2007.pdf).

Furthermore, it is possible that plant-based diets (consisting mainly of starchy meal plus bones and cartilage) are sufficient even for growing juveniles.

Partly for this reason, the domestic dog remains, in several countries, a species of 'grain-fed' livestock, butchered for human consumption (https://www.onegreenplanet.org/animalsandnature/how-south-korea-manages-to-farm-dogs-for-consumption-will-shock-you/ and https://en.wikipedia.org/wiki/Dog_meat and https://www.usatoday.com/in-depth/news/2019/02/25/south-koreans-eat-more-than-2-million-dogs-every-year-but-thats-changing/2930025002/ and https://awionline.org/dogmeat).

It seems significant that the raising of the domestic dog as consumable livestock needs no particular breed; and types ranging from small- to large-bodied are utilised (http://messybeast.com/history/edible-dogs.htm and https://web.archive.org/web/20160418004308/http://greenconsensus.com/education/food/materials/02_due_september19/podberscek_Good%20to%20Pet%20and%20Eat.pdf and https://en.wikipedia.org/wiki/Xoloitzcuintle and https://www.science.org/news/2011/05/earliest-american-dogs-may-have-been-dinner and http://traditionalanimalfoods.org/mammals/domesticated/ and https://www.jstor.org/stable/40914418).

Plant-based foods tend to be cheaper than animal-based foods. This is because of basic thermodynamic principles in the 'energy pyramid' (https://en.wikipedia.org/wiki/Trophic_level). Bones are also affordable. It would hardly be economical to treat the dog as livestock were it not for the capacity of this species to grow with minimal amounts of the relatively expensive, animal-based foods in its diet.

If the 'missing ancestor' of the domestic dog was ecologically similar to modern jackals, its capacity to exploit plant-based food-scraps would have suited it to human economies. Such a capacity seems to have been increased only slightly by domestication.

Does this alternative ancestry not seem more plausible than the assumption that selective breeding of the wolf for docility and obedience happened also - inadvertently - to convert the carnivorous wild species to omnivory in domestication?

Posted on September 29, 2021 04:07 AM by milewski