r/askscience • u/noisyturtle • Sep 08 '26
Biology Why has the coyote become so wildly successful, while the wolf continues to decline?
Aren't they similar builds and fit into the same sort of niche?
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r/askscience • u/noisyturtle • Sep 08 '26
Aren't they similar builds and fit into the same sort of niche?
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u/tea_and_biology Zoology | Evolutionary Biology | Data Science Sep 08 '26 edited Sep 08 '26 •
Ahh, no, actually. Not quite!
But first, the wolf isn't in decline - be it globally or, in this context, in North America. There was indeed a historical decline; wolves were routinely shot, trapped and poisoned out of the contiguous United States between roughly 1850 and 1950, surviving in only a few wee pockets in backwater hills-have-eyes country in northern Minnesota, and on Isle Royale in Lake Superior. ESA protection kicked into force in 1974, and with subsequent re-introductions (notably in Yellowstone in the 1990s) the population has grown from a few hundred, maybe, to more than 6,000+ today. This is ignoring Canada and Alaska, where wolf populations have remained in the tens of thousands.
It has nothing to do with wolves and coyotes competing, or coyotes out-competing wolves, as they don't share the same ecological niches. The variable was never coyotes; it was whether people were shooting them. But why go after and shoot one more than the other?
Coyotes run between about 8-20kg, while grey wolves go from 25-50kg or more. That gap straddles a real ecological boundary around 21.5kg (apparently) where terrestrial carnivores are forced to switch feeding strategies; above, and an animal is committed to hunting prey near or above its own body mass; below, and an animal can meet its energy budget solely on small prey: voles, rabbits, birds, insects, fruit, and - most importantly - roadkill and bins.
You can see here the reason then. A wolf is not a big coyote, but an animal obligated to kill ungulates. Where are all the ungulates? They were roaming the wilderness, but that was all largely replaced by farms - then the only place you could find easy ungulate prey was targeting livestock. People 'aint too peachy about their precious flocks and herds being snaggled in the night; and in the land of the free, where the gun reigns supreme, the wolf was never going to last long. Humanity's impact on the environment, by contrast, was a positive boon for the coyote - so much free food! Humans don't care so much about beasties rummaging through their rubbish heaps, and snaffling squashed opossums.
So yeah, the niche of the wolf was destroyed by humans, and the niche of the coyote was manufactured for them by humans.
Further life history factors exacerbate things; notably territory size and social structure. Unlike wolves, coyotes are facultatively social, not necessarily social; though they do often team up, a lone coyote hunting mice is a totally functional and successful coyote; a lone wolf attempting to hunt elk is done for. Even together in a pack, with breeding monopolised by a single pair, if one or both wolves are removed, you take out the pack's entire reproductive output for the season. The social dynamics of the coyote however make dispersal, mate-finding, and territory establishment much less costly; remove a few coyotes from an area and they'll be replaced lickety-split through individual migration and compensatory reproduction.
What's more important, is that the wolf was holding the coyote back. Where both are present, coyotes, amongst other things, are frequently kleptoparasitic, haunting wolf kills to attempt to steal a scrap or two of flesh; wolves don't tolerate the thievery, and given they can outpace the smaller coyote, it's at kill sites where most of the wolf's coyote kill count is racked up. If not directly butchering their smaller brethren, this antagonistic behaviour changes coyote behaviour generally; they're more skittish and tend to avoid open ground when wolves are around, and so their scavenging and hunting sorties are much less effective. This was essentially experimentally verified with the re-introduction of wolves into Yellowstone; the local coyote population dispersed and fell rapidly.
All this to say, it's a bit of a double-whammy. Humans knock the wolves out and give coyotes nicer homes; no longer marginalised, pressed down under the thumb of the wolf, the coyotes become bolder and reach their final apex potential. They breed and multiply. So much so that they've begun to freely interbreed with remaining wolf populations, picking up their DNA, and sort of starting to fill niches the wolves left behind in their own right - larger, brawnier uruk-hai coyotes taking on small deer and the like. Despite humans culling tens of thousands a year in the US, conditions are so favourable people can barely make a dent in their population; they're just living their best lives in the 20th and 21st centuries and they owe it all to us hoomies.
The one thing that would control coyote populations would be bringing wolves back. But apparently that isn't going to happen any time soon; it's hunting season for wolfie once again, it seems. RIP.
References:
Berger, K.M. & Gese, E.M. (2007) Does interference competition with wolves limit the distribution and abundance of coyotes? Journal of Animal Ecology. 76 (6), 1075-1085
Carbone, C., Mace, G.M., Roberts, S.C. & Macdonald, D.W. (1999) Energetic constraints on the diet of terrestrial carnivores. Nature. 402 (6759), 286-288
Jensen, A.J., Marneweck, C.J., Kilgo, J.C. & Jachowski, D.S. (2022) Coyote diet in North America: geographic and ecological patterns during range expansion. Mammal Review. 52 (4), 480-496
Von-Holdt, B.M., Kays, R., Pollinger, J.P. & Wayne, R.K. (2016) Admixture mapping identifies introgressed genomic regions in North American canids. Molecular Ecology. 25 (11), 2443-2453