Monday, August 11, 2008

Coyotes of New England

While I was writing about ziphiids, I couldn't help but notice that coyotes (Canis latrans) established themselves in my neighborhood. I've seen the occasional individual around before but the chorus howls only started a couple of months ago. The coyotes seem to avoid me (probably because I make a lot of noise running at night) although they seem to have been within 50 feet of my residence judging by tracks and my neighbors reported them exhibiting curious behavior. Coyotes are still rather recently established in the Eastern US (the eastward expansion started c. the late 1800's) but they don't seem to be quite like their Western relatives.

Eastern coyotes differ from their Western relatives by preying on deer more frequently, living at lower densities, in larger home ranges and smaller group sizes (Way 2007). The largest reliably recorded* extant coyote was a 25.1 kg (55.3 lb), 1.57 m long female ("Casper") from Barnstable, Cape Cod, Massachusetts (Way and Proietto 2005); E. Mass./Cape Cod has the second largest average coyote sizes (17.9 kg M, 16 kg F) and is exceeded by New Hampshire (20.4 kg M, 17.9 kg F) (Way 2007). Weight can vary a lot due to condition, hydration, season and so forth (as opposed to skeletal length) and while average size figures will undoubtedly be revised, the difference between Eastern and Western coyotes (overall average: 11.4 kg M, 10.5 kg F) is consistent and significant enough for them to be placed in different size categories (Way 2007). So how did these coyotes get significantly larger all the sudden and apparently occupy a distinct niche?

*Other records of 25 kg+ coyotes are secondhand and questionable (Way and Proietto 2005).

It has been suggested that there are three possible reasons for large size in Eastern coyotes: introgression of wolf genes, genetic selection due to larger prey size/food supply or phenotypic response to enhanced food supply (Thurber and Peterson 1991). Thurber and Peterson thought the size difference was phenotypic* due to the time frame and because recently arrived coyotes in Alaska did not show larger size than their southern cousins. The authors suggest that this is due to less available food in Alaska, but it needs to be pointed out that the Eastern wolf (C. lycaon) may be a closer relative of the coyote than the wolves that live in the west (C. lupus). North American "higher canids" (C. lupus, C. lycaon/C. rufus, C. latrans) have a rather ambiguous phylogeny thanks to possible hybridization and introgression (Zrzavy and Ricankova 2004) and an article documenting eastern coyote genetic ancestry has yet to be published. Jon Way's website mentions that there is a study awaiting publication on this subject which concludes that the eastern coyote is distinctive and has heritage from both the western coyote and eastern wolf (C. lycaon). Apparently the paper will consider the eastern coyote to be a distinct species, although I'm not sure if eastern coyotes should qualify as anything more than a distinct population. If the admixture really is as extensive as it appears, maybe the coyotes and the eastern wolf (C. lycaon) should be considered some "higher Canis complex" or maybe even the same species. I'll definitely have to comment upon this when it eventually gets published.

* Larivière and Crête 1993 noted that New Hampshire coyotes reached a larger size in captivity than western ones. However, Thurber and Peterson 1991 didn't entirely rule out hybridization in some localized areas.

The idea of having a considerably sized* wild canid roaming around suburban areas is undoubtedly going to make some people uncomfortable, but at the moment there doesn't seem to be much to be concerned about. Well, in New England at least, California has 111 attacks on record (vs. 7 for New England) including one fatality (Timm and Baker 2007). These attacks are the result of habituation caused by increased coyote presence in the area and human activities towards them, such as intentional feeding (Timm and Baker 2007). Domestic dogs are of course responsible for far more fatalities (4 in California from 95/96, see footnotes) and attacks, but we should still try and prevent this sort of situation developing in New England. Much larger coyotes with tendencies to prey on larger animals could be trouble...

*The coyotes that I've seen didn't seem to be much smaller than a greyhound, but the average weights in RI are 16.6 kg (36.5 lbs) M and 15.3 kg (33.6 lbs) F (Way 2007). The record was a 21.1 kg (47 lbs) female (Way 2007). Unexpectedly seeing a canid at night undoubtedly makes them seem much larger.

I'll have to see if I can manage to get a picture of one of these canids, geez has my summer disappeared.


Larivière, S., and M. Crête. 1993. The size of eastern coyotes (Canis latrans): A comment. Journal of Mammalogy 74 (4):1072–1074.

Murray, D. L. and Waits, L. P. 2007. Taxonomic status and conservation strategy of the endangered red wolf: a response to Kyle et al. (2006). Conserv. Genet. 8, pp. 1483–1485

Peterson, Rolf O. and Thurber, Joanne M. 1993. The size of eastern coyotes: A rebuttal. Journal of Mammalogy 74 (4): 1075-1076

Thurber, Joanne M. and Peterson, Rolf O. 1991. Changes in Body Size Associated with Range Expansion in the Coyote (Canis latrans). Journal of Mammalogy, 72 (4) pp. 750-755

Timm, Robert M. and Baker, Rex O. 2007. A History of Urban Coyote Problems. Proceedings of the Wildlife Damage Management Conference, Available

Way, Jonathan G. 2007. A Comparison of Body Mass of Canis latrans (Coyotes) Between Eastern and Western North America. Northeastern Naturalist. 14 (1) pp. 111- 124.

Way, Jonathan G. and Proietto, Robert L. 2005. Record Size Female Coyote, Canis latrans. The Canadian Field-Naturalist v. 119, pp. 139-140

Zrzavy, Jan and Ricankova, Vera. 2004. Phylogeny of Recent Canidae (Mammalia, Carnivora): relative reliability and utility of morphological and molecular datasets. Zoologica Scripta, 33 (4), pp. 311–333

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