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 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
* Larivière and Crête 1993 noted that
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
*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.
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
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