Lately, “coywolves” have been making headlines and raising eyebrows. They are a wild canid that is a hybrid between a coyote and a wolf. It may sound like an urban legend, but coywolves are real.* I first learned about this quirky common name via a news article from The Star in Canada, Meet the Coywolf (by , which does a surprisingly good job of detailing the coywolf and its increasing run-ins with humans on the eastern edge of greater Toronto. And now, a new study is out offering both a coarse-scale genetic analysis of this new hybrid species, and specific trends in their skull shape.
One thing I find so interesting about this phenomenon is the plasticity of the two species that they can interbreed so successfully. Why is this? Species within the Canid genus have a remarkable ability for crossing the species barrier and procreating under certain conditions. Dogs (Canis familiaris) can mate with some wolves (Canis lupus). Wolves can mate with coyotes (Canis latrans). And unlike other species that create infertile hybrids, the offspring of these pairings can be fertile, so when these hybrid offspring mate and produce their own pups, they introduce new genes into one of their parent populations. For example, when a coyote and a wolf mate and create a hybrid, and then that hybrid lands a coyote suitor and they have their own pups, those pups are born with some wolf genes that are then brought into the coyote population.
Until recently, most of the public’s attention has been directed at the affect of coyote hybridization upon wolves, with little conversation about the effects of wolf hybridization upon coyotes. The general thought in the U.S. seems to be that there are plenty of coyotes — so why worry about them — but since wolves are largely endangered here, we need to protect their genetic diversity from “pollution” by coyotes. But what about the coyotes? How might wolf genes be helping or hurting them?
A new study published Sept. 23, 2009 in the journal Biology Letters asserts that coyote-wolf hybridization events in the northeastern U.S. have lent coyotes genes that gave them an extra edge when expanding their range into new territories. The study by Roland Kays, et al. analyzed mtDNA from 686 eastern coyotes and analyzed 196 skull measurements associated with what the authors call the coyotes “two-front colonization pattern.” The two-fronts relate to the coyotes expansion from the Great Plains and then a.) north and east the long way around the Great Lakes, and b.) a straight shot due east from Ohio, the short way below the Great Lakes. Intriguingly, the study states that the coyotes expansion on the longer front north around the Great Lakes occurred at a rate five times faster than the coyotes that expanded along the short route. They attribute this speed to the coyotes exposure to wolves in Canada along the northern route, whereas the coyotes along the southern Great Lakes route expanded in the absence of wolves, which had been extirpated in the previous 90 years. The two expanding fronts then met, giving scientists an opportunity to compare the effects of geographic travels upon each front.
What could make animals from the same parent population expand five times faster in one direction versus another? Kays and his team say that as the northern front of coyotes expanded around the Great Lakes, they hybridized with eastern wolves in Ontario. The injection of wolf genes into the coyote population in this area then led to larger coyotes, which in turn enabled them to hunt deer. Kays and his team also found evidence that the coywolves have a stronger bite than traditional coyotes do, as evidenced by skull musculature. Previously, some scientists had suggested that the larger coyote body size may be due to natural variation (phenotypic plasticity), but the authors state that:
Our results show that northeastern coyote populations are a hybrid swarm resulting from the widespread introgression of GLW [Great Lakes Wolves] genes. This suggests that hybridization introduced genetic variation for the rapid adaptation of more efficient predation on deer, including larger predator body size and skull dimensions.
Their nickname casts a playful tone, but these new hybrids are larger than their western coyote relatives and smaller than wolves. And their larger size is enabling them to hunt larger prey, which has definite ecological implications. According to the Star article at the top of this post, people are reporting that the hybrids act bolder, like a wolf, but have retained the coyotes tolerance for urban areas. While only anecdotal, this does seem to be a logical extension of their larger stature.
The coywolves, then, have benefited from the wolf genes they acquired en route around the northern edge of the Great Lakes, and they are undergoing adaptive evolution. Kays’ study details the case that these animals have undergone a genetic change which has allowed them to use their environment differently (hunting larger prey) while at the same time, their environment has changed in the past century due to the eradication of wolves in the U.S.
What I find so interesting is that the traditionally western coyote acquired genes from eastern Canadian wolves, and brought those genes back to a region where eastern wolves had been extirpated decades ago. I wonder to what degree these new coywolves will have an ecological impact in the east. Will conservation biologists one day be arguing for their protections, if they prove to play a similar role in the ecosystem as the extirpated red wolf, which once occupied land from the southeastern U.S. northward into southeastern Canada? And will people adapt to the coywolf as readily as it has adapted to its new habitat and us?
NOTES and SOURCES:
1. I originally wrote this post in August 2009; but in switching over to using ResearchBlogging.org I needed to re-post it for their system to recognize it. Thanks for your patience.
2. * Addendum (Feb. 2010) I have learned that Roland Kays, whose work is reported on here, does not support using the term “coywolf” to describe these hybrids. This came out in a Boston Globe article published on Feb. 17, 2010.
Kays R, Curtis A, & Kirchman JJ (2010). Rapid adaptive evolution of northeastern coyotes via hybridization with wolves. Biology letters, 6 (1), 89-93 PMID: 19776058