Page updated July 21, 2016. This page succinctly summarizes and provides PDFs of the recent papers that describe the coywolf and how it formed thru hybridization between western coyotes and eastern wolves, as well as with gray wolves and domestic dogs. It is most likely that human induced habitat changes (i.e., clearing the forest) and persecution of wolves allowed western coyotes to colonize the east starting in the 1800s. On their collective way past the Great Lakes states, western coyotes met eastern wolves in southeastern Ontario and the two species hybridized in the early 1900s to form this hybrid “coywolf”. Recent data shows that this animal also has gray wolf and domestic dog genetic introgression as well. The animal subsequently colonized and saturated just about all available habitats in the Northeast US and Southeastern Canada since those early colonization events.
Below is a list of the important papers that show the morphological and genetic introgression between coyotes and wolves that formed the eastern coyote/coywolf. The papers are roughly in order of date of publication with the most recent papers appearing first (at the top of this list):
Way, J.G. 2016. Why the eastern coyote should be a separate species: the ‘coywolf’. The Conversation. 11 May. URL: https://theconversation.com/why-the-eastern-coyote-should-be-a-separate-species-the-coywolf-59214. This paper explains why I believe the eastern coyote should be called coywolf, Canis oriens. It is written in the academic journal The Conversation to explain, in layman’s language, the findings of the article just below here (Way and Lynn 2016).
Way, J.G. and Lynn, W.S. 2016. Northeastern coyote/coywolf taxonomy and admixture: A meta-analysis. Canid Biology & Conservation 19(1): 1-7. URL: http://canids.org/CBC/19/Northeastern_coyote_taxonomy.pdf. This paper summarizes the literature (much of the pertinent literature being on this weblink page) and suggests that not only should ‘coyotes’ in the Northeast be called coywolves, but that they warrant new species status, Canis oriens – meaning eastern canid! The meta-analysis concludes that the coywolf in the Northeast is ~60% coyote, 30% wolf, and 10% dog.
Rutledge, L.Y., Devillard, S., Boone, J.Q., Hohenlohe, P.A. and White, B.N. 2015. RAD sequencing and genomic simulations resolve hybrid origins within North American Canis. Biology Letters 11: 20150303. http://dx.doi.org/10.1098/rsbl.2015.0303. This paper conclusively determines that eastern wolves are a unique species and that the eastern coyote/coywolf formed due to hybridization between western coyotes and eastern wolves.
Monzón, J., Kays, R. and Dykhuizen, D.E. 2013. Assessment of coyote–wolf–dog admixture using ancestry-informative diagnostic SNPs. Molecular Ecology 23:182-197. doi: 10.1111/mec.12570. This paper uses some of the newest genetic techniques (mainly SNPs) to show that the eastern coyote/coywolf has western coyote, eastern wolf, gray wolf, and domestic dog genes.
Way, J.G. 2013. Taxonomic Implications of Morphological and Genetic Differences in Northeastern Coyotes (Coywolves) (Canis latrans × C. lycaon), Western Coyotes (C. latrans), and Eastern Wolves (C. lycaon or C. lupus lycaon). Canadian Field-Naturalist 127(1): 1–16. This is an important scientific paper suggesting that the eastern coyote should more appropriately be called “coywolf” given their mixed species ancestry and intermediate morphological and genetic status. It counters some of the claims made by Chambers (2010, see below).
Rutledge, L. Y., P. J. Wilson, C. F. C. Klutsch, B. R. Patterson, and B. N. White. 2012. Conservation genomics in perspective: A holistic approach to understanding Canis evolution in North America. Biological Conservation 155: 186-192. Note: this paper focuses on eastern wolves and I share it here because it is the most up-to-date paper summarizing the literature and concluding that eastern wolves are a unique species. In essence, it counters recent papers (cited within) that claim that eastern wolves are western coyote x gray wolf hybrids.
Bozarth, C. A., F. Hailer, L. L. Rockwood, C. W. Edwards, and J. E. Maldonado. 2011. Coyote colonization of northern Virginia and admixture with Great Lakes wolves. Journal of Mammalogy 92(5): 1070-1080. This paper shows that coyotes in the mid-Atlantic area also have wolf genes but to a lower extent than eastern coyotes (coywolves) in the Northeast.
Chambers, S. M. 2010. A perspective on the genetic composition of eastern coyotes. Northeastern Naturalist 17(2): 205-210. This paper counters some of the claims in the Way et al. (2010) paper below; note: Way (2013, above on this webpage) counters many of the claims made herein.
Way, J. G., L. Rutledge, T. Wheeldon, and B. N. White. 2010. Genetic characterization of eastern “coyotes” in eastern Massachusetts. Northeastern Naturalist 17: 189-204. This and the Kays et al. (2010) paper are the first papers to “officially” (i.e., thru scientific reporting) acknowledge that the canids in the east are part-wolf (i.e., have wolf genetic introgression) despite decades long speculation and theories supporting this thought.
Wheeldon, T. J., B. Patterson, and B. White. 2010. Reply to Kays et al. on northeastern coyotes. Biology Letters E-Letter Reply. URL: http://rsbl.royalsocietypublishing.org/content/6/2/248.full/reply#content-block.
Kays, R., A. Curtis, and J. Kirchman. 2010. Reply to Wheeldon et al. ‘Colonization history and ancestry of northeastern coyotes’. Biology Letters 6(2) 248-249. Note: this PDF includes the Wheeldon et al. paper immediately below this link.
Wheeldon, T., B. Patterson, and B. N. White. 2010. Colonization history and ancestry of northeastern coyotes. Biology Letters 6: 246-247. Note: this PDF includes the Kays et al. paper immediately above this link.
Kays, R., A. Curtis, and J. J. Kirchman. 2010 Rapid evolution of northeastern coyotes via hybridization with wolves. Biology Letters 6: 89-93. See Way et al. (2010) four papers above for comments relating to the significance of this paper.
Way, J. G. 2007. A comparison of body mass of Canis latrans (Coyotes) between eastern and western North America. Northeastern Naturalist 14: 111-124. This paper conclusively shows that ‘coyotes’ in the Northeast are the heaviest type of ‘coyote’ in North America. This paper came out prior to official genetic acknowledgement that coyotes and wolves hybridized to from the eastern coyote/coywolf.
Way, J. G., and R. L. Proietto. 2005. Record size female Coyote, Canis latrans. Canadian Field-Naturalist 119: 139-140. This paper details a large 55-lb female eastern coyote/coywolf!