The eastern Coyote or Coywolf (Canis latrans × C. lycaon) inhabiting northeastern North America resulted from hybridization between the expanding population of the western Coyote (Canis latrans) and the remnant population of Eastern Wolf (C. lycaon) and possibly domestic dogs (C. lupus familiaris) in the early 20th century. This study compares the body mass of eastern (i.e., northeastern) Coyotes, western Coyotes, and Eastern Wolves and synthesizes the recent literature to gain better insight into the taxonomic relations and differences of closely-related Canis species. Northeastern Coyotes (males = 16.5 kg; females = 14.7 kg) were statistically (P < 0.0001) intermediate in mass between western Coyotes (males = 12.2 kg; females = 10.7 kg) and Eastern Wolves (males = 28.2 kg, females = 23.7 kg), consistent with their hybrid origin, but were numerically closer to western Coyotes. Large Cohen’s d (3.00–8.56), (0.915–0.929), and Cohen’s f (3.28–3.62) values indicated large effect sizes from the body mass comparisons. Eastern Wolves were 61–71% heavier than the same sex in the northeastern Coyotes, which in turn were ca. 35–37% heavier than the same sex in the western Coyotes. Alternatively, western Coyotes were 73–74% of the size of the same sex in the northeastern Coyotes, which in turn were 59–62% of the size of the same sex in the Eastern Wolves. I also attempted to relate mitochondrial DNA (mtDNA) haplotypes to body mass. Six of 17 (35.3%) adult female northeastern Coyotes captured in Massachusetts weighed ≥18 kg, heavier than any other described Coyote from outside northeastern North America. Mitochondrial DNA haplotypes associated with these heavy female northeastern canids were C9 = 4, C19 = 1, and C48 = 1. Body mass (kg) and mtDNA haplotype data of 53 northeastern Coyotes (males = 28, females = 25) showed no difference between haplotype and body mass for males (P < 0.852) or females (P < 0.128), suggesting that there is not a particular haplotype (e.g., C1) that is associated with the heavier animals. I propose that the most appropriate name for this hybrid animal is Coywolf (Canis latrans × C. lycaon), rather than a type of Coyote. Coywolves are distinct, being larger than any other population of Coyotes but smaller than Eastern Wolves. I propose that the 5 distinct types of Canis be recognized as: western Coyote, Coywolf (northeastern Coyote), Eastern Wolf (including Red Wolf C. rufus), Gray × Eastern Wolf hybrids (‘Great Lakes’ Wolves; C. lupus × C. lycaon or C. lycaon × C. lupus), and Gray Wolf (C. lupus). The implications for wolf recovery in the northeastern United States is discussed.
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)