Coywolf is an informal term for a canid hybrid descended from coyotes, eastern wolves, gray wolves, and dogs. All members of the genus Canis are closely genetically related with 78 chromosomes and therefore can interbreed. One genetic study indicates that these two species genetically diverged relatively recently (around 55,000–117,000 years ago). Genomic studies indicate that nearly all North American gray wolf populations possess some degree of admixture with coyotes following a geographic cline, with the lowest levels occurring in Alaska, and the highest in Ontario and Quebec, as well as Atlantic Canada. Another term for these hybrid is sometimes wolfote. Description Hybrids of any combination tend to be larger than coyotes but smaller than wolves; they show behaviors intermediate between coyotes and the other parent's species. In one captive hybrid experiment, six F1 hybrid pups from a male northwestern gray wolf and a female coyote were measured shortly after birth with an average on their weights, total lengths, head lengths, body lengths, hind foot lengths, shoulder circumferences, and head circumferences compared with those on pure coyote pups at birth. Despite being delivered by a female coyote, the hybrid pups at birth were much larger and heavier than regular coyote pups born and measured around the same time. At six months of age, these hybrids were closely monitored at the Wildlife Science Center. Executive Director Peggy Callahan at the facility states that the howls of these hybrids are said to start off much like regular gray wolves with a deep strong vocalization, but changes partway into a coyote-like high pitched yipping. Compared with pure coyotes, eastern wolf × coyote hybrids form more cooperative social groups and are generally less aggressive with each other while playing. Hybrids also reach sexual maturity when they are two years old, which is much later than occurs in pure coyotes. Varieties Eastern coyotes Eastern coyotes range from New England, New York, New Jersey, Pennsylvania, Ohio, West Virginia, Maryland, Delaware, and Virginia. Their range also occurs in the Canadian provinces of Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island and Newfoundland and Labrador. Coyotes and wolves hybridized in the Great Lakes region, followed by an eastern coyote expansion, creating the largest mammalian hybrid zone known. Extensive hunting of gray wolves over a period of 400 years caused a population decline that reduced the number of suitable mates, thus facilitating coyote genes swamping into the eastern wolf