here is what I found through my research
a western male coyote will tip the scales around 35 pounds, a eastern male will go 50, 60, even 70 pounds. all I have read points to the conclusion that when coyotes started expanding east, they could not cross the Mississippi River, so they went north above the Great Lakes, in the north they crossed with grey wolves and various dog breeds. coyotes do not hunt in packs, wolves do, carrying this trait when food gets scarce, and the weather is bad, they pack up and when packed their fear of humans is not as great as when they are paired up. I personally have killed eastern coyotes to 51 pounds, by far larger than their western cousins.
RR