Here is an image of a Coyote I photographed back in 2006 and what an expert from NH Fish & Game had to say about it:
Hi Paul, The animal photographed, in this magnificent photo, is an eastern coyote. Eastern coyotes have wolf genetics, thus is a "cross" considering an evolutionary biologist stand point.
My identification is based on the ear to head proportion, head size, nose shape and ear shape. I also used the beech leaves as an approximate scale.
Given the animals robust size and body shape I can understand why some would believe the animal is wolf. However it is not the body size and shape that assist biologist with wild canid identification. Given that eastern coyotes are a cross of western coyote/wolf genetics, a large coyote can look wolf like and a small wolf can look coyote like. Thus, biologist look at the details I used above.
Another identifier of coyote versus wolf is the animals tail use when moving. Wolves point the tail straight out when moving, eastern coyotes keep the tail down. I could not use this identifier as it appears the animal was standing still when photographed.
Sincerely,
Patrick Tate
New Hampshire Fish & Game Department
Furbearer Project Leader
Region 3 Wildlife Biologist
225 Main St, Durham NH, 03824