Plate 111 of the Birds of America by John James Audubon, depicting the pileated woodpecker. Adults are 40 to 49 cm (16 to 19 in) long, span 66 to 75 cm (26 to 30 in) across the wings and weigh 250 to 400 g (8.8 to 14.1 oz), with an average weight of 300 g (11 oz).
How Wolves Help. Wolves play a very important role in the ecosystems in which they live. Since 1995, when wolves were reintroduced to the American West, research has shown that in many places they have helped revitalize and restore ecosystems. They improve habitat and increase populations of countless species from birds of prey to pronghorn, and even trout.
Wolves commonly function in packs consisting of two to nine individuals; packs basically are family units. Pack cohesion is based on ties developed during courtship of adults and those developed during early life of the young. Wolves may be active at any time, but tend to be more active at night. They travel extensively. Howling, distinctive among individuals, is used to assemble the pack and to advertise the territory.