The zoo, which is situated on 5 acres (2.0 ha) of land, is built on the site of a historic train station and consists of domestic animals, as well as wildlife that is native to North America.

Cosley Zoo, the DuPage County Forest Preserve, and other local partners have teamed up in an effort to increase the population of the Illinois state endangered Blanding's turtle.

Eggs are incubated and hatched at a partner facility, then some arrive at Cosley Zoo where they will be reared for about a year before being released back in to a DuPage County wetland.

The zoo has helped rear and release more than 4,000 Blanding's turtles since becoming involved with the head start component of the Blanding's Turtle Recovery Project in 2001. four-toed salamander, Cope's gray tree frog, gray tree frog American kestrel, American robin, Baltimore oriole, barn owl, blue jay, brown-headed cowbird, chicken, domestic duck, gray catbird, great horned owl, Hahn's macaw, killdeer, mallard, northern pintail, red-tailed hawk, redhead, Sandhill crane, screech owl, turkey vulture, wood duck giant African millipede, Honduran curly hair tarantula, Madagascar hissing cockroach American guinea hog, black angus cattle, Canada lynx, coyote, four-toed hedgehog, Guernsey cattle, domestic rabbit, lesser Madagascar hedgehog tenrec, llama, miniature donkey, miniature horse, Montadale sheep, nine-banded armadillo, North American porcupine, Norwegian Fjord horse, Nubian goat, raccoon, red fox, white-tailed deer Blanding's turtle, California kingsnake, central bearded dragon, common bullsnake, corn snake, eastern blue-tongued skink, eastern box turtle, eastern rat snake, midland painted turtle, three-toed box turtle, western dusky hognose snake On November 9, 1973, Paula Jones donated 2.65 acres of land in honor of relative Harvey Cosley.

[2] It started its work with the DuPage County Forest Preserve District to rehabilitate Illinois' Blanding's turtle population in 2001.