Oregon Zoo

The 64-acre Oregon Zoo is located in Portland, a city and surrounding metropolitan area of more than 1.5 million people. Attendance in 2011 exceeded 1.6 million.
Oregon Zoo facts and numbers

The zoo has five major exhibit areas: Great Northwest, Fragile Forests, Asia, Pacific Shores and Africa. Within these large areas are 23 specialized exhibits.
Animals of the Oregon Zoo

    2,200 individual animals represent 260 species of birds, mammals, reptiles, amphibians and invertebrates
    21 endangered species and 33 threatened species live at the zoo.
    The zoo is active in 21 Species Survival Plans.

Plants of the Oregon Zoo

    Native plants of the Pacific Northwest's temperate rainforests have been cultivated to create naturalistic exhibits, pathways and vistas within the zoo.
    More than 1,000 species of exotic plants thrive in the zoo's botanical gardens, including firebird heliconia, pelican flower and ground orchid. Some are harvested and given to the animals as browse.

Volunteer information:  http://www.oregonzoo.org/get-involved/volunteer-zoo