BROWSING FOR BROWSE! Feeding the zoo's specializd herbivores

Do you ever wonder what animals at the zoo eat? One of the most commonly fed items at the zoo is browse. Browse is the term used for the leaves, stems, and twigs of woody plants like trees and bushes. Animals that eat mostly browse in the wild are called browsers. Some of the browsers that make their home at Brookfield Zoo include giraffe, okapi, black rhino, gorilla, and colobus monkeys, among many other species!

Our Animal Welfare Science team recently published a literature review about the health and welfare benefits of providing browse in zoos. Research suggests that feeding on browse fulfills behavioral needs. Although the species fed at the zoo are typically those found in temperate climates (willow and oak, for example), these feeds better mimic the natural diets of browsers. Browse encourages animals to perform foraging behaviors and to spend more time eating throughout the day. For example, many animals like to peel the bark off branches and eat it, and giraffes use their long, specialized tongues to break off twigs and pluck leaves. This also provides animals with the opportunity to exercise dietary choice and control by allowing animals to choose what parts of the plant to eat.

Browse is also excellent for animal health. While the other parts of animal diets at the zoo give browsers complete nutrition, browse is an excellent additional source of fiber as well as certain vitamins and minerals. This encourages satiety (the feeling of being full). It also provides tannins, which are secondary plant compounds that may benefit digestive health and prevent disease. Browse is also good for dental health, and can act like a toothbrush to help clear plaque and keep teeth clean.

Our review also summarizes the challenges surrounding browse provision such as: how do zoos get enough browse? After all, some animals like the black rhino can eat over 50 pounds of food in a day! While the zoos can get some of its browse from their grounds department, most zoos must find other sources such as commercial growers or plant their own farms. Other zoos find creative ways of meeting their browse needs. For example, for Brookfield Zoo Chicago most of our fresh browse is collected throughout the Chicagoland area through a partnership with ComEd. Since 2011, the energy company has been donating the clippings from routine tree trimmings, which help keep power lines clear. This way, the branches that otherwise would have been discarded can be enjoyed by the animals at the zoo! Fresh browse is shipped to the zoo every week between spring and fall.

But what about during the winter? Our review also summaries the methods of preserving browse when fresh browse is not available, including drying, silage, and freezing. For example, staff at Brookfield Zoo Chicago have found a way to provide the leafy branches throughout the year by freezing whole pieces and thawing them later to feed to the animals. Freezing browse preserves its nutritional content, and allows for browse to be shared year-round!

You can find our review in the journal Zoo Biology, where it will be published in the first issue of this year. The next time you are at the zoo, keep an eye out for who might be enjoying browse in their habitat!

Maggie Ramont, MSc
Behavioral Research Assistant
Published January 23, 2025