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African wild dogs play tug of war with browse at Brookfield Zoo
A partnership is blooming between the Chicago Zoological Society, which manages Brookfield Zoo, and ComEd, one of the zoo’s sponsors. The electric company is providing browse—leaves, twigs, and branches from trees and shrubs—for many of the zoo’s animals.

The zoo’s Grounds Department is constantly trimming trees and providing browse for the animals. However, at Brookfield Zoo there is no such thing as too much browse, and now—thanks to ComEd—more animals are enjoying an endless supply.

Each week, ComEd makes two deliveries of 20 to 25 cubic yards of browse per truckload. The browse is from trees that are trimmed along transmission tower corridors located throughout the Chicago metropolitan area. The zoo’s staff nutritionist has provided ComEd with a list of approved plant and tree species, which includes some of the animals’ favorites, such as sugar and silver maple, willow, grapevine, mulberry, box elder, honey locust, and alder.

After each delivery, keepers from the zoo’s Commissary load up their truck and make the rounds to the various exhibits, depositing the tasty treats for the animals, including gorillas and other primates, giraffes, grizzly bears, rhinos, kangaroos, and Rodrigues fruit bats, to name just a few.

“We are very appreciative of ComEd’s weekly browse donations to Brookfield Zoo’s animals,” said Jennifer Watts, Ph.D., nutritionist for the Chicago Zoological Society. “Fresh browse is a natural method for promoting the animals‘ gastrointestinal and dental health, but it is also a great way to provide enrichment to the animals.” Some animals go as far as stripping off the bark to eat, others use it for a body massage, and still others, like the African wild dogs, just run around with it. In addition, some of the larger branches are being used as deadfall in the animals’ habitats.

“As a responsible corporate citizen, our top priority is delivering reliable electricity to northern Illinois residents and businesses, but we’re always looking for new ways to partner with communities and
build in efficiencies,” said Mike McMahan, ComEd vice president of smart grid and technology. “Teaming up with our friends at Brookfield Zoo was a natural fit—we recycle 100 percent of our tree trimmings anyway—and it’s relatively easy for us to share some of what we collect each week with the animals that are helping to educate families about the importance of conserving our natural resources.”

As a part of its ongoing reliability enhancements, ComEd trims trees along its high-voltage distribution circuits on a four-year cycle. The company trims approximately 9,000 miles of tree line each year. Additionally, ComEd performs “midcycle” trimming on sections that have higher incidences of outages related to tree contact. The company spends more than $60 million a year on tree trimming and has invested nearly $10 billion in the last decade, improving reliability by nearly 40 percent.

The browse deliveries will stop at the end of October before beginning again in the spring. In order for the animals to continue to get browse year-round, staff will be freezing some of it. Additionally, some of the leaves and smaller twigs are being stored in barrels to create silage, a type of fermented browse that can last for up to eight months, thus making it possible for the hoofed animals to enjoy this treat in the winter.