Arboriculture at the zoo

Gorillas eating browse, grown at the zoo.

So, you think it’s a zoo where you work? You should see where Dan Simpson works. It really is a zoo, which means it’s also a very complicated life for an arborist.

Simpson is head arborist at the San Diego Zoo, although technically he’s called an associate horticulturist. His gardens are jungles, his workspaces are public exhibits and his clients are animals.

The San Diego Zoo is acclaimed as one of the world’s great zoos, sitting on 120 acres and featuring over 800 animal species and 4,000-plus individual animals on exhibit (not counting the insects) in Southern California. It also has over 1,000 species of trees that make up the backdrops for exhibits, specialized gardens and tree collections that are part of the facility’s commitment to environmental conservation. An ISA-certified arborist, Simpson has a crew of three that does the bulk of the tree work at the facility, two of whom are certified arborists and one a certified tree worker and arborist. Simpson also heads the Wild Animal Park, the zoo’s sister facility.

With such a varied forest, and with exhibits ranging from desert to rain forest, the tree crew must be knowledgeable and hard working. Because the public arrives at 9 a.m., and most jobs, including cleanup, must be completed by then if there has been pruning going on, scheduling is extremely important. Sometimes work starts at 5 a.m. Safety is a big focus here, with standard zoo security features ensuring that animals are locked out of the area the tree crew works in.

“The pruning we do in-house,” Simpson says, but the zoo hires tree service contractors to help with jobs that must be done quickly or that involve a massive project. For example, if a large tree is to be removed or relocated, a contractor with a crane may be hired.

An interesting part of the tree workers’ job is growing “browse” food for the animals on exhibit. There is a special eight-person “browse crew” under Simpson’s supervision that does little but grow and harvest food for koalas, panda bears and other critters. Twelve species of bamboo, for example, are used for koala fodder, out of over 70 species on the grounds, and much of this is grown in agricultural-type hedgerows specifically for food.

“We need tons per year of bamboo,” Simpson notes. The zoo also grows some browse for other facilities. He harvests some 40 species of ficus foliage, some of it for the Cincinnati Zoo’s rare Sumatran rhinoceros. About 150 species are grown for browse, and other prunings of hibiscus or other plants are often utilized in addition, especially for large mammals such as elephants and gorillas.

Arborists and other horticulturists at the San Diego Zoo cooperate to plant and care for trees and other landscaping, as well as species grown for the animals to eat.

As an arborist, Simpson feels that the zoo is a place where constant modifications to ISA standards are necessary. He has a boom truck, but his crew members are all rope and saddle climbers as well. He employs a vista pruning kind of methodology throughout the zoo grounds, especially the public areas, to maintain a pleasant and accessible environment. “It comes under the topic of habitat management in a confined space,” he says.

Tree and landscape workers at the zoo always have to keep the animals in mind, because they can cause behavior modification by being nearby and working with tools. Often, if chain saw use is necessary, workers start the saws some distance away from the exhibit and walk in carefully to allow the animals time to adjust to the noise and disturbance. During nesting season in the aviaries, this can be daunting, although, if precautions are taken and eye contact is avoided, birds will often remain on their nests throughout a work session.

Trees don’t grow in all exhibits because soil space for planting can be limited, but where they do grow they must be cared for as they would anywhere. Trees have to be pruned back from within the enclosures to keep construction materials from being pushed out of place. In addition, some trees must be protected from the animals themselves.

Having spent over 30 years at the San Diego Zoo, Certified Arborist Dan Simpson has become proficient at tree care in a public setting. The San Diego Zoo has a crew of eight who grow and cut ôbrowseö for picky animals like the panda, which has 12 species of bamboo cut for its use.

So, how do you prune a rain forest? The zoo designers want a wild look to the place, and yet elements such as sunlight for the health of the animals must be maintained. It’s pretty much an informal approach, he says. He also has to make sure that public access is safe and open for educational purposes, while making sure that the 3-mile, double-decker tour bus route is clear of low-hanging branches.

The San Diego Zoo is home to several accredited tree collections. Palm, coral and ficus collections are among those, and they have their own level of maintenance. Much of the tree care work after 9 a.m. is done behind the scenes. His crew also assists the large horticultural landscaping crew when there is a new exhibit or a renovation.

Simpson is involved in new designs at the zoo from the beginning in order to advise on the role of trees in exhibits. In the new Elephant Odyssey exhibit, for example, he was asked to help determine whether new tree species should be incorporated into it or whether trees from the renovated area could be employed. He’s also traveled to countries such as Ireland to help advise them on setting up koala exhibits.

The aviaries are particularly interesting to do tree work in, he says. Some have wire enclosures extending 100 feet high, and hundreds of birds live in there. It is up to the arborists to thin out branches so that visitors can see the birds while still maintaining a wild look to the place. At the same time, walkways for visitors must be kept clear, and trees pruned so that fruit doesn’t fall onto paths.

Simpson came to work at the zoo in 1971, after owning his own tree service company. He has gone through a lot of ISA training and has come up through the ranks at the zoo. His next goal is to attain board-certified master arborist status.

Don Dale is a freelance writer and a frequent contributor. He resides in Altadena, Calif.