Botanical gardens discussion reviews implementation, effects of deer cull
Close to 40 people filed into the Matthaei Botanical Gardens Auditorium Wednesday evening for a presentation on the effects deer have had on the parks of Ann Arbor, and in turn, the deer cull’s impact on local populations. The talk was hosted by Wild Ones, an organization aiming to protect native species of plants and animals.
The deer cull has been a controversial topic in Ann Arbor, with calls for the University of Michigan to cease its support of the cull, and for the city to stop funding the program entirely.
Presenter Jacqueline Courteau, a professional biologist who has studied the local environment for the past 20 years, acknowledged the program comes with considerable emotional baggage, and proceeded to outline policy and management implications from her research.
“Deer management is a complicated and controversial issue, and very emotional,” she said. “It is important to remember that deer exert many effects in their ecosystem.”
Corteau went on to discuss how browsing, the pattern of feeding wherein deer move through a wooded location and feed on underbrush, negatively affected forest growth and diversity in multiple local parks. One of the ways she — in cooperation with the University of Michigan — tried to quantify the damage done to plants by browsing is by systematically planting an indicator species like red oak, and observing how deer and other animals interacted with it.
She found 54 percent of red oak seedlings across 11 sites were browsed by deer. She deemed this especially concerning, given 15-percent browsing is generally considered the lower threshold for negative impact on forest repopulation on the whole.
“Browse proportion ranged from 20 percent to 90 percent depending on the site, but in half of the sites, 60 percent or more were deer-browsed, and some of them repeatedly,” she said.
According to Corteau’s research, another effective way to measure the impact deer have on plants is by creating exclosures throughout areas. This involves taking two similar plots of land, blocking one off so that deer cannot access it, and allowing the other to act as a control.
She found that, in one of the preserves she studied with exclosures, “plant size, average plant size, was significantly greater in the deer exclosure than either of the control plots, and those were not significantly different from each other.”
Paul Muller, a retired employee of the Metropark system, focused his talk on the implementation of the cull. Muller emphasized the entire parks and recreation community was concerned with carrying out the cull as effectively and ethically as possible, and outlined how the cull was the consensus of multiple environmental groups, was voted on multiple times and was adjusted when needed.
He also noted the positive effects of the cull, like the donation of all the meat to local food banks, which totals over 135,000 pounds to date.
“Deer-management programs have been a safe and cost effective deer-management program,” he said. “With careful planning and execution, our main focus was always safety when we were going through the whole process. Obviously you need proper funding and the political and public support, and you need a dedicated staff and employees.”
Organizer Andrea Matthies, the local chapter president of Wild Ones, understands that for many, the cull is a very emotional issue and they do not want to see deer killed. She hopes to inform the public about data regarding the effects of deer overpopulation on the local environment at large — in part by elaborating that popular initiatives, such as rain gardens and drives to plant native plants and save bees, will all be made easier with robust control of the deer population.
“I think that some people are just distressed on an emotional level what had become somewhat of a pet in their backyard,” she said. “They were really relating to deer more as a pet, whereas those of us involved in the world of native plants see them as the creatures who are eating the food that our native bees, butterflies, all of our pollinators, our native birds — that they are destroying that.”