January 14, 2016
Topic: Campus News
A University of Michigan evolutionary biologist says he and many of his U-M colleagues support the city of Ann Arbor's plans to kill up to 100 deer this winter, calling the cull "a positive step toward ecological sustainability."
Christopher Dick, associate professor of ecology and evolutionary biology and director of the E.S. George Reserve, explains his position on the proposed deer cull in a guest commentary in Bridge Magazine, which is published by The Center for Michigan.
According to the city of Ann Arbor's website, the goal of the deer-management program is to decrease the city's deer population "in order to reduce deer-human negative interactions and support biological diversity in natural areas."
For evidence that deer culls help restore ecological balance and biodiversity, people need to look no further than U-M's 1,300-acre E.S. George Reserve near Pinckney, according to Dick.
In 1928, four does and two bucks were released there, and the population rose from six deer to more than 160 deer in six years. Browsing by deer damaged trees and shrubs and suppressed plant succession, Dick wrote.
Since 1942, E.S. George Reserve stewards have periodically culled the deer herd, leading to a steady recovery of oak, hickory, maple and other native plant species, according to Dick.
"The Ann Arbor deer cull may not reverse decades of ecological degradation or prevent all diseases," he wrote. "But with around 150 tons of buds, leaves and flowers that will be spared this year alone, it is a positive step toward ecological sustainability."
Dick said he discussed the urban deer issue with other U-M biologists, including ecologists, botanists, zoologists, restoration ecologists and landscape architects.
"We are all in support of the city council's decision to conduct a cull," he wrote.
In the past century, whitetail deer numbers have swelled to historic highs across much of North America, threatening ecosystems.
A single whitetail deer eats roughly 3,000 pounds of plant material each year. Herds remove swaths of forest wildflowers and damage the woody understory, according to Dick. This affects native butterflies, bees, small mammals, amphibians and some birds.
Whitetails alter forest composition by browsing oak and other hardwood seedlings. Their food preferences allow unpalatable species to proliferate, including invasive garlic mustard and Japanese barberry, which inhibit the next generation of forest trees and native wildflowers.
Deer occur in even higher abundance in urban settings, Dick wrote. City parks and suburban gardens are rich in their preferred foods, and the deer are safe from hunting and natural predators there.
U-M botanists have long noted declines in native plants that deer favor, Dick said. In a 2015 study, an ecological team surveyed browsing impacts in Ann Arbor's Bird Hills Nature Area and found browsing damage in 80 percent of the tree saplings, according to Dick.
"From ecological and conservation perspectives, an ideal deer herd will coexist with a full range of native species," he wrote. "By several measures, Ann Arbor's herd size has surpassed this threshold."
Apart from its ecological value, deer culling is an important tool for combatting emergent diseases such as chronic wasting disease and Lyme disease, according to Dick, who is also director of the U-M herbarium.