Keeping predator populations in check may have adverse consequences on habitat

(Edmonton) Thin out too many cougars and wolves that prey on moose and deer, and it means that bird and butterfly populations could also dwindle, University of Alberta research has discovered.

U of A master’s student Kristine Teichman is spending the second of two summers monitoring the birds, butterflies and shrubs in and around Elk Island National Park east of Edmonton, to determine how heavily ungulate populations�moose and deer�are feeding, or “browsing,” on vegetation in habitats used by shrub-dependent birds and butterflies.

For her thesis, Teichman, a student in the Department of Biological Sciences, is trying to answer the question of whether large ungulate populations in the aspen parkland are consuming too much vegetation, particularly shrubs, thereby threatening populations of some North America’s shrub-nesting birds and butterflies.

Teichman’s results are beginning to show that too many deer and moose affect other animals dependent on shrubs. She believes that wolves and cougars, once the top predators of the aspen parkland, play a key role in maintaining biodiversity, and her research is exploring an active area of debate in ecology and conservation: the question of just how important top predators are in regulating diversity and what are the consequences of their loss.

“While some research is finding that predators may promote biodiversity in some ecosystems and not in others, my research is suggesting that predators are important to naturally limit moose and deer populations, to maintain a biologically diverse ecosystem,” she said.

In fact, research has already shown that declines in cougar numbers boosted deer populations, resulting in the loss and alteration of vegetation along streambeds. This affected the survival of some fish and amphibian species, she noted.

Basing her research in and around Elk Island because of high moose and deer populations, Teichman has been recording just how heavily browsed different areas are inside and outside the park. Her early results indicate that vegetation is more impacted inside the park, which is fenced and where ungulates are protected against wolves and cougars.

Teichman is measuring the browse, height and density of vegetation and counting bird and butterfly populations. Her concern is that reductions in the size and density of willow, aspen, gooseberry, chokecherry and saskatoon bushes will limit nesting areas and larval food plants for birds and butterflies, respectively. Currently, she estimates the aspen parkland is home to approximately 50 species of butterflies. As part of her work, she is monitoring up to 10 of those species.

Her research to date shows that at least one species of bird, the yellow warbler, has lower numbers inside the park than outside its boundaries.
Teichman believes that by examining the consequences of the loss or reduction of top predators from natural systems, wildlife managers can make informed decisions when the goal is maintaining biological diversity.

Her work is co-supervised by Scott Nielsen, professor of renewable resources and Jens Roland, professor of biological sciences and is funded by the Alberta Conservation Association, the Alberta Sport, Recreation, Parks and Wildlife Foundation, Natural Sciences and Engineering Research Council, a Queen Elizabeth II Graduate Scholarship and a University of Alberta Graduate Teaching Assistantship.