UNIVERSITY PARK, Pa. -- Selective browsing by white-tailed deer likely is promoting the spread of some invasive plant species in northeastern U.S. forests, as deer avoid eating vegetation they find unpalatable.
That's the conclusion of researchers who conducted a study of deer dietary choices at the Penn State Deer Research Center, during which captive deer were simultaneously offered a selection of eight non-native invasive and seven native plants to determine the animals' preferences.
The research is important because it quantifies interactions between deer and invasive plants -- and how, over time, deer might be exacerbating problems with non-native plant species, according to researcher David Mortensen, professor of weed ecology in Penn State's College of Agricultural Sciences. He expects the findings to contribute to the conservation of forest understories and natural areas.
"This study provides evidence that deer impacts on plant invaders depend on plant species' palatability," he said. "Consequently, deer selectivity likely plays an important role in the invasion process. To the extent that herbivory impacts plant communities, these results suggest that deer promote the spread of some plant invaders by avoiding them."
In the study, published this month in the journal Biological Invasions, researchers documented feeding preferences of eight mature does without fawns through three seasons (late summer, early autumn and spring). The 15 plant species were offered in containers where deer could choose among them. A camera activated by a motion detector and infrared-enabled for night viewing allowed the researchers to observe and record deer behaviors. The amount of each plant consumed also was measured.