It’s great to see animals like deer, rabbits, squirrels, et cetera, in the Natural Lands, especially at this time of year. When the air is freezing and the snow is falling (or not) the sight of these cute critters will raise your spirits and make you feel warm and cozy again. One of our most conspicuous residents is our population of white-tailed deer, or Odocoileus virginianus. These roving ruminants have made themselves a frequent sight on campus, and the surrounding Natty Lands. While walking through our forest, I used to find myself thinking that, back in the day, I might have been mauled by a wolf or a bear. In reality, large animals would have been an unusual sight, due to the large amount of land that they require. We often lose sight of this when thinking about our herd of deer, with their big ol’ eyes, silly fauns and charming shyness, but the truth is these sugar-plumb pixies are hiding a dark secret.

St. Olaf’s Natural Lands cover 430 acres–more than half a square mile. This land is home to around 20 deer. This might not seem like a lot, but the carrying capacity of a population of deer is not always what you’d expect. Carrying capacity is not only determined by land space, but by access to edible plants, diseases, competitors, and predators. If the conditions of a large area of land are not helpful to deer, then the numbers of deer in that area will be lower than what you may expect such a big place to carry.

Even if a place is suitable for white-tailed deer, it may not remain so for long! White- taileds produce some of the highest numbers of offspring of any deer, with does being able to

birth around 30 fawns over their lifespans. Deer are voracious hunters … of plants. Without a controlling force to counterbalance them, deer can decimate vegetation, like they did in Yellowstone before the reintroduction of wolves. But the deer will get their comeuppance through the specter of hunger. With high rates of overpopulation, most white-tailed deer herds are undernourished. In cases of overpopulation, deer will slowly starve after eating all of their resources.

Despite being associated with forests, white-tailed deer actually like transitional areas between forest and prairie. The 19th and 20th century destruction of most open grasslands forced this tenacious species to adapt to the forests. Nevertheless, smaller deer species–like white-tails– like forest edges. What this means is that habitat fragmentation is actually beneficial to white- tails because it creates more edge habitats. Another reason that habitat fragmentation benefits white-tailed deer is that land development has replaced almost all of the prairies with huge fields of nutritious crops. The desire for more productive agriculture has also led to the extirpation of all predators–like wolves–which could put a dent in white-tail populations.

Could St. Olaf accommodate wolves (Canis lupus) on our lands? Definitely not! Even a small pack requires hundreds of square miles. The much less demanding coyote, aka Canis latrans, requires a territorial range between a few to 40 miles. The red fox, Vulpes vulpes, can hold territories of comparable size in certain habitats, but only need a minimum of two to five miles. Both of these canids roam widely through their dominions, and are also frequent sites around here. So could they control the deer? Probably not. While coyotes do snack on deer, they can also go after a range of other prey. As for foxes, they could actually make things worse.

Foxes prefer to dine on mice, voles, and rabbits–all of which feast upon the grasses which the

deer love. Other, smaller herbivores can affect the amount of protein that deer have access to. So

by ravenously devouring the bun-buns and mousies, foxes and other predators like weasels indirectly raise the number of deer an area can potentially support. As a not-so-fun fact; those cute weasels you may see take down rabbits several times their size!

And even if the deer can’t stay in the natural lands full time, they can just retreat to their hidden-in-plain-site hideout: the town. The restrictions on the use of firearms in suburban areas creates a refuge for the deer. And being that deer are much less intimidating then, say, coyotes or bobcats, no one complains about them or in any way advocates for their removal.

White-tailed deer also affect the abundance of other species. For example, a study in New Jersey and Pennsylvania found that areas with high levels of deer browsing raised the local abundance of three species of non-native plants. One of these invaders is garlic mustard, which is very common in Minnesota. Greater white-tailed deer grazing also increases the amount of grazing resistant plants, such as grasses and sedges, which in turn affects the area’s biodiversity. White tailed deer grazing on forest areas could possibly also be affected by the surrounding farmland. A study in 1995 to 1996 in Southern Minnesota found that the availability of alfalfa and row crops could reduce the likelihood of deer eating plants from nearby areas of protected woodlands at certain times of the year. Thus, white-tailed deer can increase biodiversity in some cases while reducing it in others. The degree to which white-tailed deer increase or decrease biodiversity overall is complex, and is a subject of ongoing research.

Sources:

“National Trappers Association.” The Coyote. Accessed December 16, 2024. https://www.nationaltrappers.com/coyote.html

“Red Fox.” Mammal Society. Accessed December 16, 2024. https://mammal.org.uk/british-mammals/red-fox

Augustine, David J. and Jordan, Peter A. “Predictors of White-Tailed Deer Grazing Intensity in Fragmented Deciduous Forests” The Journal of Wildlife Management 62, no. 3 (July, 1998): 1076-1085. https://www.jstor.org/stable/3802560

Dewey, Tanya. “Odocoileus Virginianus (White-Tailed Deer).” Animal Diversity Web. Accessed December 16, 2024. https://animaldiversity.org/accounts/Odocoileus_virginianus/

Eschtruth, Anne K., and John J. Battles. “Acceleration of Exotic Plant Invasion in a Forested Ecosystem by a Generalist Herbivore.” Conservation Biology 23, no. 2 (March 16, 2009): 388–99. https://doi.org/10.1111/j.1523-1739.2008.01122.x

Hunter, Tex. “The Right Density – Number of Whitetail Deer per Acre of Habitat.” Texas Hunting Times: Texas Hunting News | Your Texas Hunting Guide & Online Magazine, January 12, 2023. https://texashuntingtimes.com/the-right-density-number-of-whitetail- deer/

McShea, William. “Ecology and management of white-tailed deer in a changing world.” Annals of the New York Academy of Sciences 1229, no 1 (January 23, 2012): 45-56. https://doi.org/10.1111/j.1749-6632.2011.06376.x

Rooney, Thomas P. “High White-Tailed Deer Densities Benefit Graminoids and Contribute to Biotic Homogenization of Forest Ground-Layer Vegetation.” Plant Ecology 202, no. 1 (August 20, 2008): 103–11. https://doi.org/10.1007/s11258-008-9489-8 .

Tekiela, Stan. Mammals of Minnesota (Adventure Publications, 2005), 171, 247, 261-283