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How Do I Assess Habitat Quality?
Like every other animal, deer need food, water, and cover to survive. Forests that provide these in abundance are good deer habitat and can support many deer before their own health is threatened. Forests with poor soils and few plants on the forest floor are poor deer habitat, and relatively small numbers of deer can further reduce habitat quality. What should you look for to assess the habitat quality of the forests you visit?
Low-growing plants
Look down in the forest. A white-tailed deer needs to find 4-10 pounds of edible plant growth each day that’s within their reach – that is, up to about 5 feet from the forest floor (hyperlink to Tim’s curriculum).
- Do you see lots of tender tips of small trees, shrubs, or abundant wildflowers? The greater the amount of food available, the better the habitat. Sometimes plants are absent because there’s too much shade, or seed production is low. Sometimes they’re absent because deer ate them, but in either case, a forest with little food makes poor habitat.
- Are there many different kinds of plants? Deer prefer variety. When almost all the plants seem to be the same, it might be because deer don’t care for that species. In Pennsylvania, for example, deer don’t eat fern, and so forests with nothing but fern within the reach of deer (picture) (hyperlink) are very poor habitat. In Wisconsin, sugar maple may be the only seedling in mixed woodlots (picture, hyperlink) because deer don’t prefer it. Low plant variety can also be caused by limited seed source, or invasion of an exotic invasive plant like garlic mustard.
- Learn the plants that deer prefer in your forest (hyperlink) and look for them. If they’re abundant, it’s a sign of good habitat; if they’re missing, it’s poor habitat. It also helps to know the less preferred plants, and to know the exotic invasives that might infest your forest
- If you find a sunny spot in the forest, are the plants growing there taller than elsewhere? When plant height is the same across the forest, even where light or species is different, it might be due to deer. Look for evidence of deer eating, or browsing, on understory plants (picture(s)). When hungry deer are keeping all plants mowed to the same height, the habitat is becoming poorer as a result of browsing.
Food in the neighborhood
Deer usually use a territory of one square mile or less (this varies by region and by sex – buck territories tend to be larger than those for does), so be sure to think about this whole neighborhood when you’re thinking about habitat quality. Are there fields, farms or landscape plantings nearby? Does the forest include patches with many small trees, saplings, or seedlings within the reach of deer? Forests with other food in the neighborhood are better habitat than stretches of unbroken forest.
Cover
Especially in the northern part of our region, deer seek cover in the winter in dense evergreen cover, to protect them from the wind and snow. In spring, fawns survive better if forests have patches of dense undergrowth in which they can hide from predators while their mothers feed. Both of these cover conditions are more likely to exist where deer densities are low relative to the K carrying capacity of the habitat. A recent study in Pennsylvania examined bear predation on fawns. In habitat where a legacy of deer overabundance had created open understories with high visibility, such as dense low fern cover, bears were a much more important cause of fawn mortality than they were in habitats with complex and varied understories and low visibility.
One of the resources on this site is a curriculum for a one-day course that teaches a method for assessing habitat quality and deer impact in the forest.
Other resources related to this topic
deCalesta, D.S.; Stout, S.L. 1997. Relative deer density and sustainability: a conceptual framework for integrating deer management with ecosystem management. Wildlife Society Bulletin 25(2): 252-258.