 |
The Effects of Drought on Wildlife
By Griff Morgan, Biological Science Technician, Bankhead National Forest (now at Conecuh National Forest)
 |
I have an unofficial wildlife study that I’ve been conducting on an ongoing basis for several years now. It goes like this. Every morning I make a mental note of what sort of critters have met their demise the night before on the sixteen miles of Highway 195 between my house and work. At that hour the crows and vultures have not yet had an opportunity to make their rounds and the evidence is untampered with! As time goes on, I try to detect a trend in what I’m seeing (more of these, fewer of those). If I notice what I believe to be a trend, I try to think of an explanation for it. Hey, I know it’s a morbid way to spend my time, but there’s nothing interesting on the radio at that time of day, and besides I’ll bet a lot of you do the same thing!
| By now you’re thinking, “What do road kills
have to do with drought?” Well, for the last three months or
so I’ve seen more raccoons on the blacktop than I’ve ever
noticed before. I suspected that the record drought we experienced
this summer had dried up the streams where they forage for food and
that they had been seeking greener (make that wetter) pastures. I
posed my theory to Ron Eakes, wildlife biologist for the Black Warrior
Game Management Area, which led to a rather lengthy discussion of
how drought affects wildlife. According to Ron, a shortage of mast may also be to blame for the surplus of raccoons I’ve been seeing. The hard mast crop in our area is particularly scarce this year due, in part, to the lack of rainfall. On those trees that did bear, the acorns are small and malformed suggesting a lack of water during development. As if that weren’t enough, the soft mast hasn’t been anything to brag about either. Important food sources like sumac, possum grapes, and muscadines have been spotty. Being omnivorous, a large part of a raccoon’s diet in the fall is mast and they are, no doubt, crossing many highways to try and find what they can. All terrestrial animal species, including we humans, exist by consuming plant products (leaves, seeds, nuts, etc.), or other animals, or some combination of the two. Water is an essential part of the process that produces vegetative growth, including the production of fruit or seeds. It follows that a protracted shortage of rainfall during the growing season will cause a shortage of food somewhere down the line. Unlike we Americans, who can just trot on down to the grocery or drive-thru at mealtime, most animals must do with whatever is available or do without. |
|
Consequently, most species have developed strategies for dealing with fluctuations in the available food supply. Rodents tend to store nuts and seeds, larger animals like deer or bear eat all they can and store fat. These fat reserves help them survive through the winter and early spring when food is scarce. It is this latter method of survival combined with this year’s shortage of mast that could spell trouble for some animals. Some individuals (deer in particular) going into the winter with low body weight would have a much tougher time surviving if weather conditions turn unexpectedly bitter in the spring.
If we were only talking about a few select critters like raccoons, or deer, or turkey, the effects of drought would be fairly predictable. But the term “wildlife” is extremely broad and encompasses hundreds, if not thousands, of species. So the effects of a prolonged shortage of rainfall can be as varied as the degree to which each is dependent upon water. For an aquatic species like a crawfish or mussel that lacks the mobility to relocate to a more favorable environment, a dried up streambed may be a death sentence. Conversely, to a predator like a hawk or bobcat, a drought can create a windfall of opportunities because it forces prey species to move around more in search of something to eat making them more susceptible to capture.
Before you begin to worry that this summer’s drought is going to cause us to run out of raccoons or deer or whatever, keep in mind that dry spells are nothing new here in Alabama. I don’t have the record book handy right now but I would be willing to bet that old timers could tell you about drought that would make this one look easy. And yet, we still have some of the most diverse ecosystems in the country! In fact, short-term weather disturbances like droughts, storms, etc. can improve the overall vitality of a species by “weeding out” its weaker individuals.
What concerns me more than the immediate effects of this year’s drought is what next year may be like, and the year after. If we are, as many predict, moving toward a time when such weather is the norm rather than the exception then we may eventually see the loss of species brought on by the loss of their habitat. Regardless of what you may believe the cause to be, there is no denying that the summers seem to be getting hotter and drier – mast for thought!