The Nature Writers of Texas

The best nature writing from the newspaper, magazine, blog and book authors of the Lone Star State . . .

Thursday, May 28, 2009

How Do Our Drought Conditions Affect Our Wildlife?
by Ro Wauer

Many of our wild animals have a very difficult time during drought conditions. Most are depended on available waterholes and/or birdbaths. Exceptions include a few lizards and small rodents. For those of us that provide plenty available water in our own yards, we cannot help notice the increased use of those artificial waterholes. But for wildlife species without access to such water, they may take one of several actions. Those species that are extremely mobile, such as some birds, they move out of the area altogether. Some other species may be able to move short distances to where they can find water. Our many rivers in Central Texas may act as sponges for those that are able to get that far.

Drought conditions can and often does lead to the death of some wildlife species. When water is not available, wildlife often goes into a sort of depression. Birds may react by being less aggressive on their territories, they may sing only part of the normal time, and they become less active in general. Those that do manage to nest often produce less than a normal clutch, and the fledglings, too, may be less healthy. Birds often are able to do pretty well during the nesting season if they are able to find adequate food to feeding the nestlings. The majority of their diet that time of year is insects that in turn are more often than not dependent upon vegetation. Severe drought conditions, of course, can greatly limit the available insects.

What about the mammals? They too must adapt to abnormal conditions. They may be less aggressive and spent the majority of their time finding food, oftentimes in locations where they might not utilize at other times. For instance, deer will spend more time grazing along roadsides where additional moisture from the roadways tends to support roadside grasses. And some of the mammals that normally are active only at night may need to spend more daylight hours in search for food. Drought conditions also produce other behavioral changes. Some species, such as some rodents, can go into a semi-hibernation mode.

Reptiles and amphibians also become less active in drought conditions. Many of these individuals seek shelter below ground and can aestivate for long periods of time. Like rodents, their metabolism can decline to a point that they are barely alive.

Butterflies are also greatly affected by arid condition. But unlike most mammals and birds, they are able to hibernate (known as diapause) and wait for a change in weather conditions. Although many butterfly species possess a life cycle of a year or less, they are able to diapause for several years. Some species diapause as larvae and can remain in that stage for five to seven years. And those individuals normally will require some significant change, such as heavy and constant rainy conditions, for them to move into the next stage in their life cycle.

Butterfly populations in South Texas are currently very low, when both species and numbers are far below normal. My garden, that will produce 25 to 35 species on a “normal” day in May, has recently only produced 10 to 20 species per day, and only a fraction of the normal numbers. And that number is as high as it is because of the constant watering of the many flowering plants that attract butterflies. Outside the watered garden, the fields and roadsides, even though recent sprinkles have finally produced an assortment of wildflowers, butterfly numbers have not adequately recovered. It will take considerable more moisture before butterfly populations return to normal.

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