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Frightful Ally
| Article
# : |
20013 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
8 / 1992 |
1,816 Words |
| Author
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Branley Allan Branson
Branley Allan Branson is professor of biology emeritus at
Eastern Kentucky University and editor of the Transactions of
the Kentucky Academy of Science. |
No American snakes are more generally feared and hated than the rattlesnakes, even though most Americans have no basis for such antipathy. This aversion is unfortunate and misdirected since rattlesnakes play an important role in nature. Rattlesnakes feed heavily upon rodents, including many destructive rats, mice, ground squirrels, and prairie dogs, occasionally augmenting their diet with birds and lizards. Field investigations demonstrate that between 85 and 95 percent of the rattlesnake diet consists of rodents, which the snakes take by ambush. Adult rattlesnakes feed every 10 to 16 days during their active season (about seven months each year), eating about twice their body weight in rodents. Complete digestion of the prey takes anywhere from 5 to 8 days depending upon ambient temperatures, and most of that time is spent in hiding.
Although exact population sizes of rattlesnakes are difficult to ascertain because of their secretive habits, nocturnal activities, and the amount of physical labor involved, good estimates put their numbers between 1 and 2 snakes per acre, sometimes 60 to 65 per square mile, depending upon adequate habitat and available food supplies. In many sections of North America, rattlesnakes are more common than other, nonpoisonous species. In the forests of the eastern United States, the timber rattler makes up about 30 percent of the total snake fauna, whereas in the shrubby ranch country of Utah rattlesnakes comprise about 40 percent of the total, and in certain desert areas rattlesnakes make up over 75 percent of the snake fauna. The prairie rattlesnake is the most common snake in South Dakota.
It is known that rattlesnakes appear to have cyclical abundance, mostly correlated with increases or decreases in food supply. Thus, the importance of rattlesnakes in nature is correlated with their relative abundance and the number of rodents they eat, tending to hold down the innate tendency of rodents to overpopulate their range. Considering the fact that a single large rodent can cause up to $20 worth of damage per year on farms and ranches, rattlesnakes also have a great economic importance besides a natural one. In spite of that fact, however, people continue to fear and despise them.
In truth, few people actually encounter these essentially nocturnal, secretive creatures, even in places where they are relatively common. The general publics as such is largely quite ignorant about the biology, distribution, and kinds of rattlesnakes that live in the United States. Throughout their range, which includes southern Canada, the United States, Mexico, some islands off Baja California, and Central and
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