Bat Diets

One of the most dramatic measures of the diversity of bats is the variety of food they consume.Although some 600 species eat insects as the main dietary staple,others live on fruit,nectar and pollen,fish, frogs,birds,small mammals,blood,and even other bats.Most of this diversity occurs in the tropics,although many bats from temperate regions vary their diets by eating a wide range of insects.

What any bat eats is determined by two important factors:the need for enough energy to keep the body going and the need for essential chemicals to maintain it.Just as an automobile requires fuel to move and lubricants to keep the engine running smoothly,animals require protein,carbohydrates,or fat for energy along with vitamins and minerals to stay healthy.Since it is essential for bats to consume enough calories to make flight,reproduction,growth,and other bodily functions possible,it is easy to see why such variety is necessary in their diets.Species that feed mainly on plant products require protein, which can be obtained by eating animals (insects),pollen (which provides only moderate amounts of protein),or large quantities of fruit (a very limited source of protein).Bats feeding on insects appear to obtain a balanced diet from this source of nutrition.

To obtain the energy and chemicals they need,bats consume vast quantities of food.Small insectivorous species (species that eat mainly insects)eat at least 30 percent of their body weight each night they are active,and in nursing mothers the amount may exceed 50 percent.These figures appear to apply to all bats,regardless of diet. It may not be impressive to learn that a little brown bat eats three grams of insects on a summer night,but to find 150 mosquitoes in its stomach certainly is,especially when you realize they are not an entire night’s ration and the bat probably caught them in less than fifteen minutes.The most impressive statistic of insect consumption comes from Texas,where it is estimated that a local population of Mexican free-tailed bats eats slightly more than 6,000 tons of insects each summer.

The basic design of a bat imposes certain restrictions on the range of food available to it.Bats determine the direction and distance of objects in their environment by emitting high-pitched sounds and interpreting their echoes to find their location-the term for this is echolocation.Because they can echolocate,New World leaf-nosed bats that feed mainly on fruit are able to catch insects to supplement their diet with protein.Flying foxes (a species of bat found mainly in Indonesia and Malaysia)and their relatives,however,do not echolocate and must obtain their protein from something other than insects.Recent studies in the lvory Coast by the Canadian biologist Donald Thomas suggest that several species of the herbivorous bat family pteropodidae get their protein from the fruit that composes the main part of their diet.The levels of protein in the fruit are low,but this is countered by the consumption of large quantities of fruit and by enzymes in the digestive tract that efficiently extract what little protein is available.Size is also a factor in determining the diet of a bat;a 3- gram butterfly bat has fewer prey species from which to choose than a 40-gram,large slit-faced bat.As a rule,smaller bats are almost entirely insectivorous,and larger species include larger prey in their diet,readily switching to small vertebrates such as fish,birds,and frogs.The smallest bats that feed on plant material are nectar-and pollen-feeders.Larger species more often feed on fruit but may also supplement their diet with nectar and pollen.

The food selected by bats also depends on where they feed. Flying bats chasing flying insects will not catch scorpions that do not fly,but they often snatch spiders ballooning on pieces of web.Bats feeding on stationary or terrestrial prey often catch resting insects that are able to fly.Bats concentrating their feeding activity over water catch more aquatic insects than those feeding high over the forest, and species hunting over water have opportunities to catch fish not available to high-flying species that visit the water only to drink.?

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?One of the most dramatic measures of the diversity of bats is the variety of food they consume.Although some 600 species eat insects as the main dietary staple,others live on fruit,nectar and pollen,fish, frogs,birds,small mammals,blood,and even other bats.Most of this diversity occurs in the tropics,although many bats from temperate regions vary their diets by eating a wide range of insects.

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