Bats of the United States and Canada

Benefits of Insectivorous Bats

recto runninghead 17 Benefits of Insectivorous Bats Nearly all species of bats in the United States and Canada, and 70% of species worldwide, feed almost exclusively on insects and are thus extremely beneficial to humans. In fact, bats are the only major predators of night-flying insects. Although bats typically eat more than 50% of their body weight in insects each night, a nursing female may consume enough prey nightly to equal her own body weight, as many as 4,500 or more small insects. Thus, a summer colony of 1,000 bats weighing 10 grams (0.35 ounce) each could consume 10 kilograms (22 pounds) of insects each night, or as many as 4,500,000 insects. As an example, people in the Chattanooga, Tennessee, area benefit by having over 100,000 kilograms (more than 110 tons) of insects removed from their area yearly by a maternity colony of 100,000 gray bats, Myotis grisescens, that spend the summer in a cave near the city. Imagine 220 This small cave in northern Alabama contains one of the largest summer colonies of endangered gray bats (Myotis grisescens). Chain-link fencing and signs prohibit passage of people into the cave. On summer evenings, exiting bats often draw large crowds of boating enthusiasts; unfortunately, some people shine spotlights into the cave, stopping the outflow of bats. Troy L. Best 18 bats of the united states and canada half-ton pickup trucks loaded to capacity with insects; that’s a whole lot of bugs. Most residents of the area probably are unaware of the presence of their furry flying friends and how they benefit from the bats. Bats serve as natural insecticides throughout the world. The amount of insects consumed by the hundreds of millions of bats is staggering. The 20 million or more Mexican free-tailed bats, Tadarida brasiliensis mexicana, that migrate north from Mexico and raise their young during summer in Bracken Cave near San Antonio, Texas, consume an estimated 182,000 kilograms (more than 400,000 pounds) of insects nightly. Imagine again—400 half-ton pickup trucks filled with insects—each night. The nightly dispersal of more than 100 million Mexican free-tailed bats from caves and bridges in south-central Texas has been observed by National Weather Service NEXRAD Doppler radar. Using the radar data, researchers discovered that the nightly dispersal of bats paralleled the time and spacing of large emergences of the cotton bollworm moth, one of the most destructive insect pests of the southwestern United States and northern Mexico. Mexican free-tailed bats congregate in huge numbers at altitudes between 180 and 1,000 meters (about 590–3,300 feet), and even as high as 3,000 meters (about 9,800 feet), and consume vast numbers of these moths. Mexican free-tailed bats also consume quantities of many other destructive insect pests, such as the corn earworm moth. Bracken Cave in southern Texas contains one of the largest colonies of bats in the world. At least 20 million Mexican free-tailed bats (Tadarida brasiliensis mexicana) migrate from Mexico and Central America to raise their young here in summer. Bat Conservation International purchased this cave to protect the bats. Troy L. Best ...