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Decline in bat numbers affects agriculture costs

Written by Jim Hintz for the York Daily Record | Mar 1, 2016 5:00 PM
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(Undated) -- The plight of bats has been in the news for many years, but you might not be aware of the agricultural costs associated with their decline.

Bats eat insects. One hundred and fifty little brown bats can eat over one million pest insects each year. Because so many insects carry diseases, including mosquitoes, you can easily see the value of bats. Crop and forest loss from pest damage are huge factors we don't often associate with bat decline.

If that weren't bad enough, add the extra pesticides needed to control those pests. A combined study by the University of Tennessee, Pretoria (S. Africa), and Boston University has said that bat losses could mean agricultural losses of more than 3.7 million dollars a year.

Our bats belong to the family Vespertilionidae, which is comprised of five subfamilies. The entire family is the second largest group of mammals, having about 925 species. Their common name is 'evening bats'. Eleven species have been reported in our state, two of which have only been sighted a few times.

Pennsylvania bats include the big brown bat, tri-colored bat, hoary bat, Indiana bat, little brown bat, northern long ear bat, red bat, silver-haired bat, and small-footed bat. The silver, red and hoary bats migrate south in the winter. The Indiana bat is federally endangered. All the species are important to our ecosystem and all need our help.

There is considerable variation between species, and much of the world family still has had relatively little study. Many of the species are cave dwellers. If a cave has the ideal temperature, several species may reside in the same cave.

Populations can be decimated if disturbed too often during hibernation. Scientists are also concerned about the number of bats being killed by wind turbines. They not yet sure why, but are actively searching for answers.

Although having small eyes, bats can see very well. Their small sharp teeth easily chew any insect they catch. Mating can occur in autumn or winter, but the female bat stores the sperm and doesn't become pregnant until spring when the weather gets warmer. Pregnancy will last from six to nine weeks at which time the males and females will typically stay segregated.

For some species, only one pup is born at a time, but the mother can have two or three litters during the breeding season, while other species can have one to four pups at one time but only once a year. The females are very good at manipulating the birth time so both weather and food are optimum. Bats are still considered one of the slowest reproducing animals in the world.

What can the average person do to help?

  • Install bat boxes. The best time to put up a box is late winter or early spring. Place the box where it will get roughly seven hours of sunlight. These boxes may be attractive to pregnant females who need a protective place to have and raise their young. Plans are available at extension.psu.edu under "natural resources," or at nwf.org.
  • Reduce or eliminate the use of pesticides in your yard and garden. Bats and mother birds rely on insects. Reserve insecticides for really tough problems that can't be solved by better means.
  • Plant dense areas using native flowering species, especially those flowering at night. White jasmine, evening primrose, mint and lemon balm are a few good ones.
  • DO NOT DISTURB bats during hibernation.
  • Become involved with conservation programs and pass on the knowledge.

Jim Hitz is a York County Master Gardener. Penn State Master Gardeners are volunteers for Penn State Cooperative Extension. For more information, contact the Master Gardener office at 717-840-7408.

This article is part of a content-sharing partnership between York Daily Record and WITF. 

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