Tuesday, June 1, 2010

Going Batty!

Bats can’t seem to catch a break. Just as soon as more people find out how helpful they are, another vampire movie comes out and terrifies a whole new audience.

The truth is, only three of more than 900 species of bats feed on the blood of other animals.

Many others feed on crop pests. Bats are important worldwide for their role in plant pollination, insect control, and dispersal of seeds. They are especially helpful in controlling crop pests; some bats eat 600 mosquito sized insects in an hour.

But 40 percent of American bat species are in severe decline because of habitat loss. Reasons include loss of roosting habitat because of cave and mine closings, intentional habitat destruction, development and deforestation, and loss of trees, snags and hedgerows from farmlands. Here are the basic bat habitat needs.

Food preferences. Insect-eating bats feed primarily on night-flying insects such as moths, beetles, fruit flies, mosquitoes, and mayflies. They can consume half their body weight each night in insects-- some species eat grasshoppers and cicadas. Fruit-eating bats eat fruit, pollen or nectar from plants and flowers as they pollinate such plants as bananas, mangoes, dates, figs, peaches, cashews and avocados.

Roosting cover. Being nocturnal, bats roost during the day in tree branches and leaves, under tree bark, in caves and mines, under bridges, in cliff crevices and natural tree cavities, and in attics and roofs of barns. Roosts may be for nursery colonies of females and their young; lower temperature bachelor roosts; and migratory stopover roosts.

Foraging needs. Most common foraging habitat is woodlot canopies and understory, over streams and other open water, open fields and croplands, and in lighted residential areas with large insect populations.
Bats skim water to drink from the surface while in flight.

Hibernation. Caves and abandoned mines are the largest hibernating habitat. That’s why totally sealed mine closings can hurt bat populations. Some bats hibernate in tree cavities, tree bark crevices, and buildings.

All the habitat components-- roosting, food, water, foraging and hibernation habitat, are needed in relative proximity to each other. For some bat species, humans can help with roosting facilities. Brown bats will use bat boxes constructed for them, but they need to be constructed and sited properly.

Attach the bat box at least ten feet high to a building or pole. Orient box to southeast to catch the morning sun if possible. If not possible, orient between the southeast and southwest to get at least seven hours of direct sun. When evicting bats from a building, place box near existing entrances, preferably a year prior to eviction. Do not evict bats between May and end of July when flightless young may be trapped inside. If more capacity is needed, additional boxes can be placed side by side.

If wasps become a problem, use a long thin stick to scrape old nests out in the winter. New nests can be knocked out in May or early June, during cold mornings or evenings, when wasps are less aggressive. If bats are present, don't disturb. Bats and wasps can coexist in boxes. Bats provide travel lanes for wasps to reach their nests. Wasps, in turn, provide some protection against box disturbance.

Here are plans from the WI DNR,  or the district also has attractive, properly designed boxes made from long-lasting cedar available for purchase.

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