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Most bats found in New York roost alone during daylight hours but those most often encountered by humans (big brown bats and little brown bats) roost in groups called colonies. Although most colonies of bats go unnoticed or are of no particular concern to people, when a colony takes up residence in a home or public building, the bats may become a nuisance due to their vocalization and activity, odors and stains from urine and feces, and rejected food, which may accumulate below roosting sites.


Bats are implicated in a number of human diseases, with rabies being the most widely known. Some typical symptoms of rabid bats are erratic flight, especially landing in areas or on surfaces where they would not usually be found. Also, appearing in the daytime should be regarded with suspicion. If you wake up to a bat in your house, the bat must be tested for rabies. This is done due to the fact that the bat may have come in contact with you while you were sleeping.  Histoplasmosis (a disease contracted by breathing the airborne spores in the dust of bat manure) is another health hazard regarding bats.


Bats also carry ectoparasites (parasites living outside the body), including mites, ticks, and fleas. The bat bug, which closely resembles the common bed bug, may bite humans. Bat manure attracts flies, cockroaches and other undesirable insects. These all must be considered in any bat control program.


Bats are mammals and every effort should be made to protect the species. For this reason, NPWC uses safe, humane exclusion methods to remove them. It is important not to attempt an exclusion during the period from when the young are born until they can fly.  In New York, little brown bats are born June 7 - July 10 and airborne by August 1st.  Big brown bats are born May 21 - June 7 and airborne by July 7th.  Exclusion at this time will result in the young being trapped inside where they will soon die.  While an exclusion can be done at any time after this period, ideally the best time would be in late fall (after October 31st) when the bats have migrated to caves in upstate NY and Canada.  After the bats are removed, all entry points are sealed to prevent a future infestation.  All work is guaranteed for a 10-year period against bats re-entering.

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