Bats are mammals. There are 17 resident bat species in the British Isles with 10 of that number occurring in Essex. Norsey Wood has at least 4 bat species but recent research may suggest that there are more to discover. Needless to say, they are a difficult group to study owing to their nocturnal way of life. The usual species that are detected within the Wood are Common Pipistrelles and Soprano Pipistrelles. A Brown Long-eared Bat has been recorded and is probably more common in the Wood than we realize. Noctule Bats (our largest bat species in the British Isles) have been seen flying high over Forty Acre Plantation to the immediate NE of Norsey Wood so they surely occur. It is likely that the Serotine Bat occasionally occurs but is not proven. Were there larger water bodies within or near the Wood then the species range would be greater. The combination of trees and water act as a magnet for insects and thus those that feed upon them.

Pipistrelles are known to live for at least 16 years of age whereas the larger species of bats can live for considerably longer. For such a small mammal, this is a surprisingly long time. This fact has not been scientifically explained but some researchers suggest the answer lay in the fact that whilst in hibernation, a pipistrelle’s heartbeat may slow down to c.25 beats a minute but when actively flying in the summer it rises to c.1000 beats a minute. Horizontal flight speed for the smaller bat species is about 18mph and for the larger species as much as 30mph but considerably more when dropping out of the sky on an insect prey below! The weight of a healthy pipistrelle bat is c.3 to 7grms and for a Noctule Bat 21 to 30grms.

Recently, an exciting project in the Wood has been the periodic installation of several batlogger recording devices (partly funded by the NWS membership) and early indications are promising. Although confirmation is required there could be more bat species within the Wood than previously realized. Work in progress.

There is a large Soprano Bat maternity roost in a house not that far from the Wood and in July, when the young are on the wing, the roost count can exceed c.700 (seven hundred!). But we are not aware of a nearby Common Pipistrelle maternity roost.