Species of the Month - October
Each month we feature a picture of a species to be found on The Commons. Wherever possible, all species featured have been photographed here, but that was not possible for this item. There are 17 species of bats known to breed in the UK; of these at least 11 have been recorded in Norfolk with 8 species on or near Southrepps Common.
Unless you make a habit of walking around at dusk, bats would not immediately spring to mind at this time of year. However, it is a busy time for them. By now the young that were born in the summer are weaned and individuals are concentrating on feeding up to gain fat reserves to support them during periods of inactivity over the winter. This is usually called hibernation, but is more correctly called torpor.
Autumn is also the time when there is a lot of social interaction and mating. Males produce calls to attract a mate, either whist flying, or from a crevice in a tree or building. Unlike most bat calls, which require special equipment to hear them, these calls can sometimes be low enough to be audible by the human ear. Mating can take place in autumn as females are able to delay pregnancy until the following spring, with a single young, called a pup, being born in early summer.
Usually the first to be seen in the evening are the Pipistrelles (the smallest UK bats), of which there are three species: Common, Soprano and Nathusius', but these can only distinguished by their different calls, using a bat detector. Noctule bats also emerge quite early in the evening. They are one of the larger species and fly more slowly and quite high overhead. Brown long eared bats are much harder to see and hear, fluttering in the canopy of trees gleaning insects from leaves. Another species often associated with woodland is the Barbastelle bat, which although nationally quite uncommon has been found regularly in this part of Norfolk. Two other species; Natterer's and Daubenton's bats, tend to fly later in the evening, the latter often associating with water where it feeds by scooping insects from the water surface with its large feet.
The bats will be with us while the warmer weather lasts and have been known to fly with outside temperatures below 10 Deg. C. But as we move into late October and November with sustained periods of colder weather they will all move to hibernation sites deep in trees, cool buildings such as ice houses and other structures. Here, with stable temperatures of 3 – 8 Deg. C they will slow their heart rate and other metabolic functions waiting for the warmer weather of spring.
More pictures and information about bats can be found on the website of the Bat Conservation Trust.
Click here to see the other Species of the month in 2018.