"Whispering Bat" a new addition to the garden list

I was delighted to record brown long-eared bat over the garden two nights ago. This is one of the very few occasions that I have managed to actually get one to register on the bat detector. Brown long-eared bats belong to the Plecotus group of bats which are often referred to as the whispering bats because their echo location is so quiet. 

Bats evolved echo location in order to allow them to catch flying insects at night, but some moths countered this by evolving ways of hearing the bats echo locating. This gives the moth an advantage because it is forewarned. Brown long-eared bats have evolved huge "ears" which are actually more like satellite dishes which allow the bat to echo locate much more quietly and therefore evade the moths early warning system. Because they echo locate so quietly they are rarely picked up by bat detectors, in fact I believe that they have to come within 3-5m in order to register.

By coincidence the following night I recorded another bat which the detector also identified as brown long-eared but although the frequency might be in the range you can clearly see that it has the hockey stick shaped call associated with pipistrelle sp. and it is in fact the social call of a pipistrelle sp.

Brown long-eared is at least the 5th species of bat I have recorded in the garden this year, the others being common pipistrelle, soprano pipistrelle, noctule and whiskered. I'm also still getting regular recordings of what the detector thinks are Nathusius's pipistrelle and Leisler's bat but they've so far not been clear cut recordings and until I get a classic I won't be counting either of those species.

Brown long-eared bats will also glean insects off the foliage of trees at night, in particular butterflies and moths. This is a technique of hovering around leaves and picking off insects, which means that day flying insects such as butterflies are as vulnerable as nocturnal insects. The bats then often carry their prey to a night time roost which can be a cave or tree, or often an old building, where they remove the wings and eat the more edible parts, leaving the wings scattered all over the floor below. I came across just such a roost in Derbyshire in 2016.

Photo: Small tortoiseshell wings at a 
Brown long-eared bat roost.