The name of the Bat with Big Ears is an understatement: the ears are huge almost as long as the rest of the body and they play a vital role in the detection of prey. Of all the British bats, the long-eared is the most distinctive. No other mammal has ears that are nearly as long as its body.
In fact, the ears of the long-eared bat are so big that they can often be seen even when it is in flight making identification easy. With its long, soft fur, large eyes, and delicate wings, it is a quite attractive mammal with inoffensive habits.
A Bat with Big Ears finds its way about in the dark by means of echolocation. It emits high-intensity, ultrasonic sounds (too high-pitched for us to hear). Which are reflected from objects in its path? From the patterns of the remaining echoes, the bat can interpret its surroundings and avoid flying into obstacles.
The same mechanism is used to catch insect prey. Echoes bounce off even the smallest midge and alert the bat to the presence of a potential meal. All British bats are capable of intercepting flying insects in this way and probably compete for similar prey. But this leaves a whole range of suitable food items untouched insects, caterpillars, and spiders.
Which do not fly but crawl about among tree-top vegetation instead? Most bats fly too fast to notice these creatures, and in any case probably cannot differentiate between the echo of, say, a caterpillar and the leaf on which it is resting.
This is where the long-eared bat comes into its own. Instead of emitting loud echolocation sounds which just bounce off foliage indiscriminately, this bat whispers. Its ultrasonic noises are so quiet and sensitive that it can tell the difference between an echo from an insect and what it is sitting on. The huge ears detect these minute echoes, and also
The Bat with Long Ears is a nocturnal mammal, foraging by night. In-flight the sensitive ears are held erect, directed forwards so they can detect insect prey by echolocation. When the bat is at rest or crawling about, the ears crinkle along their outer edges and are then lowered over the shoulders.
There are two long-eared bats in Britain, the common and the grey. The grey (Plecotus austriacus) is very difficult to distinguish from the common and there are no external features that provide positive identification of every specimen.
Generally speaking, the grey long-eared bat has darker fur than the common, which is browner. The presence of the grey was overlooked in Britain until 1963, and even now little is known about it. So far it has been identified only in southern England, though it may be more widespread.
Distinguish between sounds reflected from different textures, such as a soft insect larva and a smooth leaf. The sounds are made and the echoes interpreted in a split second during the flight a remarkable feat since it involves only part of the bat’s brain, the whole of which is smaller than a pea.
The task of catching insects is made easier for the long-eared bat by its ability to hover at an angle of 300. The long-eared bat can pick food delicately and precisely off foliage and bark, and perhaps even from the ground. As well as the usual flying insects, its diet, therefore, includes a whole range of invertebrates gleaned from trees that other bats do not manage to exploit.
In late summer especially, the Bat with Long Ears takes large numbers of noctuid moths, snapped up on the wing, and carried off to a convenient perch to be dismembered and eaten. Usually, the moth wings and legs are discarded, and a little heap of such litter accumulates below the perch.
The Bat with Long Ears’ habit of using feeding roosts near human habitation, and its ability to hover and fly in confined spaces make it likely to be one of the species that flies into bedrooms at night through open windows. It is difficult to be more precise since few people favored such a visit stop to check the identity of the intruder.
The Bat with Long Ears mostly roosts in attics. Groups of up to two dozen females gather in attics in summer to bear their young. They are usually so quiet that they easily pass unnoticed by the householder, and can raise their young undisturbed. Attics make good bat nurseries because they are warm. Higher temperatures mean faster growth and development for the young.
On cool days the bats huddle together to warm their offspring. Such a colony does no harm and may help to keep the roof space clear of moths, spiders, and destructive beetles. The young are born in June and July. Each female never has more than one baby a year and none at all in some years. The population thus increases only slowly. When a colony is wiped out it may take a decade to recoup.
A low breeding rate is characteristic of bats probably because their babies are so big. Each weighs nearly a third as much as its mother at birth. Under natural conditions, bats do not need to produce large numbers of offspring as they have few predators to fear. The long-eared, For example, is occasionally taken by owls and cats but is otherwise safe except for destruction by humans.
Adult males do not usually roost with nursing females, and take no part in rearing the young. They meet up with the females again once the young have been weaned and the nursery colony has dispersed for the winter.
Three-month hibernation like other insectivorous animals, the long-eared bat faces a critical shortage of food once the colder nights of autumn begin. Two options are open to it. Either they fly south to warmer places, or stay put and drastically reduce energy requirements by hibernating.
It seems that Bat with Long Ears normally hibernate, often staying close to where they have spent the summer months. They usually hibernate in trees and buildings; though sometimes use caves, mines, and other similarly cool places. Their preferred hibernating temperature is probably about 0°C (32°F).
Bat with Long Ears would be forced into unnecessary and unwelcome activity if they hibernated. Somewhere that became too warm on sunny winter days. Winter activity is undesirable because there is little chance of recouping the fat reserves used to provide energy for flight.
If the bat finds a suitable place, it may well hibernate for over three months. During hibernation, the large ears pose a problem. Precarious moisture may evaporate from their large surface and, even when this difficulty is avoided by the choice of a cool, humid place to pass the winter, they a vulnerable to frostbite.
The ears could get in the way if the hat wanted to crawl into a more sheltered crevice, so the problem is solved by folding the ears backward. Hibernation ends in March in the south of England, probably later in the north though this varies with the prevailing weather.
Mating takes place soon after hibernation ends or perhaps earlier during periods of wakefulness in winter. When they wake up the hats start feeding to recoup the .2O or more of lost weight.
Long-eared bats become active within the day and roost at about sunset every night. They are emerging from the nooks and crannies where they have passed the day. They may spend up to an hour or so making short flights and grooming their silky fur. If the long fine fur becomes matted, it loses its insulation, stream-lining, and rain-proofing properties. Once it is fully dark the hats go out to forage.
Sometimes they stay out all night at other times especially if there is plenty of food. If there are babies to be fed they may return within the hour. Perhaps they are making another sortie later.
Long-eared bats normally manage to find all the food they need without having to fly far from home. Occasionally, some Bat with Long Ears hats appears to make extensive journeys out to sea.
They have turned up among night-migrating birds attracted to offshore lighthouses, in 1%8 one was found dead on a lightship in the North Sea, 31 miles out from Great Yarmouth.