Folding of the Ears of a Long Eared Bat (Plecotus auritus)

FOLDING OF THE EARS OF A LONG EARED BAT (PLECOTUS AURITUS). b y T H E EARL OF CRANBROOK.

A long-eared bat when in flight holds its ears extended to their f체ll length of about 35 mm. When at rest or eating the ears are relaxed, the outer edge crinkling up like a concertina in a series of tranverse wrinkles, the inner edge curving over and outwards so that the whole effect is rather like a ram's horns. When asleep or hibernating the ears are folded longitudinally, stretched out almost to their f체ll length and tucked away under the wings parallel with the forearms, the tragi still pointing downwards and giving the appearance of long narrow pointed ears. Changes from the " ram's horn " to the erect position and vice versa are easily and frequently observed. In the first case the whole ear stiffens up, the transverse wrinkles on the outer side disappear and the inner edge straightens out like a bent twig returning to its original position : in the second the ear seems to collapse outwards as if by the relaxation of muscular tension or loss of an original turgidity. In neither case is there any longitudinal folding while the extended ears are always held pointing forwards to a greater or lesser degree and never to the rear along the back or sides as they would have to be if they were tucked under the wing in the extended position and then folded longitudinally.

Looked at from behind hanging in a box or on the side of a cave or wall the forearms and ears of a sleeping or hibernating bat are hidden by the f체r and Observation of the method used to fold away the ears is impossible. A long eared bat was therefore kept in a box the rear wall of which was made of a sheet of glass with a series of horizontal wires 5 mm. apart fixed inside. The bat could thus be observed from the ventral side as it settled down to sleep, when both ears and forearms were easily seen. In the event in a warm room the bat seemed often to sleep without tucking away its ears and since, as it was ultimately found, the operation takes but a fraction of a second, many hours of fruitless watching were wasted. The bat after feeding climbed the wires head uppermost, turned upside down, and hung suspended by the claws of the hind feet. The ears at first would be in the extended position, pointing downwards, but would soon relax, the lower distal portion curling outwards into the " ram's horn " position. At this stage the upper, basal part of the ears would still be pointing more or less downwards, each at an angle of about 20째 to a vertical line drawn down the centre of the bat's back between the ears. Gradually the angle between the ears would widen, though closing a little at intervals to widen again, the outer portion still in the ram's horn position until the base

FOLDING EARS OF A BAT

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of each ear was held outwards and well above the horizontal, the previously outer but now inner part of the ram's horn against the body. Finally one of the forearms would very quickly move outside the ear and come back pressing it, still in the ram's horn position, crumpled against the side of the body and under the wing.

After that with occasional twitches of the bat's body and forearm the ear would gradually extend to its fĂźll length, folded longitudinally and held between wing and body.

BIRTH OF A SEROTINE BAT (.EPTESICUS SEROTINUS, Schreber.)

IN CAPTIVITY. by

T H E EARL OF CRANBROOK.

A female serotine captured on May 26th, 1960, was kept in eaptivity in a glass sided aquarium one wall of which had J" wire netting on the inside, on which she hung and slept. Food and water in small shallow dishes were on the floor and she learned within two days to feed from the dish. She was fed on meal Worms, blow fly pupae and house crickets. The last were killed by crushing their heads and the freshly killed bodies were left