Birth of a Serotine Bat (Eptesicus serotinus, Schreber) in Captivity

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

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BIRTH OF A SEROTINE BAT

in the dish for her to eat. The same method can be used with grasshoppers, beetles, moths, etc. Though soon becoming tarne enough to be handled without biting she was always nervous.

If a hand was put suddenly into her box while she was hanging on the side she would drop to the ground and squat, looking upwards with bared teeth at the approaching danger, and though she fecl happily in my hand when we were alone she was always worried at the presence of strangers. Sometimes she gave out a high pitched buzz like a bee, which was accompanied by a strong Vibration in her body. This would be made at intervals when she was lying quietly in the hand, unlike the " ticking " noise made by other vespertilionid bats which is only heard when they are struggling to take flight.

On July Ist she gave birth to a single male child which when first seen was tucked under the mother's wing making an obvious protuberance in the wing membrane between her forearm and body when seen from the back, as is usual with bats. When first born it was pink and naked underneath, dark on back, head and wings. The wart-like outgrowth under the chin was very obvious.

From the first when the mother moved about her box, head downwards and supported by hind feet and thumbs, the baby's small feet could be seen shifting from foothold to foothold between the mother's as they moved, while he held on to a teat with his teeth.

When they slept both were cold as is usual with sleeping bats whose body temperature then falls to that of the air around them.

For the first three days the baby was kept under her wing and she carried him with her when she climbed down to feed and drink.

Thereafter she left him hanging alone while she fed and on her return he would push in between her forearm and her body, seize a teat and suck. Satisfied, he would fall asleep and wake up later to scramble to the other side and suck the other teat, the mother moving her forearm out to allow access. Often, but not invariably, she would lick and groom him all Over while he was sucking. His subsequent development is best dealt with in diary form.

July lOth.

Belly fully covered with short hairs, eyes open.

July 13th. Baby first seen hanging asleep beside the mother and not under her wing. Thereafter though he sometimes slept under her wing after sucking, he more frequently slept alone.

Weight 10 grammes cold and presumably empty. He was always weighed when cold in order to avoid the variations in weight due to the amount of food or milk in his stomach. He was not taken from his mother and weighed before this in case it made her discard him.

July 21st. Baby first seen to groom himself, licking, stretching his wings and scratching with his hind feet. Weight 15 grammes.

389 July 24th. No reactions to a meal worm even when its juices were squeezed into his mouth.

July 28th. Juices of two meal worms swallowed but no attempt made to chew the skin. That evening after feeding the mother climbed up the opposite side of the wire netting to the baby. He became very restless scratching himself,stretching his wings right out and moving about. Finally he climbed down, up again the other side beside his mother and started to suck. This sort of behaviour was often seen when they thus became separated. For the next fortnight the baby was offered meal worms daily and ate the squeezed out juices but was incapable of dealing with the skin.

He was more active than the mother during the day scratching, grooming, stretching his wings, etc., warm and active while she was cold and asleep. Occasionally he was seen to suck when she was cold.

Aug. 1 Ith. When the baby tried to suck the mother kept her forearm pressed tightly against the teat for some little time.

Frustrated he scratched and groomed himself and then moved to the other side, when she relented and allowed him to suck.

BIRTH OF A SEROTINE BAT

Aug. 13th. Baby swallowed 2 large meal worms chewing up about ÂŁ of the skins.

Aug. 16th. 6 meal worms well chewed up.

Aug. 19th. 6 meal worms, 6 large house crickets all eaten normally. Thereafter he was fed by hand a fĂźll ration of 2-3 dozen meal worms or house crickets a day but continued to suck regularly until Sept. 5th. Thereafter the"mother usually refused him her teat, by now dry or almost dry, though he was seen attached to it on Sept. 18th. He was slow to learn to feed himself but on Sept. 16th suddenly started to pick up meal worms from his dish.

By Sept. 18th he was feeding well and could be looked upon as weaned.

Aug. 23rd. " Buzzing " as described above heard from the baby for thefirsttime ; thereafter it was heard and feit frequently.

Sept. 15th. Weight 24 grammes, forearm 46 mm. Another juvenile male serotine caught Aying on that day had weight 24 grammes, forearm 51 mm. It may be that a somewhat artificial diet restricted his growth, though the wild serotine was caught feeding on crickets which the captive one had in abundance with calcium boro-glucinate as a Supplement.

I am grateful to Messrs. Mears and Stainbank of the well known Whitechapel bell foundry for help towards investigations into the habits of various species of bat, animals with which they are not infrequently concerned professionally.