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A FIND IN THE GIPPING VALLEY TRENCHING for a new sewage system has been in progress at Bramford for many months, mainly in ancient terrace gravels of the River Gipping which appear to have been deposited toward the close of the Pleistocene epoch. No mammalian fossils had been discovered until the 23 rd April when a magnificent antler of Reindeer, Rangifer tarandus, was unearthed at a depth of twelve feet below the road surface, and about nine feet above the present river bed. T h e antler was broken and portions are probably still buried ; these cannot be recovered because of the crumbly nature of the sand and gravel. T h e antler, which is from the left side, is much larger than any other specimen found in the Ipswich area and must have belonged to an old animal which was equal in size to a fine head of a Caribou from Canada, which is in the Ipswich Museum. It is estimated to have been at least forty inches in length along the curve and the beam is two inches diameter. T h e largest portion is twenty-two inches long from where it is broken off just above the bez tine to the beginning of the palmation, of which only two pieces were saved. It is considered the gravels may be richer in mammalian remains at a greater depth and to be very slightly later than the deposits on the opposite side of the river at Barham. ^

NOTES ON THE FEEDING OF THE LONG-EARED T H E E A R L OF

HABITS BAT

CRANBROOK

THAT bats navigate by echo-location is well known. T h e y give out bursts of ultra-sonic impulses when in flight and are able to identify obstacles in their path by the echoes of those Impulses reflected back and picked up by their ears. A bhndfold bat avoids obstacles as easily as a fĂźll sighted one : a bat with its ears plugged is helpless, blundering into obstacles whether in light or darkness, fĂźll sighted or blindfold. T h e ultra-somc Impulses are sound waves emitted at frequencies far beyond the compass of the human ear though bats also make audible " con-


156

FEEDING HABITS OF LONG-EARED BAT

versational " squeaks at so high a pitch that many people, especially those past middle age, cannot hear them. These squeaks have nothing to do with echo location. Most bats capture their insect prey at flight in mid air. D. R. Griffith (" Listening in the dark." Yale University Press, 1958) found that blindfold bats can avoid by echo-location wires as small as J millimetre in diameter, into which they blundered with ears plugged but füll sighted. He also found that bats picked up and followed small plugs of cotton wool Aying through the air, objects which were so soft and smooth that they set up no vibrations and could only have been picked up by echo-location. It is probable therefore that while in flight they can similarly identify and capture insects which they could not see. The long-eared bat (Plecotus auritus) on the other hand is known to pick the insects on which it feeds off the foliage of trees, sallow catkins, etc. Its flight amongst the foliage is a gliding one, with frequent pauses to capture insects. When going to another tree the flight is swift, strong and close to the ground (L. Harrison Matthews. " British Mammals " Collins, 1952). It is not known whether it recognises its prey by sight or by echo-location. A long-eared bat kept during February and March, 1959, in a room with a night temperature of 54° - 58° F. learned within ten days to feed and drink from shallow round casseroles placed on the floor of its cage. Drinking, it would stand on the edge of the casserole with its wrists and thumbs in the water lapping like a dog, feeding it would get right inside the casserole, picking up the meal worms and blow-fly pupae on which it was fed by feeling for them with its mouth. It did not appear to look for its food in spite of its relatively large eyes but feit about until it found and seized its prey, when it would sit head up, body at an angle of about 45°, munching. Usually it would seize a meal worm with a sudden snap and sit up at once to eat. Rarely it would make some movement to push its prey into the interfemoral pouch but it would always thereafter sit up as described above. After feeding it would crawl to the water and having drunk, climb the bark lined wall of its box, turn head downwards, hang up and go to sleep, with the ears folded, but stretched out at füll length, under its wings. When the position of the water and food casseroles was reversed it went first to the normal place for food and finding water did not drink but crawled about until it found the food casserole—both were similar in size—fed and then went back to drink. When crawling about, feeding or drinking the ears were only partially erect, the lower portion stiff, the upper flaccid with the ends curled over and outwards, looking rather like a ram's horns. They were held in the same position when the bat was hanging up awake but not taking much notice of what was going on around it. When the bat was fed in the hand its ears would be held in the " ram's horn " position but when it had had enough


FEEDING HABITS OK LONG-EARED BAT

157

its ears would become stiff, turgid and erect and remain so while the animal walked to a suitable position from which to take flight. When the ears were in this erect position the bat made a very quiet ticking noise, the intervals between the ticks decreasing; until they merged into a buzz, rather like the purr of a cat, just beforetaking off. If the bat was prevented from Aying by, e.g., being made to walk through each half closed hand in turn repeatedly, the tick or buzz would continue as long as the ears were held erect and the bat was obviously trying to reach a position from which it could takeflight.If the bat gave up the struggle and relaxed, the ears would drop and the ticking sound would cease. The sound was never heard when the ears were in the " ram's horn "' position ; only, and always, when the ears were erect. These ticks, first described by S. Dijkgraaf in 1943, should not be confused with the ultra-sonic echo-locating waves used by bats in flight though they are in fact a component of them and are only heard when a bat is emitting the ultra-sonic echo-locating impulses. When inflighta long-eared bat's ears are held stiffly erect at an angle of about 45° to each other. Griffm (Zoe. cit.) found that when the tips are stuck together with collodion, so that the ears are held parallel, the bat blunders into obstacles, presumably because its echo-locating device is thrown out. The same thing happens when the bat's ears are artificially deformed in other ways, e.g., the tips bent over and stuck down or the edges of each ear stuck together. When the collodion is removed and the ears can once more be held at the normal angle the bat avoids obstacles in the usual way. A long-eared bat therefore can only make use of its echo-locating device when the ears are held in the normal Aying position and the behaviour of the particular bat under review seems to show that the ultra-sonic impulses are only emitted when the ears are held in that position. Barrett-Hamilton and Hinton (A History of British Mammals 1910-21) note that when a long-eared bat is hovering to pick insects off branches the long ears are " bent outwards, so much as to curl down the sides of the face," i.e. in the resting and silent " ram's horn" position, not in the Aying echo-locating one. When feeding in this way, therefore, with the ears held in the " ram's horn " position the bat cannot be using its echo locating device and must be relying on sight or smell. The observations noted above on feeding in captivity do not positively indicate the use of either sight or smell but the eyes of a long eared-bat are proportionately much larger than those of other similar sized British bats and it would seem that they must identify beetles, moths, etc., on branches or Aowers by sight and not by echolocation.

Notes on the Feeding Habits of the Long-Eared Bat  
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