CONSERVATIVE ANIMALS

Greymouth Evening Star, 11 July 1931, Page 4

CONSERVATIVE ANIMALS

KEEPING IN GROOVES. Conservatism plays a large part in the lives of most wild animals (writes E G. Boulenger, Director of the Zoological Society’s Aquarium, in the “Daily Telegraph”). Swallows return to the same eaves they occupied a previous year, even though there aic others just as good a few cottages away, while finches make for the same left,"and tomtits for the same old jampot in the same neglected garden. Often such conservatism leads to trouble. There is the classic case of tlie ospreys who used for generations the same nest in the North of Skye. Each succeeding year saw a fresh layer of leaves and offal added to the nest of yester-year, till at the end of twelve years there had arisen a tower of rubbish , some 20ft. in height. A sudden gale demolished the entiie structure , and with it the eggs and hopes of the tenants. Force of habit is deeply rooted in such comparatively lowly creatures as reptiles and amphibians. A lizard will take to one corner of a run or one spot on a branch, and defend it aga-inst all comers—with its lite if necessary. Some interesting observations have been made on the habits of geckos. Although several species may inhabit the same locality, yet as a general rule they keep separate and aloof from, each other. In India, for instance, in a house the dark cellars may be the resort of one species, the roof of another, whilst the crevices of the walls may be exclusively occupied by a third. However, at night they issue forth in quest of insects, and may be found mixed up together in the same spot. But on the slightest disturbance, or when they have done feeding, they return hurriedly to their hiding-places.

Why, wo ask ourselves, should the salmon make for the stream of its forefathers, usually in the face of great difficulties? Even more wonderful, if possible, is the case of the eel. Here we have a creature, born off the Bermudas, travelling across the Atlantic and eventually making its way up European rivers and mountain streams. Currents and the search for food may possibly explain how an eel from Bermuda. reaches a lake in the Swiss Alps, but the exact forces which eventually bl ing the eel back to the place of its birth have yet to be discovered. True, file mature eels are urged forward by the reproductive instinct, but it would be grotesque to represent that they have tender memories of the spot they left in their infancy.

Even in captivity many fish are equally tied to their favourite locations, and in the Zoo Aquarium a number of tho inmates take up their stands in some particular corner of the tank which, to the human eye, is no better, or, indeed, not so good, as many others available. If disturbed by some accident. or necessary operation such as the daily cleansing of the tank floor with a suction pipe, tiie fish at once return to their chosen haunts. Tho Zoo authorities have often proved to their cost that established animals removed to another cage'identical in every respect ‘ frequently die through ‘‘causes unknown.” Eyeii among molluscs this liking for a particular spot is often rigidly maintained. One might reasonagly suppose that one rock is much like another toza limpet, yet marked limpets have proved that tho mollusc may keep to one site for several years, wandering a few feet away to feed, and then returning to its pitch, till the sharp edges of its shell and the action of its powerful feet wear a circular impression in the hardest material. Most, house-builders show great prejudice in the choice of materials. A curious instance of this is offered by the larvae of some cadis flies. Some forms which make a habit of building cases of sand and mud will, if dragged from their homes and placed in an aquarium carpeted with pebbles, shells, or even glass beads, quickly adapt themselves to the new material. Not so others, and many kinds normally using sticks or similar debris will perish father than cover their nakedness with a. material new to them.