Collins New Naturalist Library. H. Hewer R.

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СКАЧАТЬ and any more specimens which might belong to that species can be compared with it. Unfortunately this is not the case with most species of seal and there has been an enormous amount of confusion, because everything depended on a verbal description. Consequently although it could confidently be asserted that Halichoerus grypus existed (it could easily be seen in the Baltic) and that Erignathus barbatus was clearly different and occurred, widespread, in the north Atlantic, it was not known to which the grey seal of Britain belonged. The earlier descriptions of it were too vague, although several of the early workers thought they corresponded more nearly with those of the bearded seal. The really astounding thing was that there was such a paucity of material for comparison. Hundreds of grey seals were killed each year for blubber or hide, yet until very recently the British Museum (Natural History) had only one adult skull, and many international museums had none. No complete skeleton existed in any museum except the National Museum of Wales in Cardiff where that of a cow was mounted.* If the hard parts were not preserved then certainly the soft parts were not. No account of the general disposition of the viscera can be found in the literature and the information about most of the anatomy of soft parts contained in this book has been specially obtained by first-hand dissection.

      An equal ignorance was displayed about the general behaviour and life-history of the animal. The principal account is given by Millais (1905) who collected together what previous writers had said and added a great many observations of his own. But all of this was anecdotal and largely based on occasional visits to rookeries lasting a few hours or at most a day or two. The basic difficulty was one of accessibility for, as we shall see, even the breeding sites are isolated and situated in some of the stormiest waters round the British Isles. When the seals are no longer on these rookeries they may be hauled-out on any of dozens of islets or skerries spread over many square miles of sea and can only be found by meticulous searching. We know now that these sites can alter with the seasons and may, to a lesser degree, alter from day to day depending on wind and tide or even, one feels, on the idiosyncrasies of the seals themselves. It is no wonder, therefore, that earlier workers found difficulties in establishing even the basic facts of the yearly cycles and life-histories of this seal, without the aid of modern means of transport.

      The first serious attempt to come to grips with the problems posed by this species was made by F. Fraser Darling in the late 1930’s. He decided to live with the grey seals and nearly all subsequent workers have done the same. This involves some difficulties and dangers, for all the islands involved are uninhabited and some are without fresh water. Consequently all supplies and a form of habitation must be taken ashore to cover not only the intended stay but for a much longer period, since return to the mainland is entirely dependent on weather and an enforced stay of up to a week tacked on to a planned three weeks is not unusual. Darling began his studies in small rookeries where each individual could be recognised and the progress of its behaviour related from day to day. Only in this way could the correct succession or pattern of behaviour become firmly established. To plunge into a large rookery with hundreds or even thousands of individuals, more arriving and others departing, makes it impossible for the observer to understand what is happening unless prior experience has shown him the correct sequence of activities. Darling’s observations in the Treshnish and Summer Isles therefore prepared him for North Rona, and his accounts of the breeding season are remarkably accurate.

      In a book published in 1936 (A Beast Book for the Pocket) some 27 statements are made concerning the biology of the grey seal. Of these 22 are wrong; not slightly wrong but completely and utterly so. Darling’s work altered all that for the autumnal period and for much of the summer.

      After the second world war our knowledge increased rapidly. Mr J. L. Davies began in 1947 by investigating the breeding season in the comparatively small group found off the Pembrokeshire coast, notably on Ramsey Island. In two subsequent years, 1950–51 a small group from London led by Dr L. Harrison Matthews F.R.S. continued the work there and enlarged it to cover the nutrition of the pup and some basic aspects of reproduction. Quite independently in 1951 a group from the Northumberland, Durham and Newcastle-upon-Tyne Natural History Society led by Mrs Grace Hickling began to weigh and tag pups in the hope of tracing the movements of the moulters when once they had left the Farne Islands. Their success was immediate and the idea caught on. I had been with the group on Ramsey Island in 1951 and in the next two years tagged as many pups as I could. In the last of these years I was joined by Dr K. M. Backhouse who had taken part in the Farne Island work and who has continued to work with me both in the field and the laboratory ever since.

      In 1954 and 1955 I went to Shillay in the Outer Hebrides to follow up a report of a disproportionate number of bull seals seen there by Dr J. Morton Boyd (who afterwards became Director of the Scottish Nature Conservancy). This led to interesting observations in pre-breeding behaviour, a field which is still largely open for the investigator. In 1956–57 Dr Backhouse joined me in observations in the Inner Hebrides, on islets off Oronsay, again to cover the pre-breeding period and the establishment of a breeding community on the rookery.

      All these observations were connected with the breeding season, as, in fact, had been all the pre-war observations. In 1954 Dr Backhouse and myself decided to begin investigations during the winter and spring using the Ramsey Island group as our base as being within reasonable touch of London, travelling down over Friday night and back on Sunday night. This was dictated by our teaching duties during term time, but could be altered and ameliorated during the Christmas or Easter vacations. Our success was very limited since only two weekends a month were suitable on account of tides, and winter gales, either before or during the weekend, prevented us or the seals from reaching the island on many occasions.

      Three very significant results emerged however; first that there was a delay in the development of the embryo (January 1956) and secondly that there was a small but quite significant number of births of spring pups (April 1956) and thirdly that this was associated in the Pembrokeshire group with large haul-outs of moulting bulls in the spring (April 1957).

      Meanwhile quite unknown to us Prof. J. D. Craggs, an electronics engineer in the University of Liverpool, and N. F. Ellison, both active members of the Liverpool Natural History Society, turned their attention from the birds of Hilbre Island, off the Wirral peninsula, to the seals which gathered at low-water on the West Hoyle Bank a mile or so farther out to sea. These had previously not been very numerous and had always been thought to be common seals. They turned out to be grey seals and a series of observations made almost every fortnight throughout the year over five years (1952–57) showed not only that the numbers were increasing, but that they fluctuated regularly during the year. They were observing the obverse of those investigating the breeding grounds and thereby made a most valuable contribution.

      To estimate the numbers of grey seals on and around the breeding grounds has always been an objective of observers and one of the difficulties has been the tendency of the seals to use small islands and skerries within a considerable radius from the breeding centre itself. Thus it was physically impossible to make a simultaneous count over the whole area, and this was imperative if the count was to have any significance. The use of an aeroplane had been tried during the breeding season in 1947 when J. L. Davies knew the numbers of seals from a ‘ground count’ in Pembrokeshire. It showed that little reliance could be placed on such observations unless the ground was fairly clear or only pups were being counted. Adults and moulters are too cryptically coloured to be easily recognisable. The only group which showed a promise of success was that of the Farne Islands where the haul-out points are necessarily limited to the outermost of the Outer Farnes and are not in fact far from the breeding islands of the Outer Farnes. From 1958 onwards monthly ground counts were made there by Mrs Hickling and Dr J. Coulson and so gave a picture the converse of Craggs and Ellison’s.

      In 1958 breeding of grey seals was discovered on Scroby Sands off Great Yarmouth and appeared to point to an increase and spread of the Farne Island group. In this year, too, North Rona became a National Nature Reserve so that in 1959 an expedition comprising Dr J. Morton Boyd and Dr J. Lockie of Nature Conservancy (Scotland), Mr J. MacGeogh, the honorary СКАЧАТЬ