Collins New Naturalist Library. H. Hewer R.
the study of them without a great deal of trouble, preparation and expense. It has, of course, been easier to kill them than to study them alive, but even then the difficulties involved have been sufficient to enable both species to survive under as great a pressure of persecution as man has found it possible and economical to mount. Had they been solely terrestrial they would have disappeared long ago. Had they been marine and social they may well have been as reduced in numbers as their fellow mammals the Cetacea. Only in modern times with greatly increased resources of powered boats, helicopters and of camping facilities in remote and uninhabited islands and coasts has it been possible to pursue a planned scheme of research on the grey seal. Investigation on the same scale for the common seal is yet to come, in fact it may not be necessary as its habits do not appear to be quite so complex, but it may be almost equally difficult to prove it.
Undoubtedly the species of pinnipede about which most is known is the northern fur-seal (Callorhinus ursinus). Its value as a fur-bearing animal made it essential that the main breeding colonies should be saved and during this century the United States Fish and Wildlife Service has carried out a series of investigations of the greatest importance. As a result of the knowledge gained it is now possible to ‘manage’ the population so as to obtain a maximum return of seal skins, consistent with the maintenance of the population at the necessary level of numbers and condition, at the same time preventing too great an excess which would adversely affect the important fishing interests of the north Pacific. While giving every credit to the ingenuity and skill of the research workers, it must be admitted that several factors have greatly assisted them. The first and obvious one is the economic value of the fur-seal which not only sanctioned the expenditure of money in research, but also provided considerable man-power (non-scientific) for major operations of tagging tens of thousands of the seal pups. The second factor involved is the behaviour of the immature groups which assemble on sites near to the breeding rookeries, segregated into the sexes. The adult bulls and cows too are markedly different in size and pelage and so can easily be distinguished at a distance without the aid of binoculars. Even in the non-breeding season help was available in an extensive pelagic sealing industry over the north Pacific. Nothing comparable is available in the north Atlantic. For all the information available from ships in the North Sea, it might have no seals in it at all, yet we know now that young grey seals cross it regularly and that at certain times of the year the majority of grey seal cows are not in coastal waters. Consequently the pattern set out in detail for the northern fur-seal is of the greatest importance for purposes of comparison wherever possible.
British workers have been responsible for a great deal of work on antarctic pinnipedes such as the Weddell, crabeater and southern elephant seals (Phocidae), the southern sea-lion and southern fur-seal (Otariidae) in the course of the ‘Discovery’ investigations of the inter-war period and of the Falkland Islands Dependencies Survey after the second world war. These researches were undertaken in an attempt to save the natural resources of the southern whale and pinnipede populations. The latter had already been brought to a point of near extinction and the former could easily follow. As a matter of history the pinnipedes have been saved, while the whales have been brought near their end. We were probably right to put our energies into this exercise when we did for not only did it have a happy result for the seals, but we have acquired a national expertise in seals and sealing which is only equalled by that of the United States Fish and Wildlife Service who were responsible not only for the work in the Pribilov Islands, but also for research on the northern elephant seal and other pinnipedes off the Californian coast.
More recently the Canadian Arctic Biological Unit has been formed and is doing good work on seals and walrus off the western north Atlantic seaboard. In the Soviet Union attention has also been turned to this natural resource and work has been done on several species in the north western Pacific Ocean.
In the next chapter we shall see how in the last thirty years or so there has been a considerable growth in the interest shown by both professional and amateur zoologists in Britain in our own species. There has also been expressed a great deal of public concern over the status of our seals but much of this has been ill-informed. The problems are complex and over simplification can lead, as it has done in the past, to harmful action when only good is meant. Intentions are not enough; knowledge is essential.
THE relationships of the grey seal, Halichoerus grypus (Fab.) have been discussed in the previous chapter. It clearly emerges that this species occupies a unique position being the only species of the genus.
The world distribution of the grey seal is peculiar and unlike that of any other seal species. There appear to be three distinct populations (Fig. 7). To prove that there is never any interchange of individuals is practically impossible, but all the available evidence suggests that no real exchange takes place. The three populations are centred on the Baltic Sea, on the eastern north Atlantic and in the western north Atlantic. Davies (1957), in a very interesting paper which dealt with the possible geographical and historical reasons for this separation, suggested that these three populations should be called the Baltic, eastern Atlantic and western Atlantic respectively. There are also very good biological reasons for the separation. The eastern Atlantic grey seals, most of which are present in British waters, breed in the autumn;* the other two populations breed in late winter to early spring. Similarly the eastern Atlantic seals breed on land, either on beaches or on the landward slopes; the others tend to breed on ice and only if it is an exceptional year and there is little ice do the western Atlantic ones breed on the adjacent shore. Consequent upon these differences the social structure of the breeding seals is different. The eastern Atlantic seals tend to form large rookeries in which the cows outnumber the bulls by 5 to 10 times; in the ice-breeding forms a much closer approximation to equality is found in the western Atlantic region and such information as is available for the Baltic seems to suggest that the same applies there – isolated cows with their pups with attendant bulls over a wide area of ice floe.
Davies points out that all three populations must have been united during the last Inter-glacial period, occupying the seas from northern Labrador to Greenland, Iceland, Norway and the White Sea, on the average about 15° north of the present range (Fig. 8). As the species is a land-breeder as opposed to an ice-breeder the succeeding Glacial period would have forced the grey seals to separate into two populations, one occupying the seas from Newfoundland to Florida and the other the seas from the ‘British Isles’ (which were not separated from the continent at that time) to the Moroccan coast. With the first retreat of the ice and glacial conditions covering the ‘British Isles’ and northern Europe, the North Sea and Baltic Sea came into existence again broadly joined in the region now known as southern Sweden and Denmark. The grey seals of the eastern Atlantic had meanwhile moved northward again occupying the seas from the Bay of Biscay round the ‘British Isles’ and into the Baltic. However after this changes in the land and sea levels caused a land connection to appear between Sweden and north Germany (Pomerania) thus cutting off a lake comprising the area of the present Baltic, including the Gulf of Bothnia and most of present-day Finland. This is known as the Ancylus Lake and in it were isolated grey seals which formed the origin of the present Baltic population. Much more recently the North Sea and the Baltic have again been joined but only by very narrow channels at the southern end of the Kattegat. As we shall see later there is evidence that only the very northern end of the Kattegat is entered very occasionally by young grey seals. The main eastern Atlantic population of grey seals no longer use the southern shores of the North Sea which are sand and mud only, quite unlike the preferred rocky situations in Britain and Norway.
FIG. 7. World distribution of the grey seal. There are three