| Popis: |
Antarctic Fur Seals, Arctocephalus gazella, have increased from a few tens of individuals at the beginning of this century to over 900,000 now, most occurring at the north-west end of South Georgia. At Bird Island in recent years some 150,000 seals have come ashore in their breeding season. Since 1960 profound changes have taken place in the vegetation. Fur Seals destroy tussock grass, Poa flabellata, which is the dominant plant cover, by trampling and lying on the tops of the tussocks. Meadows of Deschampsia antarctica and cryptogams are also destroyed by trampling and this can lead to local erosion. Destruction of the tussock deprives birds (the endemic Pipit, Anthus antarcticus, and Pintail, Anas georgica, and several burrowing petrels) of breeding habitat and exposes them to predation by Antarctic Skuas, Catharacta antarctica. The destruction of vegetation by Fur Seals is believed to be a new phenomenon associated with high density occupation by the recovering population. This may reach 4 × 106 by the year 2000, and the effects are likely to increase. The successful recovery of the Fur Seals may well be accompanied by significant decreases in several bird populations. |
