Reindeer in South Georgia are an example of an animal which has been introduced outside its native range. The reindeer, a species of deer adapted to arctic and subarctic climates, was introduced to the subantarctic island of South Georgia by Norwegian whalers in the early 20th century.[1] The reason for the introduction was to provide both recreational hunting and fresh meat for the numerous people working in the whaling industry on the island at the time.[1] Since then, although the people have departed, the reindeer population, in two geographically separated wild herds, has increased to the point where their presence is causing environmental damage and has led to a decision to eradicate them.
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The first introduction was made by the brothers C.A. and L.E. Larsen in November 1911. Three males and seven females from Hemsedal in southern Norway were released at Ocean Harbour (then the site of an active whaling station) on the Barff Peninsula, on the northern coast of South Georgia. These formed the basis of what came to be called the Barff herd which, by 1958, had increased to 3000 animals. A 1976 population estimate of 1900 head indicated subsequent decrease, though with some range expansion to Royal Bay.[1]
A second introduction was made in 1912 by the Christian Salvesen Company. Two male and three female reindeer were left at Leith Harbour on the Busen Peninsula in Stromness Bay, also on the north coast of the island. By 1918 they had increased to 20 animals, but the entire herd was killed by an avalanche that year.[1]
The third introduction took place in 1925; three males and four females were released at Husvik Harbour in Stromness Bay. These became the nucleus of the Busen herd, the numbers of which increased slowly to 40 in 1953 before climbing rapidly to about 800 head by the early 1990s. The source of the animals was the same as that of the Barff herd.[1]
The Barff herd was relatively isolated from human access and increased rapidly in size before it outgrew its resources and declined in numbers. The Busen herd, however, was much more accessible to the human population of South Georgia; its size was kept relatively low by regular hunting until whale processing declined and came to an end.[2]
Since the whaling industry ended in the 1960s, and those employed by it departed, South Georgia has been largely depopulated except for a small military presence, visiting scientists and occasional tourists from cruise ships or private yachts. Little hunting or any other human control of the reindeer has occurred. The two herds, separated by glaciers terminating in the ocean and isolated from other ice and snow free areas, comprise some 2600 animals occupying 318 km2, one third of the total vegetated area, and thus potential grazing habitat, of the island.[1][2]
Rutting peaks between the 20th and 30th of March, with calves being born in November. Males become sexually mature at 4-8 months old and females can first conceive at 16-17 months. The mean generation length is 4.2 years, with males having an average 7-8 year, and females an 11-12 year, lifespan, with annual mortality of 30-40%. The main limiting factor in the population is the availability of winter forage; as well as starvation, a significant cause of mortality is falls from cliffs while trying to access ungrazed areas.[2]
The population density of the reindeer in South Georgia is generally much higher than in their native range. In the Svalbard archipelago in the Arctic, reindeer density is about 5/km2, while 7/km2 is considered a safe stocking rate for winter range. In South Georgia, although densities vary, values ranging from 40/km2 to 85/km2 have been recorded.[2]
The areas occupied by reindeer on South Georgia are the most vegetated and biologically diverse on the island. The impact of the animals has been severe, resulting in overgrazing of the native Tussac Grass and Greater Burnet, soil erosion, loss of plant community biodiversity and the spread of invasive weeds, such as the introduced grass Poa annua which is better able to sustain grazing than the native flora.[1]
Because of the environmental damage caused by the reindeer, and the danger that glacial retreat caused by global warming will allow the reindeer to extend their range to other areas of the island, their permanent eradication has been proposed, with an announcement of intention being made on 19 February 2011.[3] In order to preserve their genetic resources, and in order to help diversify agriculture in the Falkland Islands, a translocation of 59 South Georgian reindeer calves (26 males and 33 females) from the Busen herd to the Falklands was undertaken in 2001 by the Falkland Island Government to establish a commercial herd there. Their first offspring were produced in 2003.[1]
Few introductions of reindeer to places in the southern hemisphere have been carried out. An attempted introduction in the late 1940s to southern Argentina failed when the animals were subsequently killed. An attempt to translocate animals from South Georgia to Isla Navarino, Chile, failed when seven of the eight animals being transported died on the sea voyage. Apart from South Georgia, the only other successful introduction was in 1954 to the subantarctic Kerguelen Islands, a French territory in the southern Indian Ocean, with ten reindeer from Swedish Lapland, which had increased by the 1970s to a population of about 2,000.[1]