222 



R. D. JONES AND G. V. BYRD 



(Gabrielson and Lincoln 1959). Foxes were re- 

 leased on Adak in 1924, and on Amchitka in 

 1921. Adak has an area of 751 km 2 and Am- 

 chitka 350 km 2 . Adak is irregular in shape 

 with extensive precipitous shorelines, rela- 

 tively few beaches, and a large, central moun- 

 tainous hinterland which foxes rarely pene- 

 trated. Amchitka, on the other hand, presents 

 a zone of marine planation on its eastern two 

 thirds, low mountains on the rest, shelving 

 beaches around most of the island, and a long, 

 linear, narrow shape that foxes explored com- 

 pletely. By 1949 ptarmigan were difficult to 

 find on Amchitka, and then only in the 

 highest, steepest section of the mountains. 

 They were extirpated from the low, eastern 

 two thirds of the island. The foxes flourished 

 on Amchitka, but did much less well on Adak, 

 where the ptarmigan population fluctuated in 

 a normal cyclic manner, apparently uninflu- 

 enced by the foxes. Then the foxes were eradi- 

 cated on Amchitka in the 1950's, and by 1962 

 the ptarmigan had spread over the whole of 

 the island and become one of the most con- 

 spicuous avian features of the landscape. 



Animal Introductions 



Nonpredatory Animals 



Man has taken ungulates with him to many 

 islands. Although numerous records of live- 

 stock introductions are available, few provide 

 information relating to the effects of these 

 animals on the habitat and their fauna unless 

 the impact has been severe. 



A most noteworthy example of destruction 

 by ungulates occurred on Guadalupe Island 

 off the coast of Baja California. Domestic 

 goats (Capra hircus) were introduced in the 

 unrecorded past with the result that little of 

 the once abundant vegetation remains. In its 

 place introduced species capable of withstand- 

 ing heavy grazing are abundant over most of 

 the island. Several endemic avian species are 

 now considered extinct, including the Guada- 

 lupe storm-petrel, Oceanodroma macrodac- 

 tyla (Howell and Cade 1954; Jehl 1972). 



Sheep (Ovis aries) have been introduced to 

 seabird nesting islands with varying results. 

 In Bass Strait, Australia, Norman (1970) 

 studied the effects of introduced sheep on 



vegetation and birds. He cited various papers 

 attributing destruction of colonies of shear- 

 waters (Puffinus sp.) to the activities of sheep, 

 primarily their treading on the burrows. He 

 found, however, that on Big Green Island and 

 Phillip Island, sheep were not responsible for 

 declines in shearwater breeding success, nor 

 did they prevent expansion of colonies. 



Other authors have reported damage to sea- 

 bird nesting areas by sheep. One such 

 example in the eastern North Pacific region 

 concerns Protection Island, Washington. Ac- 

 cording to Richardson (1961), 100 to 300 

 sheep grazed freely on the island since 1958. 

 He reported damage by grazing and frequent 

 trampling of nesting areas of rhinoceros auk- 

 lets (Cerorhinca monocerata). Landslides were 

 initiated by these activities, rendering the 

 slopes unusable by auklets. Of the burrows in 

 his study area, 46% were buried by slides. He 

 did not determine mortality. 



Other avian consequences may flow from 

 sheep introductions. Husbandry of these 

 ungulates has been practiced with varying 

 success for many years in the Aleutian 

 Islands, most notably on Umnak and Un- 

 alaska islands, both of which have large na- 

 tive populations of bald eagles, Haliaeetus 

 leucocephalus (Gabrielson and Lincoln 1959). 

 Before the introduction of sheep, these rap- 

 tors were oriented to the sea, hunting fish and 

 seabirds. Sheep presented a new resource and 

 presently the industry found itself confronted 

 by a formidable predator, and demanded that 

 eagles be destroyed (letter to William Egan, 

 Governor of Alaska, from James S. Bynum, 

 Secretary-treasurer, Umnak Company, Inc.). 



Other ungulates introduced on Alaska is- 

 lands include cattle (Bos taurus) on Chernof- 

 ski and Chernabura islands; caribou (Rangifer 

 tarandus) on Adak; reindeer on St. Matthew, 

 Nunivak, Atka, Umnak, St. Paul, St. 

 Lawrence, Hagemeister, and Kodiak as well 

 as many interior locations; deer (Odocoileus 

 hemionus) on Kodiak and Afognak; elk 

 (Cervus canadensis) on Afognak; and musk 

 oxen (Ouibos moschatus) on Nunivak. All 

 these animals have maintained populations on 

 islands for a time, and some appear likely to 

 do so into the distant future. Specific effects 

 on seabirds is generally not known, but 

 trampling of grassy slopes such as that re- 



