Arctic Fox Control Improves Productivity of Arctic Nesting Geese
R. MICHAEL ANTHONY, PAUL L. FLINT,
AND JAMES S. SEDINGER
Alaska Fish and Wildlife Research Center, U.S. Fish and Wildlife Service,
1011 East Tudor Road, Anchorage, AK 99503; Institute of Arctic Biology
and Department of Biology and Wildlife, University of Alaska,
Fairbanks, AK 99775-0180
Populations of geese that nest on the Yukon-Kuskokwim Delta (YKD) of western Alaska have declined substantially from high levels in the 1960s. Numbers of cackling Canada gem (Branta canadensis minima) declined from a high of over 350,000 in 1966 to less than 25,000 in 1985. Nesting colonies of black brant (Branta bernicla nigricans) also decreased in size and abundance from the 1960s. In the early 1980s, arctic fox (Alopex lagopus) were recognized as the most serious predator on goose nests, despite having relatively little effect on nesting during the 1960s and 1970s when goose numbers were high. Because of the impact of predation on goose reproduction, experimental fox control was conducted at two sites during 1986-89.
In 1986, fox control was initiated at a black brant colony that was in jeopardy following several years of nearly complete reproductive failure. Fifty-two foxes were killed, mostly in 1986 and 1987. Low capture rates in 1988 and 1989 coincided with an eruption of tundra voles throughout the YKD. Mean nesting success in the brant colony was 82.2 + 1.2 % during the 4 years of fox control. Mean nest success at another large colony where foxes were not controlled during the same time was 53.7 + 11.8 %. Fox control was successful in increasing productivity in the brant colony, which was apparently too small (ca. 1,100 nest in 1985) to overcome predation during high populations of arctic foxes in coastal habitats.
Another fox control study is underway to determine the feasibility of improving the nesting success of cackling Canada geese. In both 1988 and 1989, 26 arctic foxes were removed from an area with relatively high nest densities. In 1988, there was no significant difference in nesting success between the removal area and a nearby check area, probably because of low fox activity in the check area. In 1989, nesting success for cackling (88 % versus 61 %) and emperor geese (98 % versus 82 %) in the removal area and the check area was different.
Our results identified several factors affecting nest predation. First, most nest predation is by arctic foxes. Arctic foxes typically inhabit the wetter habitats where these geese nest, whereas red foxes occupy drier habitats and rarely use wet areas. In the absence of foxes, nest losses to predators are generally low for cackling geese and brant. Predation on adult geese is negligible. Immigration of foxes into removal areas has been negligible during the nesting period (mid-May to early July). Reoccupation of vacant habitats occurs with dispersal of families in fall. Finally, predation rates on nests are probably influenced by fluctuating microtine populations plus abundance and distribution of marine mammal carcasses, which may influence behavior, survival, productivity, and distribution of foxes.
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