Expansion of the geographical distribution of red foxes (Vulpes vulpes) into the far north tundra region may lead to competition between arctic (Alopex lagopus) and red foxes for space and resources. Behavioral interactions between red and arctic foxes were evaluated during 9 trials conducted in a 4.05ha enclosure near Woodworth, North Dakota. Each trial consisted of introducing a male-female pair of arctic foxes into the enclosure and allowing them to acclimate for approximately a week before releasing a female red fox into the enclosure, followed by her mate a few days later. In 8 of 9 trials, red foxes were dominant over arctic foxes during encounters. Activity of the arctic foxes decreased upon addition of red foxes. Arctic foxes tried unsuccessfully to defend preferred den, resting, and feeding areas. Even though the outcome of competition between red and arctic foxes in the Arctic is uncertain, the more aggressive red fox can dominate arctic foxes in direct competition for den sites and other limited resources. J. WILDL. MANAGE. 46(4):877-884 The impact of energy development on Arctic ecosystems is not yet known, but it could affect the abundance and distribution of many species. In recent years the red fox has extended its range in Arctic regions (Marsh 1938, Skrobov 1959, Macpherson 1964). If human-induced environmental changes, such as energy development, facilitate the range extension of red foxes, direct competition with the arctic fox could intensify in some regions. Competition for limited resources will result when both species, occupying the same space, seek the same food and denning sites. Macpherson (1970) and Danilov (1958) reported that denning sites for foxes are scarce in the Arctic, and Skrobov (1959) and Ostbye et al. (1978) reported on occupation of arctic fox dens by red foxes. Man often creates artificial food sources in the Arctic which are used by both red and arctic foxes (Vincent 1958, Klein 1973, Hanson and Eberhardt 1977, Eberhardt 1977). In northern Alaska, red foxes may also take advantage of roads for dispersal into remote areas, or use buildings and other man-made objects, such as steel pipes, for denning; this may result in higher densities of red foxes in specific localities. The purpose of this study was to determine the outcome of interactions between arctic and red foxes and to develop a more accurate scenario of the consequences of competition between the 2 species. Because the chance of seeing encounters between the 2 species in the Arctic is small, this study was conducted by observing interactions of confined fox-
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