2008-06-12_GENERAL DOCUMENTS - C1980007 (3)

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Lxploitation competition may contribute to lvnx starvation and reduced recruitment. Luring periods of low snowshoe hare numbers, starvation accounted for up to two-thirds of al, natural • Ivnx deaths in the Northwest Territories ofCanada (Poole 1994). Major predators of snowshoe hare include lynx, northern goshawk (Accipiter gentilis), great homed owl (Bllb0 vii ?i?ziaraus); bobcat. covote. red fox (T`ulpes vulpes), fisher. and mountain lion. In southern portions of snowshoe hare range, predators may limit hare populations to lower densities than in the taiga (Dolbeer and Clark 1975. Wolff 1980; Koehler and Aubry 1994). Population Dynamics In Canada and Alaska, lynx populations undergo extreme fluctuations in response to snowshoe hare population cycles. enlarging or dispersing from their home ranges and ceasing the rt::cruitment of young into the population after hare populations decline (Mowat et al. 2000). In the southern portion of the range in the contiguous United States, lynx populations appear to be naturally limited by the availability of snowshoe hares, as suggested by large home range size, high kitten mortality due to starvation, and greater reliance on alternate prey. These characteristics appear to be similar to those exhibited by lynx populations in the taiga during the low phase of the population cycle (Quinn and Parker 1987, Koehler 1990, Aubry et al. 2000). This is likely due to the inherently patchy distribution of lynx and hare habitat in the contiguous United States and corresponding lower densities of hares. A lack of accurate data limits our understanding of lynx population dynamics in the contiguous United States and precludes drawing definitive conclusions about lynx population trends. Formal surveys designed specifically to detect lynx have rarely been conducted. Many reports of • Lynx (e.g., visual observations, snow tracks) have been collected incidentally to other activities, but cannot be used to infer population trends. Long-term trapping data have been used to estimate population trends for various species. However, trapping returns are strongly influenced by trapper effort, which varies between years, and therefore may not accurately reflect population trends. Another important problem is that trapping records of many States did not differentiate between bobcats and lynx, referring to both as "lynxcats." Overall, the available data are too incomplete to infer much beyond simple occurrence and distribution of lynx in the contiguous United States (McKelvey et al. 2000b). Lynx populations in the contiguous United States occur at the southern periphery of a metapopulation whose core is located in the northern boreal forest of central Canada (McCord and Cardoza 1982; Quinn and Parker 1987; McKelvey et al. 2000a). Lynx population dynamics may emanate from the core to the periphery, as evidenced by a lagged correlation of lynx trap records and observations (McKelvey et al. 2000b; Mowat et al. 2000). In the Great Lakes Geographic Area, population dynamics in recent decades appear to be strongly driven by immigration from Canada (McKelvey et al. 2000b). In other areas and time periods, however, it is not known to what extent the correlation is due to immigration from Canada. population responses to the same factors controlling northern populations. or a combination of the two. We suspect that some areas in the contiguous United States naturally act as sources of ly-rix (recruitment is -''neater than mortality) that are able to disperse and potentially colonize other patches (-McKel,, ev er al. 2000x). Other areas may function as sirs. wl ere lynx mortality is is L-reater than recruitment and lynx are lost fi-om the ov erall population. Sink habitats are most likely those places on the periphery of the southern boreal forest where habitat becomes more 0