Limitation of Collared Lemming Population Growth at Low Densities by Predation Mortality

Abstract

A. 1995. Limitation of collared lemming population growth at low densities by predation mortality.-Oikos 73: 387-398. Populations of the collared lemming (Dicrostonyx kilangmiutak) and the tundra vole (Microtus oeconomus) have been at consistently low densities, and non-cyclic, at Pearce Point, Northwest Territories, Canada, for six yr. In most summers population densities decline, or only increase marginally, despite ongoing reproduction. We investigated the hypothesis that predation mortality is sufficient and necessary to curtail lemming population growth in summer. To test predictions of the hypothesis, we compared lemming demography, using mark-recapture and radiotelemetry, on a population from which predators were excluded (PE), using a perimeter fence and aerial mesh of nylon (11.4 ha), with demographies of three control populations (18-25 ha). Predation was the proximate cause of the majority of adult and neo-natal mortality, and was not replaced in a compensatory fashion by any other mortality factor in the PE. Significantly fewer adult lemmings died in the PE, and consequently survival inside the PE was significantly enhanced. Recruitment of juvenile lemmings to the adult population was significantly higher in the PE on a per unit area basis. The lemming population in PE followed a significantly different trajectory than the control populations in 1990 and 1991, remaining fairly stable while controls declined. However, the protected population did not grow, apparently because of juvenile dispersal: telemetered juveniles dispersed at an average rate of 53 m/d within the first ten d after weaning. We believe that the protected area was too small to encompass such dispersal, and that emigrants were not replaced by immigrating juveniles since the latter faced heavy mortality outside the exclosure. In 1992, numbers on PE and all controls grew, in conjunction with a regional absence of rough-legged hawks (Buteo lagopus) and a scarcity of red foxes (Vulpes vulpes), the two principal microtine predators. Tundra vole population growth was also limited by predation mortality, but to a lesser extent. We conclude that predation mortality is sufficient and necessary to limit summer population growth in these microtine species.

Of lemmings and snowshoe hares: the ecology of northern Canada

“…Two attempts have been made to reduce predation on lemming populations by fencing out predators. Reid et al [31] fenced 11 ha of tundra with a perimeter fence and an aerial These data are discussed in more detail in Krebs et al [27].…”

“…Infanticide in the field is very difficult to detect. The sole estimate of infanticide losses in field populations of collared lemmings from Reid et al [31] ranged from 0 to 5 per cent for a lowdensity population in which most losses of nestlings (43-70% lost) were due to predation. Whether a similar result would occur at higher lemming densities is not known.…”

“…Reproduction is increased by both winter breeding and an earlier age at sexual maturity and could be reduced by food shortage [30]. Mortality can be increased by predation losses and infanticide [31]. All of these processes tend to be delayed density dependent and we seem to have two options.…”

Synchrony in lemming and vole populations in the Canadian Arctic

“…First, we (C.J.K., A.J.K., S.G.) surveyed island and mainland sites in the western Canadian Arctic and central Arctic from 1987 to 2000. Our western Arctic surveys arose from our intensive research on the collared lemming (Dicrostonyx groenlandicus) at Pearce Point (Reid et al 1995). In a typical year we surveyed five sites on both sides of the Mackenzie River from Horton River, Northwest Territories (N.W.T.…”

Predator population depending on lemming cycles

“…The periodicity of the process can be regulated from quasi-periodic process to random pulse process. 8 Specifically, experimental data of lemming populations shows fairly high periodicity with cycles, 9 absence of regularity with random pulses, 10,11 and something intermediate between these extreme cases (see Fig. 2 of Ref.…”