Unstable dynamics and population limitation in mountain hares

Abstract

The regular large-scale population fluctuations that characterize many species of northern vertebrates have fascinated ecologists since the time of Charles Elton. There is still, however, no clear consensus on what drives these fluctuations. Throughout their circumpolar distribution, mountain hares Lepus timidus show regular and at times dramatic changes in density. There are distinct differences in the nature, amplitude and periodicity of these fluctuations between regions and the reasons for these population fluctuations and the geographic differences remain largely unknown. In this review we synthesize knowledge on the factors that limit or regulate mountain hare populations across their range in an attempt to identify the drivers of unstable dynamics. Current knowledge of mountain hare population dynamics indicates that trophic interactions--either predator-prey or host-parasite--appear to be the major factor limiting populations and these interactions may contribute to the observed unstable dynamics. There is correlative and experimental evidence that some mountain hare populations in Fennoscandia are limited by predation and that predation may link hare and grouse cycles to microtine cycles. Predation is unlikely to be important in mountain hare populations in Scotland as most hares occur on sporting estates where predators are controlled, but this hypothesis remains to be experimentally tested. There is, however, emerging experimental evidence that some Scottish mountain hare populations are limited by parasites and that host-parasite interactions contribute to unstable dynamics. By contrast, there is little evidence from Fennoscandia that parasitism is of any importance to mountain hare population dynamics, although disease may cause periodic declines. Although severe weather and food limitation may interact to cause periodic high winter mortality there is little evidence that food availability limits mountain hare populations. There is a paucity of information concerning the factors limiting or regulating mountain hare populations in the Alps of Central Europe or in the tundra and taiga belts of Russia. Future research on mountain hare population dynamics should focus on the interactions between predation, parasitism and nutrition with stochastic factors such as climate and anthropogenic management including harvesting.

The effects of population density on the breeding performance of mountain hareLepus timidus

“…Rather, Hewson (1976) found that demographic parameters tended to be associated with a phase of population growth with low juvenile recruitment during the low phase, when population density was very low, and greatest juvenile recruitment during the increase phase as population density increased. Both these early studies support the results of our study despite differences in methodologies and some concerns over the provenance of the island populations used in Angerbjo¨rn's (1986) study (Newey et al 2007a).…”

Habitat selection and activity patterns in Alpine mountain hare (Lepus timidus varronis)

“…Panek 2009;Carlsson et al 2010). The importance of predator pressure on mountain hare densities, and behaviour are likely to vary in relation to densities of both prey and predator and with habitat structure (see also Hik 1995;Newey et al 2007). The short time-span of our study did not allow us to explore a possible relationship between variation in fox density and hare space and/or habitat use.…”

Long-term decline in a salt marsh hare population largely driven by bottom-up factors

“…Intensification of agricultural practices has resulted in loss of crop and landscape diversity, and as such is thought to be the main cause behind the decline of hares in agricultural landscapes (Edwards et al 2000;Smith et al 2005). Other factors may have contributed to the decline but have probably not influenced the long-term population trends (Haerer et al 2001;Frölich et al 2007), and these include increased predator densities (Lindstrom et al 1994;Schmidt et al 2004), intensive hunting (Avril et al 2012(Avril et al , 2014 and diseases (Flux et al 1990;Mitchell-Jones et al 1999;Newey et al 2007). Moreover, these factors probably do not operate in isolation but strongly interact with each other.…”