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Demographic differences in diet breadth of Canada lynx during a fluctuation in prey availability

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ABSTRACT

Population dynamics of specialist carnivores are closely linked to prey availability, but the extent of variability in diet breadth of individual carnivores relative to natural variability in the abundance of their primary prey is not well understood. Canada lynx (Lynx canadensis) specialize on snowshoe hares (Lepus americanus) and exhibit cyclic fluctuations in abundance that lag 1–2 years behind those of snowshoe hares. Declining hare densities spur demographic changes in lynx, but it is unclear whether a corresponding increase in diet breadth occurs: (1) broadly across a lynx population; (2) only among individuals who are able to effectively switch to alternative prey; or (3) only among individuals who cannot capture sufficient primary prey. We measured stable isotope ratios of lynx muscle tissue spanning a cyclic increase and decline in hare density (1998–2001) in Fort Providence, NT, Canada. We found that lynx cohorts responded differently to hare population change, with yearling animals having broader diets at low hare densities, while adults and dependent juveniles maintained a constant diet through the initial decline in hare density. This result was consistent irrespective of lynx sex and indicates that yearling lynx likely are forced to adopt a broader diet when primary prey densities decline. Our results imply that select cohorts of specialist carnivores can exhibit high dietary plasticity in response to changes in primary prey abundance, prompting the need to determine whether increased diet breadth in young lynx is a successful strategy for surviving through periods of snowshoe hare scarcity. In this way, cohort‐specific niche expansion could strongly affect the dynamics of organisms exhibiting population cycles.

No MeSH data available.


A yearling Canada lynx (Lynx canadensis). Photograph credit: C.M. Burstahler.
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ece32115-fig-0001: A yearling Canada lynx (Lynx canadensis). Photograph credit: C.M. Burstahler.

Mentions: Canada lynx (Lynx canadensis) are specialist predators in a prey‐limited system, providing a useful model for examining effects of food limitation on diet breadth and its variability in a population (Fig. 1). Lynx in the core range exhibit population cycles following 1–2 years behind that of their preferred prey, snowshoe hare (Lepus americanus), which cycle in abundance every 9–10 years (Krebs et al. 2013). Lynx cycles have been attributed ultimately to changes in snowshoe hare density (Krebs et al. 2001) and proximately to changes in juvenile recruitment (Brand and Keith 1979; Mowat et al. 1996; Slough and Mowat 1996). Additionally, lynx can increase their use of alternative prey in their winter diets when hare densities decline (Brand et al. 1976; O'Donoghue et al. 1998a), meaning that the influence of primary prey can be dampened during periods of food shortage. During winter in the boreal forest, red squirrel (Tamiasciurus hudsonicus) comprise the greatest available alternative resource for lynx (Mowat et al. 2000), and ruffed grouse (Bonasa umbellus), small mammals (Peromyscus spp., Microtus spp.), and ungulate carrion also are consumed (Van Zyll de Jong 1966; Brand et al. 1976).


Demographic differences in diet breadth of Canada lynx during a fluctuation in prey availability
A yearling Canada lynx (Lynx canadensis). Photograph credit: C.M. Burstahler.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5016656&req=5

ece32115-fig-0001: A yearling Canada lynx (Lynx canadensis). Photograph credit: C.M. Burstahler.
Mentions: Canada lynx (Lynx canadensis) are specialist predators in a prey‐limited system, providing a useful model for examining effects of food limitation on diet breadth and its variability in a population (Fig. 1). Lynx in the core range exhibit population cycles following 1–2 years behind that of their preferred prey, snowshoe hare (Lepus americanus), which cycle in abundance every 9–10 years (Krebs et al. 2013). Lynx cycles have been attributed ultimately to changes in snowshoe hare density (Krebs et al. 2001) and proximately to changes in juvenile recruitment (Brand and Keith 1979; Mowat et al. 1996; Slough and Mowat 1996). Additionally, lynx can increase their use of alternative prey in their winter diets when hare densities decline (Brand et al. 1976; O'Donoghue et al. 1998a), meaning that the influence of primary prey can be dampened during periods of food shortage. During winter in the boreal forest, red squirrel (Tamiasciurus hudsonicus) comprise the greatest available alternative resource for lynx (Mowat et al. 2000), and ruffed grouse (Bonasa umbellus), small mammals (Peromyscus spp., Microtus spp.), and ungulate carrion also are consumed (Van Zyll de Jong 1966; Brand et al. 1976).

View Article: PubMed Central - PubMed

ABSTRACT

Population dynamics of specialist carnivores are closely linked to prey availability, but the extent of variability in diet breadth of individual carnivores relative to natural variability in the abundance of their primary prey is not well understood. Canada lynx (Lynx canadensis) specialize on snowshoe hares (Lepus americanus) and exhibit cyclic fluctuations in abundance that lag 1–2 years behind those of snowshoe hares. Declining hare densities spur demographic changes in lynx, but it is unclear whether a corresponding increase in diet breadth occurs: (1) broadly across a lynx population; (2) only among individuals who are able to effectively switch to alternative prey; or (3) only among individuals who cannot capture sufficient primary prey. We measured stable isotope ratios of lynx muscle tissue spanning a cyclic increase and decline in hare density (1998–2001) in Fort Providence, NT, Canada. We found that lynx cohorts responded differently to hare population change, with yearling animals having broader diets at low hare densities, while adults and dependent juveniles maintained a constant diet through the initial decline in hare density. This result was consistent irrespective of lynx sex and indicates that yearling lynx likely are forced to adopt a broader diet when primary prey densities decline. Our results imply that select cohorts of specialist carnivores can exhibit high dietary plasticity in response to changes in primary prey abundance, prompting the need to determine whether increased diet breadth in young lynx is a successful strategy for surviving through periods of snowshoe hare scarcity. In this way, cohort‐specific niche expansion could strongly affect the dynamics of organisms exhibiting population cycles.

No MeSH data available.