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

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.

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Related in: MedlinePlus

Age‐structured differences in isotopic niche breadth (SEA) of lynx during marginal environmental conditions when snowshoe hare densities and lynx recruitment were low (red), and during good environmental conditions when snowshoe hare densities and lynx recruitment were high (black) for A) juvenile lynx, B) yearling lynx, C) subadult lynx, and D) adult lynx. SEA is the standard ellipse area.
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ece32115-fig-0002: Age‐structured differences in isotopic niche breadth (SEA) of lynx during marginal environmental conditions when snowshoe hare densities and lynx recruitment were low (red), and during good environmental conditions when snowshoe hare densities and lynx recruitment were high (black) for A) juvenile lynx, B) yearling lynx, C) subadult lynx, and D) adult lynx. SEA is the standard ellipse area.

Mentions: Stable isotope ratios and SEAc estimates of lynx grouped by environmental condition and age class are presented in Figure 2. Diet breadth estimates (SEAc) of cohorts during good years were juveniles = 0.64‰2, yearlings = 0.64‰2, subadults = 0.52‰2, and adults = 0.62‰2. Diet breadth estimates (SEAc) of cohorts during marginal years were juveniles = 0.59‰2, yearlings = 1.22‰2, subadults = 1.12‰2, and adults = 0.61‰2. The global split plot model of diet breadth fit better than simpler variations (Table 4). Diet breadth of yearlings expanded when environmental condition declined, but juveniles, subadults, and adults maintained largely similar diets across environmental conditions (Fig. 3). The coefficient for subadult niche expansion under marginal environmental conditions may suggest a tendency toward niche expansion, but confidence intervals of our model overlap zero (Fig. 3). Random intercepts for the global model were 1998 = 0.60, 1999 = 0.50, 2000 = 0.72, and 2001 = 0.37. Model fit improved considerably with addition of random effects (Rm2 = 0.37 and Rc2 = 0.77). Visual inspection of fitted values and residuals indicated compliance with assumptions of normality and homoscedasticity.


Demographic differences in diet breadth of Canada lynx during a fluctuation in prey availability
Age‐structured differences in isotopic niche breadth (SEA) of lynx during marginal environmental conditions when snowshoe hare densities and lynx recruitment were low (red), and during good environmental conditions when snowshoe hare densities and lynx recruitment were high (black) for A) juvenile lynx, B) yearling lynx, C) subadult lynx, and D) adult lynx. SEA is the standard ellipse area.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016656&req=5

ece32115-fig-0002: Age‐structured differences in isotopic niche breadth (SEA) of lynx during marginal environmental conditions when snowshoe hare densities and lynx recruitment were low (red), and during good environmental conditions when snowshoe hare densities and lynx recruitment were high (black) for A) juvenile lynx, B) yearling lynx, C) subadult lynx, and D) adult lynx. SEA is the standard ellipse area.
Mentions: Stable isotope ratios and SEAc estimates of lynx grouped by environmental condition and age class are presented in Figure 2. Diet breadth estimates (SEAc) of cohorts during good years were juveniles = 0.64‰2, yearlings = 0.64‰2, subadults = 0.52‰2, and adults = 0.62‰2. Diet breadth estimates (SEAc) of cohorts during marginal years were juveniles = 0.59‰2, yearlings = 1.22‰2, subadults = 1.12‰2, and adults = 0.61‰2. The global split plot model of diet breadth fit better than simpler variations (Table 4). Diet breadth of yearlings expanded when environmental condition declined, but juveniles, subadults, and adults maintained largely similar diets across environmental conditions (Fig. 3). The coefficient for subadult niche expansion under marginal environmental conditions may suggest a tendency toward niche expansion, but confidence intervals of our model overlap zero (Fig. 3). Random intercepts for the global model were 1998 = 0.60, 1999 = 0.50, 2000 = 0.72, and 2001 = 0.37. Model fit improved considerably with addition of random effects (Rm2 = 0.37 and Rc2 = 0.77). Visual inspection of fitted values and residuals indicated compliance with assumptions of normality and homoscedasticity.

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.


Related in: MedlinePlus