Predation as a probable mechanism relating winter weather to population dynamics in a North American porcupine population

Abstract

An abundance index of an eastern Quebec population of North American porcupines (Erethizon dorsatum) has cycled with superimposed periodicities of 11 and 22 years from 1868 to 2000. This cycle closely followed 11-and 22-year cycles in solar irradiance and local weather (e.g., winter precipitation and spring temperature), generating the hypothesis that solar activity may affect porcupine abundance through effects on local weather. We investigated the mechanisms linking porcupine abundance to local weather conditions using a 6-year study (2000)(2001)(2002)(2003)(2004)(2005) involving individual mark-recapture, radio tracking, seasonal survival analyses and identification of mortality causes. Summer (May-August) survival was high and constant over the study period, whereas winter (AugustMay) survival was lower and varied during the duration of our study. Variations in local winter precipitation explained 89% of the variation in winter survival. Porcupine predation rates appeared strongly related to snow conditions; 95% of depredated porcupines were killed when snow was covering the ground, and predation rates were higher in years with increased winter precipitation. Our data thus support the hypothesis that changes in predation rates under different snow conditions were the mechanism relating climate to porcupine population dynamics, via modifications of the local predator-prey interactions and impacts on porcupine winter survival. Our study adds to the growing body of evidence supporting an effect of climate on predator-prey processes. Also, it identifies one possible mechanism involved in the relationship between solar irradiance and porcupine population cycles observed at this study site over a 130-year period.

Population dynamics of a northern‐adapted mammal: disentangling the influence of predation and climate change

“…Although, porcupines in the Great Basin Desert experienced nutritional limitation during winter, the relatively more moderate winter conditions likely exerted only a weak influence on survivorship. Our findings are corroborated by those from an analogous system with similar climatic patterns; Mabille et al (2010) found that winter precipitation modulated predatory influence on a porcupine population in southern Canada by altering snow conditions, which drove adult survivorship.…”

Environmental variation as a driver of predator‐prey interactions

“…While previous studies have usually dealt with determining the effect of climatic conditions on habitat selection (Dussault et al 2005, Hansen et al 2010, Stahlschmidt et al 2011 or, directly, on vulnerability to be predated (Stenseth et al 2004, Wikenros et al 2009, Mabille et al 2010, our approach allowed us to get a better insight into the behavioral mechanism indirectly linking environmental drivers to predation risk.…”

Behavioural responses of wintering porcupines to their heterogeneous thermal environment

“…However, predator avoidance may also lead animals to reduce their activities (Lima & Dill, 1990). Porcupines suffered high predation rates from fishers (Martes pennanti) during our study, and predation was linked to snow cover (Mabille, Descamps & Berteaux, 2010), probably because porcupines have short limbs and are thus vulnerable to predators when there is snow. In fact, porcupines spent less time outside of the den and had shorter activity bouts when snow penetrability was high, which may represent behavioural responses to increased predation risk.…”

“…Thermal conditions measured with T ref ( fragmented by abandoned and cultivated fields and characterized by a rugged topography, abundance of natural rock dens, and a mixed-boreal forest. The study population has been monitored each summer since 2000 and sometimes reached a high density (Mabille, Descamps & Berteaux, 2010). The population was at medium density and comprised about 40 individually marked porcupines in winter 2004 (see Berteaux, Klvana & Trudeau, 2005 for details on individual monitoring).…”