Abiotic conditions mediate intraguild interactions between mammalian carnivores


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Abstract

Intraguild (IG) interactions are common among mammalian carnivores, can include intraguild predation (IGP) and interspecific killing (IK), and are often asymmetrical, where a larger more dominant species (IGpredator) kills a smaller one (IGprey). According to ecological theory, the potential for an IGpredator and IGprey to coexist depends on whether the direct consumptive benefits for the IGpredator are substantial (IGP) or insignificant (IK), the extent to which the IGprey is the superior exploitative competitor on shared prey resources, and overall ecosystem productivity.We used resource selection models and spatially explicit age and harvest data for two closely related mesopredators that engage in IG interactions, American martens (Martes americana; IGprey) and fishers (Pekania pennanti; IGpredator), to identify drivers of distributions, delineate areas of sympatry and allopatry, and explore the role of an apex predator (coyote; Canis latrans) on these interactions.Model selection revealed that fisher use of this landscape was strongly influenced by late winter abiotic conditions, but other bottom-up (forest composition) and top-down (coyote abundance) factors also influenced their distribution. Overall, fisher probability of use was higher where late winter temperatures were warmer, snowpack was deeper, and measures of productivity were greater. Martens were constrained to areas of the landscape where the probability of fisher use, coyote abundance, and productivity were low and selected for forest conditions that presumably maximized prey availability. Marten age data indicated an increased proportion of juveniles outside of the predicted area of sympatry, suggesting that few animals survived >1.5 years in this area that supported higher densities of fishers and coyotes.Consistent with asymmetrical IG interaction theory, the IGpredator (fishers and, to a lesser degree, coyotes) competitively excluded the IGprey (martens) from more productive, milder temperature habitats, whereas IGpredators and IGprey coexisted in low productivity environments, where a combination of abiotic and biotic conditions enabled the IGprey to be the superior exploitative competitor.In this paper, the authors investigate biotic and abiotic drivers of distributions for two closely related mesopredators that engage in intraguild interactions, American martens and fishers, and explore the role of an apex predator (coyote) on these interactions. They test the dominant hypothesis on the mediating effect of snow, demonstrate patterns of competitive exclusion and coexistence that are consistent with theory and discuss the role of productivity in shaping these patterns.

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