Should I stay or should I go? Causes and consequences of intraspecific variation in site fidelity

Site fidelity, the tendency to return to previously visited locations, is common across a wide range of taxa and ecosystems. Site fidelity can benefit animals by improving foraging efficiency, reducing movement costs, and increasing reproductive success. Nevertheless, considerable variation exists within and among species in the nature and magnitude of site fidelity, and the mechanisms underpinning this variation are poorly understood. One hypothesis for explaining variation in site fidelity suggests that in predictable resource landscapes, fidelity should be conditional on prior reproductive success (win-stay, lose-switch). Alternatively, animals occupying less predictable resource landscapes should make greater use of cues from their current environment and site fidelity should scale inversely with the magnitude of environmental heterogeneity.

We investigated the causes (e.g., prior reproductive success, foodscape heterogeneity) and consequences (e.g., nutritional condition, neonate survival) of intraspecific variation in site fidelity during spring and summer among three bighorn sheep (Ovis canadensis) populations occupying a low-elevation grassland and two alpine ecosystems. We used distance-based metrics to quantify site fidelity at inter-annual, inter-month and inter-week scales to better understand the behavioral strategies employed by bighorn sheep to mitigate environmental variation and optimize foraging opportunities.

Site fidelity varied considerably among study areas and across temporal scales. Prior reproductive success was not an important predictor of site fidelity by bighorn sheep, and instead, site fidelity appeared to be influenced by quality and predictability of forage resources within individual home ranges. Despite consistency of this effect, however, we found little evidence that site fidelity improved nutritional condition of female sheep or neonate survival to 120 days.

Our results generally support the notion that environmental conditions shaped the strength of site fidelity across temporal scales. Yet, the benefits of site fidelity were limited, at least based on the performance metrics we measured. Continuing to parse the complex mechanisms underpinning variation in site fidelity will shed important light on the capacity of animals to adjust to an unpredictable and changing environment.