Pulsed resources and the resource-prediction strategy: a field-test using a 36-year study of small mammals

Pulsed resource environments are known for their marked variations in resource availability over space and time. Animals living in such environments usually increase reproduction after resources become available. Some small mammal populations, however, may use environmental cues that precede large crops of seeds (e.g. pollen, flowers, unripe seeds) to ‘predict' mast-seeding events and reproduce in advance. In other words, these populations exhibit a resource-prediction strategy based on future fitness prospects. Habitat selection might play a key role in the resource-prediction strategy, but our understanding of habitat selection in pulsed resource environments is extremely limited. We used a 36-year dataset on small mammal trapping and seed availability collected in Maine (USA) to test if American red squirrels Tamiasciurus hudsonicus, eastern chipmunks Tamias striatus, white-footed mice Peromyscus leucopus and southern red-backed voles Myodes gapperi select habitats based on upcoming resources and examine the consequences to individual fitness. Small mammal trapping was conducted in summer before seeds were available, thus trapping occurred when only the cues of an upcoming mast event were available. Using home-range estimations and capture data, we performed resource selection analyses to assess if individuals select habitat to maximize future resource acquisitions. Using capture–mark–recapture models, we also estimated individual survival (a proxy for fitness). Our results do not support habitat selection as a mechanism underlying the resource-prediction hypothesis, indicating that individuals do not select habitats based on the upcoming seed availability. Nevertheless, we found that white-footed mice with home ranges in areas characterized by a greater quantity of white oak acorns have up to a 15% higher survival rate. Our empirical study advances the understanding of predator response to pulsed resources by not supporting a key mechanism thought to underpin the anticipatory responses that have been observed in many ecosystems worldwide.