Digital biodiversity datasets reveal breeding phenology and its drivers in a widespread North American mammal

Shifts in reproductive timing are among the most commonly documented
responses of organisms to global climate change. However, our knowledge of
these responses is biased towards taxa that are easily observable and
abundant in existing biodiversity data sets. Mammals are common subjects
in reproductive biology, but mammalian phenology and its drivers in the
wild remain poorly understood because many species are small, secretive,
or labor-intensive to monitor. We took an informatics-based approach to
reconstructing breeding phenology in the widespread North American deer
mouse (Peromyscus maniculatus) using individual-level reproductive
observations from digitized museum specimens and field censuses spanning
>100 years and >45 degrees of latitude. We reconstructed
female phenology in different regions and tested the importance of three
environmental variables (photoperiod, temperature, precipitation) as
breeding cues. Photoperiod and temperature were strong positive and
negative breeding cues, respectively, while precipitation was not a
significant predictor of breeding phenology. However, phenologies and the
use of environmental cues varied substantially among regions, and we found
evidence that these cueing repertoires are tuned to ecosystem-specific
limiting conditions. Our results reiterate the importance of ecological
context in optimizing reproduction and demonstrate how harmonization
across biodiversity data resources allows new insight into phenology and
its drivers in wild mammals.