Data from: Seasonal body mass dynamics mediate life history trade-offs in a mammalian hibernator

We used 8753 body mass records from 3351 individually marked, free-ranging northern Idaho ground squirrels (<i>Urocitellus brunneus</i>) -- a federally threatened hibernating mammal -- to meet three research objectives: (1) document seasonal changes in body mass across the active season by squirrel sex, age class, and reproductive status, (2) test a suite of ecological hypothesis to explain spatiotemporal variation in squirrel body mass, and (3) document the effect of pre-hibernation body condition on squirrel overwinter survival. We collected the data across 12 years (2013-2024) at 16 study sites that were spread across the species' limited range in western Idaho, USA.The dataset archived here includes R code fitting linear mixed effects models of northern Idaho ground squirrel body mass. One .R file models our complete body mass dataset. Another models body mass of female squirrels for which reproductive status was known. The dataset also includes R code fitting generalized linear mixed effects models of annual recapture probability for northern Idaho ground squirrels. Lastly, the dataset includes two .R files plotting model-based predictions of seasonal mass gain and recapture rates. The remainder of the dataset includes the necessary .csv files to input into the .R files. The NIDGS_Mass_LMM and NIDGS_Recap_GLMM files also serve as the raw data files for the study as they include the complete datasets analyzed and we modeled the raw data.