Sampled states of the hibernator’s year were defined by body temperature.

<p>Samples were collected from 7 states. Summer (SA, n = 6) and spring (SpC, n = 5) ground squirrels represented the homeothermic portions of the annual cycle. Winter states representing the heterothermic period (blue box, expanded for clarity) were collected throughout the winter hibernation season and were defined as follows by body temperature telemetry: entering torpor (Ent, n = 7) at 27°C>T_b >23°C; late torpor (LT, n = 7) at 80–95% previous bout duration; early arousing (EAr, n = 6) at 7°Cb <12.8°C; and 3–4 hours after T_b stabilized in inter-bout arousal (IBA, n = 5) period. Samples were also collected during the highly variable Fall transition period (FT, n = 12) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071627#pone.0071627-Russell1" target="_blank">[16]</a>. Colors representing each state are used throughout.