Data from: The secret life of ground squirrels: accelerometry reveals sex-dependent plasticity in above-ground activity

The sexes differ in how and when they allocate energy towards reproduction, but how this influences phenotypic plasticity in daily activity patterns is unclear. Here, we use collar-mounted light loggers and triaxial accelerometers to examine factors that affect time spent above ground and overall dynamic body acceleration (ODBA), an index of activity-specific energy expenditure, across the active season of free-living, semi-fossorial arctic ground squirrels (Urocitellus parryii). We found high day-to-day variability in time spent above ground and ODBA with most of the variance explained by environmental conditions known to affect thermal exchange. In both years, females spent more time below ground compared with males during parturition and early lactation; however, this difference was fourfold larger in the second year, possibly, because females were in better body condition. Daily ODBA positively correlated with time spent above ground in both sexes, but females were more active per unit time above ground. Consequently, daily ODBA did not differ between the sexes when females were early in lactation, even though females were above ground three to six fewer hours each day. Further, on top of having the additional burden of milk production, ODBA data indicate females also had fragmented rest patterns and were more active during late lactation. Our results indicate that sex differences in reproductive requirements can have a substantial influence on activity patterns, but the size of this effect may be dependent on capital resources accrued during gestation.两性在繁殖能量分配的方式与时机上存在差异，但该差异如何影响日常活动模式的表型可塑性（phenotypic plasticity）仍尚不明确。本研究借助项圈式光照记录仪（collar-mounted light loggers）与三轴加速度计（triaxial accelerometers），针对野生半穴居北极地松鼠（Urocitellus parryii）的活动季，探究了影响其地表停留时长与整体动态身体加速度（overall dynamic body acceleration, ODBA）——一种反映活动特异性能量消耗的指标——的各类因素。研究发现，地表停留时长与ODBA均存在较高的日间变异性，且绝大多数变异可由已知影响热交换的环境条件所解释。在两年的观测周期内，雌性个体在分娩与哺乳早期的地下停留时长均长于雄性；但第二年的性别差异幅度达到了四倍之多，这可能是因为当年雌性的身体状况更佳。两性的每日ODBA均与地表停留时长呈正相关，但雌性在地表每单位时间内的活动强度更高。因此，即便雌性在哺乳早期的每日地表停留时长比雄性少3至6小时，二者的每日ODBA却并无显著差异。进一步而言，除了需要承担泌乳的额外生理负担外，ODBA监测数据还显示雌性在哺乳晚期的休息模式更为碎片化，且活动量更高。本研究结果表明，繁殖需求上的性别差异可对动物活动模式产生显著影响，而这种效应的强度可能取决于雌性在妊娠期间积累的身体资本资源。