Data from: A case for considering individual variation in diel activity patterns

There is a growing recognition of the role of individual variation in patterns emerging at higher levels of biological organization. Despite the importance of the temporal configuration of ecological processes and patterns, intraspecific individual variation in diel activity patterns is almost never accounted for in behavioral studies at the population level. We used individual-based monitoring data from 98 GPS-collared brown bears in Scandinavia to estimate diel activity patterns before the fall hunting season. We extracted 7 activity measures related to timing and regularity of activity from individual activity profiles. We then used multivariate analysis to test for the existence of distinct activity tactics and their environmental determinants, followed by generalized linear regression to estimate the extent of within-individual repeatability of activity tactics. We detected 4 distinct activity tactics, with a high degree of individual fidelity to a given tactic. Demographic factors, availability of key foraging habitat, and human disturbance were important determinants of activity tactics. Younger individuals and those with higher bear and road densities within their home range were more nocturnal and more likely to rest during the day. Good foraging habitat and increasing age led to more diurnal activity patterns and nocturnal resting periods. We did not find evidence of diel activity tactics influencing survival during the subsequent hunting season. We conclude that individual variation in activity deserves greater attention than it currently receives, as it may help account for individual heterogeneity in fitness and could facilitate within-population niche partitioning that can have population- or community-level consequences.

学界日益认识到，个体变异在更高层级生物组织所呈现的模式中发挥着关键作用。尽管生态过程与模式的时间配置至关重要，但在种群水平的行为学研究中，几乎从未考虑过种内个体间的昼夜活动模式（diel activity patterns）变异。本研究利用斯堪的纳维亚地区98只佩戴GPS项圈（GPS collar）的棕熊的基于个体的监测数据，对秋季狩猎季前的棕熊昼夜活动模式进行了估算。本研究从个体活动谱中提取了7项与活动时机及规律性相关的活动特征指标。随后，本研究通过多变量分析（multivariate analysis）检验了差异化活动策略的存在性及其环境驱动因素，并借助广义线性回归（generalized linear regression）估算了活动策略在个体内的可重复程度。研究共识别出4种差异化的活动策略，且个体对其所采用的活动策略具有高度的固守性。种群统计特征、关键觅食栖息地的可获得性以及人类干扰，均是影响活动策略的重要驱动因素。年龄较小的个体，以及家域（home range）内棕熊密度与道路密度更高的个体，表现出更强的夜行性，且更倾向于在日间休息。优质的觅食栖息地与年龄增长则会促使个体呈现更多的昼行性活动模式，并在夜间休息。本研究未发现证据表明，昼夜活动策略会对后续狩猎季内的个体存活率产生影响。综上，活动模式的个体变异值得受到比当下更多的关注：该变异或可解释适合度（fitness）的个体异质性，且有助于推动种群内的生态位分化（niche partitioning），进而可能对种群乃至群落水平产生影响。