Sklíba Jan, Lövy Matěj, Hrouzková Ema, Kott Ondřej, Okrouhlík Jan, Sumbera Radim
Department of Zoology, Faculty of Science, University of South Bohemia, Cˇeské Budeˇjovice, Czech Republic.
Department of Zoology, Faculty of Science, University of South Bohemia, Cˇeské Budeˇjovice, Czech Republic
J Biol Rhythms. 2014 Jun;29(3):203-214. doi: 10.1177/0748730414526358. Epub 2014 Jun 10.
Predictable daily activity patterns have been detected repeatedly even in mammals living in stable environments, as is the case for subterranean rodents. Whereas studies on activity of these rodents under laboratory conditions almost exclusively have concerned themselves with the influence of light, many field studies have revealed signs of an association between the activity pattern and daily fluctuations of temperature under the ground. This would assume that behavioral thermoregulation is probably involved. The only exceptions to the relationship between temperature and activity are 2 eusocial mole-rats of the genus Fukomys (Bathyergidae, Rodentia), which indicates that activity patterns could be affected also by social cues. To better understand how social and environmental factors influence the activity pattern in a eusocial mole-rat, we monitored the outside-nest activity in another species of this genus, the Ansell's mole-rat (Fukomys anselli), which has a relatively small body mass, high conductance, and more superficially situated burrows. Its daily activity had 1 prominent peak (around 1400 h), and it was tightly correlated with the temperature measured at depth of foraging burrows. Since F. anselli has high thermoregulatory requirements to maintain stable body temperature below the lower critical temperature, we conclude that the observed pattern is probably the result of minimizing the cost of thermoregulation. There were no significant differences in the daily activity patterns of breeding males and females and nonbreeders. Members of the same family group tended to have more similar activity patterns, but consistent activity synchronization between individuals was not proven. From the comparison of available data on all subterranean rodents, we assume that social cues in communally nesting mole-rats may disrupt (mask) temperature-related daily activity rhythms but probably only if the additional cost of thermoregulation is not too high, as it likely is in the Ansell's mole-rat.
即使在生活于稳定环境中的哺乳动物身上，也反复检测到了可预测的日常活动模式，地下啮齿动物就是如此。尽管在实验室条件下对这些啮齿动物活动的研究几乎都只关注光照的影响，但许多野外研究已经揭示了活动模式与地下温度日波动之间存在关联的迹象。这意味着行为体温调节可能也参与其中。温度与活动之间关系的唯一例外是2种裸鼹形鼠属（掘土啮齿科，啮齿目）的群居鼹形鼠，这表明活动模式也可能受到社会线索的影响。为了更好地理解社会和环境因素如何影响群居鼹形鼠的活动模式，我们监测了该属另一种鼹形鼠——安塞尔氏鼹形鼠（Fukomys anselli）的巢外活动，这种鼹形鼠体重相对较小、导热性高且洞穴位置较浅。其日常活动有1个明显的高峰（约14:00），并且与觅食洞穴深度处测得的温度紧密相关。由于安塞尔氏鼹形鼠在低于下限临界温度时维持稳定体温有很高的体温调节需求，我们得出结论，观察到的模式可能是将体温调节成本降至最低的结果。繁殖期的雄性和雌性以及非繁殖个体的日常活动模式没有显著差异。同一家族群体的成员往往有更相似的活动模式，但并未证实个体之间存在一致的活动同步。从对所有地下啮齿动物现有数据的比较中，我们推测群居鼹形鼠的社会线索可能会扰乱（掩盖）与温度相关的日常活动节律，但可能只有在体温调节的额外成本不太高时才会如此，安塞尔氏鼹形鼠可能就是这种情况。
