Cryptic behaviour and activity cycles of a small mammal keystone species revealed through accelerometry: a case study of Merriam's kangaroo rats

Kangaroo rats are among the most abundant vertebrates in many terrestrial ecosystems in Western North America and are considered both keystone species and ecosystem engineers, providing linkages to other species as both consumers and resources. We developed an integrative miniaturized animal-borne accelerometry/radiotelemetry approach to quantify the cryptic behaviour and activity cycles of kangaroo rats. Our study highlights a method of attachment and retrieval for deploying accelerometers, a non-disruptive method of gathering observational validation datasets for acceleration data on free-ranging nocturnal small mammals, and a case study for analyzing how behavioural patterns relate to abiotic factors. We found that Merriam's kangaroo rats are only active during later light phases of the night, show no reduction in activity or foraging associated with moonlight (indicating that kangaroo rats are actually more lunarphilic than lunarphobic) and increased foraging effort on more humid nights (most likely as a mechanism to avoid cutaneous water loss). Our work represents the first continuous detailed quantitative description of fine-scale behavioural activity budgets in kangaroo rats and lays out a general framework of how to use miniaturized biologging devices to examine behavioural responses of nocturnal small mammals to environmental factors.

更格卢鼠（Kangaroo rat）是北美西部众多陆地生态系统中最为丰富的脊椎动物类群之一，同时被认定为关键物种与生态系统工程师，既作为消费者又作为资源，为其他物种间搭建了生态联系纽带。本研究开发了一套集成化的微型动物佩戴式加速度计（accelerometer）与无线电遥测（radiotelemetry）技术方案，用于量化更格卢鼠的隐秘行为与活动周期。本研究不仅提出了加速度计的佩戴与回收方法，还建立了针对自由活动夜行性小型哺乳动物的加速度数据无干扰观测验证方案，并提供了分析行为模式与非生物因子关联关系的案例研究框架。研究发现，梅里亚姆更格卢鼠仅在夜间后段光照时段活动，并未因月光出现活动或觅食行为的减少——这表明更格卢鼠实际上更偏向趋月性（lunarphilic）而非避月性（lunarphobic），且在湿度更高的夜晚会增加觅食投入，这极有可能是为避免皮肤水分流失的适应策略。本研究首次对更格卢鼠的精细尺度行为活动预算进行了连续、详尽的定量描述，并构建了一套通用框架，可用于借助微型生物记录（biologging）设备探究夜行性小型哺乳动物的行为对环境因子的响应机制。