Data from: Primates adjust movement strategies due to changing food availability

Animals are hypothesized to search their environments in predictable ways depending on the distribution of resources. Evenly distributed foods are thought to be best exploited with random Brownian movements; while foods that are patchy or unevenly distributed require non-Brownian strategies, such as Lévy walks. Thus, when food distribution changes due to seasonal variation, animals should show concomitant changes in their search strategies. We examined this issue in six monkey species from Africa and Mexico: three frugivores and three folivores. We hypothesized that the more patchily distributed fruit would result in frugivores showing more levy-like patterns of motion, while folivores, with their more homogenous food supply, would show Brownian patterns of motion. At least three and up to five of six species conformed to the overall movement pattern predicted by their primary dietary item. For folivorous black howler monkeys (Alouatta pigra), ursine colobus (Colobus vellerosus), and red colobus (Procolobus rufomitratus), Brownian movement was supported or could not be ruled-out. Two frugivores (spider monkeys, Ateles geoffroyi yucatanensis, and grey-cheeked mangabeys, Lophocebus albigena) showed Lévy walks, as predicted, but frugivorous vervet monkeys (Chlorocebus pygerythrus) showed a Brownian walk. Additionally, we test whether seasonal variation in the spatial availability of food support environmentally driven changes in movement patterns. Four of five species tested for seasonal variation showed adjustments in their search strategies between the rainy and dry seasons. This study provides support for the notion that food distribution determines search strategies and that animal movement patterns are flexible, mirroring changes in the environment.

已有假说认为，动物会根据资源分布情况，以可预测的方式探索其生存环境。学界普遍认为，对于均匀分布的食物，动物可通过随机布朗运动（Brownian movement）实现最优觅食；而对于斑块状或非均匀分布的食物，则需采用非布朗运动策略，例如利维行走（Lévy walks）。因此，当食物分布因季节变化而改变时，动物的觅食策略也应随之发生相应调整。为此，我们针对来自非洲与墨西哥的6种灵长类动物展开研究，其中3种为食果动物（frugivore），另外3种为食叶动物（folivore）。我们提出假说：由于果实的分布斑块性更强，食果动物的运动模式应更接近利维行走；而食叶动物的食物供应更为均匀，其运动模式则应符合布朗运动。在6个物种中，至少有3种、至多有5种符合其主要食性对应的运动模式预测结果。对于食叶的黑吼猴（Alouatta pigra）、乌叶猴（Colobus vellerosus）以及红疣猴（Procolobus rufomitratus），其运动模式符合布朗运动假说，或无法排除布朗运动的可能性。两种食果动物——蜘蛛猴（Ateles geoffroyi yucatanensis）与灰颊白眉猴（Lophocebus albigena）的运动模式正如预期般呈现利维行走，但食果的黑长尾猴（Chlorocebus pygerythrus）却表现出布朗运动模式。此外，我们还验证了食物空间可获得性的季节变化是否会驱动动物运动模式随环境改变。在针对季节变化展开测试的5个物种中，有4个物种在雨季与旱季之间调整了其觅食策略。本研究为"食物分布决定动物觅食策略，且动物运动模式具有灵活性、可响应环境变化"这一观点提供了实证支持。