Influence of visual information on sniffing behavior in a routinely trichromatic primate

Most catarrhine primates are considered to be strongly visually oriented animals, obtaining information about conspecifics and their environment from a diversity of visual cues. Other sensory modalities may provide information that is redundant and/or complimentary to visual cues. When cues from multiple sensory modalities are available, these may reinforce or suppress each other, as shown in a range of taxa from insects to humans. In the present study, we tested how the presence and ambiguity of visual information affects the use of olfactory cues when exploring food and non-food items in semi-free ranging Barbary macaques at Affenberg Salem, Germany. In experiment 1, we presented monkeys with pipes containing food (peanuts, popcorn), non-food (stones, feces) or no items. The ends of the pipes were either transparent or opaque, and we assessed whether animals looked, sniffed and/or grabbed into the pipes depending on visibility of the contents. In experiment 2, we manipulated the visual appearance of familiar food items (popcorn) with food colorant and scored if monkeys sniffed at and/or ate the popcorn depending on whether it was uncolored or dyed. In both experiments, the available visual information modulated sniffing behavior. Both visual as well as olfactory information further affected, whether or not monkeys attempted to retrieve the items from the pipes in experiment 1, while data were insufficient to assess this in experiment 2. Hence, reliance on the olfactory sense was modulated by the available visual information, emphasizing the interplay between different sensory modalities for obtaining information about the environment.多数狭鼻猴类（catarrhine primates）被视作高度依赖视觉的动物，能够通过多样化的视觉线索获取同种个体及其生存环境的相关信息。其他感官模态所提供的信息，既可能与视觉线索存在冗余，也可对视觉信息形成补充。当多感官模态的线索同时可用时，这些线索可彼此强化或相互抑制，这一现象已在从昆虫到人类的诸多类群中得到验证。本研究以德国Affenberg Salem半自由放养的巴巴利猕猴（Barbary macaques）为研究对象，探究视觉信息的存在性与模糊性对其探索食物与非食物物品时嗅觉线索使用行为的影响。实验1中，我们向猕猴提供三类管道：内部装有食物（花生、爆米花）、非食物（石块、粪便）或空管。管道端口分为透明与不透明两种类型，我们将根据内容物的可视性，评估猕猴是否会对管道进行观察、嗅探及/或抓探操作。实验2中，我们通过食用色素改变熟悉食物（爆米花）的外观，并根据爆米花是否着色，记录猕猴对其进行嗅探及/或取食的情况。两项实验均表明，可获取的视觉信息会调控猕猴的嗅探行为。在实验1中，视觉与嗅觉信息均会进一步影响猕猴是否尝试从管道中取回物品；而实验2中因数据不足，无法对该效应进行评估。综上，猕猴对嗅觉的依赖程度受可获取的视觉信息调控，这凸显了不同感官模态在获取环境信息过程中的相互作用。