In mammals, colouration patterns are often related to concealment, intraspecific communication including aposematic signals, and physiological adaptations. Slow lorises (Nycticebus spp.) are arboreal primates native to Southeast Asia that are starkly coloured, highly territorial, regularly enter torpor, and are notably one of only seven mammal taxa that possess venom. All slow loris species display a contrasting stripe that runs cranial-caudally along the median sagittal plane of the dorsum. We examine if these dorsal markings facilitate background matching, seasonal adaptations and intraspecific signalling. We analysed 195 images of the dorsal region of 60 Javan slow loris individuals (Nycticebus javanicus) from Java, Indonesia. These are included in the dataset here. We extracted greyscale RGB values dorsal pelage using ImageJ software and calculated contrast ratios between dorsal stripe and adjacent pelage in eight regions. We assessed through Generalised Linear Mixed Models if the contrast ratio varied with sex, age, and seasonality. We also examined if higher contrast was related to more aggressive behaviour or increased terrestrial movement. We found that the dorsal stripe of N. javanicus changed seasonally, being longer and more contrasting in the wet season, during which time lorises significantly increased their ground use. Stripes were most contrasting in younger individuals of dispersal age that were also the most aggressive during capture. The dorsal stripe became less contrasting as a loris aged. A longer stripe when ground use is more frequent can be related to disruptive colouration. A darker anterior region by younger lorises with less fighting experience may allow them to appear larger and fiercer. We provide evidence that the dorsum of a cryptic species can have multimodal signals related to concealment, intraspecific communication, and physiological adaptations.
Permanent link to this resource: https://doi.org/10.24384/p633-qk55
(Oxford Brookes University)
Faculty of Humanities and Social Sciences
Published by Oxford Brookes University
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