@article{f2390b7e783241268aab5ef5b08244df,
title = "External environmental conditions impact nocturnal activity levels in proboscis monkeys (Nasalis larvatus) living in Sabah, Malaysia",
abstract = "Recently, several diurnal nonhuman anthropoids have been identified displaying varying degrees of nocturnal activity, which can be influenced by activity “masking effects”—external events or conditions that suppress or trigger activity, temporarily altering normal activity patterns. Environmental masking characteristics include nocturnal temperature, rainfall, cloud cover, and moon brightness. Similarly, other ecological characteristics, including proximity to humans and predators and daytime activity, may also trigger or suppress nocturnal activity. Understanding the effects of external conditions on activity patterns is pertinent to effective species conservation. We investigated the presence of nocturnal activity and the influence of masking effects on the level of nocturnal activity displayed by wild proboscis monkeys (Nasalis larvatus) in Sabah, Malaysian Borneo. Dual-axis accelerometers were attached by collar to six male proboscis monkeys from different one-male, multi-female groups to record activity continuously (165–401 days each). We measured the monkeys' nocturnal and diurnal activity levels and investigated the effects of seven potential masking effects. Nocturnal activity was much lower than diurnal activity. Still, proboscis monkeys did display varying levels of nocturnal activity. Generalized linear mixed models identified higher nocturnal activity in the study individuals during nights with cooler temperatures, higher rainfall, and after higher diurnal activity. These three masking effects affected nocturnal activity levels during the observation period that informed our model, although they did not predict nocturnal activity outside of this period. While the generalizability of these results remains uncertain, this study highlights the utility of accelerometers in identifying activity patterns and masking effects that create variability in these patterns.",
keywords = "accelerometer, activity pattern, diurnal primates, masking effects, nocturnal activity, proboscis monkeys",
author = "Kooros, {Sophie J.} and Benoit Goossens and Sterck, {Elisabeth H.M.} and Richard Kenderdine and Malim, {Peter T.} and {Ramirez Saldivar}, {Diana A.} and Stark, {Danica J.}",
note = "Funding Information: We thank the Sabah Biodiversity Centre and the Sabah Wildlife Department for their permission and support of the project. The authors wish to thank the rangers of the Wildlife Health Unit (WHU) and the Wildlife Rescue Unit (WRU), and the research assistants at Danau Girang Field Centre (DGFC) for their efforts in collaring the animals and their consistent help throughout the study. The authors also greatly appreciate the financial support from Sime Darby Foundation, Ocean Park Conservation Foundation Hong Kong and Margot Marsh Biodiversity Foundation (PR12-12 and PR14-036). The authors thank Dr. Jorg Massen for discussions over the statistical components. We also thank the two reviewers for their valuable feedback on an earlier version of the manuscript. This paper contains modified Copernicus Climate Change Service information (2017). We thank the Copernicus Climate Change Service and all scientists involved in this project. The authors state that neither the European Commission or European Centre for Medium-Range Weather Forecasts (ECMWF) is responsible for any use that may be made of the Copernicus information or data it contains. We dedicate this paper to the memory of co-authors Dr. Diana Angelez Ramirez Saldivar and Mr. Peter Titol Malim who devoted their lives to the conservation of wildlife in Sabah. Funding Information: We thank the Sabah Biodiversity Centre and the Sabah Wildlife Department for their permission and support of the project. The authors wish to thank the rangers of the Wildlife Health Unit (WHU) and the Wildlife Rescue Unit (WRU), and the research assistants at Danau Girang Field Centre (DGFC) for their efforts in collaring the animals and their consistent help throughout the study. The authors also greatly appreciate the financial support from Sime Darby Foundation, Ocean Park Conservation Foundation Hong Kong and Margot Marsh Biodiversity Foundation (PR12‐12 and PR14‐036). The authors thank Dr. Jorg Massen for discussions over the statistical components. We also thank the two reviewers for their valuable feedback on an earlier version of the manuscript. This paper contains modified Copernicus Climate Change Service information (2017). We thank the Copernicus Climate Change Service and all scientists involved in this project. The authors state that neither the European Commission or European Centre for Medium‐Range Weather Forecasts (ECMWF) is responsible for any use that may be made of the Copernicus information or data it contains. We dedicate this paper to the memory of co‐authors Dr. Diana Angelez Ramirez Saldivar and Mr. Peter Titol Malim who devoted their lives to the conservation of wildlife in Sabah. Publisher Copyright: {\textcopyright} 2022 The Authors. American Journal of Primatology published by Wiley Periodicals LLC.",
year = "2022",
month = sep,
doi = "10.1002/ajp.23423",
language = "English",
volume = "84",
pages = "1--13",
journal = "American Journal of Primatology",
issn = "0275-2565",
publisher = "John Wiley and Sons Inc.",
number = "9",
}