Into the night: camera traps reveal nocturnal activity in a presumptive diurnal primate, Rhinopithecus brelichi

Chia L. Tan,Yeqin Yang,Kefeng Niu

doi:10.1007/s10329-012-0318-2

Abstract

Most living primates exhibit a daytime or nighttime activity pattern. Strict diurnality is thought to be the rule among anthropoids except for owl monkeys. Here we report the diel activity pattern of an Asian colobine, the Guizhou snub-nosed monkey Rhinopithecus brelichi, based on a methodology that relied on using 24-h continuously operating camera traps. We conducted the study in Fanjingshan National Nature Reserve in Guizhou, China from March 22 to May 19 and from June 17 to October 14, 2011. After standardizing all time elements to a meridian-based time according to the geographic coordinates of the study site, we showed unequivocally that the monkeys, though predominantly diurnal, exhibited activity beyond daylight hours throughout the study. Specifically, their activity at night and during twilight periods suggests a complex interplay of behavioral adaptations, among others, to living in a temperate environment where day length and food resources fluctuate substantially across seasons. We contend that, under prevailing ecological conditions, so-called strictly diurnal primates may adjust their activity schedule opportunistically in order to increase energy intake. We also discuss the advantages of using camera traps in primate studies, and how the standardized use of meridian-based time by researchers would benefit comparisons of diel activity patterns among primates.

Highlights

Camera traps have become an effective tool for studies of wildlife populations without direct observation or physically capturing animals
Images of four vertebrate species were captured by our camera traps; they included those of R. brelichi, M. thibetana, the giant flying squirrel Petaurista sp., and the golden pheasant Chrysolophus pictus
Since categorically diurnal and nocturnal primates differ significantly in their features of the visual system (Kay and Kirk 2000; Kirk and Kay 2004), this distinction has led to the assumption that primates are largely confined to a diel activity pattern due to constraints associated with a particular type of visual system

Summary

Introduction

Camera traps have become an effective tool for studies of wildlife populations without direct observation or physically capturing animals. Use of camera traps is ideal for surveying elusive animals in vast, remote areas with difficult field conditions that prohibit adequate sampling using more traditional methodologies (Kays and Slauson 2008; O’Connell et al 2011). Beyond population surveys and monitoring, camera traps are useful in ecological and behavioral research, as images captured may reveal key information about habitat, and the behavior of species on an individual as well as group basis (Bridges and Noss 2011). We applied camera trap technology to our research on free-ranging Guizhou snubnosed monkeys R. brelichi—an endangered species with a single global population of 700–800 individuals restricted to Fanjingshan in southwest China (Yang et al 2002).

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Results

Conclusion