Sleeping Site and Tree Selection by Bale Monkeys (Chlorocebus djamdjamensis) at Kokosa Forest Fragment in Southern Ethiopia

Addisu Mekonnen,Vivek V Venkataraman,Colin A Chapman,R Adriana Hernandez-Aguilar,Nils Chr Stenseth,Peter J Fashing

doi:10.1007/s10764-021-00251-1

Abstract

Although selecting advantageous sleeping sites is crucial for nonhuman primates, the extent to which different factors contribute to their selection remains largely unknown for many species. We investigated hypotheses relating to predator avoidance, food access, and thermoregulation to explain the sleeping behavior of Bale monkeys (Chlorocebus djamdjamensis) occupying a degraded fragmented forest, Kokosa, in the southern Ethiopian Highlands. We found that the study group reused 11 out of 20 sleeping sites used during the 42 study days over a 6-month period. Sleeping sites were usually close to the last feeding trees of the day (mean distance =15.2 m) and/or the first feeding trees of the next morning (mean distance = 13.5 m). This may reflect an attempt to maximize feeding efficiency and reduce travel costs. Compared to the mean trees in the study area, sleeping trees were significantly shorter. Bale monkeys selected sleeping places in trees with high foliage density above and below them, lending support to the hypothesis that they select sleeping places that can conceal them from predators and at the same time offer shelter from cold weather. The monkeys also frequently huddled at night. Our results suggest that predator avoidance, access to food resources, and thermoregulation all likely influence the selection of sleeping sites by Bale monkeys.

Highlights

The selection of sleeping sites is an essential aspect of the behavioral ecology of primates and may be crucial for individual survival
The top five species chosen in decreasing order of selectivity were Cupressus lusitanica, Allophyllus abyssinicus, Maytenus obscura, Schefflera volkensii, and Ilex mitis (Table III)
In line with the predation avoidance hypothesis, during our study Bale monkeys often reused a few sleeping sites, a strategy that would increase their familiarity with the area and may enhance their chance of escape from predators

Summary

Introduction

The selection of sleeping sites is an essential aspect of the behavioral ecology of primates and may be crucial for individual survival. Because primates spend about half of their lives at sleeping sites, they are vulnerable to predators at these locations during prolonged periods of time while sleeping (Anderson, 1998). The predation avoidance hypothesis proposes that primates select sleeping sites that minimize the risk of being detected by predators and at the same time favor primates’ detection of predators to increase their chances of escaping (Anderson, 1998). Some primates are suggested to change their sleeping sites frequently to decrease the predictability of a predator finding them (e.g., François’ langur [Trachypithecus francoisi: Qihai et al, 2009]; wild saddleback tamarin [Saguinus fuscicollis: Smith et al, 2007])

Methods

Results

Conclusion