Food Abundance Is the Main Determinant of High-Altitude Range Use in Snub-Nosed Monkeys

Cyril C. Grueter,Ming Li,Zuofu Xiang,Baoping Ren,Dayong Li

doi:10.1155/2012/739419

Abstract

High-altitude dwelling primates have to optimize navigating a space that contains both a vertical and horizontal component. Black-and-white or Yunnan snub-nosed monkeys (Rhinopithecus bieti) are extreme by primate standards in inhabiting relatively cold subalpine temperate forests at very high altitudes where large seasonal variation in climate and food availability is expected to profoundly modulate their ranging strategies so as to ensure a positive energy balance. A “semi-nomadic” group ofR. bietiwas followed for 20 months in the montane Samage Forest, Baimaxueshan Nature Reserve, Yunnan, PRC, which consisted of evergreen conifers, oaks, and deciduous broadleaf trees. The aim of this study was to disentangle the effects of climate and phenology on patterns of altitudinal range use. Altitude used by the group ranged from a maximum of 3550 m in July 2007 to a minimum of 3060 m in April 2006. The proportional use of lichen, the monkeys’ staple fallback food, in the diet explained more variation in monthly use of altitudes than climatic factors and availability of flush and fruit. The abundance of lichens at high altitudes, the lack of alternative foods in winter, and the need to satisfy the monkey's basal energetic requirements explain the effect of lichenivory on use of altitudes.

Highlights

An adaptive way for endotherm animals in montane temperate areas to cope with pronounced seasonality in climate and resource availability is to change location along an altitudinal gradient, thereby following food or avoiding cold/snow and maintaining a positive energy balance
None of the systematic studies on altitudinal ranging patterns in this species has delivered evidence for use of lower altitudes in winter [3,4,5,6]; see [7, 8] for the ecologically and phylogenetically close Rhinopithecus brelichi and R. roxellana, resp.). This peculiarity required explanation, and Quan et al [6] have recently proposed a sunshine hypothesis which posits that solar radiation affects the altitudinal distribution of this species, primarily because it reduces costs of thermoregulation
A test of this hypothesis in a population of R. bieti in Tibet has shown that solar radiation and sunshine hours increase with elevation in Tibet, and intensified solar exposure was seen as the main reason for the monkeys’ use of high altitudes in winter

Summary

Introduction

An adaptive way for endotherm animals in montane temperate areas to cope with pronounced seasonality in climate and resource availability is to change location along an altitudinal gradient, thereby following food or avoiding cold/snow and maintaining a positive energy balance. None of the systematic studies on altitudinal ranging patterns in this species has delivered evidence for use of lower altitudes in winter [3,4,5,6]; see [7, 8] for the ecologically and phylogenetically close Rhinopithecus brelichi and R. roxellana, resp.). This peculiarity required explanation, and Quan et al [6] have recently proposed a sunshine hypothesis which posits that solar radiation affects the altitudinal distribution (and microhabitat use) of this species, primarily because it reduces costs of thermoregulation. Quan et al [6] did not test a much more parsimonious

Objectives

Methods

Results

Conclusion