Demographic variables for wild Asian elephants using longitudinal observations

PLoS One. 2013 Dec 20;8(12):e82788. doi: 10.1371/journal.pone.0082788. eCollection 2013.

Abstract

Detailed demographic data on wild Asian elephants have been difficult to collect due to habitat characteristics of much of the species' remaining range. Such data, however, are critical for understanding and modeling population processes in this endangered species. We present data from six years of an ongoing study of Asian elephants (Elephas maximus) in Uda Walawe National Park, Sri Lanka. This relatively undisturbed population numbering over one thousand elephants is individually monitored, providing cohort-based information on mortality and reproduction. Reproduction was seasonal, such that most births occurred during the long inter-monsoon dry season and peaked in May. During the study, the average age at first reproduction was 13.4 years and the 50(th) percentile inter-birth interval was approximately 6 years. Birth sex ratios did not deviate significantly from parity. Fecundity was relatively stable throughout the observed reproductive life of an individual (ages 11-60), averaging between 0.13-0.17 female offspring per individual per year. Mortalities and injuries based on carcasses and disappearances showed that males were significantly more likely than females to be killed or injured through anthropogenic activity. Overall, however, most observed injuries did not appear to be fatal. This population exhibits higher fecundity and density relative to published estimates on other Asian elephant populations, possibly enhanced by present range constriction. Understanding the factors responsible for these demographic dynamics can shed insight on the future needs of this elephant population, with probable parallels to other populations in similar settings.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aging / physiology
  • Animals
  • Animals, Wild / physiology*
  • Conservation of Natural Resources
  • Demography
  • Elephants / physiology*
  • Female
  • Fertility
  • Geography
  • Longitudinal Studies
  • Male
  • Parturition
  • Rain
  • Sri Lanka

Grants and funding

This research was funded in part by the U.S. Fish and Wildlife Asian Elephant Conservation Fund (Grant nos. F11AP00258 and 92210-7-G167) to SdS and DW, as well as a Postdoctoral Research Fellowship in Biology from the National Science Foundation (Award No. 1103468, SdS). Publication was supported by Colorado State University’s Open Access Research and Scholarship Fund (GW). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.