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 50th 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.
Highlights
Individual-based long-term monitoring studies that build on detailed longitudinal life histories are important for understanding social, demographic, and ecological processes [1]
The mean age at first conception was lower at Uda Walawe than those reported for some populations in India, but slightly higher than other populations in Sri Lanka for which these variables were approximated based on age structure (Table 2)
While approximately a quarter to a third of the living Asian elephants may be in captive or semi-captive situations that are closely monitored [14,16,26,27,28,29], very little is known about the remaining wild populations that are scattered throughout South and South East Asia
Summary
Individual-based long-term monitoring studies that build on detailed longitudinal life histories are important for understanding social, demographic, and ecological processes [1]. This is relevant for large-bodied species with extended longevity, such as elephants, which mature and reproduce relatively slowly. Long-term studies of African elephants (Loxodonta africana) have documented similarities and disparities in the dynamics of elephant populations at different locations, as well as the demographic responses of those undergoing stress through drought and poaching [2,3,4,5]. Detailed demographic data are critical for establishing and predicting population trends of these keystone species as well as informing management decisions [6,7]. Because elephants are key players in structuring entire habitats, their population dynamics are likely to have cascading effects throughout ecosystems [8,9,10]
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