Population,age and sex assessment of free-ranging elephants of Periyar tiger reserve
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Date
2005
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Department of Livestock Production Management, College of Veterinary and Animal Sciences, Mannuthy
Abstract
A demographic study on the free ranging elephants of Periyar Tiger Reserve was conducted from March to May 2005. Herd composition, age structure and sex assessment were the main parameters recorded. The technique of molecular sexing using dung extracted DNA was incorporated into the study to reduce error in determining sex by physical verification. The published results by different investigators on the structure and pattern of elephant population in Periyar Tiger Reserve varied widely, especially on the age structure and biased sex ratios towards females giving the elephants in Periyar Tiger reserve a high priority conservation status. This information formed the basis for the study.
Of the total 239 elephants observed in 43 herds, 193 elephants were classified based on age and sex. It was found that more than 50 per cent of the recorded elephants were adult females. The calves formed 5.19 per cent, juveniles 20.76 per cent, sub adults 20.76 per cent and adult males only 0.889 per cent of the observed population. Females formed 81.99 per cent and males formed only 18.01% of the population, but the proportion of males and females in the calf and juvenile category was almost same, with a shift biased towards the females from the sub adult category onwards. The sex ratios in the juvenile, sub adult and adult categories were 1:0.9, 1:4.71 and 1:58.95 respectively. In the observed age-sex classes, adult females and sub adult females formed the major portion (69.53 %) of the population, a shift towards the older age class.
The calving interval of the Periyar elephants was above 10 years and the fecundity rate 0.099 indicating a population suggestive of acute shortage of breeding bulls and approximately only one in ten adult females conceive every year. This is the first study to combine reliable conventional tools and molecular methods to assess sex of free-ranging elephant population of Periyar Tiger Reserve. It is found that molecular sexing is a very reliable tool for assessing the sex of individuals of free-ranging wild animal populations.
The study infers that the present situation of the Periyar elephants is crucial and calls for further research and immediate active population management strategies.
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