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Temporal trends in elephant Loxodonta africana numbers and densities in northern Botswana: is the population really increasing?

Jessica Junkera1, Rudi J. van Aardea1 c1 and Sam M. Ferreiraa1

a1 Conservation Ecology Research Unit, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.

Abstract

The apparent increase in elephant Loxodonta africana numbers in northern Botswana is of concern because it may affect other species. We compared changes in population growth rates based on elephant numbers and densities over 1973–2004. Population estimates and survey details extracted from published and unpublished sources allowed us to calculate growth rates. From 1973 to 1993 growth rate was positive when based on elephant numbers but did not differ from zero when calculated for densities. This discrepancy may be because of the significant increase in survey area during the same period. In contrast, none of the growth rates differed from zero for time series between 1996 and 2004, when the size of the survey area varied little. We propose two explanations for these results. The first suggests that the population did not grow, while the second proposes that the population expanded its range and increased in size. Notwithstanding, an equilibrium model best explained the variance in dry season estimates of elephant numbers for the complete time series. Such apparent density-dependence could be disrupted by any artificial reduction of numbers through culling as a management option in northern Botswana.

(Received October 04 2006)

(Reviewed November 14 2006)

(Accepted December 21 2006)

(Online publication January 14 2008)

Correspondence:

c1 Conservation Ecology Research Unit, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. E-mail rjvanaarde@zoology.up.ac.za

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