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Elephant poaching in Niassa Reserve, Mozambique: population impact revealed by combined survey trends for live elephants and carcasses

  • Vernon R. Booth (a1) and Kevin M. Dunham (a2)
Abstract
Abstract

Trends in the populations of large herbivores in Niassa Reserve, Mozambique, have been monitored through biennial aerial surveys since 1998. The elephant Loxodonta africana population has been subjected to intensive illegal hunting since 2006. We used a simple population model to mimic the observed trends in the numbers of live and dead elephants to demonstrate the impact of poaching. The number of fresh or recent carcasses recorded was used in the model as an index of the annual mortality rate. A maximum likelihood analysis to compare population models revealed that the best fit to the survey estimates of both live elephants and old or very old carcasses was a model that started with 6,635 elephants in 1987. This number increased through births by 4.6% annually and decreased through deaths from natural and anthropogenic causes. In the best-fit model, the mean mortality rate in any year was 3.2 times the observed 1 + 2 carcass ratio (ratio for carcasses in age categories 1 and 2), and carcasses remained visible for a mean of 6 years. The model suggested that c. 900 elephants were poached during 2007–2010 and another c. 1,000 during 2011. Population estimates for live elephants and carcasses are now routine outcomes of aerial surveys conducted as part of the CITES programme for Monitoring the Illegal Killing of Elephants, and our method can be applied to any population with a time series of estimates for live and dead elephants.

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(Corresponding author) E-mail vernonrbooth@gmail.com
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This paper contains supplementary material that can be found online at http://journals.cambridge.org
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This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

R.W. Burn , F.M. Underwood & J. Blanc (2011) Global trends and factors associated with the illegal killing of elephants: a hierarchical Bayesian analysis of carcass encounter data. PLoS ONE, 6(9), e24165.

T.F. Corfield (1973) Elephant mortality in Tsavo National Park, Kenya. African Journal of Ecology, 11, 339368.

K.M. Dunham (2008) Detection of anthropogenic mortality in elephant Loxodonta africana populations: a long-term case study from the Sebungwe region of Zimbabwe. Oryx, 42, 3648.

A. Herman , V.B. Kumar , P.A. Arkin & J.V. Kousky (1997) Objectively determined 10-day African rainfall estimates created for famine early warning systems. International Journal of Remote Sensing, 18, 21472159.

N.S. Ribeiro , H.H. Shugart & R. Washington-Allen (2008) The effects of fire and elephants on species composition and structure of the Niassa Reserve, northern Mozambique. Forest Ecology and Management, 255, 16261636.

M.P. Wells (1989) The use of carcass data in the study and management of African elephants: a modelling approach. African Journal of Ecology, 27, 95110.

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Oryx
  • ISSN: 0030-6053
  • EISSN: 1365-3008
  • URL: /core/journals/oryx
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Booth and Dunham Supplementary Material
Tables S1-S2

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