Fine-scale group structure and demography of African savanna elephants recolonizing lands outside protected areas

Authors

  • M. A. Ahlering,

    Corresponding author
    1. Division of Biological Sciences, University of Missouri, 226 Tucker Hall, Columbia, MO 65211, USA
    2. Center for Conservation and Evolutionary Genetics, Smithsonian Conservation Biology Institute, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
    3. African Conservation Centre PO Box 15289-00509, Nairobi, Kenya
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  • J. E. Maldonado,

    1. Center for Conservation and Evolutionary Genetics, Smithsonian Conservation Biology Institute, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
    2. Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, MRC 108, Washington, DC 20013, USA
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  • R. C. Fleischer,

    1. Center for Conservation and Evolutionary Genetics, Smithsonian Conservation Biology Institute, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
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  • David Western,

    1. African Conservation Centre PO Box 15289-00509, Nairobi, Kenya
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  • L. S. Eggert

    1. Division of Biological Sciences, University of Missouri, 226 Tucker Hall, Columbia, MO 65211, USA
    2. Center for Conservation and Evolutionary Genetics, Smithsonian Conservation Biology Institute, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
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Marissa A. Ahlering, The Nature Conservancy, 10 Cornell Stop 9019, Grand Forks, ND 58202, USA.
E-mail: mahlering@tnc.org

Abstract

Aim  Dispersal is a critical component of animal ecology that is poorly understood for most species. In particular, savanna elephants (Loxodonta africana) have been studied for decades in national parks across Africa, but little is known about their dispersal into new or unused habitats or their population dynamics in human-dominated landscapes. We capitalized on a natural dispersal event of savanna elephants recolonizing communal land in southern Kenya to document their demographic characteristics and genetic relationships.

Location  Rift Valley province of Kenya.

Methods  We collected faecal samples and used genetic methods to identify individuals, estimate the sex ratio and evaluate the patterns of relatedness within the female groups and male aggregations. We also measured dung bolus circumference to assign age classes to individuals and estimate the age structure.

Results  We identified 112 individuals with a sex ratio not different from one (1.32:1.00). The age structure was skewed towards younger elephants (71%), suggesting the potential for rapid growth from reproduction. We detected significantly higher kinship levels within female groups (= 0.124 ± 0.023), suggesting that family groups colonized the site, but found little support for higher-order genetic relationships among female groups. Males detected together were unrelated (= 0.003 ± 0.030).

Main conclusions  Our results suggest that highly social mammals, such as savanna elephants, disperse into unoccupied habitat as family groups and that a young demographic structure and a large number of males might be expected in establishing populations. These findings highlight the potential value of indirect, non-invasive methods for assessing elephant herd and demographic characteristics when direct observations are difficult.

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