Elephant are not beetles: implications of the ivory trade for the survival of the African elephant

Poole, Joyce H.; Thomsen, Jørgen B.

doi:10.1017/s0030605300023012

Cited by 28 publications

(23 citation statements)

References 19 publications

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“…Our model showed that selective hunting under all 3 environmental conditions tested, not only can have a direct effect on reducing population size (Milner et al , Allendorf et al ) but also can bias the sex‐ratio in favor of females and heavily skew the age structure towards younger animals. Undisturbed elephant populations have only a slightly skewed sex ratio favoring females (Poole and Thomsen , Wittemyer ). Thus selective hunting consequently could have an effect on reproduction (Ginsberg and Milner‐Gulland , Milner et al , Allendorf et al ).…”

Section: Discussionmentioning

confidence: 99%

Sustainability of elephant hunting across international borders in southern Africa: A case study of the greater Mapungubwe Transfrontier Conservation Area

et al. 2013

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Trophy hunting of African elephant is often implemented as an income generator for communities surrounding protected areas. However, the sustainability of hunting on elephant populations, especially with regards to international cross‐border populations has not previously been evaluated. We assessed the effects of trophy hunting on the population dynamics and movements of elephant in the Greater Mapungubwe Transfrontier Conservation Area, which is spread across the junction of Botswana, South Africa, and Zimbabwe. Currently, no common policy exits in quota setting for cross‐border species, and each country determines their own quota based on limited data. Using VORTEX, we determined the sustainability of current quotas of elephant off‐take under different ecological and hunting scenarios. We used distribution data from 6 aerial surveys and hunting data per region to determine the disturbance effect of hunting on bulls and breeding herds separately. Hunting of bulls had a direct effect in reducing bull numbers but also an indirect effect due to disturbance that resulted in movement of elephants out of the areas in which hunting occurred. The return interval was short for bulls but longer for females. Only a small number of bulls (<10/year) could be hunted sustainably. At current rates of hunting, under average ecological conditions, trophy bulls will disappear from the population in less than 10 years. We recommend a revision of the current quotas within each country for the Greater Mapungubwe elephant population, and the establishment of a single multi‐jurisdictional (cross‐border) management authority regulating the hunting of elephant and other cross‐border species. © 2013 The Wildlife Society

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Section: Discussionmentioning

confidence: 99%

Sustainability of elephant hunting across international borders in southern Africa: A case study of the greater Mapungubwe Transfrontier Conservation Area

et al. 2013

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“…). Illegal ivory harvesting caused changes in age and sex structure leading to reduction or elimination of older animals; an effect more severe in males compared to females (e.g., Poole ; Poole and Thomsen ; Barnes and Kapela ). Elephant poaching targets older individuals and males because older animals and males carry large tusks than younger animals and males carry larger tusks compared to females.…”

Section: Introductionmentioning

confidence: 99%

Illegal tusk harvest and the decline of tusk size in the African elephant

Chiyo

Obanda

Korir

2015

Ecology and Evolution

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SummaryHarvesting of wild populations can cause the evolution of morphological, behavioral, and life history traits that may compromise natural or sexual selection. Despite the vulnerability of large mammals to rapid population decline from harvesting, the evolutionary effects of harvesting on mega‐fauna have received limited attention. In elephants, illegal ivory harvesting disproportionately affects older age classes and males because they carry large tusks, but its' effects on tusk size for age or tusk size for stature are less understood. We tested whether severe historical elephant harvests eliminated large tuskers among survivors and whether elephants born thereafter had smaller tusks. Adjusting for the influence of shoulder height – a metric strongly correlated with body size and age and often used as a proxy for age – we compared tusk size for elephants sampled in 1966–1968, prior to severe ivory harvesting in the late 1970s and early 1980s, with tusk size of survivors and elephants born during population recovery in the mid‐1990s. In a regional population, tusk length declined by ˜21% in male and by ˜27% in female elephants born during population recovery, while tusk length declined by 22% in males and 37% in females among survivors. Tusk circumference at lip declined by 5% in males but not in females born during population recovery, whereas tusk circumference reduced by 8% in male and by 11% in female survivors. In a single subpopulation, mean tusk length at mean basal tusk circumference declined by 12.4% in males and 21% in females. Tusk size varied between elephant social groups. Tusk homogeneity within social groups and the often high genetic similarity within social groups suggest that tusk size may be heritable. Our findings support a hypothesis of selection of large tuskers by poachers as a driver of the decline in tusk size for age proxy and contemporary tusk evolution in African elephants.

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“…Poaching of elephants for ivory has been a serious conservation issue not only in African elephant (Loxodonta africana) populations (Western, 1987;Douglas-Hamilton 1988;Poole & Thomsen, 1989;Dublin, Milliken & Barnes, 1995) but also in Asian elephant (Elephas maximus) populations (Sukumar, 1989;Menon, Sukumar & Kumar, 1997). Unlike the African elephant, where both sexes generally possess tusks, only males in the Asian elephant have tusks.…”

Section: Introductionmentioning

confidence: 99%

Impact of poaching on an Asian elephant population in Periyar, southern India: a model of demography and tusk harvest

Sukumar

Ramakrishnan

Santosh

1998

Animal Conservation

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Ivory poaching has been a serious problem in Asian elephant (Elephas maximus) populations. Reliable records of elephants killed and ivory harvested are generally unavailable. We have used a simulation modelling approach to estimate the numbers of male elephants killed and the quantities of ivory harvested over a 20 year period in the Periyar Reserve of southern India. The age-structured Leslie matrix projection model was modified for this purpose by considering three segments (female, tusked male and tuskless male), relating fecundity to adult sex ratio and iteratively simulating tusked male mortality rates so as to match the observed elephant population structure at Periyar. Four different scenarios of poaching all gave very similar results. We estimate conservatively that 336-388 tuskers have been poached and 3256-3334 kg of ivory harvested by poachers over the 20 year period. The maximum harvest came from the 10-20 year age class. Trends in various demographic parameters such as population numbers, tusked male to tuskless male ratios and female fecundity are described. The implications of ivory poaching and the extremely skewed sex ratios for the conservation and management of the elephant population at Periyar are discussed.

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Elephant are not beetles: implications of the ivory trade for the survival of the African elephant

Cited by 28 publications

References 19 publications

Sustainability of elephant hunting across international borders in southern Africa: A case study of the greater Mapungubwe Transfrontier Conservation Area

Sustainability of elephant hunting across international borders in southern Africa: A case study of the greater Mapungubwe Transfrontier Conservation Area

Illegal tusk harvest and the decline of tusk size in the African elephant

Impact of poaching on an Asian elephant population in Periyar, southern India: a model of demography and tusk harvest

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