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

Ecology and Evolution
Patrick I ChiyoDavid K Korir

Abstract

Harvesting 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 su...Continue Reading

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Citations

Nov 16, 2018·Proceedings. Biological Sciences·Sarah P Otto
Nov 2, 2017·Scientific Reports·Shifra Z Goldenberg, George Wittemyer
Dec 1, 2017·Proceedings. Biological Sciences·Robert J Knell, Carlos Martínez-Ruiz
Oct 3, 2020·Evolutionary Applications·Tonje Knutsen SørdalenEsben Moland Olsen

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