Male biased sex ratio of poached elephants is negatively related to poaching intensity over time

Poaching and habitat loss has caused a massive decline in the number and range of African elephants over the past few decades, with the greatest post ivory ban losses occurring since 2006. Poaching targets the largest individuals for their greater tusk sizes. This should also bias poaching towards males. We hypothesized that elephant sex ratios from heavily poached populations will initially be strongly male biased, but become progressively less male biased in heavily poached areas over time. This will occur because large, older female matriarchs will eventually provide the next source of large tusks once the largest males are killed. In this paper, we examined the sex ratio of ivory samples from very large ivory seizures (0.5-6.5 tons) made between 2002 and 2013. Origins of these large seizures were independently determined and in most cases, consisted of individuals poached in the same or nearby location. Our results indicate a male-biased sex ratio among these large ivory seizures. The earliest and largest seizure (6.5 tons seized in 2002) from Zambia was 4-6 times more male biased than later seizures. However, male bias progressively declined in samples that originated from that same, heavily poached area over time, indicating a rise in female targets. These trends are likely to have negative implications on elephant recovery given the importance of female matriarchs to elephant social structure and population growth.