The Impact of Tusks on the Diet and Behavior of the African Elephant, Loxodonta africana

Abstract

Many African elephants, Loxodonta africana, currently have short tusks due to selective pressures from poaching and the impact of a new conservation strategy referred to as detusking. Detusking involves the removal of the majority of an elephant’s tusks in the hopes of preventing that elephant from breaking fences and raiding farmers’ crops. While detusking is currently only being utilized by Lewa Wildlife Conservancy, Kenya, this potential conservation strategy may soon spread to nearby conservancies (Mutinda, personal communication). However, the impact of short tusks on the diet and behavior of elephants was previously unknown. The purpose of this study was to understand whether detusked elephants, naturally short-tusked elephants, and naturally long-tusked elephants differ from each other in terms of their nutritional levels and feeding behavior. I hypothesized that if bark and large branches on Lewa contained higher levels of certain nutrients than other food sources available to elephants and if elephants need long tusks to access bark and branches, then detusked and short-tusked elephants should either experience a nutrient deficiency or alter their feeding behavior in a compensatory manner to prevent low nutrition levels. I found one of my key assumptions to be true, namely that elephants need longer tusks in order to most effectively break off large branches from trees. However, I did not find that bark and large branches on Lewa contained significantly higher levels of key nutrients (protein, calcium, sodium) or energy than twigs and grasses, contrary to results found on other conservancies. Thus, even though short-tusked and detusked elephants were observed consuming branches to a significantly smaller degree, this did not result in a nutrient deficiency or in a need for short-tusked and detusked elephants to perform compensatory feeding behaviors. However, tusk length was associated with differences in fitness for females. All females in this study were matriarchs and groups with long-tusked matriarchs were significantly larger and had significantly more young in the group than in those of short-tusked matriarchs. This indicates higher reproductive fitness for the long-tusked female matriarchs. I was unable to acquire sufficient data to measure reproductive fitness in males. While no nutrient deficiencies were found on Lewa, this study should be carried out on conservancies where bark does contain significantly higher levels of nutrients like calcium. In these locations, a nutrient deficiency may arise and worsen the fitness condition of the short-tusked elephants there. Future studies should also measure the link between diet and reproductive fitness in males. Until these studies have been conducted, I recommend that detusking should be used cautiously as a conservation strategy and only when the vegetation of the conservancy has been thoroughly assessed and found to have sufficient nutrients in grasses and tree twigs to sustain an elephant’s nutrient demands.