Peaceful coexistence between people and deadly wildlife: why are recreational users of the ocean so rarely bitten by sea snakes?
Abstract
1. Research on interactions between humans and deadly snakes has focused on situations that result in high rates of snakebite; but we can also learn from cases where snakes and people coexist peacefully. For example, coastal bays near Noumea, in the Pacific archipelago of New Caledonia, are used by thousands of tourists and snakes, but bites are rare. 2. Our long-term studies clarify reasons for this coexistence. Although 97% of snakes encountered in standardised snorkel surveys were a harmless species Emydocephalus annulatus, we recorded dangerously venomous taxa often enough (one snake per 8 hr snorkelling) that we would expect many risky human-snake interactions in these crowded bays. However, the risk is reduced by low overlap between humans and snakes in the timing of activity, both seasonally and on the diel cycle. Mate-searching male snakes, the group most likely to approach divers, enter the bays only in cooler months of the year when few beach users are present. Also, snakes tend to be active by night, whereas people are not. 3. Risk is further reduced by spatial divergence: bare-footed beach users stay in sandy areas rather than the adjacent coral-reef areas that are preferred by snakes. The response of snakes to disturbance is also important: most sea snakes are reluctant to bite even when harassed. Water currents frequently push sea snakes against hard objects, perhaps explaining why the snakes do not interpret brief contact with a human as an attack. The ability of snakes to flee is increased by uniformly high body temperature, and a complex three-dimensional aquatic environment. 4. Thus, the danger of snakebite for recreational users of these popular beaches is reduced by aspects of human and snake behaviour that (a) decrease encounter rates and (b) render snakes unlikely to bite even if contacted. The risk to snakes is also reduced because snakes are more difficult to detect and kill underwater than on land. As a result, thousands of snakes and people coexist harmoniously within these small bays.