Cheryl Santa Maria
Venomous olive sea snakes are known to attack scuba divers in unprovoked incidents that sometimes involve biting and chasing.
Now, a new study published in Scientific Reports finds the snakes may just be trying to say "hello" and possibly spark up a romance.
Upon analysis of data collected between 1994 and 1995 by Tim Lynch, one of the study's authors, while diving in Australia's Great Barrier Reef, researchers found the encounters were more frequent during mating season.
Attacks involving males occurred immediately after unsuccessfully pairing with a female or after an incident with a male rival. Females tended to approach divers after chasing off a male snake.
Past research suggests sea snakes have trouble identifying shapes in water, and they are likely mistaking the divers for potential mates or, in the case of females, as hiding spots.
Experts say the best way for a diver to avoid a sea snake attack is to remain still and allow the snake to investigate them.
Though venomous, sea snakes don't deliver toxins every time they attack. While their venom is strong enough to kill a human, fatalities are rare.
- Article
- Open Access
- Published:
Mistaken identity may explain why male sea snakes (Aipysurus laevis, Elapidae, Hydrophiinae) “attack” scuba divers
Scientific Reports 11, Article number: 15267 (2021)
Abstract
Scuba-divers on tropical coral-reefs often report unprovoked “attacks” by highly venomous Olive sea snakes (Aipysurus laevis). Snakes swim directly towards divers, sometimes wrapping coils around the diver’s limbs and biting. Based on a focal animal observation study of free-ranging Olive sea snakes in the southern Great Barrier Reef, we suggest that these “attacks” are misdirected courtship responses. Approaches to divers were most common during the breeding season (winter) and were by males rather than by female snakes. Males also made repeated approaches, spent more time with the diver, and exhibited behaviours (such as coiling around a limb) also seen during courtship. Agitated rapid approaches by males, easily interpreted as “attacks”, often occurred after a courting male lost contact with a female he was pursuing, after interactions between rival males, or when a diver tried to flee from a male. These patterns suggest that “attacks” by sea snakes on humans result from mistaken identity during sexual interactions. Rapid approaches by females occurred when they were being chased by males. Divers that flee from snakes may inadvertently mimic the responses of female snakes to courtship, encouraging males to give chase. To prevent escalation of encounters, divers should keep still and avoid retaliation.
Introduction
Diverse and abundant in tropical marine waters, sea snakes of the subfamily Hydrophiinae are secondarily aquatic taxa derived from terrestrial elapid (front-fanged) snakes1,2. Laboratory studies suggest that the venoms of some species of sea snakes are highly toxic3; and worldwide, bites by sea snakes kill many people annually4,5. Although those fatalities generally involve fishermen rather than recreational or other users of the ocean6, SCUBA divers frequently report unprovoked “attacks” which can imperil divers through inducing panic, even if the snake does not deliver a bite7.
As described by Heatwole8, these “attacks” involve rapid jerky zigzag movements, easily distinguished from the leisurely swimming mode of curious snakes. Understanding the causes for such “attacks” is of interest from two perspectives. First, why would a free-ranging snake approach and bite a person that has not harassed it, is too large to be a prey item, and could readily be evaded in the complex three-dimensional world of a coral reef? Extensive studies on terrestrial snakes (including elapids) show that these animals would far prefer to escape than to confront an approaching human9, so why should sea snakes be so different? Second, understanding the context of these approaches might suggest how divers should respond to rapid approach by a potentially lethal snake. This may be of practical value to recreational dive and eco-tourism operators as well as commercial divers to mitigate this common human-wildlife interaction.
Anecdotal reports suggest that Olive sea snakes (Aipysurus laevis) are the most frequent “attackers”, and that this behaviour is manifested most frequently during the snake’s breeding season8,10,11,12,13. To explore those ideas, we quantified the seasonal timing and identity of “attacking” snakes in the course of a 27-month scuba-based behavioural study of sea snake ecology.
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