Emydocephalus annulatus

Turtle-Headed Sea Snake
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Family:	Elapidae
Subfamily:	Hydrophiinae
Genus:	Emydocephalus
Species:	E. annulatus
Binomial name
Emydocephalus annulatus Krefft, 1869

The Turtle-Headed Sea Snake (Emydocephalus annulatus) is a species of sea snake that can be found in waters of Oceania near Australia and some Pacific Islands like the Philippines and the Loyalty Islands of New Caledonia. The range is sporadic, for example, with populations distributed in the Eastern and Western coasts of Australia in the Great Barrier Reef and the Timor Sea reefs respectively. They do not, however, occur in the Gulf of Carpentaria along the North coast.^[1] Named for its short, blunt head, the medium-sized snake has a slender build and varies in color. A single snake may exhibit only one color or may have banded patterns of white or yellow with dark rings. The scales on top of the head are large, regular, and entire. The rostral scale on the tip of the snout is conical in shape, and the second of three supralabial scales is the largest. The body has 15-17 rows of smooth, overlapping scales. It has 125-145 ventral scales, a single anal scale, and 20-33 single subcaudal scales. It may grow to 75 cm in length.^[2]

According to a recent study, an individual snake's color affects the amount of algal fouling that accumulates on its body. A snake of a darker, more monotonous color will have a higher amount of algae build-up than those of a paler, patterned variety. The added weight of algae affects an individual's speed, reducing it by 20%. It was observed that those whose locomotive skills were affected had a tendency to be more inactive and choose to hide among the coral, while those with little to no algal fouling were found actively foraging. The inactivity, however, did not affect their survival rates as the study did not find significant evidence that lighter-colored snakes were more likely to survive than their darker-colored counterparts.^[3]

In recent years, there is still, however, a steady decline in populations in and around the New Caledonian Lagoon. About twice a week for nine years (2003-2011 inclusive), scientists have counted the number of individual sea snakes within the protected coral reef snorkeling area in the lagoon. In 2003, volunteers spotted an average of more than six snakes per day, which decreased to less than two per day in 2011.^[4] In 2006, similar studies were also done in Ashmore Reef in northern Australia that exhibited a decline in population as well.^[1] The cause of the decline is indistinct in either case, though the authors of both studies attributed it to human interference, habitat degradation due to tourism, coral bleaching, and habitat and diet complexity.^[1][4]

Dietary Habits

The Turtle Headed Snake feeds solely on immobile demersal fish eggs, such as damselfish, blennies, and gobies.^[5][6] The larger the snake, the more probable they are to feed on damselfish eggs, which lie in exposed areas, rather than blennies and gobies whose eggs are located in narrow crevices.^[5] Interestingly, E. annulatus populations tend to stay where they are and rarely move between each other. This could possibly have something to do with the spatial memory of snakes and their ability to remember where nests are located. If they stay in the same area, then the snakes are able to feed regularly on the same sites.^[7] Curiously, Emydocephalus is the only sea snake that does not possess palatal teeth.^[6] Contrary to the foraging habits of other snakes, the turtle head tends to eat smaller, more frequent meals rather than larger, infrequent prey. In this respect, Emydocephalus feeds more like a grazing mammal than a snake. This atypical method of feeding is evidence of the great adaptive radiation of snakes.^[8]

Mating Habits

Terrestrial snakes use pheromones to locate potential sexual partners with a male often tracking a female's scent over large distances. Tracking scents over long distances, however, not possible in the aquatic environment of the Turtle Headed Snake.^[9] E. annulatus uses visual cues to search for mates. These includde the size, movement, and color pattern of the object holding its attention.^[9] Upon locating females, the reception of female skin lipid pheromones by tongue-flicking males is necessary for males to continue courtship and mating^[9]

Turtle Headed Snakes are sexually dimorphic. The females of this species grow larger than males.^[9] The rugosity of the scales is greatly increased in males compared to females.^[9]

References