Leaf-scaled sea snake (Aipysurus foliosquama)

Leaf-scaled sea snake fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Leaf-scaled sea snake description

The leaf-scaled sea snake (Aipysurus foliosquama) is named for the characteristic leaf-like shape of its body scales ^{(2) (3)}, which strongly overlap each other ⁽²⁾.

A small, slender snake, the leaf-scaled sea snake has a small head, with large, symmetrical scales, and a pointed snout ⁽²⁾. Its nostrils are positioned higher up on its head than in terrestrial snakes, which makes it easier to breathe when it surfaces. As in other sea snake species, the end of the leaf-scaled sea snake’s tail is flattened and paddle-like, enabling this marine reptile to swim efficiently ⁽⁴⁾.

The upper surface of the leaf-scaled sea snake is reddish-brown to purplish ⁽²⁾, and is marked with paler, contrasting bands or rings ^{(2) (3)}. The scales on the underside of the leaf-scaled sea snake are deeply notched ⁽²⁾.

Male and female leaf-scaled sea snakes are similar in appearance, although the female is usually larger than the male ⁽³⁾.

Also known as

leaf-scaled seasnake.

Size

Length: 60 - 90 cm ⁽²⁾

Weight

up to 500 g ⁽³⁾

Leaf-scaled sea snake biology

Like all species within the Aipysurus genus, the leaf-scaled sea snake is an entirely aquatic species, never venturing onto land, not even to breed ⁽⁶⁾. Typically a solitary reptile ^{(1) (2)}, the leaf-scaled sea snake is nevertheless sometimes found at coral outcrops with other sea snake species ^{(1) (2)}, and although venomous it is rarely aggressive ⁽³⁾.

As is true of all sea snakes, the leaf-scaled sea snake is an air-breathing reptile, but it is capable of remaining underwater for up to two hours at a time, before surfacing to breathe again. Its single, elongated lung, which extends for almost the entire length of its body, is highly efficient for gas exchange, and sea snakes are also able to absorb oxygen through their skin when underwater. All sea snakes have specialised nostril valves which prevent water from entering the lung when submerged ⁽²⁾.

Living in the marine environment poses several other challenges, and as in other sea snake species, the leaf-scaled sea snake has a specialised gland under its tongue which enables it to excrete excess salt from its body. A sea snake sheds its skin approximately once every two to six weeks, by rubbing its lips against something hard such as coral until the loosened skin is anchored there. The sea snake then crawls forwards, leaving the skin turned inside out behind it. By shedding its skin so frequently, a sea snake can get rid of the many marine species, such as algae and barnacles, which become attached to it ⁽²⁾.

Like most species of sea snake, the leaf-scaled sea snake is viviparous, meaning that it gives birth to live young rather than laying eggs ^{(2) (3)}. Mating in sea snakes is a lengthy affair, and the males are unable to disengage from the female until copulation is complete. The gestation period of the leaf-scaled sea snake is thought to be between six and seven months, after which time a small brood is born. Generally, sea snakes are long-lived and slow-growing ⁽²⁾, and the leaf-scaled sea snake is thought to have a lifespan of approximately eight to ten years and to reach maturity at two years old ⁽¹⁾.

The leaf-scaled sea snake feeds on small coral reef fish ^{(1) (2) (3)}, including wrasse (Halichoeres species), gudgeons (Eleotridae species) and eels (Anguilliformes) ⁽²⁾. It hunts its prey by poking its head into hollows and crevices within the reef ^{(1) (2)}, before immobilising its quarry with a quick strike ⁽¹⁾.

Leaf-scaled sea snake range

The leaf-scaled sea snake has an extremely limited range ⁽¹⁾, possibly being the most restricted of all sea snake species ⁽³⁾. It is endemic to the Ashmore and Hibernia Reefs in the Timor Sea ^{(1) (2) (3) (5)}, where it is thought to occupy a total area of less than ten square kilometres ⁽¹⁾.

Occasional records of the leaf-scaled sea snake from other locations in northwest Australian waters are thought to be of vagrant individuals which are not part of the breeding population of this species ⁽¹⁾.

Leaf-scaled sea snake habitat

The leaf-scaled sea snake is primarily found in the shallow waters of outer reef edges or on the reef flat itself, usually in water depths of less than ten metres ^{(1) (2) (3)}.

On Ashmore Reef, the leaf-scaled sea snake can be found in exposed tidal pools during low tide, and is thought to have behavioural adaptations which enable it to tolerate the high water temperatures within the pools ⁽²⁾.

Leaf-scaled sea snake status

The leaf-scaled sea snake is classified as Critically Endangered (CR) on the IUCN Red List ⁽¹⁾.

Leaf-scaled sea snake threats

In the 1990s, the leaf-scaled sea snake used to comprise about 50 percent of the sea snakes commonly recorded on its native reef flats, with its population numbers estimated at between 4,000 and 9,000. However, intensive surveys have failed to record a single individual since 2001 ⁽¹⁾.

The threats to this species are largely unknown, but it is not thought to be affected by fisheries, as it is not a target species and is not subject to being accidentally caught in trawls, a fate which befalls many other sea snake species. Declines in the leaf-scaled sea snake could potentially be a result of habitat degradation due to coral bleaching and an overall decline in the quality and health of its ecosystem, which consequently leads to a reduction in prey abundance. As well as causing coral degradation, increasing water temperatures as a result of climate change may exceed the upper lethal limit for the leaf-scaled sea snake, which in other sea snake species has been found to be 36 degrees Celsius ⁽¹⁾.

As a shallow-water species, the leaf-scaled sea snake is unable to move to areas of higher habitat quality, as deep water barriers restrict its dispersal ability ⁽¹⁾.

Leaf-scaled sea snake conservation

The leaf-scaled sea snake used to be the most common sea snake species encountered on the reef flat at Ashmore Reef ⁽²⁾. However, despite it being a nature reserve since 1983 ⁽¹⁾, sightings in this particular area have not been reported since 2001 ⁽²⁾. Illegal fishing on the reef has been monitored at various levels since 1983, although protection of marine life in the area was not actively enforced until 1998. Unfortunately, none of the implemented habitat management plans are specifically targeted towards conserving the leaf-scaled sea snake, and it is unclear how, or to what extent, these measures are reducing the current threats to this species ⁽¹⁾.

All sea snake species in Australia are protected under their classification by the Department of Environment and Water Resources as ‘Listed Marine Species’ ⁽¹⁾. In addition, sea snakes are protected under the Environment Protection and Biodiversity Conservation Act 1999 ^{(1) (2)}, while the Australian Fisheries Management Act 1991 requires fisheries to avoid impacting on protected or threatened species, including sea snakes. A three-year study has been instigated to develop and implement a long-term bycatch monitoring programme for Australia’s Northern Prawn Fishery, which has the largest impact of any Commonwealth-managed fishery on protected sea snake populations ⁽¹⁾.

Since 2003, industry workshops have been jointly run by Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) and Australia’s Fisheries Management Authority (AFMA) to train prawn fishery crew members on how to identify, photograph and record information regarding sea snake capture during the main prawn seasons ⁽¹⁾.

Find out more

Find out more about sea snakes:

• Carpenter, K.E. and Niem, V.H. (2001) The Living Marine Resources of the Western Central Pacific. Volume 6: Bony Fishes Part 4 (Labridae to Latimeriidae), Estuarine Crocodiles, Sea Turtles, Sea Snakes and Marine Mammals. Food and Agriculture Organization of the United Nations, Rome. Available at:
  ftp://ftp.fao.org/docrep/fao/009/y0870e/y0870e65.pdf
• IUCN - Sea snakes:
  http://www.iucn.org/knowledge/news/biocuriosities/?4798/Sea-snakes

Learn more about marine conservation in Australia:

• Australian Marine Conservation Society:
  http://www.amcs.org.au/
• University of Western Australia Oceans Institute:
  http://www.oceans.uwa.edu.au/

Find out more about protected Australian species:

• Species Profile and Threats Database (SPRAT):
  http://www.environment.gov.au/cgi-bin/sprat/public/sprat.pl

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Glossary

Algae

Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.

Bycatch

In the fishing industry, the part of the catch made up of non-target species.

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Genus

A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

Gestation

The state of being pregnant; the period from conception to birth.

Gland

An organ that makes and secretes substances used by the body.

Reef flat

The shoreward, flat, broadest area of a coral reef.

Vagrant

An individual found outside the normal range of the species.

Viviparous

Giving birth to live offspring that develop inside the mother’s body.

References

1. IUCN Red List (October, 2012)
   http://www.iucnredlist.org/
2. Department of Sustainability, Environment, Water, Population and Communities (2012) Aipysurus foliosquama. In: Species Profile and Threats Database. Department of Sustainability, Environment, Water, Population and Communities, Canberra. Available at:
   http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=1118
3. Cousteau, F. (2008) Ocean: The World’s Last Wilderness Revealed. Dorling Kindersley, London.
4. Karleskint, G., Turner, R. and Small, J. (2010) Introduction to Marine Biology. Brooks/Cole Publishing, Kentucky.
5. The Reptile Database (October, 2012)
   http://reptile-database.reptarium.cz/search.php
6. Tomascik, T. and Mah, A.J. (1997) The Ecology of the Indonesian Seas. Tuttle Publishing, Vermont.