Broad-headed snake  (Hoplocephalus bungaroides)

The broad-headed snake is classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (5).

A nocturnal, rock-dwelling reptile, the broad-headed snake (Hoplocephalus bungaroides) can be identified by its pattern of bright yellow scales, which contrast against its otherwise black body. The yellow scales form several irregular cross-bands across the upper side of the body, and sometimes form splotches on the grey underside (2) (3).

As its common name suggests, the broad-headed snake has a noticeably wide head, which is wider than its neck. The head has an irregular pattern of yellow scales, as well as yellow bars on the scales of the upper lip (3).

The female broad-headed snake generally grows to a larger size than the male (3).

The broad-headed snake can only be found in sandstone ranges in the Sydney Basin and within a 200 kilometre radius of Sydney, Australia. Since the 1970s, this species has not been recorded in rocky coastal areas near Sydney, where it was once abundant (2) (3).

The broad-headed snake is typically found in rocky outcrops surrounded by evergreen heathland vegetation and eucalypt (Eucalyptus) forest (3) (6). It typically dwells in sandstone crevices during the cooler months of the year, but moves into nearby woodland in the warmer months to shelter inside hollow trees (2) (3) (4) (6). Pregnant females and juveniles may remain in rocky habitat throughout the year, using cooler, more shaded crevices during the warmer months (2) (7).

Individual broad-headed snakes, particularly females, have been known to consistently return to the same shelter sites year after year (2) (6) (7).

This small, venomous snake is an ambush predator which may lie in wait for prey for as long as four weeks inside a single retreat site (2) (3) (6). The broad-headed snake typically preys on small lizards, particularly the velvet gecko (Oedura lesueurii) (2) (3) (6) (8) (9). Juvenile broad-headed snakes rely almost exclusively on velvet geckos, but adults also take mammals (9), especially during the warmer months when tree hollows are used as retreat sites (3).

Although the broad-headed snake is venomous, most individuals are small enough not to pose a fatal threat to humans (10).

The broad-headed snake occupies distinct home ranges, and individuals generally avoid sharing spaces with each other. Male broad-headed snakes have been shown not to have overlapping ranges, although the ranges of females may overlap those of males (7).

The female broad-headed snake usually breeds every two years and the litter size, which ranges from 4 to 12, is correlated to the female’s body size. Mating takes place between autumn and spring, and the young are born live, usually between January and April (2). Although female broad-headed snakes usually measure between 50 and 70 centimetres, they can give birth to offspring as large as 20 centimetres in length (2) (3).

Due to its ambush feeding strategy, the broad-headed snake does not feed very frequently, and the young snakes therefore grow quite slowly (2) (3). Female broad-headed snakes tend to mature in six years, while males mature in five years (2).

The broad-headed snake is greatly dependent on sandstone rocks for shelter, and is therefore under significant threat from the collection of sandstone rocks, or ‘bushrocks’, which are increasingly being used for garden decoration (2) (3) (4). As well as removing essential shelter sites for the snake, this reduces the available shelter for its prey and for the spiders and insects on which its prey depends (2) (3). Rock collectors also sometimes deliberately kill snakes (2).

Since the broad-headed snake inhabits areas with a high human population density, its habitat has been subject to wide-scale degradation, and its populations have become fragmented. Although it does occupy national parks, illegal rock collection has persisted in these areas, particularly alongside roads and trails (2).

The broad-headed snake is very selective about the sites it inhabits, and will not dwell in rocks exposed to too much sunlight or that are too wobbly. This complicates its conservation, as it makes efforts to improve the habitat through adding rocks an unlikely solution (2) (6). It also makes the broad-headed snake particularly sensitive to any disturbance of surface rocks (3).

Threats to the woodland areas occupied by the broad-headed snake in summer may also negatively affect this species. Altered fire regimes may affect prey availability and reduce the tree hollows in which the broad-headed snake shelters, while forestry activities can disturb the woodland habitat and remove the large, hollow trees this snake prefers (2) (3).

Illegal collection is also likely to be having a serious impact on the broad-headed snake population, with recent changes to the laws on reptile-keeping potentially exacerbating the problem (3) (11). Non-native foxes and cats may also be predating this species (2) (3).

The slow growth and reproduction of the broad-headed snake, together with its fidelity to specific sites and the low dispersal rates of juveniles, make this species particularly vulnerable to human disturbance and less likely to colonise new areas (2) (3) (7) (9).

Several conservation strategies have been suggested to help preserve the broad-headed snake. Captive breeding has shown some success, although this is limited by a lack of suitable habitat for the reintroduction of the newly-bred juvenile snakes (10). Measures also need to be taken to control the removal and sale of bushrock from areas inhabited by the broad-headed snake (3), and closing or gating of certain roads and tracks may help to reduce illegal rock theft as well as illegal snake collection (3) (11).

The broad-headed snake occurs in a number of reserves (3), and is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that any international trade in broad-headed snakes should be carefully controlled (5).

The specific habitat requirements of the broad-headed snake mean that it may not directly benefit from attempts to restore its habitat by moving new rocks into suitable locations. However, such measures may indirectly benefit the species by increasing the shelter available to its gecko prey (2). As broad-headed snakes do not tend to roam far, habitat restoration may need to be combined with the release of captive-bred or wild-caught juveniles into new areas to aid re-colonisation (7).

Better forest management may be another solution to conserving the broad-headed snake. For example, the pruning of trees in certain areas may improve the suitability of its rock shelters by preventing shading (2). Forestry practices should also be designed to retain suitable trees for the broad-headed snake, and reserves should encompass large forest areas around the sandstone outcrops that this rare reptile inhabits (4) (7).

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more about the broad-headed snake and its conservation:

• Australian Government - Department of Sustainability, Environment, Water, Population and Communities (2011) Hoplocephalus bungaroides. 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=1182
• NSW National Parks and Wildlife Service (1999) Threatened Species Information: Broad-headed Snake. NSW National Parks and Wildlife Service, Australia. Available at:
  http://www.environment.nsw.gov.au/resources/nature/tsprofileBroadheadedSnake.pdf

More information on conservation in Australia:

• Australian Wildlife Conservancy:
  http://www.australianwildlife.org/