Pale-headed Snake

Introduction

A dependency on old trees for food and lodging makes the Pale-headed Snake vulnerable to poor forestry and farming practices.

Identification

A slender snake, with a broad head distinct from the muscular body. The back, sides and tail are blackish to greyish dark brown (inland forms are generally paler) without any pattern. The head is a lighter grey in colour, with a series of dark spots along the temporal region and also bordering the distinctive white nape stripe at the back of the head. Lips are usually strongly barred with dark grey and cream. Underneath, the ventral colour is creamy grey, sometimes with darker flecks. Body scales are smooth and matt to slightly glossy in appearance. Ventral scales are angled on the lateral edge, creating a keel and giving the body a "bread-loaf" shape in cross-section. Eye is medium-sized and brownish, with an orangey rim around the pupil.

Midbody scales in 19 or 21 rows, ventrals 190-225, anal and subcaudal scales single.

Habitat

Pale-headed Snakes can be found in wet and dry sclerophyll forest, and open woodlands (especially Callitris woodland) on floodplains and near watercourses. They are strictly arboreal and rely heavily on old and dead standing trees with hollows and exfoliating bark for shelter sites.

Distribution

The species has a discontinuous distribution along the coast, ranges and western slopes of eastern Australia, from south-east Cape York, Queensland to around Gosford in New South Wales. It has the largest distribution of the genus Hoplocephalus.

Biomaps map of Pale-headed Snake specimens in the Australian Museum collection. http://www.biomaps.net.au/biomaps2/mapam.jsp?cqn=Hoplocephalus%20bitorquatus&cql=sn&csy=Square

Feeding and diet

The snake eats a variety of vertebrates, particularly tree-dwelling species, including frogs, geckos, skinks and bats. Examination of museum specimens revealed that frogs were the most common prey item (77 percent of 26 prey items). Pale-headed Snakes hunt out in the open at night; however during the day they may remain active within their shelter and ambush other creatures also taking refuge.

In captivity, Pale-headed Snakes will eat small mammals such as mice.

Other behaviours and adaptations

The Pale-headed Snake, along with the other members of the genus Hoplocephalus(broad-headed snakes) are the most arboreal of the Australian venomous snakes (family Elapidae). The slender body and ventrolateral keel allow the snakes to gain purchase on ledges and crevices and grip the climbing surface. This body design is also shared by several other Australian climbing snakes, including the Common Green Tree Snake Dendrelaphis punctata and the Brown Tree Snake Boiga irregularis (family Colubridae).

Breeding behaviours

Examination of museum specimens showed that male Pale-headed Snakes appear to be sexually mature at a snout-vent length of 362mm and females at 384mm. The mean snout-vent length of gravid females was 512mm.

Mating behavior has been observed mostly in captive individuals. Behaviour interpreted as courtship took place in both spring (October) and autumn (April), and actual mating in spring (September), summer (February) and autumn (March, May). Courtship consisted of “frantic” tail wagging, with the male rubbing and twitching his body along the female’s body. Mating can occur at night and may last for several hours - one mating went from late at night until the following morning.

In the wild, females with very large follicles have been found in mid-spring (October) and gravid females have been found in early summer (January). The species is live-bearing, and give birth to between 2 and 11 young measuring around 26-27cm long. In captivity, females appear to breed only every second year, even with regular feeding, so it is reasonable to assume that wild individuals do not reproduce annually.

Management

The Department of Environment and Conservation NSW (DEC) has identified the Pale-headed Snake as being vulnerable in NSW, and likely to become endangered if protective measures are not implemented. Various threats to the Pale-headed Snake include:

• Clearing and fragmentation of habitat.
• Forestry practices which result in loss of old or dead trees.
• Too frequent burning for fuel reduction or grazing management which destroys old and dead trees and removes understorey vegetation.
• Illegal collection of snakes from the wild (Copyright Department of Environment and Conservation (NSW))

DEC has developed a number of action plans to address these threats and help recover the Pale-headed Snake in New South Wales (visit www.threatenedspecies.environment.nsw.gov.au for further information).

Danger to humans

The Pale-headed Snake is a shy but nervous species, and easily agitated if cornered. When disturbed they quickly assume a threat position by holding the head and neck in a tight S-shaped loop, flattening the head and facing the intruder, sometimes with the mouth slightly open. If the intruder comes within reach the snake will strike without hesitation, delivering multiple bites in quick succession. Although there have been no recorded fatalities from this snake, an envenomation can produce some unpleasant symptoms, including severe headache, blurred vision, localized pain, and abnormal bleeding. Medical attention is advised for anyone receiving a bite from this species.

References

Cogger, H. (2000) “Reptiles and Amphibians of Australia”, Reed New Holland

Greer, A.E. (2006) “Encyclopedia of Australian Reptiles : Elapidae”, Australian Museum

Ehmann, H. (1992) “Encyclopedia of Australian Animals : Reptiles”, Australian Museum, Angus & Robertson

Mirtshin, P. and Davis, R. (1991) “Dangerous Snakes of Australia”, revised edition, Ure Smith Press

Further reading

Wilson, S. and Swan, G. (2008) “A Complete Guide to Reptiles of Australia”, Reed New Holland