Stephens' banded snake (''Hoplocephalus stephensii'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of highly venomous tree snake in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Elapidae. The species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Taxonomy

Gerard Krefft Johann Ludwig (Louis) Gerard Krefft (17 February 1830 – 19 February 1881), a talented artist and draughtsman, and the Curator of the Australian Museum for 13 years (1861-1874), was one of Australia's first and most influential zoologists and ...

described ''Hoplocephalus stephensii'' as a species new to science in 1869. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''stephensii'', is in honour of Australian academic

William John Stephens William John Stephens , FGS, (16 July 1829 – 22 November 1890) was headmaster at Sydney Grammar School, a professor at the University of Sydney and museum administrator. Stephens was born in Levens, Westmorland, the son of the Rev. William St ...

Description

This species of snake grows up to 1 meter in length, with some specimens having been recorded being an upwards of 120cm long. The Stephens' banded snake is the largest species within the

Hoplocephalus ''Hoplocephalus'' is a genus of venomous snakes in the family Elapidae. The genus is endemic to Australia. Three species are recognized. Description Snakes of the genus ''Hoplocephalus'' have a pair of large grooved venom fangs, which are follo ...

genus, weighing up to 250g as an adult. On average, the females of this species are larger than males. This slight

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

is an adaptation that likely improves the reproductive capabilities of females. The anterior scalation of Stephens' banded snake consists of 21 rows of midbody scales, 220 to 250 ventral scales and their singular

subcaudal scales In snakes, the subcaudal scales are the enlarged plates on the underside of the tail.Wright AH, Wright AA. 1957. Handbook of Snakes. Comstock Publishing Associates (7th printing, 1985). 1105 pp. . These scales may be either single or divided (pair ...

can range between 50-70 scales from the anal plate to the tip of the tail. This species has a singular anal plate that covers its cloacal opening. The

ventral scales In snakes, the ventral scales or gastrosteges are the enlarged and transversely elongated scales that extend down the underside of the body from the neck to the anal scale. When counting them, the first is the anteriormost ventral scale that conta ...

of the ''Hoplocephalus'' genus differs from other elapids as they have lateral notches along the caudal border of each of these scales. This adaptation aids with gripping onto branches whilst climbing. Additionally, the occipital scales on the head of this snake are elongated. The body of the Stephens' banded snake is adorned with alternating grey or black and dirty-white bands of colouration on the dorsal side of the snake. These snakes may have over 40 of each colour band from the back of the head to the tip of the tail. Whilst the flat and quadrangular belly of the snake is mostly dirty-white with occasional splotches of grey towards the head and tail end of the snake. The top of this species’ head is typically dark brown in colouration, and they have pale blotches or bars of patterning along their lips. The morphological composition of a slender body and broadened arrow-shaped head also allows for more agile locomotion in an arboreal habitat whilst also having the capability of predating on a large range of species within the

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

. This unique body plan essentially reduces metabolic costs, allowing the snakes to retain energy for longer periods of time.

Distribution and habitat

The Stephens' banded snake is endemic to the east coast of Australia. The distribution of these snakes spans from its northern most range in the Kroombit tops of south-eastern

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

down to the

Gosford Gosford is the city and administrative centre of the Central Coast Council local government area in the heart of the Central Coast region, about north of Sydney and about south of Newcastle. The city centre is situated at the northern extre ...

Area of

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

. Within this coastal range, the species is typically restricted to high-rainfall remnant forest regions, secluded from human intervention. The Stephens' banded snake can be found up to an

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

of 950m above sea level within their geographical range. Studies on the habitat preferences of This species has found that they prefer to reside around 20 metres high in canopy trees. These snakes have a broad tolerance for variations in abiotic and biotic factors such as vegetal communities and climatic changes within the constraints of their remnant forest habitats. The species will favour areas with less rugged terrain as well as hollow bearing trees, dense understory vegetation or rocky outcrops that they may utilise to seek refuge. Individual male Stephens' banded snakes occupy an average home range of 20.2 ha. Whilst the females of the species have a much smaller average home range of 5.4 ha. This difference is likely due to the fact that males may venture out of their typical territories in order to find a viable mate.

Behavior

Stephens' banded snakes have been described as having a nervous and defensive temperament towards other animals. These snakes are relatively solitary animals, only voluntarily interacting with other individuals of the same species during mating season, in which males will actively pursue females to reproduce. If females are apprehensive to reproduce upon the pursuit of potential mates, they may assume a stereotypical posture that is used to prevent males from engaging in

copulation Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetrat ...

. The female will form a tight coil with its body, with its vent in the centre coil, out of reach from the male. Stephens' banded snakes are one of the only predominantly arboreal elapid species in Australia. Other Australian elapidae that exhibit similar arboreality include the

broad-headed snake The broad-headed snake (''Hoplocephalus bungaroides'') is a species of venomous snake in the family Elapidae. The species is restricted to the Sydney Basin in New South Wales, Australia. It is one of three snakes in the genus '' Hoplocephalus'', ...

and the

pale-headed snake The pale-headed snake (''Hoplocephalus bitorquatus'') is a species of venomous snake in the family Elapidae. The species is endemic to Australia. Taxonomy The species was originally described as ''Alecto bitorquata'' by Giorgio Jan in 1859. De ...

, both of which belong to the ''Hoplocephalus'' genus. Stephens’ banded snakes are also capable of living a terrestrial lifestyle depending on the available resources in their environment. The species is nocturnal; thus, they spend a large portion of the day sequestering in the canopy tree hollows within the mesic forests in which they reside. The Stephens' banded snake displays significant reluctance with their heliothermic behaviours. Due to their small size they are at risk of predation. Therefore, these snakes will spend minimal time basking amongst the branches of trees. Typically, they are semi-covered by

foliage A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

so as to offer some means of concealment whilst in this vulnerable position. A study on the basking behaviours of ''Hoplocephalus stephensii'' has revealed that the species only prefers to overtly bask when they are either in late stages of pregnancy, have just fed or are in the process of undergoing

ecdysis Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals typically forms a largely inelastic exoskeleton, it is shed during growth and a new, larger covering is formed. The remna ...

. Throughout the winter season, Stephens' banded snakes stop feeding and undergo

brumation Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be clos ...

in the protection of tree hollows for up to 5 months. During this period of time, their metabolism is significantly slowed, allowing them to conserve energy. These animals are cold blooded, so they are only able to resume digestive processes when temperatures rise again in their environment. Studies on the survivable temperature threshold of these snakes has revealed that their body temperatures may fluctuate anywhere between 11.1 °C to 37.8 °C depending on the climatic conditions. The typical diurnal body temperature of this snake species averages at 28.4°C. The species is at its most active in their natural habitat between the months of September to May. Stephens' banded snakes are highly vagile and may use up to 30 different trees within its range. Territories of individuals may overlap. Despite this, they avoid conspecific encounters.

Life cycle

Studies suggest that Stephens' banded snakes evolved to live a low energy and slow life cycle in response to limited food availability and low temperatures along the snake's geographical range. Males of the species only reach sexual maturity at 3 years of age, whilst females may only reach sexual maturity after 4 years. In Addition, individual females are only gravid every two years and give birth to relatively small litters in comparison to other Australian elapids. Through observations of captive Stephens' banded snakes, scientists were able to note that the species engaged in reproductive behaviours during the spring season. Stephens' banded snakes are viviparous, and the species has been recorded to have anywhere between 1 and 9

offspring In biology, offspring are the young creation of living organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a brood or progeny in a more general way. This ca ...

per litter. In wild populations the average generational length for Stephens' banded snakes is 8 years.

Diet

Stephen's banded snakes are

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

. They are infrequent feeders and have a generalist approach to hunting methods. By implementing a combination of active searching and ambush strategies, they are able to obtain a wide range of prey including; bush rats, pygmy possums, and other small lizards, mice and frogs. Studies have observed that these snakes prefer to inhabit

tree hollows A tree hollow or tree hole is a semi-enclosed cavity which has naturally formed in the trunk or branch of a tree. They are found mainly in old trees, whether living or not. Hollows form in many species of trees, and are a prominent feature of nat ...

that are frequented by small mammalians, often times coiling amongst rodent nests waiting for their potential prey to return. Prey options within the habitat of Stephens’ banded snakes vary on a seasonal basis. The small size of these snakes means that they are unable to feed on the adult variants of most prey species. Instead, they seasonally hunt juveniles of different animals throughout the year as their limited mouth gape prevents them from predating on larger prey. The

neonatal An infant or baby is the very young offspring of human beings. ''Infant'' (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is a formal or specialised synonym for the common term ''baby''. The terms may also be used to ...

size of this species is large compared to other juvenile elapids, measuring an average of 25cm in length. This large size is advantageous at a young age as they are readily capable of consuming a wider variety of species including small

ectotherms An ectotherm (from the Greek () "outside" and () "heat") is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature.Davenport, John. Animal Life a ...

and rodents that live in their resource poor environment.

Venom

The Stephens' banded snake has been described as a ready biter with their subsequent envenoming being potentially fatal. The venom of ''Hoplocephalus stephensii'' is a procoagulant and has typically been described as exhibiting a defibrination-type coagulopathy in patients. Therefore, envenomation will result in a reaction known as

venom-induced consumption coagulopathy Venom-induced consumption coagulopathy (VICC) is a medical condition caused by the effects of some snake and caterpillar venoms on the blood. Important coagulation factors are activated by the specific serine proteases in the venom and as they beco ...

(VICC). Systemic symptoms of VICC include;

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

and

headaches Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result of m ...

abdominal pain Abdominal pain, also known as a stomach ache, is a symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than ...

vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the Human nose, nose. Vomiting can be the result of ailments like Food-poisoning, foo ...

and

diarrhoea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...

as well as

diaphoresis Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distribut ...

. The venom contains prothrombinase, a complex that prompts the production of the thrombin enzyme in the blood. This enzymatic reaction induces micro clotting in the bloodstream of their victims. Effectually, this blocks the flow of blood throughout the body. If left untreated, the clotting will cause blood vessels to rupture. Consequentially, the envenomated victim will experience excessive bleeding. Presently, no anti-venom has been derived from the venom of the Stephens’ banded snake. Despite this, it has been documented that victims of this snake’s envenomation have been successfully treated using up to 4 doses of 3,000 unit tiger snake anti-venom. Despite the lethality of this snake's venom, there has only been one recorded fatality of envenomation. The victim of this fatal encounter was an elderly man in his 60s from the town of Kalang in NSW. Due to torrential rain and flood conditions, a team of SES, ambulance and police rescue worked together to reach and transport the wounded man to

John Hunter Hospital The John Hunter Hospital and John Hunter Children's Hospital (sometimes known as the JHH and JHCH respectively, or more colloquially The John Hunter) is the principal referral centre and a tertiary hospital for Newcastle, and northern New South ...

. However, medical assistance was unable to remediate him in time.

Genetics

Genetic research pertaining to the molecular

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

of the ''Hoplocephalus'' genus has revealed that Stephens’ banded snakes displays up to 2.6–3.1% in genetic divergence with the

(''Hoplocephalus bungaroides''), making these two coastal species the most closely related within the genus. Whereas, the

(''Hoplocephalus bitorquatus'') a more inland relative, genetically diverges up to 7.8–8.3% with Stephens' banded snake. ''Hoplocephalus stephensii'' displays low genetic diversity amongst extant populations. Wild populations of the species exhibit 9 different mitochondrial haplotypes. Within Individual populations, the snakes may exhibit anywhere between 1 to 3 haplotypes with single base pairing differences. Throughout the entire wild population of Stephens' banded snakes, the largest genetic divergence has been observed between the far north and far south populations with a 1.7% sequence divergence. Through genetic analysis, scientists have determined that these populations of Stephens' banded snakes separated from each other approximately 850,000 years ago.

Threats and conservation

Stephens' banded snakes are listed as near threatened in the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...

. In the last 200 years since the onset of European colonisation in Australia, this species has experienced a steady decline in population. Scientists have been able to use radiometric tracking technology in order to study the movement patterns of Stephens' banded snakes throughout their natural habitat. These studies have suggested that the declining populations of the species is primarily due to

Habitat fragmentation Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological processes ...

coupled with a low fecundity and growth rate. This is a result of anthropogenic disturbances such as

deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated d ...

and habitat encroachment by urban developments as well as livestock farming. Due to the rarity of these snakes, the illegal capturing of wild specimens for commercial use has proven to be detrimental to the survivability of these wild populations. In addition, invasive species have also introduced zoonotic diseases and increased competition for resources. In an effort to maintain the survivability of Stephens’ banded snakes, the NSW government has registered this species under the landscape management section of the ‘Saving Our Species program’, by way of the Biodiversity Conservation Act of 2016 No. 63. This was done in order to establish a recovery strategy to reconnect and revegetate the species' fragmented habitats.

Captivity

The New South Wales government permits the private ownership of these snakes. The NSW Native Animal Keepers Species List of 2016 specifies that individuals need to register with the Department of Planning, Industry and Environment in order to acquire either a R3, R4 or R5 Level license. In order to obtain this level of licensing for the legally ownership of Stephens' banded snakes, keepers must provide proof of a first-aid certificate, an escape proof enclosure, a lockable room, an emergency response plan as well as references that confirms the applicant's experience and skills in handling venomous reptiles.

Ex situ Svalbard GLOBAL SEED BANK, an ''ex situ'' conservation. ''Ex situ'' conservation literally means, "off-site conservation". It is the process of protecting an endangered species, variety or breed, of plant or animal outside its natural habitat; ...

observations of this species has revealed that Stephens' banded snakes, when kept in

captivity Captivity, or being held captive, is a state wherein humans or other animals are confined to a particular space and prevented from leaving or moving freely. An example in humans is imprisonment. Prisoners of war are usually held in captivity by a ...

, can potentially grow larger and reproduce more rapidly than their wild counterparts as a result of consistent food availability.