DANGEROUS SNAKES OF PAPUA NEW GUINEA
Ask any Papua New Guinean what the most dangerous snake in their country is, and the resounding reply will be "Papuan black" - a name that is widely used for any black or dark coloured snake (and there are many that meet this description). There is of course a genuine Papuan blacksnake (Pseudechis papuanus) which was once common throughout southern Papua New Guinea, and according to early studies on snakebite, a significant cause of clinical envenoming. This snake is now becoming increasingly rare, and accounts for less than 5% of snakebites in Central province.
So what then are the main medically important species?
Although there are many venomous species in Papua New Guinea, the majority present only minimal risk to humans, and the major burden of serious envenoming is caused by just five species:
Papuan taipan (Oxyuranus scutellatus)
Description: A large, fast-moving snake that is typically greyish, dark brown to black above with a broad orange-red dorso-vertebral stripe that extends along most of the back. The belly can be white to orange in colour. The tip of the nose and the sides of the lips are usually creamish. There is local and regional variation in colouration and even specimens from the same location may differ considerably in colour. Head long and distinct from powerfully muscled but slender neck and forebody. Papuan taipans have large distinctive heads that are crudely rectangular; the body is large, long and muscular; the tail is round and tapers to a fine tip. The mouth is large and the lower jaw articulates well back beyond the labial scales giving these snakes an enormous gape and the ability to accommodate very large prey items.
Scalation: Dorsal scales in 21-23 rows at mid-body, and most are keeled, particularly on the neck; 220-250 ventrals; anal single; 60-80 paired subcaudals.
Body Size: Average length: 1.8 metres for females and 2.0 metres for males; maximum length: claimed to be 3.4 metres, but specimens over 2.6 metres long are rarely seen.
Distribution: This species is restricted to grasslands and savannah woodlands in the southern coastal provinces of Milne Bay, Central (including the National Capital District), Gulf and Western provinces. Absent from the lowland rainforest plains between the Purari and Bamu Rivers. Specimens have been recorded from the mainland near Samarai Island in Milne Bay province and are common in areas of open savannah woodland and grassland west through the Magarida (Iruna), Boru, and Marshall’s Lagoon districts. The range extends along the coastal littoral and into the foothills of the Owen Stanley Range near Sogeri, encompasses the National Capital District and continues through Mekeo into the eastern third of Gulf province to just west of Malalaua near Koaru. Slater records that the species also occurs in the isolated grasslands around the Vailala River west of Kerema.
The species is absent from the Kikori Basin but Papuan taipans have been found on both sides of the Fly River, and bites have been recorded in Balimo, Suki, Wipim and Morehead. None could be found on Daru Island during fieldwork in 2004, and there are no hospital records of envenomation originating on the Island. Papuan taipans have been collected by herpetologists in southern West Papua (Indonesia) around Merauke and west to the Wildoman River region. There has also been a confirmed record from Saibai Island (Australia).
Habitat: Inhabits grasslands and savannah woodland to an altitude of around 400 metres. Adapts well to areas of human activity and often lives in village gardens and residential areas. Papuan taipans are relatively common in the suburbs of Port Moresby especially around Gerehu, Waigani, Erima, Korobosea and Kaugere. In both urban and rural areas these snakes are often found close to human settlements or in and around garden plots. In rural areas of Central and Gulf province Papuan taipans are common in areas of kunai (Imperata cylindrica) or pit-pit (Themeda triandra) grassland, melaleuca and acacia scrub, savannah (Eucalyptus spp.) woodland and other ‘dry’ tropical habitats. Papuan taipans often cross gravel roads transecting large expanses of pit-pit cane or kunai grass, especially in the Mekeo, Rigo and Kupiano-Moreguina districts.
Diet: Feeds on warm-blooded prey; primarily rodents and small mammals to the size of bandicoots, but also known to eat ground-dwelling birds. Appears unaffected by the introduction of the cane toad (Bufo marinus), which is thought to be a cause of declines in frog-eating species. As other species continue to decline, the proportion of snakebites by this species will rise.
Reproduction: Oviparous producing 1-2 clutches of 16-22 eggs each year. Mating has been observed between June and July. The normal incubation is 60-66 days, but female snakes usually leave their eggs within a few days of laying them.
Activity: Papuan taipans are usually only active by day. Most are seen moving around between early to late-morning, and then again during the mid to late-afternoon. During research in PNG no specimens were observed later than 6.30 pm. Not enough is known to tell if taipans are more active at different times of the year.
Behaviour: A very shy, extremely nervous snake that tries to avoid human contact, but which will defend itself violently when threatened, making them exceedingly dangerous adversaries. Taipans are capable of ferocious self-defence and may inflict multiple bites in rapid succession using a ‘snap and release’ strategy, where larger amounts of venom are injected with each subsequent bite. Taipans also strike higher than other venomous species; bites to the calves or even above the knee can occur. This is the only snake in PNG likely to ‘attack’ a perceived threat.
Medical importance: The most dangerous species of venomous snake in Papua New Guinea, with the highest venom yield and the longest fangs. There is considerable evidence that this snake causes most of the serious snakebites admitted in Central province. Lalloo et al (1995) showed, using a specific diagnostic test (EIA), that 82.3% of serious snakebites in Central province were caused by Papuan taipans.
Venom: The two most important components of taipan venom are (1) an irreversible neurotoxin that destroys nerve endings, and (2) a powerful activator of a blood clotting factor (prothrombin), which leads to the incoagulable blood seen in many taipan bite patients. In addition to these toxins there are also several other minor components which contribute to the effects of envenoming.
Papuan taipan (Milne Bay Province, PNG)
Papuan taipan hatching from egg
Papuan taipan laying eggs
Distribution of Papuan taipans in PNG
New Guinea death adders (Acanthophis laevis & Acanthophis rugosus)
Description: Short, thickset snakes with large angular heads and raised supraocular scales that give the appearance of small horns. The tail is thin and ends in a soft ‘spine-like’ tip. Colour varies enormously and background body colour can vary from almost black to red, brown, yellow or light grey interspersed with alternate light and dark transverse bands which are most prominent when the snake is threatened. Smooth-scaled death adders (Acanthophis laevis) usually have a rather subdued pattern, whereas most rough-scaled death adders (A. rugosus) are very contrastingly patterned. The labial scales are usually white with dark brown or black streaks. The belly is white with darker spots.
Scalation: Dorsal scales in 21-23 rows at mid-body; 110-135 ventrals; anal single; 36-60 subcaudals – anteriorly single, paired posteriorly. The dorsal scales of A. laevis are usually smooth or weakly keeled, while those of A. rugosus are strongly keeled and look rough, particularly on the neck.
Body Size: Average length approximately 50 cm, maximum 90-100 cm. Females longer than males. There are reports of dwarfed populations in the Highlands and unusually large specimens in river valleys in northern PNG, but in the latter case, specimens are lacking, and it is likely that large ground boas (Candoia aspera) are being mistaken for death adders.
Distribution: Smooth-scaled death adders (A. laevis) occur in all of the mainland PNG provinces and on closer islands such as Karkar, Yule, Daru and those in the mouth of the Fly River. It is also found throughout West Papua and on Seram and the Aru islands. The rough-scaled death adder (A. rugosus) is currently only known from south-eastern West Papua (Merauke region), but probably also occurs in the south-west corner of the South Fly District around Weam and Morehead.
Habitat: Death adders occur in a wide range of habitats including lowland grasslands and savannahs, sago swamps, monsoonal forests, woodlands, rainforest, coffee, tea and cocoa plantations, village gardens, highland grasslands and other montane environments. These ground dwelling snakes can be common in any area with abundant leaf litter, grass trash or other ground cover in which they can hide. They often occur around forest margins, or on the periphery of garden plots, and near the sides of walking tracks: all areas of filtered sunlight and abundant lizard prey.
Diet: Predominantly small ground-dwelling lizards, frogs and occasionally small rodents or ground birds that are attracted to wriggling of the snake’s grub-like tail. The tail does not contain a poisonous sting.
Reproduction: One of the very few venomous snakes in PNG which produce live-born young in litters of 8-12. Juveniles range from 0.17-0.24 metre at birth.
Activity: Generally nocturnal, these snakes usually sit under cover during the day, often close to pathways along which small animals (and people) regularly travel. If disturbed (by the burning of grass for example) they may move around during the day. Often seen crossing roads and paths at night, especially at dusk when people are returning home from the garden or bush. Although this represents one danger period for contact with this snake, many bites occur in daytime when people step on the sleeping snake, or touch it as they reach down to pick up something.
Behaviour: Death adders are unique among PNG snakes in their reliance on a ‘sit and wait’ ambush feeding strategy, which means that they will remain motionless on the ground even when approached very closely. These inoffensive snakes become a significant snakebite threat because of this behaviour. While most snakes will flee from an approaching human, death adders rely on remaining motionless to avoid detection, but if touched will strike reflexively.
Medical Importance: Although considered responsible for only about 10% of serious snakebites in Central Province, death adders are the major cause of snakebites throughout much of the rest of PNG, and in particular northern PNG where they are the most commonly encountered venomous snake (Lalloo et al, 1995a, 1996). In Gulf province, death adders are the major cause of envenoming in communities around the Purari, Kikori and Turama Rivers to the west of Kerema (Williams, 2005). Death adders are also the dominant venomous species in most of the forested regions of Western Province, and are the most common cause of snake bites in the Rumginae, Tabubil, Mougulu and Nomad areas.
Venom: Death adder venoms are rich in postsynaptic neurotoxins, as well as a variety of minor components, including weak anticoagulants. Specimens from neighbouring Papua have been found to contain myotoxins in their venoms, but rhabdomyolysis is not common in patients bitten by death adders in PNG, and paralysis is the major clinical effect of envenoming.
Smooth-scaled death adder (Central Province, PNG)
Smooth-scaled death adder (Madang Province, PNG)
Newly born smooth-scaled death adders
Distribution of death adders in PNG
New Guinea death adders (Acanthophis laevis & Acanthophis rugosus)
Description: This is a thick-bodied snake with an extremely variable colour pattern based on a greyish head and pale yellow, creamish or salmon coloured body with dark-tipped scale edges that give rise to broad dark bands from midbody to the end of the tail. Juvenile snakes are much more prominently marked than adults. This snake is often known as the ‘white snake’ in Madang province due to its pale body colour. As the name implies the eyes are small, dark and slightly recessed.
Scalation: Midbody dorsal scale rows are in 15 rows; ventrals number 178-225; the anal is divided and the 36-55 subcaudals under the tail are paired.
Body Size: The average total length is between 1.2-1.7 metres; large specimens of 2.1-2.3 metres have been recorded, but most specimens are much smaller.
Distribution: Recorded from northern Western province (Kiunga to Star Mountains) and all of the Highland and New Guinea provinces. The most concentrated populations appear to be found on islands off the northern coast of PNG. British herpetologist Mark O’Shea has collated a wealth of distribution data for this species. Small-eyed snakes are common on Karkar Island off the coast of Madang and Mark O’Shea records them from villages such as Mom, Kurum, Miak, Kulkul, Kaviak, Bulu and from around the Gaubin Lutheran Mission. There are also numerous records from the nearby mainland including Madang itself, Alexishafen, Malolo, Nageda and Bogia. It is probable that the snake is found on Manam Island off Bogia. Further along the coast it is common near Wewak and Aitape and occurs on Walis Island. Other records include Popondetta, Buna, Kokoda and Ilimo in Oro province; Garaina, Wau and Bulolo in Morobe province; and Telefomin, Tabubil, Ningerum, Rumginae, Takam and Munbil in Western province. Records are scattered throughout the rest of the Highland and Mamose provinces but this may be due more to the crepuscular nature of the snake than to a lack of abundance. There are isolated records in Gulf, Southern Highlands, Central and Milne Bay provinces.
Small-eyed snakes are widely distributed in West Papua and the Aru Islands from as far afield as Montagne de Karoon on the north-western side of Waigao Island to Jayapura near the Papua New Guinea border in the east of West Papua province. There are museum records from Batante Island and from Misool Island north of Seram. In Geelvink Bay small-eyed snakes have been found on Jobi and Numfoor Islands and it also occurs on Mansinam Island off the eastern coast of Sorong. Mainland records include the mountainous Baliem Valley, Wasior on the Wandammen Peninsula, Fakfak on the Onim Peninsula, and Mimika River and Merauke in the south.
Habitat: This snake lives in wet environments from sea level to over 1,500 metres. Common in monsoonal forests, lowland swamps and rainforests where it lives in ground debris. There are some well-established and abundant regional populations, often in and around Coconut plantations (especially Karkar Island) where large numbers of small-eyed snakes lives in old coconut husk piles.
Diet: Believed to be an opportunistic feeder, preying on a wide variety of small ground dwelling animals including lizards, rodents, frogs and particularly other snakes, including its own species.
Reproduction: Very little is currently known about this egg-laying snake although the Moscow Zoo in Russia successfully hatched two juveniles from a clutch of five eggs in 2004.
Activity: Although generally considered to be a ground dwelling, largely nocturnal species, there is a single report from West Papua of a serious snakebite having been caused by a large M. ikaheka that was caught in a bird trap high in a tree (Warrell et al., 1996). During the dry season this snake is often found in old, overgrown coconut husk piles, but is often encountered moving on the ground at night during rainfall. On the PNG mainland small-eyed snakes living in natural forests are rarely encountered and nothing is known about their daily or seasonal activity cycles.
Behaviour: These are shy, generally inoffensive snakes until disturbed. If handled small-eyed snakes can be very aggressive and will bite readily, often chewing down hard and refusing to let go of its victim. Small specimens are very agile and surprisingly fast, while large snakes tend to be heavy-bodied. The small eyes and smooth body scales are specific adaptations for burrowing among ground debris and loose topsoil in search of food.
Medical Importance: This highly venomous snake is believed to account for only a small proportion of snakebites in mainland regions of Madang, East Sepik and Sandaun provinces. However, a study of M. ikaheka bites found that approximately 40% of the envenoming on Karkar Island were due to this snake (Warrell et al, 1996). Bites by this snake also appear to be relatively common in the Rumginae area of Western Province.
The presence of small-eyed snakes in coconut plantation husk piles is a potential hazard to plantation workers, as these snakes often emerge from within piles to hunt just as workers are returning home at dusk. Although local people in the Omati and Baina areas of Gulf province say that this is a common snake, it is rarely a cause of snakebite as it lives in thick rainforest areas where few people venture at night and this may explain why few people seem to be bitten on the mainland.
Venom: Small-eyed snake venom contains a number of unique toxins that are not present in other PNG snake venoms. Although these produce clinical effects similar to those seen in bites by other species, such as neurotoxicity, myotoxicity and bleeding, the unique properties of the venom mean that antivenom may not neutralise some components as well as others. Laboratory experiments suggest that CSL polyvalent antivenom is effective in the treatment of bites by this snake, but more evidence is required to determine whether this applies in clinical cases.
Small-eyed snake (Oro Province, PNG)
Small-eyed snake (Madang Province, PNG)
Newly hatched small-eyed snake at AVRU/UPNG Serpentarium
Subadult small-eyed snake (Madang Province, PNG)
Distribution of small-eyed snakes in PNG
New Guinea brown snake (Pseudonaja textilis)
Description: A slender, very fast-moving snake that may be from tan to dark brown in colour dorsally with a cream to yellow belly that is speckled with greyish-brown spots. Juveniles have a black patch on the top of the head and a black bar across the nape of the neck; some also have up to 50 black cross bands that eventually fade with age in most specimens, although some adults retain faint banded markings.
Scalation: Dorsal scales in 17 rows at midbody; 200-210 ventrals; anal divided; 45-75 paired subcaudals (in some snakes a few of these are single anteriorly). Brown snakes lack the temporolabial scale which is present on the heads of many other species in PNG).
Body Size: Average length is from 1.2-1.8 metres; maximum length is 2.45 metres.
Distribution: Most common in Milne Bay and Oro provinces. Specimens have been found near Dogura and Wedau, Baiawa, Tarakwaruru and Menapi Mission near Abuaro on the northern side of Milne Bay province. Chris Austin collected specimens near Wamawamana in Milne Bay, and Mark O’Shea records specimens from Buna, Popondetta and Embogo in Oro province. Mark collected specimens on behalf of AVRU during field work near Heropa, Oro Province in 2006. A handful of specimens have been recorded in Central province from near Hisiu, Tapini, and Goldie River as well as Six-Mile and Nine-Mile in the NCD. Specimens have been collected in West Papua near Merauke, and there are anecdotal reports from Western province near Weam and Morehead.
A study of the biogeography of New Guinea brown snakes (Williams et al, 2008) is currently in press.
Habitat: Kunai (Imperata cylindrica) or pit-pit (Themeda triandra) grasslands and savanna woodlands comprising Acacia, Eucalyptus and Melaleuca tree species. Brown snakes adapt well to areas of human settlement, at least in Australia.
Diet: Very opportunistic, but primarily small lizards and rodents. Unlike other venomous snakes in PNG this species will use constriction to hold and subdue prey in much the same way as non-venomous pythons.
Reproduction: Females lay eggs in clutches of up to 22 eggs in October-November.
Activity: Almost exclusively diurnal and unlikely to be seen at night. Brown snakes are very active foraging species that are often encountered moving around searching for food or shelter.
Behaviour: If approached this is a very aggressive snake that will defend itself with little encouragement. Brown snakes typically adopt a very characteristic defensive stance in which they lift the front third or more of the body high off the ground in a rigid S-shape and hiss violently while holding the mouth open. From this position the snake will make repeated lunges at an antagonist, and will strike several times.
Lalloo et al (1995) reported that this species was responsible for 1.8% of the serious snakebites in their study within Central province, and reported bites from Tapini, Goldie River, Kapari and 9-Mile. Although the venom is extremely toxic, both the yield and the fangs used to deliver it are small.
Venom: Brown snake venom contains very powerful toxins that cause bleeding and coagulopathy, and although potent neurotoxins are also present, it is the typically the effects on the blood that are the most clinically important.
New Guinea brown snake (Milne Bay Province, PNG)
New Guinea brown snake (Oro Province, PNG)
Distribution of brown snakes in PNG
Papuan blacksnake (Pseudechis papuanus)
Description: As the name implies these snakes are typically gunmetal black both on the dorsal (back) and ventral (belly) surfaces. The tip of the nose and the throat may be cream to yellow in colour. Rare brown-coloured specimens have also been recorded. Smaller specimens are slender while larger snakes can be quite robust. The head is indistinct from a thickset neck, unlike in the Papuan taipan (O. scutellatus) in which the head is clearly distinct from the slender neck.
Scalation: There are 19 rows of dorsal scales; 220-230 ventrals; a divided anal scale and from 48-65 subcaudals (single anteriorly, but paired posteriorly).
Body Size: Average length: 1.2 metres; maximum length: 2.1-2.2 metres.
Distribution: Specimens have been recorded in Milne Bay, Central, Gulf and Western province, as well as in neighbouring southern West Papua. The current status of the species in Milne Bay and Central provinces is unknown; very few specimens have been reported over the last 25 years, and only one dead specimen has been positively identified in Central province since 1992. Before the, the last confirmed records from Central province were three specimens sent to the National Museum in the early 1990’s, two from Veifa’a and one from Moreguina (Lalloo et al, 1994).
Blacksnakes have been found near Kukipi in Gulf province, and one was responsible for a death there in the 1980’s (Williams, 2005). They appear to be absent from the Kikori Basin, as pictures of blacksnakes were not recognised by local people. A blacksnake was sighted but not captured during a 2007 AVRU field trip to Milne Bay Province at the eastern end of the PNG mainland.
The only other confirmed identifications since 1992 have been in the South and Middle Fly districts of Western province. Specimens have been collected from Kunini, Oriomo River, Wipim, Iamega, Bensbach and near Weam. A blacksnake was identified as the snake responsible for a fatal snakebite near Balimo in 2004.
There are reports that Papuan blacksnakes remain common in West Papua near Merauke, and specimens were recently collected on Saibai Island followed by confirmed identification of the species on Boigu Island (both Australian islands in Torres Strait).
Habitat: Coastal swamps and marshland, monsoonal forests, bamboo thickets and occasionally savannah woodland. In the past specimens have been found in rubber tree groves in the Abau district, and in rainforest around Veifa’a.
Diet: Opportunistic, but prefers frogs. One hypothesis for the apparent decline in numbers in Central province is that the spread of the poisonous introduced cane toad (Bufo marinus) has resulted in regional extinction.
Reproduction: This is an egg-laying snake, producing clutches of 12-18 eggs.
Activity: This is a diurnal snake that is more likely to be encountered in daylight when it comes out of hiding to bask or hunt for food. In West Papua specimens have been collected in the early morning basking close to the edge of sago palm lined river banks. Specimens have been reported basking near the edges of forest thickets near Kukipi in Gulf province.
Ken Slater noted in the 1960’s that these snakes were more likely to be seen during the late dry season, but local people in the South Fly District of Western province say that most specimens are seen basking during breaks in heavy rain during the wet season months of March and April.
Behaviour: Ken Slater, who collected many Papuan blacksnakes during the 1950’s and 1960’s for antivenom production, believed that it was a shy snake which almost always attempted to escape when disturbed, but noted that if provoked it would bite with minimal provocation.
Medical Importance: A study of snakebite in the 1990’s using a specific diagnostic test (EIA) found that only 4.2% of the serious snakebites admitted to PMGH over a thirty month period were caused by bites from Papuan blacksnakes. No specimens have been reliably identified in Central province since 1992, and the only blacksnakes caught since then have come from the South Fly district of Western province, and from neighbouring West Papua.
Venom: Blacksnake venom contains a number of components that have neurotoxic, anticoagulant, and haemorrhagic activity. One of the identified toxins has potential myotoxic activity (Kamiguti et al, 1994).
Papuan blacksnake (Saibai Island, Australia)
Papuan blacksnake (Saibai Island, Australia)
Papuan blacksnake (Western Province, PNG)
Distribution of Papuan blacksnakes in PNG
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