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australia:snakes

Australian snakes

Introduction

  • most of the world's top 10 venomous snakes reside in Australia!
  • snakes in Australia are a protected species!
  • the venomous snakes are Elapids of which there are 90 terrestrial species which account for 57% of all terrestrial species in Australia, and the non-venomous pythons 1)
  • Australian is home to over 130 species of the 320+ known species of Elapid snakes (including sea snakes)
  • all Australians and travelers to the Australian bush or coastal regions should know how to avoid and how to survive a snake bite.
  • snakes eat frogs, eggs, small mammals, lizards and even other snakes
  • snakes are active when their body temperatures are between 28 and 31 °C and thus they thermoregulate by basking in warm sunny spots in the cool early morning (eg. on your pathway) and rest in shade in the middle of hot days, and may reduce their activity in hot dry weather in late summer and autumn
  • the only time two snakes are in the same place is during courtship and mating. Otherwise the larger snake will usually kill and eat the smaller one
  • snakes can hear low pitch sounds (below 600Hz - human voice is 100-250Hz, at least at 85dB such as a loud voice at 1.2m) and feel vibrations but have trouble hearing higher pitched sounds
    • pythons seem to go towards sounds displaying curiosity
    • ambush predators such as death adders tend to move away from sounds presumably to avoid being stepped on
    • fast moving day time predators such as browns and taipans seem to display defensive and cautious behaviours, signalling potential avoidance behaviour from raptors
  • snakes generally will try to make their way to their preferred escape route and last known safe haven, but sometimes they make poor choices when threatened and the eye sight is relatively poor - if a human is between them and their safe haven they may adopt a defensive raised posture to try to signal to you to get out of their way and then they will approach their safe haven which may appear they are chasing you but they are not!
  • if you approach and harass them they respond with a strike and a bite, although, fortunately, most are dry bites which do not envenomate - never try to catch a snake unless you are trained to do so - call a snake catcher!
  • snakes like to hide under shelters such as sheets of iron roofing, concrete slabs, piles of wood or rocks, etc - take great care when lifting these up.

Evolution

  • snakes evolved from lizards c120-150mya
    • NB. “goannas” (monitor lizards) evolved 90mya in the Nth Hemisphere and migrated to Australia 15mya where they evolved into 28 species
  • Pythons (lay eggs, have a pelvic remnant, two lungs, and did not make it to America until recently) diverged from Boa (give birth to live young) in the Cretaceous period and migrated from Asia to Australia and New Guinea via Wallacea c8-14mya
    • ancestors of Morelia split from the Python tree c35mya 2)
      • Morelia sp evolved 20-22mya
        • Morelia spilota evolved c8mya
  • Elapids (including sea snakes) appear to have evolved from an Asian ancestor 38mya and then rapidly diversified into:
    • coral snakes (30-25mya)
    • Afro-Asian clade of cobras and mambas (30-25mya)
    • Australasian clade including Bungarus (Kraits) and Elapsoidea (African garter snakes) (Hydrophiinae) 25mya
      • semi-aquatic sea kraits (Laticauda)
      • terrestrial Australian Elapid snakes
        • Pseudechis sp 17.5mya
        • two burrowing lineages (Vermicella+Neelaps, Simoselaps+Brachyurophis) 17mya
        • Pseudonaja and Oxyuranus ancestor 14mya
      • viviparous sea snake (Hydrophiini) ancestor 16mya
        • Australepis and Notechis ancestor 12mya
        • Hydrophis 8mya
  • all continents became colonised with snakes by 30-25mya
  • it would seem the Australian elapids are all fairly closely related to each other as a relatively snake-free Australian continent was colonised only 25 mya 3)
  • morphological and biochemical data have suggested a close relationship between Australian terrestrial proteroglyphs and hydrophiid sea snakes
  • prey preference drives the evolution of venom composition and toxicity in snakes
  • AVOID snake bites by:
    • ALWAYS be vigilant when outdoors
    • never trying to catch them or corner them
    • avoid walking where you cannot clearly see the path and even then always be on the look out
    • if walking on paths less than 1m wide without clear vision, wear boots, thick long trousers such as jeans (or long gaiters)
    • when walking over logs fallen on a path take care there is not a snake on the other side
    • if gardening, keep you eye out and if picking something up throw it away from you not towards you
      • snakes like to hide under objects - take great care lifting such objects
    • when camping, camp in a clearing rather than next to tall grass, bushes as snakes are less inclined to come into open areas especially if humans are around
    • take care on very hot nights outdoors as snakes may be hunting (they are not usually active at night unless its hot)
    • understand snake characteristics and behaviour:
      • snake teeth of Victorian venomous snakes are generally less than 1cm long so unlikely to envenomate if wearing thick trousers
      • most snakes will display an aggressive behaviour by raising their heads and feigning strikes as a defence mechanism - and will only strike you if you get too close and they feel threatened - even then, most will not waste their precious venom on you in a bite
      • once snakes are in grasses more than 15cm or so high, you will have trouble seeing them
      • most snakes will flee if they are aware of you coming
      • many snakes will play dead if they did not have a chance to flee
      • some snakes will just want to enjoy the warmth of the sun on a path especially in the morning as they warm up and you will just have to find your way around them or wait for them to vacate their prized spot
  • when hiking be prepared for a snake bite
    • take first aid - bandages to create a mildly compressive bandage to slow lymphatic spread of venom (NOT that tight that it cuts off your circulation!)
    • take a communication device such as a personal radio beacon especially if going to a location without mobile phone access
    • understand that you need to remain inactive to reduce lymphatic circulation speed and get to medical help as soon as possible - mostly you have a few hours if first aid has been applied - deaths within minutes is rare but can happen

Victorian snakes

  • the main venomous snakes in Victoria (Eastern Brown, Tiger, Copperhead and Red bellied black snake) are all diurnal but may hunt for prey on warm nights (especially the red-bellied black snake which does not like very hot days over 40degC and will thus hunt at night instead on those days)
  • the main venomous snakes in Victoria are mainly found on the ground or close to the ground but can rarely be seen on wire fences and climbing hedges or trees in search of birds
    • their prey is usually under 300g - other reptiles, mammals, birds, frogs, eggs, etc but larger snakes will kill and eat other large snakes
  • nocturnal snakes include the Bandy Bandy snake in northern Victoria, the rarely seen secretive small eyed snake which hunts sleeping skinks in south-eastern Victoria and non-venomous pythons which are mainly in north-eastern Victoria

Tiger snake

  • Notechis sp
  • 17% of snakebites in Australia
  • these are also the main snakes living in Tasmania (where a sub species, the Black Tiger snake also resides)
  • relatively poor eyesight and slower moving than a brown and thus more likely to be trodden upon
  • in Victoria, the species is the Mainland Tiger Snake (Notechis scutatis) which usually grows to 0.9m but can grow to 2m and prefers coastal areas and wetlands
  • these snakes flatten their body and raise their heads if threatened
  • they can live 10-15 years and average 1-1.2m in length
  • are good swimmers and can stay underwater for at least up to 9 minutes to avoid terrestrial predators
  • they are solitary and only interact with other Tiger snakes when they mate in Spring and at this time the males can be aggressive and fight other males for up to 7 hours for mating rights. The female gives birth to 20-30 independent snakelets in late Summer.
  • they are generally slow moving, docile (unless threatened) and diurnal - hunting at night only on warm nights
  • diet is mainly frogs, tadpoles, lizards and carrion, but will also take small mammals, bats, insect, birds, and fish while the larger Chappell Island tiger snakes will also prey on fat muttonbird chickens
  • their main predators are other snakes (adult tiger snakes will often eat juveniles) including the small-eyed snake (Cryptophis nigrescens) (a nocturnal snake found in eastern Australia between northern Cape York Peninsula in Queensland and eastern Victoria) and birds of prey such as harriers, goshawks, butcherbirds, ibises, kookaburras and kites.
  • in cooler weather, they aestivate in animal burrows as deep as 1.2m, under large boulders or dead trees. But they may also be found basking outside on warmer winter days.

Common Eastern Brown snake

  • account for ~40% of all snake bites in Australia due to proximity to urban centres, and account for 75% of all deaths from snake bites in Australia
  • Pseudonaja textilis - a fast (can outpace a human running but will not chase humans) snake with good eyesight
  • the second-most venomous terrestrial snake in the world
  • grows to 1.5m and sometimes to 2m
  • found along the east coast of Australia from Malanda in Qld down to Victoria and across to Yorke Peninsula in Sth Australia. Disjunct populations occur elsewhere such as NT.
  • tends to prefer drier areas such as sclerophyll forests, coastal heaths, farmlands (especially as they prefer to eat rodents), etc
  • has two phases of threat display:
    • partial: raises front of body partly off the ground and flattens neck
    • full: rises up vertically high off the ground, coiling its neck into an S shape, and opening its mouth
  • this means, unlike most other snakes, these snakes can bite the upper thigh when standing, but fortunately most bites do not result in envenomation
  • they are generally fast moving and diurnal - hunting at night only on warm nights
  • walking in undisturbed areas on cool days in September and October risks running into courting male snakes that would not notice people until close as they are preoccupied with mating
  • snakes will generally move away early when they detect humans, and they can detect them better if they are wearing dark clothing and approaching quickly and noisily, and are less able to detect when people are moving slowly, especially on a cloudy, windy day

Red-bellied Black snake

  • Pseudechis porphyriacus “false viper”
  • native to the east coast of Australia as far north as Gladstone in Qld
  • in Victoria it is mainly in the south, east, central parts of Victoria but extends to Sth Australia along the Murray River
  • account for 16% of snake bites in Australia but no deaths
    • tend to be more painful than most other Australian snakebites
  • it is the most commonly reported species responsible for envenomed dogs in NSW
  • not aggressive, less venomous, usually within 100m of a water body, average length 1.25m but can grow to 2.5m
  • adjust their conditions to maintain a temperature of 28-31degC
  • are very good swimmers and can stay underwater for up to 23 minutes to avoid terrestrial predators
  • there are related species in the Atherton Tablelands in Qld (Pseudechis porphyriacus eipperi ) and another in southeastern South Australia (Pseudechis porphyriacus rentoni )

Copperhead snake

  • a shy snake which rarely bite humans unless provoked
  • Common Lowlands Copperhead Australeps superbus
    • length usually reaches 1.75m
    • common in southern Victoria and in Tasmania
  • Alpine or Highlands Copperhead Australeps ramsayi
    • grows to 1.25m and lives near streams in northern Victoria and southern NSW alpine regions
    • often found on alpine hiking paths in the morning sun even if temperatures are 10degC - they are unlikely to move unless provoked!
  • Pygmy Copperhead Australeps labialis
    • confined to Sth Australia

non-venomous pythons

  • mainly found in the Wangaratta and eastern Gippsland regions
  • Carpet Python Morelia spilota metcalfei - mainly nocturnal; northern areas;
  • Diamond Python Morelia spilota spilota - non-venomous; coastal heaths of far east Gippsland

other snakes

  • Little Whip snake Rhinoplocephalus flagellum
  • snakes confined mainly to north-western regions of Victoria (eg. Mallee):
    • Western Brown Snake Pseudonaja nuchalis - fast, aggressive
    • Master's snake Drysdalia mastersii - mainly Mallee
    • Mitchell's Short-tailed snake Rhinoplocephalus nigriceps - mainly Mallee & north-central areas
    • Bardick Echiopsis curta - mallee region
    • Port Lincoln snake Rhinoplocephalus spectabilis
    • Red naped snake Furina diadema - rare; usually assoc. with termite mounds
    • Yellow-faced Whipsnake Demansia psammophis - fast snake; Murray River;
  • snakes confined mainly to northern Victoria:
    • Curl Snake Suta Suta - mainly in the Loddon, Avoca and Murray rivers region
    • Bandy Bandy snake Vermicella annulata - rarely seen snake in northern areas; nocturnal;
    • Blind snakes Ramphotyphlops spp - rarely seen snake in northern areas; non-venomous; nocturnal;
    • Woodland Proximus Blind Snake (Anilios proximus)
      • found in eastern Queensland, New South Wales, northern Victoria (Grampians to Wodonga - north of the Dividing Range) and eastern South Australia
      • mainly nocturnal and non-venomous, it is a burrowing snake which spends most of its life beneath leaf litter or underground.
      • rarely seen in daytime, but would make incidental appearances after heavy rainfall or warm moist nights using rocks and debris for shelter
      • deter predation by emitting an unpleasant odour from anal glands
  • snakes confined mainly to south-eastern Victoria:
    • White-lipped snake Drysdalia coronoides - eastern suburbs Melbourne & southern forests but rarely seen
    • Small-eyed snake Cryptophis nigrescens - warm dry forests of south-eastern Victoria

Tasmanian snakes

  • Tasmania has three types of snakes: tiger snakes, copperheads and white-lipped snakes — all venomous

Queensland snakes

  • unlike Victoria which only has a few common species of snakes there are over 20 common species of snakes in Queensland including many more non-venomous arboreal snakes as well as different venomous snakes such as taipans and death adders (tiger snakes range as far north as Bundaberg near the SE coast but are found in a couple of regions in inland Qld as well, while copperhead snakes prefer cooler areas and only range as far north as the Great Dividing Range near Byron Bay)
  • it is estimated 1 in 3 houses in the Gold Coast in Queensland have a non-venomous python living in the roof cavity!4)
    • pythons in Qld start to get more active as soon as temperatures hit 24degC, but the venomous eastern brown snakes start getting more active a bit later after winter when there is at least 4-5hrs a day above 24degC which causes the ground to warm up following winter
australia/snakes.txt · Last modified: 2024/02/04 23:06 by gary1

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