SPIDERS
Spiders belong to the Arachnid group which also includes scorpions, mites and ticks. There are over 2000 spider species in Australia and, since they are carnivores, most possess a venom strong enough to subdue their prey.
Two are known to have caused human fatalities, the Sydney funnel-web and the redback. Neither of these is naturally found in the wet tropics but redbacks have been turning up here in increasing numbers, presumably having hitched a ride on trailers, furniture, and so on. It is only the females, the ones marked with the warning red spot, which can cause us problems but they are responsible for more cases of serious envenomation in Australia than all snakes and marine stingers put together.
The good news is that redbacks are not aggressive, their venom is slow-acting and an anti-venom is available. They like undisturbed spots such as outbuildings and can be found underneath logs and rafters so it is always wise to be careful where you put your hands. Some people in redback prone areas have their houses sprayed with insecticides but this is not necessarily a smart move because redback predators may also be killed; black house spiders kill redbacks.
Much remains to be discovered about the effects of various spider bites on humans. Many including the common black house spider, can cause severe illness. Wolf spiders and white-tailed spiders have both been blamed for causing ulcers and spreading tissue death leading occasionally to amputation. The latter spider is a small long-bodied black spider with a white tip to its tail, sometimes found wandering around homes at night. Some people suffer little reaction to the bites while for others they become an ordeal. The simple message is, don't handle spiders.
CATERPILLARS
Caterpillars of a number of moth species are covered with spines or hairs containing venom or irritating substances, which cause itchiness and pain when they come into contact with human skin or eyes. Caterpillars of the bag moth (boree moth) are usually associated with acacia trees where they feed and shelter communally, building a tent-like bag of silk. They can also be seen travelling head-to-tail in long processionary trails. Contact with the caterpillars, the hairs which they leave on tree barks, cast-off skins or bags can lead to numerous hairs penetrating the skin. It is unwise to sit or camp under-trees where they are present.
GREEN TREE ANTS
Green tree ants are the animals most likely to trouble visitors and residents in the coastal wet tropics. They are everywhere where there is vegetation and bite with a nasty nip. Knocking into a nest is a particularly unpleasant experience but the effects are not serious or long-lasting.
BEES & WASPS
Usually stings result in local pain and swelling but some people are allergic to the venom, their reaction becoming more severe each time until a stint may be life-threatening. Wasps, defending a nest, can attack viciously, each delivering multiple stings. Wasps remove their stings but when a bee departs it leaves behind the sting and attached venom sac which continues to pump toxins into the victim.
SCORPIONS
Scorpions, when provoked, deliver a sting from the tip of their tails. Australia species, although common, are not nearly as dangerous as those from other parts of the world. Stings are rare and pain usually wears off after a few hours.
MITES
Mites are tiny relatives of spiders. One species occurring in north Queensland is known as the scrub itch mite. Juveniles picked up by people from logs or vegetation become lodged in skin folds and under tight clothing causing an itchy rash. Rarely, these mites (and ticks) also transmit scrub typhus, a serious illness typified by headaches and fever which needs antibiotic treatment.
LEECHES
Leeches are among the most loathed but least harmful of the animals which might take more than a passing interest in humans in the rainforest. Related to earthworms, they feed on blood. A leech's body is covered with receptors attuned to heat, cold, light, odour and vibration so it is very quick to detect a potential meal. Using suckers on each end of its body, the leech loops swiftly in pursuit. Once on the host it seeks out a dark spot and digs in its teeth, releasing an anaesthetic which keeps its presence undetected and an anti-coagulant which stops the blood from clotting. It falls off when it is full and up to five times heavier than it was at the beginning of its meal. It can last for a further year without eating.
It is difficult to outwit leeches when they are around in large numbers in wet rainforests. Covering the socks and shoes with insect repellent, eucalyptus oil or soap lather is said to repel them and some people wear pantyhose on the outside of socks and long pants. Others simply ignore them and just wash oft` the blood at the end of the day. Leeches can be encouraged to drop off when heat, such as a lighted cigarette, or salt are applied. Pulling them off can tear the skin which may then become infected.
One potentially dangerous situation is where a leech is not noticed crossing a face in wet and cold conditions and fastens itself to an eyeball. It does happen! The only safe thing to do is wait for 15-40 minutes until the leech voluntarily detaches itself and drops off. Pulling it or applying salt may damage the eye.
CENTIPEDES
Centipedes up to 15cm long are found in the wet tropics. The two powerful jaws can deliver a painful bite which may cause nausea. Centipedes are fast-moving creatures and shouldn't be handled.
BULLROUTS
Even if you avoid the stingers in the sea and the crocs in the creeks you are not entirely safe in fresh water. In coastal rivers, near rocks and in weedbeds, the bullrout lurks, lying in wait for small fish and crustaceans. A relative of the marine stonefish, it sports very similar venomous spines on its fins. Human victims usually accidentally stand on or brush the fish, the spines even penetrating light footwear and delivering venom deep below the skin. The pain is excruciating but the venom is, happily, quickly destroyed by heat.
Avoid bullrout stings by wearing substantial footwear when wading through shallow weedy water, particularly below dams and weirs where bullrouts accumulate. Shuffling may encourage the fish to move away.
CASSOWARIES & PIGS
Cassowaries and pigs are the only potentially dangerous large animals to be encountered in wet tropic forests. Although cassowaries will usually move away they are unpredictable and it is not unknown for them to attack people, kicking forward with strong feet and dagger-like middle toes. Sometimes birds which are accustomed to being fed by people appear aggressive when they approach, expecting handouts. Cassowaries, like all wild animals, should not be fed. If a cassowary does approach aggressively back away, keeping it in sight, and try to get something solid between you and the bird. Be prepared to hold a bag defensively in front of your body but not above your head as this would leave your torso vulnerable.
Most pigs will run away from you but if one approaches just step aside, behind a tree, and it will probably keep going.
MONITOR LIZARDS
Monitor lizards have strong claws and jaws and, if accustomed to being fed, boldly approach camp and picnic areas. When scared they climb trees (do not get in their way) and may bite if provoked. Since they feed on carrion, bacteria in their mouths may cause infection.
PLANTS
Stinging Tree
One of the
worst things a visitor to the rainforest can encounter is
the stinging tree which frequently grows in clearings and
along tracks. The leaves bristle with hollow hairs of
silica which, when brushed, snap off and inject a
powerful and irritating toxin. The composition of this is
not fully understood but it causes intense pain which can
last for months, recurring whenever the area becomes wet
or cold. Dead stinging trees are also hazardous - when
disturbed they release a cloud of stinging hairs which
can cause severe problems if inhaled. It is a good idea
to learn to recognise and avoid stinging trees. Avoid
rubbing the area if you get stung.
Burny Bean Vine
Many other
plants also protect themselves with stinging hairs. The
burny bean vine (Mucuna gigantea) produces seed
pods up to 14cm long covered with golden hairs which
cause a burning sensation in enquiring fingers for about
half an hour.
Tar Tree
The tar tree (Semecarpus
australiensis) gets its name from the black resin
which drips from it and which can cause permanent
blindness if rubbed in the eyes. The cashew-like fruit of
the tar tree causes painful ulcers of the mouth if eaten
but is only one of many toxic rainforest fruits. Don't
sample unless very sure of what you are putting in your
mouth.
TICKS
One of the first questions commonly asked by visitors to the wet tropics is about dangerous snakes. However, one of the most dangerous animals in the wet tropics - the cause of at least 20 deaths in Australia in the first half of this century - is one of which few people are aware and which is so small its approach is almost never noticed. It is the paralysis tick, also known as the scrub tick.
Ticks are essentially large mites which need to feed on blood and are attracted to their hosts by movement and by the carbon dioxide exhaled by mammals. Dropping on to their victims from grass or leaves, they quickly find a dark moist spot such as the upper thighs, armpits, behind ears or on the scalp where they attach themselves and begin to feed. A female needs three feeds of blood during its life but it is usually the third feed of the large adult female which causes trouble. (The adult male does not feed at all.) From time to time, as the tick feeds, it injects unwanted fluid from the blood back into the host's body, along with its own saliva. This saliva contains a powerful toxin and the output increases as the tick’s body enlarges.
Small children begin to show the effects of the toxin after about three days when their walking tends to become unsteady. This muscle paralysis spreads to their arms and then, if no help is given, to their chest muscles, at which stage they may die from respiratory failure. The devastating effect of its saliva on some hosts is of no obvious use to the tick and seems to be purely a quirk of nature. Its normal native host, the bandicoot, is immune.
It is important to be aware of the potential impact of scrub ticks, especially on children (and pets) and particularly during the peak season, from June to December. After bushwalking all members of the group should be checked for the following six days for signs of ticks - usually a minor irritation and lump. Grasp the tick as near to the person's skin as possible and pull it off`, taking care not to squeeze the body which might then inject more saliva. If the mouthparts remain they can be picked out with a sharp blade, but there is no need to cut the skin.
Reaction to the toxin wears off slowly (even increasing for a while following removal). Happily, due to awareness of the problem and the availability of an antitoxin, deaths from ticks are now very rare. An adult tick is at first oval, flat, yellowish and the size of a match head. As it feeds it darkens and swells to the size of a pea.