Stinging Tree Can Kill Marina Hurley Dogs and Horses, And
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Marina Hurley The stinging tree can kill dogs and horses, and Marina Hurley has even led to the death of humans, but countless native animals live content among its Left: The rainforest gap at Wongabel State Forest where Marina Hurley poison hairs. conducted her study. Above:A leaf from the most painful of Marina Hurley spent stinging trees, the Gympie Gympie, showing characteristic damage caused by many nights among a voracious noctural beetle. these dangerous plants to discover why. Selective stingers Marina Hurley received her PhD at James ustralia is home to the world’s the southern giant stinging tree leaves always seemed to be full of holes. One evening, when spotlighting for also eating the stinging-tree leaves. This Cook University in 1997 for research into most painful plant to touch: the (Dendrocnide excelsa) and the northern Something was eating them. I wanted to possums, I found the answer. Scattered all was a surprising discovery, as I had no stinging trees and their herbivores. She now ‘stinging tree’. Even gently shiny-leaf stinging tree (D. photinophylla). find out what it was and whether they over the leaves were shiny green-black knowledge, and there were no repots of, teaches entomology and ecology at the A brushing the leaves of this tree can cause The rest are shrubs, including the most were deterred by the stinging hairs. beetles (Prasyptera mastersi). These any mammal having eaten D. moroides. University of Tasmania and,with the CRC intense pain, an itching, burning sensation painful plant of the genus, the Gympie- nocturnal beetles ate between the stinging I started leaving leaf baits on the forest for Sustainable Production Forestry, which in mild cases can linger for months, Gympie (D. moroides). This is found in Not so hapless herbivores hairs, but quite effortlessly walked among floor, weighted down with rocks. Every investigates plantation Eucalyptus nitens and and in extreme cases can be agonising, North Queensland rainforests along with them. Another common insect herbivore day the leaves (as large as dinner plates) their beetle herbivores I began my research in a clearing at even fatal. another closely related, but slightly less Wongabel State Forest on Queensland’s was a small moth (Prorodes mimica) which were dragged away from the rocks and harmful species, D. cordifolia. made protective shelters in the leaves. eaten – hardly the kind of feat you’d Stinging trees belong to the same plant Atherton Tablelands. There I found that family as European stinging nettle. They I chose to study these two species of From then on I worked in the rainforest expect from an insect. far more animals can eat stinging leaves are found on Australia’s eastern coast, stinging tree because they fascinated me during the evening, looking at the beetles, Possums were known to eat the less and fruits than are affected by the sting. from Iron Range on Queensland’s Cape and no one had looked closely at them watching them feed, and comparing their noxious giant and shiny-leaf stinging trees, The stinging trees of Wongabel were York Peninsula to wet temperate before. The botanist who described the density with leaf damage I had measured but they didn’t appear to eat the noxious crawling with creatures: spiders, scarab rainforests of the south-east. They grow in genus in the late 1960s had mostly relied during the day. D. moroides. Through a process of rainforest clearings, moist woodland on preserved specimens, resulting in some beetles, green ants, mites, katydids, On one occasion, a two-metre stinging elimination I found the culprit was the red- gullies, along small tracks and creek edges, taxonomic inconsistencies. sapsuckers, leafhoppers, assassin bugs, a tree with large round leaves was stripped legged pademelon, Thylogale stigmatica: a and on properties that border rainforest. The role of the stinging hairs was also few snails and the occasional frog and overnight. All that was left was chewed shy, fleet-footed rainforest wallaby that can Of the six ‘stinging tree’ species known puzzling. Although the shrubs appeared lizard. It took me weeks to determine remains and scratch marks on the stems. smell you coming ‘a mile away’, especially in Australia, only two are actually trees: to have the ultimate defence system, the which did the most damage. Something much larger than insects was if you’re carrying a camera! 18 Ecos 105 October–December 2000 Ecos 105 October–December 2000 19 The red-legged pademelon’s taste for An unfortunate stinging-tree leaves is well-founded. My research has shown that stinging tree Marina Hurley grasp of the leaves are actually nutritious, containing high concentrations of nitrogen and even nettle calcium (nettle tea was a common beverage prepared throughout Europe for ‘WORKING in the rainforest at night similar reasons). was easy enough, unless it rained Stinging trees are not protected from heavily. I always wore a miners torch being eaten by insects or mammals. In fact and took a spare in my pocket. they seem better suited to the rapid The nocturnal stinging tree beetle is happy There was one night, however, when colonisation of rainforest gaps than to among the tree’s poison hairs. both torches failed and it was lucky that avoiding herbivore damage. Unless small the moon was out. I managed to seedlings are wiped out by a pademelon or Because our bodies cannot break down falling branch, stinging trees are able to negotiate dozens of stinging tree leaves silicon, the stinging sensation can be felt put up with heavy leaf damage, by being by moonlight, to find my way back to up to a year. The hair containing the toxin able to quickly regrow large leaves. the track and then back to my car. is embedded in the skin and any The leaves of D. moroides can readily Painful analysis movement of the affected area caused by sting your skin through the toughest of touch or exposure to hot or cold Stinging trees deliver their sting by means clothing. Welding gloves were all I temperatures will release the toxin and the of a toxin contained in tiny silicon hairs could find to wear to handle the leaves stinging sensation will recur. that cover all parts of the plant, except the and collect insects without getting The nature of the toxin is not fully roots. These are easily broken off on stung. I learnt very quickly to develop a understood, but acts like a neuro-toxin contact, penetrating the skin and acting sixth sense when moving around the and is so stable that it retains its pain like miniature hypodermic needles. plants, always moving slowly and producing properties for decades. Dried Depending upon the species and the remaining alert at all times. botanical specimens at a CSIRO degree of contact, the reaction can vary herbarium in Brisbane, collected in 1910, But I wasn’t prepared for my worst from mild irritation to death, not only in can still cause pain. sting that left me in hospital for half a humans, but also in dogs and even horses. The only human death officially day. I dropped my glove on the ground The burning pain is felt almost attributed to the tree was recorded in New and as I picked it up I drove my finger immediately after contact, then intensifies, Guinea by Dutch botanist HJ Winkler in right through a dead leaf that was reaching a peak after 20–30 minutes. the early 1920s. He also observed that the curled up on the forest floor. Another During this time the heart rate increases dried bark of another species D. cordata, is close call was forcing myself not to and the lymph glands in the joints begin to fatal when eaten. instinctively jump backwards, and into swell and throb, causing almost as much I once received a letter from an ex- a patch of stinging trees, when finding pain as the sting. The hairs are so tiny that serviceman Cyril Bromley who was a snake basking in the sun at my feet.’ the skin will often close over them, making severely stung while crossing Rocky Creek them difficult or impossible to remove. Marina Hurley near the Barron River in North Queens- land in 1941. During military training, he was swinging on lawyer cane over a creek when it broke and he fell into a stinging tree. He was literally tied to his hospital bed for three weeks because the pain was so bad. He also told me of an officer who had shot himself because he could not stand the pain. In addition to the pain, I found that the RN Parsons, Through the Looking Glass Photography stinging hairs are also shed continuously and cause an allergic reaction to anyone who remains close to these plants for more than one hour. The reaction involves intense, harsh, continuous bouts of sneezing from breathing in the air-borne stinging hairs. This phenomenon was prevented by wearing particle masks, The hair of the less noxious northern provided they were replaced regularly. shiny-leaf stinging tree. Extended contact without protection will eventually result in nose bleeds. 20 Ecos 105 October–December 2000 A newly-emerged Gympie Gympie leaf, showing its dense, stinging hairs. Below: Stinging trees are inhabited by a variety on rainforest animals.These green ants are making a nest in the northern shiny-leaf stinging tree. Ecos 105 October–December 2000 21 Why do these plants cause so much pain? that mammals have simply learned to deal to gain a foothold and race up into the It is likely that insects are small enough to with the pain over time.