Australia is home to six species of 'stinging tree'. The most painful is the shrub gympie-gympie, Dendrocnide moroides. Many native mammals and birds are not deterred by the stinging hairs, while humans, dogs and horses are adversely affected. Stinging tree leaves are eaten by several herbivores. The leaves deliver their sting by a toxin contained in tiny silicon hairs covering parts of the plant, except the roots. The toxin acts like a neuro-toxin and retains its pain producing properties for decades.