The Ark Files - Toxic shock

Teeth, claws, hoofs and horns are not the only weapons animals use. Chemical warfare in the form of poison is also used very effectively. Snakes and spiders are the best known producers, but most amphibians are also toxic and there are three types of venomous mammals and even a species of poisonous bird.

Cute and cuddly?

The platypus as a mammal is strange enough – it has fur and it also lays eggs. But in addition to these somewhat confusing features, it is also distinguished by another feature shared by very few mammals – it is venomous! The male platypus has a horny spur about one centimetre long on its hind leg. The spur resembles a snake's fang as it is hollow and injects a highly toxic substance from glands located in the thigh. The venom is said to be very similar to that produced by the Australian Tiger Snake. The toxin from a platypus jab can cause excruciating pain in humans and kill smaller animals such as dogs. Platypuses mainly use this weapon when fighting other males for a mate or in defence of their territory.

Another venomous mammal is the solenodon, a large shrew-like mammal that weighs about one kilogram and lives in the dense, humid forests of Cuba and Haiti. The solenodon is endangered, nocturnal and rarely seen, spending most of its time foraging on the ground with its sensitive snout and tearing into rotten logs and trees with its claws for insects and spiders. Its saliva is poisonous and a quick bite will subdue any prey.

Some short-tailed water shrews which live in the swamps of eastern North America also have toxic bites. Called Spiny Hell-rats, they are more weasel-like than shrew-like and armed with particularly sharp claws as well as poisonous saliva. They will even occasionally take on snakes.

Small but deadly

Frogs have glands that produce slimy mucous to keep their skins moist, and in many species these slime glands also produce poison. The little poison-arrow frogs of the South American rainforests top the list when it comes to producing the most toxic amphibious poison, and one called Phyllobates terribilis is one of the most poisonous vertebrate animals in the world. One thousandth of a gram of the poison from these frogs is enough to kill a human. Although tiny, poison-arrow frogs are fearless and climb about the leaf litter during the daytime, relying on their vivid colours to warn of the lethal prospect of eating them. Unfortunately they have one successful predator, the South American Indians who catch them and, in a rather gruesome process, scorch them over a fire till the poison leaks from their skins. The Indians then collect and use it to smear on their arrow tips and blow-pipe darts. The amount extracted from a 2.5 centimetre frog is enough to poison fifty arrow heads.

Harpoon hunters

The beautiful cone shells of the tropics are remarkable carnivores that use very specialised teeth to stab and poison. The single tooth is long, grooved, barbed at the tip and connected to a poison gland. Cone shells that feed on marine worms and snails thrust the tooth into their prey like a dart. But in those that feed on fish, the cone lies buried in the sand and does not strike until the fish pauses near the ocean floor. The cone shell then harpoons the soft underbelly of its victim, retaining a hold by a slender cord of tissue. The fish is very quickly paralysed by the venom injected into the wound, reeled in and then swallowed whole. The bite or sting of certain South Pacific cone shells is highly toxic to humans, and has caused a number of deaths, one in only four hours.

Trash birds

Research biologists were stunned by the recent discovery of chemical defences in two species of New Guinea song birds known as pitohui. Apparently the natives of New Guinea have long known of the poisonous nature of these birds, and referred to them as trash birds because they were unable to use them for food.

The unusual toxins are found in the skin, flesh and feathers, and predators have been seen to first pluck the birds before eating parts of them. An unsuspecting researcher recalls his first experience of these birds when he extracted a trapped pitohui from a net. The bird immediately scratched him, causing a painful burning sensation to his hand. His second lesson was not to put his fingers in his mouth after handling the birds as the effect was similar to tasting red hot chilli peppers or touching a live nine-volt battery.

The poisons found in the pitohui were previously only known in poison-arrow frogs.