by Whit Gibbons

April 26, 2015

The arsenals used by plants and animals throughout the world in waging chemical warfare are fascinating. Finding commonalities and dissimilarities between various groups reveals how diverse the natural world can be. The primary function of injection by many venomous animals is to acquire their prey, although toxic chemicals are also used defensively.

Examples of venomous injection methods include the nematocysts of a jellyfish, the tail stinger of a stingray, and the stinging hairs of some caterpillars. Even some plants, such as the common stinging nettle, are technically venomous as tiny hairs on the leaves and stem can penetrate the skin and release histamines when someone brushes against them. My grandchildren are no longer a threat to stinging nettles because all have learned firsthand the perils of tramping through a patch of this well-armed plant.

A few of the world's mammals qualify as venomous, the best known being the male duckbill platypus of Australia. A sharp spur on each hind foot is connected to a venom gland and a duct that transfers the toxin to the barbed structure. The short-tailed shrews of the eastern United States have toxic saliva that enters the body of prey, or would-be predators, when the shrew bites it.

Poisonous organisms differ from venomous ones in that the noxious chemical is not injected but can be injurious if eaten or touched or even inhaled (e.g., smoke from burning poison ivy). Some toxins can enter the bloodstream through a cut or the lining of mucus membranes. Poison ivy produces an oily substance that causes dermatitis in some people upon contact with leaves, stems, or roots. Death angel mushrooms and poison hemlock produce chemicals that are harmful if eaten. Common garden toads secrete distasteful toxins from skin glands.

No venomous birds have yet been discovered and presumably none exist. But the pitohui birds in New Guinea have poisonous skin and feathers. The chemical composition of the poison is similar to that in the skin of dart poison frogs of Colombia, South America. These deadly little frogs secrete a toxic chemical, a type of alkaloid that makes them unpalatable to other animals. If eaten or injected, as with the tip of a man-made dart used by Colombian natives to hunt prey, the toxic material has an immediate effect on the nervous system.

The particular toxin of the New Guinea pitohui birds was unknown anywhere else in the animal kingdom except in the poison frogs. The chemical is a powerful deterrent, and predators avoid poison frogs as a source of prey. Presumably the poison operates in a similar fashion for the New Guinea pitohui birds by discouraging typical predators such as snakes, other birds and mammals from having an otherwise tasty meal.

The most toxic of the New Guinea birds is the hooded pitohui, a small, orange and black, foul-smelling creature with a crest like a tufted titmouse. While collecting and preparing the first specimens of hooded pitohui birds, the investigators suffered from bouts of sneezing, along with numbness and burning of the mouth and nasal lining. As is often the case with scientific discoveries, the local populace already knew about the phenomenon. A 1977 book on folklore of the Central Highlands Province in Papua, New Guinea, mentions that local residents said the skin of the hooded pitohui "is bitter and puckers the mouth." They referred to it as a "rubbish bird" and advised that it not be eaten "unless it was skinned and specially prepared." I have not sought out the recipe.

Any increase in our knowledge of the natural world is of value if it raises our intellectual consciousness. Such discoveries help us to better understand the differences and similarities of various organisms as well as to appreciate the many ways nature has of solving problems. Knowing that natural poisons (including injected venoms) are an everyday part of nature makes it all the more interesting.

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