【明報專訊】They could be the most brightly-coloured animals on earth, and one of the most poisonous! Poison dart frogs (毒箭蛙) don't hide their incredible toxic weapon–they actually wear it on skin and give it brilliant, neon-like colours of red, blue, yellow, orange and gold! This is the warning from the tiny poison dart frogs, "Hey, look at my colours! I'm extremely dangerous! Don't eat me!" (photo.1)

Talented chemists

The Choco people of western Colombia in South America have a tradition of dipping their arrows in the poison collected from golden poison dart frogs for hunting. This practice has given the frogs their common name ''poison dart frog''.

Measuring only 2.5 to 5cm long, the poison dart frogs in the tropical rainforests of Central and South America may be pocket-sized, but more than 100 species of them carry poison on their skin which can paralyse and even kill predators. The most dangerous of them all is the golden poison dart frog, whose poison is deadly enough to kill 10 grown-up men!

Poison dart frogs feed on insects, such as beetles and ants. Scientists believe that the frogs make poison out of their diet: the insects eat plants that contain toxins which are transferred to the frogs when they eat the insects, processing the deadly chemicals to produce poisons covering their skin.

Dedicated parents

Poison dart frogs often stay in pairs and groups. They are also extremely attentive parents. Once the eggs are laid, both parents help make sure that they are moist and well-guarded. After the tadpoles (蝌蚪) have hatched, the parents carry them on their backs, which are covered with sticky skin that allows the tadpoles to cling (抓緊) safely onto them. The tadpoles are in this way piggybacked and transported to water sources such as ponds.

Every few days for the next two or three months, the parents return to the pond until the tadpoles go through a metamorphosis (變態) – a change so great that a tadpole becomes a completely different creature in body, diet and lifestyle. For example, it will lose its gills (腮) for breathing underwater and tail which it uses to swim. It will develop lungs and legs to live on land. And soon, it will acquire its individual colour and patterns on its skin, something so unique that it is almost like the fingerprints of humans. (photo.2)

When poison fails to protect

Like all animals, poison dart frogs are not free of predators. There is one snake, called the fire-bellied snake, which is immune (免疫的) to their poison and may be their one and only natural predator.

Many species of poison dart frogs have become endangered and threatened. These tiny animals are very sensitive to small changes in their environment and their sharp decline in numbers is a result of habitat loss and climate change. To ensure a more sustainable future for our planet, we must save forest resources, such as paper and wood. (photo.3)

Text and photos：Ocean Park Hong Kong

■Glossary

dip (v) 點、浸

paralyse (v) 使……麻痺

attentive (adj) 關心的

acquire (v) 獲得

[Smarties' Power English 第249期]