The Schlegel's Whistler (bird with the scientific name Pachycephala schlegelii) was discovered to science in 1871 while the Rufous-naped Whistler (Aleadryas rufinucha) was discovered in 1874. Both species are endemic to New Guinea and until now few data were known about them due to They live in areas that are very difficult for humans to access.
An expedition led by researchers from the University of Copenhagen (Denmark) that has entered jungles and little-explored subtropical forests of this large island located in the north of Australia has made it possible to discover that the Schelegel's whistler and the Rufous-naped whistler are poisonous birds; What's more, their feathers and their skin contain an extremely potent neurotoxin.
"We managed to identify two new species of venomous birds on our most recent trip. These birds contain a neurotoxin that they can tolerate and store in their feathers," says Knud Jønsson, a researcher at the Natural History Museum of Denmark and co-author of the discovery.
Knud Jønsson and Kasun Bodawattau, a researcher at the University of Copenhagen, have led a study exploration of the biodiversity of the New Guinea rainforest. They captured specimens of the two birds and verified that they have developed the ability to consume toxic food and turn it into their own poison.
"We were very surprised to find these birds to be poisonous, as no new species of poisonous bird has been discovered in more than two decades. In particular, as these two bird species are very common in this part of the world," says Knud Jønsson. .
Most people are familiar with the iconic South and Central American poison dart frogs, especially the golden poison dart frog. These brightly colored little amphibians can kill a human on the slightest touch.
The discovery of two new species of poisonous birds in New Guinea, which carry the same type of toxin on their skin and feathers, shows that frog toxin is more widespread than previously thought.
The poison in the body and plumage of these birds is called batrachotoxin. It is an "incredibly potent" neurotoxin that, in higher concentrations, such as those found in the skin of golden poison dart frogs, causes muscle cramps and cardiac arrest almost immediately after contact, the authors recall in a scientific summary article from their discovery published in the journal Molecular Ecology.
"The toxin from birds is of the same type as that found in frogs, which is a neurotoxin that, by forcing sodium channels in skeletal muscle tissue to remain open, can cause violent convulsions and ultimately instance, death," explains Kasun Bodawatta, study coatur.
South American poison dart frogs use their toxin to protect themselves from predators. Although the level of toxicity to New Guinea birds is less lethal, it may still serve a defensive purpose, but the adaptive significance to birds is still uncertain.
"Knud thought I was sad and having a hard time on the trip when they found me with a runny nose and tears in my eyes. In fact, I was sitting there taking feather samples from a pitohui, one of the most poisonous birds in the world. world". Getting birds out of the net isn't bad, but when samples have to be taken in a confined environment, you can feel something in your eyes and nose. It's a bit like cutting onions, but with a nerve agent, I guess. says Kasun Bodawatta.
"Locals don't like spicy food and stay away from these birds because, according to them, their meat burns in the mouth like chili peppers. In fact, that's how researchers first became aware of their presence. "And the toxin can be felt when holding on to one of them. It feels a bit unpleasant, and holding on to one for long is not an attractive option. This could indicate that the poison serves to deter those who would want to eat them to some extent. spot ". Jønsson explains.
The authors of the study are convinced that the toxicity of these birds gives them an evolutionary advantage, defense against predators, which occurs in various parts of the food chain. It starts at the bottom of the chain with beetles, insects, and other invertebrates. Over time, some of these develop toxicity to avoid being eaten. Perhaps they also acquire a particular coloration that can serve as a warning to us. This, in turn, allows them to venture out from hiding under logs and rocks.
"Then a predator strikes back, and suddenly a species of bird can eat them harmlessly. The predator also acquires, as a species, a mutation that offers resistance to the toxin. This gives the bird an advantage and opens a completely new food source that is not available to their ecosystem competitors. So clearly there is an arms race going on and the beetles will have to crawl back under that rock until they have developed their next move a few million years later," Jønsson explains. .
"Subsequently, birds that have developed the ability to eat toxic food become toxic and can fend off predators further up the food chain. And so the race continues up the chain. It's evolution: anything can happen, but many times it takes a long time," says the researcher.
What makes it possible for these birds to have a toxin in their bodies without getting hurt? The researchers studied this by taking inspiration from poison dart frogs, whose genetic mutations prevent the toxin from keeping their sodium channels open and thus preventing cramps.
"So it was natural to investigate whether the birds had mutations in the same genes. Interestingly, the answer is yes and no. Birds have mutations in the area that regulates sodium channels, which we hope gives them this ability to tolerate the toxin , but not in exactly the same places as the frogs," says Kasun Bodawatta.
The study indicates that while their neurotoxin is similar to that of South American poison dart frogs, the birds developed their resistance and ability to transport it in their bodies independently of the frogs. This is an example of what biologists call convergent evolution.
