The strawberry poison dart frog (Oophaga pumilio) (Photo One)
Dear Readers, as the frogs return to my pond I found myself curious about frogs in general, so off I went to New Scientist. First up, here is the strawberry poison dart frog. In the archipelago of Bocos del Toro, Panama, the frogs vary greatly in colour according to which island they live on, although they are all the same species. Wildlife photographer Paul Bertner headed off to the islands, accompanied by his Panamanian guide who had won one of the islands on a gameshow. It isn’t clear why the frogs on the different islands look so different – presumably the colours give them an advantage in each habitat, so my guess would be that there are slight variations in plant cover and predators. Sadly, some of the colour variants are already becoming rare, because there’s a market for them amongst exotic amphibian collectors. Leave the frogs alone, people! Amphibians and other exotic animals are extremely difficult to rear and breed in captivity, and I dread to think how many die because their conditions aren’t correct. I speak, sadly, from experience, having tried to keep reptiles and amphibians in my twenties. I soon realised that this is a very tricky area which requires specialised knowledge.
Still, here are some of the photos that Bertner captured of the wild frogs, and very pretty they are too. You would never guess from looking at them that they were the same species.
Strawberry Poison Dart Frog (Photo by Paul Bertner)
Strawberry poison dart frog (Photo by Paul Bertner)
You can see all the photos and read the article by Alice Klein here.
From rainbow frogs to fluorescent ones. Scientist Julián Faivovich has found that the polka-dot tree frog of the Amazon basin is the first one that glows in the dark. making it 30% brighter at twilight than other frogs. It’s known that many microorganisms fluoresce, and so do some fish and sea turtles – in other words, they have substances in their skin that absorb light at one wavelength, and emit it at a longer one. Faivovich believes that although this species is the first amphibian which has been proven to fluoresce, it’s unlikely to be the only one – there are 5000 species of frog, so for this to have evolved just once is very unlikely.
The fluorescence happens at a wavelength that the frog can see, and so it’s probably useful for signalling and for communication although, as with so much about frogs, it’s still a mystery.
You can read the whole article by Sam Wong here.
Polka-dot tree frog (Hypsiboas punctatus) in daylight….(Photo Two)
…and when seen under ultraviolet light (Photo Three)
In other good news, a new species of frog discovered in a protected forest in India in 2019 is the only living member of a lineage that dates back millions of years. The starry dwarf frog (Astrobatrachus kurichiyana) is only two centimetres long with an orange stomach. Interestingly, the number of frog species identified in India has leapt from 200 to 400 species over the past few decades, which just goes to show what you can find when you look. You can read the whole article by Adam Vaughan here.
Starry Dwarf Frog (Photo by Seenapuram Palaniswamy Vijayakumar)
And finally, you may be aware that frog species all over the world are being decimated by chytrid disease, a fungal disease of amphibians. Frogs are widely seen as the ‘canaries in the coalmine’ by ecologists, due to their acute sensitivity to changes in their habitat. Many zoos and institutions have been in a race against time, taking whole frog populations into captivity to preserve them and breed them, with the hope that they will be able to be reintroduced into the wild when a cure for the fungal disease is found, and when their habitats are secure. So it was great to see that some populations of frogs do seem to be developing immunity to chytrid, provided that there are enough of them and their habitat is not too degraded.
The Sierra Nevada yellow-legged frog (Rana sierrae) lives in the mountainous regions of California, but its population has been in decline for years. This is partly due to the stocking of the rivers where it lives with non-native trout, who eat the frog’s tadpoles, but the frog really started to decline when chytrid hit in the 1970’s. By 2000 the frog had disappeared from 93% of its habitat, and was classified as endangered. However, the good news is that the frog appears to be bouncing back, with an annual population growth of 11%. Scientist Roland Knapp puts this down partly to the Park Service’s good sense, as they stopped stocking the river with trout in 1991. However, the frogs that have survived chytrid now appear to have some resistance to the fungus, allowing the population to recover. This has also been observed in the Stony Creek frog in Australia, which also appears to have developed resistance.
However, scientists are cautious – in areas with tiny, isolated populations, or where there is already significant habitat degradation, it will be a lot harder for the frogs to survive long enough to develop resistance. It seems that those dedicated frog conservationists battling to save these animals will be busy for quite a while yet.
You can read the whole article by Brian Owens here.
Sierra Nevada Yellow-Legged frog (Photo by Joel Sartore, National Geographic Photo Ark/Getty)
Photo One by By Marshal Hedin from San Diego – Oophaga pumilio (Strawberry poision frog)Uploaded by Jacopo Werther, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=24872534
Photo Two By Erfil – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20721069
Photo Three by By Casa Rosada (Argentina Presidency of the Nation), CC BY 2.5 ar, https://commons.wikimedia.org/w/index.php?curid=69469705