Poison frogs of the Osa peninsula

I returned to the beautiful Central American wildlife paradise which is Costa Rica in April this year. It was always going to be a bit hit and miss in terms of finding amphibians, being the end of the dry season and this turned out to be the case. After several attempts at the beginning of the trip to find an urban population of Agalychnis annae, I became concerned that the extreme drought of recent months would make the trip a disaster. Needless to say no Blue-sided tree frogs could be found, not surprising as all of the vegetation surrounding their breeding ponds was dying off.

DSCN0358Fortunately things would improve as we boarded our small plane to Puerto Jiménez in the Osa Peninsula. We spent 6 days and nights at the beautiful La Tarde finca on the edges of the Corcovado National Park and the moved onto La Bahía de Drake area afterwards. Thanks to Eduardo, the owner of the finca we could find some beautiful amphibians despite the drought. A few brief spells of rain in the late afternoon on 2 days really made all the difference for finding some species. This is one of the few places in Osa where all of the areas poison dart frogs can be found together. The granulated poison frog (Oophaga granulifera) was the first species we encountered, not by day but sleeping by night. On the previously mentioned rainy afternoons we soon found more out calling and hunting by day and then several more sleeping on leaves at night. A species I expected to be common here was in fact the trickiest to find, I’m pleased to say I found them all by myself in the end! The Green and black poison frog (Dendrobates auratus) is a common species in many parts of Costa Rica but not in the Osa peninsula. After many hours of hiking trails by day I eventually found three adult individuals. Their patterns here differ somewhat to those further north. Whilst searching for the green and blacks we came across a nice water fall with a stream below it. Here we found a dense population of Lowland rocket poison frog (Silverstoneia flotator). These are tiny frogs and seem to spend a lot of their time sitting on damp rocks by the stream edge.

In terms of poison frogs, we saved the best until last. After a long hike back to the finca I bumped into Eduardo and I asked him about the Golfo Dulce poison frog (Phyllobates vittatus). He said they were tricky but he told me of a nice “riachuelo” where they can be found in good numbers and that he would take me there! Within minutes we started hiking again, after a nice rain shower into a very dense area of rainforest with no trails. We hacked through vegetation to reach the stream and straight away we heard the calls not only of granulifera but also the much desired vittatus! “Matt, aquí hay una!” We found one straight away soon followed by 6 more adult individuals. These are bigger frogs than I expected and turned out to be one of the highlights of the trip! Thanks Eduardo! Later on at Drake Bay I visited another place where I was lucky to find 2 more of these frogs under leaf litter at night. Despite the drought we found lots of other amphibians which I will share in a later post.


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