Poison arrow frog photos - Paul Bertner

Poison arrow frog photos




Background


Bocas Del Toro is an archipelago in north eastern Panama. Due to rising water levels nearly 10,000 years ago,  a vast series of islands and finger-like projections were created independent from the mainland. Each island and fragment served as a kind of experiment in evolution. And although the majority of the flora and fauna is mostly homogenous across the islands, there is a glaring exception. Amazingly, almost every island has given rise to a different colour morph or "isotype" of a single species: the strawberry poison arrow frog (Oophaga pumilio).  There is some lively debate among scientists about the actual number of variants and what constitutes an actual isotype versus population drift. However, most agree that it is between 15-30, with the pet trade running the numbers up into the 50's and 60's to capitalize on slight morphological differences within a population which they can then market as a distinct isotype and thus charge more.

How so many different colour forms has evolved and within such a small area is still largely unknown. Poison arrow frogs gain their toxicity through bioaccumulation. They sequester and store alkaloids which they obtain form their prey. The more vibrant the colours of the isotype, the more toxic the prey on that particular island, or so one theory posits. Regardless of the evolutionary reason, the cornucopia of colours exhibited by this one species is truly one of nature's many marvels.


Technical details


All the portraits taken on this page were taken with a Canon 5D mark III, Canon MPE-65mm and Canon MT-24EX twin flash with DIY diffusers (I will explain how to make these in a future post).

Due to the dark rainforest understory, I  did one of 2 things.  A) Positioned myself below the subject shooting upward. This only worked if the subject was on a hill or ledge from which I could shoot up into sky to include natural light, or else B) Place the subject on a leaf, twig or substrate which I then held up to the brightest point in the sky. Elevating them off the ground had the additional benefit of making them more sedentary, an especially salient point, because poison arrow frogs are normally very fast and rarely sit still for long. 

I would then minimize the flash duration so that 1) it wouldn't overwhelm the natural light, and 2) the specular highlights would be less evident. Flash duration ranged from 1/64-1/8. If shot at the brightest time of the day, the shutter speed could be as high as 1/30sec, but oftentimes it went as low as 0.4". The ISO on the natural light photos never rose above 400, but would go slightly higher when shot against a white background because the noise is less evident in an all-white versus natural light background.

For photos with a white background, I used a clear acrylic sheet held above a white reflector disk and then made sure to shoot at a slight downward angle.This setup it very light, multi purpose, and packs easily. The disadvantage is that it doesn't work for flying subjects, since it is "open air".


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