02 February 2016

In February last year, members of Chester Zoo staff embarked on an expedition to our project in Assam. Whilst out in Assam, the 12 members of Chester Zoo staff provided technical support to villages that had previously been victims of human-elephant conflict.

This year’s expedition was a trip to Madagascar to provide support to our colleagues at Madagasikara Voakajy (MaVoa). We have been working with MaVoa for a number of years and the focus of this expedition was monitoring the critically endangered golden mantella frog population – an ongoing project.

Capture-mark-recapture

Microchips are often used to monitor populations through the use of a technique called capture-mark-recapture. If you’re checking populations over a long period of time (months or years), the microchip tells us that an individual has been captured before and when it was last captured.

If all animals captured have been microchipped, you can be reasonably confident that the majority of the population has been marked. By counting the number of individuals captured and already microchipped, population size estimations can be calculated.

Unfortunately, using microchips for a capture-mark-recapture population estimation isn’t really possible for many amphibian species, like the golden mantella frog, because of their size. The golden mantella frog only reaches a length of 20 – 26mm and a microchip measures around 12mm – half the body size of the frog!

Instead, a clever technique for marking the tiny frogs has been developed: elastomer marking. This technique uses two parts of silicone to give the golden mantella small coloured implants under their skin that are visible, almost like a small tattoo. The silicone used comes in several different colours and the colours used can be translated into a coding system. Pretty clever isn’t it?

Silicone used to mark the golden mantella frogs

Different colours of silicone are used to mark the golden mantella frogs

The technique was firstly tested on the golden mantella that we have at the zoo so that any effects of the implants on the frogs could be monitored closely. Once our amphibian experts at the zoo were satisfied that there were no secondary effects to the frogs, Gerardo Garcia – Chester Zoo’s curator of invertebrates and lower invertebrates – travelled out to Mangabe in Madagascar to start using the technique on wild populations.

Since 2014 we have monitored the golden mantella population using this technique. We do this three times a year and has been an extremely useful technique for our partners MaVoa who have also been trained by our zoo staff on the marking technique.

Gerardo Garcia and Philippa Carter Jones showing colleagues in Madagascar how to mark frogs

The expedition’s main focus was to assist with population surveys of the golden mantella, using the elastomer marking technique. So it was important that the team had the necessary skills in frog handling.

Leading the training workshop was Gerardo Garcia and Philippa Carter Jones (Pip), Chester Zoo amphibian keeper, who have had enough training to use the elastomer marking out in the field. Our two amphibian experts taught the rest of the team everything they needed to know to understand the process thoroughly.

These are just some of the preparations the team did ready for the Madagascar expedition to ensure that they could maximise on the support they were able to give our colleagues at MaVoa.

Keep an eye on our blog for more updates from the expedition or sign up to our Act for Wildlife monthly e-newsletter and receive news straight to your inbox.