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martes, 16 de julio de 2013

Where are the bats?

When Joe arrived back from his whistle-stop European trip he brought back an exciting present for Annie with him – telemetry equipment, 10 micro GPS units and 10 micro VHF transmitters. The master plan – to attach them to bats that she was trapping to gain information about their movements. As my love of field work was spawned in Namibia using VHF telemetry, I was more excited than a child on Christmas day by the brand new receiver and TINY transmitters!! After practicing a little to get used to the equipment everyone was given a run down on how to use the receiver and listen for that hideously illusive BEEP! Everyone took turns in using the equipment to track down a transmitter that I had hidden around the station. Unfortunately, the weather decided that it was not going to be our friend and assist us in this project. The rain and the cold started. And it didn’t stop for around 13 days. This left Annie with a race against time to trap bats weighing more than 90g. Guidelines state that you cannot attach tracking equipment to an animal that weighs more than 5% of its body weight. Even though the transmitters were TINY, Annie still had to make sure that she only put them on the largest bats she was catching. In the few days following the rain the bats started to come back to the nets, but none big enough. Then finally as panic started to set in Annie and Joe finally managed to catch a large female bat and attach a transmitter!! Then the hunt began. With Annie desperately needing sleep, Charlotte (a primate volunteer from the UK) and I took the telemetry equipment and set out on the first hunt. As VHF tracking operates using radio waves one technique to avoid interference is to get up high. To do this, I spent a lot time scrambling onto the roof of the car while all ears strained to hear the tiny bleep through the loud, grating interference. On the road we picked up Janine and Celine and then finally we were joined by Annie. Team Chica was complete and ready for action!!! We drove around the reserve searching for somewhere that we could find a signal from. As we drove out of the gate and down the road to San Jorge, we were rewarded with a spike on the receiver’s digital display! The next day we went out again to hunt for the receiver and hopefully, retrieve it if it had become detached from the bat. Charlotte, Annie, Jorge and I headed out armed with the telemetry equipment and machetes. The signal seemed to be pointing us into the forest so I suggested we head around to the field and see what sort of signal we could get with nothing blocking the transmission. Jorge announced we should just take the path that was there. Before we could ask where the path was he had vanished into the bushes with the machete and created one. Who needs roads when you have a forest guard with a machete!! I spent the afternoon clambering up and down trees (in some cases being lifted very ungracefully down by Conce and Kasper!!). Though we didn’t find the transmitters we did find the grapefruit grove and had a well-deserved break with some delicious fresh grapefruits!! As we sat on the back of the car contemplating what to do next the receiver suddenly exploded into loud, clear beeping!! At the same time, we heard bats chirruping overhead. The unit must have still been on the bat and it had just emerged. Over the following days the hunt continued and eventually we realised a horrible fact. The electricity pylons were interfering with the signal and we never managed to locate the units before the batteries in the transmitters died. VHF signals can be disrupted by dense vegetation and in the end we were defeated by the Atlantic Forest. Thankfully, Annie collected fantastic data for community analysis of the bat population across Laguna Blanca’s different habitats and everybody had a great time learning how to use the telemetry equipment – a valuable tool in any field biologist arsenal!! Everyone at PLT would like to say a huge THANK YOU to Annie for leaving the receiver and antennae at RNLB in order to train future interns and volunteers in VHF tracking!!! If you want to gain experience living and working in the field while having the time of your life check out