April 2009


 

One of the most difficult challenges of this project is getting our radio-collared agoutis to remove and cache tagged seeds. We have just completed our first successful seed experiment trials. As one can see from the video, Frank takes three seeds from the experiment. He buries two of them right next to the experiment and then carries the third away. Once we match up the tagged seed to the collared agouti from the photos, we return to the cached seeds and attach a radio tag to monitor the fate of the seed. In this case, Frank didn’t carry the seeds very far. We think he might come back to these seeds later, move them further from the experiment, and then save them to eat during the lean months when few foods are available.

 

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A radio tag tied to a cached seed. Note the bright yellow string partially buried in the ground. At the other end of the string is a buried Astrocaryum seed. After this picture was taken, we attached the transmitter to a small magnet duct taped to a nail in the ground (you can see the top of the green duct tape just above the seed transmitter). The long wire on the transmitter increases the signal strength and allows us to monitor any movements of the seed using the ARTS system.

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In order to determine the amount of food available for our 20 collared agoutis, we need a measure of Astrocaryum fruit abundance for each agouti territory. During the trapping, we tried to catch animals living in areas with either really high or very low food abundance. During the trapping period, we used Astocaryum abundance maps made from aerial photographs to determine where we would trap. Even though these maps give a very good approximation of the number of Astrocaryum trees per area, we needed a more accurate and direct measure. During April, we counted the amount of fruits and marked the location all the Astrocaryum trees in the 20 agouti territories. Amazingly, we were able to finish the mapping in less than 3 weeks. The result is that we caught some agoutis which live in territories with very low fruit abundance (Barry, Wilhelmina and Femke) and some which live in areas full of fruit (Pam and Fiona). Over all, the agoutis we captured live in a continuum of low vs. high fruit abundance, perfect for testing the fruit abundance hypothesis.fruit-abundance-per-agouti1

Twenty agouti home ranges. The pink circles represent Astrocaryum trees. The larger the circle, the more fruit in the tree. Note that some territories have very little fruit and some are almost completely filled with Astrocaryum trees.

 

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