August 2011


In our first field season we noticed that some seeds traveled so far that they must have moved out of the home range of an agouti. This led us to wonder whether the massive seed re-caching behaviors we observed were the result of one agouti caching its seeds many times or agouti thieves moving seeds from one territory to the next.

To solve this question we needed to be able to identify individual agoutis, which otherwise all look alike. After substantial live-trapping effort we were able to catch >20 agoutis in one portion of the island (in and around the 25 ha plot). We individually marked each agouti we caught with a distinctive radio-collar, ear-tag and/or freeze brand. Then, we put a motion-sensitive camera next to a buried seed where we knew the “owner” and recorded every agouti (or other species) that walked by. This allowed us to determine whether the cached seeds were being dug up and moved by their owners, or by thieves. We are still crunching the numbers from these experiments but in the process discovered a cool video that shows just how crafty agouti thieves can be.

Many rodents bury seeds in times of plenty to save them for lean times, and these hidden food caches are critical to their survival. Rodents will go to great lengths to protect their seeds from potential thieves. For example, Michael Steele and colleagues found that if a squirrel wanted to bury a seed but was being watched, it would often behave “deceptively” by making fake caches and making caches behind trees so the observer could not see the cache being made. While I would have loved to do some similar experiments with the agoutis, it would have been hard to observe the agoutis without scaring them away. However, if you run enough camera traps for enough time you eventually record some surprising clips.

In this case, I didn’t notice what was going on the first time I saw this video, and only recently realized how it shows the subtle dynamics between different agoutis sharing an area. The seed that this camera was monitoring was previously cached by an agouti named Tracy, who can be identified by a small diagonal white freezebrand mark on her body. In the video you can see Tracy come to uncover her seed four months after she originally placed it there (we had a camera there the whole time). Given the high rates of cache movement, Tracy was lucky her seed lasted that long and her strategy of saving food underground for the low food season seems to be a good one. Unfortunately for her, as soon as she begins digging up her cached seed she gets chased away by another more dominant agouti who steals her seed. Even sadder is the fact that Tracy came back to the old cache location a few seconds later to see if it was still there (it wasn’t). While this isn’t fair to Tracy, the other dominant agouti got a free meal on the cheap. The degree to which our agoutis used this kleptoparastic strategy is unclear, but given the behaviors seen in this video, we think it might be a good idea if agoutis used the same sorts of deceptive behavior found in squirrels.


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If you get excited about sensor networks, yagi antenna, live data streams, and agoutis, then you’ll love our new paper in the Computer Journal describing the technical details of the Automated Radio Telemetry System (ARTS) that helped us track animals and seeds in Panama.

 

Photo: ARTS tower rises above the tropical rainforest canopy of BCI to help researchers track the movement and activity of animals and seeds, sending data back to the lab in real-time.

ARTS tower