May 2010


Seed tracking season is in full swing here on BCI.  And the seeds are moving amazing amounts.

Agoutis burry seeds to give themselves a storehouse of food for later in the year, when very few trees have ripe fruit.  The trees are happy about this, because it puts their seeds in a good place to germinate – underground.  We are studying how far agoutis move these seeds and what determines their fate, questions important both from the plant perspective (forest regeneration, species diversity) and from the animal’s perspective (surviving the lean season).

To test our hypotheses, we need an agouti of known identity to cache a seed, which we then follow long-term with a small radio-transmitter.  Earlier this year we trapped a bunch of agoutis and marked them, now we are using camera traps to record which agouti initially takes the seed away and buries it.  We are aiming for at least 200 seeds cached by known agoutis, and so far we are up to 35, a pretty good start.

You would think that tracking 35 seeds wouldn’t be that hard, how often can one seed move?  Turns out, some seeds are moving almost every day.  At least in the first week we have seven seeds that have moved five or more times. But is it the same agouti managing its own caches, or massive thievery?

To address this question we are following a subset of our tracked seeds with camera traps.   When a known agouti buries a seed we use the radio-tag to find it, and then put a camera trap nearby to record what happens next. These results are just starting to come in, but its already obvious that these early seed movements are largely due to thievery.

Here is a video of a thief.  This seed was originally cached by Shelia, a radio-collared agouti, but then it is stolen by Sharpee, an agouti with ear tags and a white tuft of hair on its side.

We have even had a reciprocal theft.  Some other agouti stole a seed that Shelia cached, moved it 12m away and reached it.  Then 2 days later Shelia found it, dug it up, and moved it 70 m away.  We’ve moved the camera nearby and will keep tracking these seeds until they germinate into a new baby tree, or get munched by a hungry agouti.

Bonus footage: another cache thievery

The seeds, they are a moving.

Seed tracking season is in full swing here on BCI.  And the seeds are moving amazing amounts.

Agoutis burry seeds to give themselves a storehouse of food for later in the year, when very few trees have ripe fruit.  The trees are happy about this, because it puts their seeds in a good place to germinate – underground.  We are studying how far agoutis move these seeds and what determines their fate, questions important both from the plant perspective (forest regeneration, species diversity) and from the animal’s perspective (surviving the lean season).

To test our hypotheses, we need an agouti of known identity to cache a seed, which we then follow long-term with a small radio-transmitter.  Earlier this year we trapped a bunch of agoutis and marked them, now we are using camera traps to record which agouti initially takes the seed away and buries it.  We are aiming for at least 200 seeds cached by known agoutis, and so far we are up to 35, a pretty good start.

You would think that tracking 35 seeds wouldn’t be that hard, how often can one seed move?  Turns out, some seeds are moving almost every day.  At least in the first week we have seven seeds that have moved five or more times. But is it the same agouti managing its own caches, or massive thievery?

To address this question we are following a subset of our tracked seeds with camera traps.   When a known agouti buries a seed we use the radio-tag to find it, and then put a camera trap nearby to record what happens next. These results are just starting to come in, but its already obvious that these early seed movements are largely due to thievery.

Here is a video of a known agouti (Shelia) coming back and retrieving a seed she had cached a few days before.  She moved it 30m away and reached it.  We moved the camera and are waiting to see what happens next.

Here is a video of a thief.  This seed was originally cached by Shelia, but then …

We have even had a reciprocal theft.  Some other agouti stole a seed that Shelia cached, moved it xxm away and reached it.  Then 2 days later Shelia found it, dug it up, and moved it xx m away.  We’ve moved the camera nearby and will keep tracking these seeds until they germinate into a new baby tree, or get munched by a hungry agouti.

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It was a typical night scene on BCI, a few folks were tapping away on their computers or eyeballing bugs through microscopes, while others enjoyed some ‘green sodas’ on the porch. But not the bat crew, they were out working on bats.  They didn’t go far from home tonight, just down the sidewalk by the dorms to film some bats with fancy German technology.

Suddenly Insa was back down at the lab, a bit too excited to just be fetching equipment.  Oh no, she had just had a once-in-a-lifetime experience and wanted to share it.  She saw an ocelot attack a sloth.

Here is a description of the event from Kerstin Wilhelm & Insa Wagner: “On the 22nd of May we were on the stairs leading to C house at ca. 9.30 pm when we saw the shrubs moving around. Looking closer we saw a sloth climbing up a tree ~2m off the ground. A second later we also saw the ocelot on the hill next to the sloth. The ocelot was jumping up to the sloth and hanging on him by his claws. The sloth managed to climb up the tree again but then the ocelot attacked a second time, biting the back of the sloth, and dragging it to the ground. But the sloth climbed up again. Then for the third time the ocelot jumped up to get the sloth, this time biting its neck and dragging it down. This bite seemed to immobilize the sloth, and the ocelot rested for a few meters away from the sloth. Then he went back to the sloth and started to eat it, pulling off the fur and cracking the bones.”

Word leaked out the BCI residents slowly at first.  The ocelot was, in fact, eating the sloth just 1m off the sidewalk, next to the dorms, and Insa didn’t want to scare it off.  But this ocelot wasn’t going anywhere.  He had his meal and was going to enjoy it – if 15 bipedal primates wanted to watch, that was fine with him.

This once-in-a-lifetime experience for lucky BCI nightowls was the end-of-a-lifetime experience for one unlucky 3-toed sloth.   Hushed exclamations of excitement and “isn’t the ocelot cute” changed to gasps of horror when it became obvious to all those watching that the sloth was being eaten alive.  As visible in this video from Melanie Mangold, this sloth is hopelessly waving its arms around as the ocelot plucks its hair out and then begins consuming it from its soft underparts.

Nature is cruel.  Ocelots must eat, and other animals suffer as a consequence.  Sloths are actually one of ocelot’s favorite foods.  Ricardo Moreno found that 3-toed sloths made up about 8% of ocelot diet in Central Panama and that, together with 2-toed sloths, they were second only to rodents in their importance.  How exactly ocelots catch sloths remain a mystery.  Ocelots are not great climbers, but they might scamper up to nab a low-hanging sloth.   Sloths venture down to the ground about once a week to go to the bathroom.  This is risky behavior for such a slow and defenseless creature.   In fact, Bryson Voirin found that even owls on BCI could kill a sloth as it visits its toilet.  Its hard to tell from this night’s observation if the battle started in the trees or on the ground.

After munching on the sloth for about 2hrs the ocelot eventually sauntered away, crossing the sidewalk, probably going down to the canal for a drink.  When drinking he should look out for crocodiles*, because nature is cruel, and always hungry!

bonus footage from a camera trap set by Sumana

*Note of added proof: one of our radio-collared ocelots was eaten by a crocodile in 2005.

Throughout Februari-April, we set up camera-traps near agouti refuges and sleeping spots. We did this because -until now- not much is known about these sleeping spots and the nocturnal activity of agoutis.

We found that agoutis use three types of refuges: burrows (holes in the ground, often in buttress roots), hollow logs and dense vine tangle-vegetation. Most agoutis enter the refuge at sunset and once they are in the burrow, they do not tend to come out before sunrise.

The main purpose of these refuges is that they offer protection against predation that often occurs at night when ocelots (the main agouti-predators) are most active. Camera-footage suggests that ocelots actively inspect agouti-refuges to find their prey. Although the ocelots try hard to get to the agouti, none of the agoutis in this video were killed.

In total, we camera-trapped about 13 different refuges throughout February-April; more than half of these were visited by ocelots, some even had regular visits!

Note that in this video, some pictures look closer together in time than they really are.

The Astrocaryum is in fruit, the agoutis are caching seeds, and we are running around behind them with camera traps and radio tracking gear.  We have (yet another) outstanding team for this year’s field work, complete with team jerseys.

Agouti Team 2010: Ben Hirsch, Roland Kays, Willem-Jan Emsens, Sumana Serchan, Lieneke Bakker, Brian Watts (not pictured: Patrick Jansen)