Predation has strong influences on most animal populations but is almost impossible to observe because it happens unpredictably, and only once in the life of a given potential prey species. This spring with the aid of camera traps, I was lucky enough to record a wide array of predatory behavior on Barro Colorado Island (BCI) in Panama. I was on BCI conducting noninvasive genetics research with ocelots (Leopardus pardalis) ,a mid-sized spotted cat. As part of my research I placed camera traps on ocelot latrines hoping to catch them ‘in the act’ in order to match photo records to genetic fingerprints from scat DNA. One latrine site in particular, in an open area on the end of a peninsula named Harvard, turned out to have a lot more than ocelot toilet behavior going on.
In late February spiny tailed iguanas (Ctenosaura similis) began to nest along the shoreline of Lake Gatun, and I got many photo records of these large reptiles basking in the sun out on Harvard point. I also began to get video records of stalking ocelots crouched low to the ground. Soon enough, I got amazing footage of a male ocelot dragging off very large iguanas twice during the course of one week. While checking my cameras the day after his second kill I was lucky enough to see the ocelot in person, likely still guarding his meal in the underbrush. Many people mistakenly believe that ocelots are nocturnal, however although they frequently hunt at night, they are opportunists and hunt iguanas during the middle of the day when the cold-blooded reptiles are out basking in the sun. Around this same time another male ocelot killed several iguanas along the shore in front of the BCI labs, to the delight of the on looking scientific residents.
Not long after this other reptiles began visiting the point. My cameras frequently captured a very large crocodile (Crocodylus acutus) coming well up from the water, causing me to keep looking over my shoulder each time I scooped ocelot poop from the latrine. Did she have a nest nearby?
Next, turtles (Trachemys scripta) from the lake began to come ashore to lay their eggs in the dirt near the latrine. Like clockwork, white-nosed coatis (Nasua narica) appeared to dig up the eggs and eat them. During the preceding weeks coatis visited every day, resulting in thousands of photo records, and leaving the point strewn with shallow holes surrounded by chewed up turtle egg shells. Then one day in late March I found a starling sequence of photos. In one photo a coati is standing directly in front of the camera, and in the next photo taken less than 2 seconds later, a crocodile is flying across the frame mouth wide open to snap! During the next few weeks I also recorded several videos of the crocodile going after coatis.
In the instances I recorded, the coatis pursued by crocodiles narrowly escaped, however not all coatis are so lucky. According to Dr. Matthew Gompper from the University of Missouri who conducted his PhD. Research on coati behavior on BCI in the early 90’s, one radio collared coati from his study was killed by a crocodile. It was witnessed by one of the forest guards, and for a month or so afterwards he could hear the collar beeping forlornly from the lake, presumably still transmitting from the stomach of the croc. Eventually he recovered part of the skull but never found the collar. According to Ben Hirsch, a postdoc on the agouti project who conducted his PhD. work on coatis in Argentina, coatis tend to like riverine ecosystems, and on BCI they may spend a large portion of time on the lake edge. Thus crocodiles might be an important source of mortality on BCI. In addition, the population of large crocodiles has been steadily increasing in the Canal Zone as a result of a prohibition on crocodile hunting put in place when Panama took control of the canal in 1999. Everyone agrees, there are more BIG crocodiles circling BCI now than any time in the last 100 years. This may be increasing the effective isolation of mammal populations on BCI, due to a greatly increased risk of mortality during swims to and from the mainland.
Interestingly however, it may be predation of crocodiles by coatis that has a strong influence on crocodile demography, not the other way around. In late April on a trip to the point to check my cameras I found a number of large, bloody, mostly eaten crocodile eggs surrounding a shallow hole. I had been walking directly over the crocodile’s nest several times per week for the last three months without even knowing it was there! Over the next few days the coatis dug up and ate every last one of the crocodile’s eggs, ruining her chances for reproduction during this nesting season. This time it was the coatis that had the last meal.
Written by Torrey Rodgers