Caimaning! (by Paul Kriedemann, intern)
Updated: Jan 4, 2020
16 August 2017
Caimaning...it may not actually be a word, but that’s what we call it on Herpetofauna Team when we go out on the rivers at night to collect data on caiman popoulations. Now that we are here at a new location called Boca Pariamanu Native Community and free from the restrictions of the previous lodge, the caiman research can continue in earnest once again. Back at the previous site, we were dependent on the lodge for access to their boats which, more often than not, were being used for the tourists and the science had to be put on hold. But here at Boca, we have full access to the boats and a schedule has been set, so we will go out twice a week on Tuesdays and Thursdays to sample caiman.
The caiman project is a mark-release-recapture study, which is a common method for studying these crocodilians, of which there are three species in this region of the Peruvian Amazon. Like it says on the tin, what this means is that we capture caiman (identify, measure, weigh, and sex them) and then we mark them with a Passive Integrated Transponder (PIT) tag (i.e. a unique identifier number that is remmotely read by a tag reader placed near it), after which we release them back into the river, stream or lake at the point of capture (having recorded the GPS location), and at a later date attempt to recapture them. It is a long term study that will take years to generate sufficient data. The end goal is to be able to study the physical development of wild individuals as well as all the usual stuff like assessing population densities, distribution, movement patterns, species ratios and so forth.
We start by delineating two monitoring areas, which in the case of the Boca site constitute separate 5-km sections of the Las Piedras River. After we have monitored these two sections of river, and begin recapturing the same individuals over and over again, we move on to the next two 5-km sections of river, and so on up the river. It usually takes about a month to get enough data on these sections. We do this because the idea is, at first, to mark and collect data on the majority of individual caiman in and around a research site, and then to let time pass (6-18 months) and then to return to the area to see what developments or changes in the individuals and population have occurred.
When we are out on the boat at night, we use a flashlight to scan the river focussing on the banks, looking for caiman eye-shine which stands out in the dark like a brilliant bright orange radiance. Their eyes have evolved to gather as much light as possible, which includes a layer of cells at the very back of their retina that reflects light back out which increases the chances that a photon will hit one of the light-sensitive rods in the eye. Catching a caiman, however, is a different story! They are wily and intelligent beings (no wonder they have been around for milions of years) that have no interest in actively assisting with science projects whatsoever and will elude capture with everything they have. If an area has a lot of human activity, they quickly learn that a flashlight means humans are approaching and this often means hunters. They are, after-all, ambush predators, so it is part of their behaviour to observe their surroundings and the movements of their prey and predators alike so they are better prepared to act accordingly when the time comes to kill or escape being killed. They have no idea that we are not hunters and all we want is to do a bit of science that may actually help them in the long run.
There are two likely ways to find a caiman. The first and most likely is to find them in the water. They float with their eyes and nostrils just above the water with their bodies submerged. There are two likely ways in which they will respond to being approached in this scenario. The first is that they will slowly submerge themselves backwards below the surface and probably stay in the immediate area. The second is that they will swim rapidly forwards and then down under the water and disappear for a long time. The other way of finding them will be on the river bank. When approached on the bank, they will quickly run into the water and swim off. The trick is to try and temporarily blind them with the powerful flashlight during the slow approach phase of the chace. They are nocturnal and their eyes are not equipped to process the bright light from a flashlight and if they can’t see the boat approaching because of the light, they are less likely to try and escape.
There are two ways of catching a caiman: with a noose; and with your bare hands. The noose is suspended from a long pole and is set up in such a way that you are able to pull the noose closed from the other end of the pole once the noose is in place. You would try and get it over the caiman's snout without touching its face and then when it is around its neck, you pull the noose closed and, with a bit of luck, you will have a caiman secured on the end of your rope. In the case of your bare hands, you just grab it(!), preferably around the neck using both hands. It is then brought into the boat and the science can begin.
At the time of writing this (Aug 2017), we have been out twice and I got to see caiman for the first time in my life. As it turned out, I got more than just the chance to see them…
There were four first-timers (including myself) that climbed into the boat on Tuesday night, so there was a lot of excitement on the air. A storm had passed over us about half an hour before and it was a few kilometres off in the distance and still very much active, so the atmosphere was literally electric and bright flashes of lightning regularly lit up the night and thunder rumbled loudly intensifying the mood even more. The protocol on the boat at night is that firstly we are not allowed to wear our trusty rubber boots because they would hinder us if we accidentally fell overboard and we needed to swim to safety, and secondly only our mighty leader, Herpetofauna Team coordinator (Dylan Singer), was allowed to use the powerful flashlight and all others must be off because too many lights would interfere with our boat diver's (Calisto) ability to navigate the obstacles in the river and keep us all safe! So, we set off in almost complete darkness, with Calisto's knowledge of his river and the occasional lightning burst lighting our way. We also had to keep silent to avoid scaring off our study subjects. All these factors combined to make the experience intensely exciting! I was personally given the task of managing the datasheet, so I was quite literally on the edge of my seat with pencil in hand awaiting information to be called out to me. It took less than five minutes from the start of the monitoring cruise for us to see our first caiman. Its eyes appeared as obvious as day in Dylan’s flashlight as it sat motionless on a sandy beach on the river’s edge. Maya Klem, Dylan’s right hand (wo)man, quickly took over the flashlight duty as Dylan grabbed the noose and prepared to jump onto the beach to try and capture it as the boat slowly approached it. I was sitting on the right hand side of the boat which was the side that the beach was on and as we approached, I thought, “Wow! I have an EXCELLENT view!”. Before I knew it, my first ever caiman was sitting about two or three meters away from me! It was a beautiful thing indeed! What struck me was how big and alive its eyes were. The crocodiles I am more familiar with back home in South Africa have tiny dead-looking eyes compared to the big, pretty eyes of a caiman. By this time, Dylan was off the boat and was slowly and carefully approaching the miniature dinosaur by land, trying not to startle it, while Maya kept the flashlight intently in its eyes. As soon as Dylan was in position, he began lowering the noose into place but before he had a chance to ensnare it, it suddenly turned towards the boat and darted off with surprising speed into the water and right towards the boat...more specifically, right towards me!
Now, a lot can go through a person’s mind in a situation like this! Things like, “But it has a lot of very sharp teeth!”, and “He was trying to catch it with a rope!” but this was not the case for me at all. My eyes widened and my mind cleared as it came straight at me and I heard my self say, “Do you want me to grab it!?” to which Dylan immediately exclaimed, ‘YES!!” so I instantly switched the clip board with the datasheet on it to my left hand and then reached out the side off the boat into the water with my right hand and, as I marvelled at how graceful its tail swished from side to side as it effortlessly glided through the water straight towards me, I slapped my hand onto its back and wrapped my fingers tightly around its torso and simply plucked it up out of the river! And then there I was sitting in a boat on a small river whose waters eventually flow into the mighty Amazon and I was eye-to-eye with the first caiman I had ever seen; its wet scutes rough and rugged in the palm of my hand, its mouth wide open baring its impressive set of teeth, and its limbs flailing helplessly in the air as it found itself abducted by a very surprised amateur scientist. The team was equally surprised and impressed with the lack of fear and hesitation and the brutal efficiency with which I captured the animal. I guess they thought that, because it was my first encounter with a caiman, I would have been afraid of the thing but I wasn’t at all. We went out to catch caiman and when one presented itself to me like a gift, that’s what I did!
It felt good. I was proud of myself for acting without any indecision and I assumed that I probably looked quite cool holding onto the little monster up in the air like a trophy that I had just instinctively removed from its natural habitat like a bird plucking up a frog with its beak but apparently I didn’t at all. The team were laughing at my reaction to the event because they say I had a look of extreme trepidation on my face and I was holding it at arms-length away from myself like I was afraid it was about to swallow me whole. They joked that the caiman and I both seemed to have the same look of surprise on our faces. But despite this, they were still very impressed and were praising me, but I tried to play it cool and humble by saying that any one of them would have done the same thing had it swam towards them but deep down inside, I was actually very proud of myself.
Once the entertainment and joking about my caiman catching prowess had ended, it was time to take its measurements. It was identified as a Paleosuchus trigonatus or Dwarf caiman. It only turned out to be 61cm long and considering most of that was tail, it makes it very small indeed. Too small to insert a PIT tag even, so we looked for any identifying features and there was a scar above its eye which we recorded and hopefully, if it is caught again in the future, it will be recognised by this mark and the long term research on this individual will happen. Once the measurements had been completed, it was photo time and everyone in the boat had a chance to get some great photos of themselves with a caiman. Well everyone except a guest on our team, Jayde Zimmerman who is here at Boca with Fauna Forever studying medicinal plants, and who had jumped at the chance to join the Herp Team for a night out on the river looking for caiman. She decided that the idea of having a scaly little teeth-filled devil in her hands, which are usually reserved for exploring plants, was a terrible idea and despite lots of encouragement from the team, she remained seated in her spot in the boat like a tree rooted to the ground! She is obviously more of a botanist.
And that was the last caiman we caught that night. We saw seven more before the night was over and we spent a great amount of time trying to catch them and I was amazed at how Calisto was able to manoeuvre the big clumsy looking boat in and out of very tricky situations on the river and its cluttered banks, but the cold and nervous caiman bested us again and again. Dylan explained that because it was cold after the rain and the front that preceded it, they would have been lethargic and, therefore, more apprehensive and flighty than usual because they are, after all, cold-blooded and when not fully charged up, are less confident about being able to defend themselves so they tend to rather simply avoid any danger by vanishing under the water. Although I saw mostly only eye-shine on the banks, Dylan was able to identify all three species of caiman found in this region. Paleosuchus trigonatus or Dwarf caiman, Melanosuchus niger or Black caiman, and Caiman crocodilus or Spectacled caiman. Most of the individuals we saw were juveniles but we did see one big Spectacled caiman on the bank that looked to be at least two meters long. So after an interesting few hours we only had a few lines of data, but memorable data for me!
When we set off on Thursday night, we did so with as much enthusiasm and excitement as we did on my first night. Looking for caiman is always fun. We had two more guests with us this time. Emily Jones and Stacey Clarke, from the Mammal Team, wanted in on the action they had heard so much about back at camp after our Tuesday night excursion and they certainly got it…
Maya wasn’t with us that night so I had been promoted to the front of the boat with Dylan. What this means is that I was up at the front and once he spots eye-shine and gives the signal to Calisto to approach the subject, it becomes my job to take his torch and keep it intently fixed on the caiman while he prepares to capture it. Once again, it took about five minutes from the start of the monitoring for us to see our first eye-shine. As we approached the bank where the eye-shine was coming from, Dylan exclaimed, “Holy s#&t! It’s a big one!” It took a moment for the glowing lights to reveal its true form to me and when it did, I had a little burst of adrenaline because it was MUCH bigger than the little creature I had caught previously. It wasn’t huge by Amazon Jungle standards at all, maybe about two meters, but as the boat got closer and closer, it seemed to become more and more massive. As I was marvelling at the beast, Dylan had already joined it on the bank and was approaching it with the noose at the ready. I was kind of half expecting it to run from Dylan and come at me like the first one we spotted on our previous excursion and I knew without a doubt that this one was way too big for me to reproduce my heroic antics but it remained completely motionless, confident in its’ belief that nothing will mess with it. But it hadn’t considered Dylan’s dogged determination and his dedication to science, and he skilfully got the noose in place around its neck and when he pulled it tight, it was too late for the caimans’ protests to have any effect. It thrashed its head from side to side and its entire body contorted and twisted at it resisted the noose and tried to destroy the pole with its mighty set of teeth. It even gave us a few textbook demonstrations of the classic crocodilian death roll but to no avail. Dylan knows what he is doing and despite the caiman having dragged the battle into the shallow water next to the bank and had a firm grip on the pole with its teeth, it had no chance of escape.
“Hey Paul! Are you comfortable getting into the water with me and this thing?”. “Sure!”, I heard myself say and, barefoot, I jumped off the side of the boat and into battle. It’s one thing sitting on the safety of a boat watching something like this unfold, but another thing all together to be right in the middle of the action. Like my experience with a giant bushmaster a few weeks before, it was thrilling mixture of fear and enthralment. The team burst out laughing when I very seriously asked, “Do you want me to throw myself onto its back like Steve Irwin?” to which Dylan replied in a surprised and reassuring voice, “Uh… no! That’s ok. Just come help me pull it out the water.” So my first task was to take hold of the pole with Dylan and pull the beast from the water and onto the river bank where it would be easier for us to restrain it and get a hold of it to bring it onto the boat with us. After a few heaves we had it on the bank and then Dylan asked me to pry the pole from out of its powerful jaws and I reluctantly admitted to myself that the only way to do this was to use my fingers to try and open its mouth enough to free the pole. So, I hesitantly placed my thumb where its top lip would have been if it had had one and immediately realised this wouldn’t work because I didn’t have nearly enough strength. So I adjusted my grip by adding more fingers from both hands to both the top and bottom jaw and it took a surprising amount of strength to open its mouth but luckily it worked and the pole suddenly flicked out its mouth which instantly slammed shut again. So quick, in fact, that the tip of my thumb got caught in the motion and I got a nasty gash from one of its formidable teeth to brag about when I get to tell this story when I get home.
My second job was to get the noose off from around its neck. Dylan had to first subdue the caiman before I could do this and he did so by coming at it from behind while its attention was on me and then in one fluid, Jedi-like movement, he stepped on its head with his right foot (and apologised to the team in the boat about the apparent violence of this act) to prevent it from being able to thrash its head back towards him and then his left foot further back on its body. He then sat down on its back and restrained its legs by squeezing it with his own legs and took a hold of its neck and told me to loosen the rope securing the noose and then he slackened the rope around its neck and gave me the go ahead to take the noose off. Once it was off and the caiman was secured, it was time to get it into the boat.
I’m sure Dylan and I could have probably wrestled it into the boat by ourselves but I think, because I had so little experience with caiman, he asked Donald Reid Neal II, a dedicated Herp man who has joined us at Fauna Forever for a month, and who we simply call Reid, if he was comfortable to help us get a proper hold of it and lift it up and into the boat. He was game and was on the river bank with us in an instant and after Dylan had given us some instructions, it didn’t take long before we were in the boat with a pretty big caiman and some very wide eyed volunteers!
For such a big and apparently old caiman – Dylan estimated that it was probably about thirty years old – it was in very good condition. Usually caiman this old have way more scars. Life is hard for them, but this one had only been shot in the face and had a huge chunk of its tail missing! Thanks to the extremely hard plate of bone on the caimans’ face this one had obviously narrowly escaped being eaten by a hunter and whoever he chose to share it with and, as to what had happened to its tail, no one will ever know but its probable that it had lost the end of it in a fight with another caiman. The way it had healed left it looking very much like the tail of a coelacanth. A quick scan with the PIT tag scanner revealed that it had no PIT tag in it, so with surgical precision Dylan injected one of the tiny little devices into the section of tail where the PIT tags usually go and I took the opportunity to borrow some of the antiseptic lotion used to clean the puncture wound to also clean my thumb! We then began taking its measurements and there was a funny moment during the examination where the caiman lurched forward in the boat right in the direction of the rest of the volunteers and they all almost fell over backwards as Dylan, Reid and I quickly brought it back under our control. Other than that, getting its measurements went off smoothly and afterwards everyone got to take photos and I even got the chance to hold it by myself for a photo after assuring Dylan that South Africa doesn’t have a suing culture and he wouldn’t be hearing from my lawyer if anything went wrong. And then with a huge splash, we released the big guy and resumed our search in an upstream direction.
The next stretch of river revealed many individual eye-shines but they were all too quick for us or too well protected by the thick vegetation on the river banks for us to be able to catch them and then we came upon an area that suddenly lit up with eye-shine! Dylan counted ten individuals and explained that we had probably found a nursery. It was intensely exciting jumping off the boat with Dylan and onto the sandy river bank that the currents had somehow delivered into the middle of the river creating a large, long pool on one of the giant sand bars, which had formed an ideal spot for a nursery. Dylan ran off very quickly in the direction of the eye-shine and yelled for Reid to join us and that we were to catch as many as we could and before very long, the three of us were spread out on the sand bar heading in every direction the eye-shine from our head-torches took us. The little baby caiman weren’t as excited about the event as we were and simply submerged their little bodies calmly into the safety of the water again and again as we rushed up and down the sand bar to no avail. Dylan and I did catch something though. We came across a sand piper's nest. They were very cute and we shared a quiet private moment together enjoying them. After about twenty minutes on the sand bar and Dylan having ended up chest deep in the river chasing a baby caiman, we admitted the nursery was more effective than we had realised and decided to move on, tail between our legs.
After two or three more empty promises from eye-shine, I heard Dylan mutter under his breath to himself, “OK one more…” and despite it being quite late already, the search went on. I spotted some eye-shine in the water under a tree overhanging the river bank and gave the signal to Calisto, but as we approached I thought this one would get away too because of how dense the vegetation was. Somehow, Calisto managed to manoeuvre the boat perfectly in the direction of the caiman and with a little more speed than usual and as we approached, I saw it try and run away up the river bank but it got held up by one of the many branches and, as I was bracing for the impact of the boat colliding with the tree and the bank, and as Dylan fumbled with the noose pole trying to guide it into position through the trees branches, he eventually abandoned it all together as he realised how masterfully Calisto had steered the boat right at the caiman and that he was going to be able to lean off the front of the boat and grab it with his bare hands from where it struggled with its branch and its fate was sealed. With a shoulder-crunching crash into the tree for Dylan with the full momentum of the boat behind it, he nevertheless caught the caiman very uncomfortably.
It was another Dwarf caiman, a little bit bigger than the one I had caught on our first night out. It was, however, big enough for a PIT tag, so we tagged it and measured it and then the team got to take a few photos again and give all the usual “oohs” and “aahs” for its monstrous cuteness and then we released it with a splash and headed back to port with a sense of scientific satisfaction.
If you'd like to assist Fauna Forever with caiman research in the Peruvian Amazon, please read the details on this page: https://www.faunaforever.org/herpetofauna-volunteer-internship