The forecast said rain. But it’d said that every day for the past week and not a drop had fallen from the sky. So much for the wet season. Even as lightning flashed out to sea whilst I tucked myself into bed, I was sceptical. But it came, and it came with force. No rain falls like rain in the tropics. The roof was suddenly pummelled with a deafening deluge, waking me from a dream. Thunder boomed overhead. My brain immediately wondered what I might have foolishly left outside. My socks were hanging out to dry. Did we close the truck windows? I expected to hear my husband stirring in the very creaky bunk below. Surely he couldn’t sleep through the noise. I considered waking him, to make sure he didn’t miss the awe-inspiring event – we both love a good storm – but figured if he can sleep through it then he must need the extra zzz’s. So I lay in my bed, counting the time between the flashes of lightning and the rumble of thunder. Then as quickly as it had appeared, it stopped. Silence. Sleep overcame me and I awoke to the now familiar blue sky, and blazing sunshine.
I’m in the Cayman Sister Islands as a volunteer looking for cryptic reptiles. The real focus is the snakes, of which there are five endemic species found nowhere else on earth: Cayman Brac racer snake, Little Cayman racer snake, Cayman Brac ground boa, Little Cayman ground boa, Cayman Brac blind snake. Apart from the racer snakes, the rest are rarely seen so very little is known about where they live and their population sizes. In theory, there could even be a Little Cayman blind snake, a species yet unknown to science. A species which we’d really like to find.
Trying to find well camouflaged snakes, some of which live underground, sounds like an impossible task. So, finding them takes a multipronged approach. Drift fences are dug into the ground to funnel creatures along, which then fall into buried pitfall traps aka buckets or plant pots. So far, the pitfalls are turning out to be a great method for catching hermit crabs and the occasional scorpion. Improvised ‘crab excluders’, aka party plates, keep the biggest hermits out which could be a risk to any reptiles which also find their way in.
A common method for surveying reptiles is the use of refugia. In our case, we’ve laid out large pieces of plywood and corrugated plastic amongst the leaf litter around Little Cayman. These act as refuges for reptiles – and other critters – providing a cool, safe place to wait out the hottest part of the day. We then approach them in pairs, one to gently lift the refugia and another waiting to dive in and catch anything of note i.e. potential new species to science. This time, we weren’t so lucky.
The final method is walking very slowly along transect lines, checking every branch, nook and cranny for reptiles and amphibians. These are often quiet during the day, as reptiles are hiding from the worst of the heat or are sufficiently warmed up to be able to scurry away before you can lock your eyes on them. The night transects however, are a different story. Green and brown anoles sleep on leaves. So, once you’ve got your eye in for these snoozing little lizards, there can be plenty to see. And it’s not just lizards that snooze – I’ve come across dragonflies, hummingbird hawk moths, spiders, caterpillars, birds, and treefrogs. The best find, though, was a ground boa on Cayman Brac. Only a handful or two of these snakes have been seen in the area in the last 50 years, making it a very exciting find indeed.
But it’s not just the promise of sleepy critters that makes the night transects so appealing. Given how small the islands are, all of the routes are within a stone’s throw of the sea, whether that’s in front of or below you. The night-time soundscape always consists of lapping waves or roaring surf, a chorus of crickets and cicadas, the scuttling sound of land and hermit crabs in the leaf litter. And if you’re lucky, singing treefrogs and the clash of thunder somewhere over the ocean. More often than not, if you turn your headtorch off you’re not left in the dark for long. Your eyes quickly adjust to the night sky littered with stars, intermittently illuminated by flashes of lightning out to sea. It’s hurricane season in the Caribbean, so storms are frequent, although very few of them seem to reach the Caymans. It's quite the experience to be stood alone in complete darkness, surrounded by unfamiliar sounds of the forest, with the occasional flash out to sea where nothing but water stands between you and the horizon for a long way.
The fieldwork itself isn’t strenuous, except for the unrelenting heat. But the native plants can make for an exciting time. Bashing through the dense undergrowth on top of sharp, unforgiving limestone karst frequently leaves my legs scratched and bruised, but knowing your plant ID is crucial in a place like this. Several plants come with strict warnings. Maiden plum releases a caustic sap at the slightest touch, which can cause severe blisters 24hrs later, and stains your clothing black. And of course, the sap is not easy to clean off. And then there’s the manchineel. Also known as the tree of death. Exactly as fun as it sounds, every aspect of the tree is dangerous – the bark, leaves, sap, fruits. Any contact causes severe blistering, requiring medical attention. You can’t even chop the tree down and burn it, as the smoke can cause blistering and blindness. And don’t even think about sheltering beneath it during a downpour, as the sap will rain down on you, making you regret every decision that led you to that moment.
But with risk comes reward. The islands are home to several exciting species, some found nowhere else on earth. One notable reptile is the Sister Islands rock iguana, locally known as siri. These fabulous beasts are often found skulking on verges or splayed on the roads in the morning, warming up on the tarmac. Unfortunately, their populations are at risk as feral cats predate on the young iguanas and older ones often fall victim to cars, meaning the populations are being hammered at both ends.
It wouldn’t be right to visit an island and not mention seabirds. What the Caymans lack in seabird diversity they make up for in quality. Two species of booby – from the same family as gannets – breed on the islands. Brown boobies and white-tailed tropicbirds only breed on Cayman Brac’s bluff. Unfortunately, both species have small populations due to cat predation, but are being well-monitored and protected, so there’s hope that the numbers will continue to climb. Little Cayman is host to the country’s only Ramsar site (internationally protected wetland), The Booby Pond. Here, around a third of the Atlantic’s red-footed boobies breed, and they’re an absolute delight to see. They roost and breed in the tops of trees, which seems peculiar for a seabird with webbed feet. Mingled among them are magnificent frigatebirds – in name and in nature. The largest of the frigates, these birds have a kite-shaped wingspan of more than 2m and spend most of their time out at sea, soaring in the thermals. Even more peculiarly for a seabird, they never enter the water. They’ll swoop down to swipe fish and squid from the surface of the sea, or they’ll kleptoparasitise – that is, they’ll chase other birds until they drop or regurgitate their catch, which the frigates will then swoop in to catch and enjoy for themselves. Delicious.
Unlike the frigates however, I was keen to get my feet wet. The islands are surrounded with golden sands, crystal blue seas and top-class coral reefs for some aquatic respite from the sun. Swimming out towards the wall which suddenly plummets into the deep is some of the best snorkelling I’ve ever experienced. Sting rays, huge queen conches, nurse sharks, barracuda, rainbow parrotfish, Nassau groupers, triggerfish, moray eels and corals galore. All in water that matches the temperature of the air. There’s even a turtle or two out there for the lucky ones.
This DarwinPlus project is a collaboration between the University of Aberdeen, RSPB, Department of Environment, and National Trust for the Cayman Islands.
As always, very interesting descriptions illustrated by amazing photography. Thank you from Paddy O'Connor.