Understanding the biology of juvenile Rainbow Boas

By R. Graham Reynolds and Cory Deal

It’s a beautiful autumn evening in North Caicos, a perfect time to relax on a porch or take a walk on the beach. A warm rain begins as the sun goes down, perhaps suggesting that indoor activities would be more appropriate. But Cory and I have different plans, for the evening rain means only one thing — snakes!

We don some rain gear, headlamps and boots and head in to Kew to meet Naqqi Manco of the Department of Environment & Coastal Resources (DECR), who has graciously agreed to join us out in the forest on a rainy night. As we gear up, our activities and plans catch the attention of Kew high school student Naz Missick, who volunteers himself as a research assistant.
We can probably safely assume that most people don’t venture into the forest on a rainy night, but for us this is paradise. The forest takes on a whole new character at night, a welcoming embrace of soft shadows and quiet solitude. The rain adds to the character, summoning forth a variety of sweet and earthy scents that mingle with the salty air, providing a rich olfactory experience. Insects buzz softly as we make our way through the large trees of the tropical dry forest, one of the few remaining stands of forest in the Bahamian Archipelago and a poignant reminder of the grand mahogany forests that used to cover these islands hundreds of years ago.
We walk quietly, enjoying the majesty of the experience, scanning our headlamps slowly across the path and along old rock walls. Suddenly, a small tubular shape appears in the misty beam of my headlamp on the path ahead — could this be our quarry? I signal to the others and we gather around to identify the creature. As we lean in, a small forked tongue flickers in and out and the lights reveal it to be a Caicos Dwarf Boa, one of three species of snakes native to the Turks & Caicos, the other two being the Caicos Blindsnake and the Rainbow Boa. A full grown dwarf boa may only be 25 cm long, as they are the smallest constricting snakes in the world, and are handsome and completely harmless creatures.

We are excited by the find, but Cory and I have come to the Turks & Caicos in search of something else — baby Rainbow Boas. These snakes are also known locally as “red snakes,” “cat snakes” and “chicken snakes,” while their scientific appellation is the Turks Island Boa, Epicrates chrysogaster chrysogaster. Though little is known about these rainbow boas, which are only found on a few islands in the Turks & Caicos, almost nothing is known about the biology of the babies.
Rainbow boa females give live birth to a litter of offspring every two years, though very little information exists on the size of the clutches, the number of offspring per clutch, or the size of the offspring and their growth during their first few months. In addition, scientists who study these boas, ourselves included, have noted that baby rainbow boas, which are bright orange for the first few months of life, are extremely difficult to find and are rarely encountered during our surveys. It has even been suggested that the babies are using different habitats than the adults, taking to the trees or retreating underground during their first few months of life. In addition, the smallest boas we have found previously in our work have been greater than 450 mm snout-vent length (snout-vent length is a standard measurement for reptiles that measures the length of the body from the snout to the cloacal opening), and estimating the age of these animals proves difficult if nothing is known about sizes and growth rates of juveniles.
Cory and I have decided to rectify this paucity of information as part of her independent study in science through her school in Florida. We planned our trip for the start of the rainy season in October, the time when the females have just given birth, in the hopes of finding baby boas in the wild. Boas that we caught were measured and weighed, and a small piece of skin was clipped for DNA analysis. In addition, we attempted to characterize the habitat and food supply of baby boas in order to understand whether they were indeed living in different habitats that the adults.
Back in the forest, we release the dwarf boa and continue on our way, hopeful that our next find will be a baby rainbow boa. As the hours pass we enjoy ourselves immensely, walking around in this beautiful coppice, barely noticing the rain as it collects on the branches above us and slides down the trunks of the trees, making rain gear rather unnecessary. Our search thus far proves fruitless, tangibly emphasizing that baby rainbow boas are indeed difficult to find. As we make our way out of the forest, we scan some rock walls in vain until “BINGO!” a skinny shape appears on the wall in front of us. A juvenile boa! We capture the animal, take our measurements and samples, photograph her (it was a female), and then release her. This small snake, a yearling, becomes the first entry in our data that will help us to understand the juvenile biology of these amazingly beautiful snakes.
After nearly four years of research on rainbow boas in the Turks & Caicos, we have a much better understanding of these animals, including the babies. Rainbow boas give birth in the summer and early fall, from around July to October, to a litter of 10–27 bright orange babies. These babies weigh on average 6 grams and are about 290 mm long from the snout to the vent. During the first few months, the babies appear to grow roughly 20.6 mm per month, a speedy growth rate resulting from a diet of small Anole lizards and geckoes. By the time the babies reach about 9 months of age, or about 17 g in weight and 400 mm long, most of the orange coloration is gone and is replaced by a gray background color with grayish-brown spots or stripes. In a few rare instances, the adult boas will retain the orange or red coloration, never changing to gray, and indeed one of these “red snakes” was found on Provo recently and brought to the DECR.
Importantly, we have found that baby boas will use similar habitats as adults, living under rocks during the day and venturing out on the ground at night. An important component of this discovery is determining that their food — baby Anole lizards — occurs on the ground. We found plenty of these lizards on or near the ground at night, with the only exception being areas where their predators, the Curly-tailed Lizards, are abundant. In these areas the anoles are in the bushes and trees, out of reach of the curly tails, and the baby boas might follow them into these arboreal habitats.
So, where do all the babies go? Why, right where their parents go, or wherever their food goes; but the babies are just hard to find!

R. Graham Reynolds is a Ph.D. candidate and herpetologist at the University of Tennessee, Knoxville, USA. You may see more of his work on reptile conservation and genetics at the National Environmental Centre on Providenciales, and learn more about the reptiles of the Turks & Caicos at web.utk.edu/~rreyno16/reptilestci.htm.

Cory Deal is a high school student in Vero Beach, Florida who is completing an independent research project on the biology of baby rainbow boas.

The authors are appreciative of the assistance of B. Naqqi Manco and Naz Missick in the field, as well as the Department of Environment & Coastal Resources, especially Brian Riggs, Eric Salamanca, Wesley Clerveaux, and Marlon Hibbert. We thank the Turks & Caicos National Trust for logistical support and the Turks & Caicos Islands Government for permission to work in the Islands. The senior author’s research is funded by the University of Tennessee, the San Diego Zoo, the American Museum of Natural History, the American Philosophical Society, Sigma Xi — the Scientific Research Society, and the W.K. McClure Scholarship for the Study of World Affairs.