Tag Archives: Iguanas

The boa strikes back!

Our mission here on Big Ambergris Cay was to work on iguanas. And we did, don’t get me wrong. We collected some really good data, including some relative population abundance data through the use of road transects. Moreover, a party of two researchers from the RSPB (Royal Society for the Protection of Birds) were helping us during this trip. They were particularly interested in collecting data on the possible presence of invasive mammals like rats and mice. Luckily it seems that these rodents are not present on the island, which is, of course, good news for iguanas and the rest of the endemic fauna. Giving the additional development planned for the island, the RSPB crew will also help in the development of a biosecurity plan for Big Ambergris Cay. With incoming barges full of materials hitch-hiking of undesired animals is possible and a biosecurity plan is fundamental to keep rats off the island.

Sarah Havery, from the RSPB crew, handling a male iguana at Calicos Jack.
A female iguana hanging on a tree. When shrubs and small trees have new foliage iguanas like to climb on branches to reach out for the new leaves.
A close up of the same iguana.

The title of this post, though, gives away the fact that the great protagonists of this trip were also boas. During the week on Big Ambergris Cay we had more than one encounter with these reptiles. A couple of nights ago some of the permanent workers of the island found a rather large female boa hanging around the dorms.

Me (holding the boa’s head and body), Dr. Gerber (center) and George Waters (with the hat), processing the boa.

In previous posts I showed a few pictures of a boa having lunch with a curly tail lizard. Boas are predators, and juvenile iguanas, 1 or 2 years old, are approximately of the same size of an adult curly tail, if not smaller.

Yesterday, during our last road transect we saw and documented a boa eating a juvenile iguana. We know this happens on the island, but documented records are rather scant.

We were cruising on the island looking for iguana to log during our transect and my eyes picked the cutout of a boa on the ground. It was about 16:50 in the afternoon. Boas are generally nocturnal predators and the first thing that I thought was a road kill. We stopped to check whether the animal was one previously captured and marked. We were all surprised to find out that the boa was well alive. The one not doing so well was the juvenile hanging from its mouth.

What probably happened is that the boa found the iguana’s burrow and went right in. It likely strangled its prey in the burrow and then pulled it out to eat it outside. When we arrived the boa was taking the little iguana towards some bushes, probably to eat it away from the sun and in a more sheltered area. Here are a few shots that I took with my camera. Enjoy, comment, share.

Iguana Work on Little Cayman

I couldn’t have thought of a better way to end this hot summer than some iguana field work. I am on Little Cayman now, helping out my colleague and friend Jen Moss with the data collection for her PhD project. She works with the Sister Island Rock Iguanas, Cyclura nubila caymanensis. As part of her project she is trying to monitor the reproductive activity of adult iguanas on this beautiful island.

In the last couple of months Jen spent quite some time in the field tracking down females and trying to figure out where they nested. Now is hatching time and, with the help of four volunteers, including me, she is trying to monitor how many hatchling will come out from the nests that she was able to identify. Briefly, this is how it works:

  • identified nests are surrounded by an enclosure (we generally use metal flashing)
Hatchling enclosure
Hatchling enclosure






  • the enclosure has to be large enough to make sure that the egg chamber (which is underground) is inside it
  • we build a little shaded area in the center of the enclosure, to make sure the hatchlings can get away from the sun
  • each enclosure is monitored every 2 hours so that the hatchlings do not spend too much time inside the metal flashing
  • after processing them, the hatchlings are finally released in the wild

The work is rather exhausting. Patience is probably the main ingredient for such kind of work. Walking all day long across the island checking on those enclosures is no joke. The heat, the mosquitoes, the sweat, the sun, and the occasional iguana that hasn’t been tagged yet….all these factors can make the days veeeery long and tiring. Luckily, Jen is not alone in this endeavor. She has three volunteer helping her. Me? Well, I am the fourth one, tagging along to learn more about the nest work and how to deal with hatchlings.

David Herz and Tanja Laaser applying colored beads to an adult for quick remote identification of individuals.
Jen Moss (aka DaBoss) holding a rather large male. Anna Jackson is about to collect head measurements of this individual.

Stay tuned to learn more about these wonderful animals and see pictures of the adorable babies.