This month’s A Load of Croc is written by CRC Research Associate Everett Madsen who is assisting CRC in our nest ecology surveys.

American crocodile eggs found on Turneffe Atoll with TASA rangers. This research was supported by Sea of Change Foundation and the Smithsonian.

Here at the CRC, we are always looking for ways to better our understanding of crocodilian ecology within Belize. Our nocturnal eyeshine, mark-recapture, and nest surveys tell us a lot about the population trends and relative health of the crocodiles. All data collected is valuable for the conservation of Morelet’s and American crocodiles in Belize.

In April of 2022, the CRC launched a new project aimed and learning about the microclimates of crocodile nests and the influences on them by construction materials used by the females. This project will use small data loggers placed in the egg chambers of nests to record temperature and humidity every 5 minutes over the course of the incubation period for the eggs. Since crocodile’s experience temperature-dependent sex determination, it is very important that the egg chamber of the nest is kept within a narrow temperature window for incubation. However, with issues such as habitat loss marginalizing crocodiles, females in some places have resorted to using materials for nest construction that deviate from the norm. For example, American crocodiles historically nested on elevated beach ridges along the coast where they dig hole nests in sand. However, with increased coastal development we have observed them nesting in very different habitats around the Placencia Lagoon using markedly different substrates such as clay. How they manage to achieve similar incubation characteristics or the implications of slight differences will be interesting to find out!

TASA ranger uncovering an American crocodile nest for our data logger project

On April 28-29, the CRC conducted nest surveys on Turneffe Atoll in collaboration with our NGO partners TASA, and managed to find three American crocodile nests. Not only was this the first data on nests collected on the islands since 2004, but we successfully managed to deploy data loggers into the nests of this historical nesting stronghold which will provide a reference for microclimates under normal nesting conditions. Additionally, we searched an area of the Placencia Lagoon known as Cardelli where American crocodiles are known to nest in an area with a very unique clay substrate. Unfortunately no nests were found this season, however with signs of crocodile activity such as slide marks, we know they are still visiting there. Luckily this nesting season is only serving as preliminary data, so next season we will deploy multiple camera traps to pinpoint exactly where the females are laying their eggs. Next year, we will also explore Belize City and the surrounding areas for nests with the hopes of discovering more unique behavioral adaptations with nest site selection.

We look forward to bringing more updates on the American crocodile nests as our data loggers provide us insight into their nesting ecology, as well as the search for Morelet’s crocodile nests to follow. Until then, stay tuned!

We thank Sea of Change for supporting our American crocodile countrywide survey, and the Smithsonian for financially supporting our work at Turneffe Atoll.

These eggs were laid within a week of us finding the nest! We can tell by the band width of the egg
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