Eduardo Carrillo is a Costa Rican biologist and a world-renowned expert on jaguars, not to mention one of my science crushes. He has been interviewed by the BBC and National Geographic, and appears in their videos. He moves through the rainforest like a ghost, and is an expert tracker…he can tell a story from a claw mark and a paw print. In a lifetime of research, he has seen 30 jaguares in the wild.
He is surprisingly shy; he wouldn’t say boo to a goose, but he is determined to share his love of Costa Rican wildlife with the world. He is also kind and has a soft spot for perritos; he’s adopted 24 abandoned dogs that he tends with dedication.
Dr. Carrillo started researching jaguares in Costa Rica long before there was funding to support him. Very little was known about them, though they are the largest cat in the western hemisphere.
However, they were commonly thought to be nocturnal animals.
Dr. Carrillo began his research in the Osa Peninsula, in remote areas that were very difficult to access and dangerously full of aggressive venomous snakes (like the Fer de Lance). He quickly realised that the jaguares specialised on white-lipped peccaries. The peccaries can be dangerous animals; they can form herds of more than 300 individuals and they are known for their aggressive behaviour. Nonetheless, weighing up to 40 kg, they are the preferred food item of the jaguar.
By radio-tagging peccaries and jaguares, Dr. Carrillo found that the jaguar population closely tracks the peccary population: the number of jaguares increases as the number of peccaries increases. In addition, by mapping their behaviour over the course of a day, he found that, contrary to popular belief, the jaguares were most active during the day….at the same time as their primary food item.
This was true only when it was not a new moon. Why would the jaguares change their behaviour during the new moon?
The answer that he found was that the sea turtles come onto shore to lay their eggs during the darkness of the new moon. At these times, the jaguares are almost completely nocturnal. In other words, during the new moon they specialise on sea turtles.
Why the switch? Well, sea turtles are a much easier prey item to capture. They are not aggressive and the jaguar doesn’t run the risk of being gutted by sharp tusks.
If you want to know more about Dr. Carrillo’s work in Costa Rica, here are a few links: