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Missing in Costa Rica: female crocodiles

Male crocodiles suddenly outnumber females. That's not good news for the species.

Cattle farms, he added, have also crept dangerously close to the creeks, allowing cows to trample nests and roam the waters where crocodiles are known to attack.

Female crocodiles nest 5 to 10 meters from the river. They test out as many as seven sites before digging a hole and laying some 30 eggs. Of those, just 3 percent may hatch.

Both scientists are also concerns about the effects of deforestation.

Clearing plant cover removes the earth’s natural coolant. Cement keeps temperatures higher while trees and plants absorb the heat, trapping carbon dioxide and releasing oxygen. While deforestation could have caused the immediate problem of removing shade on the riverbanks, scientists say it could also speed up climate change by ridding the planet of nature’s sink for harmful greenhouse gas.

While many residents and farmers might like to see the huge, sharp-toothed reptiles just disappear, their demise would be harmful for the habitat in which they live, Porras argues. As top-level predators, crocodiles are vital to maintaining their ecosystem, helping control the population of other species and nurturing aquatic plant life with their excrement.

The findings on the sex imbalance came about unexpectedly during an experiment with crocodile translocation, in which Porras and her team relocated crocodiles to different rivers to observe how they lived in a different habitat. Forcible translocation of animals by humans is a management tool used to save a species from extinction or sometimes to protect a human population from dangerous predators.

Distances of up to 20 kilometers didn’t matter, Porras said. The crocodiles found their way back to their families. (Good for crocodile survival; bad for residents, farmers and prey who want crocs out of there.)

During the experiment, the scientists studied the species’ genetic diversity. It was during that study that the sex ratio appeared out of whack.

The crocodile experts say with more funding they intend to continue monitoring the species in different habitats around the country and they hope that with raised awareness Costa Ricans will work to prevent them from becoming another dinosaur in the natural science museum.