San José, Costa Rica, since 1956

In Guanacaste, too many crocs

From the print edition

Fabricio Pizarro has no trouble spotting a crocodile. The tour guide for Palo Verde Boat Tours sees them all the time relaxing on the riverbanks of the Río Tempisque, in the northwestern province of Guanacaste. 

Lately, Pizarro has noticed more crocs in places he hadn’t before, like in his hometown of Filadelfia, Guanacaste. Crocodiles always skulked around parts of the town, but never like this. Years ago, locals knew which rivers were safe to cool off in. Now, they’re not so sure. 

“People used to go swimming there,” Pizarro, 24, said. “And they don’t now because there are more crocodiles.”

The American crocodile (Crocodylus acutus) is found throughout rivers and brackish water in Costa Rica, on most of the Pacific coast and parts of the Caribbean. Around Río Tempisque, the gigantic reptiles – which can grow up to 6 meters long – are showing up in strange places.

Workers for the National System of Conservation Areas (SINAC), a branch of the Environment Ministry, have received calls to remove crocodiles from cemeteries in Bagaces and a water treatment plant in the provincial capital of Liberia. 

The explosion of crocodiles in the area has grown out of control, with at least 2,300 living in Río Tempisque, which empties into the Gulf of Nicoya and its tributaries. 

Overpopulation seems even more bizarre when considering where it’s occurring. Guanacaste is the fastest-growing province in the country, but cities like Cañas, Liberia, Nicoya and Bagaces are observing increases in croc populations. Although SINAC said urban development is destroying animal habitats in Guanacaste, the number of crocodiles continues to rise, heightening the risk of a clash with an encroaching human population.

Conservationists consider the American crocodile a vulnerable species, and Costa Rican law prohibits hunting them. However, overcrowding has forced local wildlife authorities to enact emergency measures to remove crocodiles from the area. 


Laura Porras, a professor at the National University (UNA) in Heredia, studies crocodile populations in Tempisque. She said residents report up to three crocodile attacks per year there, and milder incidents go unreported. 

She said another phenomenon also could lead to more close encounters: Around Tempisque, male crocodiles outnumber females by three to one. Most males cannot find a mate, and as a result, when mating season begins in September, the crocs act more territorial. 

“They fight with each other for every female, and they grow more aggressive,” Porras said. “It increases the probability of an accident with people.”

Competitive male crocs complicate an already worrying situation, as the reptiles have no natural predators in the region. In other parts of Costa Rica, wild dogs that steal eggs help keep the croc population down. Snakes and birds of prey also eat baby crocodiles. 

Those assailants are less present in Tempisque, where crocodiles grow faster and larger due to the main factor contributing to overpopulation: too much food.

 Many tilapia farms are located in Guanacaste. In time, fish escaped from the farms and swam into the Tempisque basin. 

Tilapia multiplied in the region’s rivers and streams, and now provide an endless supply of meals for the carnivores. (Porras said the crocodiles “eat like pigs.”) They feed on any animal that can be snatched between their powerful jaws, and with the influx of tilapia, crocodiles keep eating and growing to enormous sizes.

As for the surplus of males among the crocodile population, nobody is certain why it is happening. Several possible culprits exist: Climate change could be influencing the sex of crocodile offspring while in the egg, or contaminants in the water or powerful hormones fed to the tilapia could be the cause.

Porras wants to obtain financing to research the toxicology of the crocodiles, in hopes of understanding the cause of the boost in male populations. 

She noted the ratio creates an internecine struggle between crocodiles and with humans. In time, if female crocodile numbers continue to dwindle, the crocodile population could drop off precipitously. Porras and other exerts studying the Tempisque region hope that in time, a balance of male-to-female ratios and crocodile-to-human ratios can be reached. 

Moving them out

At the end of August, SINAC enacted an emergency plan to remove 80 male crocodiles from Guanacaste. 

Wilber Orozco, who leads SINAC’s wildlife conservation efforts in Tempisque, said authorities have extracted 50 crocodiles from that area so far. The organization tries to find locations to place the crocodiles, but it can be a struggle. 

Crocs need a permanent home and cannot be reintroduced into the wild because of overpopulation. They have a lifespan of up to 60 years, and few places exist that can adopt so many of them. A reserve in Caño Negro, a wildlife refuge in northern Costa Rica, took 10 of them. Another 10 were placed in a Guacalito zoo in Tárcoles. The other 30 crocodiles were euthanized. 

Porras and other UNA employees are working on zoning projects with SINAC to find places to put the extra crocodiles. They also are conducting forums in towns near Tempisque to try to better gauge how the problem affects locals. At the end of the year, SINAC will evaluate how well the extractions worked.

“Apart from the mitigation measures, there is a management plan for the medium and long term,” Orozco said. “It involves using public and private companies to help manage the population properly.”

The specifics of that plan remain a work in progress, he acknowledged.

On Sept. 18, Orozco met with residents in Filadelfia to discuss the problem. Villagers are bothered by the crocs, but they try not to overreact. If one approaches someone’s property, locals call SINAC to ask for its removal. But they also threaten to kill crocs if SINAC doesn’t show up. 

Still, residents enjoy the benefits of local wildlife: Crocodiles do help bring tourist dollars. But weariness is mounting, and both human and crocodile populations in Guanacaste are growing faster than officials can come up with a long-term fix. 

“The solution is not just to extract the animals,” Porras said. “We need to establish a way to take care of the population.”

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