Jaguars Increase Their Take of Green Turtles at Tortuguero

Winter 2001 Issue Articles:

* New Threat Facing Loggerhead Sea Turtles in Florida
* Jaguars Increase Their Take of Green Turtles at Tortuguero

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Jaguars Increase Their Take of Green Turtles at Tortuguero

By Sebastian Troëng

Turtle tracks are not the only tracks one can find on the Tortuguero beach these days. Over the last couple of years, we have seen a steady increase in the number of tracks from the largest neotropical cat, the jaguar, on Tortuguero beach.

This carcass was all that remained of a green sea turtle that had been attacked and killed by a jaguar in Tortuguero National Park, Costa Rica. Photo by Sebastian Troëng

Sea turtles are subjected to much predation during their early years by a wide variety of predators. However, only sharks, crocodiles, orcas and jaguars are known to be able to kill adult sea turtles. Jaguars have been reported to kill nesting sea turtles on distant beaches in Suriname, French Guiana and even in Corcovado National Park on the Pacific coast of Costa Rica. In Tortuguero, sea turtles killed by jaguars were not commonly seen until 1997. Researchers and conservationists have only two records of killed green turtles before that year. Then in 1997, track surveyor Alonso Rankin saw a female jaguar with two cubs feeding on a green turtle they had killed on the beach. All in all, Alonso counted four dead green turtles killed by jaguars in that year. The following year he added 25, and in 1999 his brother Eddy, who by then had taken over the track counts, recorded 22 killed green turtles and two leatherbacks. This past year, with the help of Ph.D. student Manjula Tiwari and her Brazilian assistant Luciano Soares, CCC tallied 60 green turtles killed by jaguars!

Twice, Manjula and Luciano saw the jaguar sitting on the beach and once, Luciano followed a turtle track into the vegetation behind the beach, only to see the jaguar resting behind the dead turtle. As the jaguar spotted Luciano, it put its front paws on top of the carapace and growled defensively. Needless to say, Luciano took off swiftly.

Jaguars are strong animals and can kill their prey by crushing its skull or breaking its neck with their powerful bite. Sometimes, the jaguar drags a dead green turtle into the vegetation for 25 meters or more, in spite of the turtles sometimes weighing in excess of 150 kg (330 lbs.).

When CCC first realized that the jaguars were using the beach and the turtles, of course the organization became worried that it might be unsafe for turtle taggers roaming the same beach. CCC staff contacted several jaguar researchers and was told reassuringly by all of them that there have been no recorded jaguar attacks on humans. Their prediction has so far held true and we are now getting used to sharing the beach with the spotted cats.

Even the giant leatherback sea turtles are not immune to the jaguar’s very powerful crushing bite.Photo by Sebastian Troëng

Tortuguero villagers and National Park Administrator Eduardo Chamorro, have told CCC that jaguars and other spotted cats in the area, such as the ocelot, the margay and the lesser spotted cat were intensively hunted in the 1960s and early 1970s for their beautiful skins. The skins were sold to Nicaraguan traders and later exported to European markets. The luck of the cats turned when Tortuguero National Park was created in 1975 and a ban on hunting the cats was enforced.

Jaguars killing green turtles are part of the natural process of predator and prey and CCC is not doing anything to limit the turtle kills. We have to remember that one of the important ecological functions that sea turtles fill is to move energy from marine habitats to beaches and the adjacent forests. The green turtles that are eaten by jaguars provide an energy flow between sea grass beds and the tropical rainforest.

When we consider how rare the predator-prey relationship is between endangered green turtles and threatened jaguars, we have to study it in detail. CCC researchers recently published an account of the observations made on turtles killed by jaguars at Tortuguero, 1997-1999, in the scientific journal Chelonian Conservation and Biology. Since then, track surveyor Eddy Rankin has continued to record the number and location of the killed turtles. Damien Hussy, a French research assistant with the 2000 green turtle program, went on extensive walks to record jaguar tracks and concluded that at least two jaguars are walking the beach in pursuit of their carapaced prey.

Using photographs of paw prints, researchers can determine the size and number of jaguars in an area. Photo by Sebastian Troëng

Recently, we have also started to take photos of the jaguar tracks and we are forwarding them to Wildlife Conservation Society jaguar expert, Carolyn Miller in Belize, for analysis. The effort is part of a regional initiative to determine if individual jaguars can be identified from their tracks. In the future, we are also hoping to be able to study the jaguars in more detail using camera traps.

We think that several hypothetical factors may be involved in causing the increase in jaguar predation on nesting sea turtles at Tortuguero: The jaguar population may have increased in recent years as a result of enforcement of protective legislation in Tortuguero National Park; Deforestation for agriculture and cattle ranching, inland from Tortuguero, may be pushing jaguars toward the coast where more intact forest and suitable jaguar habitat remain; Possibly a decline in population of other prey may have left the jaguars with less prey options and increased pressures on sea turtles; It could also be a female jaguar that has taught her cubs to feed on the nesting turtles. Jaguars are known to be opportunistic hunters and it would not be strange if this was the case.

It is nice to be able to report that Tortuguero, already a special place full of natural magic, has become even more so with the return of the silken cats patrolling the beach at night.