A jaguar’s puzzle solved with scats and carcasses

The diet of jaguars has long been a hot research topic but little is known about the specific prey that these big cats choose to hunt. Stephanny Arroyo and a team of researchers from three Costa Rican NGOs were determined to find more pieces of this puzzle.  They decided to sample 9 kms of coastline in the Tortuguero National Park looking for scats and carcasses on a weekly basis, from 2012 to 2016.  As you can imagine, carcasses are easy to find on an open beach, especially when black vultures raise the alarm by swarming overhead.  However, scats are trickier to detect for the untrained eye and it requires the researcher to closely observe the size, shape and other traits to make sure it does belong to a jaguar.  Each collected scat is soaked in a solution of water and detergent for 48 hours and then washed through fine-mesh filters.  Once dried, only then can the prey’s non-digested remains be identified e.g. claws, tissue and hair.

After four years of data collecting the researchers found 1374 carcasses and 75 scats. 99% of the carcasses corresponded to four sea turtle species, mostly green sea turtle, but also the remains of a gray four-eyed opossum and birds of the Pelican family were found.  Through the scats analysis, another ten species were registered as part of the jaguars diet however, 36% of the remains were unidentifiable – so there are probably even more prey yet to be discovered. For now, we know that these prey include kinkajou, red brocket, white-lipped peccary, green sea turtle hatchlings, green iguana, Geoffroy’s spider monkey, lowland paca, forest cottontail rabbit, sloth, gray four-eyed opossum and the nine-banded armadillo. The later also captured on the camera traps – a method which allowed the Baird’s tapir and the common opossum to be recorded as prey of the jaguar. These results help confirm that the white-lipped peccary is still one the jaguar’s favourite prey but also reaffirms the well-known generalist and opportunistic behavior of this species.

The research uncovered another piece of evidence that has not been explored much anywhere in the world – cannibalism. On the 6 February 2014, a scat containing seven claws of a big feline, either another jaguar or a puma, was found during the weekly fieldwork activities. Stephanny and her colleagues point out a few possible explanations for this finding: social stress caused by multiple individuals converging in one spot; a female defending her off-spring; or individuals defending their prey. According to unpublished work by the Coastal Jaguar Conservation, 13 individuals share at least 29 kms of coastline which is a high-density level for this species.

The researchers can also interpret results from the items that were absent from the scats. Even though most of the prey identified from carcasses were adult sea turtles, there were no remains in the scats. It is likely that jaguars are only eating the soft tissue of these marine creatures and therefore after passing through the digestive system there are no identifiable remains left. These contrasting results bring light to the importance of using a variety of methods while studying diet preferences. The absence of domestic animal carcasses or their remains in the scat was also an important discovery in the human-jaguar conflict context. Often local stories arise of jaguars attacking cattle and dogs which can generate a fear of this feline and in turn create a pressure to hunt them. Using molecular analysis could bring clarity to this polemic topic and maybe even expand the list of prey which jaguars predate on. In the future, the authors also recommend to carry out more surveys further inland and complement it with prey abundance studies to add another piece to the puzzle that is the jaguar’s diet.

Learn more about the research here »

Photo credit: Ian Thomson – «A jaguar (Panthera onca) returning to feed on its prey of a green turtle (Chelonia mydas) at Tortuguero National Park, Costa Rica.»