Researchers from Oregon State University and a team of international scientists have gained new insight into the diet, population density and social interactions of a group of Brazilian jaguars.
Fish and aquatic reptiles dominated the diet of jaguars in a remote wetland in Brazil, representing the first population of jaguars known to feed on few mammals. Additionally, motion-triggered video cameras showed jaguars playing, fishing and traveling together.
The findings, recently published in the journal Ecology, go against beliefs that jaguars are solitary mammals whose social interactions are limited to court or land disputes, said Charlotte Eriksson, a doctoral student at the Oregon State and lead author of the article.
The research took place in a seasonally flooded protected area in the northern part of Brazil’s Pantanal, the largest freshwater wetland in the world. Fishing is prohibited in the area. There are no roads or human settlements nearby, and cattle rearing is not allowed.
The flooded nature of the area, along with the fact that researchers have to cover themselves from head to toe due to an abundance of biting inserts, make it a tough place to work.
“Everything is based on the boat,” Eriksson said. “We obviously cannot drive. And we can’t really walk because there’s water and there’s a ton of jaguars.
Taal Levi, associate professor at the State of Oregon, started the project in collaboration with Brazilian researchers in the region in 2014 after Carlos Peres, professor at the University of East Anglia in the UK, described a place that would have an unusually tall jaguar. population density.
Eriksson is a member of Levi’s lab. She started working on the project in 2017 for her doctoral research. Since then, she has visited the Brazilian site twice, in 2018 and for six weeks in August and September of this year.
For the article just published, the researchers also collected jaguar droppings. They identified nine prey in 138 droppings. The jaguar’s diet was dominated by three groups: reptiles (55%), fish (46%) and mammals (11%).
The finding indicates that the jaguars in this region have by far the most aquatic diet and the least mammal consumption of any jaguar studied previously, the researchers said. Even the tigers of the mangrove forest of the Sundarbans in India, which may be the most comparable large cat family in a habitat similar to the jaguars in the Brazilian region, primarily consume terrestrial mammals.
The researchers also trapped and fitted with a GPS collar 13 jaguars, which spent an average of 96% of their time in the study area. They estimated the jaguar density to be 12.4 per 100 square kilometers, or 36 square miles. This density is two to three times higher than what other scientists have found for jaguars in other parts of South America.
Researchers believe the density is so high and jaguars interact socially in ways never seen before due to the abundance and distribution of aquatic prey, which they call aquatic subsidies, in the region. In other words, their biological needs are met so that they have energy to burn or play.
“If there is a lot of food around, there is less need to fight for it,” Eriksson said.
The researchers used data from 59 camera stations that operated for 8,065 days from 2014 to 2018. Jaguars were detected on 95% of the cameras. A total of 1,594 jaguar videos were obtained, representing 69 unique individual animals. The maximum number of unique jaguars captured by a camera was 15, including nine in 2015.
“Typically, you very rarely see a predator at the top of the camera, as it moves over very large areas,” Eriksson said. “Jaguars were the mammal most often seen on camera, which is really unusual. “
Researchers have documented 80 independent social interactions between adult jaguars. Of these, 85% were between males and females, but 12 were between jaguars of the same sex (a female-female interaction and 11 male-male). Two men even spent 30 minutes in front of the camera playing.
The other authors of the article are Levi and Joel Ruprecht, both of the Oregon State Department of Fisheries, Wildlife and Conservation Sciences at the College of Agricultural Sciences; Daniel Kantek, Selma Miyazaki and Ronaldo G. Morato from the Instituto Chico Mendes of the Brazilian Conservação da Biodiversidade; Manoel dos Santos-Filho from the Universidade do Estado in Mato Grosso, Brazil; and Pérès.