Ecology of fishing jaguars: Rare social interactions
Date:
October 18, 2021
Source:
Oregon State University
Summary:
Scientists have gained new insights into the diet, population
density and social interactions of a group of Brazilian jaguars.
FULL STORY
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Oregon State University researchers and a team of international scientists
have gained new insights into the diet, population density and social
interactions of a group of Brazilian jaguars.
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Fish and aquatic reptiles dominated the diet of the jaguars in a remote
wetland area of Brazil, representing the first population of jaguars
known to feed minimally on mammals. In addition, motion-triggered video
cameras showed jaguars playing, fishing and traveling together.
The findings, recently published in the journal Ecology, run counter to
beliefs that jaguars are solitary mammals whose social interactions are
limited to courting or disputes over territory, said Charlotte Eriksson,
a doctoral student at Oregon State and lead author of the paper.
The research took place in a seasonally flooded protected area in the
northern portion of the Brazilian Pantanal, the largest freshwater
wetland in the world.
Fishing is prohibited in the area. No roads or human settlements are
nearby, and cattle ranching is not allowed.
The flooded nature of the region, plus the fact that researchers must
cover themselves from head to toe due to an abundance of biting insets,
make it a challenging place to work.
"Everything is boat-based," Eriksson said. "We obviously can't drive. And
we can't really walk because there is water and there's a ton of jaguars."
Taal Levi, an associate professor at Oregon State, initiated the project
in collaboration with Brazilian researchers in the region in 2014 after
Carlos Peres, a professor at the University of East Anglia in the United
Kingdom, described a place rumored to have an unusually high jaguar
population density.
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Eriksson is a member of Levi's lab. She began 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 just-published paper, researchers also collected jaguar scat. They
identified nine prey items in 138 scats. The jaguar diet was dominated
by three groups: reptiles (55%), fish (46%) and mammals (11%).
This finding indicates jaguars in this region have by far the most aquatic
diet and the least mammal consumption of any previously studied jaguar,
the researchers said. Even tigers in the Sundarbans mangrove forest
in India, which may be the most comparable large family of cats in a
similar habitat to the jaguars in the Brazilian region, consume mostly
land-based mammals.
Researchers also trapped and GPS-collared 13 jaguars, who spent on average
96% of their time in the study area. They estimated jaguar density was
12.4 per 100 square kilometers, or 36 square miles. That density is two
to three times higher than what other scientists have found for jaguars
in other regions of South America.
The researchers believe the density is so high and the jaguars are
interacting socially in ways not seen before because of the abundance and
distribution of aquatic prey, which they refer to as aquatic subsidies,
in the region. In other words, their biological needs are met so they
have energy to burn or play.
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"If there is a lot of food around, there is less of a need to fight over
it," Eriksson said.
Researchers used data from 59 camera stations that were operational
for 8,065 days from 2014 to 2018. Jaguars were detected on 95% of the
cameras. In all, 1,594 videos of jaguars were obtained, representing 69
unique individual animals. The maximum number of unique jaguars captured
by one camera was 15, including nine just in 2015.
"Typically you see an apex predator very infrequently on camera because
they move over really large areas," Eriksson said. "Jaguars were the most
frequently seen mammal on camera -- which is really unusual." Researchers
documented 80 independent social interactions between adult jaguars. Of
those, 85% were between males and females, but 12 were between same-sex
jaguars (one female-to-female interaction and 11 male-to-male.) Two
males even spent 30 minutes in front of the camera playing.
Other authors of the paper are Levi and Joel Ruprecht, both of Oregon
State's Department of Fisheries, Wildlife, and Conservation Sciences
in the College of Agricultural Sciences; Daniel Kantek, Selma Miyazaki
and Ronaldo G. Morato from the Brazilian Instituto Chico Mendes de
Conservac,a~o da Biodiversidade; Manoel dos Santos-Filho from Universidade
do Estado de Mato Grosso, Brazil; and Peres.
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Story Source: Materials provided by Oregon_State_University. Original
written by Sean Nealon.
Note: Content may be edited for style and length.
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Journal Reference:
1. Charlotte E. Eriksson, Daniel L.Z. Kantek, Selma S. Miyazaki,
Ronaldo G.
Morato, Manoel Santos‐Filho, Joel S. Ruprecht, Carlos
A. Peres, Taal Levi. Extensive aquatic subsidies lead to territorial
breakdown and high density of an apex predator. Ecology, 2021;
DOI: 10.1002/ecy.3543
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Link to news story:
https://www.sciencedaily.com/releases/2021/10/211018082343.htm
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