Jaguar Smashes Record for the Species’ Longest Recorded Swim, Baffling Scientists

Despite what they say about cats and water, jaguars are powerful swimmers. These predators rarely stray from the rivers and wetlands that permeate their rainforest habitat, and they readily dive in to hunt for prey.

Usually, these dips are relatively brief: Until now, the farthest jaguar swim on record was just 656 feet (200 meters). But now, scientists have observed a jaguar in Brazil smashing that record as if they were a feline Michael Phelps, with the big cat seemingly paddling for more than a mile across an artificial lake. This is the first time we’ve seen a jaguar swim such a distance, and it raises fresh questions about how to best protect this threatened species.

An unprecedented journey

In a preliminary paper posted September 10 on the preprint server BioRxiv, Brazillian researchers reported that camera traps around the Serra da Mesa hydropower reservoir in Central Brazil had captured images of an adult male jaguar on the northern shore of the reservoir in May 2020. More than four years after that initial sighting, he was seen again, this time by a camera trap on a small island within the reservoir.

An analysis of the jaguar’s spots found a total match between both sightings, confirming that the researchers were looking at the same individual seen in 2020. And to get to the island, he would have had no choice but to swim. The researchers used geodesic analysis to identify two possible routes he could have taken: A direct 1.54 mi (2.48 km) swim, or a 1.45 mi (2.33 km) swim with a stop about midway through on an islet, before continuing to the island.

Because the researchers couldn’t pinpoint exactly where the jaguar entered the water on the mainland, they made a conservative estimate based on the shortest possible distance he had to swim between the islet and the island—about 0.79 mi (1.27 km). This distance alone is nearly six times longer than the longest jaguar swim ever verified before.

Jaguar habitat increasingly fragmented

This kind of long-distance swim by a large, terrestrial carnivore is believed to be exceedingly rate, the researchers noted, and this case offers a rare opportunity to study whether jaguars have the ability to move into new territories via water. That’s crucial for conservation, as their habitat is being fragmented by deforestation and other human-driven pressures, so understanding what limits there may be on their movement is important.

Experts have long thought hydropower reservoirs like the Serra da Mesa to be a potential barrier. Hydropower development has already inundated more than 9,800 square miles (25,400 square kilometers) of jaguar habitat, transforming the rainforest into archipelagos, according to the researchers. But how this change had constrained jaguar habitat wasn’t well understood.

The team’s findings suggest that the permeability of these manmade aquatic barriers depends on several factors, including water temperature, boat traffic, and the presence of islets. The study is preliminary and not peer-reviewed, so the results need to be validated. Still, the context they could provide is critical to jaguar conservation efforts, which have so far primarily focused on connecting pockets of suitable habitat to enable the cats to fan out, promoting gene flow between populations, and ensuring the long-term survival of the species.

“​​These insights have direct relevance for hydropower impact assessments and corridor planning, highlighting that the strategic retention of riparian habitat and placement of steppingstone islets can sustain landscape permeability for wide-ranging carnivores,” the researchers concluded.