When you think of a lion, what is the first thing that comes to mind? A catchy song from a Disney movie, their majestic roar, or maybe the similarities between these predators and the housecat curled up on your lap? What perhaps doesn't enter your mind is the swimming prowess of these African beasts. Well, new research has revealed that these big cats might be swimming a whole lot more than we thought. 

In Queen Elizabeth National Park, Uganda there is a pair of lion (Panthera leo) brothers named Jacob and Tibu. The pair are already known to researchers because of 10-year-old Jacob’s incredible life of survival; among other things, his various battle scars have left him with only three legs. 

“I’d bet all my belongings that we are looking at Africa’s most resilient lion: he has been gored by a buffalo, his family was poisoned for lion body part trade, he was caught in a poacher’s snare, and finally lost his leg in another attempted poaching incident where he was caught in a steel trap,” said Dr Alexander Braczkowski, from Griffith University's Centre for Planetary Health and Food Security, in a statement. 

Jacob and Tibu show no sign that their various brushes with death have let that stop them. The latest exploit of the brothers is the subject of new research and shows the pair swimming approximately 1.5 kilometers (0.9 miles) across a river filled with crocodiles and hippos. The pair actually took three attempts to cross on the night the swim was recorded by drone, each time returning to the banks after being trailed by what the team thought was a hippo or a crocodile. 

“His swim, across a channel filled with high densities of hippos and crocodiles, is a record-breaker and is a truly amazing show of resilience in the face of such risk,” Dr Braczkwoski said. 

Previously, lions were known to swim typically less than 100 meters (328 feet). The team estimates that Jacon and Tibu swam 1.1 kilometers (0.6 miles) in linear distance but more likely closer to 1.5 kilometers (0.9 miles) accounting for small changes in direction during the swim. 

Some swims have reportedly ended in death to the lions via crocodile attack. Nile crocodiles (Crocodylus niloticus) can weigh more than four times that of adult male lions, explain the authors. This begs the question of why would the brothers risk swimming so far, given that the Kazinga Channel is so full of dangers. 

"It’s likely the brothers were looking for females,” Dr Braczkowski explained. “Competition for lionesses in the park is fierce and they lost a fight for female affection in the hours leading up to the swim, so it’s likely the duo mounted the risky journey to get to the females on the other side of the channel.”

There is one other way across the river, but the researchers think that human activity deterred the lions from using the small bridge. Filming the epic feat back in February of this year, it's thought the brothers swam across the river six times. The team concluded that the lack of females, fights over territory with other males, and the human presence on the road bridge were the three main driving forces behind the lions' incredible record-breaking swims. 

“Jacob and Tibu’s big swim is another important example that some of our most beloved wildlife species are having to make tough decisions just to find homes and mates in a human-dominated world,” Dr Braczkowski said. 

The paper is published in Ecology and Evolution.