Alexander Braczkowski
On February 4, scientists monitoring lion populations in Uganda captured thermal drone footage at night of two lions — brothers named Jacob and Tibu by the Uganda Wildlife Authority — swimming through the predator-infested Kazinga Channel, which connects two lakes, most likely to find a mate. While there have been previous reports of the lions swimming short distances, Jacob and Tibu covered about 1.5 kilometers (nearly a mile) — the longest swim ever recorded, according to a new paper published in the journal Ecology and Evolution.
“The fact that [Jacob] “The fact that Mr. and his brother Tibu have managed to survive for so long in a national park that has faced significant human pressure and high poaching rates is an achievement in itself – our science has shown that this population has almost halved in just five years,” said co-author Alexander Braczkowski of Griffith University, who has been working with the Ugandan government to monitor the lion population in the area since 2017. “His swim, across a channel teeming with high densities of hippos and crocodiles, is a record-breaker and is a truly astonishing demonstration of resilience in the face of such risks.”
Jacob and Tibu’s impressive feat is likely the result of increased pressure from human encroachment, says Braczkowski, who co-authored a 2020 paper proposing a new census technique that could be used more broadly as an early warning of lion declines. Their method revealed a worrying movement parameter for both males and female lions in Uganda’s Queen Elizabeth National Park, where home ranges increased to 3.27 km (a 400 percent increase) for males and 2.22 km (a 100 percent increase) for females—likely a response to systematic prey depletion through poaching, for example. And the sex ratio was dangerously skewed: one male for every 0.75 females, a highly unusual occurrence.
“In African lions, males already pay a high price for large, impressive sexual displays, taking enormous risks to find mates, establish permanent home ranges, and defend lionesses and their cubs,” Braczkowski et al. wrote in their new paper. “This is likely to be exacerbated when there is limited access to females or significant human pressure.” Hence the record-breaking swim.
Lion brothers Jacob and Tibu braved hippos and crocodiles to make the crossing. Credit: Alexander Braczkowski
Braczkowski et al. believe that Jacob and Tibu were likely searching for available females to mate with. Apparently, they had lost a battle for female affection with other male lions just before their record-breaking swim and decided it was worth trying to find mates on the other side of the canal. There is actually a small bridge connecting the two sides of the canal, but there is a constant human presence (two armed guards) on the bridge, which probably deterred the lions from using it.
Covering the distance
This isn’t the first time Jacob has defied expectations. The lion is something of a local icon, famous for surviving many previous incidents that could have killed a less tough fellow, one of which cost him a leg. Yes, he did make that incredible swim on three legs. “Jacob has had the most incredible journey and is truly a cat with nine lives,” Braczkowski said. “I would bet everything I own that we are looking at the most resilient lion in Africa. He’s been gored by a buffalo, his family has been poisoned for the lion parts trade, he’s been caught in a poacher’s trap and finally lost his leg in another poaching attempt where he was caught in a steel trap.”
Evidence for lions' ability to swim long distances has been scarce, but the authors observed the behavior in lions on six other occasions in the past year in western Uganda. They also conducted an extensive online search for other examples. One peer-reviewed paper suggested that lions could cross the Kwa-Kasaii and Congo rivers, but provided no hard evidence. The authors did find a report of an adult male crossing the 100-meter-wide Zambezi from northern Zimbabwe to Zambia in 2012, as well as several YouTube videos of male African lions making short swims back and forth across the Okavango Delta.
Although African lions are known to occasionally hunt crocodiles and hippos on the coast, they are much more vulnerable in the water. However, “data such as these indicate that lions, where motivation is sufficient, can cross large rivers, often seen as barriers to connectivity between existing lion populations,” the authors wrote, despite the high risk of injury or death.
Ecology and Evolution, 2024. DOI: 10.1002/ece3.11597 (About DOIs).
