In a video captured by biologists, an aggressive African freshwater tigerfish can be seen jumping out of water to prey upon a swallow in flight.
This time, it is a fish preying on a bird, and not the other way round.
For the first time, biologists have reported Hydrocynus vittatus, a population of African tigerfish found in freshwater, preying on flying barn swallows in Africa's Schroda Dam. And they caught the whole thing on camera.
The biologists, who were there to study the species, reported their observations in the Journal of Fish Biology.
Researchers from the Water Research Group of North West University, South Africa, conducted a 15-day survey of the area, during which they observed as many as 20 successful attempts by tigerfish each day.
The fish displayed two strategies to capture the unladen African swallows. These included surface or sub-surface pursuits, followed by aerial strikes, and direct aerial strikes initiated from deeper water, according to the article published in Journal of Fish Biology.
"The whole action of jumping and catching the swallow in flight happens so incredibly quickly that after we first saw it, it took all of us a while to really fully comprehend what we had just seen," Nico Smit, director of the Unit for Environmental Sciences and Management at North-West University in Potchefstroom, South Africa, told Nature. "The first reaction was one of pure joy, because we realized that we were spectators to something really incredible and unique."
Tigerfish usually feed on other fish, crustaceans and insects. But this "avivorous behavior" is the first confirmed report of a freshwater fish preying on birds in flight, said the team of researchers.
Rumors about such behavior have circulated since the 1940s, Smit said. But he and his team "never really convinced by the anecdotal reports," he added.
Scientists have observed some freshwater fish, such as, eels, piranhas, and pike, occasionally preying on birds. But this behavior involves catching swimming, floating, or stationary birds on land close to the edge of the water, not leaping out of the water and grabbing them mid-flight.
When the team set out to study the migration patterns and habitat of these animals in a South African lake in the Mapungubwe National Park, near the border with Botswana and Zimbabwe, they were not necessarily looking for fish lunging out of the water, according to Nature.
Given the limited study of freshwater fish in Africa, Smith said that he hoped his team's findings "will really focus the attention on the importance of basic freshwater research, and specifically fish behavior."