African tigerfish catch swallows in flight
African tigerfish have been filmed by scientists catching swallows in flight.
Some species of fish are known to feed on stationary birds but experts say this is the first evidence of one catching birds on the wing.
Tigerfish are a predatory freshwater species that are best known for their large, razor-sharp teeth.
The behaviour was filmed at Schroda Dam, a man-made lake in Limpopo Province, South Africa.
Researchers from the Water Research Group of North West University, South Africa, described their findings in the Journal of Fish Biology.
Predators in the water
"The African tigerfish is one of the most amazing freshwater species in the world," said Prof Nico Smit, co-author of the study.
"It is a striking fish with beautiful markings on the body, bright red fins and vicious teeth."
The fish, Hydrocynus vittatus, is known as a voracious predator and according to Prof Smit, its characteristic jump makes it a favourite species for freshwater anglers.
It is a protected species in South Africa and Prof Smit and colleagues were conducting a study into how it uses different habitats in Schroda Dam.
Using radio tags to monitor the movements of individual fish, researchers found that they primarily fed on other fishes at dawn and dusk and withdrew to rest in deep, sheltered areas during the day.
But during a summer survey, the team recorded some unusual activity. The tigerfish swam out to open water in the mid-morning and were seen preying on swallows as they skimmed over the lake's surface.
Prof Smit said the team were "extremely surprised" by the behaviour which they were able to capture on film.
In the past, anecdotal evidence of birds disappearing as they flew over African lakes and pools has suggested that fish could be catching them for food but nothing conclusive had been recorded.
Bass, eels, piranhas and pike have all been acknowledged as freshwater species that prey on birds floating on the surface of the water or by the water's edge, but Prof Smit says this is the first record of freshwater fish catching birds in flight.
He suggested that the findings will change how scientists think about how energy transfers in freshwater eco-systems - and may also have implications for swallow conservation in the country.