Catfish learning to hunt pigeons on land (VIDEO)
A European catfish moves in to attack a group of pigeons. (YouTube/Discover Magazine)In an unusual development that researchers are calling evidence of adaptive behavior, some catfish have taken to jumping on land to hunt live pigeons.
Discover Magazine's Ed Yong writes, "These particular catfish have taken to lunging out of the water, grabbing a pigeon, and then wriggling back into the water to swallow their prey. In the process, they temporarily strand themselves on land for a few seconds."
Researchers captured video of the European catfish, which reside in the River Tarn in southwestern France. In the footage, several of the fish, which range in length from 3 to nearly 5 feet, are seen thrusting their bodies from the shallow banks onto land where they capture pigeons and drag them back into the water.
Some dolphins and killer whales have exhibited similar behavior, though both are mammals and better equipped to survive on land for brief periods of time.
Still, Julien Cucherousset from Paul Sabatier University in Toulouse has taken to describing the catfish as "freshwater killer whales."
The study results were published in the scientific journal Plos One. The study's abstract notes:
"Among a total of 45 beaching behaviors observed and filmed, 28% were successful in bird capture. … Since this extreme behavior has not been reported in the native range of the species, our results suggest that some individuals in introduced predator populations may adapt their behavior to forage on novel prey in new environments, leading to behavioral and trophic specialization to actively cross the water-land interface."
Watch the video of the catfish hunting the pigeons:Alerted to the fishes’ behaviour by local fishermen, Cucherousset watched them from a bridge overlooking the island. Over the summer of 2011, he filmed 54 attacks, of which 28 percent were successful.
Catfish get their name for the long, sensitive whiskers (or ‘barbels’) on their upper jaws, and the Tarn fishes would erect theirs when they were hunting pigeons. This, combined with the fact that only moving pigeons were ever attacked, suggests that the fish are sensing the vibrations of birds that approached the water.
Chucherousset collected samples of the catfish, as well as the three animals that they eat—pigeons, crayfish, and smaller fish. All of these prey have different levels of carbon and nitrogen in their bodies, and Chucherousset used these to show that individual catfish varied in whether they hunted pigeons, and those that did ate fewer fish.
For the moment, this stands as an interesting example of unusual behaviour. Chucherousset doesn’t know why these particular catfish started stranding themselves to kill pigeons, or whether they particularly benefit from doing so.
The European catfish is an alien, introduced into the Tarn in 1983, and currently flourishing there. Is it possible that these invaders have eaten too many local fish and are forced to seek sustenance elsewhere? Does this explain why it seems to be the smaller catfish that go after pigeons? Or is it that the smaller individuals are less likely to be permanently stranded on shore, or expend less energy in wiggling back into the water? Why, essentially, is a bird in the mouth worth being a fish out of water?
Reference: Cucherousset, Bouletreau, Azemar, Compin, Guillaume & Santoul. 2012. ‘‘Freshwater Killer Whales’’: Beaching Behavior of an Alien Fish to Hunt Land Birds. PLOS ONE http://dx.doi.org/10.1371/journal.pone.0050840
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