Stomach contents reveal the lesser salmon catfish of Australia favors a diet of small mammals.
Mice have been turning up in large quantities in the bellies of lesser salmon catfish, according to a study in the Journal of Arid Environments.
A survey of 18 lesser salmon catfish from Ashburton River in Australia revealed that nearly half of the fish had mice at various stages of digestion in their stomachs. Insects, crustaceans and plants, which were previously thought to constitute their primary food source, were found to be supplemental to their main diet of native spinifex hopping mice.
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The larger wels catfish have been observed beaching themselves to capture pigeons on land, but until now, predation on land animals was considered a rare occurrence in the lesser salmon catfish.
Hopping mice don’t normally spend time in the water, though they do construct deep burrow systems in the sand of riverbanks.
“These mice often live in small colonies within a single burrow system,” study lead author Erin Kelly of the Centre for Fish and Fisheries Research at Murdoch University, Perth, tells New Scientist, “so collapse or flooding of one or multiple burrow systems along the Ashburton river could have inadvertently introduced them into the water.”
As Kelly points out in a press release, “Both species are nocturnal, and it is also possible that the catfish are actively hunting mice on the riverbank.”
Although it remains unknown just how the catfish are gaining access to the mice, their dietary shift may reflect changing food availability in response to extreme cycles of drought and flooding in their river habitat.
"Understanding whether species like the lesser salmon catfish can adapt to their changing environment, and how the successful ones do it, will help us to conserve these creatures," Kelly says.
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