In a pun-rich turn of events, some Australian catfish have started eating mice.
A study published this month in the Journal of Arid Environments found that lesser salmon catfish in the Ashburton River had been eating Spinifex hopping mice in fairly large portions. Of the fish they sampled, 44 percent were found to have the mice in their stomachs, and of those, mice composed about 95 percent of their stomach content.
This is the first report of Spinifex hopping mice being eaten by any fish, as well as the first report of Australian catfish eating a land-based mammals at a high rate. Previous reports from studies conducted in 2010 and 2014 stated that similar mammals made up only 4 percent of this catfish’s diet.
Catfish will eat anything, but how are they getting these mice?
Scientists were surprised to find evidence that mammals might be much more crucial to the catfish as prey than previously believed, but it’s not in itself odd that a catfish would eat a mouse. One of the paper’s authors, David Morgan, director of the Centre for Fish and Fisheries Research at Murdoch University, clarified to The Verge that catfish are omnivorous and have very non-specific diets.
What is strange is that the scientists don’t know how the catfish are catching and killing these mice at such high rates. Because of their springy hind legs and tails, hopping mice are better than most mammals at avoiding water, and they don’t spend time in water on purpose. And though catfish are far from picky eaters, they’re usually opportunistic hunters — in most cases they eat whatever happens to be floating around.
One 2012 study found evidence that a much larger species of catfish, which had been displaced from its native habitat, had adapted to the situation by learning to beach itself and attack pigeons. Morgan told The Verge that his team hadn’t ruled this out as a possibility and noted that this species of catfish does look for prey that might have wandered into shallow waters at night and is known to eat grasshoppers and other bugs that fall onto the water's surface.
It’s possible that the catfish studied by Morgan and his team have learned some new skills, but right now, the researchers’ best guess is that odd weather in northern Australia at the time of the study (July of last year) gave the catfish a hunting helping hand. Hopping mice live in groups, in interlocking systems of underground burrows. Last year’s extreme summer rainfall may have flooded the burrows and pushed the mice into the river.
another story of ecosystem disruption
Climate projections for northern Australia say that the area is set to experience longer droughts and more dramatic periods of flooding in coming years. While this will make plenty of hopping mice available to the catfish during flood periods, it could also throw river ecosystems of balance and threaten biodiversity. For this reason, the researchers emphasize that further investigation into these seemingly minute changes is urgent.
This story is just one of the many weird ecosystem disruption tales we will undoubtedly hear more and more of as the effects of climate change make themselves felt.