CATS MAY EAT GRASS TO CLEAR HAIRBALLS, LIKE UNCLOGGING A DRAIN

Cat owners are no strangers to the odd and sometimes unpleasant behaviours of their feline companions — like finding surprise hairballs or catching them snacking on grass or houseplants. While these habits may seem unrelated (or just plain strange), a new study suggests they might be closely connected.

Researchers from High Point University in North Carolina, writing in the Journal of Veterinary Behaviour, propose that cats may be using grass as a natural tool to help eject hairballs. The idea? The rough, jagged edges of certain grasses can physically entangle strands of fur, making it easier for cats to cough them up — like unclogging a drain.

A Closer Look at Hairballs

To test this theory, scientists collected hairballs from two indoor–outdoor cats and examined them using high-resolution scanning electron microscopy. They discovered sharp plant structures — including tiny, spike-like projections called trichomes — tightly interwoven with fur.

These microscopic plant features, invisible to the naked eye, were surprisingly effective at snagging cat hairs, which are 2 to 20 times wider than the structures themselves. The arrangement was strikingly similar to how some commercial pet foods use added fiber to reduce hairballs.

More Than Just Nutrition

It’s long been believed that cats, like other wild animals, eat plants not for nutrition but for self-medication. Studies have shown wolves passing parasites wrapped in grass, and some primates choosing specific plants to rid themselves of intestinal worms. In cats, the assumption has been that grass helps purge parasites — but the High Point team found little evidence of this in their samples.

Parasites like roundworms and tapeworms are far too large to be physically trapped by the grass’s microstructures. What researchers did find, however, was consistent plant matter — mostly from common backyard grasses and hardy houseplants like spiderwort — with rough surfaces perfectly suited to snare hair.

In every sample, fur was visibly tangled with plant fibers, suggesting cats may be instinctively selecting plants with the ideal texture for this purpose.

What About Dogs?

While the findings support the idea that grass helps cats manage hairballs, some questions remain. For instance, if grass is mainly a tool for hairball control, why do dogs — who rarely suffer from hairballs — also eat it?

To explore further, the researchers are now shifting their attention to the other end of the digestive tract. They’re collecting their cats’ poop for future experiments to see whether grass also helps move hair through the system rather than out the mouth.

Nature’s Self-Care Routine?

In the end, this study adds to growing evidence that animals use plants in complex, purposeful ways — far beyond food. For cats, eating grass may not be a quirky, gross habit after all, but a clever biological solution to a grooming problem they can’t otherwise solve.