As the old adage has it, cleanliness is next to godliness, but it also has sinister consequences for lab rats: they are much more likely to cannibalise their young if their cages are frequently cleaned.

Charlotte Burn at the University of Oxford and Georgia Mason at the University of Guelph in Ontario, Canada, found that nearly twice as many pups were eaten in cages cleaned twice a week as in those cleaned fortnightly (Applied Animal Behaviour Science, DOI: 10.1016/j.applanim.2008.02.005). Cannibalism was most likely if the cages were cleaned soon after the pups were born.

Burn notes that cannibalism in …