When people live cheek by jowl, moods sour and tempers flare.
Mice react to cramped quarters in a similar way.
But new research has uncovered a more sinister side effect of overpopulation on these masters of high-speed reproduction. Female mice reacting to the stress of chronic overcrowding develop perplexing lesions on their ovaries, report researchers from Binghamton University in New York. Stress can disrupt or even halt ovulation in humans, but the state of the ovaries in these mice was a complete surprise. When wild house mice were allowed to reproduce freely in the lab, the ovaries of two out of seven strains became covered with shapeless white masses of 'amyloid protein' fibres. Similar amyloid fibrils create debilitating plaques in the brains of Alzheimer's patients.