Given a large enough total sample and a wide range of replicates, it is possible to learn a lot about basic stoat biology from simple routine dissections. This survey collected 1599 stoats, plus 40 weasels and 56 ferrets from 14 study areas representing native southern beech (Nothofagaceae) forests, podocarp/broadleaved forests, and tussock grasslands, at both low and high elevations and across latitudes from 38oS to 45oS. We found that stoats can survive injury by inhumane traps or vehicle impacts; they eat whatever they can catch, and survive on large native invertebrates when necessary; their black-tipped tails help them avoid swooping raptor talons; males grow larger than females, especially when well fed as nestlings, and larger males can better fight off rivals while smaller females can be more efficient hunters; stoats in New Zealand have become slightly smaller than their ancestors; fecundity of females (ovulation rate) is fixed a year in advance of littering but fertility (litter size) is finely adjusted to maternal condition by intra-uterine mortality over winter; skull shape and bacula weight reliably change with age; seasonal changes in sex ratio of trap captures is related to the annual cycles of behaviour of individuals; traps set too wide miss many females.