A study has found that road collisions can remove nearly a third of a hedgehog population each year, posing a particular threat to already small groups. Researchers say the findings matter because even one or two deaths can seriously weaken populations with fewer than 15 animals, increasing their risk of local extinction.

Nottingham Trent University researchers studied four Nottinghamshire populations over 520 miles (838km) of survey routes. Traffic collisions accounted for about two fifths of recorded deaths and killed 15% to 29% of each group annually; larger populations were more resilient because of higher reproduction and because most road deaths were male. Britain’s rural hedgehog populations are estimated to have fallen by 30% to 75% since 2000, and conservationists recommend improving habitat and creating fence or wall gaps known as “hedgehog highways”.