Warming Winters Are Reshaping New Hampshire's Moose Population

State wildlife biologists say New Hampshire's moose population has continued a long, uneven decline linked most directly to winter tick infestations, a parasite whose survival and reproduction is strongly tied to the length and severity of winter. Shorter, milder winters in recent years have allowed tick populations to explode on individual animals, with calves suffering the highest mortality.

Necropsies on moose found dead in late winter frequently reveal tens of thousands of ticks on a single animal, a burden biologists say causes fatal blood loss and hair loss severe enough to leave animals unable to retain body heat even in relatively mild conditions. Adult moose generally survive tick loads that prove fatal to calves, contributing to a population skewed toward older animals.

Wildlife managers have experimented with adjusting hunting permit levels in response to population data, a tool that indirectly affects moose density and, in turn, the ease with which ticks find hosts each fall. Researchers caution that any single management intervention is unlikely to fully offset a challenge ultimately driven by broader climate trends affecting winter length across the region.