• Investigation of the Northern Range Expansion of the Virginia Opossum (Didelphis virginians)

      Garneau, Danielle; Gervich, Curt; Romanowicz, Ed; Appling, Leslie (2014)
      The Virginia opossum (Didelphis virginiana) has a very wide geographic range and is found throughout the south and northeastern United States, as far south as Central America and recently a few sightings have been noted in southern Canada. Low temperatures play a significant role in defining the opossum distribution, as they do not forage when temperatures are below 24.8°F. In parts of the opossum range, where they are forced to endure this temperature minimum, many experience increased mortality rates as a result of frostbite due to their small body size and hairless ears and tail. It may also be possible for them to persist in the northern extreme of their range by metabolizing body fat stores during cold winter months. Opossums found further north typically have a thick layer of underfur, which serves a thermoregulatory function. Because the opossum does not hibernate, it must forage year-round; however, this is difficult during the cold winters of upstate, New York. Typically the opossums stop foraging in temperatures less than 24.8°F, and avoid foraging in temperatures below 32°F . The goal of this study was to assess the progression of the northern migration of the opossum using a combination of qualitative roadkill and live sighting survey responses (i.e., bus drivers, mail collectors, Fed Ex drivers, hunters and trappers) and climate trends derived from long-term regional weather station records. We do not predict that sustainable Virginia opossum populations currently reside in high density within our region. Largely, this is because Clinton County is at the northern extent of their range in United States and their thermoregulatory needs cannot be met in these rural habitats. However, warming climate and increases in anthropogenic food sources may be making their northern migration possible in the near future.