The Virginia opossum (Didelphis virginiana) is North America’s only marsupial. Unlike many native mammals, this species has not evolved the physiological mechanisms for a deep, sustained winter dormancy. Winter poses a profound challenge to the opossum, forcing it to constantly balance the need to conserve body heat with the necessity of finding food. This ongoing struggle shapes the animal’s behavior, dictating its movement, its choice of shelter, and its overall chances of making it through the season.
Winter Strategy: Activity Versus Hibernation
Opossums do not undergo true hibernation, which is a state of deep, prolonged inactivity characterized by a massive drop in body temperature and metabolic rate. Instead, their survival strategy involves remaining active, though they significantly reduce their movements during the coldest periods. When ambient temperatures drop, especially below freezing, the opossum will enter short, intermittent bouts of torpor. This shallow metabolic slowdown helps conserve energy for a few hours or days. Because of this limited energy-saving capacity, the opossum must regularly emerge from its den to forage and replenish its reserves.
Shelter and Den Selection
To manage the energy demands of winter, the opossum prioritizes finding safe, well-insulated shelter. They are highly opportunistic and nomadic, rarely staying in the same location for more than a few days, making them reliant on pre-existing structures. Opossums do not dig their own burrows, instead utilizing abandoned dens created by other animals or natural cavities. Common winter hideaways include hollow logs, rock crevices, and sheltered spaces beneath tree roots or dense brush piles. They frequently move into human-created environments like sheds or under decks, seeking the thermal buffer these locations provide. The opossum uses its prehensile tail to carry dry leaves and grasses back to the den, creating a warm lining for insulation.
Foraging and Energy Reserves
Before winter arrives, opossums attempt to build up a layer of subcutaneous fat, though this reserve is modest compared to true hibernators. This fat is metabolized to fuel their basic survival needs during periods when they are forced to shelter indoors by severe weather. However, this energy store is insufficient for months of inactivity, necessitating continued foraging. Their diet shifts dramatically in the winter from insects and fresh produce to a more scavenging-focused approach due to the scarcity of natural foods. Opossums become reliant on carrion, which is often easier to locate than live prey. They also scavenge for nuts, frozen fruits, and human-associated waste like discarded food scraps and accessible pet food left outdoors. Foraging trips are strongly linked to temperature, with animals typically avoiding travel when the night temperature drops below approximately -4°C, as the energy expenditure outweighs the potential gain.
Physical Vulnerabilities to Extreme Cold
Despite their thick fur coat, the opossum possesses several physical features that make it susceptible to cold-related injuries. Their ears, tail, and toes are largely hairless, leaving these extremities exposed to freezing temperatures. This lack of protective fur and fat makes them highly vulnerable to frostbite during prolonged exposure outside the den. Frostbite is a common issue for this species, often resulting in the loss of ear tips or sections of the tail. The tail, which is used to carry nesting materials and for balance, can be compromised if too much is lost to injury. The frequent sighting of opossums with shortened tails or notched ears serves as a visible record of their struggle to survive prior winters.