El Niño Early Winter - Mammal Impacts
By Gerry Smith
The non winter of much of November-December 2015 is a double edged sword for much of the natural world. Survivorship for many animals is enhanced but lack of snow cover and warm temperatures have their down sides. Many insects were about that should not have been. Ticks remained active, being the bane of all critters coming in contact with them. Mammals such as skunk and opossum were active, using energy that they may not be able to replace. Many amorous male skunks, for example, became road kill when they should have been curled up in a den site. As with all aspects of the natural world, things are complicated and interactions complex.
The primary cause of this mild winter is a Godzilla El Niño in the Pacific Ocean. Whether this natural event has been intensified by climate change is a matter of conjecture. Whatever the cause, the effects on different species vary greatly. The dominant mammal in the region, us, is generally benefited by, and happy with such a winter. With the notable exception of winter sports enthusiasts, most of us have an easier time surviving. The same is true of that other dominant mammal of the region, the white-tailed deer. Winter kill is a major factor in deer mortality and the last two old-fashioned North Country winters caused substantial die-off in some areas. Normally deer retreat to yarding areas in November going to locations with thick cover that helps them survive the winter. By mid-December 2015 there was no evidence of this behavior in most areas. When deer are not concentrated they have access to food resources that enhance their survival. The flip side of this is that high deer numbers have many adverse impacts on natural ecosystems and greater survival only worsens the problem.
Many small mammals benefit much less from a mild winter than larger species. Rodents in particular may be hard hit by predators as their natural bomb shelter, snow cover, is lacking. For example meadow voles can still feed and breed happily under several inches of hard crusted snow while protected from most predators. Even larger species such as snowshoe hare may be at greater risk of predation. A hare whose seasonal molt has given it all white pelage stands out like a sore thumb to a hungry predator in a snowless landscape. These species evolved with fairly predictable effects of climate and weather fluctuations. Significant changes in such a regime would certainly upset the apple cart for many species in our area. As with mammals, birds wintering locally receive both benefits and adverse impacts during mild winters. More on that next time…