Capitol Hill has been ensconced in winter for a few months now. That said, as humans, we have it pretty easy. Not ignoring poverty and homelessness, but generally we can turn up the heat, put on another layer, stay inside, or eat high-calorie foods. Have you ever thought about how Capitol Hill’s wild kingdom copes out there in the elements?
Ultimately this is a diverse topic, even for urban wildlife. The strategies are numerous and fascinating, but for brevity’s sake, let’s focus on a few examples. Generally speaking, most animals handle winter with behavioral or physiological adaptations, often in tandem.
Many mammals tackle winter with only marginal changes. As long as they’ve effective insulation and plenty of calories. Being endothermic, we can create our own heat, but we need fuel for the fire. Most mammalian species frequenting Capitol Hill year-round don’t hibernate; our winters are mild enough that there’s no need. Food is available year-round too (often thanks to people), though in smaller amounts during winter. To survive colder temperatures many simply pack on extra-pounds and grow a winter coat. Ever paid close attention to Eastern gray squirrels (the ones that are everywhere) in winter? They’re chubby, having eaten as much as possible while the getting was good, and wearing a thicker winter coat.
Caching food is a handy behavior that squirrels and other species practice. Many of us have found a peanut buried in the ground or under leaf litter. Hiding food of course allows them to save for harder times. However, one can’t cache all in one place. Another animal, such as a crow, might easily find it by watching repeated visits or a rodent kin might sniff it out. So a squirrel scatters its caches, relying on both spatial memory and smell to retrieve them. In a setting with native species, forgotten or leftover caches are an important part of natural seed dispersal.
Birds, especially corvids (our crows and jays), are extremely good at remembering caches but use spatial memory alone, lacking in a strong sense of smell. Steller’s jays do a tidy job of caching, while also relying on flexible, opportunistic diets year-round. In terms of memory they stand in no comparison to their alpine relative, the Clark’s nutcracker. Studies have shown they have up to a 90% retrieval rate of the thousands of pine nuts they cache, allowing them to survive bleak winters at elevation.
Small, hot bodied Anna’s hummingbirds do surprisingly well in our cool climate. One helpful adaptation is that they can go into torpor every night. Torpor is a period of greatly reduced thermoregulation, only a few vertebrates can achieve. Anna’s hummingbirds drop their temperature from their standard 107 to around 48 degrees nightly. This allows them to greatly decrease the calories their high metabolisms would need, even resting, overnight.
While we aren’t amazingly rich in most terrestrial insects and invertebrates, those around are equally adapted to the temperate zone. Being ectothermic, reliant on external temperatures for thermoregulation and in turn to keep moving and flying, species that overwinter as adults need to hide and effectively “shut down” when winter hits (many go into a prolonged state similar to torpor). Other species time short life-cycles to gestate during the colder months. Eggs are deposited in the ground, in water, and inside plants or hidden amongst leaves or bark, waiting for warmer months to hatch.
The social insects we typically encounter have similar but more complex methods. Queen yellow jackets and bumble bees are typically the only individuals who overwinter, while workers die off, replaced the following year. Transplant, European honey bees don’t create honey for our pleasure. They create it to last the winter, while huddled around their queen in the central chamber of the hive. Most ants simply retreat to ambient temperatures below the surface, with a larder to last the winter.
This is really just the tip of the iceberg in terms of winter adaptations. If you really want to learn more, a good starting place is with Bernd Heinrich’s book Winter World. Snuggle up with it on a nasty day and think about how good you’ve got it (and how helpless we’d be without our big brains).
Previously in Pikes/Pines