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Arb Notes: Animals in the wintertime

Minnesota winters can be brutal. This is as true for many of the critters which inhabit the arb as it is for us Carleton students. One of the primary challenges that animals face during the winter is an increased threat of starvation.

Cold temperatures necessitate that animals burn more fuel to keep their bodies warm. Moreover, sources of energy are often less abundant during winter time. As trees shed their leaves and prairie grasses get covered with snow, there is substantially less plant biomass available to herbivores. For predators, many of their prey items are hidden away in hibernation or have migrated to warmer climes. And for animals which rely primarily on sight, the reduced daylight hours add an even greater set of challenges. How do animals clear all of these hurdles?

Many skirt these threats by hibernating and significantly lowering their metabolic demands. Others adopt behavioral strategies that are far more interesting than sitting in a catatonic state. Many species of small birds—such as Black Capped Chickadees—will adopt ‘riskier’ foraging strategies during winter. In a set of experiments performed by behavioral biologists, small birds will opt for bird feeders with more variable rewards during cold weather, and will opt for feeders with more consistent rewards during warm weather. What explains this strategy?

These small birds know that if they play it safe their greater energetic demands likely won’t be met. By choosing feeders with more variable rewards, they can increase the chance that they’ll get enough food to stay warm. In other words, during winter, many birds need to truly risk it to get the biscuit.

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