by Whit Gibbons

January 28, 2018

Q: I have a question concerning cold weather and insects. I have always assumed that once the temperature drops below 45 or 50 degrees all insects went dormant. However, during the last cold snap I saw insects flying past my outdoor camera at night with the temperature at 26 degrees. The low for the night was 14 degrees in my yard. As I type this, my camera is on and the temp is 28 degrees, and I see insects flying around. My question is what insects are active at such cold temperatures?

A: The question is intriguing in two ways, the first being, what are the insects? But a second aspect that I find equally interesting is, why don’t more people inquire about these nighttime, cold-weather flying insects? In fact, I have never before been asked this question. The answer to the second question is that most people out in the cold at night are not really paying attention to flying bugs, or if they do see one flitting by, they mark the observation up to an exception and move on. The wildlife camera provided an opportunity to observe the phenomenon closely.

Anyway, the most likely insects you have seen flying on cold winter nights belong to the family of owlet moths. Certain members are known to be active at subfreezing temperatures. Rather than spending the cold months in an egg or larval stage underground or shielded from the elements inside of a log, these small moths remain active as adults in winter. Two mechanisms keep them from freezing. They are able to shiver to create body heat. Although we associate shivering with exposure to cold, such behavior is uncommon in insects, the most notable exception being honeybees that cluster together to warm up the hive. A second trait of winter moths is their ability to store heat in their body by reducing blood flow to the more exposed head and abdomen and retaining warmer blood in the thorax.

Q: Recently, you wrote about the Arctic fox in Iceland. I am curious about something: What do the foxes eat? And what did they eat before people inhabited the island?

A: As I noted in that earlier column, Arctic foxes are native land mammals in Iceland. And many natural food sources are available including seabirds, fish and invertebrates along the shorelines. They will readily scavenge the carcasses of marine mammals that wash ashore and have been documented to attack and kill seal pups. Once Iceland was colonized by people, invasive species including rats, rabbits and mink ultimately became established and are now fair game for foxes.

Humans intentionally brought along some other additions to the Icelandic buffet for foxes—sheep and chickens. Foxes are universally viewed by farmers as predators on livestock. According to a reliable reference, “Walker’s Mammals of the World,” “In Iceland the Arctic fox is persecuted because of its reputed depredations on sheep and lambs. Legislation there has promoted its destruction since at least as early as A. D. 1295.” That’s a lot of centuries to try to get rid of a perceived pest that probably does not eat nearly as many lambs or chickens as people think.

In addition to a wide array of natural and human-introduced food sources, Arctic foxes have a variety of adaptations that allow them to weather harsh winters when food may be scarce. From summer to winter they have an increase in “fur depth of nearly 200 percent” and have a “short muzzle, ears, and legs and a short, rounded body,” all of which serve to reduce heat loss. They can even reduce their metabolism up to 50 percent to wait out extended periods of limited food. Another cold weather adaptation is a circulatory system mechanism that sends warm blood to the pads of their feet in winter. My guess is that the little foxes of Iceland will be around for a long time to come.

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