Heat Effects

The midwestern United States is experiencing a heat dome this week.  This is the result of a high pressure system hundreds of miles across and moving very slowly.  Air in the upper atmosphere of a heat dome is already warm, but is still cooler than the air below, and cooler sir sinks towards the Earth’s surface.  As the air moves downward, it compresses air molecules together releasing heat, making the lower layers even hotter and drying out the area as moisture evaporates.  With little or no moisture, no clouds form to relieve the heat and dry conditions.

Humans have a variety of ways to cope with high heat including being less active, drinking plenty of fluids, and remaining in shady or air-conditioned areas.  Wildlife still has to get food and water every day and may have fewer opportunities available to them to avoid the high heat.  Let’s look at how the heat is affecting a few of the backyard species common in the Midwest.

Fireflies are cold-blooded, or ectothermic, and prefer warm and humid areas.  They come out in the early evening and as their bodies warm, they become more active, flying and flashing more frequently, communicating with other fireflies to find a mate.  Eggs are laid soon after mating, but these will perish if they do not remain hydrated.  Turning off outdoor lighting for a few hours in the evening and maintaining taller, well-watered vegetation will help fireflies during hot and dry conditions.

^{American Toad by Brad Carlson, Mar 2012; and Bullfrog at Waterfall Place by DonArnold, 2022}

Frogs and toads are also ectothermic and require heat from the environment to live.  Species worldwide, including American toads and bullfrogs in our area, find temperatures in the 70s to be ideal.  As temperatures move into the mid-80s, these species and others are prone to dehydration and heat stress.  In addition, they normally look for shady and humid areas to regulate their body temperatures, but the lack of moisture in a heat dome does not make those niches easy to locate.  Maintaining shady, well-watered areas of the garden provides refuge for many amphibian species.

Birds are often affected by extreme heat.  Most birds have lower body temperatures than the outside air.  This allows birds to easily dissipate heat from high energy activities, such as flight.  Once the outside air gets above a hundred degrees, birds cannot lose heat to the atmosphere and become severely compromised by heat and dehydration.  Rapid open-mouthed breathing, changing eating times to early or late in the day, sitting with wings outstretched, or exhibiting poor balance are all signs of heat stress in birds.  Providing shady, undisturbed areas and readily available water sources gives birds the opportunity to move around less and stay hydrated.

Wild animals have to deal with weather extremes just as we do.  Come to the Jurica-Suchy Nature Museum or a nature center near you to learn more about providing opportunities for wildlife to survive heat, drought, and other environmental conditions.