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Sunday, August 20, 2023

Cooling Conduct


Eastern Ringtail dragonflies obelisking

The unrelenting heat this summer has affected all living creatures, and while humans can escape into air-conditioned spaces, wildlife needs to rely on other ways to regulate their body temperature.  Often this is accomplished through different types of behavioral strategies acquired through adaptation, and some may seem quite odd until you understand the dynamics at work.

One of the most obvious behaviors (for humans at least), is sweating.  But many creatures don’t have sweat glands, or only sweat from their feet (like some canines), so they rely on panting instead.  In panting, animals breathe rapidly and shallowly with their mouths open, thereby increasing evaporation from the surfaces of their mouths.  This evaporation removes heat and acts as a cooling mechanism.  Panting is used by most mammals (like dogs) and many species of birds. While panting is effective at removing heat, dehydration is a risk so a nearby water source is important.  Birds may also spread their wings and body feathers to allow heat to dispel, and they have an elaborate breathing system that includes air sacs (in addition to lungs) to help them get rid of excess heat through panting.

A molting Northern Cardinal, panting and spreading its wings to cool down

Some birds, such as some species of vultures and storks, will voluntarily defecate on their legs to cool down.  Since bird poop is mostly liquid, it works by having an evaporative cooling effect, much like sweating.  As the poop dries on the bird’s legs, the heat is carried away and it brings down their body temperature.  Pelicans, herons, doves, owls, quail, and nighthawks, can employ gular fluttering, vibrating the muscles and bones in the throat and exposing moist throat membranes to the air, which helps regulate temperature by increasing evaporation.

Insects, like most all creatures, can also maintain a stable body temperature in at least a portion of their bodies through some interesting behavioral means.  While many insects need some heat to warm up their flying muscles, many will adjust/reduce their activity levels or seek out shady spots to handle extreme heat.  Dragonflies, for example, will often obelisk while perched in the midday hot sun, or point the tip of their abdomen directly up at the sun.  It is believed that this behavior reduces the heating effect by reducing the amount of surface area exposed directly to the sun’s rays.

Checkered Setwing exhibiting obelisking as a cooling behavior

When temperatures soar, four-legged animals such as squirrels, marmots, rabbits, bears, and even dogs and cats will lie flat on their stomachs on a cooler surface with their arms and legs stretched out from their bodies.  This behavior is called splooting, and it is thought that since their bellies have less fur and lots of blood vessels, they can dissipate the heat and absorb some of the coolness from the surface.  Also known as frogging or pancaking, splooting can take on various forms: the full sploot (all four legs out), the classic sploot (one leg tucked underneath the body while the other is kicked back), the side sploot (one leg tucked under the body and the other kicked out to the side), and the reverse sploot or toolps (when the animal lays on its back with its legs in the air)!

Fox Squirrel in a full sploot on our back porch

Regardless of the method, we all have to find some form of cooling conduct that allows us to survive until temperatures fall and (hopefully) the rains begin once again.