Posted: May 1, 2011, 5 a.m. EDT
Ferret Shaymus/© Courtesy Helena Hansen
One way that ferrets try to cool down when it's too hot is by sleeping more.
Hardly a year goes by without the loss of a ferret due to hyperthermia. Hyperthermia occurs when a ferret has too high a body temperature, and it can be a deadly problem in the summer heat. I was particularly impacted by such a possibility last year when my air conditioner gave up the ghost at the beginning of a particularly nasty heat wave. Outdoor temperatures went into the 90s, while indoors, the temps were several degrees higher. The ferrets could not wait for me to repair the unit, so I had to do something immediately to keep them cool.
How Ferrets Keep Cool Naturally
The best way for a ferret to keep its cool is to allow them to use their own innate behaviors to accomplish the task; behaviors forged over millions of years of polecat evolution. Polecats and black-footed ferrets typically live in areas that freeze in winter and swelter in summer. Yet, polecats and ferrets lack significant numbers of sweat glands and other physiological adaptations that heat-tolerant animals seem to possess. So, how do they survive?
Simple — they go underground. Any spelunker can tell you that caves are warm in winter and cool in summer. If deep and protected, the cave interior is the yearly average temperature for the local environment. So, if the summer highs are 110 degrees Fahrenheit and the winter lows are -20 degrees Fahrenheit, the yearly average could be a stable 60 degrees. That makes the cave cozy in winter and cool in summer. A deep burrow acts similar to a cave in that regard. Neither polecats nor black-footed ferrets hibernate, yet they survive harsh, cold winters and sweltering summers quite nicely, snug in a cozy little burrow.
Ferrets also overcome heat by limiting movement as much as possible, abstaining from most play and exploration. Using muscles requires burning calories, which creates heat. Humans sweat to prevent overheating, but ferrets lack appreciable numbers of sweat glands. Hot ferrets tend to limit exercise as much as possible, turning into pathetic furry slugs, slithering across the floor in slow motion.
Hot ferrets frequently cool down by going prone. You have no doubt seen your ferret imitating a speed bump after strenuous play. They go prone on the floor, flattening as much of their body as possible to cool down. This ingenious behavior is a cooling mechanism that works on basic principles of thermodynamics. It is why a tile floor feels cool to your feet even though it is the same comfortable temperature as your room. Your feet are hotter than the floor, so heat flows from your feet into the tile, creating a sensory feeling of coolness. It is why a hot skillet cooks an egg; heat flows from the frying pan into your breakfast. Called “heat conduction,” it is the flow of thermal energy from an object with high temperature to one of lower temperature in the attempt to reach equilibrium. In the wild, a shallow pit in the earth, a shady rock, and muddy wallows are favored for conductive cooling. Water can speed heat loss, so ferrets might soak in a water dish or lounge in urine to cool off; a damp litter box is a favorite spot to lose heat.
Panting is a common method to lower body temperature. Simply put, as cooler-than-body-temperature air crosses the tongue and oral tissues and enters the lungs, heat transfers from blood to the air, helping cool the body. The degree of panting can be used as a rough estimate of heat stress: the more frantic the panting, the more stressed. If panting stops and the ferret is still obviously overheated, it is in serious trouble.
Another method to keep cool is to abstain from food. Food digestion generates heat, and so heat-stressed ferrets usually eat less. Ferrets will drink more water if available. This replaces moisture lost thought panting, but because water is generally cooler than the body core, it directly cools as well. It also increases urination, which also helps to drain heat from the body.
Another behavioral heat adaptation is sleeping. Ferrets will not only decrease their activity levels when heat-stressed, but tend to sleep longer and nap more. Metabolic rates are slower when sleeping and muscles are not working as much, so there is less body heat for the ferret to lose.