When Heat Pumps Become Killing Machines

Heat pumps have been a boon for efficient residential heating and cooling, at least in those regions of the country where winter temperatures do not consistently hover in the frigid range. In the southern United States, whole house heat pumps are arguably the most efficient way to heat and cool a house. Outside temperatures rarely fall below twenty degrees Fahrenheit, and even at 20°F, there is plenty of ambient heat available to heat a well-insulated home.

Owners of heat pumps have probably noticed that in the summer, heat removed from the home is released into the outside air. Heat coming off the outdoor unit, the actual heat pump, is hot. On the other hand, they may not have ventured out on a winter night to see how cold the exhaust from a heat pump is when it is in “heat” mode. But cold it has to be. Compared to a temperature of absolute zero, winter air is hot as hades. A heat pumps works by extracting some of that heat and sending it into the house to warm the house occupants.

But you can’t get something for nothing. Once the pump extracts a portion of the heat from cold outside air, that outside air must become colder.

Into this thermodynamic saga enters a non-native lizard called the Cuban or Brown Anole. The lizards are invasive, which means they are decimating the native Green Anoles which have long existed in the South Eastern United States. The Cubans are larger, more aggressive than the Greens, and reportedly feed on young Green Anoles. 

Cuban Brown Anole [Anolis sagrei]

However, they have a weakness. As you might expect for any species originating in Cuba and the Bahamas, they don’t like the cold. Whereas Green anoles range as far north as the Carolinas, the Browns do not. In fact, after a cold night in the Florida Panhandle I found a Brown Anole hard frozen on my doorstep. Perhaps he sensed warmth seeping from under the front door, and was trying to get in the house. Well, he didn’t make it.

The Greens, on the other hand, apparently shelter on or underground in leafy areas to survive the occasional cold dip.

This image has an empty alt attribute; its file name is Anole-Green-cropped.jpg
Green Anole (Anolis carolinensis)

As the outside temperature begins to drop in the late fall and winter, heat-seeking tropical lizards can be found warming themselves on top of the outdoor heat exchanger of our AC unit. When the proverbial nip is in the air, owners of well-insulated Florida homes plagued with high humidity, continue to run their air conditioning until late in the season.

For the Anoles, that is both a boon and a risk; it can prove to be a dangerous warming strategy. If frightened by the sudden appearance of a homeowner, Anoles run. When in their panic they fall into the running fan, the attempted evasion does not end well.

But the greatest insult is a thermodynamic one, which comes when the outside temperature drops even lower. Naturally, that chill makes the warmth from the heat exchanger even more attractive to the lizards. That is, until one of the human occupants decides it’s time to turn on the heat.

Thermodynamics being what it is, that switch almost instantaneously turns a warming source of air from the AC unit into a frigid blast of air.

Which explains why one morning after turning on the heat, I discovered the freeze-dried carcass of a Brown Anole clutching tightly to the grill of the AC unit. Apparently, the already chilled tropical lizard had what little strength it had left suddenly sapped by the high velocity blast of cold air. It died in place. (I have spared you the photo I took at the time.)

There is a moral to this story I believe.

As we grow cozy with new technology we don’t understand, while basking in the warmth and seduction of advanced engineering with its seemingly miraculous capabilities, perhaps we should remember this little lizard. It had acquainted itself with the bright side of thermodynamics, without realizing there was a dark side. Likewise, with the throwing of a switch, seemingly magical technology could be our undoing.

A serving of Artificial Intelligence, anyone?

The Immigrants in My Backyard

I admit it; I have long been angry at the immigrants living in my backyard.

When I moved my family back to Florida over twenty years ago, I was thrilled by the sight of the beautiful green anoles (lizards) scampering over the white stucco walls of our house.

Green Anole, from Wikimedia Commons.

But over the years the native green lizards have all but disappeared, replaced by the drab brown lizards which immigrated somehow from Cuba and the Bahamas.

We can’t get Cuban rum or Cuban cigars, but we have Cuban lizards. How did that happen?

Anyway, it is a well proven scientific fact (see pages 12-28 of the linked publication) that when Cuban brown lizards move into a territory, the Green lizard population plummets. Part of the reason is because the larger brown lizards eat the young of native Green Anoles. That alone is enough to make me angry with them; although human anger is better directed towards human atrocities than against instinctive animal behavior. I know that, as a scientist, but still there is the annoyance I cannot quench at the loss of the Greens who, after all, belong here.

One particularly cold morning when the temperature had uncharacteristically dropped to 20° F overnight, I found a Brown Cuban Anole had crawled up to our front porch, trying, I suppose, to get as close to the house’s heat as possible. And there he lay, stiff and dead.

I actually rejoiced in the immigrant’s vulnerability. I remember thinking, “Bet it doesn’t get this cold in Cuba, does it? See, you should have stayed;” as if that frozen lizard had a choice in the matter.

As a matter of curiosity, and definitely not sympathy, I moved his stiff body out on the sidewalk where the warming sun rays were beginning to fall. I was thinking perhaps the local cats would like their lizard breakfast with the chill taken off it.

Imagine my surprise when I found 20 minutes later that the lizard was moving, and a few minutes after that, had managed to scurry off into the garden. Well, you have to admire toughness; and who doesn’t enjoy a surprise?

In the past couple of weeks these little guys’ toughness and their surprising lack of fear has helped me to appreciate these invaders, just a bit.

He’s hard to see; a good survival strategy.

I have been pushing my physical limits digging drainage trenches through root infested sandy soil. Much to my surprise, the Brown Cubans have been watching me, closely. Apparently my disturbance of the ground stirs up insects and small worms which the Anoles then feed upon with lightning quick forays into the digging zone.

What surprised me, however, is just how close they approach the digging. The most extreme example of lizard fearlessness was when I used a string trimmer to mow down ground-cover so I could uncover an outdoor sump pump. A Brown Cuban was hanging upside down on the stucco wall of the house, barely a foot away, with clippings from the cutter flinging at high speed into the wall where the lizard remained still but vigilant. He was completely unperturbed by the machine noise and the constant barrage of vine debris. Tough little critter, I thought. photo (36)

Apparently, he had only one thing in mind;  the prospect for the sudden appearance of food stirred up by the string trimmer.

During another phase of the project, what seemed like the same large Anole perched himself on any high elevation available so he could watch my digging. Every once in a while he would hop down into the disturbed dirt to snag a morsel, seeming unconcerned by the fact that a steel shovel was working the earth.

On one occasion he ran 18 inches or so right up to my foot to snag some insect I had failed to see. At the foot of the giant —  yes, that little guy was fearless.

The Foreman lizard, keeping a watchful eye on my work.

OK, I had to admit, no Green Anole had ever done that before.

As I continued to work one hot Saturday, covered in sweat, I began to enjoy my constant companion. So much so that I picked up a camera and started taking photos of him, without the flash of course. I didn’t want to blind him.

On one shot the flash went off unexpectedly just inches from his face. He bolted. After 10 minutes or so, when he was nowhere to be seen, I actually felt bad, thinking that I’d scared him, or worse, blinded him. Yes, I know it was strange, that the Brown immigrant hater, me, actually felt remorse for my carelessness with the camera.

Finally, after another 30 minutes or so, he showed up again, as if nothing had happened. And with that, I felt forgiven.

Obviously, my hard attitude towards these immigrants has softened. The more time I spend with them, the more I appreciate their positive qualities: fearlessness, willingness to appreciate me as a food provider. They are in a word, opportunistic. And that, I believe, gives them  an advantage over the more timid native Green Anoles.

As for the Cubans feeding on the natives? Well, they get as good as they give. Neighborhood house cats, who are certainly not native either, feed nightly on the Cubans. I cringe when I watch a cat flip an Anole, of any color, into the air and down it head first in a single gulp. That is the way of nature, and the fact that I like it or not has no influence at all on the outcome.











You’re Not a Mad Dog – So You Must Be an Englishman


Snowy school bus stop. Photo credit: Cathy Griffin.










Running in Hades heat



I do not understand it.


