Iguanas plummeting to the ground in Miami is an indelible winter in Florida image.
What happens to all of the other semi-tropical creatures when it gets cold? Where do the alligators go in chilly weather? Are there cold weather shelters for manatees?
There are, to a degree, cold weather shelters for manatees. Hot springs, water shallows, and the warm effluent released by older power plants are refuges for them. Manatees will huddle together for warmth since they’re vulnerable to temperatures 68 degrees and lower. Even though manatees are endotherms, which means they regulate their body temperature internally, cold water wicks warmth away from their bodies. Unlike other marine mammals, they don’t have blubber to insulate them.
Fun manatee fact: manatees’ teeth are created in the back of their mouth and rotate to the front, gaining a centimeter a month. The front teeth grind down comparatively quickly and fall out as the teeth from the back move to replace them.
Literally cold blooded
Brumation, torpor, diapause, and hibernation are all types of dormancy, when a creature slows its bodily functions dramatically. These differ from sleeping because brain activity also primarily shuts down. Hibernation in endotherms, or warm-blooded animals, usually lasts for a longer period of time. The animals have stored up fat and rely on it through their hibernation period.
Cold-blooded creatures don’t eat before they go into brumation, because their bodies can’t process the food. Instead they may wake up if it is a warm day and soak up some sun. Then head back to their lairs when the temperature drops. Their body temperature drops radically as well.
There is one other type of dormancy – estivation. Estivation is the warm weather version. Creatures will slow down their metabolism when it is hot and dry and food or water is hard to find.
Alligators are ectotherms (cold-blooded) and have different strategies for cold weather. They stay dormant through cold weather, sinking to their burrows near the water’s edge and brumate.
They stop eating when temperatures go below 70° F (21° C) and start brumation when it’s brisk even for Florida-fied humans, below 55° F (13° C). Alligators can wake up and get some sun if it warms up, and then go back to literally chilling out.
Fun alligator fact: alligators are more closely related to birds than to reptiles, sharing dinosaur ancestors.
About those chilled lizards
The ubiquitous lizards of Florida, from iguanas to anoles to skunks, are not cold weather fans. Videos of iguanas falling to the ground during a Miami cold snap in January 2020 circulated around the world. It led to an interesting discovery by tropical lizard researcher James Stroud. Surviving the cold permanently changed the lizards.
“While there was great variation in temperature tolerance before the cold event — some, like the large-bodied brown basilisk, were very intolerant of low temperatures, while others like the Puerto Rican crested anole were more robust — we observed that all species could now tolerate, on average, the same lowest temperature,” wrote Straud.
The change in cold tolerance seems permanent, and now researchers are studying to see if it gets passed along to the lizards’ offspring. Iguanas and other lizards plummet down because as they get cold, they lose their ability to grip branches and stay in their safe places.
Fun lizard fact: geckos have tiny hairs on their toes which help them climb up walls and other smooth surfaces.
C’mon to my house!
Gopher tortoises are winter heroes. During storms and cold weather, gopher tortoise burrows serve as a Noah’s Ark to their neighbors. They can shelter 360 different species.
Snakes, coyotes, rodents, skunks, owls, and other animals hunker down in the burrows, which may be 50 feet long. The tortoises are ectotherms, and slow their activity in winter months, from October to April, sometimes sunning on the apron (think patio) of their burrow.
“The gopher tortoise is a keystone species, so we can’t just focus on the gopher tortoise itself,’ says Lara Milligan, a Natural Resources Agent with UF/IFAS Extension Pinellas County. “We have to focus on all of the other species that the gopher tortoise helps to basically survive.”
Another type of turtle is vulnerable to the cold. Sea turtles in the panhandle part of Florida get cold-stunned, or go into shock, when water temperatures drop below 50° F (10° C). If the sea turtles are in shallow water when a cold front passes through, they may not have the time or energy to swim back into the warmer waters of the Gulf of Mexico.
Fun turtle (gopher tortoise is a subspecies of turtle) fact: Turtles use cloacal respiration, which is the nice way of saying they breathe through their butt.
During warm weather, Floridians are serenaded nightly by crickets and frogs. When it gets cold, silence falls. Where do those noisy neighbors go?
Wood frogs burrow into the ground, leaves, or wood. Aquatic frogs will bury themselves in water and freeze – not to death – just until it gets warm again. Though ice crystals form inside frogs’ bodies, important organs are protected by an influx of glucose as the frogs become dormant. The frogs absorb enough oxygen to survive through their skin from the water.
Crickets are even more extreme, shutting their entire system down. As it starts getting colder, crickets enter diapause. Diapause seems like science fiction – every cell shuts down and stops growing. Crickets, like frogs, are regulated by hormones as cold weather approaches. Amino acids and glucose act like antifreeze, protecting tissue, until it is warm again.
Raccoons and possums, two other common nocturnal animals, don’t hibernate during cold weather in Florida. They may grow thicker fur, and relocate to warmer places, such as our attics or garages. They might go into a torpor state, a deep sleep or stillness, if they are in a safe place and it is extremely cold. Possums’ tails are susceptible to frostbite and falling off.
It’s lovely to see the White Pelicans arrive for the winter season and float just off shore. What about our resident Brown Pelican? The ones that live in the northern part of the state can get frostbite in their pouches or feet, or suffer from starvation or hyperthermia in extremely cold weather.
Brown Pelicans aren’t migratory like their cousins, but will travel to warmer temperatures by following their prey, Pelicans and other waterfowl coat their feathers with oil secreted from their preen glands, which helps keep their feathers waterproof. As long as the oil isn’t stripped off by chemicals in the water, the birds can stay warm by floating on water that is warmer than the air temperature.
Fun pelican fact: Pelican Island was the first designated National Wildlife Refuge, named so by President Theodore Roosevelt in 1903.
Florida may be known for sunshine and warmth, but it sometimes gets chilly for all of the residents. Be careful if you are out in nature in the cold. There might be a critter in a dormant state that could suffer from being disturbed. The state’s Fish and Wildlife Conservation Commission’s website is a fantastic source for information.