Palm trees at sunset. Photo by D. Sillman
(Click on the following link to listen to an audio version of this blog … Bats and Alligators
One evening, we were sitting out on the porch of our beach house watching the silhouettes of the palm trees slowly fade against the pink and orange sunset sky. There were a few mosquitoes, but they seemed to only be biting Marian. She must have the gift of long-chain aldehydes and the just the right carboxylic acids in her skin secretions to attract mosquitoes even when very few of them are out and about(see Signs of Winter 2, December 8, 2022). The rest of us, unbitten and unbothered, thanked her for keeping the rest of us unbothered and unbiten!
Anyway, most of us were sitting there in the deepening darkness very comfortable and totally unpunctured, when, suddenly, something flitted over the back lawn. Then it went past again! Then several more “somethings” darted past making impossible twists and turns and zig-zags across the sky. Bats!
In the dim light it was very hard to see anything more than the outlines and sizes of the bats. They were larger than the little brown bats (Myotis lucifugus) we used to watch on the summer evenings back in Pennsylvania but definitely smaller than the big brown bats (Eptesicus fuscus) we regularly see on summer nights in Colorado.
Velvety free-tailed bat. Drawing by A. D. d’Orbigny. Public Domain
The i-Naturalist website lists five species of bats that have been recently seen in the Florida Keys (the velvety free-tailed bat (Molossus molussus), the northern yellow bat (Lasiurus intermedius), the Jamaican fruit eating bat (Artibeus jamaicensus), the buffy flower bat (Erophylla sezekorni) and the evening bat (Nyeticeius humeralis).
The two species on this list that are in between the size ranges of the little brown and the big brown bat (little brown (0.18 to 0.49 oz body weight, 8.74 to 10.59 inch wingspan), big brown (0.4 to 0.8 oz body weight, 13 to 14 inch wingspan) are the velvety free-tailed bat and the evening bat (both about 0.4 oz body weight and 10 to 11 inch wingspans). These two species, though have very different flight behaviors and very different typical roosting habitats. The evening bat is described as a “slow, steady flyer” and a “true forest species” that roosts primarily in hollow trees. The velvety free-tailed bat, on the other hand, is a very fast flyer that roosts, in the Keys, at least, almost exclusively in human-constructed buildings and houses.
Based on the speed and agility of the bats we observed, and also on the lack of nearby forests, I assume that we were watching velvety free-tailed bats.
There are admittedly, not that many bats in the Florida Keys. In fact, it used to be said that there were no bats here, although that is patently not true. In 1929, a local fishing lodge owner and entrepreneur named Richter Clyde Perky decided that the environment of the Keys would be greatly improved if there were fewer mosquitoes swarming the exposed, available, blood sources of good, money-spending tourists! So Mr. Perky researched the topic and decide to build a large bat house and establish a population of bats in the Lower Keys.
Photo by Ebyabe. Wikimedia Commons.
He built his monumental, 30 foot tall bat house on Sugarloaf Key about 13 miles north of Key West and named it the Sugarloaf Bat Tower. Allegedly, he spent $10,000 on its construction (that is the 2022 equivalent of $163,000!). It instantly became a local landmark and a tourist attraction and, eventually, was added to the National Registry of Historical Places (in 1982). The Bat Tower had slatted walls to allow bats easy access and egress and an internal cleaning system to remove the accumulations of bat feces and urine. The Bat Tower, though, never did get any bats! Crates of bats (the exact species were not recorded) were brought in and released into the Tower. Specialized “bat bait” attractants (exact formula not divulged but in the heat of the Keys its odor was astonishing!) were added to the interior of the Tower, but the bats just flew away.
Osprey used the top of the Tower for a nesting site, and it is rumored that the Skunk Ape (the Florida Keys version of Big Foot) used the Tower as a hideout. No bats, though, ever lived there.
The Tower was destroyed by Hurricane Irma in 2017.
The velvety free-tailed bat emigrated to the Keys in the 1990’s possibly from the Greater or Lesser Antilles or Central America. It has adapted itself to the human-modified habitat of the Keys very well and is doing the job of mosquito control for free that Mr. Perky was willing to put up a small fortune to get accomplished!
Manatee with calf. Photo by G. Rathbun, USFWS. Public Domain
There were two animals we really wanted to see on our trip to Florida: manatees and alligators. We never did get a glimpse of a manatee, although we searched hopefully through lots of seagrass beds, but we did find alligators the day we drove up to The Everglades. Along the hiking trail we took out from the parking area at the park office was a magnificent, eight or nine foot long alligator just resting and chilling in a wet depression! Later we saw another, even bigger one, further down the trail.
Photo by L. Drake
We kept a respectful distance from the alligators, but one couple that was standing with us did get closer than I felt was comfortable. The husband was trying to get his wife to kneel down next to the alligator so that he could take their picture. She was not excited about the idea and kept refusing. They were still arguing about it 45 minutes later when we came back along the trail on our way to our car. The alligator, in spite of all of the noise and clamor, had not moved an inch!
The American alligator was once found in wetlands and lakes from Texas, all across the Gulf states, up the U.S. Atlantic coast as far north as North Carolina. Freshwater and brackish water, and open and marshy habitats were occupied by this apex predator. By 1967, though, primarily due to widespread, uncontrolled hunting, the numbers of wild American alligators were so low that the species was teetering on extinction. Placement of the species on the endangered species list in 1967 and the passage of the full Endangered Species Act in 1973 provided sufficient protection to allow the American alligator to recover and to re-inhabit much of its former natural range. There are even alligators now in the bayous of my old hometown of Houston!
Photo by J. Hamilton
Why are alligators important? First and foremost, they are predators. They broadly and opportunistically take almost any prey species that come available. They especially consume relatively large prey species that live in their aquatic habitats (especially large fish), and they also take a wide range of terrestrial species that wade or swim across their aquatic habitats or come to the edge of their pools, ponds or streams to drink. American alligators have been known to eat black bears, panthers, deer and wild boar but more commonly capture and eat smaller terrestrial prey like raccoons and muskrats. As we talked about in a blog a few weeks ago, alligators also developed a taste for exotic, invasive nutrias (see Signs of Winter 3, December 22, 2022) much to the alligators’ benefit and the nutrias’ misfortune. Wading birds may also be taken but they are not a typical part of an alligator’s diet. Control of these prey species is a very important ecological role of the American alligator.
American alligator. Photo by D. DeLoach. Wikimedia Commons
One very interesting “unintended consequence” of the extirpation of the American alligator from wetlands in Florida (which was motivated in part at least to stop the alligator consumption of game fish) was the precipitous drop in game fish populations. Researchers determined that the alligators preferentially consumed the very largest fish (like gars), and that these gars primarily ate game fish. Without the alligator control of the gar population, game fish numbers drastically declined.
American alligators also construct “gator holes” or “gator ponds” in their wetland habitats. The alligator uses its snout and tail to dig down through the accumulated muck and vegetation to create a relatively deep water pool in which it can hide and hunt. These pools fill up with freshwater and are often the only water sources that persist during times of drought. Many animals rely on these gator holes for drinking water during times of low rainfall (although they have to keep an eye out for lurking alligators!).
Everglades hammock. Photo by D. Sillman
Female American alligators also modify their wetland habitats via the construction of nesting mounds. These mounds can be as much as 3.5 feet high and up to 7 feet wide. These mounds serve not only as incubation sites for the alligator eggs but can also can significantly add to the topographic complexity of the wetland habitat. A variety of plant species that require slightly drier soils can grow on these mounds thus increasing the vegetative diversity of the wetland. Also, a significant number of bird and mammal species use these mounds for their own nests and dens. Looking out across the wet, grassy plain of the Everglades we could see many “hardwood hammocks” scattered about. Some of these isolated, wooded mini-islands may have started as alligator nesting mounds which then accumulated organic debris and sediments and steadily grew into their final, wooded forms.
Pizzo on Housecat Day 2023! Photo by D. Sillman
Housecat Day Update! I took my cat Pizo out the back door and put her down on the snow-covered patio. It was a sunny, cold afternoon, but she wandered all over the patio (even walking boldly across the snow!) and showed no intention of running back into the house. Pizo’s prediction: Spring is right around the corner! (please note: she is not looking at her shadow!)