Appreciation for the Brown Anole
July 14, 2023
The brown anole is a common sight across both my college campus and across most of Florida, where their scurrying and scuttling make up the background noise to almost any walk in the woods. This small, invasive lizard is often overlooked, but, like so many other common, urban animals, there is a lot of interesting stuff to talk about regarding them. So let’s get started!
A handsome brown anole who came to say hello as I was birdwatching one morning. Those who are genuinely fascinated by wildlife will still be interested in the introduced, common, and, perhaps at first glance, boring. Image by Donovan Snell
The brown anole (Anolis sagrei, named after a famous anarchist journalist) is just one member of the enormous Anolis genus, which consists of several relatively small, diurnal lizards inhabiting the warmer regions of the Americas and Caribbean islands. Traditionally, Anolis contains a massive amount of species, perhaps as many as 425, which would make it the largest amniote genus. However, this high concentration of species has been questioned many times. Several authors have suggested that the genus needs to be massively cut down and reorganized, with some suggestions that there may be as few as 45 true Anolis species. The fossil record, as one would likely expect for small, delicate, primarily arboreal animals, for anoles is scant and does not do much in the way of helping clear things up. As a result, their evolutionary history, which is based primarily on phylogenetic studies, has been interpreted differently by different authors. The anole family, Dactyloidae, diverged from other lizards somewhere around 23 to 95 million years ago (a huge gap, I may add) with a South American origin being most widely accepted. The controversy surrounding the taxonomy and evolution of anoles is something I can’t cover in full in this article but perhaps will be revisited sometime in the future.
So where does the brown anole fit into all of this? A. sagrei’s exact affinities have been called into question on occasion, with Nicholson et al. suggesting that the brown anole is a species complex within their proposed genus Norops alongside over a hundred other species. More concrete than their classification is their habitat. The brown anole is native to Cuba and its surrounding islands, the Bahamas, and the Swan Islands, but due to human activity, they now have a much larger range. They have been introduced to the southern United States, Hawaii, Taiwan, and almost the entirety of the Caribbean. The brown anole is a highly adaptable animal and can be found in a variety of habitats, from salty mangrove forests to city sidewalks. It is consistently stated that the brown anole is more terrestrial than most anole species, preferring to spend more time on the ground or in lower vegetation than in trees. I have observed brown anoles on fairly high branches on a few occasions, but certainly not to the extent that one would expect with how many of them there are. Brown anoles, like most anoles, are primarily diurnal, but, as a testament to their adaptability, many brown anoles in urbanized areas have become more nocturnal to take advantage of insects attracted to artificial lights.
Brown anoles are highly generalist and will take advantage of all kinds of resources, from thin cattails to metal pipes. Images by Donovan Snell
The brown anole, like most anoles, is primarily insectivorous. Their diet consists mostly of smaller insects, spiders, and worms, though they have been known to take on larger prey such as other lizards, including the native green anole as well as smaller members of their own kind. I’ve personally seen a relatively small brown anole trying to kill a large moth, slightly bigger than the lizard himself, by crushing the moth’s head. Another larger anole saw this and came in to try and steal the moth for himself. This led to a twenty-minute back-and-forth over the dying moth (who, at this point, couldn’t fly away due to a shredded wing) until the smaller individual grabbed the moth by the head again and dashed off deeper into the foliage where I couldn’t see the action anymore. The larger one chased quickly behind and I assume their little scuffle continued for some time afterwards. Brown anoles have also occasionally been observed eating plant material such as fruit, but this is possibly more for hydration than for energy intake.
Brown anoles are pretty variable in color. They are also capable of changing color, often becoming darker when they are basking in order to get more heat from the sun. Because of this, you may see brown anoles that are actually more gray or black than brown. Most females and sometimes males have a white or beige stripe running down their backs. Every so often, I notice brown anoles of both sexes with distinct red heads. Information on this color variation is rare, but anecdotally it is reported across Florida and, for whatever reason, appears to be getting more and more common.
Brown anoles can vary a lot in color. At left, a female brown anole with a distinct beige stripe running down her back, alongside some rather intricate patterning. At right, one of these strange “red-headed” brown anoles. Images by Donovan Snell
The male brown anole is larger than the female and has his famous dewlap, a brightly colored flap of skin on his throat that can be extended for use in attracting females and intimidating rivals. The female also possesses a dewlap, though it is far smaller and less noticeable. Calsbeek and Marnocha have observed that male brown anoles display more often from elevated perches instead of simply on the ground. It was also noted that males are more aggressive towards males that are on the same elevation as them and more tolerant of males that were below them. Body size was also directly correlated with perch height, indicating that higher perches are a valuable resource worth fighting over for male brown anoles. Male brown anoles rarely stray far from their perches, even to deal with encroaching rivals. In such high population densities, it seems that maintaining one’s perch as a signal of dominance is more important than scaring away every single rival and potentially losing out on this resource to the hoards of suitors.
A male brown anole displaying his famous dewlap. Image by Donovan Snell.
When fighting does ensue, it can be quite violent and lengthy. The males use their small but still rather sharp teeth to latch onto each other. They will often attempt to throw each other to the ground, especially when on more elevated perches, something I have been fortunate enough to see firsthand on many occasions. One time, I witnessed a male brown anole toss a smaller male off of a branch around thirty or so feet off the ground. The smaller male seemed to be uninjured minus his pride and ran off unscathed.
The sharp teeth of a brown anole at work. Image by Donovan Snell.
In Florida, the mating season for the brown anole is almost all of spring and summer, during which the displays of males are a common sight. Like other anoles, the female brown anole lays just one egg at a time. She will lay an egg once every four to six days, and she will typically lay around 15 or so eggs by the end of the breeding season. Nest construction is a simple matter, as the female will quickly dig a shallow depression in loose soil, lay her egg, and then cover it back up. The simplicity and speed of the process is likely an adaptation to avoid detection of both the mother and egg by predators. Interestingly, it has been experimentally shown that female brown anoles are more likely to lay their eggs near where other females have already laid their eggs as opposed to entirely unused soil.
In their introduced range, brown anoles have become prey for many native predators, including birds, snakes, mammals, and even some larger arthropods such as certain spiders. Predation upon the brown anole is something I have personally seen countless times. Speed and camouflage are their primary defenses but, as a last resort, the brown anole, like many lizards, has a detachable tail that can be used as both an escape method or as a distraction, as the tail continues to twitch around even after removal. The tail will grow back, but typically shorter and duller than it was before.
The poor brown anole is on the menu for plenty of predators. Here are two native predators, a loggerhead shrike (Lanius ludovicianus) and an eastern gray squirrel (Sciurus carolinensis), chowing down on some exotic snacks. Images by Donovan Snell.
The brown anole is likely the oldest and is now one of the most abundant invasive reptile species in the United States. Reports of the brown anole in the Florida Keys can be traced back to the 1880s but it is doubtful that the species was ever established in the mainland United States prior to around 1940. By 2000, the brown anole had been reported in every single county in Florida and continues to expand their range to this day, though they have likely reached some of their temperature-based limits already. The primary proposed reason for their introduction to the U.S. is that they and/or their eggs arrived via cargo from Cuba, in particular, live plants and the soil they were contained in. However, an intentional release of around 100 individuals in Palm Beach County in 1941 is known, and it’s also been proposed that accidental hitchhiking inside vehicles has helped contribute to their expansion northward. Genetic evidence has shown that the brown anole has been introduced from Cuba to Florida at least eight separate times, and their occurrence in overseas locales like Hawaii and Taiwan likely came from Florida stock.
The primary concern surrounding the brown anole’s presence in the United States is its potential impact on the native green anole, an idea that has been tossed around since the 1960s but hasn’t generated much conclusive evidence. The brown anole is a known predator of hatchling green anoles and competes with adults for food, but evidence that they are directly responsible for any decline in green anole populations is scant. What is known more concretely is that brown anoles alter green anole behavior. In the presence of brown anoles, green anoles spend significantly more time in higher branches, presumably as a way of avoiding brown anoles.
The green anole, the only anole native to the United States. Image by Donovan Snell
Overall, the brown anole, despite how common they are, seems to have a lot yet to be discovered about them. Who would have expected so much mystery out of something so seemingly ordinary?
Sources
“Brown Anole.” Savannah River Ecology Laboratory, accessed May 29, 2023, https://srelherp.uga.edu/lizards/anosag.htm
Nicholson, Kirsten E., Brian I. Crother, Craig Guyer, and Jay M. Savage. It is time for a new classification of anoles (Squamata: Dactyloidae). Zootaxa, 2012. https://www.southeastern.edu/acad_research/depts/biol/faculty/pdf/nicholson_et_al2012.pdf
Poe, Steven, et al. A Phylogenetic, Biogeographic, and Taxonomic Study of all Extant Species of Anolis (Squamata: Iguanidae). Systematic Biology, 2017. https://academic.oup.com/sysbio/article/66/5/663/3056323?login=false
“Anolis sagrei.” Indian River Lagoon Species Inventory, accessed May 29, 2023, https://irlspecies.org/taxa/index.php?quicksearchtaxon=Anolis+sagrei&taxon=8957&formsubmit=Search+Terms
Losos, Jonathan. Red-Headed Brown Anole. Anole Annals, 2013. https://www.anoleannals.org/2013/02/10/red-headed-brown-anole/
Calsbeek, Ryan and Erin Marnocha. Context Dependent Territory Defense: The Importance of Habitat Structure in Anolis sagrei. Ethology, 2006. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0310.2006.01194.x
Tokarz, Richard R. Body size as a factor determining dominance in staged agonistic encounters between male brown anoles (Anolis sagrei). Animal Behavior, 1985. https://www.sciencedirect.com/science/article/abs/pii/S0003347285800063
Lee, Julian C. Anolis sagrei in Florida: Phenetics of a Colonizing Species. Copeia, 1985, https://www.jstor.org/stable/1444808
Johnson, Steve A., Courtney Reyes, Brandon Dodge, and Natalie M. Claunch. Florida’s Introduced Reptiles: Brown Anole (Anolis sagrei). UF/IFAS Extension, 2021. https://edis.ifas.ufl.edu/publication/UW486
Dees, Allison, Kayla Wilson, Chanel Reali, Jenna E. Pruett, Joshua M. Hall, Renata Brandt, and Daniel A. Warner. Communal egg-laying behaviour and the consequences of egg aggregation in the brown anole (Anolis sagrei). Animal Behavior, 2020. https://onlinelibrary.wiley.com/doi/abs/10.1111/eth.13028