Friend or Foe: The Relationship between the Northern Curly Tail and Florida's Green Anole

Please note, this article is part of multipart series published that will be published periodically.

Part 2

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Most species of Curly Tails (Leiocephalae), and in particular the Northern Curly Tail, (L. carinatus) have an opportunistic diet.[1] Curly-tailed lizards, while known predators of smaller lizards, especially anoles, do not pose a threat to the native Green Anole because they limit their predation to the invasive, nonnative, Brown Anole.[2] This component of the Northern Curly Tail’s diet may actually benefit Florida’s Green Anole by reducing the population of Brown Anoles.

How? The Brown Anole has a history of displacing Florida’s Green Anole. Both the Green and the Brown anoles are arboreal, or tree dwelling, while our subject, the Northern Curly Tail is terrestrial and lives on the ground. An extensive body of research legitimizes the phenomena of displacement. When the Brown Anole is introduced into the Green Anole’s habitat, the Green Anole is pushed higher into the tree canopy. The effect of this displacement is two-fold. Green Anoles may appear scarcer because they are less visible when dwelling higher in the canopy. Secondly, Green Anoles are at an increased risk of predation by a large, territorial and solitary goliath – the non-indigenous Knight Anole (Anolis equestris).

On the sunny Caribbean islands, the ancestral home of both the Anole and Curly Tail lizards, a similar phenomenon of displacement has been observed. Anoles were driving other Anole species higher into the trees.  Meanwhile, on the east coast of Florida, nestled in a long, wide, remote and shallow estuary (where the river meets the sea) 50-year-old man-made islands are clustered together, creating an ideal environment for further research into this phenomenon. These man-made islands are known as spoil islands and are one of the least developed regions on the east coast of Florida.[3] Here, in Mosquito Lagoon, Dr. Todd Campbell, a vertebrate ecologist with a special interest in the amphibians and reptiles of the Southeast, and an associate professor at the University of Tampa, conducted an incredible experiment. Campbell, whose research interests include how introduced species interact with their environments, “documented [the] precipitous declines in green anole densities following the experimental introduction of brown anoles.” [4]

Indian River Spoil Islands near Vero Beach, Florida

In Florida, USA, herpetofaunal (amphibians and reptiles) population declines have been documented and largely attributed to habitat change or loss and the influence of nonindigenous species[5] Competition for limited resources and displacement harm the Green Anole. As the Brown Anole population expands, the Green Anole population declines, and the survivors shift their perch height, utilizing different habitats than they did prior to the introduction of the Brown Anole.[6]

The displacement of the Green Anole is so significant that in 2017, after Hurricane Irma devastated upper levels of tree canopy “Miami herpetologist Steven Whitfield  reported . . . seeing “more green anoles in the past two days than I have in the two months before that.[7]” Interestingly, this is a juxtaposition of the Northern Curly Tail lizard’s situation, where the lizard may appear more populous because it inhabits areas where humans frequent. Furthermore, ecologists have long suspected that negative interactions, such as competition, are responsible for driving different species into different microhabitats, with subsequent morphological adaptation to these microhabitats over evolutionary time.[8] Thus, not only has the Green Anole population declined as the invasive Brown Anole population booms but there is an irreversible evolutionary effect on the species. Green Anoles in Florida have developed larger toe pads to facilitate life higher in the tree canopy.[9]

Growing up to 16 inches in length, with powerful jaws and teeth, the Cuban Knight Anole inhabits the uppermost canopy of trees, earning it the title of “Crown Giant Ecomorph.” Should this aggressive lizard encounter the Green Anole as the native lizard is forced into the voracious Cuban Knight Anole’s domain by  Brown Anoles, our native anole does not stand a chance.  Unlike the Northern Curly Tail, the Cuban Knight Anole is dangerous to the Green Anoles not because of its greater size and strength, but because the Cuban Knight Anole is a different class of  opportunistic eater, one that will eat the Green Anole.

Cuban Knight Anole. Photo by Sean Giery

In 2017, Sean Giery, a postdoc in the Department of Ecology and Evolutionary Biology at the University of Connecticut, when examining the stomach contents of the Cuban Knight Anoles found evidence for vertebrate prey in the form of a 1 cm section of green anole tail.[10] It is important to note, however, that the larger the lizard, the more it relies on supplemental nutrition from plant matter. Schoener et al. (1982) and Cooper & Vitt (2002) found that larger lizards are more likely to consume plant matter than smaller lizards, perhaps because of the greater caloric needs associated with larger body size.

But biology is not the only factor in determining a species success. In a 2018 article titled Risk and Reward: Lizards Demonstrate Role of Natural Selection in Shaping Behavior by David Slipher, scientists released anoles onto islands to record patterns in natural selection when a top predator was introduced. What they found was surprising. In environments where the Northern Curly Tail was present, Brown Anoles who displayed behavioral traits of increased risk taking had a higher likelihood of survival than their counterparts and controls.

Elegance

The svelte, jewel toned, Green Anole is a pretty lizard. It moves slowly and intentionally, like its doppelgänger the Chameleon.[11] Its bright pink dewlap contrasts with a brilliant green coloring and gives a tropical aesthetic that the invasive Brown Anole does not. It appears small and sympathetic, especially compared to the Northern Curly Tail which is a grim shade of dirty grey reminiscent of crumbling communist housing in Eastern Europe. The grubby stout body, short face, and hideous scampering run of the Northern Curly Tail give it the appearance of a schoolyard bully. But the Northern Curly Tail may be the Green Anoles closest ally. The Northern Curly Tail lizard’s predation on the Brown Anole could theoretically mitigate the adverse effects of the Brown Anole on Green Anole populations. By reducing the Brown Anole numbers, which displace Green Anoles, the Northern Curly Tail might help Green Anoles maintain their natural habitat. Consequently, this reduction could prevent Green Anoles from being forced into the territory of the more aggressive Cuban Knight Anole. If enough Brown Anoles were consumed by Northern Curly Tail lizards, it could enhance the Green Anole’s ability to thrive in its preferred environment, reducing interactions with the Cuban Knight Anole. 

The Northern Curly Tail, decaying communist housing, and an ai rendition of a schoolyard bully.

[11] Green Anoles are commonly but erroneously referred to as “chameleons” because of their ability to change color. https://www.britannica.com/animal/green-anole 

Do you think the Northern Curly Tail lizard is unfairly judged as a negative influence on Florida's native flora and fauna?

• Yes
• No
• Undecided

Citations

[1] Henderson & Powell 2009).

[2] e.g., Schoener et al. 2002

[3] https://floridadep.gov/rcp/aquatic-preserve/locations/mosquito-lagoon-aquatic-preserve

[4] Kamath, Ambika. “Are Brown Anoles in Florida Really Driving Green Anoles to Extinction?” Anole Annals, 10 June 2015, www.anoleannals.org/2015/06/10/are-brown-anoles-in-florida-really-driving-green-anoles-toextinction/#:~:text=But%20it’s%20also%20certainly%20possible,their%20ancestral%20trunk%2Dcrown%20niche. 

[5] Cassani JR, Croshaw DA, Bozzo J, Brooks B, Everham EM, III, Ceilley DW, et al. (2015) Herpetofaunal Community Change in Multiple Habitats after Fifteen Years in a Southwest Florida Preserve, USA. PLoS ONE 10(5): e0125845. doi:10.1371/journal.pone.0125845

[6] Campbell, Todd S., "Analyses of the Effects of an Exotic Lizard (Anolis sagrei) on a Native Lizard (Anolis carolinensis) in Florida, Using Islands as Experimental Units. " PhD diss., University of Tennessee, 2000. https://trace.tennessee.edu/utk_graddiss/4722

[7] Kamath, Ambika. “Are Brown Anoles in Florida Really Driving Green Anoles to Extinction III: A Post-Irma Update.” Anole Annals, 15 September, 2017.  https://www.anoleannals.org/2017/09/15/are-brown-anoles-in-florida-really-driving-green-anoles-to-extinction-iii-a-post-irma-update/

[8] Kamath, Ambika. “Rapid Evolution in Anolis Carolinensis Following the Invasion of Anolis Sagrei.” Anole Annals, 4 Nov. 2014, www.anoleannals.org/2014/10/25/rapid-evolution-in-anolis-carolinensis-following-the-invasion-of-anolis-sagrei/. 

[9] Brooks, John. “The Green Anole: A Comprehensive Guide.” Wild Explained, 14 September, 2023. https://wildexplained.com/animal-encyclopedia/the-green-anole-a-comprehensive-guide/

[10] Giery, Sean.  “Knight Anoles Eat Fruit and Pass Viable Seeds,” Anole Annals, 21 June 2017, https://www.anoleannals.org/2017/06/21/knight-anoles-eat-fruit-and-pass-viable-seeds/

Additional links:

https://biology.ucdavis.edu/news/risk-and-reward-lizards-demonstrate-role-natural-selection-shaping-behavior

https://www.anoleannals.org/2015/06/10/are-brown-anoles-in-florida-really-driving-green-anoles-to extinction/#:~:text=But%20it's%20also%20certainly%20possible,their%20ancestral%20trunk%2Dcrown%20niche.

Kamath, Ambika. “Are Brown Anoles in Florida Really Driving Green Anoles to Extinction?” Anole Annals, 10 June 2015, www.anoleannals.org/2015/06/10/are-brown-anoles-in-florida-really-driving-green-anoles-to-extinction/#:~:text=But%20it’s%20also%20certainly%20possible,their%20ancestral%20trunk%2Dcrown%20niche.