A. sagrei

Brown Anole

Appearance: Anolis sagrei may not be the most colorful or strikingly patterned anole, but owing to its widespread distribution and high abundance it may the anole most familiar to you. Adults commonly grow to 7-8 inches from head to tail with females being a few inches smaller than males. Their body color ranges from light tan to gray to dark brown, almost black. Unlike green anoles that can turn brown, these guys are never green! Males have red-orange dewlaps, sometimes with a yellow border or blotches. Females often have a pattern with diamonds, bars, or a stripe running down their back. When in south Florida don’t confuse brown anoles with crested anoles (Anolis cristatellus). Crested anole females only have a cream-colored stripe on their backs, and brown anoles do not have a light ring around the eye or a light stripe above their front limb. Brown anoles often have two dark bars above their eyes.

Ecology and Habitat: The brown anole is a trunk-ground habitat specialist or ecomorph. They are often found on the ground or perching low on tree trunks (up to 1.5 m high). Brown anoles have relatively long limbs for their body size, which allows them to run fast on the ground and tree trunks that they typically occupy. Brown anoles are usually sit-and-wait foragers, keying in on the movement of prey to jump from their perch and attack. Their diet consists of a wide variety of arthropods including most any spiders and insects they can fit in mouths. They will occasionally eat other invertebrates and small vertebrates including their own hatchlings. Brown anoles primarily occupy disturbed and edge habitats in both natural and human-modified landscapes. Their abundances suggest they are just as at home in the city as in natural areas. Like tourists at the beach, these guys love the sun – they are often active during the hottest parts of the day. All anole species display, but brown anoles are the champions – they are often seen fanning their brightly colored dewlaps, and doing head-bobs and push-ups with the intensity and stamina of an Olympic athlete.

Geographic Range and Biogeography: The native range of the brown anole includes the Bahamas, Belize, Cuba, Cayman Brac, Little Cayman, Swan Island and the Gulf of Mexico/Caribbean coast of Mexico. Its evolutionary origin as part of the 15-species sagrei group is Cuba with multiple colonization events to Caribbean islands east and west of Cuba to round out its native range. One of the best natural colonizers of all anoles, brown anoles are also the undisputed champion of recent human-mediated introductions. Non-native populations are well established around the world including the southeastern United States (e.g. Alabama, Florida, Georgia, Texas), Atlantic islands (e.g. Ascension, Bermuda), Caribbean islands (e.g. Grand Cayman, Grenada, Jamaica, St. Vincent), and Pacific islands (e.g. Hawaii, Taiwan), among other locations with reports of new introductions every year. Genetic analyses reveal multiple origins of these introduced populations from numerous localities in Cuba as well as the Bahamas and Belize. A key discovery about these introductions is that genetic variation from these multiple native-range sources mixes within non-native populations, resulting in increased genetic variation compared to native-range populations.

Research Highlights:

If Anolis carolinensis (green anole) is the “lab rat” of the reptile world, then Anolis sagrei is undoubtedly the “field rat.” This species has been studied extensively in the field from populations on small islands in the Bahamas to the heart of the city in Miami. A well-studied natural history, high local abundance, and the ability to tag individuals for unique identification make this species ideal for field studies of natural selection. We have learned that natural selection acts on morphological, physiological and behavioral traits of brown anoles. For example, natural selection favors longer hindlimbs in the presence of terrestrial predators (curly-tailed lizards, Leiocephalus carinatus) and higher optimal performance temperatures in warmer habitats. Other studies show adaptive responses of limbs to local vegetation after being introduced to new islands. A recent study by Oriol Lapiedra and colleagues evaluated whether natural selection acts on variation in risk-taking behavior of brown anoles when they occupy small islands with and without the ground predator Leiocephalus carinatus. Brown anoles that avoided the ground in lab trials were favored in the presence of the predator, whereas more exploratory brown anoles survived better in the absence of the predator. Moreover, selection on behavior and morphology acted independently. This experiment is among the best studies yet showing that natural selection acts on behavior.

AA post: https://www.anoleannals.org/2017/06/27/evolution-2017-it-doesnt-pay-to-be-risky-when-predators-are-about/

Brown anoles are also a key species in studies of the consequences of global environmental change, including biological invasions, climate change, and urbanization. Recent studies of non-native brown anoles in Miami by Jason Kolbe and his lab discovered that brown anoles living in the city have consistently different personalities compared to their forest counterparts – city lizards are more tolerant of humans, less aggressive, more exploratory in new environments, and bolder after simulated predator attacks. Cities also dramatically alter the ecological niche space occupied by brown anoles. Urban heat islands produce warmer microclimates that allow brown anoles to more often attain their preferred body temperatures during the summer in Miami, likely increasing their ability to persist in some areas. Brown anoles prefer to perch on broad substrates like tree trunks, and urbanization typically results in the removal of smaller trees and the addition of broad diameter artificial structures, such as light posts and utility poles. This leads brown anoles to use broader perches in urban areas despite the fact these artificial substrates are often quite smooth and lizards slip and fall when using them.

Video: https://www.anoleannals.org/2016/09/08/lizards-running-and-slipping-in-ultra-slo-mo/