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With urbanization expanding into natural areas, it is increasingly important to understand how species subject to human-induced habitat alteration respond to novel opportunities and stressors. A pervasive consequence of urbanization is artificial light at night (ALAN), which previous studies have found introduces both costs and benefits for vertebrates. This understanding, however, primarily reflects findings from laboratory-controlled experiments or comparisons of wild populations in areas with long-standing differences in ALAN regimes. Here, we investigated the short-term costs and benefits for Anolis lizards during the period of initial exposure to ALAN using realistic light levels for urban areas (mean ± SD = 87.9 ± 36.7 lx at a distance of 3 m). As compared to controls, we hypothesized that adding ALAN would result in behavioral and physiological changes over the short term for brown anoles and their arthropod prey. In contrast to predictions, ALAN did not increase arthropod abundance or extend anole activity into the night. Structural habitat and sleep site use changed little in response to ALAN, which exposed about one-third of sleeping anoles in ALAN plots to light at night due to our manipulation. However, this direct light exposure resulted in lizards being more easily roused from sleep compared to lizards sleeping in the dark in control plots or in shadows in ALAN plots. The apparent inability of some anoles to adjust their sleep sites to avoid ALAN exposure may have contributed to their increased responsiveness at night and decreased locomotor endurance in the day. Our study suggests brown anoles can experience higher short-term costs than benefits during initial exposure to ALAN.

Behavioral adjustments may allow organisms to cope with the drastic environmental change caused by urbanization. We compared the escape behavior of Anolis lizards during simulated predator approaches on trees in both urban and forest habitats and on artificial structures (i.e., cement walls and metal posts) in urban areas. We found that urban lizards were less wary on trees, likely due at least in part to habituation to humans. In contrast, lizards on cement walls showed greater wariness, which may reflect a behavioral modification when escaping because of poor locomotor performance on this substrate. In both habitats, lizards modulated escape responses in ways consistent with their performance abilities on the various substrates. Escape by jumping decreased when lizards used wider and more isolated perches, which are characteristic of urban sites. Urban lizards squirreled (i.e., moved to the opposite side of a structure) more on wider trees and metal posts, and sprinted more but never jumped from cement walls. These behavioral responses for predator escape are consistent with the structural habitat changes caused by urbanization. Urban habitats had larger diameter trees, sparser ground vegetation, and many artificial structures. We found that urban lizards showed behavioral modulations because of exposure to humans as well as the locomotor constraints of using some artificial structures, such as cement walls. The ability of urban lizards to alter their escape responses and adjust to novel features of the habitat may be important traits of species able to colonize and persist in urban areas.

Persistence of animals in urban habitats, a stark environmental contrast to natural habitats, can be explained through evaluating the mechanisms behind organism-habitat interactions. One of the most notable effects of urbanization is the change in structural habitat; vegetation is removed and modified, favoring large trees and adding artificial structures in cities, which may alter how organismal preferences for aspects of the habitat are realized. We evaluated the mechanisms by which structural habitat changes associated with urbanization alter the available vegetation and substrates on which two species of Anolis lizards perch in urban and natural forest sites in Miami, FL. We also experimentally assessed habitat preference in the lab to establish the mechanism behind habitat selection. We found that vegetation was broader in urban areas compared to natural habitats, and artificial structures in urban areas were more than twice the diameter of available natural perches. Lizards expressed their preference for broad perches by selecting broader vegetation and artificial structures compared to their availability in both habitats. With the increased availability of broad substrates in urban areas, perch diameters selected by lizards resulted in an expansion of this aspect of the structural habitat niche for both species. The two species differed, however, in other responses to altered urban habitats. Anolis cristatellus tended to avoid artificial substrates, whereas A. sagrei used both natural and artificial structures in proportion to their availabilities. This study provides a mechanistic explanation for how urbanization alters structural habitats, leading to niche expansion for organisms living in cities.

Foraging decisions reflect a trade-off between the benefits of acquiring food and the costs of movement. Changes in the biotic and abiotic environment associated with urbanization can alter this trade-off and modify foraging decisions. We experimentally manipulated foraging opportunities for two Anolis lizard species – the brown anole (A. sagrei) in Florida and the crested anole (A. cristatellus) in Puerto Rico – to assess whether foraging behavior differs between habitats varying in their degree of urbanization. In both urban and natural forest habitats, we measured the latency of perched anoles to feed from an experimental feeding tray. We manipulated perch availability and predator presence, while also taking into account population (e.g., conspecific density) and individual-level factors (e.g., body temperature) to evaluate whether and how these contribute to between-habitat differences in foraging behavior. In both species, urban anoles had longer latencies to feed and lower overall response rates compared to lizards from forests. Urban anoles were also larger (i.e., snout-vent length and mass) in both species and urban A. sagrei were in better body condition than the natural forest population. We postulate that the observed patterns in foraging behavior are driven by differences in perceived predation risk, foraging motivation, or neophobia. Although we are unable to identify the mechanism(s) driving these differences, the substantial differences in urban versus forest anole foraging behavior emphasizes the importance of understanding how urbanization influences animal populations and their persistence in anthropogenically-modified environments.