Date of Award
Master of Science in Biological and Environmental Sciences (MSBES)
Jason L. Kolbe
As the human population increases, urban areas are expanding and bringing humans and wildlife into close proximity. Disturbance by humans can lead to changes in animal behavior and ecological interactions. Urban areas also provide access to novel, artificial substrates (e.g., cement walls and metal posts), which may influence the behavior of organisms. We studied whether urban habitats and artificial substrates influenced escape and foraging behavior of the Puerto Rican Crested Anole (Anolis cristatellus).
We tested whether lizards in urban environments reduced flight initiation distance (i.e., the distance between the observer and the lizard when the lizard begins escape) in response to differences between the natural habitat and whether flight distance differed between urban and natural habitats. We found that flight initiation distance was significantly shorter in urban environments as compared to forest habitats. Flight distance did not differ between habitats. The proportion of escape modes used varied between the habitats. Urban lizards escaped more frequently by squirreling around the perch and reduced the frequency of jumping. Use of larger perches with less vegetation nearby in urban areas was consistent with our results of lizard's squirreling more and jumping less during escape. Our results show differences in lizard flight initiation and escape mode employed between the urban and natural habitats. Habituation to the presence of humans and/or lower predation risk could account for differences in FID. Moreover, habitat differences in urban areas influence the escape mode used by lizards through the increased availability of larger perches and the reduction of perches to which lizards can jump.
We tested differences in latency to feed between urban and forest environments and in the presence or absence of a life-like model of a lizard predator. We found that lizards in the forest habitat foraged more frequently and faster compared to lizards in the urban area. Lizards did not respond to the presence of the model predator in either habitat. Because lizards are visual predators, the lack of movement of our model predator likely reduced the perceived threat to lizards. We also evaluated the effect of conspecific lizards on latency to feed and found that when conspecifics approach the feeding tray, focal lizards reacted less often in the forest habitat. Because the food resources provided was limited, conspecific lizards often exhausted the food resource in our experimental trials, which eliminated the opportunity for focal lizards to feed. Our results show that forest lizards foraged faster and potentially competed more with conspecifics for food resources.
Both studies show clear differences in behavior between lizards in urban and forest habitats. More work is needed to assess whether these differences are due to behavioral flexibility and/or evolutionary adaptation to human-modified environments. Regardless, differences in behavior found in this study suggests that habitat modifications due to human activities, such as urbanization, may be a potent force impacting the ecology and evolutionary trajectory of these populations.
Aviles-Rodriguez, Kevin J., "DO URBAN ENVIRONMENTS INFLUENCE ANTIPREDATOR AND FORAGING BEHAVIOR OF THE LIZARD ANOLIS CRISTATELLUS?" (2015). Open Access Master's Theses. Paper 544.