title: Evaluating thermal resource partitioning : By sympatric lizards Anolis cooki and A. cristatellus: a field test using null hypotheses.
abstract: The field thermal biology of sympatric Anolis cooki and A. cristatellus were evaluated in January and in August in desert scrub forest at Playa de Tamarindo near Guanica, Puerto Rico. Data on randomly positioned copper models of lizards, each equipped with a built-in thermocouple, established null hypotheses about basking frequency and operative temperatures (Te) against which the behavior and body temperatures (Tb) of live lizards were evaluated. Both species exhibited non-random hourly basking rates (more marked in cristatellus than in cooki), and cristatellus was virtually inactive during the warm mid-day hours. The relationship between lizards' Tband randomly sampled Tediffered between the species: cristatellus's mean Tbwas 2° to 3° C lower than randomly sampled mean Tein both months, whereas cooki's mean Tbwas slightly higher than mean Tein January and slightly lower in August. Although cooki's mean Tbwas higher than that of cristatellus in both months, the Tb's of the two species overlapped substantially over an annual cycle. Given the similarities in their field active Tband the low thermal heterogeneity among microsites at Playa de Tamarindo, these species appear not to partition the thermal environment there in a coarse-grained way. Instead, the relatively small differences in their field active Tbprobably result from small differences in their use of similar microhabitats within their mutually exclusive territories. Thermal resource partitioning by territorial animals is unlikely unless thermal heterogeneity is coarse-grained in relation to territory size.
authors.affiliation: Department of Biological Sciences, Barnard College, Columbia University, 10027, New York, NY, USA.
authors.forename: P E
authors.initials: PE
authors.lastname: Hertz
keywords: Anolis thermal biology; Partitioning thermal resources