Subspecific divergence in a loud call of the ruffed lemur (Varecia variegata)

A loud call of the ruffed lemur (Varecia variegata) was analyzed for subspecific and gender differences according to four variables: pulse rate, median pulse duration, median high frequency, and median low frequency. These vocalizations of black-and-white and red ruffed lemurs and one hybrid ruffed lemur were recorded at the Duke University Primate Center (Durham, NC). Significant differences were found between subspecies but not between the sexes. Quantitative differences in this loud call of ruffed lemur subspecies indicate that these prosimians exhibit subspeciation trends similar to anthropoid primates for which comparable data exist. Preliminary data are presented that support the hypothesis that the vocalization functions as a terrestrial predator alarm call

LIMITS ON THE WAVELENGTHS REPRESENTED IN ULTRAVIOLET IMAGES OF LEPIDOPTERA

Volume: 62Start Page: 133End Page: 13

Species recognition of color and motion signals in Anolis grahami : evidence from responses to lizard robots

Male Anolis lizards exhibit an impressive diversity of dewlap color patterns and motion displays. These traits are thought to mediate species recognition, but direct experimental support is limited. It is also unclear if and how color and display behavior each may contribute to the signaling of species identity. We used a programmable robotic lizard to manipulate these signal components independently in Anolis grahami. Four robot variants were used: a control treatment that displayed the conspecific (orange) dewlap color and headbobbing sequence, 2 treatments that differed from the control only in dewlap coloration (light or dark blue), and a fourth treatment that differed from the control only in headbob display pattern (reversed headbob display structure). Artificial dewlaps were calibrated in color and brightness to the A. grahami visual system using a computational model. We presented robots to 102 adult male subjects and quantified their responses for durations of dewlap pulsing and headbob displays. Subjects spent significantly more time pulsing their dewlaps in response to control (conspecific) robot displays than to treatments that deviated from the control either in dewlap color or in headbob display structure. Our findings implicate both morphology and behavior as functional components of social signaling in A. grahami, thus underscoring the complex, multicomponent nature of anoline displays.7 page(s

Gaping displays reveal and amplify a mechanically based index of weapon performance

Physical prowess, a key determinant of fight outcomes, is contingent on whole‐organism performance traits. The advertisement of performance, via display, is poorly understood because it is unclear how information about performance is encoded into display characteristics. Previous studies have shown that weapon performance (i.e., bite force) predicts dominance and reproductive success in male lizards. We tested the hypothesis that gaping displays by adult male collared lizards (Crotaphytus) can provide an index of weapon performance by exposing the major jaw‐adductor muscle complex and that white patches at the mouth corners amplify this index. For territorial adult males, the breadth of the muscle complex, which is not correlated with body size, was a strong predictor of bite force. For nonterritorial yearling males and females, however, measures of body and head size predicted bite force. The patches are highly conspicuous, exhibit UV‐reflecting properties within the visual range of lizards, and provide size‐independent information about bite force only in adult males. We conclude that exposure of the muscle complex during gaping displays can provide rival males with a reliable, body‐size independent, biomechanically based index of weapon performance, an index that the mouth‐corner patches amplify. Indexes that transmit information through mechanistic links to performance are expected to be widespread among animals.14 page(s

Evolution of displays in Galápagos lava lizards : comparative analyses of signallers and robot playbacks to receivers

Differentiation in the structure of animal signals and displays among closely related species has intrigued biologists for centuries. Such divergence is often attributed to behavioural premating isolation, where sexual selection has favoured species recognition in environments containing sympatric congeners. However, in some cases closely related taxa have undergone speciation and display differentiation in isolation, in the apparent absence of benefits afforded by species recognition. Such is the case for the lava lizards (Microlophus spp.) endemic to the Galápagos Islands, where no two species overlap in distribution and all are thought to have evolved in allopatry from congeners. To test alternative evolutionary models, we used several phylogenetic comparative methods to assess how Microlophus displays have evolved. Results showed some potential for the influence of genetic drift, but little evidence of sexual selection (via male-male competition) or colonization history on the way displays have diverged among taxa. We then used lizard robots to test whether two representative Galápagos lava lizard species, Microlophus grayii and Microlophus indefatigabilis, would respond preferentially to a robot performing conspecific displays over those of the congener. We predicted that, in the absence of reinforcing selection, neither species would show a preference for conspecific displays. Results were mixed: whereas M. grayii showed no discrimination of conspecific over heterospecific displays, male M. indefatigabilis showed significantly stronger responses to their own displays than to those of the heterospecific. We then conducted the same experiment with a mainland congener, Microlophus occipitalis, to provide a broader view of potential responses across the group. Results revealed significant discrimination against heterospecific displays. We discuss our findings in light of hypotheses of signal differentiation, and suggest alternative interpretations for recognition of conspecific displays in species that are thought to have evolved in isolation.12 page(s