Daniel W. Leger

Antipredator vigilance of juvenile and adult thirteen-lined ground squirrels and the role of nutritional need

Juvenile thirteen-lined ground squirrels, Spermophilus tridecemlineatus, are less vigilant (i.e. they spend less time visually scanning the environment) than adults. To determine whether nutritional need was a potential cause of this difference, we supplemented two groups of free-ranging juveniles during the predispersal stage, while juveniles were still near and around the natal burrows. The high-energy food group (HEF: 11 squirrels) received peanut butter and oats while the low-energy food group (LEF: seven squirrels) received lettuce. Adults (14 squirrels) were also supplemented, but due to their greater home range sizes, it was not feasible to classify them as either HEF or LEF. To evaluate the effect of supplementation on antipredator vigilance, the behavioural act of visually scanning for predators, we videotaped individuals while they were foraging above ground during 5-min observation periods. Each squirrel was observed and weighed during three time periods over 23 days. From the videotape, we extracted measures of time spent vigilant, locomoting and foraging. All three categories of squirrels gained mass over the study period, but the HEF juveniles rapidly exceeded that of the LEF juveniles. Early in the study, LEF and HEF juveniles did not significantly differ in either body mass or time budgets, and, initially, both juvenile groups were similar to adults in the amount of time devoted to vigilance. Later in the study, the behaviour of HEF juveniles closely resembled that of adults (increased time devoted to vigilance and decreased time devoted to foraging), while LEF juveniles decreased vigilance and increased their foraging time. This study indicates that for thirteen-lined ground squirrels the lower vigilance of juveniles is due, at least in part, to the greater nutritional needs of young animals with consequent increases in foraging, which is largely incompatible with vigilance. Copyright 2000 The Association for the Study of Animal Behaviour.

Vocalizations of Belding's ground squirrels (Spermophilus beldingi)

Abstract Vocalizations of Beldings ground squirrels (Spermophilus beldingi) were recorded during the summer of 1982 near Tioga Pass in the central Sierra Nevada of California. Sonagrams were made and call parameters were measured. Discriminant function analyses revealed that multiple-note calls (‘trills’) differed acoustically depending on whether they occurred in response to a predator, or were given by males following copulations. The post-copulatory trills of males were individually distinctive. Among anti-predator trills there was no evidence of predator-specificity within the narrow range of predators tested: trills given to two species of (stuffed) weasels (Mustela), to dogs and to humans were statistically indistinguishable. Sonagrams of trills occurring in agonistic contexts suggest that a third general category of trills may exist, but agonistic trills were more variable than either anti-predator or post-copulatory trills. The ground squirrels also gave single-note calls in the three contexts described above, either repetitively (‘chirps’) or singly (‘whistles’). Neither chirps nor whistles encoded any obvious situation-specific information, except that whistles were typically associated with rapidly-moving predators, usually raptors. The post-copulatory chirps of males were individually distinctive. Vocalizations of Beldings ground squirrels may not vary among contexts as much as do the analogous calls of California ground squirrels (S. beecheyi).

Relation between food preference and food-elicited vocalizations in golden lion tamarins (Leontopithecus rosalia).

We report the results of 2 studies on food-elicited vocalizations in golden lion tamarins (Leontopithecus rosalia). First, we investigated the preferences of 10 golden lion tamarins for 6 foods. Tamarins prefer mealworms and raisins significantly more than apple, egg, carrot, or marmoset diet. Food preference rank was significantly and positively correlated with the rank of latency to choose a particular food. Second, we investigated the relation between food preference and 15 vocal parameters measured from the calls emitted by 5 tamarins to a subset of the foods. Only 1 parameter was significantly correlated with food preference across animals. Within-subjects multivariate analysis of variance showed that the vocalizations to foods are significantly different. Our results support an hypothesis that food-elicited vocalizations vary in ways that correspond to the callers preference but not in a manner that labels food type.

FIRST DOCUMENTATION OF COMBINATORIAL SONG SYNTAX IN A SUBOSCINE PASSERINE SPECIES

Abstract Birds with songs having two or more acoustically distinct elements can arrange them either rigidly (i.e., in the same sequence) or flexibly. Flexible song syntax can be achieved either by varying the number of repetitions of elements or by combining elements in different ways. Combinatorial syntax has been documented only in the songs of oscine passerines and in one nonpasserine, but not in the suboscine passerines. Dawn and day songs of a tyrant flycatcher, the Flammulated Attila (Attila flammulatus), were recorded in Costa Rica. Flexible syntax was noted in both dawn and day song. Attilas not only varied the number of repetitions of their song elements but also combined elements in various ways. This appears to be the first reported case of combinatorial song syntax in a suboscine species.

Cross-gender perceptions of facial attributes and their relation to attractiveness: Do we see them differently than they see us?

Examination of perceptions of human facial attributes revealed that individual attributes are similarly perceived by males and females. However, patterns of attribute interrelationships differ as a function of gender of the face. Undergraduate students (N=280) rated pictures of 40 male or female Caucasians on 12 physical attributes (e.g., nose size, face width) and overall attractiveness. The four sets of attribute ratings (defined by rater gender and picture gender) were submitted to principal components analyses, and five-factor solutions were found for each condition (accounting for about 76% of the variance). Comparisons of the four component solutions using confirmatory factor procedures revealed that male and female raters share one factor structure when rating photographs of female faces and another factor structure when rating photographs of male faces. Multiple regression analyses revealed that the patterns of attribute interrelationships were not “perceptual units” in the perception of attractiveness, and that different “rules” are used to assess the attractiveness of male and female stimuli faces. The importance of these results for models of facial attractiveness and interfacial similarity judgments are discussed.

GEOGRAPHIC VARIATION IN SONG OF THE BRIGHT-RUMPED ATTILA (TYRANNIDAE: ATTILA SPADICEUS): IMPLICATIONS FOR SPECIES STATUS

Abstract Bright-rumped Attilas (Attila spadiceus) have two song forms, one sung primarily at dawn, the other primarily during the rest of the day. Both songs consist of a main phrase and an optional terminal phrase. Our recordings of dawn and day songs in Costa Rica were very similar to those made elsewhere in Central America. However, Central American dawn songs were significantly different than dawn songs from South America, both in terms of quantitative features (temporal and frequency variables) and qualitative characteristics (note shape). Day songs from Central and South America were similar. Song differences suggest that the Bright-rumped Attila may be two species, one in Central America, the other in South America.

Versatility from a Single Song: The Case of the Nightingale Wren

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Personal computers and behavioral observation: An introduction

Some fundamental aspects of observational data are outlined, and some basic issues in implementation of small computers in observational research are discussed.