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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 9, Issue 1, 1996


The Relationship Between Calcium Gland Size, Fecunduty and Social Behavior in the Unisexual Gecks Lepidactyluse Lugubris and Hemidactylus Garnotii


three present experiments examined the relationship between calcium gland size, fecundity, and dominance/social behavior in the unisexual geckos, Lepidodactylus lugubris and Hemidactylus garnotii. Study 1 examined the above variables while the geckos were housed communally and solitarily. L.lugubris established stable dominance hierarchies through aggressive interactions, whereas H. garnotii neither established a dominance hierarchy nor displayed signs of aggression while housed communally. Eggs were developed by 4 of 4 dominant L lugubris but by only 1 of 4 subordinate L lugubris and 1 of 6 H. garnotii. Calcium glands decreased in size in the subordinate L lugubris and H. garnotii during communal housing, then recovered when the geckos were housed solitarily. Study 2 examined the relationship between reproductive state and calcium gland size in L lugubris. Calcium glands were found to be smallest prior to and immediately after oviposition and largest when  eggs were yolking follicles. Study 3 examined the effect of sociality on fecundity in H. garnotii.Egg development was not related to whether geckos were housed solitarily or as dyads. Calcium gland size in geckos appears to be related to both stress and to the reproductive state of the gecko. We hypothesize that stress decreases the size of geckos' calcium glands resulting in decreased egg production in stressed animals.

Variations in the Structure of the Peep Vocalization of Female Domestic Chicks (Gallus Gallus Domesticus) on Days Five and Six Post-Hatching


chicks {Callus gallus domesticiis) were reared in pairs from day three post-hatching. On the fifth day of life, a chick was  separated from its brood mate and 30 sees, later the chicks' vocalizations were recorded for five minutes. The recordings were analysed using Canary 1.1 sound analysis system running on Mac II vx. Seven acoustic parameters of the peep vocalizations of female chicks were measured (duration (msec), maximum frequency (kHz), minimum frequency (kHz), difference between maximum and minimum frequency (kHz), peak frequency (kHz), energy (watts) and average power (joules)). During separation chicks produced peep calls that differed in structure. In total, 12 female chicks' vocalizations were examined and seven chicks produced three distinct peeps . These were classified as short, medium and long. Three calls of each type for each chick were examined. Short peeps have a narrow frequency range and short duration, medium peeps have a wider frequency range, longer duration and a short upper inversion preceding the descending frequency. Long peeps have the widest frequency range, the longest duration and have the most complex structure. The main finding of this study is that the chick of the domestic fowl can produce hree distinct types of peep call. 


Some of Aristole's Writings About Bird Behavior and Issues Still Current in Comparative Psychology

In his

search for the causes of the diversity observed in living beings,including humans (zoa), Aristotle did not define them by their bodily parts and generation process only. He also payed extensive attention to nutrition and especially to character (ethos). Indeed, combined with the other three types of features, it  determines the way of life (bios) and subsequent activities (praxeis) of each species at both intra and extra-specific levels. Character in the less developed and shorter-lived animals is less obvious. Conversely, the longer-lived ones are granted "a certain natural capability in relation to each of the soul's affections" (HA 608all-13). Birds are of that kind. The present paper examines how birds are approached by Aristotle with respect to breeding and parental care in order to shed some light on the method, purpose and results of his comparative psychology.

The Response of LLamas (Lama Glama) to Familiar and Unfamilar Humans


current study explored the response of llamas to familiar and unfamiliar humans under housing and management conditions typical of both zoological gardens and llama farms. A group of five adult llamas was exposed to three 30-min socialization sessions with one female handler, who offered food and tactile contact. Subjects were then tested for their responses to the familiar handler (A)versus a stranger (B) in an Aj-B-Aj design. Proximity to the handler, sampled at 5-sec intervals through the 1-min test exposures, was used as a dependent variable. For  both the A,-B and B-A^ comparisons, the number of animals present in the test area was significantly lower in the presence of the unfamiliar human (p < 0.001; 2-tailed Randomization Test). This finding has important implications for llama housing and management, where individual humans may serve as discrete conditioned or discriminative stimuli if repeatedly paired with hedonic events. Such human-based itioningmay affect animal behavior, physiology, and motivation. Interactions with humans may thus potentially confound experimental results in a research environment, or be used to facilitate eanagement or training.