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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 5, Issue 1, 1991

Research Article

Acquistion of Pine Cone Stripping Behaviour in Black Rats (Rattus rattus)

Black rats (Rattus rattus) have begun occupying a new habitat in recent years —the Jerusalem pine (Pinus halepensis) forests in Israel. In this, otherwise almost sterile habitat, the sole source of nourishment for the rats is the pine seems that can only be extracted from the cones through a complex feeding technique. Adult black rats unfamiliar with the technique (termed "naive") were unable to attain it either through trial and error or through observational learning when housed with experienced rats (termed "strippers"). In contrast, black rat pups raised by stripper mothers did learn the pine cone opening behaviour. In addition to the presence of a stripper model, however, the clues of the pine seeds themselves, as well as partially open cones, may also play a role in the acquisition of the technique. The state of the cone itself, when encountered by the rat pups, may be an important factor. Three groups of experimental animals were used: 25 pups born to naive mothers and reared on rat chow without exposure to either stripping mothers or partially opened cones; 25 pups born to naive mothers and exposed to pine cones in various stages of opening; 55 pups born to stripper mothers and exposed both to pine cones and to the presence of their mothers actively involved in stripping the cones and feeding on the seeds. We found that pine cone stripping behaviour is learned through two stages of a local enhancement effect: First, the pups are directed to the pine cones as a food resource, and then to the cone's proximal end as a starting point. The development of the stripping technique is acquired individually, with accumulating experience.

Discrimination of Musical Stimuli by Rats (Rattus norvegicus)

Rats were trained under go-no go conditions to discriminate among complex acoustic stimuli (short musical sequences). In order to investigate the role of different stimulus attributes in discriminative performance, two short musical excerpts differing in their melodic pattern, but maintaining the number, pitch, and duration of notes constant were provided in two different timbres, to obtain four different complex auditory stimuli. According to the experimental condition, the discriminative stimuli were, therefore, different in structure, in timbre or in both aspects. The animals were able to discriminate efficiently among the musical sequences only when cues furnished by timbre were available, whereas melodic differences made no difference. In the experimental setting used, the rat's discrimination of complex auditory stimuli appears, therefore, to be based neither on the melody nor on a compound of melody and timbre,but simply on the properties of the timbre of the stimuli.

Variation in the Aggressive Behavior of the Parthenognetic Lizard (Cnemidophorus uniparens, Teiidae)

The desert-grassland whiptail (Cnemidophorus uniparens) is an  all-female lizard species that reproduces clonally by parthenogenesis. Here we report marked geographic variation in the aggressive behavior of paired individuals in which pairs consisted either of individuals from within study sites or individuals representing each of two different study sites. Although we document allozyme variation within each study site, this did not differ significantly between sites. Previously reported restriction endonuclease analysis of mitochondrial DNA indicates that the two lizard populations used in the present study arose from the same or closely related maternal ancestors by interspecific hybridization. Gross climatological differences do not appear to explain the behavioral variation between sites. The possible roles of polygenic effects not detected by the biochemical analyses and laboratory ies of environmental effects on the development of aggressive behavior await further investigation.

Teaching and Research in Animal Behaviour in South African Universities: A Survey

A qualitative questionaire-based survey of psychology and biology/zoology departments at all 21 universities found in the Republic of South Africa was carried out in 1990 in order to determine how many of them taught and/or conducted research in the subdiscipline of animal behaviour, i.e., either as ethology or comparative psychology or both,and their future plans. Altogether only 10 psychology and 12 biology/zoology departments responded to the questionaire. In addition, a further five psychology departments were contacted via phone or through personal communication. The survey revealed a somewhat disappointing picture with regard to psychology departments—only three of them taught courses in animal behaviour regularly, five taught only small modules on animal behaviour whereas the rest of the departments neither did nor ever planned to do so in the near future. Most psychology departments were of the opinion that the study of animal behaviour was not important at all and consequently only a few of them had conducted or were still conducting some research in the area. In contrast, the picture was a much more exciting one with regard to biology/zoology departments—all of those which had responded, except for one only, had taught courses on animal behaviour in their curricula and had done so for at least a decade. The biology/zoology departments concerned considered animal behaviour to be a relatively important subdiscipline and the majority of them had also conducted or were still conducting some research in the area. Possible explanations for this discrepancy as well as implications thereof for the future of the study of the subdiscipline in South African universities are discussed.

Letter from the Editor

Ethel Tobach, Editor American Museum of Natural HistoryCentral Park West at 79th Street New Yrok, NY, 10024-5192,USA