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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 11, Issue 1, 1998


Chronological Development of Behavior in the Blind Mole Rat (Spalax Ehrenbergi)

The blind mole rat {Spalax ehrenbergi) is a potentially highly aggressive solitary, subterranean rodent. Data on growth and development of pups are lacking since it is difficult to raise pups in captivity and, until recently, the blind mole rat has never bred in captivity. In this study six litters were maintained in six large semi-natural setups. We describe for the first time the chronological development of behavior in the blind mole rat from day of birth until the young disperse and establish their own independentterritories. The relatively short gestation period (34 days) and low birth mass

(5-6 g) combined with the need to acquire all survival skills prior to dispersal, are probably correlated with the relatively lengthy development of the blind mole ratcompared to Bathyergidae.

How Many Dimensions are Needed to Describe Temperament in Animals: A Factor Reanalysis of Two Data Sets

Factor analysis has commonly been used to infer the dimensions of animal temperament. However, the results were often complicated by large number of broad and situation-specific factors caused by low psychometric adequacy of the correlation matrices,undermining the assumptions of factor analysis. In this study I reanalyzed the datasets obtained by Royce, Foley & Yeudall (1973) and Gervai & Csanyi (1985) including,however, only the variables with high correlations (multiple R^ > 0.3) and psychometric adequacies (Kaiser-Meyer-Olkinmeasure > 0.5). This yielded more stable andsimpler factor solutions than in the original studies. Specifically, even though the present reanalysiscannot rule out the existence of other temperament factors, it indicates thattwo general dimensions, Activity-Exploration and Fear-Avoidance, are present in suchdiverse species as mice and the paradise fish.

Startle-Freeze Behavior in Weaned Pigs

Pigs may express a startle response and then freeze after they have heard

an auditory stimulus. The objective of this study was to induce startle-freeze behaviour, describe it and to seek potential variables that might influence it. A startle-freeze response lasting 1 to 12 seconds was produced in 36 pigs 5-6 weeks old penned in 12 groups (3 pigs per group), using a cymbal (26 cm radius) to produce a sound of 1 10 dB intensity. This was repeated at 4 minute intervals for 8 stimuli over 28 minutes. The duration of the startle-freeze response decreased over presentations and all pigs had ceased to respond by the seventh stimulus. The frequencies of social interaction, ingestion and lying or sitting behaviours before freezing decreased after the freeze period, and standing or walking increased. The behaviours shown before and after immobilisation were not independent (x\ = 101.9, p < 0.001). The social status of each group was determined from videotape records. The dominance rank of the pig was significantly related to the onset of immobilization; the most dominant pigs responded to the noise first, often 1 to 2 seconds ahead of lower ranked pigs (x\ = 15.74, p < 0.05). In conclusion, pigs show a clear startle-freeze response to a novel auditory stimulus, they habituate rapidly and the onset of startle-freeze behaviour depends upon their social status.