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McGhee, J. R., & Mestecky, J. (1990). In defence of mucosal surfaces. Development of novel vaccines for IgA responses protective at the portals of entry of microbial pathogens. Infect. Dis. Clin. North Am., 4(2), 315–341.
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Smith, S. F., Appleby, M. C., & Hughes, B. O. (1990). Problem solving by domestic hens: opening doors to reach nest sites. Appl. Anim. Behav. Sci., 28(3), 287–292.
Abstract: In a trial of cage designs for laying hens, eggs were discovered in dust baths where access was restricted by a closed door during the normal laying period (08:00-13:00 h). Observations showed that the hens in these dust bath treatments had developed methods of opening the doors in order to lay in the baths. Three different methods of opening were observed. An average time of 34.4 min was spent attempting to open the doors before access was finally achieved. This implies a strong nesting motivation in these hens. The proportion of eggs laid in the dust baths increased (with occasional fluctuations) over a 24-week period. Door opening is likely to have initially developed in one individual in each cage through a trial and error basis, and then have been learned by cage mates through imitation. The speed and efficiency of door opening was not found to increase with experience or time.
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Petherick, J. C., & Rutter, S. M. (1990). Quantifying motivation using a computer-controlled push-door. Appl. Anim. Behav. Sci., 27(1), 159–167.
Abstract: A computer-controlled push-door system was designed and tested as a method for measuring motivation. Eleven domestic hens were trained to use the push-door to gain access to food. They were deprived of food for 12 h or 43 h on 12 occasions and the push-door was used to measure the amount of “work” (measured as force × time) that they performed to gain access to a food reward. When deprived of food for 12 h the hens took significantly longer (P<0.01) to reach the required threshold of work, than when deprived for 43 h. This difference arose from the amount of time that the hens spent not pushing at the door. The problems encountered with this system and such an approach to measuring motivation are discussed.
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Byrne, R. W., & Whiten, A. (1990). Tactical deception in primates: the 1990 database (Vol. 27). German Primate Center.
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Tooze, Z. J., Harrington, F. H., & Fentress, J. C. (1990). Individually distinct vocalizations in timber wolves, Canis lupus. Anim Behav, 40.
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Schilder, M. B. H. (1990). Social behaviour and social arganization of a herd of plains zebra in a safari park. Ph.D. thesis, , University of Utrecht.
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Würbel, H. (1990). The relationship between social structure and mating system in donkeys & Mating strategies of male donkeys in a promiscuous mating system"l structure and mating system in donkeys &. Diploma thesis, , Faculty of Natural Sciences, University of Berne, Switzerland.
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