Abstract: Local enhancement is one way individuals may realize foraging advantages from grouping. A distinction between fine-level and coarse-level local enhancement is made, the latter often being neglected in theoretical research on group foraging. In the former case, an individual has a higher feeding rate as a member of a group because individuals copy other group members' foraging, whereas in the latter, groups simply attract other individuals to patches where food is particularly abundant and copying does not occur within the group. Coarse-level local enhancement may decrease the time needed to find profitable feeding patches in spatially and temporally variable environments. A review of the empirical literature indicated that coarse-level local enhancement is typical in bird species foraging in open habitats and in large groups with relatively little competition between group members whereas the opposite attributes fit the species for which fine-level local enhancement had been documented. Furthermore, species in which coarse-level local enhancement prevails usually forage in temporary groups. However, coarse-level and fine-level local enhancement are not necessarily mutually exclusive, but which one is more important in a particular case may be habitat-dependent.

Abstract: Pigeons were trained on operant schedules simulating successive encounters with prey items. When items were encountered on variable-interval schedules, birds were more likely to accept a poor item (long delay to food) the longer they had just searched, as if they were averaging prey density over a short memory window (Experiment 1). Responding as if the immediate future would be like the immediate past was reversed when a short search predicted a long search next time (Experiment 2). Experience with different degrees of environmental predictability appeared to change the length of the memory window (Experiment 3). The results may reflect linear waiting (Higa, Wynne, & Staddon, 1991), but they differ in some respects. The findings have implications for possible mechanisms of adjusting behavior to current reinforcement conditions.

Abstract: The study of animal behavior has been around for many years, but it is divided into several fields which often do not communicate well. These fields of study include (but are not limited to) comparative psychology, ethology, behavioral ecology, and sociobiology. Comparative psychology is more isolated than the other three fields, which share a common biological/evolutionary background. This paper gives a brief background of the four main fields of animal behavior research, along with a list of sources, both specialized and interdisciplinary.

Abstract: Ten feral mares free-roaming in Maryland, USA, were inoculated with porcine zonae pellucidae (PZP) protein before the breeding season for three consecutive years (1988-90). Ovarian function was monitored for 51 days during the peak of the breeding season after the third annual PZP inoculation, in seven of these mares and in four untreated control mares, by means of urinary oestrone conjugates and nonspecific progesterone metabolites. None of the ten inoculated mares became pregnant in 1990, compared with 55% of 20 control mares, which included two of the four monitored for ovarian function. Three of the untreated mares demonstrated apparent normal ovarian activity, characterized by preovulatory oestrogen peaks, concurrent progesterone nadirs at ovulation, breeding activity, and luteal-phase progesterone increases after ovulation. Two of the seven monitored PZP-treated mares demonstrated ovulatory cycles that did not result in conception. One was pregnant as a result of conception in 1989 and demonstrated a normal, late-gestation, endocrine profile. The remaining four PZP-treated mares revealed no evidence of ovulation, and urinary oestrogen concentrations were significantly depressed. The experiments indicated that (i) a third consecutive annual PZP booster inoculation is greater than 90% effective in preventing pregnancies in mares and (ii) three consecutive years of PZP treatment may interfere with normal ovarian function as shown by markedly depressed oestrogen secretion.

Abstract: Draft mares and their mule foals were observed from the day of birth to Week 17 of each foal's life. The rate of nursing was recorded and the duration of nursing activity to the nearest second. The rate at which foals engaged in nursing activity varied at each age. The duration of nursing bouts varied slightly as the foals matured. Aggression was recorded during both nursing and non-nursing activity for both the mares and foals. Maternal aggression was highest during nursing activity, especially during the pre-nurse nuzzling period. Maternal aggression increased as the foals matured. Mother-directed foal aggression was primarily in response to maternal aggression. Spatial relationships between each focal dyad were recorded when the foals were upright, not nursing and when they were recumbent. Spatial relationships differed based on the foal's state. The activity in which the mare engaged while her foal was recumbent was recorded. The movements of the mares were also recorded during foal recumbency. Mares approached or maintained their distance from their recumbent foal more than they left their recumbent foal in all weeks of the study, except Week 2.