Abstract: Cerebral lateralization, the preferential use of one hemisphere of the brain to perform certain cognitive functions, is a widespread and evolutionarily ancient adaptation. Lateralization appears to enhance cognitive capacity, yet substantial individual variation in the strength cerebral lateralization is apparent in all species studied so far. It is puzzling that cerebral lateralization, a seemingly advantageous trait, has not been driven to fixation. It has been suggested that variation in lateralization may be linked to individual variation in behaviour, which itself may be subject to disruptive selection. We examined the relation between cerebral lateralization and individual variation in boldness in the convict cichlid, Archocentrus nigrofasciatus. We show that convict cichlids that are more strongly lateralized when exploring a familiar environment, but not a novel one, are quicker to emerge from a shelter in a test for boldness. The possibility that cerebral lateralization is linked to life history strategy is discussed.

Abstract: Temperament traits in animals may have important fitness consequences, but have received little attention from ecologists or evolutionary biologists. A few studies have linked variation in temperament with fitness, but none has measured selection on temperament traits. We estimated the strength of selection on female boldness and docility on bighorn sheep ewes, Ovis canadensis. The Ram Mountain population experienced little predation pressure during the first 25 years of study, then 2 years (1997 and 1998) of frequent predation by cougars, Puma concolor, during which adult ewe mortality almost tripled over the long-term average, to 27% a year. During years of high predation, we found moderate selection favouring bold ewes, and age-specific selection on docility. Old ewes appeared more vulnerable to predation than young ewes. In contrast, no evidence of selection on temperament traits was observed during 2 years of low predation (1996 and 1999). These results suggest predator-induced selection favouring bold and nondocile ewes. Leadership was highly correlated with age and may increase the risk of predator encounter. Leadership alone, however, could not explain the higher vulnerability of old ewes to predation. Cougar predation on bighorn sheep occurs sporadically and unpredictably, probably because individual cougars often are prey specialists. Cougar predation may have limited microevolutionary effects on temperament in bighorn sheep, because it mostly affects ewes near the end of their reproductive life span and because of potential countervailing selection on boldness and docility. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Abstract: We describe two field experiments with wild guppies, Poecilia reticulata, in Trinidad that demonstrated that guppies can acquire foraging and predator escape-response information from conspecifics. In the foraging experiment, subjects were presented with two distinctly marked feeders in their home rivers. One feeder contained a conspecific shoal in a transparent container. Guppies preferred to enter the feeder containing this artificial shoal over the other feeder. In a test phase, the artificial shoal was removed and the feeders replaced at the testing site after a 5-min delay. More guppies entered the feeder that had contained the artificial shoal over the other feeder, a difference that can be explained only by the fish learning the characteristics or location of the feeder during the training phase. We suggest that subjects acquired a foraging patch preference through a propensity to approach feeding conspecifics, a local enhancement process. In the predator escape-response experiment, naive 'observer' guppies could avoid an approaching trawl net by escaping through either a hole to which 'demonstrator' guppies had been trained or through an alternative hole. When the demonstrators were present, the naive observers escaped more often and more rapidly by the demonstrated route than the alternative route. When the demonstrators were removed, observers maintained a route preference according to the training of their demonstrators, which suggests that the observers had learned an escape route through following or observing their more knowledgeable conspecifics. Thus, both experiments reveal that guppies can socially learn in the wild. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.

Abstract: Managers concerned with shrinking habitats and limited resources for wildlife seek effective tools for limiting population growth in some species. Fertility control is one such tool, yet little is known about its impacts on the behavioral ecology of wild, free-roaming animals. We investigated influences of the immunocontraceptive porcine zona pellucida (PZP) on individual and social behavior in bands of feral horses (Equus caballus) in three discrete populations and used 14 hierarchical mixed effect models to gain insight into the influences of PZP treatment on feral horse behavior. A model of body condition was the strongest predictor of feeding, resting, maintenance, and social behaviors, with treated females allocating their time similarly to control females. Time spent feeding declined 11.4% from low condition to high condition females (F1,154 = 26.427, P < 0.001) and was partially reciprocated by a 6.0% increase in resting (F1,154 = 7.629, P = 0.006), 0.9% increase in maintenance (F1,154 = 7.028, P = 0.009), and 1.8% increase in social behavior (F1,154 = 15.064, P < 0.001). There was no difference detected in body condition of treated versus control females (F1,154 = 0.033, P = 0.856), but females with a dependent foal had lower body condition than those without a foal (F1,154 = 4.512, P = 0.038). Herding behavior was best explained by a model of treatment and the interaction of band fidelity and foal presence (AICc weight = 0.660) which estimated no difference in rate of herding behavior directed toward control versus treated females (F1,102 = 0.196, P = 0.659), but resident females without a dependent foal were herded 50.9% more than resident females with a foal (F3,102 = 8.269, P < 0.001). Treated females received 54.5% more reproductive behaviors from stallions than control mares (F1,105 = 5.155, P = 0.025), with the model containing only treatment being the most-supported (AICc weight = 0.530). Treated and control females received harem-tending behaviors from stallions equally (F1,105 = 0.001, P = 0.969) and agonistic behaviors from stallions equally (F1,105 < 0.001, P = 0.986). Direct effects of PZP treatment on the behavior of feral horses appear to be limited primarily to reproductive behaviors and most other differences detected were attributed to the effects of body condition, band fidelity, or foal presence. PZP is a promising alternative to traditional hormone-based contraceptives and appears to contribute few short-term behavioral modifications in feral horses.

Abstract: Behavioral and physiological characteristics of individuals within the same species have been found to be stable across time and contexts. In this study, we investigated individual differences in learning abilities and object and social manipulation to test for consistency within individuals across different tasks. Individual ravens (Corvus corax) were tested in simple color and position discrimination tasks to establish their learning abilities. We found that males were significantly better in the acquisition of the first discrimination task and the object manipulation task, but not in any of the other tasks. Furthermore, faster learners engaged less often in manipulations of conspecifics and exploration of objects to get access to food. No relationship between object and social manipulation and reversal training were found. Our results suggest that individual differences in regard to the acquisition of new tasks may be related to personalities or at least object manipulation in ravens.