Investigators have shown that elephants exhibit consistent individual differences in behavior by rating elephants using personality adjectives. These adjectives, however, are not based on pre-defined measurements of the behaviors performed. Instead, they are based on the observers’ interpretations of an animal’s behavioral patterns, therefore making them subject to observer bias. Furthermore, elephants have a capacity for learning; thus, they may alter their behavioral patterns over time. This behavioral plasticity in itself might be a way of measuring consistent behavioral differences among individuals. With this in mind, I approached elephant personality as a multivariate problem. I used behavioral observations collected from female elephants in Addo Elephant National Park, South Africa. Instead of grouping behaviors into subjective categories prior to analysis (as is often done in studies of elephant behavior), I used ordination methods to determine which correlations among behaviors were important for defining personality. Ordination methods were performed on matrices of the behavior data set and on subsets of behaviors for each age class. I calculated the angular differences among major axes of covariation from the ordinations of subsets to determine if the behaviors that defined personalities differed by age class. I also defined personalities by centroids (in multidimensional space) for non-metric multidimensional scaling (NMDS) scores of each individual and dispersion of NMDS scores for each individual as a measure of behavioral plasticity. I analyzed the effects of plasticity and age on personality of individual elephants using a non-parametric multivariate analysis of variance. Major axes of covariation were not well defined and therefore not useful in describing differences among groups. The interaction of age and behavioral plasticity did have a significant effect on the personalities of individuals as defined by ordination centroid scores. This suggests that incorporating plasticity may be a helpful measurement in quantifying consistent behavioral differences among individuals.

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The ability to adjust behaviors to a particular environment has been well documented across taxa. Our understanding of behavioral plasticity is largely based on experiments in which individuals have a single exposure to an environment. Observed behavioral changes are then traditionally measured in small windows of responsiveness in a single population or species. In this project I investigated the effects of prolonged exposure to predator cues in Gryllodes sigillatus and also tested for the presence of trans-generational effects of this prolonged exposure. I found there were no differences in anti-predator behaviors when measured in subsequent assays compared to control individuals. These results were paired with a comparison of differences in average expressions of behaviors, differences in variances, and behavioral correlations of five closely related cricket species, including G. sigillatus. Our results showed that species differ in average behaviors and plasticity but did not significantly differ in behavioral correlations.

Recent studies have begun to explore the features of perinatal experience which facilitate infants’ abilities to integrate information from the various sensory modalities. The present study utilized a precocial avian infant, the bobwhite quail (Colinus virginianus), to explore 1) what types of postnatal social experience young chicks require to successfully pair sights and sounds and 2) when these experiences need to occur to maintain species-typical intersensory development. Specifically, chicks in this study were reared in one of four conditions: with normal siblings, with altered tactile experience, with altered auditory experience, or with altered visual experience. Findings revealed that altered tactile, auditory, and visual experience presented throughout the first 72 hrs of postnatal development delays chicks’ ability to integrate maternal auditory and visual information at 72 hrs of age, a response reliably seen in unmanipulated chicks. Furthermore, results showed that altered sensory experience in any modality presented during the first 36 hrs of postnatal development delays intersensory responsiveness. Altered tactile or auditory sensory information presented during the last 36 hrs of postnatal development also disrupted normal perceptual development, while altered visual information presented during the last 36 hrs of postnatal development failed to disrupt species-typical responsiveness. These findings suggest that normal sensory experience derived from social interaction is important for normal species-typical development. / Master of Science

Stress affects virtually all organisms and can result in both physiological and behavioral changes. Conditioned defeat in Syrian hamsters is a model of stress-induced behavioral plasticity that occurs in a social context. In this model, hamsters are defeated by a larger, more aggressive counterpart. Defeated hamsters subsequently fail to defend their own territory and show striking and long-lasting increases in submissive behavior even when paired with a non-threatening counterpart. The present series of experiments seeks to identify the brain regions and molecular mediators that contribute to this behavioral plasticity. One brain region that has been overlooked by our laboratory is the hippocampus. The results of the first study suggested that the ventral, but not dorsal, hippocampus is important for the acquisition of conditioned defeat as temporary inactivation of the ventral hippocampus prior to defeat training significantly reduced submissive and defensive behaviors when hamsters were tested with a non-aggressive intruder. Next, we sought to identify a potential molecular mediator of social stress-induced behavioral plasticity in hamsters identified as winners or losers after a fight. Using in situ hybridization for brain-derived neurotrophic factor (BDNF) mRNA, we showed that winning and losing hamsters exhibited differences in BDNF mRNA in several regions including the basolateral and medial amygdala as well as the dentate gyrus of the dorsal hippocampus and CA1 of the ventral hippocampus. We next showed that neurotrophic activity in the basolateral amygdala is important for the acquisition of conditioned defeat because K252a infused into the basolateral amygdala prior to defeat training by an aggressive counterpart, significantly decreased submissive and defensive behavior during subsequent testing. Finally, existing data suggest that the amygdala and hippocampus interact to modulate the formation of emotional memories. To test the hypothesis that the basolateral amygdala and ventral hippocampus interact to mediate the behavioral plasticity observed in conditioned defeat, we simultaneously inactivated these regions either contralaterally or ipsilaterally prior to social defeat. Our results suggest that BLA and VHPC interact to mediate the acquisition of conditioned defeat, however, the nature of this interaction remains to be determined.

Investigators have shown that elephants exhibit consistent individual differences in behavior by rating elephants using personality adjectives. These adjectives, however, are not based on pre-defined measurements of the behaviors performed. Instead, they are based on the observers’ interpretations of an animal’s behavioral patterns, therefore making them subject to observer bias. Furthermore, elephants have a capacity for learning; thus, they may alter their behavioral patterns over time. This behavioral plasticity in itself might be a way of measuring consistent behavioral differences among individuals. With this in mind, I approached elephant personality as a multivariate problem. I used behavioral observations collected from female elephants in Addo Elephant National Park, South Africa. Instead of grouping behaviors into subjective categories prior to analysis (as is often done in studies of elephant behavior), I used ordination methods to determine which correlations among behaviors were important for defining personality. Ordination methods were performed on matrices of the behavior data set and on subsets of behaviors for each age class. I calculated the angular differences among major axes of covariation from the ordinations of subsets to determine if the behaviors that defined personalities differed by age class. I also defined personalities by centroids (in multidimensional space) for non-metric multidimensional scaling (NMDS) scores of each individual and dispersion of NMDS scores for each individual as a measure of behavioral plasticity. I analyzed the effects of plasticity and age on personality of individual elephants using a non-parametric multivariate analysis of variance. Major axes of covariation were not well defined and therefore not useful in describing differences among groups. The interaction of age and behavioral plasticity did have a significant effect on the personalities of individuals as defined by ordination centroid scores. This suggests that incorporating plasticity may be a helpful measurement in quantifying consistent behavioral differences among individuals.

abstract: Of all the signals and cues that orchestrate the activities of a social insect colony, the reproductives' fertility pheromones are perhaps the most fundamental. These pheromones regulate reproductive division of labor, a defining characteristic of eusociality. Despite their critical role, reproductive fertility pheromones are not evenly expressed across the development of a social insect colony and may even be absent in the earliest colony stages. In the ant Camponotus floridanus, queens of incipient colonies do not produce the cuticular hydrocarbons that serve as fertility and egg-marking signals in this species. My dissertation investigates the consequences of the dramatic change in the quantity of these pheromones that occurs as the colony grows. C. floridanus workers from large, established colonies use egg surface hydrocarbons to discriminate among eggs. Eggs with surface hydrocarbons typical of eggs laid by established queens are nurtured, whereas eggs lacking these signals (i.e., eggs laid by workers and incipient queens) are destroyed. I characterized how workers from incipient colonies responded to eggs lacking queen fertility hydrocarbons. I found that established-queen-laid eggs, incipient-queen-laid eggs, and worker-laid eggs were not destroyed by workers at this colony stage. Destruction of worker-laid eggs is a form of policing, and theoretical models predict that policing should be strongest in incipient colonies. Since there was no evidence of policing by egg-eating in incipient C. floridanus colonies, I searched for evidence of another policing mechanism at this colony stage. Finding none, I discuss reasons why policing behavior may not be expressed in incipient colonies. I then considered the mechanism that accounts for the change in workers' response to eggs. By manipulating ants' egg experience and testing their egg-policing decisions, I found that ants use a combination of learned and innate criteria to discriminate between targets of care and destruction. Finally, I investigated how the increasing strength of queen-fertility hydrocarbons affects nestmate recognition, which also relies on cuticular hydrocarbons. I found that queens with strong fertility hydrocarbons can be transferred between established colonies without aggression, but they cannot be introduced into incipient colonies. Queens from incipient colonies cannot be transferred into incipient or established colonies. / Dissertation/Thesis / Ph.D. Biology 2012

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