Title from title page of PDF (University of Missouri--St. Louis, viewed February 23, 2010). Includes bibliographical references.

<p>The ability to monitor, learn from, and respond to social information is essential for many highly social animals, including humans. Deficits to this capacity are associated with numerous psychopathologies, including autism spectrum disorders, social anxiety disorder, and schizophrenia. To understand the neural mechanisms supporting social information seeking behavior requires understanding this behavior in its natural context, and presenting animals with species-appropriate stimuli that will elicit the behavior in the laboratory. In this dissertation, I describe a novel behavioral paradigm I developed for investigating social information seeking behavior in rhesus macaques in a laboratory setting, with the use of naturalistic videos of freely-behaving conspecifics as stimuli. I recorded neural activity in the orbitofrontal and lateral prefrontal cortex of monkeys as they engaged in this task, and found evidence for a rich but sparse representation of natural behaviors in both areas, particularly in the orbitofrontal cortex. This sparse encoding of conspecifics' behaviors represents the raw material for social information foraging decisions.</p> / Dissertation

Behavioral differences among closely related species can result from adaptation via natural selection, and this is especially true of innately expressed behavior that shows evidence of complex design or function. A major goal of biologists is to understand how and why complex, adaptive behavior evolves. To this end, I investigated the evolution, ecology and genetics of innate burrowing differences in deer mice (genus Peromyscus). First, I show that several species of deer mice recapitulate their natural burrowing habits under laboratory conditions. When I compare these behaviors in a phylogenetic context, I find that burrowing is species-specific and the complex burrows of the oldfield mouse (P. polionotus) likely arose from simple behavior similar to that expressed by two closely related species. Second, I examine the influences of soil composition and genetics on the burrowing behavior of oldfield mice. Although burrow length variation is relatively constant in nature, burrow depth is negatively associated with the silt content of soils. To determine the genetic architecture of complex burrowing, I crossed the oldfield mouse and its sister species, the deer mouse (P. maniculatus), which builds a relatively simple burrow. My results suggest that complexity results from the integration of several component behaviors: the lengthening of entrance tunnels and the construction of an escape tunnel. Additionally, complex burrowing segregates as a dominant trait and I identify four quantitative trait loci that influence burrow variation--three affect tunnel length and a single locus influences escape tunnel construction. Last, I test whether Peromyscus burrow socially. Specifically, I measure burrows constructed by both pairs of mice and individuals across three Peromyscus species with different social systems. Only in the monogamous species (P. polionotus), which is also the only species that builds complex burrows, do pairs of mice coordinate their behavior to build longer burrows. This effect of pairing increases burrow length in same-sex pairs of unrelated individuals, but it is most pronounced in male-female pairs, suggesting that oldfield mice invest most heavily in burrows constructed for the purpose of reproduction.

Animal movement patterns provide a rich source of information for examining a wide range of ecological interactions that span ecological scales from foraging behaviors of individuals to the spread of populations across landscapes. I investigated the causes and consequences of consumer movement, from the localized movements of individuals to the patterns of spread of populations across landscapes, using a series of complimentary microcosm experiments with a model consumer-resource system. In chapter one, I conducted a series of experiments designed to test differences in the fine-scale movement characteristics of swimming rotifers under experimental manipulations of local resource and conspecific abundance. Individual turn frequencies increased in resource-rich environments but were unaffected by competitor density. In contrast, individual swimming speeds increased at high competitor densities but were unaffected by resources. I demonstrated how these contrasting behaviors could be integrated to form predictions of population spread under different ecological scenarios. In chapter two, I tested the predictions established in chapter one by directly measuring the rates of spread of many replicate populations of rotifers in one-dimensional environments. Experimental treatments included a wide range of resource and conspecific densities, and starved versus sated rotifers in the presence versus absence of predator chemical cues. Rates of population spread were negatively correlated with resource abundance, especially when conspecific density was high, and rates of spread of both starved and risk-exposed populations were significantly lower than controls. In chapter three, I tested the effect of resource patchiness, conspecific density, and their interaction, on population spread through a two dimensional landscape. I found that rates of population spread decayed over time indicative of a sub-diffusive movement processes explained by positive density-dependent movement responses. Neither the rate of spread nor the magnitude of its decay differed between patchy and evenly distributed resource treatments, despite observed rotifer preferences for patches. These findings suggest that under certain ecological circumstances resource distribution may be less crucial in predicting population spread than density-dependence. Overall, my research demonstrates mechanistic links between the behavioural responses of individuals to their environment and the resulting larger scale phenomena of population-level movement patterns.

No description available.

No description available.

<p>The evolution of animal signals is driven largely by characteristics of the signaling environment and properties of receiver sensory systems. Selection favors signal traits that increase the probability that a signal will stimulate the sensory systems of intended receivers, but not potential predators, under average environmental conditions. However, environmental conditions often fluctuate, which means that a given signal property may not be equally effective at all times. One potential mechanism that an organism might employ to overcome this challenge is to modulate its signal properties as environmental conditions change in order to maintain stimulation of the receiver sensory system. In this dissertation, I explore the possible role of signal modulation using the motion detection and communication systems of tropical Anolis lizards. </p><p>In order to assess the possible role of signal modulation in the communication behavior of anoles, it was necessary to determine the properties of their motion detection systems. In Chapter 2, I tested whether motion detection properties are conserved across species of anole. I adapted a behavioral assay to quantify the spatial parameters of the motion detectors of three species of Puerto Rican Anolis lizards, with each preferring a distinct structural habitat type. I then compared the results to data previously collected for anoles from Cuba, Puerto Rico, and Central America. Results indicated that all species share a minimum amplitude threshold for detecting moving objects and exhibit multiple peaks in relative response to various motion amplitudes. Fine-scale interspecific differences in the number and values of response peaks were not correlated with structural niche. Overall, the study suggests that the motion detection systems of Anolis lizards are relatively conserved, which may help explain shared features of movement-based signals in anoles.</p><p>For mobile organisms, the spatial relationships of signaling individuals and intended receivers can be fluid. Such fluctuation in the distance between signalers and receivers can greatly impact signal efficacy, but it is unclear exactly how animals cope with this problem. In Chapter 3, I investigated whether signal modulation can serve as an effective strategy to cope with variation in the spacing of receivers in the environment by tuning a signal to maintain stimulation of the receiver sensory system. I evaluated this hypothesis by testing the use of modulation in the tropical lizard Anolis gundlachi in Puerto Rico. I first characterized the motion detection properties of the sensory system of A. gundlachi in the laboratory. I then measured the physical properties of movement-based headbob displays given during staged social encounters under natural conditions. I found a significant positive association between the maximum amplitude of headbob displays and the physical distance to intended receivers. Modulation occurred in response to small-scale changes in signaler-receiver distance, and signalers gave displays that fell within a range of amplitudes predicted to optimally stimulate the visual system of A. gundlachi. These findings strongly suggest that modulation of the physical properties of motion-based signals can be an effective mechanism to tune signals to both characteristics of receiver sensory systems and receiver distance, and can serve as a behavioral strategy to cope with relatively frequent changes in the spacing of individuals. </p><p>Although signaling individuals must effectively capture and hold the attention of intended conspecific receivers, they must also limit eavesdropping by potential parasites or predators. However, predation pressure can vary over the course of an individual's lifetime, or over the course of a day, thereby altering signal efficacy. In Chapter 4, I tested the hypothesis that prey can modulate the physical properties of their signals or their display behavior in order to decrease conspicuousness and potentially limit predation risk. To do so, I conducted a manipulative experiment in nature to determine the effect of predation pressure on the properties of movement-based signals and the display rate of the semiarboreal lizard Anolis sagrei. I found that male anoles reduced the maximum amplitude of headbob displays but not the proportion of time spent signaling on islands onto which predators were introduced, in comparison to males from control islands lacking the predator. Characteristics of the motion detection system and social behavior of A. sagrei show that this reduction in amplitude also decreases signal active space, which might alter the reproductive success of signaling individuals. I suggest that future studies of predator-prey interactions consider the risk effects generated by changes in signals or signaling behavior to fully determine the influence of predation pressure on the dynamics of prey populations.</p> / Dissertation

Eight experiments examined the role of the intertrial interval in the extinction of conditioned fear to a context. Rats were shocked in one context (A) but not in another (B) and freezing responses to Context A were extinguished. The interval between extinction trials was spent in the home cages. Experiments 1a and 1b showed that massed extinction trials produced better response loss but worse learning than spaced trials. Experiment 2 demonstrated that the interval between the final extinction trial and test mediated the level of responding on a test exposure. Experiments 3 and 4 showed that the duration of the extinction trial affected long term response loss, whereby long durations facilitate response loss compared to shorter durations. Subsequent experiments (Experiments 5 to 8) demonstrated that the first in the series of massed extinction trials reduced the associability of subsequent trials. Associability was restored by alternating extinction trials between Context A and Context B. The results are discussed in terms of the role accorded to self-generated priming in the models developed by A. R. Wagner (1978; 1981).

Thesis (M.Sc.)--Victoria University of Wellington, 2008. / Includes bibliographical references.

Thesis (Ph. D. in Biological Sciences)--Vanderbilt University, May 2009. / Title from title screen. Includes bibliographical references.