Browsing by Author "Sewall, Kendra B."
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- Brain and Cognitive Consequences of Early-Life Immune System Challenge in a SongbirdCampbell, Simone Alicia (Virginia Tech, 2016-05-17)Cognition, defined as the mechanism by which an animal acquires, processes, stores, and uses information present in the environment, is a trait that is sensitive to developmental conditions. Existing research supports the idea that the ability to develop and maintain cognitive abilities depends on the physiological condition of the individual, which can be influenced by the early environment. Alterations in maternal care, social stress, and malnutrition are some examples of environmental conditions that impact development and resulting cognitive abilities across taxa. The primary goal of this research was to determine whether immune system challenge during the critical song learning period in zebra finches (Taeniopygia guttata) would lead to long term negative impacts on song quality and learning, spatial learning, and neophobia. Immune challenge during this period of development did not produce long term impacts on learning or memory, nor did it lead to any changes in neophobic responses. However, birds that were hatched later in a clutch performed better on the motoric and spatial tasks, and were less neophobic. Future research in zebra finches that can describe the variation in song attributes as a function of hatching order would be a useful first step in determining a mechanistic link between hatch order and song learning outcomes.
- Characterizing the Role of Magnetic Cues Underlying Spatial BehaviorPainter, Michael Scott (Virginia Tech, 2017-01-09)In the 50+ years since the discovery of magnetic compass orientation by migratory songbirds, evidence for the use of magnetic cues has been obtained for a range of taxonomic groups, including several classes of vertebrate and invertebrate taxa. Surprisingly, however, the biophysical mechanisms and biological substrate that underlie magnetic sensing are still not fully understood. Moreover, while use of magnetic cues for compass orientation is intuitive, the functional significance of other forms of behavioral responses mediated by magnetic cues, such as spontaneous magnetic alignment, is less clear. The following research was carried out to investigate the mechanisms underlying magnetic orientation in vertebrates and invertebrates. This involved the modification of existing experimental systems to characterize responses to magnetic cues in laboratory animals (flies, mice) and the development of novel techniques for studying the role of magnetic cues in the spatial behavior of free-living animals (red foxes). Chapter II examines magnetic orientation in wild-type Drosophila melanogaster larvae. We show that three strains of larvae reared under non-directional ultraviolet (UV) light exhibit quadramodal spontaneous orientation along the anti-cardinal compass directions (i.e. northeast, southeast, southwest, northwest) when tested in a radially symmetrical environment under UV light. Double-blind experiments cancelling the horizontal component of the magnetic field confirmed that the response is dependent on magnetic cues rather non-magnetic features of the test environment. Furthermore, we argue that the larval quadramodal pattern of response is consistent with properties of magnetic compass orientation observed in previous studies of adult Drosophila and laboratory mice, both of which have been proposed to be mediated by a light-dependent magnetic compass mechanism. Chapter III explores the use of novel biologging techniques to collect behavioral and spatial data from free-roaming mammals. Specifically, a previous observational study of free- roaming red foxes found a 4-fold increase in the success of predatory 'mousing' attacks when foxes were facing ~north-northeast, consistent with magnetic alignment responses reported for a range of terrestrial animals. The authors propose that the magnetic field may be used to increase accuracy of mousing attacks. Using tri-axial accelerometer and magnetometer bio-loggers fitted to semi-domesticated red foxes, we created ']magnetic ethograms' from behavioral and magnetic machine learning algorithms 'trained'] to identify three discrete behaviors (i.e. foraging, trotting, and mousing-like jumps) from raw accelerometer signatures and to classify the magnetic headings of mousing-like jumps into 45° sectors from raw magnetometer data. The classifier's ability to accurately identify behaviors from a separate fox not used to train the algorithm suggests that these techniques can be used in future experiments to obtain reliable magnetic ethograms for free-roaming foxes. We also developed the first radio-frequency emitting collar that broadcasts in the low MHz frequency range shown to disrupt magnetic compass responses in a host of animals. The radio-frequency collars coupled with biologgers will provide a powerful tool to characterize magnetic alignment responses in predatory red foxes and can be adapted for use in studies of magnetic alignment and magnetic compass orientation in other free-roaming mammals. Chapter 3 discusses findings from a magnetic nest building assay involving male labratory mice. Mice trained to position nests in one of four directions relative to the magnetic field exhibited both learned magnetic compass responses and fixed magnetic nest positioning orientation consistent with northeast-southwest spontaneous magnetic alignment behavior previously reported for wild mice and bank voles. This is the first mammalian assay in which both learned magnetic compass orientation and spontaneous magnetic alignment were exhibited in the same species, and suggests that the use of magnetic cues in rodents may be more flexible that previously realized.
- Consequences of avian parental incubation behavior for within-clutch variance in incubation temperature and offspring behavioral phenotypesHope, Sydney Frances (Virginia Tech, 2020-01-17)Parents can have large effects on their offspring by influencing the early developmental environment. In birds, a major way that parents can influence the early developmental environment is through egg incubation. Not only is incubation necessary for hatching success, but small changes of <1C in average incubation temperature have large effects on post-hatch offspring morphology and physiology. However, incubation is energetically costly and time-consuming for parents, and thus parents must allocate resources between incubation and self-maintenance. This can lead to differences in parental incubation behavior and egg temperatures among and within populations. Understanding which factors influence incubation, and the subsequent effects for offspring, is crucial for understanding parental effects, non-genetic drivers of phenotypic variation, and how environmental changes affect avian populations. I used wood ducks (Aix sponsa) as a study species to investigate how factors (disturbance, clutch size, ambient temperature) that influence parental demands may affect parental incubation behavior, physiology, and egg temperatures, and subsequently how egg temperatures affect offspring behavior and physiology. In a field experiment, I found that nest disturbance (i.e., capture) reduced both parent prolactin concentrations and the amount of time that parents spent incubating (Chapter 1). Further, ambient temperature was positively and clutch size negatively related to egg temperatures. Notably, in large clutches, differences in average incubation temperature among eggs within nests were large enough (i.e., >1C) to lead to different offspring phenotypes within broods (Chapter 2). Then, in a series of experiments in which I controlled incubation temperature, I provided evidence that lower average incubation temperatures lead to a reduced ability of ducklings to exit the nest cavity (Chapter 3), a more proactive behavioral phenotype (Chapter 4), a smaller body size, and a reduced efficiency in food consumption (Chapter 5), compared to those incubated at higher temperatures. Together, my dissertation illustrates how disturbances, clutch size, and ambient temperature can influence an important aspect of avian parental care, which has wide-ranging effects on offspring traits and fitness. This has broad implications for understanding the evolution of clutch size, development of behavior, and the effects of anthropogenic changes on wildlife.
- Effects of Bird Feeder Density on the Behavior and Ecology of a Feeder-Dependent Songbird: Patterns and Implications for Disease TransmissionAberle, Matthew A. (Virginia Tech, 2018-09-18)Anthropogenic resource provisioning of wildlife has increasingly been hypothesized to alter pathogen spread. Although bird feeding is the most widespread form of intentional wildlife provisioning, we know relatively little about how the degree of anthropogenic feeding at a site impacts wild birds in ways relevant to disease transmission. We manipulated the density of bird feeders (low versus high) available at otherwise similar sites and tracked the local abundance, body condition (scaled-mass index), feeding behavior, and movement across the landscape in wild house finches (Haemorhous mexicanus), a feeder-dependent species subject to outbreaks of a contagious pathogen commonly spread at feeders. The local abundance of house finches was significantly higher at sites with high feeder density but, surprisingly, finches at high-density feeder sites had poorer body condition than those at low-density sites. Behaviorally, birds at high-density feeder sites had longer average feeding bouts and spent more time per day on feeders than birds at low-density feeder sites. Further, birds first recorded at low-density feeder sites were more likely to move to a neighboring high-density feeder site than vice versa. Overall, because local abundance and time spent on feeders have been linked with the risk of disease outbreaks in this species, effects of bird feeder density on both traits may, in turn, influence disease dynamics in house finches. Our results suggest that heterogeneity in the density of bird feeders can have diverse effects on wild birds, with potential consequences for disease transmission.
- Effects of low-density urbanization on genetic structure in the Song SparrowBrewer, Valerie N.; Lane, Samuel J.; Sewall, Kendra B.; Mabry, Karen E. (PLoS, 2020-06-12)Urbanization fragments landscapes and can impede the movement of organisms through their environment, which can decrease population connectivity. Reduction in connectivity influences gene flow and allele frequencies, and can lead to a reduction in genetic diversity and the fixation of certain alleles, with potential negative effects for populations. Previous studies have detected effects of urbanization on genetic diversity and structure in terrestrial animals living in landscapes that vary in their degree of urbanization, even over very short distances. We investigated the effects of low-intensity urbanization on genetic diversity and genetic structure in Song Sparrows (Melospiza melodia). We captured 208 Song Sparrows at seven sites along a gradient of urbanization in and around Blacksburg, VA, USA, then genotyped them using a panel of fifteen polymorphic microsatellite loci. We found that genetic diversity was comparable among the seven study sites, and there was no evidence of genetic structuring among sites. These findings suggest that over a gradient of urbanization characterized by low density urban development, Song Sparrows likely exist in a single panmictic population.
- The evolution of self-controlMacLean, Evan L.; Hare, Brian; Nunn, Charles L.; Addessi, Elsa; Amici, Federica; Anderson, Rindy C.; Aureli, Filippo; Baker, Joseph M.; Bania, Amanda E.; Barnard, Allison M.; Boogert, Neeltje J.; Brannon, Elizabeth M.; Bray, Emily E.; Bray, Joel; Brent, Lauren J. N.; Burkart, Judith M.; Call, Josep; Cantlon, Jessica F.; Cheke, Lucy G.; Clayton, Nicola S.; Delgado, Mikel M.; DiVincenti, Louis J.; Fujita, Kazuo; Herrmann, Esther; Hiramatsu, Chihiro; Jacobs, Lucia F.; Jordan, Kerry E.; Laude, Jennifer R.; Leimgruber, Kristin L.; Messer, Emily J. E.; Moura, Antonio C. de A.; Ostojic, Ljerka; Picard, Alejandra; Platt, Michael L.; Plotnik, Joshua M.; Range, Friederike; Reader, Simon M.; Reddy, Rachna B.; Sandel, Aaron A.; Santos, Laurie R.; Schumann, Katrin; Seed, Amanda M.; Sewall, Kendra B.; Shaw, Rachael C.; Slocombe, Katie E.; Su, Yanjie; Takimoto, Ayaka; Tan, Jingzhi; Tao, Ruoting; van Schaik, Carel P.; Viranyi, Zsoia; Visalberghi, Elisabetta; Wade, Jordan C.; Watanabe, Arii; Widness, Jane; Young, Julie K.; Zentall, Thomas R.; Zhao, Yini (NAS, 2014-04-21)Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.
- Male zebra finches exposed to lead (Pb) during development have reduced volume of song nuclei, altered sexual traits, and received less attention from females as adultsGoodchild, Christopher G.; Beck, Michelle L.; VanDiest, Issac; Czesak, Frankie N.; Lane, Samuel J.; Sewall, Kendra B. (Elsevier, 2021-01-08)Lead (Pb) is a pervasive global contaminant that interferes with sensitive windows for neurological development and causes oxidative damage to tissues. The effects of moderate and high exposure to Pb have been well-studied in birds, but whether low-level early-life exposure to Pb influences adult phenotype remains unclear. Female songbirds use a male’s song and coloration to discriminate between high- and low-quality males. Therefore, if early-life exposure to Pb disrupts song learning ability or shifts the allocation of antioxidant pigments away from colorful secondary sexual traits, male birds exposed to Pb may be less attractive to females. We exposed developing zebra finches (Taeniopygia guttata) to Pb-contaminated drinking water (100 or 1000 parts per billion [ppb]) after hatching (days 0–100). Once male finches reached adulthood (120–150 days post hatch), we measured song learning ability, coloration of bill and cheek patches, and volume of song nuclei in the brain. We also measured female preference for Pb-exposed males relative to control males. Finally, we measured motoric and spatial cognitive performance in male and female finches to assess whether cognitive traits differed in their sensitivity to Pb exposure. Male zebra finches exposed to 1000 ppb Pb had impaired song learning ability, reduced volume of song nuclei, bills with less redness and received less attention from females. Additionally, Pb exposure impaired motoric performance in both male and female finches but did not affect performance in a spatial cognitive task. Adult finches exposed to Pb-contaminated water had higher blood-Pb levels, though in all cases blood-Pb levels were below 7.0 μg dL⁻¹. This study suggests that low-level exposure to Pb contributes to cognitive deficits that persist into adulthood and may indirectly influence fitness by altering secondary sexual traits and reducing male attractiveness.
- The Mouse Magnetic CompassArnold, Tessa Jean (Virginia Tech, 2015-06-26)All five classes of vertebrates use the geomagnetic field for spatial orientation. The geomagnetic field can be used to derive both 'map' and 'compass' information. There is evidence for two different mechanisms used to sense the magnetic field, the radical pair mechanism (RPM) and the magnetite based mechanism (MBM). C57BL/6 laboratory mice can rely on directional information from the magnetic field to position their nests and to solve a water maze task. The primary objective of this research was to characterize the magnetic compass of C57BL/6 laboratory mice in the plus water maze task. These experiments explored sources of variation in magnetic responses and investigated the underlying magnetic compass orientation mechanism in C57BL/6 mice. The results provide evidence that the mouse magnetic compass is sensitive to low-level radiofrequency fields, consistent with the use of the RPM for magnetic orientation. Surprisingly, the results also suggest that C57BL/6 mice have a polarity sensitive compass, consistent with the use of a MBM for magnetic orientation. These experiments confirm that mice have a specialized magnetic compass sense. Furthermore, despite the controlled environment in which these laboratory experiments were conducted, a variety of factors can increase the variability in the response. Future experiments are needed to further characterize the mouse magnetic compass, as there is a possibility of a hybrid magnetic response where both magnetoreception mechanisms could be used for spatial orientation.
- Phenotypic Responses to Invasion in the Brown Anole (Anolis sagrei)Fetters, Tamara Lynn (Virginia Tech, 2020-01-17)Invasive species often encounter climatic conditions that differ significantly from those of their native range. These environmental shifts may trigger phenotypic responses, resulting through some combination of adaptation and plasticity, that enable the invader to persist under novel thermal regimes. In this dissertation, I examine phenotypic changes in a tropical lizard that has successful invaded a cooler temperate climate, specifically examining traits that may promote survival and reproduction in their new range. First, I examined physiological traits, as I predicted greater cold tolerance would be necessary to survival in the invasive range. I found that invasive populations tolerated lower temperatures, exhibited greater maximum sprint speeds, and had higher metabolic rates than native populations. Next, I examined how life-history traits may change in the invasive range in order to facilitate reproduction under shorter breeding and growing seasons. I found that compared to native females, invasive females had shorter interlaying intervals and produced eggs that hatched more quickly. Once I quantified changes physiological and life-history traits that may have aided in successful establishment, I executed a common garden study to determine whether changes were the result of adaptation or plasticity. I found that differences in critical thermal minimum, metabolic rate, interlaying interval, and incubation period were maintained in lab-reared offspring, while measures of sprint speed converged. My results provide evidence that life history and physiology can evolve rapidly during invasion. These findings are useful to understanding contemporary evolution, and also provide valuable insight on how species respond to environmental shifts, both during invasions and as a result of climate change.
- A Proximate Perspective on the Cooperative Behavior of a Lekking PasserineVernasco, Ben Joseph (Virginia Tech, 2019-09-18)Elucidating the mechanisms responsible for driving individual variation in behavior is a foundational question in organismal biology. Answering these types of questions is necessary for understanding how tradeoffs are mediated as well as potential constraints on evolutionary responses to selection. In Chapter I, I synthesize the evidence suggesting that testosterone plays a central role in driving individual variation in cooperative reproductive behaviors and mediating the tradeoff between cooperation and competition. The subsequent chapters of my dissertation then focus on understanding the mechanistic sources of individual variation in the cooperative courtship behaviors of male wire-tailed manakins (Pipra filicauda), a Neotropical lekking songbird. Wire-tailed manakins exhibit cooperative courtship display behaviors wherein both floater and territory-holding males perform coordinated courtship displays. Territory-holding males sire essentially all offspring and, among territory-holders, those that are more cooperative exhibit higher reproductive success. Cooperation also benefits floater males in that more cooperative floater males have a higher probability of becoming a territory-holder. In Chapter II, I detail the difficulties associated with measuring circulating testosterone in free-living animals and develop a new field technique that can improve our ability to accurately account for the effects that the stress of capture has on circulating testosterone levels in birds. In Chapter III, I quantify individual variation in the cooperative courtship behaviors of territory-holding male wire-tailed manakins using video cameras. I then use both observational and experimental approaches to show that among territory holders, high testosterone has antagonistic effects on a male's cooperative behavior. Chapter IV focuses on quantifying how an individual's cooperative behavior relates to their telomere length. Telomeres are the segments of repetitive DNA found at the end of chromosomes. Telomeres shorten in response to both physiological and environmental perturbations, are predictive of an individual's mortality risk and, because of these characteristics, are thought to reflect an individual's biological age (as opposed to chronological age). My results show that short telomeres are associated with increased cooperative behaviors and, given that a male's cooperative behavior is reflective of their reproductive investment, suggest that males with lower future reproductive potential (i.e., shorter telomeres) invest more in reproduction. My last chapter (Chapter V) focuses on synthesizing these results and suggests that future research on cooperative behaviors will need to integrate biomarkers of an individual's condition with mechanisms that reflect an individual's social competence to further understand the sources of individual variation in cooperation.
- Song Competition Affects Monoamine Levels in Sensory and Motor Forebrain Regions of Male Lincoln's Sparrows (Melospiza lincolnii)Sewall, Kendra B.; Caro, Samuel P.; Sockman, Keith W. (PLOS, 2013-03-26)Male animals often change their behavior in response to the level of competition for mates. Male Lincoln's sparrows (Melospiza lincolnii) modulate their competitive singing over the period of a week as a function of the level of challenge associated with competitors' songs. Differences in song challenge and associated shifts in competitive state should be accompanied by neural changes, potentially in regions that regulate perception and song production. The monoamines mediate neural plasticity in response to environmental cues to achieve shifts in behavioral state. Therefore, using high pressure liquid chromatography with electrochemical detection, we compared levels of monoamines and their metabolites from male Lincoln's sparrows exposed to songs categorized as more or less challenging. We compared levels of norepinephrine and its principal metabolite in two perceptual regions of the auditory telencephalon, the caudomedial nidopallium and the caudomedial mesopallium (CMM), because this chemical is implicated in modulating auditory sensitivity to song. We also measured the levels of dopamine and its principal metabolite in two song control nuclei, area X and the robust nucleus of the arcopallium (RA), because dopamine is implicated in regulating song output. We measured the levels of serotonin and its principal metabolite in all four brain regions because this monoamine is implicated in perception and behavioral output and is found throughout the avian forebrain. After controlling for recent singing, we found that males exposed to more challenging song had higher levels of norepinephrine metabolite in the CMM and lower levels of serotonin in the RA. Collectively, these findings are consistent with norepinephrine in perceptual brain regions and serotonin in song control regions contributing to neuroplasticity that underlies socially-induced changes in behavioral state.
- Two Neural Measures Differ between Urban and Rural Song Sparrows after Conspecific Song PlaybackSewall, Kendra B.; Davies, Scott (Frontiers, 2017-05-17)Urbanization is a critical form of environmental change that can affect the physiology and behavior of wild animals and, notably, birds. One behavioral difference between birds living in urban and rural habitats is that urban males show elevated boldness or territorial aggression in response to simulated social challenge. This pattern has been described in several populations of song sparrow, Melospiza melodia. Such behavioral differences must be underpinned by differences in the brain, yet little work has explored how urbanization and neural function may be interrelated. We explored the relationship between urbanization and neural activation within a network of brain regions, collectively called the social behavior network, which contributes to the regulation of territorial aggression. Specifically, we captured free-living, territorial male song sparrows by playing them conspecific songs for 6-11 min, and then collected their brains. We estimated recent neural activation, as indicated by the immediate early gene FOS, and measured levels of a neuropeptide, arginine vasotocin (AVT), which is involved in the regulation of social behavior. Based on previous studies we expected urban males, which are generally more territorially aggressive, to have lower FOS expression in a node of the social behavior network implicated in regulating territoriality, the lateral septum (LS). Additionally, we expected urban males to have lower AVT expression in a brain region involved in the regulation of sociality, the medial bed nucleus of the stria terminalis (BSTm). We found that, compared to rural males, urban male song sparrows did have lower FOS expression in the LS. This pattern suggests that lower neural activation in the LS could contribute to behavioral adjustments to urbanization in male song sparrows. Additionally, counter to our predictions, urban male song sparrows had higher AVT-like immunoreactivity in the BSTm. Future work building upon these findings is needed to determine the causal role of such neural differences across rural and urban habitats. Understanding the mechanisms impacted by urbanization will inform our understanding of the reversibility and consequences of this form of habitat change.
- Variation in Hematological Indices, Oxidative Stress, and Immune Function Among Male Song Sparrows From Rural and Low-Density Urban HabitatsGoodchild, Christopher G.; VanDiest, Isaac; Lane, Samuel J.; Beck, Michelle; Ewbank, Hallum; Sewall, Kendra B. (Frontiers, 2022-02-16)A central theme in the field of ecology is understanding how environmental variables influence a species' distribution. In the last 20 years, there has been particular attention given to understanding adaptive physiological traits that allow some species to persist in urban environments. However, there is no clear consensus on how urbanization influences physiology, and it is unclear whether physiological differences in urban birds are directly linked to adverse outcomes or are representative of urban birds adaptively responding to novel environmental variables. Moreover, though low-density suburban development is the fastest advancing form of urbanization, most studies have focused on animals inhabiting high intensity urban habitats. In this study, we measured a suite of physiological variables that reflect condition and immune function in male song sparrows (Melospiza melodia) from rural and suburban habitats. Specifically, we measured hematological indices [packed cell volume (PCV), hemoglobin concentration, mean corpuscular hemoglobin concentration (MCHC)], circulating glutathione (total, reduced, and oxidized), oxidative damage (d-ROM concentration), antioxidant capacity, and components of the innate immune system [bacteria killing ability (BKA), white blood cell counts]. We also measured whole-animal indices of health, including body condition (scaled mass index length) and furcular fat. Song sparrows inhabiting suburban environments exhibited lower hemoglobin and MCHC, but higher body condition and furcular fat scores. Additionally, suburban birds had higher heterophil counts and lower lymphocyte counts, but there were no differences in heterophil:lymphocyte ratio or BKA between suburban and rural birds. PCV, glutathione concentrations, and oxidative damage did not differ between suburban and rural sparrows. Overall, suburban birds did not exhibit physiological responses suggestive of adverse outcomes. Rather, there is some evidence that sparrows from rural and suburban habitats exhibit phenotypic differences in energy storage and metabolic demand, which may be related to behavioral differences previously observed in sparrows from these populations. Furthermore, this study highlights the need for measuring multiple markers of physiology across different types of urban development to accurately assess the effects of urbanization on wildlife.