Nicholas Brandley

 Nicholas Brandley

Nicholas C. Brandley

  • Courses6
  • Reviews9

Biography

Colorado College - Biology


Resume

  • 2009

    Doctor of Philosophy (PhD)

    Biology

    Duke University

  • 2004

    Bachelor of Science (BS)

    Ecology and Evolutionary Biology

    University of Michigan

  • Animal Communication

    Animal Behavior

    College Teaching

    Sensory Ecology

    Physiology

    Biology

    Python

    Eavesdropping on Visual Secrets

    Sonke Johnsen

    Daniel Speiser

    Private communication may benefit signalers by reducing the costs imposed by potential eavesdroppers such as parasites

    predators

    prey

    or rivals. It is likely that private communication channels are influenced by the evolution of signalers

    intended receivers

    and potential eavesdroppers

    but most studies only examine how private communication benefits signalers. Here

    we address this shortcoming by examining visual private communication from a potential eavesdropper’s perspective. Specifically

    we ask if a signaler would face fitness consequences if a potential eavesdropper could detect its signal more clearly. By integrating studies on private communication with those on the evolution of vision

    we suggest that published studies find few taxon-based constraints that could keep potential eavesdroppers from detecting most hypothesized forms of visual private communication. However

    we find that private signals may persist over evolutionary time if the benefits of detecting a particular signal do not outweigh the functional costs a potential eavesdropper would suffer from evolving the ability to detect it. We also suggest that all undetectable signals are not necessarily private signals: potential eavesdroppers may not benefit from detecting a signal if it co-occurs with signals in other more detectable sensory modalities. In future work

    we suggest that researchers consider how the evolution of potential eavesdroppers’ sensory systems influences private communication. Specifically

    we suggest that examining the fitness correlates and evolution of potential eavesdroppers can help (1) determine the likelihood that private communication channels are stable over evolutionary time

    and (2) demonstrate that undetectable signals are private signals by showing that signalers benefit from a reduction in detection by potential eavesdroppers.

    Eavesdropping on Visual Secrets

    The iconic red hourglass of the black widow spiders (genus Latrodectus) is traditionally considered an aposematic signal

    yet experimental evidence is lacking. Here

    we present data that suggest that black widow coloration may have evolved to be an aposematic signal that is more conspicuous to their vertebrate predators than to their insect prey. In choice experiments with wild birds

    we found that the red-and-black coloration deters potential predators: Wild birds were ~3 times less likely to attack a black widow model with an hourglass than one without. Using visual-system appropriate models

    we also found that a black widow’s red-and-black color combo is more apparent to a typical bird than a typical insect. Additionally

    an ancestral reconstruction reveals that red dorsal coloration is ancestral in black widows and that at some point some North American widows lost their red dorsal coloration. Behaviorally

    differences in red dorsal coloration between 2 North American species are accompanied by differences in microhabitat that affects how often a bird will view a black widow’s dorsal region. All observations are consistent with a cost–benefit trade-off of being more conspicuous to predators than to prey. We suggest that limiting detection by prey may help explain why red and black aposematic signals occur frequently in nature.

    Aposematic signals in North American black widows are more conspicuous to predators than to prey

    The information an animal gathers from its environment

    including that associated with signals

    often varies continuously. Animals may respond to this continuous variation in a physical stimulus as lying in discrete categories rather than along a continuum

    a phenomenon known as categorical perception. Categorical perception was first described in the context of speech and thought to be uniquely associated with human language. Subsequent work has since discovered that categorical perception functions in communication and decision-making across animal taxa

    behavioral contexts

    and sensory modalities. We begin with an overview of how categorical perception functions in speech perception and

    then

    describe subsequent work illustrating its role in nonhuman animal communication and decision-making. We synthesize this work to suggest that categorical perception may be favored where there is a benefit to 1) set-ting consistent behavioral response rules in the face of variation and potential overlap in the physical structure of signals

    2) especially rapid decision-making

    or 3) reducing the costs associated with processing and/or comparing signals. We conclude by suggesting other systems in which categorical perception may play a role as a next step toward understanding how this phenomenon may influence our thinking about the function and evolution of animal communication and decision-making.

    Categorical perception in animal communication and decision-making

    We document a previously undescribed vocalisation in the Variegated Fairy-wren (Malurus lamberti)

    the Type II song

    which is given in response to the calls of a specific avian predator. We used playbacks of five species of both predators and non-predators to determine which species most commonly elicit Type II songs. Calls of Grey Butcherbirds (Cracticus torquatus) were the only stimuli to elicit Type II songs. Two other species in the genus Malurus

    the Splendid Fairy-wren (M. splendens) and the Superb Fairy-wren (M. cyaneus)

    are also known to sing Type II songs in response to the calls of specific avian predators. In all these species

    Type II songs may function as displays to conspecifics. This study highlights the possibility that predator-elicited display behaviour may be more widespread in the genus Malurus than was previously recognised.

    A predator-elicited vocalisation in the Variegated Fairy-wren (Malurus lamberti)

    Visual acuity (VA) --- a measurement of the fineness or coarseness of vision --- correlates with the size of an animal

    with larger species often possessing sharper vision. However

    it is unknown whether the same relationship between visual acuity and size holds within a species when individuals differ consistently and substantially in size

    such as through a sexual size dimorphism. Here we examine the visual acuity of three species of sexually dimorphic band-winged grasshoppers

    in which females are the larger sex (Arphia pseudonietana

    Dissosteira carolina

    and Spharagemon equale; total n = 98). Using a radius of curvature estimation method

    we find that females have ∼21% finer vision in the most acute region and axis of the eye than do males. Further explorations of the eyes of the species showing the greatest size dimorphism (D. carolina) suggest that this VA dimorphism is driven by females having larger eyes with more ommatidia. In contrast to many flying insects where males have finer vision to acquire mates

    our study is one of the first to demonstrate a female-biased sexual dimorphism in acuity. Given the number of species in which females are larger than males

    our results suggest that differences in VA between the sexes may be more common than currently appreciated.

    A sexual dimorphism in the spatial vision of band-winged grasshoppers (in review)

    The many dimensions of categorical perception: a response to comments on Green et al.

    The many dimensions of categorical perception: a response to comments on Green et al.

    Acuity

    the fineness with which sensory systems perceive and parse information

    limits the information that organisms can extract from stimuli. Here

    we focus on visual acuity (the ability to perceive static spatial detail) to discuss relationships between acuity and signal form and evolution. Research suggests that acuity varies by orders of magnitude across species

    and that most animals have much lower acuity than humans. Thus

    hypotheses regarding the function of spatial patterns must account for the acuity of relevant viewers. New data quantifying acuity in a range of taxa allow us to examine correlations between acuity and ecology

    elucidate the selective forces that receiver acuity places on signal evolution

    and examine how signals might appear to viewers with different acuities.

    Visual acuity and the evolution of signals

    My research falls within the intersection of ecology

    behavior

    and sensory physiology. Broadly

    I seek to understand how differences in vision influence the behavior and coloration of animals. To accomplish this I investigate both 1) how different behavioral

    ecological

    and morphological factors cause variation in vision between animals and 2) what functional effect these differences have on the animal’s behavior and ecology. My work includes projects in visual acuity (i.e. spatial vision; informally the number of pixels in an animal’s visual scene)

    color vision

    and synthesis papers examining how physiology influences behavior.

    Nicholas

    Elon University

    The College of Wooster

    Duke University

    Duke University

    Colorado College

    NC Governor's School East

    Elon University

    University of Michigan Biological Station

    Human Physiology Lecture (1 section)

    Elon University

    Colorado College

    Colorado Springs

    Colorado Area

    Visiting Assistant Professor

    Raleigh

    NC

    Residential summer school for gifted rising high school seniors.

    Natural Science Instructor

    NC Governor's School East

    Adviser: Dr. Sönke Johnsen\nDepartment of Biology

    Duke University

    Teaching Assistant

    Natural History and Evolution (1 section)

    University of Michigan Biological Station

    Assistant Professor

    The College of Wooster

    Lab Instructor

    Human Physiology (2 sections)

    Elon University

    Summer Term Instructor

    Intensive summer course in animal adaptations.

    Duke University

    The College of Wooster

    Wooster

    OH

    Visiting Assistant Professor

BE 106

4.5(2)

BE 440

4.8(2)

BIO 106

4.5(1)