24 Sep 2010: Caitlin Barale
A networks approach to sheep movement and leadership
Social network analysis is a tool that has only recently been applied to animal behavior. It is a powerful way to identify influential individuals and examine assocations between peers, and to assess things like the strength and direction of relationships. In this project, we examine two aspects of sheep behavior - leadership in group movement and subgroup associations - using SNA.
1 October 2010: Christie Riehl
Why are robins' eggs blue? Sexual selection and the evolution of conspicuous eggshell coloration
The adaptive significance of brightly colored avian eggs has interested evolutionary biologists since Alfred Russell Wallace. A number of different factors have been proposed to explain the evolution of conspicuous eggshell coloration, including thermoregulation, camouflage, increased visibility to cavity-nesting parents, avoidance of brood parasitism, and protection against solar radiation. However, the explanation that has received the most attention in the past decade is the "sexually selected" hypothesis, which posits that the pigments responsible for the blue-green coloration of avian eggs is costly for females to produce, and may therefore serve as a reliable indicator of a female's genetic quality. If so, males should be able to judge the genetic fitness of their mates by the intensity of the coloration of the eggshell, and to adjust their investment in the clutch accordingly. Since the publication of this hypothesis in 2003, there has been a flurry of experimental studies aimed at testing whether the intensity of eggshell coloration does, in fact, predict paternal investment. In this talk, I'll review the evidence in support of this hypothesis. I will argue that the majority of empirical studies have used a flawed experimental design, leading to sloppy reasoning and inaccurate results. I will also question the fundamental assumptions of the sexually selected hypothesis, including the heritability of fine-scale differences in eggshell coloration and the relationship between paternal care and offspring quality.
8 October 2010: Patrick Onyango
There are major gaps in our knowledge of the extent of tradeoffs between
mating effort and paternal care among mammalian males. These
reproductive tradeoffs can arise from resource and/or temporal
constraints. I investigated potential conflict between mating effort and
paternal care in male baboons by examining male sociosexual behaviors
within a specific context of mating called mate-guarding episode that is
a common characteristic of many cercopitherines including savanna
baboons. I used a predictive framework that integrated energetic
constraints, female reproductive quality, male dominance rank, and the
number of immature offspring a male had in the group to evaluate
conflict in investment between mating and paternal care. I will present
results of this study and I look forward to a wonderful discussion.
15 October 2010: Henry Horn
Social butterflies: Simple rules and complex behavior in the field and in NetLogo models - a preliminary report and prospectus
Mate-finding behavior in butterflies spans a range like that in vertebrates, from random vagrant encounters through territorial defense of resources that attract females. I am trying to discover
simple sensory cues and behavioral rules by which butterflies might organize such seemingly
complex behaviors. My talk will present pretty pictures, behavioral observations, and adaptive
interpretations for two species, the Plain Ringlet (Coenonympha tullia inornata) and the
Pearly Eye (Enodia anthedon). I shall reinterpret the behaviors at a mechanistic level, first
with informal verbal models, and then with somewhat more formal models using the NetLogo
computer language, beloved of lecturers at the Santa Fe Institute. These preliminary formal
models give surprisingly realistic caricatures of some behaviors of butterflies in the field, and
they help to generate plans for further explorations. I am also interested in the consequences of
differences in behavior for the ecology of local populations, but that is another story.
22 October 2010: Jenny Ouyang
Fear and stress: How parental response to novelty and perceived nest predation risk vary with corticosterone levels in temperate and tropical birds
Temperate and tropical birds differ in life-history traits which may be a result of regional differences in levels of ecological plasticity. Neophobia, a fear response to a novel stimulus, is an example of a plastic behavior that can be readily modified in response to variation within the environment. Recently, it has been suggested that how readily an organism responds to novelty is correlated with its physiological phenotype, namely, the stress response. However, to date, no studies have looked at neophobic behaviors across a latitudinal gradient with varying environmental characteristics nor have any studies correlated levels of neophobia with measurements of stress. We examined behavioral differences between temperate and tropical birds, captured individuals of the same species to assess baseline and stress-induced corticosterone concentrations, and followed them to assess life-history traits. We found that temperate species with the highest stress-induced corticosterone levels showed the lowest intensity of response to an intruder; moreover, after the placement of a novel object, both temperate and tropical species with the highest stress-induced corticosterone level were the slowest to return to normal behavior. Furthermore, survival rates were higher in the tropics than in the temperate region and the highest survival rates were correlated with species exhibiting a high corticosterone response and high neophobic behavior. These findings suggest that birds living in different environments differ in behavioral phenotypes that may be mediated by a specific physiological pathway, accumulating to functional significance in their survival capabilities.
29 October 2010: Cassandra Nunez
Wild horses subject to different management regimes demonstrate significant variation in their behavior-- those subject to more invasive techniques are more likely to demonstrate fundamental changes to their behavioral ecology and reproductive biology. The question is then, can these "dysfunctional" animals learn normal behavior from unmanaged, "functional" animals? I will propose two experiments that are designed to help answer this question. The answers to questions like these are important to the future of wild horses, particularly those in the western United States. As a behaviorist (i.e. not an experimentalist), I would really appreciate your ideas and feedback on experimental design, potential pitfalls, proper controls, etc.
19 November 2010: Andrew Gallup
Contagious yawning in birds? An observational study in budgerigars (Melopsittacus undulatus)
Yawning is a widely expressed, stereotyped phenomenon occurring in all classes of vertebrates, but contagious yawning has only been observed in humans and a few other primate species. Contagious yawning has recently been linked to empathy and is speculated to serve a communicative role. To better understand the comparative nature of contagious yawning, an observational study was conducted in budgerigars (Melopsittacus undulatus), a highly social, flock-living, small parrot. Flock-housed budgerigars were videotaped for 1.5 hours at three times during the day (early morning, afternoon and early evening), and the times of all yawns and stretches for each bird were recorded. Both yawning and stretching were significantly clumped and this does not appear to be a result of a similar circadian pattern, suggesting that they may be contagious. Functionally, contagious yawning and stretching may help coordinate activity and arousal in this flock-living bird, promoting group vigilance and preparation for flight. This account provides the first support for contagious yawning in a non-primate species, but experimental evidence is needed to confirm these findings.
3 December 2010: David Pattemore
Does compensation maintain ecosystem function in the face of species extinctions? A case study from pollination systems in New Zealand
Global declines in the abundance and diversity of pollinators are predicted to adversely affect pollination as a key ecosystem function and service. While compensation has been suggested as a stabilizing process to maintain overall ecosystem function on an inter-annual timescale, most broad theoretical considerations of pollinator extinctions ignore the role that compensation could play in maintaining pollination. The almost complete loss of a guild of vertebrate pollinators from forests in northern New Zealand provides a natural experiment to test whether compensation can maintain pollination despite the local extinction of pollinators. We compared the pollination of three plant species on Little Barrier Island, which has an intact endemic vertebrate pollinator fauna, to populations in depauperate forests on the adjacent North Island. Here we show that invasive Ship rats (Rattus rattus) and recent-colonist Silvereyes (Zosterops lateralis) are partially or fully maintaining pollination in the absence of endemic bat and bird pollinators. This is evidence that compensation by novel species can be an important stabilizing process for ecosystem function following the extinction of endemic species. The role of these novel species in maintaining ecosystem function implies that care should be taken when managing invaded forest systems.
10 December 2010: Salvador Jorgensen
Philopatry and migration of Pacific white sharks
Advances in electronic tagging and genetic research are making it possible to discern population structure for pelagic marine predators once thought to be panmictic. However, reconciling migration patterns and gene flow to define the resolution of discrete population management units remains a major challenge, and a vital conservation priority for threatened species such as oceanic sharks. Many such species have been flagged for international protection, yet effective population assessments and management actions are hindered by lack of knowledge about the geographical extent and size of distinct populations. Combining satellite tagging, passive acoustic monitoring and genetics, we reveal how eastern Pacific white sharks (Carcharodon carcharias) adhere to a highly predictable migratory cycle. Individuals persistently return to the same network of coastal hotspots following distant oceanic migrations and comprise a population genetically distinct from previously identified phylogenetic clades. We hypothesize that this strong homing behaviour has maintained the separation of a northeastern Pacific population following a historical introduction from Australia/New Zealand migrants during the Late Pleistocene. Concordance between contemporary movement and genetic divergence based on mitochondrial DNA demonstrates a demographically independent management unit not previously recognized. This population's fidelity to discrete and predictable locations offers clear population assessment, monitoring and management options.