office: KINSC L103
Haverflock: flocking research at Haverford
We are studying collective animal behavior with a focus on the way flocking is deployed in predator-prey relationships. [For background and some exciting videos, see the pioneering STARFLAG group's website.-] In past summers, we've obtained and analyzed data on a phenomenon called mobbing, whereby smaller prey animals (in our case,barn swallows and terns) harass and attack a larger predator (primarily raptors such as the red-tailed hawk or osprey ).  We have used particle-tracking methods and statistical analyses to understand and model the dynamical rules governing this behavior.
|European starling mobbing a red-tailed hawk on Haverford College's campus|
Why study collective animal behavior? In addition to its intrinsic interest, flocking has been studied to enable us to understand and identify universal features of collective behavior in general (such as financial markets, traffic and human crowds during evacuations), to model the motion of animals in CGI, and to avoid collisions between bird flocks and airplanes. Collective animal behavior provides a laboratory for understanding the way cooperation factors into evolution; models have shown that flocking can reduce the risk to individuals from predators on average, or that cooperating with other fish reduces the risk during inspection of a predator, for example.
We are interested in mobbing in particular because it presents an intriguing case of nonintuitive behavior whose evolutionary origins are uncertain. What drives smaller prey birds to seemingly enhance their risk of predation by confronting a predator at close range? Do their attacks take advantage of strategies that deter the predator while avoiding the most likely scenarios of attack? How do the trajectories of mobbing birds coordinate with their characteristic mobbing cries? Mobbing attacks take place in groups ranging from individuals to small flocks of a dozen or more birds, with the average number found to be around six. How do mobbing attack strategies depend upon the number of mobbers?
(left) Actual trajectory data for a barn swallow mobbing a predator model similar in size to native accipeters such as Cooper's Hawks. (right) Computer animation combining actual prey flight trajectories with simulated predator pursuit.
Methods We make our observations around Haverford's 216-acre campus and Arboretum, as well as at various local bird refuges and nature reserves including at the New Jersey Shore in Cape May. We film mobbing incidents in the wild between actual passerines and predators, as well as experiments using model predators. (Earlier studies have shown that mobbing can be induced by using a taxidermy predator as a target near a passerine roosting site -.) Our field data consists of stero images recorded on two high-def 30 fps progressive scan Canon Vixia HF-200 digital video cameras precisely positioned and aimed so as to provide stereo images of our experimental subjects. We analyze these using the image analysis package Sigmascan, ImageJ, OpenCV and our lab's custom python tracking and stereo analysis code to provide 3D video of mobbing attacks. Finally, we use computer simulations code to model our flight trajectory data and to understand how various strategies relate to questions about hypothesized goals of the observed behavior.
(left) Elias Tousley setting up stereo video at the New Jersey Shore and (right) hiking and observing raptors with Emily Cunningham on Hawk Mountain.
2011-2012 This academic year we have constructed and tested out our new acoustic localization system hardware and software to accompany our 3D stereometric video studies. This will allow us to record bird calls and associate them with the higher-spatial-resolution flight trajectories of individual birds. We will use this new approach to delineate how different individuals play roles in their flock by adding communnications networks to video data in flocking studies. Students Marjon Zamani and Emma Oxford traveled with me to the Sierra Nevadas for the Cornell Bioacoustics Research Group's Sound Recording Workshop to learn about these new experimental tools. We then assembled and tested out our microphone array here at Haverford, and analyze our data with bioacoustics software (RAVEN Pro) from the Cornell Bioacoustic group. We will continue our flocking studies, but now employing the microphone array and robotic predators to be constructed this summer (this will enable us to study a wider variety of behavior and better control the experimental parameters of our studies.) This year we also established collaborations with teams of falconers in the U.S. and E.U. who are testing out miniature "BirdCam's": backpack mounted videocameras that can be mounted on raptors to collect video of their field of view during hunts; we are deploying these in the field along with microsensor arrays to understand raptor hunting strategies.
|Collaborators: Charlotte Hemelrijk, Behavioural Ecology and Self-Organization, University of Groningen, the Netherlands|
|Hanno Hildenbrandt, Behavioural Ecology and Self-Organization, University of Groningen, the Netherlands|
M. Elias Tousley (Haverford Physics '11) worked on this project since its inception; his senior thesis project involved taking the swallow-raptor and tern mobbing data, writing code, doing data analysis and helping create our experimental setup.
|Emily Cunningham (Physics '12) wrote our simulation code and took tern mobbing data in summer 2009.|
|Anna Schall (Physics '12) worked during fall '09 to analyze online videos of crows mobbing various predators|
|Owen Glaze (a '09 graduate of Lower Merion High School) performed research in summer 2009 before attending Penn State's main campus in the fall. Owen wrote much of the image analysis code and took the swallow-raptor data with Elias.|
|Marjon Zamani (Physics '13) co-wrote our local ImageJ tracking userguide and performed experiments on using video and bioacoustic methods in summer 2011|
|Emma Oxford (Physics '13) co-wrote our Raven Pro supplementary userguide and helped develop our bird-mounted GPS and other sensors.|
- STARFLAG website
- Physics Today article on bird flocking & the STARFLAG group
- Interaction Ruling Animal Collective Behaviour Depends on Topological rather than Metric Distance: Evidence from a Field Study PNAS, 105, 1232-1237 (2008) (free download).
- An empirical study of large, naturally occurring starling flocks: a benchmark in collective animal behaviour
Animal Behaviour 76, 201-215 (2008). Here is the Preprint version
- The STARFLAG handbook on collective animal behaviour: Part I, empirical methods Animal Behaviour 76, 217-236 (2008). Here is the Preprint version
- The STARFLAG handbook on collective animal behaviour: Part II, three-dimensional analysis Animal Behaviour 76, 237–248 (2008). Here is the Preprint version
- New statistical tools for analyzing the structure of animal groups, Mathematical Biosciences 214, 32-37 (2008).
- Collective behavior in animal groups: theoretical models and empirical studies, HFSP Journal 2, 205-219 (2008).
- Roni Ostreiher, "Is mobbing altruistic or selfish behaviour?", Animal Behaviour, Volume 66, Issue 1, July 2003, Pages 145-149, ISSN 0003-3472, DOI: 10.1006/anbe.2003.2165. (http://www.sciencedirect.com/science/article/B6W9W-48FSV4T-7/2/cc5318bf3e76a0a15b47f0a2cf1f50c5)
- Hendrichsen, DK; Christiansen, P; Nielsen, EK, et al., Exposure affects the risk of an owl being mobbed - experimental evidence, Hendrichsen, DK; Christiansen, P; Nielsen, EK, et al.
Journal Of Avian Biology, Volume 37, Issue 1, Pages 13-18, Jan. 2006
- Mark T. Nolen, Jeffrey R. Lucas, Asymmetries in mobbing behaviour and correlated intensity during predator mobbing by nuthatches, chickadees and titmice, Animal Behaviour, Volume 77, Issue 5, May 2009, Pages 1137-1146, ISSN 0003-3472, DOI: 10.1016/j.anbehav.2009.01.023. (http://www.sciencedirect.com/science/article/B6W9W-4VRWNNM-3/2/61330586040906cd3a12ca2d64d84f47)
A Biophysical Model of Prokaryotic Diversity in Geothermal Hot Springs
Physics majors Anna Klales '09 (Harvard PhD program), Jim Duncan ’03 (Oregon State Geosciences PhD program) and Liz Janus Nett'04 (U. Wisconsin PhD program)
Photosynthetic bacteria living in geothermal hot spring environments have surprisingly complex ecosystems with an unexpected level of genetic diversity. In particular, their thermal gradients support genetically distinct bacterial strains that differ in their preferred temperatures for reproduction and photosynthesis. Each region along the thermal gradient exhibits multiple strains of photosynthetic bacteria adapted to several distinct thermal optima, rather than the expected single thermal strain adapted to the local environmental temperature. Here we analyze microbiology data from several ecological studies to show that the thermal distribution field data exhibit several universal features independent of location and specific bacterial strain. These include the distribution of optimal temperatures of different thermal strains and the functional dependence of the net population density on temperature. We present a simple population dynamics model of these systems that explains the observed diversity of different strains of the photosynthetic bacteria, the observed thermal population distributions and certain features of population dynamics observed in laboratory studies of the same organisms.
Anna Klales, James Duncan, Elizabeth Janus Nett, and Suzanne Amador Kane, "A biophysical model of prokaryotic diversity in geothermal hot springs" http://arxiv.org/abs/0808.1134?context=q-bio.PE
Previous Research Topics
Molecular wire fabrication and characterization: entropic ordering & hybrid quantum dot/organic chemical structures
David Burkhardt (Physics '07), Lindsay Subers (Physics '06) & Adolphe Alexander (Physics '05)
Mechanical Measurements of Biopolymers (AFM studies & modeling of synthetic proteins)
with Rob Fairman, Karl Johnson (Biology), Rob Manning (Math), Walter Smith (Physics), and Haverford students Theresa Horne ('03), Carl Lederman (Math '05) and Eric Acton (Math '05)
Daniel J. Rigotti, Bashkim Kokona, Theresa Horne, Eric K. Acton, Carl D. Lederman, Karl A. Johnson, Robert S. Manning, Suzanne Amador Kane, Walter F. Smith and Robert Fairman, "Quantitative atomic force microscopy image analysis of unusual filaments formed by the Acanthamoeba castellanii myosin II rod domain" Analytical Biochemistry, 346(2), 2005, pp. 189-200