Project: Biogeographic study of Southern Resident Killer Whale (SRKW) behavior in the Salish Sea
The purpose of this biogeography study is to determine if group spatial structure (cohesion), as defined by the distance between group members (contact, tight, loose, spread), of SRKWs changes in response to variables such as bathymetry (underwater topography), currents, season, day of the week, and number of vessels; and to establish whether the responses and variables vary geographically. One component of the study will assess whether vessel density, the mode of vessel operation, and the distance to the whales affect the whales’ cohesion and/or activity state. Group cohesion is a spatial and temporal assertion of social structure (Mann 2000). Research shows these animals to be highly social (Heimlich-Boran, S.L. 1986, Hoelzel, A.R., and Osborne, R.W. 1986); if group cohesion is disrupted their ability to communicate, forage, and move through their environment may be impaired, which may ultimately limit their overall fitness and survivability.
Our objectives are to address the following hypotheses:
The spatial structure of SRKW groups does not change with
different behavior states (resting, traveling, foraging,
socializing). Testing the first hypothesis helps establish
the stability of standardized SRKW behavioral states relative
to the spatial structure parameters measured in this study.
This project utilizes an integrated equipment package which includes a global positioning system (GPS) with built-in data collector to record attribute data (e.g. whale identification, group size, and behaviors), a laser rangefinder to determine distance, and a compass for bearing. These components are connected and synchronized to generate geo-referenced data for focal whales and vessels. Two equipment packages are used to collect data simultaneously, one for collecting data on killer whales and the other for collecting data on vessels in the vicinity of the killer whales.
I record whale data using an individual-follow protocol, and a continuous sampling method during focal follows (Altmann 1974, Mann 1999). A focal whale is chosen and subsequent group spatial assessments are taken at least every 5 minutes based on the distance of other animals to this one. Group spatial measurements include standardized inter-individual distances (contact, tight, loose, spread) and orientation (flank, linear, non-linear). If the focal animal leaves the group, the research vessel remains with that animal for the duration of the focal follow. Additional sampling methods are used including scan sampling to record the gross behavioral activity state (resting, foraging, socializing, traveling) that most group members (always including the focal animal) are engaged in (Mann et al. 2000). Scan sampling is also used to record focal group size, pod identity, identity of non-focal group whales/sub-pods in area, approximate total number of whales in area, direction, and speed. Point sampling is used to record the distance and identity of the focal animal’s nearest neighbor whenever possible (Mann et al. 2000). To record vessel activity, location, and distance relative to the focal whale, a research assistant utilizes a second integrated remote sensing equipment package to collect vessel data using scan sampling during the same sampling track on 5-minute intervals. Vessel data collected include: geo-referenced latitude/longitude location, vessel class (commercial and private whale-watching, commercial fisheries and private sports fishing, monitoring, enforcement, research, ferry, military, shipping, non-motorized), vessel placement relative to focal whale group (inshore, in path, offshore), vessel position relative to whale group (parallel, bow-in perpendicular, bow-out perpendicular), location relative to whales (in front, to the side, on top of, behind) and vessel speed (stationary, slow, medium or fast). Data post-processing combines vessel and whale tracks for analysis.
During the 2007 and 2008
field seasons (June – October) an average of 6.5 hours per day were
spent during 98 days of field data collection, during which 220 focal
follows were conducted, resulting in 14,900 geo-referenced location
points including behavioral attributes of boats and whales to be used
for analysis. Analysis of all data is currently
underway. Log-linear regression analysis will be used to
determine if SRKW group cohesion changes in response to vessel operator
activities, distance and/or density, or geographic location.
Previous studies suggest that log-linear regression analysis may be
successfully used to show effects of vessels on marine
mammals. For example, Williams, et. al. (2006) used
log-linear analysis to show that boat presence had a strong effect on
the probability of change in activity state for Northern Resident
Killer Whales, and Lusseau (2003) used log linear analysis to show that
boat interactions affected the probability of transitions in activity
state for bottlenose dolphins.
Deborah Giles (lead)
Deborah Elliott-Fisk, Ph.D.
Pete Klimley, Ph.D.
2008, 07 National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Research Contract awarded to study biogeography of Southern Resident killer whale behavior.
2008, 07, 06 Recipient of a Henry A. Jastro and Peter J. Shields Research Fellowship Award
2008-2005 UC Davis Geography Graduate Group Research Grant: Student Support Award, recognizing student promise of productive scholarship, annual award for the past 4 academic years.
2007 Office of Graduate Studies, Travel Award, to present research at AAG annual conference