Project: Biogeographic study of Southern Resident Killer Whale (SRKW) behavior in the Salish Sea

 


Introduction:

Southern Resident Killer Whales
Group of Southern Resident Killer Whales.
Photo by D. Giles

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.  

Objective:

Our objectives are to address the following hypotheses:

1)    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.

2)    The spatial structure of SRKW groups does not change relative to vessel conditions.  This hypothesis tests the influence of vessel conditions (geographic location, types, densities, behaviors) around SRKWs for their affect on SRKW group spatial structure.

Methods:

Breaching killer whale
Breaching killer whale.
Photo by D. Giles

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. 

Progress:

Killer whale dorsal fin
Dorsal fin of killer whale.
Photo by D. Giles

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.

Ongoing analysis of vessel and whale data are being explored in ArcGIS 9.2; a program that can examine a variety of spatial and temporal questions that would be more difficult to achieve using more traditional statistics.  GIS will be used to analyze changes in whale behavior in different geographical regions and as variables within their environment change such as season, day of the week, currents, number of boats, and bathymetry.  Geographical location of whales are being examined to determine which areas the whales are occupying during different activity states throughout the season for comparison with other published habitat use data (Hauser, 2006).  Further spatial analysis will be used to see if vessels tend to approach and observe whales differently in different regions; such information may inform future regulations regarding whale watching in particular zones, such as those that are deemed important feeding areas.

Personnel:

Deborah Giles (lead)

Deborah Elliott-Fisk, Ph.D.
Department of Wildlife, Fish, & Conservation Biology, University of California, Davis

Pete Klimley, Ph.D.
Department of Wildlife, Fish, & Conservation Biology, University of California, Davis 

James Quinn, Ph.D.  
Department of Environmental Science and Policy, University of California, Davis

Lynette Hart, Ph.D.  
Department of Population Health & Reproduction, University of California, Davis

Funding Sources:

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

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