Linking predator-prey interactions is a favorite topic among ecologists, but can be expensive and challenging to accomplish at fine scales, particularly in shallow waters that limit traditional prey mapping methods. The Pacific Coast Feeding Group (PCFG) of gray whales forages in the Oregon near-shore environment, making them accessible for study with creative, low budget technology. This project aims to link gray whale foraging behavior with fine-scale prey distributions, using inexpensive field methods (e.g., theodolite, GoPro cameras and shallow net tows deployed off a research kayak) that have broad applications.
For five consecutive summers we have non-invasively tracked gray whale movements with shore-based theodolites in Port Orford, Oregon, USA. When conditions allow, a research kayak is concurrently navigated to sampling stations in two comparative study areas within the tracking viewshed (Mill Rocks and Tichenor Cove). GoPro cameras are used to record zooplankton relative density in the water column and zooplankton net tows are used to assess community structure. Prey quality is further assessed through bomb calorimetry, a method used to determine the caloric content of organic matter. This analysis (conducted in collaboration with COZI) will allow us to determine whether zooplankton species vary in their caloric content along the Oregon coast, and therefore may have different energetic benefits for gray whales. Whale behaviors are categorized into search, forage, and transit behaviors using the Residence in Space and Time method.
Despite being only one kilometer apart, we have found significant spatio-temporal differences in the community assemblages of zooplankton between the two study areas, and whales demonstrate fine-scale habitat selection relative to this prey availability. Preliminary results indicate that prey quality, assessed through caloric content of zooplankton, does vary by species and reproductive stage, however not by time or space. Additionally, we have documented annual variation in prey availability and whale distribution and behavior patterns in the area. As we continue this long-term study, we aim to assess whether these PCFG individuals display foraging specializations. If individuals display different ecological patterns (i.e. spatial use, prey preferences) then they may be exposed to different threats, which can consequently impact populations in variable times, ways, and intensities.
Linking predator-prey interactions is a favorite topic among ecologists, but can be expensive and challenging to accomplish at fine scales, particularly in shallow waters that limit traditional prey mapping methods. The Pacific Coast Feeding Group of gray whales forages in the Oregon near-shore environment, making them accessible for study with creative, low budget technology.
Oregon State University Marine Mammal Institute
Hatfield Marine Science Center
2030 SE Marine Science Dr
Newport, Oregon 97365
Phone: (541) 867-0202
Fax: (541) 867-0128