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Gordon Sarratt
MARC ISR class of 2026
What it is:
Most of the world's gray whales (eschrichtius robustus) live off the western coast of north america, and the predominant population (Eastern North Pacific or ENP) makes the trip every year from foraging in Alaska in the summer down to Baja California Sur in the winter to raise their calves. Gray Whales are among the most opportunistic foragers of the baleen whales, and are somewhat frequently found feeding on a wide variety of prey all up and down the coast. Their primary foraging strategy is benthic feeding, where the whales dive down to the seabed and use their short baleen to filter amphipods from the mud. This is where the majority of gray whale's diet comes from, during the summer in the arctic.
Intertidal pit feeding is a unique behavior exhibited by a small population of gray whales who take a detour off their migration route to forage for ghost shrimp in the North Puget Sound (NPS) in Washington. They wait for the tide to be high and then go into the shallow water of the intertidal zone to filter feed for ghost shrimp. This is a very high-risk strategy for the whales, and can result in their being beached. (the "cool pictures and facts" section on this blog has videos of the whales engaging in this behavior if you're interested in seeing more)
Why it's important:
One of the biggest modern threats to all whales, but in particular Gray Whales, is declining food availability. The past 2 Unusual Mortality Events (UMEs) both were likely caused by starvation and decreased energy availability. Therefore, a full understanding of the foraging energetics of these animals is critical to their conservation as well as that of their prey. Gray Whales are also highly resilient among whale populations, having had a significantly stronger return to normal population levels post industrial whaling. One hypothesis as to why this is is because they are such effective opportunistic foragers. A better understanding of this type of foraging behavior could lead to more informed conservation efforts and research with species that are struggling to rebound from Industrial whaling. The prey species, Ghost shrimp, are harvested by local commercial fisheries to be sold as bait for recreational sturgeon fishing. One of the primary concerns of regulators is the sustainability of the commercial and whale combined use of the shrimp population, and a better understanding of the whale resource use will make those judgements more informed.
The ENP whales' migration route. The Sounders make their stop roughly halfway through their spring migration.
The typical benthic feeding process.
Gray Whale body condition is a major marker of health and an increase or decrease often indicates changing forage quality. This image comes from an IUCN page considering the recent threats to the Gray Whale population.
the study area in Washington, along with a picture of an individual site
What I'm doing:
I'm using UAV (drone) photogrammetry to determine the characteristics of intertidal pit feeding in whales. My mentor Hannah has been taking thousands of aerial pictures at low tide over the past few whale seasons, and each picture has RTK (real-time kinematic) metadata that allows them all to be assembled into a 3D model of the intertidal sediment during each individual flight on a given day. Using that 3d model, I can measure and count the pits that the whales leave behind, gathering data spatial and temporal characteristics of the behavior, both on an individual level and on a sound-wide scale. The primary goal is to determine the average dimensions of an individual feeding pit, and how they vary depending on the forager's age, head size, or timing. This will also allow us to determine the density of this behavior in the 4 test areas, and its variation depending on whale sightings, how long feeding pits stick around in the intertidal zone, how pit dimensions change over time and relative to location, and assess the level of recent predation's impact on prey abundance.
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