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PACIFIC MAMMAL RESEARCH
Science Summaries
Want to learn more about PacMam's work but skip the scientific jargon? No problem!
Enjoy this growing collection of summaries, poems, and more that share our work in a new way.
Resident Harbor Porpoises (Phocoena phocoena vomerina) in the Salish Sea: Photo-Identification Shows Long-Term Site Fidelity, Natal Philopatry, and Provides Insights into Longevity and Behavior
Harbor porpoises, often confused with dolphins, can be found worldwide, including in the Salish Sea. Harbor porpoises are characterized by their small robust body, blunt snout and small dorsal fin. However, there is a lot unknown about these marine mammals. How many harbor porpoise live in the Salish Sea and how do they use the area? They are thought to not be very social, but is that true? How do they interact with one another? How often do they have babies? Do those babies stay in the area? Answers to questions like these are important to understand the conservation status of these animals and to inform management of their habitat.
PacMam's recent study used 11 years of photo identification monitoring to help shed some light on these questions and others. This technique involves watching for porpoises from shore and taking pictures of their distinguishing features such as dorsal fins, body markings and coloration. Photo identification is a valuable tool for studying marine mammals because it is non-invasive, low cost, and can provide a wealth of vital information.
Data from this research confirms that there is a resident population of harbor porpoises that can be seen year round in the Salish Sea. The group size varies from season to season, with reduced group numbers occurring in the summer–typically harbor porpoises are found in groups of two to three individuals. Photo ID also revealed that females as old as 14 can birth baby porpoises, also known as calves, and can reproduce in consecutive years. In this study, at least 3 calves remained in the area beyond weaning from their mothers.
Harbor porpoise behavior is typically thought of as cryptic but photo ID uncovered some trends. Behaviors such as travel, foraging, and other social behaviors were influenced by season and tide. This research emphasizes the need for more fine-scale studies like this to ensure appropriate management and conservation of harbor porpoise populations and stocks are implemented worldwide.
Scientific Poem: In-Water Photo-Identification, Site Fidelity, and Seasonal Presence of Harbor Seals in Burrows Pass.
- A Poem By Tegan Keyes.
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Burrows Pass sings.
Boiling eddies and rips
funnel through the narrow throat
lined with island tissue.
Each tidal breath
hums with marine life
flurries of gulls, otters and lingcod
sea urchins, coils of kelp
and harbor seals.
A jumbled mess of sound
from which we hoped to pull
a single line of music,
the secrets of the seals’ lives
once muted by water.
Season after season
Burrows Pass
sang to us in seals.
They rolled along the blue-tongued currents
like messages in mottled bottles
and we photographed them
as they bobbed at the surface.
We cataloged the markings of their fur
and saw that some seals visited only once
but others swam the pass again and again,
each moved to a different rhythm
resisting unison.
Unpredictable, and yet we observed each year
that our sightings steadily rose and fell,
echoing seasonal cycles
of pupping and molting
plankton blooms and summer upwelling
forage fish migrating and spawning.
Slowly, patterns emerged
from the spots and scars
scattered across each photograph,
and gray noise resolved into collective harmony.
We listened
and from the mouth of Burrows Pass
spilled the song of the harbor seals.
- Scientific Summary By Andrea Segers.
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What might happen if a harbor porpoise goes after prey that’s too big? Harbor porpoises
have been recently documented targeting and catching large fish species, such as salmonids and American shad. This new behavior can be a huge risk for the harbor porpoise if they try to consume the fish whole - similar to how they consume smaller fish.
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Porpoises need to consume a very large amount of food in order to survive, and female porpoises need to eat even more when supporting a baby. Female porpoises, especially pregnant or lactating females, are the most likely to go after these large fishes. It takes a lot less energy to catch one big fish instead of having to catch a bunch for the same amount of food.
Catching large fish species could result in the harbor porpoise choking and then drowning. This feeding behavior is very risky for the porpoise, but it can also be a very big reward for them if they manage to eat it. This high-risk, high-reward feeding behavior could be what drives harbor porpoises to catch these large fishes, especially for the ravenous reproductive females who need to support a fetus.
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For us, eating too much at once can result in a tummy-ache, but for harbor porpoises it can be fatal.
Scientific Poem: Open water grouping behaviour in harbour seals (Phoca vitulina richardii) of the Salish Sea
- A Poem By Tegan Keyes.
​
We watched them cluster
on mudflats and rocky outcrops
they hauled their bodies to shore
heavy as beached ships
landed, languid
drowsily tolerating our scrutiny
But when they returned to the sea
our observations foundered
we thought them solitary seafarers
gray and whiskered
embarking on private expeditions
to fill their round hulls with fish
before returning to the safe harbor
Until we looked out to open water
far from their shoreline sanctuaries
And saw strange aggregations
dozens of seals swimming together
lifting sun-glossed heads out of the water
before curling into a dive, inverting
their pale keels turned to the sky
to scan for prey below
A fleet of mottled ships
rolling through blue water
they sailed together in mysterious synchronicity
flouting our predictions
heeding a call unknown to us.