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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.
Abstract
Harbor porpoises have been well studied in locations worldwide, but relatively little research has focused on site fidelity of individuals, which influences population structure and determines appropriate management and conservation measures. This study investigated the site fidelity and behavior of harbor porpoises through long-term, land-based photo-identification around Fidalgo Island, Washington, USA. Individuals were consistently re-sighted for up to 11 years, including natal philopatry. There was individual variation in seasonal site fidelity, with some individuals seen year-round, though general porpoise presence in the study area and individual re-sightings were greatly reduced during summer. Females had calves yearly for up to 3 consecutive years, with females as old as at least 14 successfully producing calves. There was some evidence for mother–calf associations post-weaning, but none long-term. Behavior was affected by tide, where porpoises traveled more and foraged and socialized less during ebb tide compared to other tidal states. Mating attempts with aerial behaviors were observed 84 times and seen year-round in every month and every season. This study provides documentation of a local, resident population of harbor porpoise, and emphasizes the need for more fine-scale studies like this to ensure the appropriate management and conservation of harbor porpoise populations and/or stocks worldwide.
Scientific Poem: In-Water Photo-Identification, Site Fidelity, and Seasonal Presence of Harbor Seals in Burrows Pass.
- A Poem By Tegan Keyes.
​
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.
Abstract
Little is known about the in-water behavior and site fidelity of harbor seals (Phoca vitulina richardii), as most photo-identification (photo-ID) studies are typically conducted while they are hauled-out on land. We investigated in-water site fidelity rates and seasonal presence in Burrows Pass, Washington, using photographs collected during a long-term photo-ID and behavioral study from January 2015 through November 2019. There was a minimum of 161 individuals and a maximum of 286 individual harbor seals using Burrows Pass. Harbor seals were present in all seasons, with the lowest sighting rates during summer. Individuals were more likely to be sighted/re-sighted in fall and spring. There was large variations in the level and seasonality of site fidelity among individuals. The majority of seals (69.62%) were seen only once, but 22.69% showed low to moderate site fidelity (2–5 sightings) and 7.69% showed strong site fidelity (≥6 sightings) over seasons and across years. These seasonal variations were likely due to foraging, life history, and individual behavioral variabilities. Studies like this provide necessary information about harbor seal in-water site fidelity and behavior, which are less well known but vitally important in harbor seal management and conservation.
- Scientific Summary By Andrea Segers.
​
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.
​
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.
​
For us, eating too much at once can result in a tummy-ache, but for harbor porpoises it can be fatal.​
Abstract
This short note provides unique insights into previously undocumented harbor porpoise behavior and diet. We document the addition of two new species as harbor porpoise prey items along the U.S. West Coast (pink salmon and American Shad) and one in the Salish Sea (coho salmon, salmonid sp.). These prey species are typically larger in length and mass than the majority of prey species known to be consumed by harbor porpoises. Observations were made during field studies in San Francisco Bay, CA, Cook Inlet, AK and Anacortes, WA (Salish Sea). There were distinct behaviors observed when hunting: accelerating just under the surface often making tight circles as they chased the fish and then when captured the porpoise carried the fish sideways in the mouth before diving. This differs from their foraging behaviors when chasing small prey items. This research shows that harbor porpoises sometimes take larger than average prey items, thus it is imperative to update our knowledge of their prey choices and quality of their prey to better understand their energy needs. Little research on this species has focused beyond group size, population abundance/distribution presence/absence in relation to use of specific habitats. and mating behavior; thus, wild harbor porpoise behavior remains poorly understood. Reports such as this are important to improve our knowledge of this difficult to observe species and highlight the need for further research and monitoring to fully understand their behavior repertoire and ecological relationships.
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.
Abstract
Harbour seals (Phoca vitulina) commonly form larger congregations at haul out locations during times of rest and pupping season, but are generally thought to be solitary at sea. Occasionally larger clusters of individuals may be observed swimming near haul out sites, forced bottlenecking channels or mouths of rivers with concentrated prey and restricted space. Recently, isolated occurrences of mass gatherings of harbour seals have been observed in the Salish Sea that were distanced from haul out sites (over 1 km away) or forced bottlenecking regions. In April-June (but primarily May) 2019–2021 juvenile and adult harbour seals in Burrows Pass (Anacortes, WA, USA) were observed in large groups (N=31) ranging in size from 6–50 individuals (x‾=16.8) within 1-2 body lengths of each other and periodically diving down seemingly hunting and chasing prey. These groupings primarily occurred during flood and slack high tides. Based on the surface level activity observed, habitat type, the frequency of individuals using the area for foraging year round and the tidal preferences during the occurrences, it is likely these are foraging events. Similar large groups have been documented (N=10) in the South Puget Sound and Central Puget Sound, first observed in 2016 and officially documented in February of 2017. These groupings (from 20–30 to 150+) occurred year round and at varied tidal states. While some sightings were obviously foraging behaviour, others appeared to be resting, traveling or socializing. Open water behaviour of harbour seals is not well documented, and a literature review found no other published accounts of large in-water groupings. Investigation of ecological relationships (like prey spawning, prey abundance, or other environmental correlates) and observation of underwater harbour seal behaviour will aid in determining the reason for this seemingly novel behaviour.
Scientific Poem: Harbor Porpoise Aggregations in the Salish Sea
- A Poem By Tegan Keyes.
​
Rolling through the waves like glossy wheels
breaking the surface, curling into a dive.
A score of sleek bodies,
flushed and dizzy with life.
We thought that harbor porpoises prowled the seas
in relative solitude.
That their gatherings were small, occasional.
Not these lunging masses
performing their ceremonies of mating and foraging
with puffing, squealing exuberance.
An anomaly, an inconsistency.
And yet, when we sought further data
Witnesses arose, undismissable.
Marine mammalogists, community scientists, whale watch captains
shared tales of harbor porpoises flocking in their hundreds,
stories that had sunken into obscurity.
It was a lesson in the limits of our recorded memory.
In what goes unseen when we do not expect to see it.
In what is lost when we do not care to look for it.
We had directed our research elsewhere
as generations of harbor porpoises gathered in great numbers
with only the ocean to bear witness.
A hidden history
that we must now piece together from scraps of stories,
combining our many eyes into one clear gaze
to observe the unexpected, unfamiliar, unknown
And to be graced with a depth of understanding
once unfathomable.
Abstract
Harbor porpoises are typically seen in small groups of 1–3 individuals, with aggregations of 20+ individuals treated as rare events. Since the 1990s, the harbor porpoise population in the Salish Sea has seen a significant recovery, and an increased number of observed aggregations that exceed the more usual small group sizes has been observed in recent years. By combining the observational data of United States and Canadian research organizations, community scientists, and whale watch captains or naturalists, we demonstrate that harbor porpoise aggregations appear to be more common than previously known, with 160 aggregations documented in 2022 alone. Behavioral data also indicate that foraging behaviors are common and social behaviors, like mating, are seen more often during these encounters compared to small groups. Other behaviors that are considered to be rare or unknown were also observed during these encounters, including cooperative foraging and vessel approach. These aggregations are likely important foraging and social gatherings for harbor porpoises. This holistic approach integrating data from two countries and multiple sources provides a population level assessment that more effectively reflects the behavior of harbor porpoises in this region, which do not recognize the socio-political boundaries imposed upon the natural world.
Scientific Poem: Kleptoparasitic interactions by bald eagles (Haliaeetus leucocephalus) during marine mammal foraging events
- A Poem By Tegan Keyes.
​
the scene:
the ocean surface
a confluence of sea and sky
a thin place, liminal
the cast:
porpoise, seal, orca
eagles, terns, gulls
a shifting ensemble of foragers
compelled by convergent hungers
enter stage:
a salmon
burning with desperate speed
a harbor porpoise
spiraling upwards in hungry pursuit
an eagle
circling above, sharp-eyed
climax:
the porpoise accelerates
its fin shreds the waves white
the eagle swoops down
talons cleave the water and snatch the fish
wings beat hard against thrashing weight
the thief ascends, victorious
end scene:
the gray fin cuts the surface once more
the porpoise sinks away
weakened by fruitless exertions of fluke and flipper
an endless drama:
citizens of two nations
the aquatic and the aerial
colliding on the blue-green stage
negotiating the terms
of their coexistence.
Abstract
Stealing of food items from another animal, or kleptoparasitism, has been well studied in bird species. Bald eagles are known kleptoparasites of other birds and occasionally other species, however kleptoparasitic interactions with mammals are relatively uncommon. We describe instances of bald eagles taking, or attempting to take, fish and mammal prey from three species of cetaceans (bottlenose dolphins (Tursiops truncatus), harbour porpoises (Phocoena phocoena vomerina) and killer whales (Orcinus orca)) and one species of pinniped (harbour seal (Phoca vitulina richardii)) on the east and west coast of the United States of America. We discuss possible drivers of this emerging behaviour, including bald eagle population increases, reductions in other prey abundance, and changes in prey choice (for harbour porpoises). Further research is needed to determine if this behaviour is opportunistic in nature, or a more common foraging strategy.
Scientific Poem: Harbor porpoises (Phocoena phocoena vomerina) catching and handling large fish on the U.S. west coast
- A Poem By Tegan Keyes.
​
The harbor porpoise
beams a hunting hum
into the dark water.
click click click
​
Flickers of motion echo back
bright as stars in the distant murk.
​
click click click
A Pacific hake
long and slim against the sand
glinting like a lost needle.
click click click
A pale squid
mantled and soft
tentacles flickering.
click click click
A distant school of small fish
herring or anchovies
glittering with dazzling motion.
Mere slivers of sustenance
small sparks burning in cold water.
click click click
But there ahead, a salmon
immensely resonant, an iron bell
flushed, fragrant, glowing with red sun
uncommon prey but perhaps worthwhile.
​
clickclickclick
​
The porpoise accelerates
and the chase begins.
​
clickclickclick
The salmon flees with frantic speed
spirals upwards, shatters the surface
in a hiss and fizz of foam.
swoosh splash snap
​
The porpoise lunges, clamps its jaw
teeth spade silver skin and firm muscle
the first plume of blood
crackles on the eager tongue
tasting of sun and salt and oil.
gasp crunch gulp
​
Scales scatter
the fish flails, caught by the gills
awkward and unwieldy
it must be wrangled into position
and swallowed whole
a choking risk, a rich reward.
splash puff puff
The porpoise surfaces once more
it blasts a gust of air and spume
an exhilarated exhalation
and swims onward
hunger satisfied.
Abstract
This short note provides unique insights into previously undocumented harbor porpoise behavior and diet. We document the addition of two new species as harbor porpoise prey items along the U.S. West Coast (pink salmon and American shad) and one in the Salish Sea (coho salmon, salmonid so). Little research on this species has focused beyond group size, population abundance/distribution, presence/absence in relation to use of specific habitats (Elliser et al., 2018), and mating behavior (Keener et al., 2018); thus, wild harbor porpoise behavior remains poorly understood. Reports such as this are important to improve our knowledge of this difficult to observe species and highlight the need for further research and monitoring to fully understand their behavioral repertoire and ecological relationships.