May 19, 2025 • 29 mins
Dive into the fascinating world of the Harbor Seal (Phoca vitulina)! This episode explores the research covering their widespread distribution across coastal habitats, their incredible physical adaptations for survival in marine environments, and their crucial role as both predator and prey within diverse ecosystems. We'll uncover insights into their behavior, reproductive cycle, and the ongoing conservation efforts to protect this adaptable species.
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Episode Transcript
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(00:00):
You're listening to MOO nature documentaries.
Welcome to the deep dive. Today we're taking a look, a
close look at a really fascinating animal you find
across the Northern hemisphere, the harbor seal.
That's right, Volkovich Celina, a truly widespread marine
mammal. And you mentioned something
amazing before we started. Some of them can dive what, over
(00:21):
100 meters down? Easily.
Yeah, they're remarkable swimmers and divers.
We pulled together quite a bit of research, various sources to
really get under the skin of these seals.
So our mission today for you, the listener, is to get a solid
understanding of these animals, their biology, how they live,
their place in the environment without getting bogged down and,
you know, overly technical. Stuff exactly.
(00:42):
We want to explore what makes them tick, how they're adapted
to so many different coastlines from icy Arctic edges to more
temperate zones, and the challenges they're up.
Against OK, sounds great. Let's start with where you'd
actually find them. Their distribution seems.
Huge. It really is impressive.
They span both the Atlantic and the Pacific.
So like where specifically in the Atlantic?
(01:03):
We'll think North America from the Arctic down the coast to
about the Mid-Atlantic U.S. states.
And then over in Europe, you're looking at Iceland, Norway, the
British Isle, all the way down to northern France.
And the Pacific? Similar story Bering Sea,
Alaska, right down the North American coast of Baja
California and then across the ocean, eastern Asia.
(01:26):
So Russia, Japan, that area. That covers a massive amount of
coastline and they're not too picky about the type of coast,
are they Rocky shores? Sandy beaches.
That's one of their key strengths, adaptability.
They thrive in diverse coastal environments.
Rocky shores, yes. Sandy beaches, absolutely.
Estuaries are particularly important to.
Estuaries. Why they're specifically?
Because they're often really rich foraging grounds, lots of
(01:49):
fish where the fresh water mixeswith the sea.
But wherever they are, they absolutely depend on haul out
sites. Haul out sites, that's their
base on land right for resting. Exactly.
Resting, warming up, molting andcrucially for raising their
pups, they need these spots on land or sometimes ice.
What makes a good haul out spot?I imagine they can't just pick
anywhere. Up Several things matter.
(02:11):
Tidal patterns are a big one. They often haul out at low tide.
They also look for places with minimal human disturbance and
fewer predators around. Makes sense.
So what kind of places fit the bill?
You can be sandy beaches, rocky areas, mud flats, even man made
structures sometimes like docks or Piers if they feel secure
(02:32):
there. Interesting they'd use human
structures. You mentioned ice too.
Yeah, and the more northern parts of their range, they
definitely use ice flows, especially for pupping.
But it's worth noting they're generally less reliant on ice
than, say, Arctic seal specialists.
OK, so they need land or ice, but they're clearly masters of
the water too. That 100m dive depth is proof of
that. Oh absolutely.
(02:53):
There are depth swimmers very capable in open water.
Can you give us a couple of examples of how their habitat
choice differs regionally, like Pacific Northwest versus North
Atlantic? Sure.
So in the Pacific Northwest you'll often find them favoring
sheltered bays and inlets. Contrast that with the North
Atlantic, where rocky coastlines, offshore islands are
more typical habitats. In Europe, like the Wadden Sea.
(03:15):
Right. The Wadden Sea is a classic
example. Huge populations there rely
heavily on those extensive intertidal sand and mud flats
for both resting and feeding. It really highlights their
flexibility, but with coasts being so popular for humans too,
how does our activity affect them?
That's a major issue. Coastal development can destroy
(03:35):
haul out sites. Pollution degrades their habitat
and food sources. Boat traffic can disturb them,
especially during sensitive times like breeding season.
So conservation efforts need to focus on protecting those
habitats. Definitely protecting their key
haulout and foraging areas is a critical part of conservation.
Now what about movement? Do they migrate long distances
(03:57):
or mostly stick to 1 area? They're generally considered
pretty sedentary. They tend to have defined home
range. So no epic migrations.
Not really, no. They do make localized movements
though. Yeah, these are mostly driven by
seasonal shifts and where their food is, or finding the best
spots for breeding or molting. Think of it like moving between
different neighborhoods rather than across countries.
(04:18):
OK, so if the fish move they might follow them locally?
Exactly, or they'll move to specific sheltered sites for
pupping season, then shift back to fallow prey patterns
afterwards. But it's usually all within that
broader home range. That makes sense.
Looking back historically, has their range always been this
widespread or has it changed? Historically, yeah, they had a
(04:39):
very broad distribution, but during the 19th and early 20th
centuries, hunting pressure was intense in many.
Areas, right? Sealing was a major industry.
It was, and it led to significant population declines
and even local extinctions in some places.
But things have improved. Thankfully, yes.
Conservation laws like the Marine Mammal Protection Act in
(05:00):
the US, passed in 1972, have been really important.
They've allowed many populationsto stabilize and even increase.
That's good news. So the current picture is stable
overall. Currently, they're still found
across those North Atlantic and Pacific coasts, but it's a bit
patchy. Some populations are doing quite
well, thriving even. Others are still considered
(05:21):
vulnerable because of ongoing pressures like habitat loss or
accidental capture and fishing gear.
So a mixed bag really. Success in some areas, ongoing
concerns and others. Precisely, it requires continued
monitoring and management, region by region.
OK, let's shift gears a bit. We know where they live, but how
do they live there? What physical traits allow them
(05:42):
to thrive in that marine environment?
Well, I've got a whole suite of fantastic adaptations.
First off, their body shape is very streamlined kind of
torpedo. Like just winging efficiency,
right? Less drag.
Exactly. Makes moving through water much
easier. Yeah.
And then, of course, there's theblubber, a thick layer under the
skin. The classic seal feature for
warmth. Primarily for insulation, yeah,
(06:04):
Essential in those cold waters, but it's also a really important
energy reserve. OK.
And they're flippers. How do they?
They've got 4 limbs and hind limbs modified into flippers.
The front ones are smaller, mostly used for steering, you
know, maneuvering. The powerful thrust comes from
the larger hind flippers. Giving them that agile movement
underwater? What about their appearance?
(06:25):
Their fur. Their fur provides some
insulation to, but its main rolemight be camouflage.
It's typically Gray or brown, but with a unique pattern of
spots or rings for each seal. So they blend in with rocks or
the sea bed. Pretty much helps them avoid
predators and maybe sneak up on prey.
And how do they sense their world, especially underwater,
(06:47):
where it can be dark or murky? That's where they're whiskers
come in the Vibra Sea. They're incredibly sensitive.
To touch. To vibrations, really.
They can detect the tiny water movements made by fish swimming
nearby, even when they can't seethem clearly.
Wow, like underwater radar? What about eyesight?
It's adapted for underwater vision too.
They have large lenses and lots of rod cells in their retinas
(07:09):
which helps them see better in low light conditions.
And they can close their nostrils and ears.
Yep, essential for diving. Keeps the water.
Out all sounds perfectly designed.
Does their look change much through their lives or with the
seasons? Oh yes, pups are born with a
special coat called lanugo. It's soft, woolly, often whitish
or light Gray. But they don't keep that.
(07:29):
No, they usually shed it either just before or very shortly
After Earth. Then, as juveniles, they develop
that denser, waterproof adult fur, and their individual spot
patterns become clearer as they age.
And adults, do they change appearance seasonally?
The main change is the annual molt.
After the breeding season, they shed their old worn out fur and
(07:50):
grow a new coat. Must take a lot of energy.
It does. They often spend more time
hauled out during the molt, partly to conserve energy and
help the shedding process along.The new coat usually looks
brighter, more vibrant. We talked about blubber for
warmth. How else do they manage body
temperature, especially going between cold water and
potentially warm land? Blubber is key, but their fur
(08:12):
and skin also play roles in insulation and, importantly,
releasing excess heat when they're on land.
They also have a neat trick in their flippers.
Oh yeah? What's that?
It's called countercurrent heat exchange.
Basically, the warm blood flowing out to the flippers runs
right next to the cold blood coming.
Back so the outgoing blood warmsup the returning blood.
Exactly. Helps keep their core body
(08:34):
temperature stable and minimizesheat loss through the
extremities. Really efficient.
That's clever biology. Any other tricks?
Behavior is important too. Basking in the sun on a rock
warms them up. Spending more time in the water
can cool them down. They can even adjust their
metabolic rate to some extent, generating more heat if needed
or slowing things down to conserve energy.
(08:55):
The whole toolkit for thermoregulation now are males
and females. Easy to tell apart just by
looking. Not really.
The differences are quite subtle, especially compared to
some other seal species. How so?
Well, males tend to be slightly larger on average, maybe 1.6 to
1.9 meters long, weighing 70 to 150 kilograms.
Females are more like 1.5 to 1.7meters in 60 to 110 kilos.
(09:19):
So a slight size difference, butnot huge.
Right. And their coloration, the spot
patterns are very similar. Males might look a bit bulkier,
perhaps around the neck and shoulders, especially mature
males, but often you can't reliably tell them apart just by
sight alone, unless maybe you see specific reading behaviors.
OK. And you mentioned there wide
range earlier, does that mean there are different types like
(09:40):
subspecies in different? Areas.
Yes. There are generally 5 recognized
subspecies, each adapted to its specific region.
Can you give us a quick rundown?Sure, there's the Eastern
Atlantic subspecies PV virgilinafound around the UK, Baltic,
Norway, Iceland, then the Pacific one PV retarded along
the North American Pacific Coast.
(10:01):
The Western Atlantic PV con colour from eastern Canada down
towards New York. The carill seal give you
stationary near Japan and the Kuril Islands.
And one more. Yes, the really unique 1 the
Ungava seal PD Malone. It's a fresh water subspecies
living in lakes in Quebec, Canada.
It doesn't migrate to the sea at.
All freshwater seal. That's incredible.
(10:22):
Really shows their adaptability.It absolutely does.
Each subspecies reflects adaptations to local conditions,
water temperature, prey types, things like that.
OK, welcome back. Let's dive into the harbor seals
life cycle now. When does the breeding season
kick off for them? It happens once a year, but the
timing really varies depending on where they are.
It's all about lining up the birth of pups with the best
(10:43):
environmental conditions for survival.
So warmer places versus colder places.
Generally, yeah. In temperate spots like the
Northeast Pacific, think late spring, early summer, maybe May
to July. In the colder Northeast
Atlantic, it shifts a bit later,maybe June to August.
And way up. North in the Arctic and
subarctic, it tends to be even later, July through September.
(11:04):
Take advantage of those short, warmer months.
Makes sense. So walk us through the life
stages, birth onwards. OK, pups are born usually on
land or ice, and they're quite developed at birth, what we call
precocial. They shed that fuzzy lanugo coat
quickly. Then comes weaning.
It's surprisingly short, only about four to six weeks, but the
(11:26):
mothers milk is incredibly rich,very high in fat.
To help them bulk. Up quickly?
Exactly. Rapid growth, building up that
essential blubber layer before they have to fend for
themselves. Weaning is a critical transition
to independence. So after just a month or so,
they're on their own. Pretty much they enter the
juvenile stage where the big task is learning to hunt
successfully. It's a tough time, lots of
(11:48):
growth still happening, but they're also very vulnerable.
To predators just figuring things.
Out both, yes. Then if they make it through
that they reach sexual maturity.Females usually around three to
five years old. Males may be a year or two
later, Four to six years typically.
And then they start breeding themselves.
Right adulthood involves those annual breeding cycles.
(12:09):
Mating usually happens in the water quite soon after the
female weans her pup, and they have this fascinating adaptation
called delayed implantation. Delayed implantation What's?
That it means the fertilized eggdoesn't immediately implant in
the uterus and start developing.It waits for a few months.
Why would it do? That it effectively times the
pregnancy so that the birth happens about a year after the
(12:30):
previous one, right back in thatoptimal pupping season.
It synchronizes the whole cycle.'S amazing timing and how long
can they live? In the wild, a good lifespan is
up to 25, maybe 30 years. OK, so back to mating.
How do they actually find and choose a partner in the big
ocean? It seems males do a lot of the
work attracting females. They produce underwater
(12:52):
vocalizations, grunts, growls, sometimes louder roar like.
Sounds advertise themselves. Essentially yes, to attract
females and maybe establish somesort of temporary territory
underwater. It's thought that females might
assess the quality of a male based on these calls.
Like a vocal display? Kind of Males might also perform
(13:13):
physical displays in the water, your females showing off their
strengths and fitness. Some males might defend specific
underwater areas near where females haul out.
So the females choose based on the calls and maybe the
territory. It seems likely the quality of
his spot, the intensity of his calls, his physical condition
probably all factors into her choice, and timing is linked to
that annual cycle happening soonafter weaning.
(13:35):
Is it always harbor seal with harbor seal or do they ever mix
with other seal types? Hybridization breeding with
closely related species like thegrey seal has happened, but it
seems pretty are mostly documented in captivity
actually. Why not so much in the wild?
Usually, differences in their preferred habitats and breeding
behaviors keep them reproductively isolated.
(13:56):
Although, you know, with environments changing, maybe
interactions could become more common in the future.
It's something researchers keep an eye on.
Interesting. Now parenting, you said weaning
is quick. What's the parental care like
before that? It's all down to the mother's
soul maternal care. She forms a strong bond with her
pup using vocalizations and scent.
And provides that super which milk?
(14:17):
Yes, milk with maybe 4050% fat content, essential for that
rapid growth and blubber. She's also very protective,
guarding the pup from danger or disturbances.
But then at 4-6 weeks, it's justover.
It's a relatively abrupt end. The mother actively encourages
the pup to become independent. Being born precocial really
(14:37):
helps the pup manage that transition.
Gives them a head start. How does a pup physically change
as it grows into an adult? Well, the size difference is
huge. Pups start around, say, 8 to 12
kilograms. Adults can be anywhere from 55
up to 170 kilos. Wow, and they're coat.
That fluffy lanugo gets replacedby the sleeker spotted adult
coat. The spots often become more
(14:59):
defined. Maybe the overall colour darkens
a bit as they. Mature and behaviorally from
dependent pup to independent hunter.
That's the biggest shift. They have to learn to find and
catch all their own food. Juveniles might actually be a
bit more social than adults for a while, maybe learning from
each other before adopting the more solitary adult foraging
style. Again, it's a vulnerable stage.
(15:21):
Right, let's talk about that food.
What exactly is on the menu for a harbor seal?
They're quite opportunistic and have a really varied.
It depends a lot on where they live and what time of year it.
Is generally fish. Fish are definitely a major
component. Things like herring, cod,
mackerel, salmon, various rockfish, flatfish, lots of
different kinds. But they don't stop there.
(15:42):
Invertebrates too. Squid, octopus, shrimp, crabs.
They'll eat those quite readily if they're available.
So the local seafood buffet, essentially.
Pretty much you see regional differences, like in the North
Sea sand eels are super important.
Off California, they might be a more squid and octopus, and the
diet gifts seasonally too, following prey availability.
(16:02):
How do they catch it all using those whiskers?
Whiskers are key for detecting prey, especially in low light.
They're skilled hunters. Mostly they forage alone, but
you might see them gather if there's a big concentration of
fish, like a herring school. And they can dive deep to get
it. You mentioned 100 meters, but
sometimes even deeper. Dives over 500 meters have been
(16:23):
recorded, though maybe not routinely, but they can
certainly access prey quite deepin the water column.
By getting all these different things, what effect do they have
on the ecosystem? Do they control other
populations? They definitely played a role in
regulating populations of their prey.
Eating lots of different fish helps prevent any one species
from dominating and influences the size and age structure of
(16:45):
those fish populations. Same for invertebrates.
So they help maintain balance. Exactly.
By keeping prey populations in check, they contribute to the
overall health and balance of the coastal and estuarine
ecosystems they live in. Their specific impact varies
locally, of course. OK, so they're predators, but
what praise on them? They have some formidable
(17:05):
natural predators. Orcas, killer whales, are
probably the main one. They're very sophisticated
hunting strategies for seals. Anyone.
Else Large sharks, definitely. Great whites, for example, are
known predators. They often use ambush tactics.
Up in the Arctic, polar bears can hunt them, especially when
they're held out on ice. And humans historically.
Historically, yes, humans were amajor predator, Less so now in
(17:29):
most areas due to legal protections, but accidental
entanglement in fishing gear is still a big problem.
What defences do the Seals have against these threats?
Well, vigilance is key. When hauled out, they're often
wary, and being in a group can offer more eyes looking out for
danger. Safety in numbers.
To some extent in the water, their speed and agility are
their best defence. Quick escapes hauling out itself
(17:53):
is a way to avoid aquatic predators like sharks or orcas,
at least temporarily. And camouflage.
That helps too. Ending in makes them harder to
spot. And of course they're diving
ability. Being able to stay underwater
for up to 30 minutes is pretty good way to wait out a thread at
the surface. 30 minutes, that's incredible breath holding.
How does the amount of food available influence where they
(18:16):
go or what they do? Food availability is a huge
driver of their behavior. If food is scarce locally,
they'll travel further on foraging trips.
They're diving patterns. How deep they go, how long they
stay down will change depending on where the prey is
concentrated. And we mentioned seasonal
movements. They'll definitely follow prey
migrations like salmon runs or spawning aggregations of fish
(18:37):
like capelin or sand Lance. So they're constantly adapting
their behavior to the food landscape.
Absolutely. They tend to favor habitats
known for consistent prey availability, like areas near
river mouths or with strong currents that might concentrate
fish. Their life revolves around
finding enough to eat. OK, we've covered their diet and
predators. Let's zoom out a bit now to
(18:59):
their broader role in the ecosystem.
How would you summarize their ecological importance?
They're really integral as predators.
They regulate fish and invertebrate populations,
influencing that whole food web structure, as we discussed.
And as prey. As prey for top predators like
orcas and sharks, there are key link in transferring energy up
the food chain. What else?
Their waste products actually contribute nutrients back into
(19:22):
the water, which helps support the base of the food web, the
plankton and algae. And because their populations
can respond to environmental changes, they serve as important
indicators of ecosystem health. Indicators.
How so? Well, if seal populations
decline sharply in an area, it might signal problems like
pollution, disease or major shifts in prey availability,
(19:43):
reflecting broader issues in themarine environment.
I see. And they sometimes come into
conflict with humans, right? Fisheries.
Yes, that can happen. There's sometimes perceived
competition for commercially important fish species, which
can lead to conflict. Beyond predator prey, what other
interactions do they have with species?
Well, there's competition. Not just conflict with humans,
(20:04):
but also potentially with other marine predators like sea lions
or even some sea birds that might target similar food
sources. Any positive interactions like
symbiosis? Strict symbiosis where both
species clearly benefit isn't really well documented.
Yeah, you might see loose associations like gulls
scavenging scraps from a seals kill.
That's more commensalism. One benefits, the other isn't
(20:26):
really affected. Cleaner fish following them
around or anything like that. Not that we know of, no.
But their general role in keeping the ecosystem balanced
indirectly benefits many other species.
Of course, they also host parasites like internal worms,
which is a different kind of interaction.
OK, let's pivot to conservation.What's their official status?
(20:46):
Are they endangered? Globally, the good news is
they're listed as Least Concern by the IUCN.
Well, that's good. It is overall, but, and this is
important, that's the global picture.
Some specific regional populations are facing
significant threats and might beconsidered threatened or
vulnerable at a local level. So what are those main threats
they face, even if the global status is OK?
(21:09):
There are several key ones. Habitat degradation is a big
one, losing those vital haul outsites to coastal development.
Pollution is another major concern.
What kind of pollution? Things like heavy metals, PCB's,
pesticides, persistent organic pollutants that build up in
their bodies and can affect their health, their immune
systems, even reproduction. Oil spills are devastating,
(21:31):
obviously, and marine debris, plastics while fishing Nets is a
huge hazard. Entanglement.
Entanglement, yes, which can injure or drown them.
And ingestion, too. Then there's climate change.
How does that affect them? It alters their habitat.
Think loss of sea ice in the North Sea, level rise, flooding,
haul out sites. It also shifts the distribution
and abundance of their prey species.
(21:54):
Human disturbance is significant, just general
activity from boats. Tourism can cause stress and
make them abandoned. Haul out sites, especially
during pupping season and disease outbreaks can also hit
populations hard sometimes. It's a long list of challenges.
Can you elaborate a bit more on how pollution and climate change
specifically impact them? Sure, with pollution those
(22:14):
chemical contaminants we mentioned can accumulate up the
food chain. So seals being high up can get
high doses leading to immune suppression, making them more
susceptible to disease and reproductive problems.
Oil spills destroy the insulating properties of their
fur leading to hypothermia plus internal damage of ingested
marine debris. Well, entanglement is horrific
(22:35):
and ingested plastic can cause blockages or starvation.
And climate change beyond habitat loss.
The shifts in prey are a really big one.
If the fish they rely on move north or into deeper water
because of changing temperatures, the seals have to
adapt, expend more energy foraging, or they might
struggle. The timing of seasonal events
like plankton blooms that support fish populations can
(22:58):
also get disrupted, affecting the whole food chain they depend
on. It creates a lot of uncertainty
for them. It sounds like they're facing
pressures from many angles. What's being done to protect
them? Are there conservation efforts?
Yes, definitely. Legal protection is fundamental
in many countries. Laws like the Marine Mammal
Protection Act in the US or the Habitats Directive in the EU
(23:20):
make it illegal to harass or kill them and provide frameworks
for habitat protection. Like marine protected areas?
Exactly Designating specific areas as protected helps
safeguard critical habitats likehaul out sites and foraging
grounds. There are also efforts to
control pollution, both nationally and through
international agreements. What about research?
Research and monitoring are crucial.
(23:41):
Tracking population numbers, assessing health, understanding
threats that information guides,conservation actions, plus
public awareness and education play a role in reducing
disturbance and building supportfor conservation.
And there are often response networks ready to help stranded
animals or investigate disease outbreaks.
How effective are these measures?
Is habitat protection working? It can be quite effective, yes.
(24:05):
Protecting key haul out sites has definitely helped
populations recover or stabilizein many areas.
Reducing specific pollutants hasalso shown benefits.
But challenges remain. Absolutely.
Addressing diffuse pollution, managing fisheries sustainably
to reduce bycatch and especiallytackling the massive challenge
of climate change. These are ongoing and complex
issues. The effectiveness really depends
(24:27):
on the scale of the threat and the resources put into
consistent adaptive management. Shifting slightly, do harbor
seals have any agricultural significance?
Not directly, no. They aren't farmed or used in
agriculture. Their significance is tied to
the marine ecosystem. A healthy marine environment
which they contribute to can support healthy fisheries, which
(24:48):
are economically important, sometimes alongside coastal
agriculture. So it's more of an indirect link
through ecosystem health. So their main role in
conservation is linked to their ecological function.
Primarily, by being predators, they help maintain balance.
By being indicators, they tell us about ocean health.
Their legal status often helps conserve wider marine
(25:09):
biodiversity, and sometimes carefully managed ecotourism
focused on seals can generate funds and support for broader
conservation goals. They sound incredibly useful for
scientific research too. Immensely, yeah.
As those indicators of ecosystemhealth, studying their diet,
contaminant levels and population trends gives us vital
data on pollution and climate change impacts.
(25:29):
Their Physiology is fascinating.Studying their diving
adaptations, how they manage oxygen.
Thermal regulation teaches us a lot about marine mammal biology
in general. They're key subjects in
conservation biology for developing management
strategies, and studying how they interact with human
activities helps us find ways tominimize conflict and promote
(25:49):
coexistence. How do scientists actually study
them? What tools do they use?
A whole range field observation is still fundamental.
Counting seals that haul outs using photo ID to track
individuals based on their unique spot patterns.
What about tracking their movements?
Tagging is really important. Small satellite tags, VHF radio
tags, or time depth recorders can be attached noninvasively,
(26:11):
usually to track where they go, how deep they dive, for how
long. And lab work.
Yes, analyzing tissue samples, skin, blubber, blood or even
scat can tell us about their genetics, diet, health, exposure
to contaminants. Acoustic monitoring can record
their underwater sounds. Remote sensing, like satellite
imagery or drones can help assess habitats.
(26:31):
Camera traps that haul out sitescapture behavior.
It's very multidisciplinary. Despite all that, are there
still things we don't know, Gapsin our knowledge?
For sure, we always need more upto date fine scale information
on population numbers and genetic connectivity across
their vast range. Understanding the full long term
impacts of climate change is a huge ongoing task.
(26:54):
What else? We need better data on the
cumulative effects of different human disturbances.
Disease surveillance could be more systematic, especially for
emerging threats. Refining our understanding of
their precise foraging ecology, Exactly what they eat, where and
when and how that might be changing is still important.
And more long term studies of their social behavior could
(27:15):
reveal a lot too. There's always more to learn.
It's clear there are really important species, both
ecologically and for what they can teach us.
Absolutely. Their role as indicators of
marine health really can't be overstated.
Studying them gives us a window into the condition of our
coastal. Oceans away to monitor the
impacts of pollution and climatechange.
Precisely, and their unique Physiology continues to provide
(27:38):
insights into how mammals adapt to challenging marine
environments. All this knowledge feeds
directly into conservation biology, helping us make better
decisions about how to protect them and their habitats.
And understanding those interactions with human
activities is key for finding ways to share the coastlines
more sustainably. Exactly.
Promoting coexistence is vital, but as we've discussed, there
(28:01):
are still significant knowledge caps.
Continued research is essential if we want to ensure their
effective conservation in the long run.
So we've covered a lot of groundtoday in our deep dive on the
harbor seal from their amazing distribution across the Northern
Hemisphere. To their incredible physical
adaptations for life in the water, their crucial ecological
roles as both predator and prey.And unfortunately, the many
(28:23):
threats they face, from pollution and habitat loss to
climate change. It's a complex picture for a
species that's both resilient and vulnerable.
Indeed, so as we wrap U maybe something for you, our listener
to think about. Given how interconnected
everything is in the ocean, whatresponsibility do we have to
(28:44):
really understand and protect a species like the harbor seal?
And thinking about everything we've discussed, what questions
do you now have about their future in our changing?
World that's a powerful thought to end on Their future is in
many ways tied to the future health of the oceans themselves.
Thank you so much for joining uson this deep dive.
It's been fascinating to exploretheir world.
(29:04):
Credit to munaturedocumentariesmu.com,
owned by Karl Heinz Mueller.
You're listening to MOO nature documentaries.
Welcome to the deep dive. Today we're taking a look, a
close look at a really fascinating animal you find
across the Northern hemisphere, the harbor seal.
That's right, Volkovich Celina, a truly widespread marine
mammal. And you mentioned something
amazing before we started. Some of them can dive what, over
(00:21):
100 meters down? Easily.
Yeah, they're remarkable swimmers and divers.
We pulled together quite a bit of research, various sources to
really get under the skin of these seals.
So our mission today for you, the listener, is to get a solid
understanding of these animals, their biology, how they live,
their place in the environment without getting bogged down and,
you know, overly technical. Stuff exactly.
(00:42):
We want to explore what makes them tick, how they're adapted
to so many different coastlines from icy Arctic edges to more
temperate zones, and the challenges they're up.
Against OK, sounds great. Let's start with where you'd
actually find them. Their distribution seems.
Huge. It really is impressive.
They span both the Atlantic and the Pacific.
So like where specifically in the Atlantic?
(01:03):
We'll think North America from the Arctic down the coast to
about the Mid-Atlantic U.S. states.
And then over in Europe, you're looking at Iceland, Norway, the
British Isle, all the way down to northern France.
And the Pacific? Similar story Bering Sea,
Alaska, right down the North American coast of Baja
California and then across the ocean, eastern Asia.
(01:26):
So Russia, Japan, that area. That covers a massive amount of
coastline and they're not too picky about the type of coast,
are they Rocky shores? Sandy beaches.
That's one of their key strengths, adaptability.
They thrive in diverse coastal environments.
Rocky shores, yes. Sandy beaches, absolutely.
Estuaries are particularly important to.
Estuaries. Why they're specifically?
Because they're often really rich foraging grounds, lots of
(01:49):
fish where the fresh water mixeswith the sea.
But wherever they are, they absolutely depend on haul out
sites. Haul out sites, that's their
base on land right for resting. Exactly.
Resting, warming up, molting andcrucially for raising their
pups, they need these spots on land or sometimes ice.
What makes a good haul out spot?I imagine they can't just pick
anywhere. Up Several things matter.
(02:11):
Tidal patterns are a big one. They often haul out at low tide.
They also look for places with minimal human disturbance and
fewer predators around. Makes sense.
So what kind of places fit the bill?
You can be sandy beaches, rocky areas, mud flats, even man made
structures sometimes like docks or Piers if they feel secure
(02:32):
there. Interesting they'd use human
structures. You mentioned ice too.
Yeah, and the more northern parts of their range, they
definitely use ice flows, especially for pupping.
But it's worth noting they're generally less reliant on ice
than, say, Arctic seal specialists.
OK, so they need land or ice, but they're clearly masters of
the water too. That 100m dive depth is proof of
that. Oh absolutely.
(02:53):
There are depth swimmers very capable in open water.
Can you give us a couple of examples of how their habitat
choice differs regionally, like Pacific Northwest versus North
Atlantic? Sure.
So in the Pacific Northwest you'll often find them favoring
sheltered bays and inlets. Contrast that with the North
Atlantic, where rocky coastlines, offshore islands are
more typical habitats. In Europe, like the Wadden Sea.
(03:15):
Right. The Wadden Sea is a classic
example. Huge populations there rely
heavily on those extensive intertidal sand and mud flats
for both resting and feeding. It really highlights their
flexibility, but with coasts being so popular for humans too,
how does our activity affect them?
That's a major issue. Coastal development can destroy
(03:35):
haul out sites. Pollution degrades their habitat
and food sources. Boat traffic can disturb them,
especially during sensitive times like breeding season.
So conservation efforts need to focus on protecting those
habitats. Definitely protecting their key
haulout and foraging areas is a critical part of conservation.
Now what about movement? Do they migrate long distances
(03:57):
or mostly stick to 1 area? They're generally considered
pretty sedentary. They tend to have defined home
range. So no epic migrations.
Not really, no. They do make localized movements
though. Yeah, these are mostly driven by
seasonal shifts and where their food is, or finding the best
spots for breeding or molting. Think of it like moving between
different neighborhoods rather than across countries.
(04:18):
OK, so if the fish move they might follow them locally?
Exactly, or they'll move to specific sheltered sites for
pupping season, then shift back to fallow prey patterns
afterwards. But it's usually all within that
broader home range. That makes sense.
Looking back historically, has their range always been this
widespread or has it changed? Historically, yeah, they had a
(04:39):
very broad distribution, but during the 19th and early 20th
centuries, hunting pressure was intense in many.
Areas, right? Sealing was a major industry.
It was, and it led to significant population declines
and even local extinctions in some places.
But things have improved. Thankfully, yes.
Conservation laws like the Marine Mammal Protection Act in
(05:00):
the US, passed in 1972, have been really important.
They've allowed many populationsto stabilize and even increase.
That's good news. So the current picture is stable
overall. Currently, they're still found
across those North Atlantic and Pacific coasts, but it's a bit
patchy. Some populations are doing quite
well, thriving even. Others are still considered
(05:21):
vulnerable because of ongoing pressures like habitat loss or
accidental capture and fishing gear.
So a mixed bag really. Success in some areas, ongoing
concerns and others. Precisely, it requires continued
monitoring and management, region by region.
OK, let's shift gears a bit. We know where they live, but how
do they live there? What physical traits allow them
(05:42):
to thrive in that marine environment?
Well, I've got a whole suite of fantastic adaptations.
First off, their body shape is very streamlined kind of
torpedo. Like just winging efficiency,
right? Less drag.
Exactly. Makes moving through water much
easier. Yeah.
And then, of course, there's theblubber, a thick layer under the
skin. The classic seal feature for
warmth. Primarily for insulation, yeah,
(06:04):
Essential in those cold waters, but it's also a really important
energy reserve. OK.
And they're flippers. How do they?
They've got 4 limbs and hind limbs modified into flippers.
The front ones are smaller, mostly used for steering, you
know, maneuvering. The powerful thrust comes from
the larger hind flippers. Giving them that agile movement
underwater? What about their appearance?
(06:25):
Their fur. Their fur provides some
insulation to, but its main rolemight be camouflage.
It's typically Gray or brown, but with a unique pattern of
spots or rings for each seal. So they blend in with rocks or
the sea bed. Pretty much helps them avoid
predators and maybe sneak up on prey.
And how do they sense their world, especially underwater,
(06:47):
where it can be dark or murky? That's where they're whiskers
come in the Vibra Sea. They're incredibly sensitive.
To touch. To vibrations, really.
They can detect the tiny water movements made by fish swimming
nearby, even when they can't seethem clearly.
Wow, like underwater radar? What about eyesight?
It's adapted for underwater vision too.
They have large lenses and lots of rod cells in their retinas
(07:09):
which helps them see better in low light conditions.
And they can close their nostrils and ears.
Yep, essential for diving. Keeps the water.
Out all sounds perfectly designed.
Does their look change much through their lives or with the
seasons? Oh yes, pups are born with a
special coat called lanugo. It's soft, woolly, often whitish
or light Gray. But they don't keep that.
(07:29):
No, they usually shed it either just before or very shortly
After Earth. Then, as juveniles, they develop
that denser, waterproof adult fur, and their individual spot
patterns become clearer as they age.
And adults, do they change appearance seasonally?
The main change is the annual molt.
After the breeding season, they shed their old worn out fur and
(07:50):
grow a new coat. Must take a lot of energy.
It does. They often spend more time
hauled out during the molt, partly to conserve energy and
help the shedding process along.The new coat usually looks
brighter, more vibrant. We talked about blubber for
warmth. How else do they manage body
temperature, especially going between cold water and
potentially warm land? Blubber is key, but their fur
(08:12):
and skin also play roles in insulation and, importantly,
releasing excess heat when they're on land.
They also have a neat trick in their flippers.
Oh yeah? What's that?
It's called countercurrent heat exchange.
Basically, the warm blood flowing out to the flippers runs
right next to the cold blood coming.
Back so the outgoing blood warmsup the returning blood.
Exactly. Helps keep their core body
(08:34):
temperature stable and minimizesheat loss through the
extremities. Really efficient.
That's clever biology. Any other tricks?
Behavior is important too. Basking in the sun on a rock
warms them up. Spending more time in the water
can cool them down. They can even adjust their
metabolic rate to some extent, generating more heat if needed
or slowing things down to conserve energy.
(08:55):
The whole toolkit for thermoregulation now are males
and females. Easy to tell apart just by
looking. Not really.
The differences are quite subtle, especially compared to
some other seal species. How so?
Well, males tend to be slightly larger on average, maybe 1.6 to
1.9 meters long, weighing 70 to 150 kilograms.
Females are more like 1.5 to 1.7meters in 60 to 110 kilos.
(09:19):
So a slight size difference, butnot huge.
Right. And their coloration, the spot
patterns are very similar. Males might look a bit bulkier,
perhaps around the neck and shoulders, especially mature
males, but often you can't reliably tell them apart just by
sight alone, unless maybe you see specific reading behaviors.
OK. And you mentioned there wide
range earlier, does that mean there are different types like
(09:40):
subspecies in different? Areas.
Yes. There are generally 5 recognized
subspecies, each adapted to its specific region.
Can you give us a quick rundown?Sure, there's the Eastern
Atlantic subspecies PV virgilinafound around the UK, Baltic,
Norway, Iceland, then the Pacific one PV retarded along
the North American Pacific Coast.
(10:01):
The Western Atlantic PV con colour from eastern Canada down
towards New York. The carill seal give you
stationary near Japan and the Kuril Islands.
And one more. Yes, the really unique 1 the
Ungava seal PD Malone. It's a fresh water subspecies
living in lakes in Quebec, Canada.
It doesn't migrate to the sea at.
All freshwater seal. That's incredible.
(10:22):
Really shows their adaptability.It absolutely does.
Each subspecies reflects adaptations to local conditions,
water temperature, prey types, things like that.
OK, welcome back. Let's dive into the harbor seals
life cycle now. When does the breeding season
kick off for them? It happens once a year, but the
timing really varies depending on where they are.
It's all about lining up the birth of pups with the best
(10:43):
environmental conditions for survival.
So warmer places versus colder places.
Generally, yeah. In temperate spots like the
Northeast Pacific, think late spring, early summer, maybe May
to July. In the colder Northeast
Atlantic, it shifts a bit later,maybe June to August.
And way up. North in the Arctic and
subarctic, it tends to be even later, July through September.
(11:04):
Take advantage of those short, warmer months.
Makes sense. So walk us through the life
stages, birth onwards. OK, pups are born usually on
land or ice, and they're quite developed at birth, what we call
precocial. They shed that fuzzy lanugo coat
quickly. Then comes weaning.
It's surprisingly short, only about four to six weeks, but the
(11:26):
mothers milk is incredibly rich,very high in fat.
To help them bulk. Up quickly?
Exactly. Rapid growth, building up that
essential blubber layer before they have to fend for
themselves. Weaning is a critical transition
to independence. So after just a month or so,
they're on their own. Pretty much they enter the
juvenile stage where the big task is learning to hunt
successfully. It's a tough time, lots of
(11:48):
growth still happening, but they're also very vulnerable.
To predators just figuring things.
Out both, yes. Then if they make it through
that they reach sexual maturity.Females usually around three to
five years old. Males may be a year or two
later, Four to six years typically.
And then they start breeding themselves.
Right adulthood involves those annual breeding cycles.
(12:09):
Mating usually happens in the water quite soon after the
female weans her pup, and they have this fascinating adaptation
called delayed implantation. Delayed implantation What's?
That it means the fertilized eggdoesn't immediately implant in
the uterus and start developing.It waits for a few months.
Why would it do? That it effectively times the
pregnancy so that the birth happens about a year after the
(12:30):
previous one, right back in thatoptimal pupping season.
It synchronizes the whole cycle.'S amazing timing and how long
can they live? In the wild, a good lifespan is
up to 25, maybe 30 years. OK, so back to mating.
How do they actually find and choose a partner in the big
ocean? It seems males do a lot of the
work attracting females. They produce underwater
(12:52):
vocalizations, grunts, growls, sometimes louder roar like.
Sounds advertise themselves. Essentially yes, to attract
females and maybe establish somesort of temporary territory
underwater. It's thought that females might
assess the quality of a male based on these calls.
Like a vocal display? Kind of Males might also perform
(13:13):
physical displays in the water, your females showing off their
strengths and fitness. Some males might defend specific
underwater areas near where females haul out.
So the females choose based on the calls and maybe the
territory. It seems likely the quality of
his spot, the intensity of his calls, his physical condition
probably all factors into her choice, and timing is linked to
that annual cycle happening soonafter weaning.
(13:35):
Is it always harbor seal with harbor seal or do they ever mix
with other seal types? Hybridization breeding with
closely related species like thegrey seal has happened, but it
seems pretty are mostly documented in captivity
actually. Why not so much in the wild?
Usually, differences in their preferred habitats and breeding
behaviors keep them reproductively isolated.
(13:56):
Although, you know, with environments changing, maybe
interactions could become more common in the future.
It's something researchers keep an eye on.
Interesting. Now parenting, you said weaning
is quick. What's the parental care like
before that? It's all down to the mother's
soul maternal care. She forms a strong bond with her
pup using vocalizations and scent.
And provides that super which milk?
(14:17):
Yes, milk with maybe 4050% fat content, essential for that
rapid growth and blubber. She's also very protective,
guarding the pup from danger or disturbances.
But then at 4-6 weeks, it's justover.
It's a relatively abrupt end. The mother actively encourages
the pup to become independent. Being born precocial really
(14:37):
helps the pup manage that transition.
Gives them a head start. How does a pup physically change
as it grows into an adult? Well, the size difference is
huge. Pups start around, say, 8 to 12
kilograms. Adults can be anywhere from 55
up to 170 kilos. Wow, and they're coat.
That fluffy lanugo gets replacedby the sleeker spotted adult
coat. The spots often become more
(14:59):
defined. Maybe the overall colour darkens
a bit as they. Mature and behaviorally from
dependent pup to independent hunter.
That's the biggest shift. They have to learn to find and
catch all their own food. Juveniles might actually be a
bit more social than adults for a while, maybe learning from
each other before adopting the more solitary adult foraging
style. Again, it's a vulnerable stage.
(15:21):
Right, let's talk about that food.
What exactly is on the menu for a harbor seal?
They're quite opportunistic and have a really varied.
It depends a lot on where they live and what time of year it.
Is generally fish. Fish are definitely a major
component. Things like herring, cod,
mackerel, salmon, various rockfish, flatfish, lots of
different kinds. But they don't stop there.
(15:42):
Invertebrates too. Squid, octopus, shrimp, crabs.
They'll eat those quite readily if they're available.
So the local seafood buffet, essentially.
Pretty much you see regional differences, like in the North
Sea sand eels are super important.
Off California, they might be a more squid and octopus, and the
diet gifts seasonally too, following prey availability.
(16:02):
How do they catch it all using those whiskers?
Whiskers are key for detecting prey, especially in low light.
They're skilled hunters. Mostly they forage alone, but
you might see them gather if there's a big concentration of
fish, like a herring school. And they can dive deep to get
it. You mentioned 100 meters, but
sometimes even deeper. Dives over 500 meters have been
(16:23):
recorded, though maybe not routinely, but they can
certainly access prey quite deepin the water column.
By getting all these different things, what effect do they have
on the ecosystem? Do they control other
populations? They definitely played a role in
regulating populations of their prey.
Eating lots of different fish helps prevent any one species
from dominating and influences the size and age structure of
(16:45):
those fish populations. Same for invertebrates.
So they help maintain balance. Exactly.
By keeping prey populations in check, they contribute to the
overall health and balance of the coastal and estuarine
ecosystems they live in. Their specific impact varies
locally, of course. OK, so they're predators, but
what praise on them? They have some formidable
(17:05):
natural predators. Orcas, killer whales, are
probably the main one. They're very sophisticated
hunting strategies for seals. Anyone.
Else Large sharks, definitely. Great whites, for example, are
known predators. They often use ambush tactics.
Up in the Arctic, polar bears can hunt them, especially when
they're held out on ice. And humans historically.
Historically, yes, humans were amajor predator, Less so now in
(17:29):
most areas due to legal protections, but accidental
entanglement in fishing gear is still a big problem.
What defences do the Seals have against these threats?
Well, vigilance is key. When hauled out, they're often
wary, and being in a group can offer more eyes looking out for
danger. Safety in numbers.
To some extent in the water, their speed and agility are
their best defence. Quick escapes hauling out itself
(17:53):
is a way to avoid aquatic predators like sharks or orcas,
at least temporarily. And camouflage.
That helps too. Ending in makes them harder to
spot. And of course they're diving
ability. Being able to stay underwater
for up to 30 minutes is pretty good way to wait out a thread at
the surface. 30 minutes, that's incredible breath holding.
How does the amount of food available influence where they
(18:16):
go or what they do? Food availability is a huge
driver of their behavior. If food is scarce locally,
they'll travel further on foraging trips.
They're diving patterns. How deep they go, how long they
stay down will change depending on where the prey is
concentrated. And we mentioned seasonal
movements. They'll definitely follow prey
migrations like salmon runs or spawning aggregations of fish
(18:37):
like capelin or sand Lance. So they're constantly adapting
their behavior to the food landscape.
Absolutely. They tend to favor habitats
known for consistent prey availability, like areas near
river mouths or with strong currents that might concentrate
fish. Their life revolves around
finding enough to eat. OK, we've covered their diet and
predators. Let's zoom out a bit now to
(18:59):
their broader role in the ecosystem.
How would you summarize their ecological importance?
They're really integral as predators.
They regulate fish and invertebrate populations,
influencing that whole food web structure, as we discussed.
And as prey. As prey for top predators like
orcas and sharks, there are key link in transferring energy up
the food chain. What else?
Their waste products actually contribute nutrients back into
(19:22):
the water, which helps support the base of the food web, the
plankton and algae. And because their populations
can respond to environmental changes, they serve as important
indicators of ecosystem health. Indicators.
How so? Well, if seal populations
decline sharply in an area, it might signal problems like
pollution, disease or major shifts in prey availability,
(19:43):
reflecting broader issues in themarine environment.
I see. And they sometimes come into
conflict with humans, right? Fisheries.
Yes, that can happen. There's sometimes perceived
competition for commercially important fish species, which
can lead to conflict. Beyond predator prey, what other
interactions do they have with species?
Well, there's competition. Not just conflict with humans,
(20:04):
but also potentially with other marine predators like sea lions
or even some sea birds that might target similar food
sources. Any positive interactions like
symbiosis? Strict symbiosis where both
species clearly benefit isn't really well documented.
Yeah, you might see loose associations like gulls
scavenging scraps from a seals kill.
That's more commensalism. One benefits, the other isn't
(20:26):
really affected. Cleaner fish following them
around or anything like that. Not that we know of, no.
But their general role in keeping the ecosystem balanced
indirectly benefits many other species.
Of course, they also host parasites like internal worms,
which is a different kind of interaction.
OK, let's pivot to conservation.What's their official status?
(20:46):
Are they endangered? Globally, the good news is
they're listed as Least Concern by the IUCN.
Well, that's good. It is overall, but, and this is
important, that's the global picture.
Some specific regional populations are facing
significant threats and might beconsidered threatened or
vulnerable at a local level. So what are those main threats
they face, even if the global status is OK?
(21:09):
There are several key ones. Habitat degradation is a big
one, losing those vital haul outsites to coastal development.
Pollution is another major concern.
What kind of pollution? Things like heavy metals, PCB's,
pesticides, persistent organic pollutants that build up in
their bodies and can affect their health, their immune
systems, even reproduction. Oil spills are devastating,
(21:31):
obviously, and marine debris, plastics while fishing Nets is a
huge hazard. Entanglement.
Entanglement, yes, which can injure or drown them.
And ingestion, too. Then there's climate change.
How does that affect them? It alters their habitat.
Think loss of sea ice in the North Sea, level rise, flooding,
haul out sites. It also shifts the distribution
and abundance of their prey species.
(21:54):
Human disturbance is significant, just general
activity from boats. Tourism can cause stress and
make them abandoned. Haul out sites, especially
during pupping season and disease outbreaks can also hit
populations hard sometimes. It's a long list of challenges.
Can you elaborate a bit more on how pollution and climate change
specifically impact them? Sure, with pollution those
(22:14):
chemical contaminants we mentioned can accumulate up the
food chain. So seals being high up can get
high doses leading to immune suppression, making them more
susceptible to disease and reproductive problems.
Oil spills destroy the insulating properties of their
fur leading to hypothermia plus internal damage of ingested
marine debris. Well, entanglement is horrific
(22:35):
and ingested plastic can cause blockages or starvation.
And climate change beyond habitat loss.
The shifts in prey are a really big one.
If the fish they rely on move north or into deeper water
because of changing temperatures, the seals have to
adapt, expend more energy foraging, or they might
struggle. The timing of seasonal events
like plankton blooms that support fish populations can
(22:58):
also get disrupted, affecting the whole food chain they depend
on. It creates a lot of uncertainty
for them. It sounds like they're facing
pressures from many angles. What's being done to protect
them? Are there conservation efforts?
Yes, definitely. Legal protection is fundamental
in many countries. Laws like the Marine Mammal
Protection Act in the US or the Habitats Directive in the EU
(23:20):
make it illegal to harass or kill them and provide frameworks
for habitat protection. Like marine protected areas?
Exactly Designating specific areas as protected helps
safeguard critical habitats likehaul out sites and foraging
grounds. There are also efforts to
control pollution, both nationally and through
international agreements. What about research?
Research and monitoring are crucial.
(23:41):
Tracking population numbers, assessing health, understanding
threats that information guides,conservation actions, plus
public awareness and education play a role in reducing
disturbance and building supportfor conservation.
And there are often response networks ready to help stranded
animals or investigate disease outbreaks.
How effective are these measures?
Is habitat protection working? It can be quite effective, yes.
(24:05):
Protecting key haul out sites has definitely helped
populations recover or stabilizein many areas.
Reducing specific pollutants hasalso shown benefits.
But challenges remain. Absolutely.
Addressing diffuse pollution, managing fisheries sustainably
to reduce bycatch and especiallytackling the massive challenge
of climate change. These are ongoing and complex
issues. The effectiveness really depends
(24:27):
on the scale of the threat and the resources put into
consistent adaptive management. Shifting slightly, do harbor
seals have any agricultural significance?
Not directly, no. They aren't farmed or used in
agriculture. Their significance is tied to
the marine ecosystem. A healthy marine environment
which they contribute to can support healthy fisheries, which
(24:48):
are economically important, sometimes alongside coastal
agriculture. So it's more of an indirect link
through ecosystem health. So their main role in
conservation is linked to their ecological function.
Primarily, by being predators, they help maintain balance.
By being indicators, they tell us about ocean health.
Their legal status often helps conserve wider marine
(25:09):
biodiversity, and sometimes carefully managed ecotourism
focused on seals can generate funds and support for broader
conservation goals. They sound incredibly useful for
scientific research too. Immensely, yeah.
As those indicators of ecosystemhealth, studying their diet,
contaminant levels and population trends gives us vital
data on pollution and climate change impacts.
(25:29):
Their Physiology is fascinating.Studying their diving
adaptations, how they manage oxygen.
Thermal regulation teaches us a lot about marine mammal biology
in general. They're key subjects in
conservation biology for developing management
strategies, and studying how they interact with human
activities helps us find ways tominimize conflict and promote
(25:49):
coexistence. How do scientists actually study
them? What tools do they use?
A whole range field observation is still fundamental.
Counting seals that haul outs using photo ID to track
individuals based on their unique spot patterns.
What about tracking their movements?
Tagging is really important. Small satellite tags, VHF radio
tags, or time depth recorders can be attached noninvasively,
(26:11):
usually to track where they go, how deep they dive, for how
long. And lab work.
Yes, analyzing tissue samples, skin, blubber, blood or even
scat can tell us about their genetics, diet, health, exposure
to contaminants. Acoustic monitoring can record
their underwater sounds. Remote sensing, like satellite
imagery or drones can help assess habitats.
(26:31):
Camera traps that haul out sitescapture behavior.
It's very multidisciplinary. Despite all that, are there
still things we don't know, Gapsin our knowledge?
For sure, we always need more upto date fine scale information
on population numbers and genetic connectivity across
their vast range. Understanding the full long term
impacts of climate change is a huge ongoing task.
(26:54):
What else? We need better data on the
cumulative effects of different human disturbances.
Disease surveillance could be more systematic, especially for
emerging threats. Refining our understanding of
their precise foraging ecology, Exactly what they eat, where and
when and how that might be changing is still important.
And more long term studies of their social behavior could
(27:15):
reveal a lot too. There's always more to learn.
It's clear there are really important species, both
ecologically and for what they can teach us.
Absolutely. Their role as indicators of
marine health really can't be overstated.
Studying them gives us a window into the condition of our
coastal. Oceans away to monitor the
impacts of pollution and climatechange.
Precisely, and their unique Physiology continues to provide
(27:38):
insights into how mammals adapt to challenging marine
environments. All this knowledge feeds
directly into conservation biology, helping us make better
decisions about how to protect them and their habitats.
And understanding those interactions with human
activities is key for finding ways to share the coastlines
more sustainably. Exactly.
Promoting coexistence is vital, but as we've discussed, there
(28:01):
are still significant knowledge caps.
Continued research is essential if we want to ensure their
effective conservation in the long run.
So we've covered a lot of groundtoday in our deep dive on the
harbor seal from their amazing distribution across the Northern
Hemisphere. To their incredible physical
adaptations for life in the water, their crucial ecological
roles as both predator and prey.And unfortunately, the many
(28:23):
threats they face, from pollution and habitat loss to
climate change. It's a complex picture for a
species that's both resilient and vulnerable.
Indeed, so as we wrap U maybe something for you, our listener
to think about. Given how interconnected
everything is in the ocean, whatresponsibility do we have to
(28:44):
really understand and protect a species like the harbor seal?
And thinking about everything we've discussed, what questions
do you now have about their future in our changing?
World that's a powerful thought to end on Their future is in
many ways tied to the future health of the oceans themselves.
Thank you so much for joining uson this deep dive.
It's been fascinating to exploretheir world.
(29:04):
Credit to munaturedocumentariesmu.com,
owned by Karl Heinz Mueller.
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