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March 26, 2025 14 mins

Join Ranger Rosie Holdsworth to uncover the mystery of the leaping shark.  

On a boat off Cornwall, wildlife guide Jenny spots a huge animal she’s never seen before jumping out of the water.  But what exactly has she witnessed?   

Across the world in Florida, shark-obsessed Dr Molly Kressler sets off on a mission to discover more about what is beneath the calm of the surface. More than that, she wants everyone else to be able to get to know and love creatures of the deep too.  

[Ad] Wild Tales is sponsored by Cotswold Outdoor, your outside retailer and epic guides to adventure.   
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Production:   
Host: Rosie Holdsworth   
Producer: Marnie Woodmeade 
Sound Editor: Jesus Gomez 
Additional research: Funbi Bakare
  
Discover more:   
Find out more about thresher sharks at sharkstrust.org.uk.  

If you want to be kept up to date with Molly’s research, you can find her on X, Instagram or TikTok at @marinemollyk.  

For incredible views of the Cornish coast, why not visit Trevose Head? Jutting out into the Atlantic, you can see for miles. Shark sightings not guaranteed (but possible!)  

Special thanks to Dr Molly Kressler and Jenny from Padstow Sea Life Safaris.  
  
Follow Wild Tales on your favourite podcast app or on Instagram @wildtalesnt. If you'd like to get in touch with feedback, or have a story idea, you can contact us at podcasts@nationaltrust.org.uk 

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Transcript

Episode Transcript

Available transcripts are automatically generated. Complete accuracy is not guaranteed.
JENNY SIMPSON (00:34):
It's a beautiful November day, we load up the
passengers, full boat, we goround to an island where there's
seals, all of a sudden somethingjust leaps out of the water.

ROSIE HOLDWORTH (00:53):
Hello and welcome to Wild Tales. I'm
Ranger Rosie Holdsworth andtoday we're heading to Colmore.
To untangle one of the world'smost endangered and cryptic
species.

JENNY SIMPSON (01:10):
First split-second reaction is a
dolphin, but as soon as it camea bit further up out the water,
the shape of it, the way inwhich it was vertically coming
straight up in the air, itdefinitely wasn't a dolphin.

ROSIE HOLDWORTH (01:27):
Jenny is a wildlife guide in Padstow. A
quaint seaside town nestled inthe Camel Estuary on the
Atlantic coast of Cornwall.Spending hundreds of hours out
at sea each year, Jenny has asuspicion about what she's seen.

JENNY SIMPSON (01:41):
You do get some people who say to us, there
aren't any sharks here, arethere? And I just say to them,
well, anywhere there's ocean,there are sharks.

ROSIE HOLDWORTH (01:50):
Jenny knows that when someone says shark,
all we think of is jaws full ofteeth.

JENNY SIMPSON (02:01):
I remember seeing a basking shark and there was a
little boy in the boat and hewas so scared. And I was like,
this is really exciting. It'snot got big teeth. Just because
it was a big shark, he was sureit was something scary.

ROSIE HOLDWORTH (02:16):
Jenny has to find out what she's seen.
When it comes to sharks, beingable to tell people on board
exactly what is out there can bethe difference between
fascination and fear.
But with just that glimpse of ashape, how could she do it?

MOLLY KRESSLER (02:34):
So I'm American. When I was born, my grandparents
moved to Florida in a reallybeautiful place called Vero
Beach. You'd wake up and you'dsee manatees and dolphins and
pelicans. And it's just like abreeding ground for marine
biologists.

ROSIE HOLDWORTH (02:47):
This is Molly.

MOLLY KRESSLER (02:48):
I was kind of the target demo of something in
the U. S. Called Shark Week onDiscovery Channel. And it
coincided pretty much annuallywith our vacation down to my
grandparents' house. So itreally was this like perfect
storm. So we'd watch Shark Week.
And then we would go to thebeach. And I remember some of my
siblings being absolutelypetrified of going near the
water. But I was more like, if Igo in the water, I might
actually see one of those sharksthat I saw last night.

ROSIE HOLDWORTH (03:11):
Unlike in the UK, in Florida, sharks are a
reasonably common sight. ForMolly, they start to become an
obsession.

MOLLY KRESSLER (03:20):
We would do surf fishing. You're literally
standing like ankle deep in thesurf. And you cast it as far as
you can. It's got a really bigweight on the end. And then it
plops in. And you know there'ssomething because it bends
really dramatically. And in thatmoment, everyone's screaming,
reel it in.

(03:40):
For a while, you have no ideawhat it is. And then it'll come
up in the swell. And when it'sin that wave, you kind of get a
good picture of it. And I justsaw that elongated gray body.
And I was like, that does notlook like the fish we're looking
for food-wise. We pulled in ajuvenile scallop hammerhead.
And I got to hold it. I've got aphoto of it somewhere. And
there's just this beam across myface. And I think I'm actually

(04:00):
wearing a hat at the time thathad a little shark embroidered
on it as well. So it's just likepicture perfect, kind of like a
shark obsessed girl.

ROSIE HOLDWORTH (04:09):
The shark obsessed girl grew up to become
Dr. Kressler, a marine ecologistspecializing in predator
behavior.

MOLLY KRESSLER (04:18):
I think getting to see that wildlife, it really
instilled in me the sense ofthere's so much going on beyond
that calm of the surface. I'mone of those people when you
give me a little bit and then...Everything else is kind of
hidden.
I'm like, no, no, I need more.And when you have the marine
environment, unless you're scubadiving or swimming, you really
can't see below. It instilledthose questions in me of like,

(04:38):
what else is out there?

ROSIE HOLDWORTH (04:40):
But Molly's thirst for knowledge kept coming
up against the same problem.

MOLLY KRESSLER (04:47):
We describe marine animals like sharks a lot
as being cryptic. So that's whenThey have these behaviours that
mean we don't really know whatthey're doing most of the time.
They can be really hard to find.
And any time you have a crypticspecies, you often have really
high research costs to eveninteract with the animal once,
let alone to understand whatit's doing over time. And that's

(05:07):
really where the power lies inunderstanding what a species is
and what we can do for it interms of conservation.

ROSIE HOLDWORTH (05:14):
Back across the Atlantic, Jenny is on a mission
to figure out what it is she'sseen. She quizzes local
fishermen and scours thenewspapers for sightings.

JENNY SIMPSON (05:24):
I'm thinking it seems a bit small for a basking
shark. I know we get blue sharksaround Cornwall, but this shark
seems a bit too sort of big andstocky. I'm kind of going
through it all in my head, butit wasn't until I got back to
the office and looking at somevideos of the style of breaching
of different sharks, I'm lookingat Mako sharks who kind of do

(05:47):
this stuff.
Of twist as they leap out. I waslike, that's not it. That's not
what we saw. Looking at a videoof a Thresher shark that comes
straight up and then splashesdown, the way in which it
breached matched perfectly.

ROSIE HOLDWORTH (06:00):
Thresher sharks are best known for their long
tails, which are almost the samelength as their body. They use
this tail like a whip to stuntheir prey. Known in some
cultures as the fox of the seafor their elusive nature, they
have a few cunning and deceptivefeatures.

JENNY SIMPSON (06:16):
Yeah, they've got these really dopey faces, almost
like they're kind of tuckingtheir bottom lip in.

ROSIE HOLDWORTH (06:22):
There are three species of Thresher sharks,
common, pelagic and big eye.Sharks, as a group of species,
are second only to amphibianswhen it comes to their risk of
extinction. To get a sighting oftheir leap is extraordinary,
once in a lifetime. But just twodays later...

JENNY SIMPSON (06:42):
We'd heard about a Thresher shark being caught.
In some fisherman's gear. Itwasn't an intentional catch with
bycatch. It just means thatthey're fishing for something
else and something accidentallygets caught in their nets that
they don't intend to catch.
But it had died and there's noway of knowing it's the same
animal. It just feels a littlebit sad to know that there's

(07:06):
these amazing beautiful animalsright up our coast but then you
know they can still fall foul togetting caught in nets.

ROSIE HOLDWORTH (07:13):
Is the problem with cryptic species. We often
only really know they're therewhen they're dead. And for
Thresher sharks, we know almostnothing about their lives.

MOLLY KRESSLER (07:23):
Threshers are a pelagic species, which means
that they spend most of theirlife out in kind of what is
described as the high seas. Whatthat means is the further from
shore, the further from humans'realm of day-to-day operations a
species exists, the harder itis, the more cryptic it is, to
understand.

ROSIE HOLDWORTH (07:43):
And this is a problem with many of the sharks
that Molly studies. She'sdetermined that there has to be
a way to get more information.And to do that, she needs to
find a method that a lot ofpeople can use.
After moving to Cornwall tostudy for her PhD, she attends a
conference and comes across agovernment study that's using

(08:04):
EDNA, or environmental DNA, tosearch for the presence of fish.
EDNA looks for tiny bits of DNAin the water. Like searching
your shower plug for hair. Thereare methods with medical-grade
filters, but they're tooexpensive and complicated to be
done on a large scale,especially if the species you're
looking for is out on the highseas. But at the conference, she

(08:27):
came across the Metaprobe.

MOLLY KRESSLER (08:32):
This is a 3D-printed sphere. It kind of
looks like the Death Star. Andinside are rolls of gauze. The
grocery store sometimes has it.It's much more affordable. And I
just, I saw the method and Ithink that the gauze-based might
be really powerful in answeringsome questions about shark
ecology.

ROSIE HOLDWORTH (08:50):
Molly knew she would need help, but she didn't
just want to test the samples.She wanted people to know more
about the sharks that driftthrough our coastlines. She
wanted someone who could takethe work and keep telling people
about the incredible speciesthat are there, day after day.

JENNY SIMPSON (09:11):
We had an email from Molly and asked if we would
help with her data collection.So she's looking for something
called EDNA and it helps them toidentify what species have been
around our coast, basically.

MOLLY KRESSLER (09:24):
So when they go out to do wildlife tours, I
would go out, take some watersamples. One of my favourite
things about going out withPadstow and Jenny was the fact
that every time I was able totalk a bit about it, answer
questions and also get to do myscience.
Hopefully we'll be publishingthe paper this year. But, the
kind of short version is that wefound that the gauze-based

(09:45):
method performs just as well asthe medical method.

ROSIE HOLDWORTH (09:49):
That means the Metaprobe, the Death Star full
of gauze found sharks.Porbeagles, Mako, and the
dopey-faced Thresher.

MOLLY KRESSLER (09:59):
That means that it's much more accessible. One
part of the project that welooked at was having citizen
scientists, sailors aroundCornwall take the Metaprobe out
with them and sample with it andcollect samples.

ROSIE HOLDWORTH (10:11):
For Molly, accessibility and people's
ability to engage with theMetaprobe is central to its
design.

MOLLY KRESSLER (10:18):
So I'm disabled. I have a congenital birth
defect. I'm missing four fingerson my left hand. And so I kind
of have always faced thisbarrier to entry, not because
I'm incapable of entering, butbecause of people's perception.
I've encountered experiences inthe field before where people
have outright told me that theyknow I can't do something and

(10:39):
therefore I shouldn't be giventhe opportunity to do it. I'll
just say I've proved them wrongevery time. There was one
instance where we had a threeand a half meter. Adult male
shark along the side of theboat.
And what you do is you have tohold them half out of the water
by the dorsal fin. I'll neverforget that moment hanging off
the side of the boat because Ihad the feeling in my head as I
was losing grip on that dorsalfin of this is where they're

(11:01):
going to disqualify me.
To have somebody, a mentor whojust said, it's fine. There's
something else you can do. Youcan still take lead on this
shark. And so when I was comingup with the field packs for the
metaprobes, I put materials inthere that could be understood
by children.
Adults with mental or learningdisabilities, as well as, you

(11:21):
know, your quote-unquote normaladults. And I was really pleased
because all the feedback was itwas easy, it was
straightforward, and the kidsloved it. And the kids found it
really interesting and they hadmore questions.

ROSIE HOLDWORTH (11:34):
The ocean is not our world. Everyone, no
matter their ability, needsspecialist equipment to be
there. So the accessibilitylimits are ones that we design.
To find these elusive sharksrequires everyone.

MOLLY KRESSLER (11:47):
A lot of populations are endangered,
critically endangered, but alarge proportion of sharks we
don't have enough data on. If wedon't know about them, we can't
help them, we can't protectthem.

ROSIE HOLDWORTH (11:58):
But despite all this, their huge diversity and
their increasing fragility, it'sundeniable that in the UK we're
still scared of sharks. We'rescared of the filter-feeding
basking sharks and thatdopey-faced Thresher.

JENNY SIMPSON (12:19):
The more people think they're scary, the less
they'll be interested in theirconservation.
Whereas actually, if you findout more about all their little
superpowers, and some of themare really fast, and some of
them use their tails like a whipto catch their prey. And so
hopefully the more people knowabout them, the more they're

(12:39):
around, the more we can talkabout them, the more people will
love them, maybe, hopefully.

ROSIE HOLDWORTH (12:57):
Thanks for joining me in this Wild Tale. Do
you have an amazing story aboutthe natural world? I'd love to
hear from you. You can find uson Instagram @wildtalesnt, where
you'll also find behind thescenes moments, nature's giants
and the micro wonders that makeour world the place it is. Use
the hashtag wildtaleswednesdaysor email podcasts at

(13:21):
nationaltrust.org.UK to send uspictures and stories of the
wildness around you.
Make sure you get every episodeby following Wild Tales on your
favourite podcast app. Evenbetter, leave us a review or
comment on an episode. I'd loveto hear what you think. Did you
know we also do video podcasts?They can be found on our YouTube

(13:43):
channel or on Spotify. Whileyou're there, why not check out
our history show, Back When, orfor smaller ears, Ranger Ray and
the Wildlifeers. See you nexttime.
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