Are horseshoe crabs…crabs?

How did horseshoe crabs get their names? Are they even crabs? And did they really exist before the dinosaurs? Early spring presents a unique opportunity to see these living fossils up close as they scuttle up to the shoreline along the Atlantic coast of the United States to mate and spawn. But Why traveled to Cape Cod to see horseshoe crabs up close. There we met up with horseshoe crab expert Sara Grady, who works for Mass Audubon. We learn all about these arthropods and answer questions like: Can humans eat horseshoe crabs? What’s with the pointy tails? Do they pinch? How long do they live? And what’s so special about their blood? 

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Episode Transcript

Jane (00:20):
This is But Why
Vermont Public. I'm JaneLindholm. On this show, we take
questions from curious kids justlike you, and we find answers.
If you've been listening for awhile, you already know we love
field trips at But Why, when weget out of the podcast studio
I've created in my closet and gosomewhere cool to make an

(00:41):
episode. Earlier this month, wegot the chance to go to the
ocean to learn more about a veryunique creature, one that's been
around since way before humans.In fact, this creature has been
alive and living mostly like itdoes today for well over 400
million years, and we got to gosee them! So to get you in the

(01:03):
mood for the episode, as we getstarted, I want you to close
your eyes and imagine you'realong on this field trip with
us.
We're on Cape Cod inMassachusetts. If you've never
heard of Cape Cod or you can'tpicture it, see if you can find
a map of the United States. Allright, I guess you can open your
eyes for that. Cape Cod is outat the eastern tip of

(01:25):
Massachusetts, and it's shapedkind of like how your arm would
look if you bent it up to showoff your bicep muscles. We're
heading out to a beach not farfrom where your elbow would
be--just above your elbow, butnot near your wrist. It's a
little too early to swim; thewater is really cold, although
it's always pretty cold in thispart of the Atlantic Ocean. But

(01:49):
it's a beautiful, sunny day, andwhen we arrive, it's almost high
tide, and we can see what look,from afar, kind of like big
rocks in the water. But as weget closer, we realize those
rocks are moving. Some of themare in the shallow water, and
some of them are already up onthe sandy shore. But these

(02:10):
aren't rocks. They've got longspikes for tails, and although
some of them are covered withbarnacles and mussel shells,
they're very much alivethemselves. They're horseshoe
crabs!

Benicio (02:22):
I'm Benicio. I live in Silver Spring, Maryland. I'm
nine years old. Why arehorseshoe crabs called horse
shoe?

Amir (02:34):
My name is Amir. I'm nine years old, and I live in
Limerick, Ireland. My questionis: why are horseshoe crabs
called horseshoe crabs?

Eva Rose (02:44):
Hi, my name is Eva Rose, and I'm eight years old,
and live in Vancouver, Canada.Why are horseshoe crabs called
horseshoe crabs if they don'tlook like crabs?

Jane (02:56):
You've sent us a lot of horseshoe crab questions, so
it's a good thing we've met upwith a scientist who studies
these incredible arthropods,because she can answer them all.

Sara Grady (03:07):
I'm Sara Grady. I'm the senior coastal ecologist for
Mass Audubon. We are at a littletucked away beach.

Jane (03:16):
I see what looks like a little hump of something heading
towards the shore. Is that ahorseshoe crab?

Sara Grady (03:24):
That is a horseshoe crab. They're coming into the
shore as the tide is coming in,so that they can lay their eggs.

Jane (03:33):
And that's what we're here to see. So that's very exciting
to me. Is it exciting to you asa horseshoe crab expert?

Sara Grady (03:38):
It's always very exciting. What's most exciting
is when you see a pair of them,because they form these pairs of
a female and a male, and theywalk around together.

Jane (03:49):
Oh, wait, there's three here.

Sara Grady (03:51):
Yeah, yeah. So they this is a pair of crabs. So
there's a larger crab in thefront, that's the female, and
then there's a smaller crab inthe back that is a male, and
then there's a second male thathas been attracted to the action
that's going on and is trying tomaybe get involved.

Jane (04:15):
Just to be clinical about this, the horseshoe crabs are
mating, and it's how they makemore horseshoe crabs.

Sara Grady (04:21):
So what happens is the female will dig a nest, and
actually, that female is doingthat right now, so she's digging
in the sand. She's going to layher eggs, and then they're going
to move forward a little bit,and then the male will fertilize
those eggs, and in about twoweeks, those eggs will hatch
out.

Jane (04:40):
I read that a female horseshoe crab can lay 80 to
100,000 eggs a year.

Sara Grady (04:46):
Yep, yep. They are pretty much a walking box of
eggs, actually. And the eggs area really beautiful, greenish
blue color. They're very tiny,about two millimeters, so about
the size of maybe the end of apencil lead. And yeah, they lay
them in little clusters in thesand.

Jane (05:06):
So the female is moving forward right now, apparently
dragging both of these males. Soshe she's already laid some
eggs?

Sara Grady (05:14):
She may have laid some eggs already. Yeah, yep.

Jane (05:17):
There looks like there's another male coming along for
the chase now.

Sara Grady (05:20):
Yeah, yes. There are usually a lot more males than
females. So if there's a female,she almost always has a male
attached to her, and then therewill be other males that are
coming along for the ride.

Jane (05:35):
I see another male over there. It's like they're all
racing to get to this onefemale.

Sara Grady (05:39):
Yes, yeah. And when we see a pair that is not buried
in the sand, we can pick themup, and I can show you.

Jane (05:50):
There might be a pair over there.
We waited in the shallows towhere we saw two crabs scuttling
towards the edge of the water.Sara picked one up so we could
get a better look at this uniquecreature.

Sara Grady (06:03):
The crab has three parts to its body. So it has
this front rounded part, it'scalled the prosoma. And then
this part here, this sort of, Idon't know, trapezoid shaped
part, is called the opisthosoma,and it has these little spines
on the side. And then this long,pointy part the tail is called

(06:27):
the telson. So they have thesethree body parts.

Jane (06:31):
One of the main questions that we've gotten from kids is,
why are horseshoe crabs calledhorseshoe crabs?

Ivy (06:38):
My name is Ivy. I'm six years old. I live in Gilbert,
Arizona. And why does horseshoecrab start with a horseshoe?

Jack (06:48):
My name is Jack. I'm seven years old, and I live in
Belfort, Pennsylvania. Where dohorseshoe crabs get their name?

Sara Grady (06:55):
Well, if you look at the front shape of the horseshoe
crab, it looks like a horseshoe.It's a U shape, and that's
that's it, yeah.

Jane (07:04):
And the horseshoe part that, that big armored part
really helps protect a lot oftheir organs, right?

Sara Grady (07:10):
Yeah. So they're really well protected both on
the back of their shell, theformal name being a carapace,
for the crab. They're alsoreally well protected
underneath, for the most part.If you look on the underside,
they have all of these differentclaws here, and they're

(07:32):
different on a male inparticular. So we know that this
is a male horseshoe crab becausehis front claws look like boxing
gloves. So those are calledboxer claws, and then the rest
look like scissors. If this wasa female, all of the claws would

(07:52):
look like scissors. They alsohave these special rear claws
that actually are more like skipoles,

Jane (08:03):
Yeah, they have like five little appendages that come out
of it. These are wild looking!

Sara Grady (08:07):
Yeah. So this, you know, just like a hiking pole or
a ski pole, helps the crab pushthemselves forward as they walk

Jane (08:12):
How many claws does one crab need?
across the mud, and then thesetwo tiny claws here are called
chelicerae, and that's how theypush their food into their
mouth. So this is the horseshoecrab's mouth, this spiky hole
here. So they use these claws tokind of push stuff down in there

(08:35):
so that they can eat it.

Sara Grady (08:39):
I know, right? So let's see. Let's count them. So
we've got our two special frontclaws on the male. Then we've
got another 1, 2, 3, on eachside, so we're up to eight. And
then we've got these pusherclaws. So that brings it up to
10, right? 1, 2, 3, 4, 5, 6, 7,8, 9, 10, and these little tiny

(09:01):
ones don't really count. So,yeah, 10 claws. Their most
sensitive part are these flapshere, which are their gills.

Jane (09:11):
So the reason they're called horseshoe crabs is
somewhat self explanatory. Themain carapace looks like a
horseshoe. But why are theycalled crabs? They're not really
crabs, are they?

Sara Grady (09:21):
Right, well, most people, I think, when they see
something that has claws and iswalking around in the ocean,
will think that it is a crab ofsome sort. Most crabs that you
see are going to walk sideways.Horseshoe crabs are walking
forward. They are more closelyrelated to spiders and
scorpions. And in fact, theselittle claws, if you were to

(09:45):
look up close on a spider, youwould also see those on a
spider.

Jane (09:50):
So they're sort of named crabs, not by mistake, but by
humans just making assumptions.

Sara Grady (09:57):
Right, right, just like, you know, there are other
marine creatures that aremisnamed, like starfish and
jellyfish, neither of which arefish, right?

Jane (10:07):
Let me just pause here for a second. Did you know that
horseshoe crabs aren't reallycrabs? I didn't. They're more
closely related to spiders andscorpions, as she said. So we've
been calling them the wrongthing all along. At least we got
the horseshoe part right.

Emilio (10:24):
My name is Emilio. I'm six years old. I live in
Columbus, Ohio. How didhorseshoe crabs live before
dinosaurs, and how are theystill alive today?

Jane (10:36):
How long have horseshoe crabs been alive?

Sara Grady (10:39):
They've been around for about 450 million years.
Yeah. So they're one of theoldest living creatures walking
around here. Yeah.

Jane (10:49):
How did they survive that long? How did they survive when
dinosaurs didn't and I mean,what's the secret of the
horseshoe crab?

Sara Grady (10:55):
There have been a lot of extinctions between the
time that the horseshoe crabevolved and now and they
survived by being tough. And Ithink really finding the right
body shape. Crabs tend to doreally well in general, even the
later crabs in evolution. Soit's a good body to have. They

(11:19):
really don't have a lot ofnatural predators when they're
in the water, and so they canjust keep going.

Jane (11:27):
Does this one need to stay wet?

Sara Grady (11:29):
That's a great question. So part of coming into
spawn is that they often willend up out of the water, and
they have these special gillscalled book gills, and they're
almost like the pages of a book.So there's these flaps on top,
but then within each of thetougher flaps, there's pages

(11:51):
almost and so those book gillswill allow the crab to breathe
as long as those can stay wet,so the they can pull oxygen out
of the air through the waterthat's on their book gills.

Jane (12:08):
So their book gills will stay wet for a little while, at
least, even if they're out.

Sara Grady (12:11):
Yeah, about two days.

Jane (12:13):
Oh, that's a long time.

Sara Grady (12:14):
Yeah. They they're okay for about two days or so.
Of course, when they're on thebeach, they are more vulnerable.
A gull--

Jane (12:21):
Sara, watch out. There's something coming for you, right
behind you. Look out behind you.

Sara Grady (12:25):
Oh, look what we have right here. Yes, another,
another crab. This one looks alittle bigger, so I'm gonna see
maybe it might be a female.Nope, another male.

Jane (12:36):
One of the other things I notice about this one that
you're holding is that there aresome things attached to it,
other shells, other creaturesattach themselves to horseshoe
crabs and get a ride.

Sara Grady (12:48):
Yeah, so they have these slipper shells that are on
the back of the crab. Sometimesthey'll have barnacles. This one
has some algae on it. Andhorseshoe crabs actually have a
flatworm that lives on mostlytheir gills. It's called a
Limulus leech. Limulus is thegenus, scientific name, for

(13:09):
horseshoe crabs, and it onlylives on horseshoe crabs, and
it's actually a flatworm. It'snot a leech.

Luisa (13:15):
My name is Luisa. I'm four years old. I want to know
if horseshoe crabs pinch. I'mfrom Lynn, Pennsylvania.

Jane (13:22):
Do horseshoe crabs pinch?

Sara Grady (13:24):
They don't. Nope. I'll show you right now that you
can put your finger right in theclaw.

Jane (13:31):
I'm gonna do it too.

Sara Grady (13:32):
Yeah, you can pick a claw, any claw, and stick your
finger in there. If you can getit.

Jane (13:38):
It won't even grab me. It's trying to grab the
microphone. It's like, "What areyou doing?"

Sara Grady (13:42):
Yeah, they're, they're, they're very friendly,
actually. You wouldn't think so,but, but yeah, one of my
favorite things to do, actually,is if you kind of put your hand
right in the middle of them,they kind of will give you a hug
with their claws. Oh, I think itjust poked your microphone with
its tail. So one thing I willsay, if you are picking up a

(14:05):
horseshoe crab, is they do liketo fold in half, so don't put
your fingers between the twohalves of the shell, because
that is the one way they canpinch you.
But they're not doing it to bemean.

Jane (14:18):
Should we be picking up horseshoe crabs? Is it okay to
No, they're just folding in halfand you happened to have your
hand in the wrong place.
be picking them up and makingthem give you a hug?

Sara Grady (14:27):
That's a really good question. I think if you're

Jane (14:28):
That's sort of upside down, then.
interested in looking closer ata horseshoe crab, it's a good
idea to pick it up and get toknow it a little bit. Make sure
you put it back in the water.Don't ever pick a horseshoe crab
up by its tail. You want to pickit up by the front, by that
rounded horseshoe part, and youcan hold it just like a bowl of

(14:49):
cereal in your hand. So that'sgonna keep it

Sara Grady (14:53):
Upside down. And they like to, they like to fold
up in half. So you can just holdthe crab like that. And you
don't want to disturb any crabsthat are actively mating.

Gray (15:04):
Hi, I'm Gray. I'm five years old. I live in Wexler,
California. Why do horseshoecrabs have the pointy thing on
the bottom?

Jane (15:17):
Tell us a little bit about this very long tail on the
horseshoe crab.

Sara Grady (15:22):
If you imagine that the crab has ended up on its
back and it's stuck on the sandor maybe in a little bit of
water, it needs to kind of polevault itself back over. So
that's what that tail is for it.It kind of will twist and plant
the end of that in the sand orthe mud and flip itself over.

Jane (15:42):
But it's so long and you're not supposed to pick them
up by it. Do they get ripped offor lost?

Sara Grady (15:47):
They do sometimes, yeah, yeah. Sometimes it will
get caught and stuff, and thenyou'll just see they have a
little stub or something likethat.

Jane (15:54):
We know that horseshoe crabs don't pinch but can they
sting you with that tail?

Sara Grady (15:59):
Nope, nope. They are not gonna sting you. They're not
gonna try to hurt you with thattail. They don't have any sort
of venom or anything like that.

Quinn (16:08):
My name is Quinn. I'm five years old. I'm from Rocket
Center, New York. What dohorseshoe crabs eat?

Jane (16:17):
What do horseshoe crabs eat?

Sara Grady (16:19):
They eat a variety of little creatures that live in
the mud.

Jane (16:24):
So they're carnivores.

Sara Grady (16:25):
They are, yes, yep. They eat little worms. They will
eat small shrimp, like animalscalled amphipods, that live in
the mud. And they also will eatsmall shellfish. And in fact,
that's kind of what gothorseshoe crabs in trouble for a
while with people, becauseeverybody thought that the

(16:50):
horseshoe crabs, especially onCape Cod where we are, were
eating all of their clams, andthey got really upset with the
horseshoe crabs. And you couldactually kill the horseshoe
crabs, and you would take theirtail to the town hall and they
would pay you a nickel.

Jane (17:09):
Wow.

Sara Grady (17:10):
Yeah, yep. So they do eat some little clams and
things like that, but it's not ahuge part of their diet.

Jane (17:17):
So now we know they're not actually eating all the clams
that the humans would like to beeating?

Sara Grady (17:21):
Yes, that's right, yeah.

Jane (17:22):
What eats horseshoe crabs?

Sara Grady (17:24):
Not a lot. But something that's really
important that they do is feedmigratory shorebirds. So when
horseshoe crabs lay their eggs,not all of the eggs end up
buried under the sand wherethey're going to turn into new
horseshoe crabs. Instead, someof them end up closer to the

(17:44):
surface, and there they canprovide lots of food for shore
birds like the red knot, whichis a bird that migrates all the
way from Argentina, from theTierra del Fuego, way way south,
all the way up to the Arctic.

Jane (17:59):
Shall we look at some more horseshoe crabs and put this guy
back and let him get on with theprocess of finding someone to
mate with?

Sara Grady (18:06):
Sure, sounds good.

Jane (18:09):
Coming up
eats them. But do we eathorseshoe crabs? And if not, why
are people catching them?

BREAK (18:19):
BREAK

Jane (18:20):
This is But Why
Lindholm. We're on a field tripto Cape Cod with scientist Sara
Grady, a coastal ecologist whoworks with Mass Audubon. Sara is
teaching us all about horseshoecrabs and answering the many
questions you sent in for us toask her. In the spring, you can
sometimes find thesearthropods--who, remember,

(18:42):
aren't really crabs atall--close to shore. They
usually live a little deeperout, spending most of their
lives on the sea floor, awayfrom human eyes. But in May and
June, they gather in big groupsat the edge of the water to mate
and lay eggs. You can see themall up and down the eastern
coast of the United States, andthe best time to spot them

(19:03):
mating is high tide, whenthere's a full moon or a new
moon. On the day we werevisiting Cape Cod to see them,
there was a citizen scienceproject going on where
volunteers were counting as manycrabs as they could to try to
keep tabs on how these ancientarthropods are doing. As we were
talking, we spotted a wholebunch of horseshoe crabs in the

(19:23):
shallows around our feet. Theyactually seemed pretty curious
about us.
Here's the whole train of themhere.

Sara Grady (19:30):
I just want to show you, we'll put these right back,
but I can pick them all up atonce.

Jane (19:36):
She's so much bigger than the male.

Sara Grady (19:37):
She's very big. Yes.

Jane (19:38):
How big do they get?

Sara Grady (19:41):
Well, the biggest ones are down in Delaware Bay.
They get bigger as you go southtoward that area, and then they
get smaller again as you go downtoward the Gulf of Mexico. They
can be over a foot across, plus.Yeah.

Jane (19:55):
So this one's big, but she's not big by...

Sara Grady (19:57):
Shes pretty big. She's pretty big for horseshoe
crabs in Massachusetts. I'mgonna put these three back. And
as you notice, the tide has comein since we've been talking,
yeah, so that's what they'refollowing, the incoming tide.

Jane (20:14):
So why do they want to lay their eggs up here, sometimes it
looks like not totally out ofthe water, but and sometimes out
of the water here up at hightide?

Sara Grady (20:25):
Well, it's a place where, once those eggs are
buried in the sand, they won'tget washed away as often, right?
So if they were to make theirlittle nest under the water,
every time there was a wave, itwould be kind of messing that
nest up. This way, it's up atthe edge of the water, and the

(20:47):
water will get there, but not asoften. And they also in places,
especially like, again, down inthe mid Atlantic, they really
prefer to lay their eggs aroundthe highest high tides. So those
would be the tides that occurwhen we have a new or full moon,
called a spring tide. And sothat way that nest isn't going

(21:12):
to really have water on it fortwo weeks, which is just about
the amount of time it takes forthe eggs to hatch.

Jane (21:17):
How tiny are the babies when they hatch? What do they
look like?

Sara Grady (21:19):
They are called trilobite larvae, and they look
like a mini horseshoe crab.They're only, again, I mean,
they're just a little bit biggerthan the egg they were in, so
they're only about two or threemillimeters across, and they
look exactly like a tinyhorseshoe crab, except they
don't have a tai. And the reasonthey don't have a tail is it's

(21:43):
usually not a good idea to havesomething sharp and pointy
inside your egg.

Jane (21:49):
True. I hadn't thought about that.

Sara Grady (21:50):
Yeah, yeah. So grow that part once you're, you know,
safe outside the egg.

Jude (21:56):
Hi. My name is Jude, and I'm five years old, and I live
in Vancouver, Canada. Do humanseat horseshoe crabs?

Jane (22:13):
Do humans ever eat horseshoe crabs?

Sara Grady (22:16):
Not really. There's a very small market for eating
the eggs. Very, very small, justlike, you know, if you've ever
ordered sushi with fish eggs onthe outside or something like
that, it's similar to that, butthat's mostly the Asian
horseshoe crabs. It's not likewe're exporting American

(22:38):
horseshoe crab eggs to to Asia.

Jane (22:42):
However, humans do capture horseshoe crabs and kill them
and use them. Why are horseshoecrabs important to humans?

Sara Grady (22:52):
So right now, there are two reasons that horseshoe
crabs are harvested. One of themis for bait, and that's for the
whelk fishery. So a whelk is agiant snail, and

Jane (23:09):
Which people do eat.

Sara Grady (23:10):
Which they do eat, Yes, yep. And there's a market
for that. And so they love thesmell of horseshoe crabs,
especially horseshoe crab eggs,so females will catch more
whelks. And so there's anindustry for collecting
horseshoe crabs for bait.Fortunately, you're no longer

(23:34):
allowed to harvest horseshoecrabs while they are spawning,
which is going to help thepopulation grow. The other
reason that horseshoe crabs areharvested is for their blood. So
horseshoe crab blood has a veryspecial property there. They
have a really sensitive immunesystem, and so anytime any sort

(23:59):
of bacteria gets into ahorseshoe crab, if you can
imagine the horseshoe crabgetting a cut through that big
shell, it's able to immediatelyform a clot around that wound
and seal it up. And peoplediscovered that you could
actually take that blood and getthat particular chemical from

(24:25):
their immune system and use thatto detect whether something had
bacteria in it. So, if you had acompany and your job was making
things like saline that they,you know, you put in an IV or
maybe a vaccine, before you hadto test to see if it had

(24:46):
bacteria in it or wascontaminated by injecting it
into a rabbit and waiting to seeif the rabbit got a fever. Now,
this compound from horseshoecrab blood, a small amount of it
can be used to test whether thatis sterile. So that's been
really helpful, and there's aneffort to find a synthetic

(25:12):
alternative so that horseshoecrabs don't have to be harvested
at all for that purpose.

Jane (25:17):
When you say synthetic, you mean a human made version
that doesn't require killing anyhorseshoe crabs to get it.

Sara Grady (25:23):
Exactly.

Jane (25:24):
To take the horseshoe crab blood, crabs are captured and
some of their blood is drainedout. The crabs are then put back
in the water. But not all ofthem survive that whole
procedure, so researchers aretrying to figure out how to make
sure the crabs are treatedfairly, and, as Sara mentioned,
they're trying to find ways tomake a chemical that does what

(25:44):
the horseshoe blood does, sothey don't need to endanger the
crabs at all.

Hazel (25:49):
My name is Hazel. I'm eight years old. I live in
Gilbert, Arizona. My questionis: what color is horseshoe
crabs blood?

Sara Grady (25:58):
Their blood is blue. Yeah, it's a sort of a sky blue
color, I suppose, a lighterblue, and that is because the
molecule that's used to carryoxygen in horseshoe crab blood
is based on copper. It's calledhemocyanin. And it's kind of

(26:24):
like the hemoglobin that's inour blood. So we have red blood
cells, our blood is red, andthat molecule in our blood has
iron in the middle. So Jane,what color does iron turn when
it's exposed to oxygen?

Jane (26:38):
Rusty red.

Sara Grady (26:39):
Yeah. And what color does copper turn when it gets
too much oxygen?

Jane (26:43):
Kind of a blue, which is confusing, because if you see a
penny, you think it's a coppercolor, which is like an orangy
metallic. But if you've everseen a copper roof, after a long
time, it's kind of a sea blue.

Sara Grady (26:56):
Yeah or the Statue of Liberty.

Jane (26:58):
Oh, yeah, I forgot about that.

Sara Grady (26:59):
Yeah, yep. So that's why their blood is blue.

Jane (27:02):
So are horseshoe crab populations in trouble?

Sara Grady (27:05):
It depends on the place, and a lot of places they
have been over harvested, and alot of people have worked hard
to try to protect them.

Jane (27:15):
So what's the status now?

Sara Grady (27:17):
They are increasing in some places, stable in others
and then there are other placeswhere they have declined. So
it's kind of all over the place.Horseshoe crabs take about 12
years between the time that theyhatch out to the time that they
come back to the beach to laytheir eggs. And so that means

(27:38):
that anything that's done toprotect them when they're laying
their eggs, we're not gonna seeif the protections worked really
well until those crabs grow upand come back.

Sophie (27:50):
My name is Sophie. I'm five years old. I live in
Delmont, Pennsylvania. How longcan horseshoe crabs live?

Jane (27:58):
So 12 years until they are adults, essentially, until
they're mature and can make newhorseshoe crab babies. How long
do they live in total?

Sara Grady (28:08):
It's hard to know, because unlike something like a
fish or like even a clam or atree, you can't cut it and count
rings or count layers on variousbones. They don't have bones
like that. So we have to kind ofgo by size, and also, to some

(28:31):
degree, by the things that aregrowing on the shell can also be
used to kind of get somewhat ofan age.

Jane (28:37):
You mean, like, you'd be like, "Look, dude, you have that
barnacle. That barnacle is atleast seven years old, which
means you must be even older."

Sara Grady (28:43):
That's right. "You've had that jewelry for a
long time."

Jane (28:46):
But I thought horseshoe crabs molted and got rid of
their shells.

Sara Grady (28:50):
The molting slows down once they become mature, so
they can live up to about 25, 30years, we think, yeah.

Jane (29:01):
And how often do they molt in a lifetime?

Sara Grady (29:06):
Oh, it's about 15 times.

Jane (29:10):
So they get a new shell 15 or 16 times. But most of that is
when they're really young.

Sara Grady (29:14):
Yeah, they molt six times in their first year, yep.
And they grow from being, youknow, about the size of a kind
of a dull pencil lead, all theway up to being bigger than a
quarter.

Jane (29:28):
Wow, in one year. That's a lot. I mean, it still sounds
pretty small, but if you're acrab, that's a lot of growth.

Sara Grady (29:33):
Yeah, yeah, yep.

Jane (29:35):
There's like, a ton of them over there.

Sara Grady (29:37):
All right, let's keep moving. Oh, here's a pair
that's actually buried in.

Jane (29:43):
Oh, yeah, wow.

Sara Grady (29:45):
So she came in, she's dug this nest, she's
laying the eggs, and thenthey'll probably leave in about
an hour.

Jane (29:54):
So they're out here on the very edge, where we can see them
right now, and there are so manyof them. So cool, because I
never see horseshoe crabs, andI'm amazed. But where are they
normally?

Sara Grady (30:06):
Well, when it's not time for spawning, they stay in
the deeper water, and they'rejust out there eating. Because
they're cold blooded, they doslow down in the wintertime, so
they'll kind of dig into the mudand stay there, and that's
actually when they get a lot ofthe barnacles and things on
them, because they pretty muchturn into a rock for a while.

Jane (30:30):
We figured we'd better let the crabs get on with their
mating and spawning. But I hadto get Sara to do one more thing
while I had a microphone in herface. Sara has written a whole
song about horseshoe crabs. It'sa specific type of song called a
sea shanty, and I sprung it onher as a surprise that I knew
about the song, and wanted tosee if she remembered enough to

(30:51):
still be able to sing a verse.

Sara Grady (30:52):
[SINGING] A little bird called the red knot can fly
so far, yes, quite a lot. FromSouth America to the Arctic on
their migration. While they fly,they stop to rest. They think
that horseshoe crab eggs arebest. For getting fat and
bulking up and reachingsatiation. Feeding this little

(31:15):
bird is quite important, I'msure you've heard. How these two
animals are strongly linkedtogether. Their blood is blue.
That's because of copper. Itclots up as an infection
stopper...it...[laughs]

Jane (31:31):
I was liking that verse,

Sara Grady (31:32):
oh yeah, I can't remember.

Jane (31:38):
That was great. Yay yay yay. Clap.
I've had that song in my headever since we got Sara to sing
it. Thanks to Dr. Sara Grady,senior coastal ecologist with
Mass Audubon, for sharing herdeep knowledge of horseshoe
crabs with us. We're going toput some videos on our YouTube
channel and social mediachannels if you want to see what
these crabs look like. If you'relucky enough to see a horseshoe

(32:02):
crab, observe them verycarefully. They are wild
animals, and they deserve to betreated with respect. They're
not afraid of people, and theymay come right up to you.
Remember, they don't pinch andthat tail doesn't have any venom
or any way to sting you. If youwant to pick one up, though, be
very careful. Hold it like abowl of cereal, and don't put
your fingers in between the twosegments of the body, because

(32:25):
when they fold, you can get yourfingers stuck where their body
parts hinge. And don't keep themout of the water for too long.
Put them back in when you'redone observing, and make sure
they're not on their backs. Andif you live near the coast,
there may be a survey happeningnear you. Have your adults help
you check with your state andlocal wildlife organizations to
see if you can get involved inhorseshoe crab conservation

(32:47):
efforts.
That's it for this episode. Ifyou have a question about
anything, have an adult recordyou asking it. It's easy to do
on a smartphone using an applike voice memos. If you are too
shy to talk or can't use yourvoice, you can always have an
adult email us a writtenquestion, and we can use that
too. Be sure to tell us yourfirst name, where you live and

(33:08):
how old you are. Then have youradult email the file to
[e-mail]. But Whyis produced by Melody Bodette,
Sarah Baik, and me, JaneLindholm, at Vermont Public and
distributed by PRX. Our videoproducer is Joey Palumbo. Check
out our YouTube series, But WhyBites. We put out a short,
bite-sized video episode everyother Friday, and we're about to

(33:31):
put one out about horseshoecrabs. Our theme music is by
Luke Reynolds. If you like ButWhy, please like and comment
wherever you listen and sharewith your friends. It really
helps other people discover us.And if you really like But Why,
you can get a But Why T-shirt, aBut Why water bottle and other
cool swag at our website,butwhykids.org. We'll be back in

(33:54):
two weeks with an all newepisode. Until then, stay
curious.