- [host Joe Hanson] Every year east coast beaches play host
to one of the world's wildest parties.
It's all sex and gluttony on the shore.
But these spring breakers are of the 10 legged variety.
Millions of prehistoric creatures converge here.
What's behind this epic fiesta?
[upbeat music]
The waters of Delaware Bay look unassuming.
But as the temperatures warm in spring,
something curious happens.
Strange creatures emerge from the depths.
These ancient beings are horseshoe crabs.
Horseshoe crabs spend most of their lives in the deep ocean
but every May and June, millions of
these creatures drag themselves ashore
on sandy beaches up and down the Atlantic coast.
Some will travel 60 miles or more just to get here.
While aerial views of these creatures are pretty cool.
We wanna take you even closer.
So we teamed up with our friends
at DEEP LOOK to show you this.
They might look like crabs.
They're actually more closely related to spiders
and other arachnids, than to crabs or lobsters.
Nowhere is the concentration of horseshoe crabs greater
than here in Delaware Bay.
As many as 30 million crabs, a population greater than
the size of Shanghai, China descend on the bay.
But what are they doing here?
These beaches are the ultimate horseshoe crab hookups spot.
Male crabs arrived just ahead of the females.
They form a wall that females must plow through
to reach suitable nesting sites.
They jostled until one lucky male successfully grabs
onto the females shell and pulls himself a board.
Each female will carry upwards of 80,000 eggs.
She buries them in the sand, which her suitors fertilize.
- [Dave] The females burrow into the sand.
So she is almost completely covered up when she's making
those nests, and the males are on the surface
of the sand and surrounding it.
They like to spawn high on the beach.
The theory is that that was a strategy
to avoid aquatic predators.
- [Joe] To do that the crabs need
to arrive when the tides are highest,
around the new and full moon in May and June.
Only a handful of the thousands of eggs
a female lays will even survive a year.
Fewer yet will survive to sexual maturity.
- [Dave] You just have to buy a lot
of lottery tickets have a chance of winning.
- [Joe] It's a strategy that served
them well for a long, long time.
They're older than dinosaurs.
- [Dave] If you saw a fossil of a horseshoe crab
from hundreds of millions years ago,
you would recognize it as a modern day horseshoe crab.
So it's a living fossil.
- [Joe] There was a time however
when their survival was in question.
In the early 1900s, horseshoe crabs were harvested by
the millions and used as fertilizer.
That practice ended but today they're harvested for bait
and for a different use.
Their blue blood contains an ingredient critical to testing
the safety of vaccines and other drugs.
To prevent over-harvesting, a yearly survey
is conducted around Delaware Bay.
Researchers and citizen scientists team up to walk
the beaches and count the crabs.
- The horseshoe crab surveys are the way for us
to learn more about the population.
Four males, several females.
It will be a recorder that will be the person in charge
of taking notes and collecting the data.
There will be a person rolling the quadrant,
which is the metric in which randomized,
which areas of the beach we collect counts.
1, 2, 3, 4, 5, 6.
- Every time I see these crabs, I just go,
this is so freaking Cool.
Horseshoe crabs need big stretches of sandy beach area.
It's an environment that's slowly disappearing around here
with all of the development so it is a big concern.
- [Joe] For now the population in Delaware Bay appears
to be healthy and growing.
That's a good thing, not only for the crabs,
but for the other spring breakers.
Up to a million migratory birds visit these shores
on their way to Arctic nesting grounds.
It's not just coincidence the crabs
and the birds are here together.
For the crabs it's mating time, but for the birds
it's the product of this mating that they're here for,
eggs.
These tiny green gems are horseshoe crab eggs.
They litter the beaches during mating season.
The eggs are an essential all
you can eat buffet for migratory birds.
Some of these birds traveled thousands of miles to get here
and their survival literally depends on this food.
- [Henrietta] Shore bird migration is timed such
that birds arrive in the Delaware Bay during
the peak of horseshoe crab spawning.
- [Joe] The threatened Red Knot is one such traveler.
It flies from the Southern tip of South America
all the way to the Arctic, a journey of nearly 9,000 miles.
- When they arrive in the stopover locations on
the Delaware Bay, they'll be very skinny
and you can almost visibly see their breastbone.
- [Joe] These nutritious eggs are the fuel needed
to complete their migration.
- [Henrietta] By the time they leave,
they've blown up like a balloon
that you could pop with a pin.
When we think of migration, we think of
these really incredible international events
that wouldn't be happening right here
in little old Delaware.
[gentle music]
- [Joe] But like any good party
the morning after it can be a real drag.
- [Man] They have the ability surprisingly to be stranded
after tide has retreated, hunkered down,
stay moist, wait for the next tide.
- [Man 2] The sun really takes a toll.
So sometimes you think they're dead until
you'd give them a little push.
And then when they start moving, it's like,
oh, good, I can save this one.
It's almost addictive.
You say, I'm just gonna flip over 10 more
and then say, well, I can do another 10.
I really do take great pleasure in saving a big mama,
knowing that she will be able to lay eggs again.
Because when you see how the birds rely on them, you know,
it's all part of the circle of life.
- [Joe] To get a more close-up view
of these amazing little creatures,
be sure to check out the latest episode from
our friends at DEEP LOOK.
♪