Sex In The Wild - the biology of mating - PBS

'Mating.

For every species on Earth, it's vital for the survival of the fittest.'

- Look! Whale! - There she blows.

'But the way some creatures make babies is quite extraordinary.

In the oceans, air-breathing mammals like dolphins and whales,

have evolved to reproduce under water.

They must have sex holding their breath.'

- You see the penis exposed? - Yeah! I didn't think I'd be able to see that.

'Newborns must rush to the surface for air the moment they are born.

And young have nowhere to hide from the biggest predators in the world.

The underwater world is a challenging place for sex in the wild.'

There are whales everywhere.

It's like whale soup here.

There we go. There's a baby.

'I'm Mark Evans.

As a veterinary scientist, I'm curious to uncover the secrets

of marine mammal mating strategies.

In Mexico, I'm finding out

why gray whales travel half way around the globe to give birth.'

One right there. Two o'clock.

'While anatomist Joy Reidenberg travels to New Zealand

to discover how dolphins perform sub-marine sex.'

I've spent my entire research career specializing in marine mammals.

I've always been fascinated

by the story of how their four-legged ancestors

walked into the sea 50 million years ago...

...and what impact this has had on how they reproduce.

And there are few better places to see marine mammals

than off the islands of New Zealand.

The species I've come to see gathers in huge numbers here.'

Right over there. See that rough patch, with white spots?

Those white spots are where the dolphins are jumping right now.

Oh, look at that! Wow! Beautiful!

'These are dusky dolphins.

Only from the air can you appreciate

the tremendous size of these mega-pods.

Down there are mothers, calves, juveniles, and mating pairs.

This is one of the few places in the world

where you can see the whole life cycle play out.

Dolphin reproduction is notoriously hard to study.

But the daily routine of dusky dolphins makes them easier to observe.

Unlike most dolphins, they eat at night and have sex during the day.

They are renowned for their sexual activity.

Females here will often mate with several males in quick succession.

But even in daylight it's hard to see what's going on.

The first challenge is to distinguish males from females.'

This is what a dolphin's body looks like.

It's very long, kind of like a long, skinny tube.

When you look at its body, there's something really weird about it.

It's really hard to tell what sex it is.

That's not true in most mammals.

You can immediately tell who's a boy and who's a girl.

In females, you would see breasts.

In humans, you see breasts.

In cows, you see an udder.

Where are the breasts on a dolphin?

They're actually located right about here.

But that doesn't show up

because they're recessed inside the body.

You expect to see a penis,

and you expect to see a scrotum with testes in it.

So the penis in a dolphin is actually internal.

It does this interesting little loop-de-loop, just like that,

and it only extrudes the penis when it's ready to mate.

And look at the size of this testis.

It's as big as the dolphin's flipper is.

That's an enormous testis to have.

'The reason they have testicles the size of rugby balls

is because they need to produce lots of sperm

to fulfill their extreme mating habits.

And with such large reproductive anatomy,

it's easy to see why they stow it all on the inside.

That way, they keep a streamlined body shape,

enabling them to glide through the water at great speed.

This means that if you want to investigate how dolphins have sex...

you need to have a fast boat.'

- Hi, Dara. - Good to see you.

- Good to see you, too. - Here you go.

- Ready to find some dolphins? - I'm very excited about it.

'Dara Orbach is a friend and colleague

who's been studying Kaikoura's dusky dolphins for three years.

She's trying to understand their complex mating rituals.'

Right there. Two o'clock.

Yeah.

'Dara has a team of researchers to help capture their brief encounters.'

Female on top, swimming. Photo frame, Theresa, female.

'Dara does the filming.'

We have a side slap from one individual...

Theresa, what's your start frame?

4424.

'Theresa takes hi-resolution photos of dorsal fins...'

Kelsey, 300 meters.

'..And Kelsey keeps the boat in the middle of the action.

At night, they put their photos through specialized recognition software

that can match the fins, like fingerprints, with any photo taken previously.'

'Dusky dolphins are the ocean's master acrobats.

Their repertoire is spectacular.

They somersault...

...side splash...

...and leap for joy.'

Tail slap from female to break away.

'But I still haven't seen mating.'

100 meters. Yep.

It looks like a pretty big group of dolphins.

'Luckily, there is a particular behavior

that helps Dara find mating dolphins.

It's a kind of aquatic dating dance

that Dara calls a “re-entry leap“.'

What's a re-entry leap compared to..

Other things looked like flips.

A re-entry leap is where they jump up and come straight down

and dive to depth.

The mating ones seem to be the only ones

that consistently do these re-entry leaps.

I think both the males and the females are leaping.

It's often one to three individuals who jump at the same time

regardless of the group size.

It's usually the female in the lead

with the males in hot pursuit behind her.

'Dara's team moves towards the leaping group to capture them mating.'

So when you see those white bellies,

that's the male, usually, upside down, often with the penis everted.

- Oh, yeah, I see it. - Still in belly-to-belly contact.

- Still in belly-to-belly contact. - And now they broke.

That was fast. (Laughs)

2.6 seconds... is the recorded average.

Do you see the inverted male over there with the female?

He's pushing the female against the surface of the water

and using the water almost like a wall to force her against it.

- Oh, wow. - When she was at the surface,

I saw her dorsal fin wiggling side to side.

Yeah.

She's trying to get away from all these ardent males.

She'll do tail slaps. Sometimes she rolls onto her back.

An actual copulation is very, very fast,

so if she doesn't line up her body and relax,

it will be difficult for the male to successfully intromiss.

We're going belly to belly. Female turning onto her right-hand side.

'By pushing the female against the water's surface,

the males make it harder for her escape.

While holding his breath,

the male must press his body against hers to have sex,

which is not so easy without arms and legs.

Groups of males will repeatedly have sex with the same female

within minutes of each other.

In order to try and win the race to her egg,

males have evolved large testicles to produce lots of sperm.'

When you see them come up, there's often two or three of them together.

They're all males and one female?

Or are there several males in that group?

We've seen a variety of different behaviors.

Usually, it's one male with one female - we presume it's a female.

That being said, sometimes we do see homosexual mating.

- Really. - So we'll see...

an individual in a female position,

and we'll see another male underneath with his penis exposed.

They'll switch positions and we'll see a penis

on the one in the female position.

When you see homosexual mating behavior,

is it a dominance display or are they just having fun?

We don't see homosexual mating behavior that often,

and we're trying to tell if it's the same males that are swimming together

or if, when they switch, it will be a different male that comes into the group.

I think we've only seen homosexual mating behavior

on three or four occasions so far.

So it's a bit tricky to know with certainty.

'When dolphin females enter a mating chase,

they may be testing the sprinting prowess of the males

to make sure they only mate with the best.

But such gymnastics are not possible

for their enormous cousins, the whales...

as Mark has been finding out.'

'The West coast of Mexico is home to dozens of whale species.

But there's a special haven on the Baja Peninsula

whose warm shallow waters provide protection from predators.

This is the San Ignacio Lagoon,

where gray whales come each year to have their babies.

Dr. Jorge Urban has been studying whales for over 30 years.'

'He's particularly interested in gray whales

because of their resilience.

They're one of the few baleen whale populations

that have produced enough babies

to recover from over a century of intensive whaling.'

- Ahh! - Look at that.

'When a gray whale breaches,

it's not a mating dance, like dusky dolphins.'

It's some spectacle when they breach like that.

'Jorge has two theories for why these whales jump.

It may be a method of communicating with other whales in the area.

Or just a way of scratching their barnacle-covered bodies without arms or legs.'

Out of your two theories, the acoustic one is fascinating.

The one about getting rid of barnacles...

It's fascinating, but when you look at the outcome,

that so many of the adults are so covered in barnacles,

- it kind of suggests it doesn't work very well. - Yes.

'As far as Jorge knows, breaching has little to do with mating,

but he's trying to unravel the gray whale's

remarkable reproductive strategy.'

How many whales do you think will be in the lagoon at the moment, roughly?

51?