A pair of wandering Albatrosses prepare
to breed for the first time.
For the next forty years or more they will remain faithful,
shackled to each other.
And this is the reason why.
A monster baby is about to enter the world.
A single chick that will demand
the undivided attention of both parents
for the next nine months.
Every three days each parent embarks
on a one thousand mile round trip across
the Antarctic Ocean to search for food.
Each growing chick is a life sentence of toil
it needs warmth
and a constant supply of nourishment
in the form of regurgitated squid
from the aduit's stomach.
The effort to raise a single chick successfully
is so immense that the Albatross can only breed
every other year.
A succession of greedy chicks will force these parents
into lifelong monogamy.
But both adults would rather be independent
than remain slaves to their offspring.
lf they could opt out of their duties
or shift the burden onto the opposite sex-
they would.
Here lies the parental dilemma.
Off the coast of Newfoundland,
tens of thousands of Capelin shoal in readiness to breed.
These fish are typical of many animals in the sea
they have no plans to care for their young.
Each year they simply head for shallow water to spawn-
a frenzied and risky affair.
As the waves break,
Capelin in their thousands fall out of
the surf and cast their eggs and sperm onto the beach.
By leaving their eggs on the shore
the Capelin have given their offspring
some protection from predators.
But if the eggs survive to hatch the babies are alone
abandoned to face the rigours of the ocean.
Only one in ten thousand fry will survive.
The open sea is vast
and an almost impossible place to care for young.
Most parents don't even try.
Where the surroundings are more secure, like coral reefs
a female spiny lobster, lumbered with eggs,
makes some parental effort.
Hidden in a rocky crevice
she is safe to hold onto her eggs until they hatch
and release them as slightly more self sufficient juveniles,
to join the rest of the plankton in the sea.
The open ocean is a living soup of abandoned youngsters
- all taking their chance.
Some females breeding on coral reefs have
become a little more cunning.
ln Blue Cromis, females take a calculated gamble
and leave their eggs with the black finned males.
Each female quickly lays her eggs and as the male fertilises them, she leaves.
These future fathers must now abandon sex
and play guardian- for a very good reason.
Gangs of pseudo catfish hoover up eggs and offspring alike.
Being a protective father is the only way to ensure
the survival of his offspring.
Here too in the shallow waters of Lake Malawi,
predators have forced fish into parenting.
These young Cichlids have not been abandoned-
they are under the watchful eye, of this time, their mother.
When danger threatens
she performs the most bizarre parental behaviour of any fish
The female is a mouth brooder and guards her group of fry
by allowing them back in and out of her mouth
The blue male meanwhile is free to solicit for more females.
The female is literally left holding the babies
but since the fry are mobile and can feed themselves,
she can now cope as a single parent.
Among beds of eel grass, food is much harder to find.
For Seahorses, if the male didn't help,
the youngsters would stand no chance of survival.
The male, on the right with the swollen pouch,
takes his courtship and parenting duties extremely seriously.
The female is about to pass several thousand eggs into his pouch
in an intricate courtship manoeuvre.
The male fertilises the eggs inside his brood pouch
and for the next month nourishes them with a fluid secreted
form the pouch lining.
Meanwhile the female is free to feed,
build up her reserves and produce more eggs.
ln every sense the mother
the male's labour contractions force the tiny replicas into the water.
The nature of seahorse sex means that this male can be certain
that he has fathered these young.
Such a guarantee of paternity
is a good way for females to entice males into parenting.
These heavy weight amphibians are African bullfrogs
and they breed explosively
when the heavy summer rains create temporary pools.
Each male competes for a succession of females and fertilises their eggs.
He will accumulate several batches of spawn amounting to thousands of eggs
When the exhausted females leave,
it's a powerful incentive for him to stay.
There's another good reason too
Tadpoles need help to survive
the tropical sun and its shrinking effect
on their shallow pools.
The father takes action and shepherds his shoal
like a sheepdog herding a flock.
lf the water gets too hot, he herds his tadpoles into cooler,
deeper water with a better supply of oxygen.
The hefty male also assumes the role of guard dog.
The tadpoles are once again heading for disaster.
Their nursery pools are temporany
and prone to dry up in the heat of the withering sun.
This devoted parent is not about to give up yet.
Although a land dweller himself
he senses the need to keep his offspring aquatic.
Using his strong back legs and pointed snout,
the male digs a channel to a neighbouring puddle to save his family
This excavation work will flood his own nursery
or act as an escape route.
ln such circumstances a dutiful fater is key to survival.
ln more predictable environments
like the humid rain forests of Central America,
caring fathers are rare.
The tiny female poison arrow frog carries tadpoles on her back
to a pocket of water.
She produces only a few offspring
and while the male is free to court again,
she carries each of them to a water filled axil of a leaf.
Each tadpole slips into a personal aquarium.
But such pools contain little food.
The female however has a plan to
overcome this and will not let her young starve.
The duty she is about to perform has made her better suited
to parenthood than the male.
Twice a week she
finds her young in the forest and delivers food in the form of
an unfertilised egg that they can eat.
Forests probably provoke
the biggest parental disputes anywhere because there is plenty of food
and this allows single parents like this frog to survive.
Woodland birds provide a constant insight into the battle over family obligations.
Females invest a minimum of effort in producing such helpless chick.
These babies need lots of food, so males are forced to help.
Throughout the season such teamwork pays off
and a pair may produce several broods.
Ninety five percent of birds opt for such a monogamous set up
but both sexes could cheat and some do.
Springtime in a lush oak forest and a male pied flycatcher sings for sex.
His song attracts a female and he shows her their future
family home.
Natural nest holes are hard to find,
so males all over Europe now commonly chose boxes.
Suitably impressed, the female moves in.
Once mated, she starts to lay their eggs.
But even before she has completed the clutch and started to incubate
her partner has slipped away
to pursue other interests.
The forest is full of more nest sites
and he plans to woo a mistress into one of them
Another female is charmed by his call
and tempted into his second box to breed.
But as soon as she lays eggs
he races across the forest back to his wife.
His chicks have now hatched and he plays the model father
The male started this family early in the season and guarded the female
against other would be mates.
With luck he will have fathered all of these chicks
so it is worth his while to help this female bring up the babies.
Back at the mistresses nest life is not so easy.
She has been cheated.
The male has not returned.
She is now a single mother.
Keeping her tiny chicks warm
and finding enough food is an almost impossible task
Meanwhile the first nest is thriving.
But the second family are now suffering
The male's deception has taken it's toll and the young are beginning to perish.
There are now just three chicks left alive in the nest.
Only the strongest will survive.
As one family struggles the other flourishes.
Five healthy fledglings are being tempted out of the nest,
into the forest, by their parents.
The sneaky male's activities as a bigamist have not compromised
the success of this family at all.
The mistress's struggle is almost over.
This time the cheating male seems to have benefited hands down,
with the bonus of two extra chicks.
But the males don't always get away with it.
ln Austria, female Penduline tits are aware
of male philanders and play a remarkable trick.
The male builds an impressive nest.
He is eager to breed as early in the season as possible.
He too has no plans loyally to stay at home once his nest has eggs.
An interested female has arrived on the scene
and the male advertises his nest.
This female is ready to mate.
The male shows her the nest one last time
and the newly wed hops inside.
lnside the nest the female plays her trick.
Each day as she lays an egg she hides it,
burying it in the fluffy nest lining.
The male is fooled into thinking that his partner is not yet laying eggs.
For three days the female deception continues,
as she continues to bury more eggs.
Finally she abandons the nest leaving her small clutch of
three eggs uncovered for the male to find.
Shocked by his discovery and with no time to find another female,
the male is forced to incubate and rear the chicks alone.
When food is abundant both sexes try to side-step parenting.
But in tough environments like the Australian bush,
the sexes must reach a compromise.
For emus, the female is in charge,
often even initiating courtship to call in suitors.
She has taken months to generate eggs
and now needs an incubator- a male to sit on them.
As she chooses a mate,
each male is weighed to judge if he is fat enough for the task ahead.
Only a heavy-weight male will be able to sit
on the nest all winter and survive without food.
The male is in no position to argue
or cheat the female exhausts her body Reserves as she lays such massive eggs.
She has no energy left to be a parent.
The well-provisioned male accepts the inevitable
and responds to the task ahead.
This is the only way he can be sure that his offspring survive.
But one group of animals excels in such harsh conditions
because they have radically changed the way they look after babies.
The mammals produce milk.
However, it is the female who sports the milk bar
so she becomes well and truly lumbered with the babies.
The male is uncoupled from parenting and free to mate with other females
but sometimes it's in his interest to stay around.
ln the arid veldt of South Africa
Aardwolf cubs need their father.
During the day they are safe underground with their mother.
As the sun begins to set the male stirs
from his resting place away from the den.
Soon he will be needed.
Night falls and the female has to leave her cubs
to search for food.
She feeds on tiny termites and needs a nightly ration
of a quarter of a million to satisfy her appetite.
This will take some hours.
During this time the cubs are vulnerable,
so the father returns to the den to babysit.
As the cubs grow confident and explore outside the den,
their rough and tumble play attracts the attention of predators.
At this stage the male's presence
makes a vast difference to their survival.
A single mother without the benefit of a male baby-sitter
will lose almost all of he cubs to such dangers.
But the father's apparent devotion to the cubs is pure selfishness.
ln fact,
his care improves his breeding success five-fold.
lf he didn't baby-sit he would have to sire
the litters of six single females to achieve the same success.
An impossible task.
His duties are about to finish.
The female has arrived back
and he eagerly disappears back into the night.
The male's decision to forego
a philandering lifestyle is a success.
lt results in a greater number of babies.
ln wild dog packs the effect of male care has a spectacular
effect on cub survival.
Males can bring food back to feed both the young
and the nursing mothers
The greater the male support the bigger the pack's expansion.
Here such help has provided the means for two females to produce
an astounding twenty seven cubs between them.
By co-operating as a group,
large nutritious prey can be captured far away from the den
and fresh meat transported to the cubs.
The communal stomachs arrive back and the excited cubs pester
the adults to regurgitate the pre-digested food.
Growing cubs need more than milk to survive
but are too small to travel to a kill.
By staying to feed their families males have fostered a communal way
of living that is highly successful.
This silverback mountain gorilla is anything but a doting father.
But he too has opted for a communal lifestyle.
His sole parental duty is that of supreme minder to his harem
of females and the offspring he has sired.
The rich territory that he guards provides food
for the whole family.
And he has what every male wants.
Although females provide all the parental care,
they don't have a bad life.
The silverback's polygamy is a compromise between the sexes.
The females are happy to share a strong male,
while the male can breed with several wives.
But within families tensions build up and occasionally erupt.
The silverback is putting one of his sons in his place
Sex is a powerful force and living communally
can unleash disruptive energy.
A new battle has begun among social groups
The battle to keep the peace.