“Mum, who do you love best?” – Parental favouritism in the animal kingdom

Whilst this is a question we tend to think of as being asked by a child with siblings, it turns out, animal parents have favourites too…

For example, there’s a species of budgie that regurgitates food for its young and males will feed in response to chicks begging whereas females will seek out the smallest offspring and prioritise them.  In bearded vultures, it really does pay to be the favourite; it’s common for parents to only feed the first born chick…  But it’s not just size and birth order that parents prioritise.  Sticking with the bird world, let’s have a look at a few more examples.

Eastern bluebird dads favour their sons, protecting them from danger whilst exposing their daughters.  But sons aren’t equal either, the baby which is brightest in colour will garner dads protection more so than his duller brother.  Mums on the other hand didn’t discriminate.  If we turn to coots, we find much the same, with parents preferentially feeding nestlings which have ornamental plumes over their duller nestmates.  But it isn’t always about how attractive the offspring are:

“In birds, female blue tits, for instance, are better parents to the offspring they had with sexy males.  Not only that, but if the male they have mated with has his colouring dulled, the equivalent of being made less attractive, the female will actively reduce her efforts to feed their offspring.”
– Verdolin

So, what’s going on with parents?  Why do they play favourites with their children?

Well, what resources are available is an essential part of understanding this.  If you have five chicks and food is scarce, you could split it all equally and end up with five slightly less healthy chicks, or you could allocate them in an unequal way and thus play favourites with your children.

With chinstrap penguins who have more than one chick, they will make their kids chase them for food.  The chick that wins the race gets the food and the one that lags behind will ultimately die.  It sounds incredibly harsh but if you only have enough food for one chick, you need to make sure it goes to the one who has the highest chance of surviving to adulthood and having their own chicks.  This explains why parents tend to favour the fastest and strongest of their young, but what about those eastern bluebird dads and the female blue tits?

This type of favouritism, based on appearances, is again about trying to ensure that your lineage will continue.  With the blue tits, sexy males mean sexy children who in turn will have more sex and hence more chicks themselves.  By putting more resources into caring for the chicks from the sexy male, the mummy blue tit is worker harder to ensure her young will become healthy, sexy and successful breeders themselves.  For bluebirds, the females prefer to mate with brighter males and thus in the example above, where dad is trying to protect his brightest son, he is attempting to protect the son who has the best chance of mating when he grows up.

You might be wondering though, why are daddy bluebirds so concerned with their sons and not their daughters.  It’s not just that bluebirds want to have daddy son time, it happens in other species as well.  For example, wandering albatrosses feed their sons more than their daughters and I’m sure there are many more examples out there of dads putting their effort into ensuring their sons grow up to be big, strong, sexy adults.  Essentially it comes down to wanting to continue the family line and sexy males (in species where an individual male has more sex than an individual female) will achieve that.

But it’s not even just after birth that parents play favourites, in some species there can be a disproportionate ratio of males and females born, taking the idea of parental preference to an extreme.  One example of this is the red deer which has more sons if mum is in good condition and more daughters is she is afflicted by parasites, ill health, in a lower rank etc.  This means that more dominant females have more sons than their non dominant counterparts, something that we see with macaques as well.

The Trivers-Willard hypothesis suggests an explanation for this favouritism.  The hypothesis is that with conditions are great, females should give birth to and invest in raising sons over daughters.  When conditions are poorer, the reverse should occur.  As with the other types of favouritism we’ve looked at, this is about ensuring that your children have lots of children and your line continues.  To understand why the Trivers-Willard hypothesis might hold, we need to note a few things:

  • If a mother is in great condition, she is more likely to have a child who is in great condition.
  • If a child is in great condition, they have a better chance of surviving to adulthood.
  • If the species is such that males have the potential to produce more offspring than females, then being sexy is important. If you aren’t a sexy male, then you might not attract any females, thus you won’t have any children and essentially the resources that your mother chose to give you are wasted.  Basically, mum would have been better having a daughter.

Essentially, a male in great condition will have significantly more offspring than a female in the same condition and thus is a better investment.  A male in poorer condition will potentially have less offspring than a female in the same condition and so is a bad choice to invest in.

Whilst it may not be of comfort to you if you aren’t the favourite child, at least you know you’re not alone… And just in case you were wondering, its thought that two thirds to three quarters of human parents favour one child over another…

Suggested reading:

Let’s do it like they do on the Discovery Channel…

Whilst my last post focused on sex primarily in a reproductive context, animals have sex for many reasons, just like humans do.  However, “for decades, biologists, anthropologists and psychologists have suppressed inconvenient evidence of homosexual behaviour among the human and nonhuman animals they observed” (Julien Dugnoille).

I’m going to start by looking at same sex activity as it’s one clear thread of evidence that not all animal sex is for reproduction.

There are many more bisexual animals than we tend to think and note I’m saying bisexual because often the animals aren’t solely engaging in same sex activity (which I’m going to say because same sex sex is a mouthful!).  Often, they are also having sex with the opposite sex when the opportunities arise.  The BBC also discusses whether we can claim some animals are homosexual as opposed to bisexual.

Ultimately, these are human enforced labels and as Eric Anderson says:

“Animals don’t do sexual identity.  They just do sex.”

You’ve quite possibly heard about the ‘gay’ penguins in a zoo.  They coupled up and started building their nest and sitting on rocks.  When the zoo realised what was going on, they placed an egg from a female penguin who was struggling to care for it in the nest.  The male penguins successfully incubated and raised the chick.

Same sex dolphins can become partners for life engaging in sexual behaviour, for example males can have a temporary female relationship but will return to the initial male partner afterwards.  Further, two male couples can join up to become a foursome.  One theory is that it helps to have a companion when feeding and resting because they can look out for danger.

Some male greylag geese pair up and when it’s time to raise children, they find a female and raise them together as a trio.  Some don’t but research shows the advantage of a trio; there is better defence against predators, the female has a higher social rank and better chance of survival and the female has more time to devote to her chicks because two males are helping.  After the chicks are raised, the males stay together whilst the female leaves.

In a reverse make up, roughly 2% of oystercatcher breeding groups are made up of two females and one male.  Additionally, up to a quarter of black swan families include parents of the same sex (Scientific American) and in some bird species, males steal eggs from females and raise them in same-sex unions.

Whilst these examples might feel like the exception to the rule, observers have witnessed as many as 1500 species of wild and captive animals engaging in same sex activity.

“Homosexual behaviours is surprisingly common in their animal kingdom.  It may be adaptive- helping animals to get along, maintain fecundity and protect their young.”
– Emily Driscoll, ScientificAmerican.com

Moving on from same sex activity to other non reproductive sexual activity, we find types of fruit bats who engage in oral sex, both female on male and male on female.  There is also masturbation and attempts to mate with the dead…

But what is all this sexual activity about?  Obviously, some sex is about reproduction, but pleasure, bonding and keeping the peace are all reasons for engaging in sex.

Bonding can be important for group species and strong bonds can be very helpful when facing off rivals or seeking protection from other group members.  This bond is also important in maintaining a strong group dynamic and sexual activities can diffuse social tensions.  Another type of bond is that of a parenting couple who may engage in sexual activity to maintain their bond whilst raising their young.

It’s interesting to look at an example, the bonobo.  Bonobos use sex to greet each other, to resolve conflict and for pleasure.  They engage in mutual masturbation, oral sex and penis fencing and are in general a very peaceful species.  Perhaps humans would be more chilled out if we had more sex?

But lets take a second to focus back on masturbation.  As well as humans, many other primates engage in masturbation and this can range from simple stimulation with their hands through to using twigs and leaves and other inanimate objects.  Females have been observed inserting objects into their vaginas and one male orangutan created his own sex toy:

“In one display of sexual ingenuity, a male orangutan created his own ‘sex toy’ using a large leaf, through which he poked a hole with his finger.  He then proceeded to thrust his erect penis through the hole for additional stimulation.”
– Carin Bondar

Sexual activity may also help some animals to reiterate their social hierarchy and may allow individuals to climb the ranks.

In some cases, animals may engage in non reproductive sexual activities such as same sex sex in order to gain sexual experience.  It’s interesting to note that it seems that same sex activity appears to be more common in captivity (although that could just be because its easier to observe), possibly because of a lack of alternative options and greater need for stress release.  In a similar way, you tend to find higher than ‘natural’ rates of same sex activity in prisons.

Time for another example!  Most penguins are not monogamous but it is by turning to Adelie penguins that we really get our eyes opened.  A scientific paper from 1915 had been hidden away for years, labelled not for publication and when it was rediscovered in 2009, it became clear why scientists of the time were reluctant to publicise the observations.

“They were ‘gangs of hooligan cocks’ whose ‘passions seem to have passed beyond their control’ and whose ‘constant acts of depravity’ run the gamut of masturbation, recreational sex and homosexual behaviour to gang rape, necrophilia and paedophilia.  Chicks were ‘sexually misused by these hooligans’, including one who ‘misused it before the very eyes of its parent’.  Strayed chicks were crushed and ‘very often suffer indignity and death at the hands of these hooligan cocks’.”
– Lucy Cooke quoting Dr George Murray Levick

Whilst this all sounds incredibly shocking, there is an explanation.  Adelies get together in October, flooded with hormones and only a few weeks to mate.  Young males are inexperienced and don’t really know what to do or how to act and this can lead to some questionable activity…  In their hormonal eyes, a frozen penguin in the right position can look a lot like an interested female… Apparently necrophilia isn’t just restricted to penguins…  Lucy Cooke references pigeons mounting dead house martins, male house sparrows attempting to mate with dead females and the same going on with a couple of pheasants…

In addition to all of this wonderfully interesting and fun goings on, we have those animals which change sex.

Suggested reading:

Fairy Penguin: Animal Dreaming

wp-image-1277557612jpg.jpg

As we’ve already seen the fairy penguin is the smallest of all penguins and is the only species of penguin which breeds in Australia.

Mating starts in June with males calling for females whilst standing with flippers above his back, his neck stretched, and head upright facing the sky.  During courtship, the two penguins stand with flippers spread, heads bowed and walk in tight circles around their nest site, calling as they do so.  This calling will continue to help build and maintain their pair bond.  Together the parents will big a burrow for their nest.  They will then defend the area around the entrance with aggressive posturing, calling and if necessary will resort to pecking, shoving and slapping.

Once the fluffy and helpless babies arrive, the parenting is shared.  Mum and dad alternate daily with one standing guard and the other out fishing.  After a couple of weeks, both parents will go to sea, returning in the evening to their chicks.  Because of their size, predators are a big risk so they tend to either go out to sea for the full day or stay home for the full day instead of running the gauntlet to get from sea to nest several times a day.

Adult penguins forage for food at sea, mostly from dawn to an hour before dusk. After feeding, they form tight groups and remain at sea until dusk.  Then they waddle across the beach and head to their burrows.  Then, under cover of night, they are known to make a lot of noise and disturb humans…

The keyword for the fairy penguin is willpower and willpower is necessary when you are such a little penguin in such a big world with so many threats.  The fairy penguin overcomes any difficulties with being small and flightless by embracing the sea.  Their choice to burrow also suggests they are accepting their vulnerabilities and instead of wallowing, they are working with them.  Larger penguins would find it difficult to make a burrow big enough for the family.  The fairy penguin comes to shore in groups, again they have noted the risk of predators and are working together to lessen this risk.

Do not hide from yourself, do not fret over your limitations, instead harness your strengths and use them to your advantage.

Penguin

wp-image-1277557612jpg.jpg

Penguins are awesome so I’m doing two posts!  One about penguins in general followed by one specifically looking at the Fairy Penguin, the smallest of the penguins at 40cm tall.  The biggest penguin is the emperor, about 1.1m tall.

The names of all the different types of penguins are amazing… We have the kings, the fairys, the macaronis, the chinstrap and the rockhopper, the royal and the gentoo to name a few.  The variety is reflected in the behaviour – the smaller ones don’t dive as deep and tend to live in warmer places.  Breeding activity varies from species to species, king penguins are monogamous for a season but unlike some types, don’t generally keep the same partner for life.  Most lay two eggs although the larger ones tend to stick to one.  Emperor penguins produce milk.

As you can see, there is a diversity amongst penguins and whilst we have a set idea about penguin baby raising, different types have different arrangements and ways of looking after their fluffy little chick.  Some penguins use a little flap of their tummy fat to keep the egg safe and warm.  This is a much nicer way of thinking about our bodies – whilst society dictates we should all be stick thin, the penguin body shows us that our fat and our tummies are used to protect vital life; in the penguins case the egg, in our case, our organs.

As you probably know, penguins are black and white flightless birds which are highly adapted to life in the water.  Their wings have become flippers covered in very dense feathers, their tails are used to balance on land and their eyes are adapted so they can see underwater.  In terms of that cute little tuxedo, their markings are used to camouflage them in the sea – from underneath they blend with the sky, from above with the water.

When they get out of the water, they do that really cute little wiggle which is adorable.  But also functional – it is to help them trap air in their feathers for insulation and they do it after swimming because the water pressure will have pushed out a lot of the air they had trapped.

Once on land, they waddle or slide on their tummies – tobogganning – to conserve energy and to move quickly.  The reason their wings or flippers stick out as the walk is partly for balance but they actually can’t fold them unlike most birds.  This awkward gait can make the penguin appear uncoordinated on land but the same body comes into its own in the water where it swims with grace – we all shine in the right environment.  Do not judge a fish for their inability to climb trees.

The Fiordland penguin, also known as Tawaki was, in Maori mythology, a god that walked the earth in human form. Humans didn’t realise that Tawaki was a god until he climbed to the top of a large hill, took of his clothes and dressed himself in lightning, hence the yellow crest we see on him today.  It was only because a man was hiding in the bushes and saw this that the people started to believe Tawaki was a god.  We have expectations about how things should look and act, we expect birds to fly and yet the penguin doesn’t.  There is a dual consideration here; are you expecting certain things from others and are you embracing your own uniqueness and talents?  Are you berating yourself for not being able to fly and missing out on the fact that you’re an awesome swimmer?  None of us are good at everything, sometimes it takes a while to find our own skills but it’s a worthwhile journey of discovery.  The same is true when you’re looking at other people.

Other than Tawaki, there don’t seem to be many myths about penguins, possibly because they don’t tend to live near humans.  However there is one much quoted mention of them in aboriginal mythology as guides for the water serpent, Jeedara, when he attended a ceremonial gathering.