Much is known about orangutan physiology and behavior. Yet there is one thing that is still unsolved – the exact reason why some male orangutans develop a flange while others do not. These large cheek pads certainly have their advantages as we shall see - it’s most certainly about dominance and mating with as many females as possible – so why do they only develop in some males and not others?
First things first – the flange is not a physical signal that a male has reached sexual maturity as was once thought – they already have quite a while back. Even though orangutans are among the slowest mammals to reach reproductive age, between 7 and 10 years of age for the male, they are capable of producing offspring at this age. However, it is rare for the male to mate before the age of 15. Females mature at about 5 years of age but like many great apes undergo a period of infertility in their adolescent years which preclude offspring for between 2 and 4 years and will not produce offspring until they too are well in to their teens.
Before the point at which the male develops his flange he will look like an adolescent, to all intents and purposes an orangutan in a subadult stage. This retardation is believed to have a social cause and may even be socially controlled. Yet when circumstances, which are still not fully understood, are convenable, he will begin to develop his flange as well as a large muscle-covered throat patch, long hair and a distinctive musty odor. Once development starts he will have his full flange within a year.
It is thought that the presence of a flanged male within a certain geography suppresses the development of flanges in other males. What is not known is how this suppression is controlled physiologically – whether it is through the release of a hormone or through another method. Studies have shown that the presence of a flanged male does inhibit flange development but not permanently (although it can for between two and seven years which is an adequate time for a male to pass on his genes to the next generation).
What if you are lucky enough to be the only male around? Males which have been kept in zoos without anything but female company have begun to develop their flanges at sexual maturity – in other words at about 7 and years before this would happen in the wild where other males would be a constant nearby presence, territorially speaking.
So, instead of it being a hormonal trigger which delays maturation, some scientists believe that flange development is all about stress. When young males are near a flanged male, social stress may cause their full development to become arrested. That may be the why but the how is still, really, not fully known.
You might think that perhaps it is down to testosterone levels – those big guys with the huge flanges must surely have much more of it pumping around than the others, surely? However, the levels in flanged and non-flanged orangutans have been found to be the same.
Yet even when you do have a flange, that isn’t always the end of the story – things can still get tricky. Some flanged males mate while others in their proximity do not. No difference in behavior or levels of testosterone, so what is it?
What
is different is the level of oestrogens in the urine of flanged males which breed – it is significantly lower than in those which do not. It has been suggested that when the more dominant flanged males are aggressive towards other flanged males then the social stress it causes somehow triggers the production of oestrogens and the suspension of desire to procreate.
So, unless you are a male orangutan right at the top of the social pile the chances are that you will not be attracting any female attention at all. Any opportunity to
do it like they do it on the Discovery Channel will have to be conducted furtively and with some force – the ladies are not going to be willing partners. You could move away and establish your own territory far away from other males: this will trigger flange growth eventually. That might just work: once you develop physically then your throat patch will produce a growl which can be heard a mile away and the females will come flocking. Or you can stay put and hope that the old, alpha male, kicks the proverbial bucket and then, perhaps, your chance will come.
First Image Credit Flickr User Guppiecat
