Male Sumatran Orangutan, April 2013

Dagu, born April 1985.

He looks better here than in the postcard- but not a typical looking Sumatran in some respects, the big heavy forward-hanging pads and short beard are more like a Bornean(I am not suggesting he's anything other than Sumatran though, as I know he is).

I've got a few more photos which show him in his full glory. I'll carry on with the uploading when I have time.

His pads hang forward when he's less than happy... around the time this image was taken, Dags was kept from his two favourite females, as one was pregnant, and the other had a small dependent infant. When he's his usual self, his flanges are much more 'open', and he seems to take on an entirely different posture!

Also, he is facing many challenges from his son, Jaya, who really needs to be moved to a group of his own females (happening very soon!).

R

As Pertinax said, what an interesting observation: might this be a general characteristic for male orangs? If so, in the wild, the most dominant male in a region would have the flattest and widest face, which could help the females to choose to mate with him.

Alan

I've never heard a satisfactory explanation of exactly what the purpose of the adult males' pads are 'for'. So some sort of mood or other signal indicator might fit the bill.

Their development can certainly be surpressed for up to several years if a male is kept in too close proximity to an older, dominant one, though I believe they will always develop eventually, even in that situation.

Our Head Orangutan Keeper believes they function like cupping your hands to project your voice, when the males are long-calling with both hands occupied in swinging through the trees. Certainly if Dagu is calling and you stand in front of him, the frequency spread at once rattles your chest and rings your ears... but it's mostly low resonances.

Gibbons are loud and arboreal, but like most canopy dwelling animals (birds, callitrichids, squirrels etc) they have a relatively high frequency call. Perhaps the low register of a big male orangutan needs help in projecting across the (rapidly declining) forests.

You can hear Dagu calling in the background (and his moments old daughter crying) here - https://www.facebook.com/video/video.php?v=10151435420107041&saved

Incredible, huh?

Presumably long-calling because of the excitement of the birth etc.

I guess 'Dagu' isn't kept with either of the new mothers yet- or is he?

I've heard that before about the pads helping to amplify the longcalls in the forest- it certainly makes some sense.