I just so happened to be lucky enough to witness one today. YEAH! It was in fact the first copulation I have witnessed here, and it just happened to be an adulterous one. What a lucky day! (Though I can't say the same for Chinda and Chu...) So, here's how it happened. Julie and I had just stumbled across A, hooray! because we wanted to do the python with them. I briefly saw Chu (A male) but then he disappeared. Then we saw more white individuals and were like crap is this the C group? But no, because we did see Chu, who is black and all of C is white, so we knew A had to be there too. It turned out to be an intergroup encounter at the border of C and A. We hadn't been with them a minute before we saw Chao (C male) and Andromeda (A female) mating. WOAH! Chinda (C female) and Chu (A male) were nowhere in sight, but the C juvenile was hanging around. Chao and Andromeda proceeded to copulate 4 times (bummer I didn't get my camera out in time!) before finally moving apart. Chu showed up again not long after and we followed him and Andromeda for the rest of the day.
Shortly after reuniting Andromeda attempted to initiate a duet, but just ended up doing three lonely great calls while Chu seemed to give her the silent treatment. (I do not presume to know what the gibbons are thinking, this is simply my anthropomorphic interpretation of what was going on, don't take it too seriously). So, a little bit later Chu and Andromeda started a duet, together this time, but as soon as Andromeda gave her first great call: silence. Zip, zilch, nada. More silent treatment from Chu. Let me tell you, a great call without a male reply is like peanut butter without jelly, it just isn't right. About ten minutes later they tried again. This time, they got past the first great call at least, but even then, no male replies for the first two great calls, then the next three were a VERY half hearted reply, and finally he gave a reply to the next two, and on the last, nothing, again. Well, this just seemed too coincidental. Males LOVE to sing, and they never miss that many replies in one duet. It seemed like Chu was holding a bit of a grudge. After a while he got over it though and they spent most of the late morning happily grooming each other. This is really boring for us as it is just: "Ok your turn," groom for 5 minutes, "My turn," groom for 5 minutes, "your turn," etc. So, we sat bored while they groomed and ate some fruit and acted really boring. They were too high in the trees to do the python. When they finally did move they went back to where the C group was and we can't do the python when there are two group present, because then we would record two groups singing at once. It was interesting to see how they behaved at this meeting though. Andromeda was suddenly shy and kept her distance while Chu made sure to stay between Andromeda and the C group at all times.
When we got back I told the project PI about it and he said something along the lines of "Oh Andromeda, she mates with everyone!" Apparently she is not only the oldest gibbon in the study site but also the most notoriously promiscuous. She was in fact one of the first examples published of extra-pair copulations in gibbons. Way back in 1992 (See http://anthro.siu.edu/reichard/reichard_ethology_95.pdf). Shes still whoring it up over 20 years later, even though her last surviving offspring was born like 15 years ago and she certainly won't be making any new baby gibbons by mating with her neighbors (shes that old).
We also saw a barking deer (and scared it into barking and fleeing), and a cool lizard who blended in wonderfully with the leaf litter. We also saw an awesome spider with an X marked right in the middle of her web like "Insects land here!" So, it was a great day!
little froggy from the other day
"bugs land here!"
the lovely creator of the web
trouble in paradise?
do you see the lizard?
there he is!
grooming solves any problem!