Wednesday, September 30, 2015

Lianas, delicious fruits, and a chimp's hand

The current site Lingering Shape in West Africa has two special features: extensive scenes of chimps savoring fruits and exciting footage of them crossing a flooded area swinging in lianas. Both features combined helped us to identify here one very special chimp.

We first paid attention to him when he crossed the flooded creek with a group of male chimps. Adult male chimps do not swing elegantly and dynamic on lianas as you might imagine. Their body size and weight urge them to be careful and slowly climb or walk on the unstable path. So, it surprised us that one of them carried something in his hand while crossing although he had rather difficulties keeping his balance. We only saw his dark back and part of an ear, so trying to match him seemed next to impossible.
Even while having a hard time to cross a flooded area, this chimp does not use his right hand for climbing (link to video)

Days later and later again, we found more videos of a dark male carrying something in his hand while walking alone or with others. As we had now seen in other videos with how much gusto the chimps fed on fruits, jokes starting around (“gourmand or gourmet?”) as he apparently always brought his own snacks. But after five or so different scenes, ascertainment that it is always his right hand kept curled in front him, and looking closely at this hand, we were wondering whether there was actually something in it. Most pictures were from quite a distance, but we could not see anything in his hand. What we could now say with the additional footage: there is a chimp with dark fur and a prominent brow ridge who is quite bald and walks always a bit hunched as he uses only one hand for knuckle-walking. We started a discussion thread “Adult male – the right hand issue” to talk about this. 

Always walking with his right hand carried in front of him (link to video)

We then remembered that we had earlier found a male chimp in the long feeding scenes that we described as somehow hunched. Our citizen scientist “Boleyn” had proposed the match based on two different scenes and named him Ebony for his very dark fur. The facial features like the prominent brow ridge fit “our” chimp very good. Reviewing all videos with Ebony, we saw that he also did not use his right hand for walking or standing up. At the time of the original matching we did not think about it much as he and other chimps were gathering fruits – picking them up with one hand, sniffing to determine ripeness, and collecting them in the other hand. That is what you expect of chimps feeding in a fruit “garden”. By looking closer into his right hand – and in striking comparison to a hand full of fruits of his buddy Rufus, we could now see that there was indeed nothing in his hand. Putting once a fruit in his right hand, we saw it rolling away. 

Ebony's damaged right hand is of no use for holding fruits (link to video)
In contrast to this, Rufus' hand is filled with delicious fruits (link to video)
We suspect that his right hand is somehow damaged, cannot really grab and support him while walking – or hanging in lianas. But then, this characteristic helped us to determine his identity.

We are not sure what happened to Ebony’s hand and whether it is a permanent injury or something he will recover from, but this special trait helped us at Chimp&See to identify this chimp. It was a great detective work of everyone involved.

We welcome you at Chimp&See! Come over to watch and try to help us match chimpanzees; if you find a match you can even name that chimp!

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