272 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



borhood of Mpororo, where a solitary bed was noted in a tree, their 

 easily recognized sleeping quarters w^ere not seen in the localities where 

 the gorillas were accustomed to roam. 



One afternoon I had a grand view of a band of about a dozen chim- 

 panzees which had decided to spend the night in a little reentrant val- 

 ley on the opposite hillside, and several hundred feet below my tent. 

 With the aid of a pair of powerful binoculars I was able for several 

 hours, till darkness put an end to the entertainment, to watch closely 

 what they were doing when absolutely at their ease and never a sus- 

 picion of the watcher above. What struck me most was the extraordi- 

 narily human way in which these apes moved about the tree tops. 

 When alarmed, or when speedy progress is desired, the chimpanzee 

 uses primarily its long arms. But when feeding unconcernedly aloft 

 and wishing to go down the nearest way to another branch it was most 

 illuminating to see the care with w^hich the descent was made. Grasp- 

 ing securely with both hands the branch it intended leaving, the chim- 

 panzee slowly lowered itself till a foot reached the new stance, which 

 was tested thoroughly, then followed the other foot, and the same per- 

 formance repeated, after which, if satisfied, the ape let go its hands 

 and, well-balanced, very cautiously lowered its body till the hands 

 could grasp fresh security. Another point that was particularly strik- 

 ing was the fact that normally one arm always hung on tightly to an 

 overhead branch, suggesting that the chimpanzee is not really at home 

 in the trees, for those under observation did exhibit the most extraordi- 

 nary care in their movements and an almost ludicrous solicitude for 

 their own safety. 



It was rarely possible at any one time to obtain a clear view of 

 more than two or three individuals, but numerous, stationary, long, 

 hairy arms, hanging on like grim death to the branches, indicated the 

 whereabouts of most other members of the troop. For minutes on 

 end, 12 minutes was the longest period timed, these arms stretched 

 upward absolutely motionless. An adult male who desired to move 

 from one treetop to the next was most comic. First of all he crawled 

 out along an upward slanting branch which was really stout, and 

 provided a ready highway to an equally thick branch of the other 

 tree. But halfway his nerve failed him and he spread-eagled him- 

 self over the branch and thoroughly tested the whole structure with 

 his hands and feet. Then, after several half-hearted attempts — there 

 must have been something very tempting on the other tree — he 

 plucked up courage and cautiously raising himself half upright 

 pushed himself forward in a regular "belly-flop", and landed on his 

 face and chest amidst the branches of his goal. 



Just before dusk the whole troop busied itself building beds in 

 three adjoining bushy-topped trees. These operations being mainly 

 inside the canopy of the trees and the light failing it was impossible 



