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[[circled]] 19 [[/circled]]

[[underlined]] Ateles [[/underlined]] ssp, Jun 24, 1959, II.

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The MFB is presumably hostile - at least in part. The animals usually give it whenever I appear. It may also contain a "friendly" component". The animals are used to getting food from human beings. It is apparently never accompanied by such overt hostile acts as actual escape or Jud.  And the Black [[male symbol]] and/or the the small Black [[female symbol]] uttered MFB's when they were wrestling together (see below). 
The mouth is apparently opened and closed during MFB's, but only slightly. The Blacks usually don't combine the MFB's with any ritualized facial movement except PL. I am not sure exactly what proportion of their MFB's are actually accompanied by PL.  It is obvious, however, that some are and some aren't. The Red [[male symbol]] usually does PL during his MFB's, and sometimes (but relatively rarely) both PL and OCB (see below). It is my impression that the MFB's of all the animals are reactions of relatively moderate intensity. The animals do not seem to be greatly excited in any way when they utter MFB's. Brief MFB's sound rather like short, not very distinct, hoarse or rusty Trills (although they are much less distinctly trilling than the Trills of the young Red [[female symbol]] - see below). They may well be related to Trills - or even, perhaps, the only Trill-like pattern these 4 monkeys have - but I find the whole subject of Trill-like notes in these 4 animals rather difficult to analyze (see below).

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The Red [[male symbol]] has a most distinctive OCB pattern.  While the lips are puckered in a more or less extreme PL pattern, the lips are also opened & closed very rapidly. This is quite conspicuous.  The lips are really opened quite far during OCB - without, I think, very much in the way of opening and closing of the mouth in many cases. Many OCB's and PL are quite silent.  Others are accompanied by one or two (possibly three or four) brief and rather