Chimpanzee culture is very political. In order to rise to the top of the hierarchy, or to stay on the good side of those at the top, a chimpanzee must know who to rub elbows with (so to speak) and when, and to what degree.
One of the ways a subordinate chimpanzee can show respect to a more dominant chimpanzee is by offering an elaborate greeting. These greetings occur when the two individuals meet after being apart from each other for some time. Most greetings involve some sort of vocalization (a breathy pant or a pant grunt, as you’ll see in the video) on the part of the subordinate chimpanzee. Generally, the louder the vocalization, the more tense the subordinate chimp feels.
Many of the chimp-to-chimp greetings here at CSNW are directed toward Burrito. Although he is not the most dominant chimpanzee here — he doesn’t quite have the skills, probably because he lacked a proper male chimpanzee role model growing up — his displays are pretty effective at intimidating the girls, so they try their best to appease him whenever they can. You might notice in the video that Burrito often turns his back or squeezes his eyes shut when he’s bring greeted. As much as he tries to show the girls who’s boss, the truth is he’s pretty nervous in social situations. Failing to graciously receive the other chimps’ greetings is probably one of the things holding him back from the dominant status he seems to desire.