Our gibbon gals: Large and in charge!

Walking back toward the office earlier today, I saw one of our gibbons, Robbie, sitting at the end of an aerial runway, enjoying the winter sunshine. A moment later, along came his mate Dianne. She got to within about six inches of him when he suddenly stood up, climbed past her, and sat down again about three feet away, while she settled down in the exact spot Robbie had just vacated. A classic “displacement” move.

Robbie, here, likes to hang out at the end of this runway—but he knows to get out of Dianne’s way!

Among our gibbon couples, the females are generally dominant to the males. Since female gibbons are about the same body size as males and have about the same size canines (a rare configuration: male primates are usually significantly larger in both departments), a female gibbon could theoretically hold her own in a one-on-one fight.

Fortunately, it almost never comes to that. The males instinctively know that their partners are an even match and don’t tempt fate. Our animal care staff sees confirmation of male restraint in the presence of their female companion on a daily basis.

Take feeding time, for example. Most of our females are the first at the food bucket, and the males patiently wait their turn. In the wild, it makes sense for females to get first dibs on food, since pregnant and nursing female mammals require lots more energy than usual. Especially when nursing a rapidly growing infant, primate mothers see their caloric needs go up by about 50 percent. They are literally eating for two.

Brandon has learned he needs to feed Michelle (top) her banana first, while Louie-Louie waits his turn, below.

This kind of behavior is also evident in captivity, sometimes to the extent that we have to take compensatory action. For instance, when we give our gibbons their nightly banana, sometimes the female will get cranky if the male is served his first. Our newest caregiver, Brandon, has learned about this first-hand. Louie-Louie is usually at the front mesh of his indoor enclosure when Brandon comes by for the night run. Louie-Louie’s mate, Michelle, typically hangs out toward the back of their night quarters and will only saunter toward the front after due deliberation. But if Brandon makes the mistake of feeding Louie a banana first, Michelle will threaten Brandon (“Hooooo! Hooooo!”), give Louie the evil eye, and even snatch his banana away.

When we handed around dates in a trick-or-treat pumpkin for Halloween this year, Courtney refused to let go until she’d eaten every last one.

Courtney and her companion Whoop-Whoop are another example, only the feeding competition there is even more noticeable. Courtney has always been a good eater. But it’s gotten to the point where she’ll eat everything in her bucket—and as much as she can out of his, too. Now we feed them not only in separate buckets, but in separate enclosures. And if we want to be sure that Whoop-Whoop gets to have his share of any special treats—like dates or berries—we hand-feed him while Courtney is busy elsewhere.

Sometimes the female control is a little more benign. Like in Scrappy’s case. He sometimes has, shall we say, emotional stability issues. As Brandon was telling me earlier today, a friendly game of “try to grab Brandon’s pant leg” might easily ramp up into a “try to eat Brandon’s pant leg” wrestling match. This happened one day not long ago, but what was really interesting was the reaction of Uma, Scrappy’s mate.

Scrappy likes to tug on our caregivers’ pants (here, he’s got hold of Cheri), but he sometimes gets a little too excited about it—until Uma calms him down.

When she saw Scrappy get all worked up over Brandon’s attire, Uma came over and tapped Scrappy lightly on the shoulder—and he abruptly let go and walked off. She has done the same kind of thing (a tap on the shoulder or a quick hug) to get Scrappy to disengage from dried old stalks of bamboo that Brandon was trying to clear out of their enclosure. Without her restraining influence, Brandon would have had a difficult time wresting away the faded greenery.

Our gibbon gals clearly use their power for good as well as evil!