I think these have always been my favourite animals at Oakland Zoo. Not sure exactly what makes them so appealing, but I think a major factor in there is simply that they can be relied on to be present & entertaining.
This guy was busy swinging around from branch to branch, while the other one sat looking like she had the weight of the world squarely on her shoulders.
I haven't taken my 300mm lens to the zoo in a while (in fact, even the DSLR has found itself left at home more often than not now we have a toddler & all of his paraphernalia to cart around). For the least trip though I pulled out the long lens, and risked hand holding it. Not everything came out well, but a lot did.
The white furred gibbon was sitting still on the branch for a while, making it relatively easy to get good shots of her. Her mate, on the other hand, was never still; capturing good shots of him was much harder.
That said, the one above and the one of him in “flight” along a branch are definitely among my favourite shots of these guys ever (and, since they're always out, I have a lot of photos of them).
The one thing I love about the 300mm, when it works, is the tight DoF on it. The backgrounds at the zoo are not always ideal (although the gibbons' exhibit doesn't really have much of an issue). The tight DoF blurs those less desirable backgrounds leaving the subject of the photo sharp. Just like this shot of the gibbon swinging.