spider monkey (A. fusciceps)

As you know, showing detail in a solid black animal with black eyes is difficult. In order to get enough flash power to reach out to the monkey on the island, I increased the flash exposure compensation to plus 2 and added a Fresnel type flash extender. (FYI the s in Fresnel is silent).

If I went to that much trouble for a monkey, imagine what I would have done if there were cats on the island!

I really have to say, I am not a fan of using a flash at a zoo. I never use one and I am really ok if zoos forbid it totally, because there is a difference if you make one flash photo of your dog or 1000 people flashing one animal per day.

I use flash rarely and I could see in indoor exhibits how it could be detrimental to the animals. I actually do not use a flash indoors with animals, because the high ISO capabilities of modern cameras are so good it is unnecessary. However, in outdoor situations like this in bright light where the animals pupils are already constricted, I cannot see that it would bother them much. Plus I never see anyone else using a flash outdoors like this, so they are definitely not subjected to a thousand flashes a day.

I am glad you brought up the subject, however, as we should always have the animal's well-being in our minds. There was a similar discussion on a photo taken with flash in the Cincinnati Zoo nocturnal building, where I do think it is harmful (even if the zoo allows it).