As noted, my cowboy collection is not available. Most of it is on slides that need to someday be digitized. Maybe next year. But I found this image that appears to slightly fit the criteria. They are heading due west, according to the compass in my car, up the "mountain (to them)" on the White Handed Gibbon Island at Lion Country Safari. So, for what it is worth ...
The turtles are very interesting as they come up on the bank when the Gibbons are being fed and the Gibbens hand feed them. A prior post showed the interaction.