A small zoo, accessible by bus, costs 8 dirhams one way (the road to Ras Al Khaimah airport). Entrance to the zoo is 40 dirhams.
I don't like zoos on humane grounds, but I was comfortable with it. The animals are not in cages, behind small fences, there is a sense of space and at least some freedom.
Predators, of course, are kept in more serious enclosures, but they are also quite spacious.
Be sure to take a couple of bunches of greens for feeding animals, almost all inhabitants eat it (5 dirhams per 1 bunch). And take the food for yourself, there is not much cafe there, but there are areas where you can eat in the shade.