In Wikibooks it is suggested that to have subfigures, one should use the subcaption package.
However, in the given example, the caption package is also included. Is it necessary here? If so, what is it for? Usually, including captions (e.g. \caption{Pictures of animals}) does not need the caption package.
It is not needed in the example as the (current) subcaption package code includes
\RequirePackage{caption}[2012/03/25] % needs v3.3 or newer
which would load caption if it is not loaded already. You'll notice the same thing when you do not load caption but include \listfiles in your preamble and check your .log file.
And yes, there is no need to load caption in order to use \caption. It provides a host of features though...
