Hi Miquel

You can use pageviews to view the data for the actual category pages. For example:

https://pageviews.wmcloud.org/pageviews/?project=es.wikipedia.org&platform=all-access&agent=user&redirects=0&range=latest-20&pages=Categor%C3%ADa:Ciencias_naturales|Categor%C3%ADa:Historia

Does this work for you?

(I'm not sure what you want exactly)

Regards