You don't own the copyright without a model release, but, in many (but not all circumstances), you can sue for renumeration if your likeness is used without your permission. With the exception of some work-for-hire scenarios, copyright is always with the creator (but the creator must be human; monkeys don't count[1]).

1.http://www.theguardian.com/technology/2014/aug/22/monkey-bus...