Ive been wondering if ethologists needed to specialize in one animal type. Such as, if I wanted to get a masters in ethology would I have to also study mammals or reptiles at the same time, or do ethologists just study the behavior of any animal type depending on the current job given to them.

No need to specialise on a single taxon. Many do of course (e.g. some people are fascinated by primates, or fish, or some particular species of bird), but probably more common among professional researchers is to focus on particular types of behaviour e.g., mate choice, parental care, aggression and the general principles that explain them across taxa.

Regardless, while a masters or PhD project in ethology is  - by its very nature - often quite focussed on a single animal species, we all need to try and see the big picture by reading around what is happening with other species.