I read the info on the symurghs and the thodamas under the help section. But nowhere in there did it mention how to obtain them. I got mine through the pet sales, which has a steady stream of wild born symurgh so i assume they must be able to be obtained somehow. I have seen no thodamas anywhere, so i assume however you get them is difficult or a special event thing but that is as much as i know of them.

So yeah, how and where do you find the two alien species?

Answer to this question also lies in the Help section, more specifically in the Battlefield Tactics FAQ. (http://beastkeeper.com/tactics-faq)

"In the center of the map there's The Portal. You will earn rating points, silver coins and a Symurgh or Throdama every 10 hours if you're holding this zone."

That is the source, from which the wild ones are coming.

Also, there are periodically events that have symurghs and throdamas as some of the prizes. This http://beastkeeper.com/thread/4674 was the last event.