I really enjoyed this one played until I ran out of levels. The visuals are excellent even more so that you say it's a first try with hand drawn 2D!
If I was to give feedback it'd be great if they moved just a little fast or have the option to speed them up and sometimes people like me like to just test the waters first before throwing a solution together. I also feel it would be a bit easier to grasp if the tiles took effect when the critters entered the tile and not the tile before... that might just be me though.
The unique abilities for each animal was a nice tough, definitely a lot of potential to expand this. Great work.