you have a lot more time than 3 months. the clock starts when Arlug shows up. she doesn't show up until you get $5000 donation for marine animals. so what i did was i put all the marine animals that came with the scenario in the back, and kept the traffic low there. meanwhile i built up big mixed habitates like savannah, scrub, tropical rainforest, and desert, etc. i used non-marine animals to get me to 5 stars. then i kept declining animal adoptions until orca shows up in the first 2 slots (so that i won't lose them if the zoo loses fame). i kept the zoo going and used the proceeds to build up the complete living quarter for Arlug, including food, enrichment objects, etc. once i got it all set up i started adding more marine animals and beefing up the tank areas, etc., to increase donation for marine animals. then as soon as Arlug shows up i released all animals and sold everything, which gave me a total of about $60K cash, enough to buy a new orca and kept them living for a while. then i just wait. it worked.