My Four Giant Indoor Vivariums are Evolving: Major Change Coming

A major change is coming to my four giant ecosystem vivariums, affecting all the life living within. The creatures of the ecosystem have begun altering their behaviour, retreating below ground, and even dying off. A natural process? The answer is quite surprising, and Mother Nature left me speechless once again, as I surveyed my four giant ecosystem vivaria for the ominous signs of this 'Great Change'.