So I coded a life simulator. The rules: starting with about 20 critters in a world of vegetation critters can (a) move randomly each turn, (b) eat vegetation if they can, (c) reproduce if a male meets a female.
Critters can die of malnutrition and old age. In this video you see a slow start to the colony, followed by a population explosion after about 56 seconds. The colony dies off after it has eaten most of the vegetation available.
Source code: coming soon!