Answer:
No, it isn't
Step-by-step explanation:
An invasive species is characterized by an organism's appearance in an area it is not a native of, with a high capacity of reproduction that will cause it to be a threat to native species in that area. A species of organism is tagged "invasive" if it is foreign to a region/location and possess a high reproductive rate that spreads fast and causes harm to other species.
Based on the analogy given in this question about the escape of a rattlesnake from a zoo, it cannot be ascertained that it is an example of invasive species. This is because rattlesnakes may be native to that area and possess a zero threat level to the environment in terms of high spreading rate.