You will need something like that(example for php):
$animals = [
new Animal('Elephant',100,10),
new Animal('Mouse',1,1),
....
];
$animal1 = $animals[ array_rand($animals) ];
....
well, actually it depends on a code you've already written, but you got the basic idea.
EZ job for good coder but still will take a couple of hours to make thing shiny.