Are the stats static (i.e. you will only have a max of 5-10 different ones)?
CREATE TABLE pets
(
`id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT ,
`user_id` BIGINT UNSIGNED NOT NULL ,
`species_id` INT UNSIGNED NOT NULL ,
`name` VARCHAR(50) NOT NULL ,
`strength` INT UNSIGNED NOT NULL ,
`intelligence` INT UNSIGNED NOT NULL
)
Something like the above should be sufficient.
If there are going to be more dynamic ones (or ones that only take place in certain situations), then you may want to make a 1:many table but I won't go there for now because this will provide your most value.