Marnie does say some animals have gendered differences but these are null as she may use his/her fr the animals when purchased. Male pigs somehow still give birth and male cows still give milk............
As far as the cat/dog it seemed to use they/them so it's not specified. Honestly your probably safe to say it's male because cats drop litters fast and if it was female your home would be covered in kittens..........its so fluffy..... Ehm had to get that out of my system. I mean Marnie could of found a spay/neuter animal but that would imply a prior owner