What dangerous animal does tom want jim to have?

Huck and Tom spend the next day catching creatures to live with Jim in his cell. They first gather about fifteen rats, but Aunt Sally's son frees them by accident and both Tom and Huck receive beatings for bringing rats into her house. Determined, the boys catch another fifteen rats, along with some spiders, caterpillars, frogs, and bugs. At the end of the day they gather some garter snakes and put them in a bag, but after dinner they discover all the snakes escaped in the house as well. Huck remarks that there was no shortage of snakes in the house for quite a while after that.