Rodent

Rodents are a group of Small pets. They are introduced in The Sims: Livin' Large, The Sims 2: Pets, The Sims 3: Pets but mostly in The Sims 4: My First Pet Stuff.

The Sims: Livin' Large
In Livin' Large, the guinea pig was introduced. If the cage wasn't cleaned for a long time, and it bit a Sim, the Sim would become sick. The fastest and easiest way of curing this sickness is to buy the guinea pig painting and look at it.

The Sims 2: Pets
The Sims 2: Pets adds womrats. They can be purchased by buying the appropriate cage in Buy mode, and then using the cage's "Restock" option, which can only be done if the cage is empty and clean. Womrats cost §75. The womrat cage is called the FMCU 3000.

The Sims 3: Pets
Rodents are one of the various kinds of minor pets introduced in The Sims 3: Pets. They can be caught outdoors like other collectibles. Rodents can be kept temporarily in the inventory, but they might eventually run away if kept for too long. Rodents need to be placed in terrarium and be fed regularly.

Being a Collectible Pet, Rodents do not have a max allowance. As long as you can afford them, you can have as many as you would like.

List of rodents
Although they are referred to as rodents in-game, shrews and hedgehogs are not actually rodents.

The Sims 3: Pets introduces 7 Rodent types. Each has its own rarity and worth.

There are only 3 common rodent available via the "Stock a Terrarium" option. THe rest must be caught in the wild.

The Sims 4: My First Pet Stuff
The Sims 4: My First Pet Stuff reintroduces Rodents to The Sims 4. This time, it adds four new rodents in special cages. Only one rodent is allowed per cage.

Cage
As long everything is available in their cages, rodents would be able to stay healthy. When a rodent cage is purchased, the new rodent will be well fed.

You need to replenish the food bowls and clean the cage as time goes on.

The following interactions are available on rodent enclosures:
 * Clean Habitat
 * Fill Food
 * Feed Treat
 * Observe
 * Play With
 * Purchase Rodent
 * Release
 * Rename
 * Study Rodent (Child/Teens Only)
 * Talk
 * Investigate and React (Cats and Dogs) (Require The Sims 4: Cats and Dogs)