Currently, the only known free-ranging population of Gambian giant pouched rats occurs on Grassy Key in the Florida Keys. However, they could reach the US mainland by natural dispersal, or more likely, by hitching a ride on vehicles (such as debris trucks heading to landfills) leaving the Keys for the mainland. In the Keys, the Gambian rats may pose a threat to the endangered Key Largo woodrat and other species of plants and animals.
Additionally, if this species reaches the mainland, there could be extensive damage to the Florida fruit industry and other agricultural commodities. Gambian rats are known to damage agricultural crops in their native Africa. Because of their large cheek pouches, they are efficient at hoarding food. Gambian rats also pose a risk of monkeypox and other diseases. Gambian rats imported into the US for the pet industry were responsible for an outbreak of monkeypox in the Midwestern US in 2003. A climate/habitat modeling exercise suggested that their new range in North America could expand dramatically if they reach the mainland.