The vegetation on the flat Baboon Islands is typical of a tropical rainforest in the form of a riparian forest.

For the protection of the animals and visitors, entry onto the islands is not permitted, as chimpanzees can be highly aggressive towards humans.

Apart from the common chimpanzee (Pan troglodytes verus), River Gambia National Park is also home to the Guinea baboon (Papio papio), green monkey (Chlorocebus sabaeus), western red colobus (Piliocolobus badius), and marmosets (Callithrix).

In addition, the park is home to the aardvark (Orycteropus afer senegalensis), honey badger (Mellivora capensis), serval (Leptailurus serval brachyura), Hausa genet (Genetta thierryi), African clawless otter (Aonyx capensis), and West African manatee (Trichechus senegalensis).

Reptiles are likewise plentiful, and include the Nile crocodile (Crocodylus niloticus), snakes, and lizards.