Complex sentence: Manuel Antonio National Park and Corcovado National Park--where it can be seen by visitors, but it is not as commonly seen in these parks as the White-headed Capuchin or the Mantled Howler monkeys.
Split into simpler sentences: Manuel Antonio National Park and Corcovado National Park--where it can be seen by visitors. However, it is not as commonly seen in these parks as the White-headed Capuchin or the Mantled Howler monkeys.