For thousands of years "humpback" whales (named for their way of arching their backs on the surface before diving) visit the Pacific Coast of Costa Rica. In August, September and October, southern hemisphere humpbacks are found here, and December, January, February, March and April, northern hemisphere whales.

Adult females choose certain areas to give birth and care for their "calves". Bahía Ballena (Whale Bay) is one of these areas  and was one of the reasons for creating Marino Ballena National Park (by executive decree in 1989).

Since the humpback whale (megaptera noveangleae) is on the International List of Species in Danger of Extinction, their protection is very important. With Marino Ballena National Park and other protection of this impressive species.

In order to support this National Park and its surrounding communities, in 1997 ASOPARQUE (Association for the development of  Parque Nacional Marino Ballena and its neighbors) was formed with the participation of local non-government organizations, and together with ACOSA (Conservation Area Osa) and MINAE (Ministery of Environment and Energy), a system of "co-management" was formed in order to work more effectively and with greater benefit to the local communities. ASOPARQUE has been legally declared "Organization of Public Interest".

The reason for the annual visits of these whales, trips of thousands of kilometers, is apparently for the warm calm water, shallow protected areas around islands and reefs where the newly born may safely become strong enough before returning to their cold-water feeding grounds where their main food, "krill" (small crustaceans) is abundant. During the few months these whales are in Costa Rica, the adults eat very little (perhaps) some small fish they might capture) or nothing, and the babies consume daily many gallons of their mother's thick rich milk (they are mammals).

The song of the humpback whale is a unique phenomenon in Nature. The male emits a series of strange sounds, loud and soft, melodious like different musical instruments and sounds of other animals, for around 15 minutes, and then he repeats everything almost exactly the same, sometimes for hours. This fascinating and mysterious behavior may be heard while snorkeling, scuba diving or swimming in the waters of  Marino Ballena National Park where the whales sing, the sound waves traveling through, the ocean for kilometers. It is believed that the males sing to attract females, but no one really knows with certainty.

It is important for the people in boats who find one more whales, not to bother or approach so close as to interrupt their normal activities or put them in danger of the boat. Even though they may be 15 meters long and weigh 45 tons, and that sometimes they jump and play spectacularly, they almost never represent a danger for humans, since they are such docile animals. Whales prefer to avoid areas where there are disrespectful boaters, shrimp fishermen trawling the bottom, or fishermen using gill nets. These activities are prohibited in the area of  PNMB, where the goal is to always welcome the whales during theirs visits to our country.