A Visitor at Dawn

by Cristi Richards

Flying Fox seen over Cockscomb, Tutuila (photograph by Benjamin Richards)

Preparations for each day of diving generally begin before sunrise, when a quiet, sleepy hush still envelopes the ship. This seemed especially appropriate when yesterday morning, just before sunrise, a silent, graceful silhouette was observed gliding behind the ship. It wasn't a bird but a flying fox or fruit bat.

There are three species of bats living in Samoa, two large fruit-eating bats and a smaller insect-eating bat, which are the only three native mammals in the Samoan Islands. These can seem odd to visitors coming from places where bats are small and generally hard to find or see. In Samoa the sight of a flying fox is a common occurrence. The bat following the ship this morning was one of the fruit-eating varieties which can attain up to a 3 foot wingspan and making it either a Pteropus samoensis (Samoan Flying Fox) or a Pteropus tonganus (Tongan Fruit Bat). While most bats are nocturnal, these bats can be seen throughout the day soaring on thermals or moving between roosting and feeding sites during the dawn and dusk hours.

Both species of bat consume a variety of foods including nectar, pollen, sap and the juice of fruits and leaves. Eating only the juice, the bat will chew on the fruit and press the pulp against the roof of it's mouth creating a pellet of dry pulp known as an ejecta. The ejecta is then spit out to make room for more pulp. This process makes it easy to determine where bats have been feeding and by analyzing the ejecta (commonly found on the hood of your car if you happen to park under a breadfruit tree).

The fruit bats found in Samoa also play an important role in pollination and seed dispersal, increasing the productivity of fruit trees transporting seeds to cleared areas. This aids the natural reforestation process. We are not sure how our flying fox visitor came to be sailing behind the Hi'ialakai instead of feasting in a breadfruit tree, but it was an impressive sight that caught the attention of everyone awake at that hour.

References:
Natural History Guide to American Samoa, 3rd edition, 2009. P. Craig, editor