The results of a four-year study, cataloging the butterfly species of St. Eustatius over the winter months of 2009-2012, have been published. This project also provided an update to species lists for the Dutch Caribbean islands of St. Eustatius, Saba and St. Maarten. The butterfly faunas of the three islands total 44 species, including seven new species records for St. Eustatius.
Aside from being a colorful addition to any garden, butterflies are of great importance to local ecosystems. Butterflies are often used as an indicator of a particular environment. For example, dense and diverse butterfly populations typically correspond to areas of equally dense and diverse plant life and other invertebrates, which often include important pollinators and natural pest control. Furthermore, because butterflies are so sensitive to changes in their environment, ecologists can use them to study the overarching impacts of climate change, urbanization and habitat loss within a specific area.
Bridging the knowledge gap
Although these species have great ecological importance, very little is known about the species-specific distribution throughout most of the Caribbean.
To narrow this knowledge gap, researchers from Wageningen Marine Research, St. Eustatius National Parks Foundation (STENAPA), Caribbean Netherlands Science Institute (CNSI), Wageningen University, Carmabi Foundation Curaçao and the University of Florida monitored butterflies on St. Eustatius. Studying various natural habitats, the butterfly populations within the three windward Dutch islands were compared to those of neighboring islands. Along with visual surveys, literature records for nine nearby islands were also collected to compile a more complete list of known butterfly species.
Local fauna and flora
This study monitored butterflies on St. Eustatius over the winter months (January-April) for four years (2009-2012) along transects of four different habitats. These habitats were the Quill crater, Quill flanks (wind sheltered, southwestern side), lower Quill flanks (of the outskirts of Oranjestad) and the northern hills. Hypolimnas misippus (Source: Hannah Madden)This project also provided an updated species lists for the neighboring islands of Saba and St. Maarten. In total, 44 species of butterflies were identified between the three islands, including seven new species on St. Eustatius.
Of the 44 documented species, nearly half were from the Pieridae family, a butterfly group known for being large, strong and fast flying. These butterflies were noted in each of the four different habitat types. The second most common butterfly was from the Lycaenidae family, a physically smaller group of butterflies known to inhabit dry, resource-limited areas. These species were found in all but one habitat, the Quill crater.
The availability of larval host plants determines if local butterflies are capable of reproducing on the island. Larval host plants were documented as being present for all but two of the butterfly species and seem to make breeding possible for the other 42 species.
Photo: Phoebis sennae (source Michiel Boeken)
Importance of elevation
Traditionally it was believed that land area was the greatest limiting factor for butterflies. This study, however, along with previous studies, shows that habitat diversity and elevation play a more important role. Even though St. Eustatius and Saba are smaller in size than neighboring islands, they host a large number of the total butterfly species.
Understanding the geology, urbanization, agricultural history and other human factors on an island can give insight into the struggles these species face. Deforestation, overgrazing by feral livestock and the use of insecticides can greatly reduce local butterfly populations.
Having an updated species list for resident butterfly populations will aid conservation efforts on these islands. Because they are important indicator species, butterflies can help sound the alarm for larger ecological trends that could be adversely affecting these islands. This research will help to guide local conservation efforts leading into the future.
Butterflies of the ABC-islands
For those interested, similar work is already available for the leeward Dutch islands. The guide book Butterflies and moths of Curacao, Aruba and Bonaire, by Debrot and Miller, provides full-color pictures and information about 78 species found on the ABC-islands. The book can be obtained through Carmabi and in bookstores.