Schaus’ Swallowtail is endemic to south Florida and one of the rarest butterflies in the United States. The swallowtail was among the first insects placed on the U.S. endangered species list, and since the 1980s, researchers at the Florida Museum of Natural History have been keeping tabs on those living in the Florida Keys.
In 1985, Thomas Emmel, founding director of the McGuire Center for Lepidoptera and Biodiversity, former curator and posthumous co-author of the study, established a Schaus’ swallowtail monitoring program on Elliott Key, a remote 7.5-mile-long island within Biscayne National Park. Using a strip of land originally cleared for highway construction that spans the length of the island, field scientists surveyed butterfly populations every spring, bearing the relentless heat, humidity and mosquitoes. Their dedication yielded worthwhile results.
Long-term data is important to help determine the best actions needed to conserve a species. Population trends are nearly impossible to capture in a snapshot, which is why short-term studies don’t always tell a complete story.
Schaus’ Swallowtail hasn’t just adapted to hurricanes, they also benefit from them. When a hurricane blows through the Florida Keys, strong winds strip trees of their leaves, and storm surge floods the land with seawater. The immediate effects are detrimental for the butterfly. However, Schaus’ Swallowtails seem to bounce back better than before in the following years.
Schaus’ Swallowtails are specialists, meaning they require specific plant species on which to lay their eggs and feed. Their survival relies on two known larval host plants: torchwood (Amyris elemifera) and wild lime (Zanthoxylum fagara).
Both are fragrant and belong to the citrus family, ranging from large shrubs to small trees. They occupy the forest’s understory, and after a hurricane, they explode with fresh leaf shoots, which are the preferred food of Schaus’ Swallowtail caterpillars. The caterpillars feed preferentially on fresh foliage which is much more tender and easier to digest.
The host plants and therefore Schaus’ Swallowtail live in dense forests where not a lot of light reaches the ground. After the hurricanes temporarily knock out their bigger, taller competitors, the host plants flourish. When additional sunlight hits the forest floor, it triggers the rapid growth of new leaves. All that new growth, in turn, means more butterflies.
Historically, Schaus’ Swallowtails were much more abundant and were distributed throughout the Florida Keys and parts of the Florida mainland. Habitat loss and urban development have severely impacted the butterflies. Schaus’ Swallowtails are now thriving on protected land, but a new, far more daunting challenge lies ahead—one that threatens both humans and butterflies. While they benefit from some periodic disturbance, larger storms might be too much of a good thin
As a precautionary measure, researchers have begun reintroducing Schaus’ Swallowtail to unoccupied conservation lands, with the aim of establishing self-sustaining populations as part of a five-year draft recovery plan. The more spread out the population is, the less likely it is for the species to be wiped out by a single storm.
The study was published in the journal Biological Conservation.
