To celebrate Vanuatu Language Week, Associate Curator, Entomology Melissa Kirk who has shared some research on the bataflae (butterflies) of Vanuatu. By studying their presence in one of the most at-risk countries for climate change, they can tell us a lot about changes to their environment.
Vanuatu comprises of a ‘y’ shape chain of 83 islets, atolls and islands within the South Pacific Ocean; many islands are small; however, some are larger including Malakura, Espiritu Santo, Efate and Erromango. The 12, 274 square kilometres of islands are volcanic with tropical rainforests, rugged mountainous landscapes, and limited freshwater. The climate is tropical and humid and defined by two distinct seasons, the cool dry season (April to October) and the hot wet season (November to March). The islands have abundant marine life, endemic birds, rare plants and various distinctive insects. Vanuatu has been classified by United Nations University (UNU) World Risk Index as one of the most at-risk countries in the world to climate change, which puts its unique biodiversity at risk. Butterflies are extremely diverse worldwide with approximately 20,000 species, they are regarded as environmental bioindicators meaning their absence or presence can reveal the state of environment. This is due to their short generation times and sensitivity to climate variables, and changes to both plant host availability and habitat.
Butterfly (Bataflae) Diversity within Vanuatu
The first organised effort to catalogue the butterfly species of Vanuatu using western science was in 1971 where the Royal Society/ Percy Sladen New Hebrides Expedition (RSE) surveyed 8 islands within Vanuatu. The butterflies were recorded by Gross (1975) who listed 63 species, of which 4 were endemic (only found in a specific region). Following this, in January to March 1983, Chris Salmon collected and imaged many butterflies in Efate. Much of the current information of butterflies of Vanuatu is due to the work of John Tennet from the Natural History Museum, London. John’s work has found that Vanuatu has at least 85 subspecies of butterflies that are known to occur within the many islands, from five different families; Hesperiidae, Papilionidae, Pieridae, Lycaenidae and Nymphalidae. Only two species, Polyura sacco and Deudorix mathewi and 26 subspecies are endemic to Vanuatu.
Tennet (2004) found some of the most widespread butterfly subspecies where Eurema hecabe sulphurata, Jamides bochus, Catopsilia pyranthe lactea, Lampides boeticus, Euchrysops cnejus cnidus, Zizula hylax dampierensis, Hypolimnas bolina nerina, and Junonia villida villida. Many of these subspecies were found to be abundant and widespread during Tennet’s 2000-2002 survey across Vanuatu. Tennet (2004) found a handful of butterfly species were only detected on a single island within Vanuatu including; Prosotas patriciae (Futuna), Delias nysa santo (Espiritu Santo), and Melanitis amabilis amabilis (Malakula). Tennet (2004) also found that larger islands such as Espiritu Santo, Malekula, Efate and Tanna had high butterfly diversity (subspecies). Whereas smaller islands such as Tegua, Toga, Reef Islands and Mere Lava had lower butterfly diversity (subspecies). This observation is likely due to increased habitat variation and plant diversity on larger islands. However, due to the low number of biodiversity surveys over multiple seasons and years the true abundance and distribution of these butterflies is unknown.
Within the Auckland War Memorial Museum entomological collection, we mainly hold Vanuatu butterflies which are common and widespread (Table 1). Naturalists that collected these butterflies from Vanuatu include; H. B. Broughton, Arthur Thomas Pyecroft and Ray Thomas Shannon.
The Role of Butterflies (Bataflae) in Ecosystems
Butterflies have many roles in ecosystems such as environmental bioindicators, pollinators and as key components of the food web. Butterflies facilitate cross pollination and thus genetic diversity within plants via pollination. Which is enhanced due to their ability to fly long distances therefore connecting plant populations. They have been found to be important in the pollination of certain plant species which display psychophily traits (flowers that have adapted to be pollinated by butterflies). Within Vanuatu psychophilous flowers exist such as Lantana and Pavetta species. However, due to the lack of formal scientific studies on the pollination of plants by butterflies in Vanuatu, little is known about their true role. Nevertheless, many common butterfly species present in Vanuatu are known to be important pollinators elsewhere including; Eurema hecabe in Bangladesh, Euploea leucostictos in Indonesia, and Hypolimnas bolina in the Philippines. In addition, butterflies/caterpillars are a vital food source for other species within the ecosystem including bats, reptiles, birds and other insects therefore playing a vital role in food webs. Due to the lack of ecological studies conducted on Vanuatu butterflies the true impact of their role in ecosystems is unknown but their decline is likely to have detrimental impacts.
Vulnerability of Butterflies (Bataflae) to Climate Change
Many studies have found butterfly populations to be declining worldwide including; Edwards et al. (2023) in the USA, Leuenberger et al. (2025) in midwestern USA, Habel at al. (2022) in central Europe and Kukkonen et al. (2022) who found a decline in the Apollo butterfly over 20 years in Finland. There are a multitude of possible negative changes that could arise from climate change on butterfly species, two fundamental ways are range shifts and asynchrony (mismatching). Butterfly distributions are likely to shift due to changes in climate variables such as temperature, humidity and rainfall and in turn host plant availability within these habitats. For alpine butterfly species their range under future climate predictions is likely to be reduced as habitats become unsuitable to them or their host plants as temperatures rise. Asynchrony is likely to happen between butterflies and their host plants; this could be due changes in environmental cues such as temperature, humidity or rainfall causing butterflies or plants to change their phenology (timing of emergence, different life stages, flowering times and mating). For example, increased temperatures might trigger early emergence of caterpillars which may no longer match their host plants optimal growth or development times. These changes are of particular concern for butterflies that are considered specialists (feed a single or on a handful of plant species), as they won’t have the flexibility of generalists (can feed on a wide variety of plant species) to switch to other more available hosts. In addition, early emergence of butterflies might lead to a mismatch between their emergence and flowering times of plants which could impact pollination.
Evidence suggests that butterflies are already being impacted by habitat change/loss and climate change. Many studies have also accessed the potential impacts of butterfly species to climate change through climatic modelling, which includes butterfly extinctions in the UK predicted as early as 2050. Some of these impacts might be able to be mitigated through increasing in suitable habitats and conservation efforts of host plants and butterflies. For butterflies of Vanuatu such impacts of climate change on the species present have not been studied, however, likely detrimental especially for more vulnerable species.
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