CONSERVATION
IUCN Redlist category Least Concern (IUCN 2020)
Rationale for redlist categorization Troides magellanus has been assessed as Least Concern. The species has a wide extent of occurrence of at least 453,930 km?, occurring from the Philippines to Taiwan. Despite incongruous statements over time on the population status of the species, it is likely to be relatively common in the Philippines. However, there are declines noted in the northern limit of its range (Orchid Island, Taiwan) where the species is listed as endangered nationally. The species occurs in forest habitats so that deforestation is likely to have an impact on the species in parts of its range. However, the species occurs in a large number of locations (it is widely distributed across a large number of islands), thus lowering the risk from these threats across its range. Given that we have limited quantitative information available for this species, monitoring and evaluation of population status would vastly improve our knowledge of this species and our ability to address any population declines where they may occur. (IUCN 2020)
Threat category Ecosystem conversion|Ecosystem degradation,Species mortality,Ecosystem degradation (IUCN 2020)
Cause of stress Intentional use (species is the target),Roads & railroads (IUCN 2020)
Described Threats Specifically, reduction in the foodplant Aristolochia zollingeriana due to deforestation, animal grazing and road building has been blamed for the dramatic declines in the population on Orchid Island, Taiwan (Yang and Fang 2002). Previously, overcollection was considered a primary threat on the island, leading to the listing of the species by the Taiwanese government as endangered in 1978 (Hu 2008), peaking at around 5,000-10,000 butterflies of this species being sent to Taiwanese factories (Hu 2007 in Hu 2008). Deforestation within the species range is likely to present a localised threat to the species. Latest data from the Global Forest Watch suggests that tree cover loss was highest on Mindanao and Leyte since 2001 (Hansen et al. 2013); given that the species occurs at relatively low altitudes where land clearing is more likely to occur, this is likely to have had an impact on it in parts of its range. (IUCN 2020)
Commercial use Butterflies are mostly traded dead for the curio market (Collins and Morris 1985, New and Collins 1991). Between 1998 to 2007, 306,000 butterflies were traded from Southeast Asia, with 13,000 of these being wild-caught (Nijman 2010). There is a distinct shift towards ranched and captive-bred individuals in trade from 2003 onwards; in 1985, it was reported that globally less than 10% of trade was in ranched individuals (Collins and Morris 1985). Altogether at least 34 different species were recorded in trade, most of which belonged to the birdwing butterflies ( Troides and Ornithoptera ; Nijman 2010). It should be noted that trade in butterflies may be underreported, because of difficulties monitoring. New and Collins (1991) noted that trade is extremely difficult to monitor because transportation of unpinned specimens is easy, especially of comparatively low value species which may instead be traded at high volumes. Birdwings can fetch high prices on the market. For example, butterfly collectors have paid high prices for birdwing butterflies of this genus: a pair of Ornithoptera meridionalis was reported to have fetched USD 3,400 in Germany (Melisch and Schutz 2000). Reported prices for Troides are however much lower. For example, a more recent pricing was around $85 per pair of T. hypolitus , around $15 per individual of T. helena and between $43 and $85 per pair of T. haliphron (Putri 2016). This species is listed on Appendix II of CITES. In terms of trade in birdwing species from the Philippines, Troides rhadamantus is the most traded, representing more than 80% of birdwing trade from the Philippines (UNEP-WCMC 2007). However, Trogonoptera trojana and Troides magellanus are also traded in significant amounts from the country (UNEP-WCMC 2007). Recent data from the CITES Trade database show, that since 2000 and 2015 around 3,500 individuals were exported from the Philippines (none from Taiwan; CITES 2015). More than 90% of these come from captive populations (CITES 2015). (IUCN 2020)
Applied conservation actions In a status assessment of the world's swallowtail butterflies in 1985, this species was not considered to be threatened (Collins and Morris 1985). In 1991, New and Collins suggested a need for provision of protected habitat for key species of Philippines endemic swallowtails (1991), primarily for those species which were identified as threatened at the time - however, any such work is likely to have benefited other species too, including this species of birdwing butterfly. The species is listed as Endangered in Taiwan (Huang and Cheng 2011). Planting of food plants on Orchid Island is part of a plan to stem the declines in the Taiwanese population of this species; between 1994-1997, 400 vines were transplanted to the island (Yang and Fang 2002), although survival was low (30%) due to continuing threats to the vines from overgrazing by sheep, drought, but most significantly due to the way in which the larvae feed on the vines. More mature vines are less or not affected by the ring cutting of larvae, so that housing was provided to ensure vines grow unhindered by the larvae to a robust age (Yang and Fang 2002). Conservation projects on Lanyu have since continued, estimating the carrying capacity of this species on the island and carrying out mark-recapture studies (Yang and Lang 2002). Analysis of the distribution and habitat requirements of the species' food plant Aristolochia zollingeriana has led to the proposal of reserve areas for the species (Yang and Fang 2006). Traditional ecological knowledge has also been used to inform conservation, with local communities involved in wider conservation of the species on Lanyu Island (Hu 2008). (IUCN 2020)
REFERENCES
- CITES. 2015. CITES Trade Data Base. Available at: http://trade.cites.org/.
- Collins, N.M. and Morris, M.G. 1985. Threatened Swallowtail Butterflies of the World. The IUCN Red Data Book. IUCN, Gland and Cambridge.
- Hansen, M.C., Potapov, P.V., Moore, R., Hancher, M., Turubanova, S.A., Tyukavina, A., Thau, D., Stehman, S.V., Goetz, S.J., Loveland, T.R., Kommareddy, A,. Egorov, A., Chini, L., Justice, C.O. and Townshend, J.R.G. 2013. High-resolution global maps of 21st-century forest cover change. Science 342: 850-853.
- Hu, C. 2007. The Articulation of Modern Fetishisms and Indigenous Species. Taiwan Journal of Anthropology 5(1): 19-62.
- Hu, J. 2008. “Spirits Fly Slow” (pahapahad no anito) : Traditional Ecological Knowledge and Cultural Revivalism in Lan-Yu. Journal of Archaeology and Anthropology 69: 45-107.
- IUCN. 2020. The IUCN Red List of Threatened Species. Version 2020-3. Available at: www.iucnredlist.org. (Accessed: 10 December 2020).
- Melisch, R. and Schutz, P. 2000. Butterflies and beetles in Germany. Traffic Bulletin 18: 91-93.
- New, T.R. and Collins, N.M. 1991. Swallowtail butterflies: an action plan for their conservation. International Union for Conservation of Nature and Natural Resources/Species Survival Commission Lepidoptera Specialist Group, Gland, Switzerland.
- Nijman, V. 2010. An overview of international wildlife trade from Southeast Asia. Biodiversity and Conservation 19(1101-1114).
- Putri, I.A.S.L.P. 2016. Handicraft of butterflies and moths (Insecta: Lepidoptera) in Bantimurung Nature Recreation Park and its implications on conservation. Biodiversitas 17(2): 823-831.
- UNEP-WCMC. 2007. Review of trade in ranched birdwing butterflies. UNEP-WCMC, Cambridge.
- Yang, Y.-L. and Fang, H.-S. 2002. The conservation status of birdwing butterflies in Taiwan. In: Sands, D. and Scott, S. (eds), Conservation of birdwing butterflies, pp. 30-31. SciComEd Pty Ltd & THECA, Marsden.
- Yang, Y.-L. and Fang, H.-S. 2006. Habitat Conditions for the Food-plant Vine Aristolochia zollingeriana of the Pear-light Birdwing Butterfly on the Lanyu Island. Endemic Species Research 8(1): 27-34.