CONSERVATION
IUCN Redlist category Near Threatened (IUCN 2020)
Rationale for redlist categorization Trogonoptera trojana has been assessed as Near Threatened. This species has a relatively restricted extent of occurrence, being confined to the island of Palawan, Philippines, and a few surrounding islands. It is likely to have gone extinct or to be very rare on the island of Balabac. Its current extent of occurrence is just in excess of 20,000 km?. Its area of occupancy, based on scarce locality records, is only 16 km?. While the species is part of the butterfly trade, the main threat is likely widespread habitat loss across Palawan. However, lack of distribution data for this species is making the assessment difficult. More information is needed to allow assessment of how many locations the species occurs in and the impact of forest loss on the species. At present, a listing of Near Threatened is possible due to its likely restricted area of occupancy and the fact that habitat is in decline, with an estimated 6% of Palawan forest lost in just over a decade. Given the potential impact of habitat loss and the 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 (IUCN 2020)
Cause of stress Intentional use (species is the target),Unintentional effects: (large scale) [harvest] (IUCN 2020)
Described Threats The 1985 IUCN Red List assessment for the species stated that this species, particularly males, are collected in great numbers, especially from the rain forests of northern Palawan (Collins and Morris 1985). The species is listed on CITES Appendix II together with the genera Ornithoptera and Troides , with the exception of O. alexandrae which is listed on Appendix I. Recently traded individuals appear to come to a large degree from ranched populations (CITES 2015). Butterfly ranching is generally thought of as a sound, economically viable and sustainable rural industry (Wambi 1996, Hanscom 1993, Burrows 2003 in Small 2007). However, there are concerns that butterfly ranching may not be as sustainable in some countries as it is often perceived to be (e.g., Papua New Guinea; Small 2007). This is based on a lack of data and species monitoring to assess the status of butterfly populations, and for many species, such monitoring is fraught with difficulty due to inaccessibility of their habitat (Small 2007). 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. It has been stated that overcollecting seldom becomes a threat to butterflies, due to the reproductive capacity of insects and the difficulty in capturing significant numbers of the population (Pyle and Hughes 1978, in Parsons 1992). However, where birdwing butterflies are highly specific to host plants and where density of these hosts plants limits population size, collection in conjunction with habitat loss could have significant impacts on the species or subpopulations. The vast majority of the Philippine exports of this species since 2000, however, were declared as captive-bred individuals (CITES Trade database 2016).
The biggest threat is likely to be forest loss from timber production (Collins and Morris 1985). Current data suggests large areas of forest loss within the species' range, especially over the most recent years (Hansen et al. 2013), with just over 6% of forest estimated to have been lost in just over a decade (Panela 2014). (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). This species is traded especially for the decorative trade, with reportedly large numbers being taken, especially males (Collins and Morris 1985). This species is listed on Appendix II of CITES. Recent data from the CITES Trade database show, however, that since 2000 and present around fewer than 200 wild or ranched specimen were exported from the Philippines, versus nearly 7,000 captive-bred specimen being exported over the same period (CITES 2015). This is in agreement with previous trends from the country between 1987 and 2005, where captive individuals were the most common source of traded individuals (UNEP-WCMC 2007). (IUCN 2020)
Applied conservation actions The species was not considered to be threatened in an IUCN Red List assessment in 1985 (Collins and Norris 1985). This species, together with its congeneric T. brookiana and all species of the genera Ornithoptera and Troides , is listed on CITES Appendix II (with the exception of O. alexandrae which is an Appendix I species; CITES 2008); this means that trade in these species is controlled in order to avoid utilization which may be incompatible with the species' survival. Given the potential impact of habitat loss and the 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)
REFERENCES
- CITES. 2008. Appendices I, II and II. (Accessed: 23 September 2008).
- 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.
- Hanscom, T. 1993. Setting hearts aflutter: little butterflies take wing as big business. The Rotarian 163: 16-19.
- 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.
- 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).
- Panela, S. 2014. ‘Too many people’: Philippine island being deforested despite extensive protections. Available at: https://news.mongabay.com/2014/10/too-many-people-philippine-island-being-deforested-despite-extensive-protections/. (Accessed: 7th November).
- Parsons, M.J. 1992. The butterfly farming and trading industry in the Indo-Australian region and its role in tropical forest conservation. Tropical Lepidoptera 3(Suppl. 1): 1-31.
- Pyle, R.M. and Hughes, S.A. 1978. Conservation and Utilization of the Insect Resources of Papua New Guinea. Wildlife Branch, Department of Natural Resources, Port Moresby.
- Small, R.D.S. 2007. Becoming unsustainable? Recent trends in the formal sector of insect trading in Papua New Guinea. Oryx 41(3): 386-389.
- UNEP-WCMC. 2007. Review of trade in ranched birdwing butterflies. UNEP-WCMC, Cambridge.
- Wambi, D. 1996. Birds, bugs and butterflies. New Guinea Insight 6: 5-9.