11 November 2010

Butterfly Re-Introduction - Boon or Bane?

Butterfly Re-Introduction Programme
Boon or Bane?

Clipper (Parthenos sylvia lilacinus) extinct in Singapore, but successfully bred and showcased in regional butterfly farms

Mention the word re-introduction to conservation ecologists or purist nature enthusiasts and you may get a bit more than just raised eyebrows - experience has shown that there have been passionate objections and heated arguments about this. There are, of course, valid causes for concern, but the other side of the argument also has pertinent points favouring re-introductions.

For those who may not be aware, re-introduction is the intentional and deliberate release of species back into the wild. These species are either bred, or captured and released from other areas where the species still exists. In various taxonomic groups, it usually involves species that are critically endangered or extinct in the wild. Technically, re-introduction usually involves the returning of species into locations or regions where they were previously found or recorded with a fair measure of confidence, but are now extinct. Hence some practitioners of re-introduction programmes prefer to call it "re-establishment".

Caterpillar of the Clipper (Parthenos sylvia lilacinus)

Re-introduction programmes have been more predominantly focused on mammals and vertebrates like birds and occasionally amphibians. There are some well-known programmes since the early 1980's where biologists have studied the impacts of re-introducing a species into the habitat it once existed in.

Smaller Wood Nymph (Ideopsis gaura perakana) - extinct in Singapore

For butterflies, any initiative to re-introduce species that have since gone extinct should take into account the following considerations :

  • Habitat and preferred localities that the butterfly can survive and thrive - those species which survive in the forested areas which are protected are more likely to be sustainable.
  • Larger and more robust species that are easier to be bred and withstand environmental pollution.
  • Availability of its caterpillar host plants and whether another extant species shares this host plant with the re-introduced species
  • Its early stages and whether the caterpillars may cause other species (even besides butterflies) to be affected by their presence.
  • Whether the intentional cultivation of the host plant may affect the floral ecological balance.
  • The correct subspecies must be ascertained.

There have been several successes of butterfly re-introduction programmes in the west, in particular, two examples being the Karner Blue (Lycaeides melissa samuelis) in Ohio, USA and the Large Blue (Phengaris arion) butterfly which was declared extinct in the UK in 1979, but has been successfully re-introduced.

Underside of the Leaf Butterfly (Kallima limborgii amplifura)

It is not known whether there have been any similar re-introduction programmes in SouthEast Asia, nor any research papers done to document if there have been any successes. Thus far, Internet searches have delivered only reports of butterfly re-introductions from western countries.

Leaf Butterfly (Kallima limborgii amplifura) extinct in Singapore but commonly bred at butterfly farms in the region

If such a re-introduction programme were to be carried out in Singapore, what would be the possible species that could be targeted? Should Singapore even consider a butterfly re-introduction programme?

Caterpillar of the Leaf Butterfly (Kallima limborgii amplifura)

From those checklists, a selection of e.g. 5-6 species could be done, and studies conducted on populations of these species where they still exist. The nearest populations of some of these species would be a mere hour's drive up north into the Malaysian state of Johor.

Wanderer (Pareronia valeria lutescens) male - extinct in Singapore, but seasonally common in forested areas in Johor

Once observations and reports are made of these species in their natural habitats and general behaviour and habits of the species, host plants, early stages and so on, the search for possibly similar habitats be made in Singapore, where the species could be re-introduced. One premise that should be established would be the availability of the caterpillar host plant in Singapore, its abundance, and extent of spread across the island. Care must be taken, of course, that the host plant is already native to the Singapore flora checklist and not to introduce an exotic species of plant to Singapore.

Wanderer (Pareronia valeria lutescens) female - extinct in Singapore, but seasonally common in forested areas in Johor

Prior to the re-introduction programme, the host plant must be cultivated, perhaps under the National Parks Board's supervision, at locations like Singapore's urban parks, gardens, park connectors and so on, where the cultivation of the plants can be supervised and observed.

Common Sergeant (Athyma perius perius) a common butterfly bred in butterfly farms in Malaysia

Once there is enough critical mass of the host plant (that is, assuming that the plant is not common in the first instance), then the import of pupae or wild-captured males and females of the target species is released into the wild. Unlike mammals, there is no need to 'train' the released butterflies to hunt or adapt to its new surroundings.

The Yellow Barred (Xanthotaenia busiris busiris) extinct in Singapore since the late 19th century

It has always been a subject of debate, whether human intervention is advisable where the survival of a species is concerned. They may have gone extinct for a good reason, and bringing them back into the environment may not necessarily be a good thing. However, one can always argue that a species has gone extinct, precisely because of human intervention in the first instance (like development, land clearing, removal of a plant species, pollution in the environment, and so on). Hence where humans have been the cause for the extirpation of a species, it would only be right that humans make amends to bring the species back.

The debate will not ever end, as there will always be proponents on both sides, extolling the pros and cons of whether to re-introduce a species, or not. As a supporter of butterfly re-introduction, I would personally recommend that further observations and studies continue to be carried out before a pilot scheme for a re-introduction be attempted.

Chocolate Tiger (Parantica melaneus sinopion) extinct in Singapore

Some suggested butterfly species that could be studied and considered for re-introduction in Singapore would be as follows :

  • Smaller Wood Nymph (Ideopsis gaura perakana)
  • Chocolate Tiger (Parantica melaneus sinopion)
  • Yellow Barred (Xanthotaenia busiris busiris)
  • Wanderer (Pareronia valeria lutescens)
  • Clipper (Parthenos sylvia lilacinus)
  • Common Sergeant (Athyma perius perius)
  • Leaf Butterfly (Kallima limborgii amplifura)

Text by Khew SK ; Photos by Bobby Mun, Khew SK & Anthony Wong

Further Reading & References :