Biswajit Fahroun Guha

Fragile Forest is a project undertaken by the Singapore Zoological Gardens to showcase invertebrates in settings similar to the natural ecosystems. Originally intended as an exclusively invertebrate exhibit, Fragile Forest has metamorphosed into an ecological experience bringing together plants and animals; both vertebrates and invertebrates, with a major emphasis on the latter. Some of the main ecosystems showcased include tropical rainforest, coral reef as well as mangrove habitats. With the setting up of Fragile Forest, it is hoped that guests will have an increased awareness and appreciation of the remarkably diverse and delicate relationships existing in an ecosystem.

INTRODUCTION

The idea of setting up an invertebrate exhibit at the Singapore Zoological Gardens was suggested several times, but was only given serious consideration some time in the early part of the nineties. Having already acquired a considerable representation of the vertebrate fauna, it was felt that invertebrates be showcased and added to the zoo’s collection, to better illustrate the diversity of animal life on this planet. At Fragile Forest, inter-relationships between plants and animals, both vertebrates and invertebrates, are highlighted to zoo guests. Invertebrates are of course still the main focus of the exhibit, but now their abundance and importance in the environment and ecosystem are accentuated and imparted to guests.

Although called Fragile Forest, the exhibit will also feature, other than a tropical rainforest; mangrove, coral reef and riparian ecosystems. From the outset it was decided that there be no specific zoogeographic region designated, as taken from a purist’s viewpoint, plants chosen would also be limited to that particular region, a task fraught with a great deal of complexity since much exotic foreign flora had already been permanently established locally.

Fragile Forest occupies an area of approximately 0.4 hectares (about 1 acre); this includes breeding and rearing complexes, caterpillar foodplant plots as well as the exhibit proper. There is a nursery off-site which maintains and propagates the bulk of caterpillar foodplant required.

There are four permanent staff managing the husbandry and maintenance at Fragile Forest. Butterflies will feature prominently in the exhibit, and as such, intensive lepidoptera breeding is carried out. It is the ultimate goal to produce all future display specimens as opposed to purchasing from an external source. For the initial two years at least, about 50 to 70% of the display stock would be purchased from external suppliers.

Service and Breeding Facilities

The service and support facilities comprise three separate buildings; the Service Block, the Caterpillar Rearing Room (CRR) and the Butterfly Flight cage (BFC). There is also an adjacent area used as a transient nursery, as well as a caterpillar foodplant cultivation plot.

Service Block: The Service Block contains two breeding rooms, a kitchen, an office, a quarantine area as well as a leaf-washing bay. The breeding rooms are equipped with breeding-boxes, measuring 40 cm x 40 cm x 60 cm, which are suitable for rearing caterpillars. There are also facilities for cricket as well as mealworm breeding and free standing boxes to house phasmids. All windows and doors in the rooms of the service block are fitted with 2mm stainless steel mesh. Commercially available plastic tanks are used to house most of the other invertebrates, including scorpions, tarantulas and beetles.

Caterpillar Rearing Room: The Caterpillar Rearing Room (CRR) adjoins the Service Block and when completed will be used for the rearing of caterpillars on life potted plants. Currently caterpillars are being maintained in the Service Block but lack of space as well as the requirement of some caterpillars for sunlight has prompted the need for the above-mentioned room.

The CRR will be fabricated of a 5 cm welded mesh support covered by two layers of fine mesh; 2 mm nylon meshing on the outside and 2 mm stainless steel meshing on the inside. Meshing is attached to the top as well as all four sides of the room. Roofing consists of clear corrugated Perspex that allows the passage of sunlight but prevents rain from entering. The double meshing allows air circulation and prevents excessive entry of rain from the sides.

To facilitate efficient maintenance of the caterpillars, the CRR is also situated beside the plant holding nursery for convenient and easy collection, as well as preparation of potted foodplant prior to being fed to the caterpillars.

Butterfly Flight Cage: The Butterfly Flight Cage (BFC) is used as an egg-collection area for butterflies currently being bred, as well as those to be acquired from external suppliers. The facility consists of an aluminium and iron support onto which 2mm stainless steel meshing is attached on the top as well as all four sides. Half the roof is covered by clear corrugated Perspex while the other half is uncovered. Life potted plants as well as flowering plants are placed inside the cage and appropriate caterpillar foodplants are also added for egg-collection.

All the facilities in the service and support areas have been modified in various ways to deal with pests and parasites. The use of 2mm stainless steel mesh is necessary for the above-mentioned facilities because it keeps out several different species of parasitic wasps and flies, which oviposit in the egg, larva or pupa of the butterfly. Having separate and discrete buildings for the different stages of the lepidopteran life-cycle also reduces infestation.

The mesh is attached under supporting beams and trusses so that no cracks, joints and crevices are inside the facility. This eliminates hiding and breeding areas for the geckoes that prey on, and can easily decimate a captive population of butterflies, given the opportunity. Stainless steel meshing is extremely resistant to attacks by rodents which also predate extensively on larvae, pupae and adult butterflies.

The last modification, and by far one of the most important, is the addition of a water barrier along the inner perimeter of all the aforementioned facilities. The water-barrier, in actual fact an open drain, with a capped outlet, prevents the entry of ants which aggressively predate on all the butterfly’s four stages. The water-barrier has been extremely effective in keeping ants out of all the service rooms but diligence is required to ensure that nothing falls across the water-barrier, thus allowing the passage of ants.

Current Invertebrate collection

The list of invertebrates presently being bred or maintained at Fragile Forest can be found in the attached appendix. Although the non-lepidopteran specimens far outnumber the butterflies, a large proportion of daily maintenance is actually devoted to caterpillar rearing and butterfly husbandry.

Butterfly breeding and management

Butterflies Bred at Fragile Forest: Foodplant availability is the determining factor in the continuity of butterfly culture. Hence we are initially concentrating on about seven species for which sufficient foodplant has been propagated. These are Idea leuconoe (tree nymph), Papilio memnon (great mormon), Pachliopta aristolochiae (common rose), Troides helena (common birdwing), Hypolimnas bolina (great eggfly), Danaus genutia (common tiger), and the Cethosia hypsea (Malay lacewing). Breeding and husbandry techniques are described below, but it should be noted that there are differences in the methods used for the individual species.

Egg Collection: The initial stages of butterfly breeding takes place in the BFC. A known ratio of males and females of each available species is placed in the BFC and are allowed to mate naturally. Foodplant, either cuttings or potted plants, are placed in the BFC and once sufficient eggs have been laid, the plants are brought into the breeding room and allowed to hatch. Butterflies are given 10% honey solution placed in feeders with different coloured discs. Flowering plants are also present as a nectar source.

Caterpillar Rearing: Upon hatching, the larvae are maintained in one of two ways, depending on the species concerned. The first method of maintenance involves feeding the caterpillars with foodplant cuttings in the breeding boxes. The cuttings are disinfected and placed in bottles, prior to being fed to the larvae. Misting with water is carried out daily, as is removal of frass and replenishment of leaves. The caterpillars are allowed to pupate naturally within the boxes and misted daily until eclosion. This method is rather labour intensive and plants from which cuttings are made, take a longer time to generate new foliage.

The second method utilizes potted plants, although this is more suitable for species in which caterpillars do not wander excessively. The eggs are allowed to hatch on the plant and caterpillars left to feed upon the leaves until almost defoliated. More potted plants are placed adjacent to the denuded plants and the larvae allowed to transfer naturally. Once the larvae are observed to be in the final instar, they are transferred to boxes in the breeding room and allowed to pupate inside.

Eclosion: The pupae within the boxes are misted daily and any butterflies emerging are collected and put either into the BFC or released into the exhibit. The breeding cycles are continuously maintained thus ensuring the availability of butterflies throughout the year.

Exhibit Layout

The exhibit is made up of a series of four connecting centres leading into a walk-through Flight Cage situated on the side of a hill, with some 6 metres in height difference. Displays in each centre focus on different themes pertaining to the aims of Fragile Forest.

Ecosystems: The first centre concentrates on the concept of ecosystems, and the interdependence of plants, invertebrates and vertebrates. This also showcases the diversity as well as abundance of invertebrate life present in the world. In this centre, guests are able to see representations of a riparian ecosystem comprising aquatic insects and tadpoles. The invertebrates on display include water-scorpions, water-beetles, pond-skaters and giant water-bugs.

A tank display of corals, sea-anemones, urchins, starfish and some crustaceans and molluscs complete the coral-reef ecosystem. Another marine tank depicts part of a sea-grass habitat complete with sea-horses and pipe-fish.

A section of the centre depicts a tropical forest setting with invertebrates found in various stratas of the ecosystem. On the forest floor are found foraging Temenggong ants (Camponotus gigas), as well as dead leaf mantises (Deroplatys sp), and rhinoceros beetles (Chalcosoma atlas) mating and feeding on fallen rotting fruits. Scorpions, tarantulas and Madagascan hissing cockroaches hide in rotting trees and crevices. The subterranean system includes developing rhino beetle larvae and the underground tunnel system of the Temenggong ants. Burrowing tarantulas are also featured in this habitat.

The ecosystem theme is continued in the second centre which has a mangrove swamp set-up that can be viewed through glass panels. The mangrove swamp ecosystem comprises an island planted with both real as well as artificial mangrove trees. It is surrounded by brackish water in which archer fish, horseshoe crabs, and several species of crustaceans are maintained. The island contains mud, the main medium in mangrove swamps, and it is in this, that mudskippers as well as the crabs burrow and live. A colony of weaver ants (Oecophylla smaragdina) can also be found on the mangrove trees on the island.

Rainforest Products: In this centre guests will enter a mock-up of a native hut, surrounded by forest trees, both life and fake; of economic importance. Here, they will find out about forest organisms that provide us with materials we so often take for granted such as rubber, rattan, timber, beeswax and honey, and even medicinal products. The message of why it is essential for us to conserve our existing forests, and also other ecosystems can be emphasized. It will be an interactive display whereby guests will be able to feel and smell the products. Methods of obtaining these materials can also be demonstrated; for example the tapping of rubber trees and the collecting as well as processing of the latex.

Survival Tactics: The final centre demonstrates the various techniques employed by forest animals in their struggle for survival. Camouflage or cryptic colouration will be demonstrated by exhibiting phasmids like the Queensland Titan (Acrophylla wuelfingi), giant prickly stick (Extatosoma tiaratum) and the Gray’s twig (Lonchodes brevipes).

Aposematic otherwise known as warning colouration, will be represented by different species of poison arrow frogs (Dendrobates sp) and also various brightly coloured caterpillars, which are known to be distasteful to predators.

Locusts will also be displayed here to give an example of invertebrates which use extremely favourable conditions to increase their population tremendously, so as to survive through periods which are less favourable. It should be noted that graphics play a major role in all these centres both for the purpose of education as well as aesthetics.

Flight Area: The four centres provide entry and exit points for the Flight Area which measures 60 m x 25 m. It is covered by an oval dome made up of 4 mm stainless steel mesh supported by two main arches. The dome attains a maximum height of about 12 metres. This allows the presence of tall trees inside to further enhance the tropical rainforest setting.

There are two observation decks, as well as rain shelters into which exhibits will be incorporated to display different species of caterpillars and the corresponding pupae formed. Butterflies are allowed to fly free within the Flight Area and an approximate number of 3000 specimens are expected to be on display at any one time. In addition to the species already being bred at Fragile Forest, about 12 other species will be purchased from external suppliers in Malaysia, Australia and Costa Rica.

The species that will be imported include:

A boardwalk winds across the Flight Area, and other invertebrates like robber-crabs (Birgus latro), phasmids, as well as Atlas moth (Attacus atlas) caterpillars might be exhibited at strategic locations, either on islands or in hollowed out habitats. An artificial log containing display tanks for invertebrates has also been included in the Flight Area. This log will have little doors which guests can lift to view the invertebrates displayed inside.

Planting within the Flight Area includes flowering plants as well as caterpillar foodplants. These will be positioned near the path to attract butterflies, hence allowing closer proximity as well as a better view of the specimens. Artificial feeders will also be placed in areas allowing guests a better view. The area will be planted so as to represent a forest fringe as well as dense forest, to accommodate the different requirements and habitats of butterflies kept within.

A cascading stream runs through the Flight Area, and a carnivorous plant exhibit has been proposed near the banks. The idea of setting up an island along the stream, thus providing an effective barrier for an insectivorous primate has also been suggested.

Vertebrates that will be kept within the Flight Area include several species of pigeons, hanging parrots, partridges, quails, weaver birds, mousedeer, sloths, tamarins, tree kangaroos, fruit bats and other herbivores.

Guests will thus be able to experience first hand the way an ecosystem works from this basic and much modified model. It should of course be noted that the Flight Area is not a true ecosystem but merely a representation, as there has been an obvious effort to leave out carnivores as well as insectivores, which would otherwise jeopardize the whole exhibit.

Conclusion

Fragile Forest is the first exhibit in Singapore Zoological Gardens to bring together both vertebrates as well as invertebrates in as natural a setting as possible. With the opening of this exhibit, it is hoped that guests will realize the importance invertebrates play in our lives and not merely dismiss them as a useless nuisance. It is hoped that Fragile Forest will be more than just a showcase of interesting "creepy-crawlies", and instead educate and increase people’s understanding of the fragility of all the planet’s ecosystems. The information and experience imparted to guests should be an encouragement towards awareness and possibly active participation in conservation of the world’s habitats.

Acknowledgements

I would like to thank the management of the Singapore Zoological Gardens for allowing me the opportunity of attending this conference. I would also like to thank Cham Tud Yinn for the use of his drawings, and finally my colleagues Pauline Tan, Rubiah Ismail and Leon Boyd for helping me in one way or another during this period.