Ecology of Sulawesi. Tony Whitten
dawn until dusk one day in 1936 (Doctors van Leeuwen 1937). Such migrations of pierids are well documented in Europe and it has been found that these butterflies travel in more or less straight lines, searching for suitable habitats. By so doing, they avoid returning to a place that they have just left. They feed and breed in different habitats and so, for a chort of butterflies that emerged at more or less the same time, the best place to be is somewhere else. These butterflies sometimes seem to follow rivers but it is possible that they are simply more visible there because experiments have shown that they have a sense of direction rather than a sense of location (Baker 1982).
Endangered Species
The names and status of the world's rare and endangered animals are compiled and monitored respectively by the Conservation Monitoring Centre of the International Union for the Conservation of Nature (IUCN) and Natural Resources based in Cambridge, England. 'Red Data Books' are produced detailing what is known of the ecology and threats facing each of these species, and what conservation measures, if any, are currently in force to protect the animals. Examination of the Red Data Books reveals that 16 species are considered to be at risk of extinction19 on Sulawesi (table 1.13).
During the course of writing this book it has become clear that the above animals are by no means the animals most at risk and indeed some animals may have become extinct unnoticed.
The attractive Caerulean paradise-flycatcher Eutrichomyias rowleyi was discovered in 1873 by a hunter working for the German ornithologist A.B. Meyer (Meyer 1878). The label on the first specimen states that it was male but there was no verification of this (Meyer 1878), and in fact the colour is more typical of a female flycatcher than of a male (S.V. Nash pers. comm.).
That first specimen is in fact the only specimen ever collected of this distinctive bird. One may have been sighted in 1981 (White and Bruce 1986), but intensive ornithological surveys of Sangihe Island by experienced ornithologists in 1985 and 1986 failed to find any. Virtually all of Sangihe has been converted to coconut and nutmeg plantations or else is covered in patches of secondary forest from abandoned gardens. A small patch of montane forest exists on the top of Mt. Sahendaruman in the south of the island and it was felt that this was the only possible habitat for the species (Whitten et al. 1986). Surveys by Action Sampiri in 1998-99 revealed that this bird was clinging to survival in those forests but the numbers are extremely low.
The status of other animals endemic to Sangihe and the Talaud Islands, should now be an immediate cause for concern (see the Introduction). The blue-and-red lory Eos histrio (Sangihe and Talaud20), Sangihe hanging-parrot Loriculus catamene and Elegant sunbird Aethopyga duyvenbodei (Sangihe), and Talaud kingfisher Halcyon enigma have all been seen recently although none of them is at all common. It is possible that the blue-and-red lory is already extinct on Sangihe but it still appears to be common on Karakelang, the main Talaud Island (Whitten et al. in press). The black birdwing butterfly Troides dohertyi (forewing length 73 mm male, 82 mm female) is known only from Sangihe and the Talaud Islands where it lives in lowland forests in which the caterpillars probably feed on the leaves of Aristolochia tagala, a climbing shrub that grows in forests and thickets up to 800 m above sea-level (Ding Hou 1984; Collins and Morris 1985). This butterfly must be considered as being under considerable threat given the greatly reduced area of lowland forest on the islands, for it is not known whether it can adapt to secondary vegetation (Collins and Morris 1985). It is probably already extinct on Sangihe but there is a hunting reserve on Karakelang, which includes hill and mountain forests and efforts should be made to determine whether the birdwing is present. The boundaries of this reserve are under pressure from illegal farmers.
E - endangered, V - vulnerable, R - rare, I - insufficiently known.
After Miller 1977; Thornback 1978; King 1979; Groombridge 1982; Wells et al. 1983; Collins and Morris 1985
The endemic fish of lakes Poso and Lindu, and of lakes Towuti, Matano, Wawantoa and Mahalona (table 4.10) are threatened by the introduction of fish to increase fisheries production. Among the endemic species are four duck-billed fish-Adrianichthys kruyti, about 11 cm long from Lake Poso (fig. 1.24), Xenopoecilus poptae and X. oophorus, about 10-20 cm long, also from Lake Poso, and X. sarasinorum, about 7 cm long, from Lake Lindu. These species used to be thought to comprise the entire family Adrianichthyidae, but recent taxonomic analyses have now placed several more species in this family, some of which are also endemic to Sulawesi, and some of which are found from India to Japan (Rosen and Parenti 1981). There are early reports that X. poptae does not seem to lay eggs as most fishes do, but rather voids eggs which hatch on contact with water. The young fry then swim along with their mother. The broken egg membranes, known locally as momosonya21, rise to the lake surface and used to cover considerable areas of the lake (Weber and de Beaufort 1922). This has not been confirmed and the 'momoso' may be pollen or seeds. It is known that the newly discovered X. oophorus carries its eggs below its body until they hatch (Kottelate 1990) (see Introduction). Similar behaviour in X. poptae may have given rise to the other story.
Teams that visited Lake Poso in 1976 and 1983 both found the two endemic fish, but a survey of fishermen and an examination of fish catches in 1986 could not confirm the continued existence of either species. Some fishermen claimed that some fish had disappeared when Colo volcano erupted in 1983 (p. 7). This seems untenable as a reason since satellite photographs of the ash plume show how this was blown to the west rather than the south (Katili and Sudrajat 1984). At the start of the century it is said that great shoals of X. poptae formed at 12 -15 m between November and January, and were caught by fishermen using hooks (Weber and de Beaufort 1922).
A likely cause of the reduction in the populations of these endemic fish, and also the possible extinction of some of the snails and mussels endemic to Lakes Poso and Lindu (p. 297) (Carney et al. 1980) is the unthinking introduction of exotic fish species, particularly of the tilapia, carp and catfish, to increase fisheries production (Whitten et al. 1986). The extinction of fish species as a result of the uninformed introduction of commercial species has been reported from elsewhere, particularly the enormous lakes of the East African rift valley to which many species of cichlid fish are (were) endemic. Indeed, 60%-80% of the world's freshwater fisheries are based on introduced species. Not all fish introductions damage the indigenous fauna, however, and success stories have been reported from other African lakes. Major agencies now do not, as policy, advocate the introduction of new species of fish into lakes except with the most extreme caution. To avoid any possible extinction of endemic fish on Sulawesi, fisheries staff must first be aware that any introduction may result in the loss of endemic species, and second be able to justify their aims to all parties.
Figure 1.24. Adrianichthys kruyti, one of the three endemic duck-billed fish of Lake Poso.
BIOGEOGRAPHY
Background to Biogeography
Every organism has a spatial distribution related to its ecology, behaviour, physiology, ability to travel long distances, the other organisms living in the same area, and to the geological history and climate of the area in question. A further and important factor in determining distributions is chance. Conditions suitable for an organism in terms of light, humidity, food, etc. do not necessarily occur evenly over an area and this is reflected in that species' distribution. The study of such patterns and the factors causing or limiting them is known as biogeography.
The distribution of an organism is generally bounded by unsuitable habitats, unsuitable climates or the occurrence of a species against which it cannot compete successfully. Alternatively, a species may be actively dispersing and the edge of its range may simply be the furthest point it has reached at that time. Clearly a barrier for one species is not necessarily a barrier for another, and a barrier for one life-stage of an organism is not necessarily a barrier for a different life-stage of the same species. For example, the larvae of many invertebrates and the seeds of plants are much more mobile than the adults.
Distributions can be described on various levels: thus a bird might live in forest; but perhaps only in a few types of forest; at certain altitudes;