P6 [XI L5 41 [XI L7 L8 45 44 iXI [XI Vegetation plots "-J m Marsh r Buildings a Beach 100 metres Figure 1. Cousin Island: physical, with locations of vegetation plots. COUSIN MICHAEL J. HILL', TERENCE M. VEL', KATHRYN J. HOLM^, STEVEN J. PARR~ and NIRMAL J. SHAH' GEOLOGY, TOPOGRAPHY AND CLIMATE Cousin is one of the smaller islands of the granitic Seychelles with an area of only about 29 ha. It lies about 2 km from Praslin, the second largest of the central Seychelles islands, and 2.1 km north east of the slightly smaller island of Cousine. The island is dominated by its plateau (Table l), a flat coastal plain made up of phosphatic sandstones. This rock was formed by the action of seabird guano on loose deposits, largely of marine origin, in the presence of Pisonia litter (Fosberg, 1984). The southern part of the island consists of a granite hill which reaches 58 m. The granite of the hill is similar in quality to that of Praslin Island (Braithwaite, 1984). Along Anse Frkgate in the south, there is a conspicuous line of fossil beach-rock (Fosberg, 1970). A granite outcrop, Roche Cannon, of similar granite to the hill, is connected to the north west corner of the island by a natural causeway. The plateau rocks support a thin layer of soil. Fosberg (1984) describes the plateau deposits as a beheaded Jemo soil, except around the marshes where deeper alluvial deposits have accumulated. These deeper soils were used for crop cultivation, and small numbers of fruit trees survive at the base of the hill. Cousin's beaches surround the island and their sand is highly mobile, shifting between beaches on the east and west sides of the island with the two main seasons of the Seychelles (Frazier and Polunin, 1973). Standing fresh water on the island is limited in extent and seasonal. On the plateau at the northern base of the hill there are several freshwater pools. To the south of the hill is a regularly inundated area of land colonised by mangroves. There are several small seasonal streams. The Seychelles islands experience a seasonal humid tropical climate (Walsh, 1984). Historical weather data for Cousin Island are limited and current data are unavailable. A summary of data on rainfall for the period 1970-75 is shown in Table 2. ' Nature Seychelles, PO Box 13 10, MahC, Seychelles. Email: birdlife@seychelles.net 1991 Casa Marcia Crescent, Victoria, British Colombia, Canada. Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK. Table 1. Area of Cousin Island by altitude (calculated from maps published by Directorate of Overseas Survey (UK)/Seychelles Government). Altitude range (m. a d . ) Area (ha) Percentage total area 50 - 100 0.6 2.1 10 - 50 5.5 19.2 0 - 10 22.5 78.7 Table 2. Cousin Island. Mean monthly rainfall (mm), 1970-1975 (from Shah et al. 1999). Jan Feb M a r Apr May Jun Jul Aug Sep Oct Nov Dec Total 232 141 143 110 56 30 41 100 112 205 139 310 1619 HISTORY The island was briefly mentioned by Malavois (1787) who described it as wooded with difficult access (in Fauvel, 1909). In 1821, when the island was surveyed by the Mauritian Government surveyor, i t was divided into three sections owned by freed slaves (Diamond, 1975). In the nineteenth and early twentieth centuries, the island had a succession of private owners. At this time mixed agriculture was probably practised and the natural resources of the predator-free island (turtles, seabirds and their eggs) exploited. Coconut plantations were begun on Cousin around 1910. Within 10 years, the natural vegetation of the plateau had been completely replaced by coconuts (den Boer and Geelhoed, 1990). The island was managed for copra production until 1967 when it was purchased by the International Council for Bird Preservation (now BirdLife International) and subsequently managed as a nature reserve, largely to protect the Seychelles warbler Acrocephalus sechellensis, which was then known only from Cousin (Komdeur, 1988). Management from this time allowed the regeneration of semi-natural vegetation dominated by Pisonia grandis (Phillips, 1984). The island was designated a Nature Reserve by the Seychelles Government in 1968, and was designated a Special Reserve in 1969. The Special Reserve designation includes the sublittoral zone to 400 m beyond the high-water mark (Shah et al. 1999). FLORA AND VEGETATION Flora Ninety-five plant species were recorded on Cousin Island, including three ferns and 92 angiosperms. Of the angiosperms, 47 (51 .I%) species are regarded as introduced (Friedmann, 1994) and 32 (34.8%) native. Only one of these native species (Pandanus balfourii) is endemic to the Seychelles although the list also contains an endemic subspecies (Ficus rejlexa ssp. seychellensis). The flora of Cousin Island has a similar proportion of introduced species and a smaller number of endemics than the flora of Seychelles as a whole (of the total Seychelles flora, around 54% are introduced and 9% endemic: Procter, 1984). The small number of endemic taxa probably reflects the island's size; in general, smaller islands in the archipelago have fewer endemic species (Procter, 1984). Of the introduced plants established on Cousin Island, a small number can be regarded as invasive weed species (Carlstrom, 1996a; Fleischmann, 1997). Of these, three are woody plants: casuarina Casuarina equisetifolia (frequent in beach crest vegetation; possibly native), papaya Carica papaya (abundant in plateau woodland) and agati Adeizuizthei-LI pnlxvziizu (occasionai in plateau woodland). Other potentially invasive species are the herbs pineapple Ananas comosus and fatak grass P ~ m i c ~ m i xi~nuin. Both species currently have a limited distribution on the island. The Rangoon creeper Quisqualis i~zdica occurs at one point near the marsh. It has the potential to dominate large areas through vegetative propagation. Several previous workers have produced plant species lists for Cousin Island, most notably Fosberg (1970, 1984). Fosberg recorded 132 species, many of which are still present on the island. Further surveys were carried out by Bathe and Bathe (1982) and Schumacher and Wuthrich (2000). In total, 54 species were identified in previous surveys but not in the current survey (Appendix 1). At least three of these previously recorded taxa are synonyms of other species on the list, and three may never have been present on the island. Many more (especially species of cultivation) are probably now extinct, or are occasionally cultivated. Some species were undoubtedly overIooked; a long-term survey of 1999 recorded 10 species not recorded by this survey (Schumacher and Wuthrich, 2000). If these, and species listed by previous authors which may survive (17 species: mainly herbs and grasses which may have been overlooked) are included, the total current plant species list for Cousin is 122. Vegetation The extents of major vegetation types on Cousin Island are shown in Table 3, and on Map 2. While most of the island was formerly coconut plantation, the plateau and part of the hill is now dominated by native woodland. The hill also has native scrub and large areas of bare rock. In total, 40 vegetation plots were completed, 20 in June and 20 in December, covering 4,000 m2 or 1.4% of the island's surface. Twenty vegetation plots were in plateau woodland covering 2,000 m2 or 1.1% of this habitat type, and 20 were in hill woodland/scrub (excluding areas of bare rock), covering 2,000 m2 or 4.7% of this habitat type. A summary of results is shown in Table 4. Hill woodland plots had a relatively low density of trees with sparse shrub and herb layers. The most abundant tree was the native Pisonia grandis (Table 5). Introduced trees made up only a small proportion of the total tree layer (only one or two species, around three percent of stems). The shrub layer of hill plots was species-poor, with only eight species represented, seven of which were native. The most widespread species was Euphorbia pyrifalia (Table 6). Coconut Cocos nucifera was only present in one plot, although in that plot i t constituted 38% cover in the herb layer. The herb layer of hill plots had fewer species than plateau plots: only 18 species were recorded, four of them introduced. The only species occurring in more than 10 plots was the fern Nephrolepis ?biserrata, in 17 plots (with a mean coverage of 29.6% in these plots). Plateau woodland plots had a high density of trees, relatively dense shrub layer, and sparse herb layer. The tree layer was more species-rich than that of hill woodland and included several species not present on the hill. Pisonia grandis was again dominant, but introduced species were more prominent due to the abundance of introduced papaya, absent on the hill. The shrub layer of plateau plots was more species-rich than that of hill plots with 15 species represented (three of them introduced). The most widespread species, and that forming the largest part of shrub cover in the plots where it occurred, was Pisonia gmizdis. Cocos nucifera, Morinda citrifolia and Ochrosia oppositifolia were also widespread in the plateau shrub layer. The herb layer of plateau plots was also species-rich with 20 species, seven or eight of which were introduced. Five species occurred in 10 or more plots: the most widespread and abundant were the liana Canavalia catlzartica (in 15 plots, mean cover 14.8%) and the fern Neplzrolepis ?biserrata (in 15 plots, mean cover 13.7%). Morinda citrifolia occurred in 12 plots (mean cover I%), Carica papaya in 11 (mean cover I%), and Pisonia grandis 10 (mean cover 4.7%). Table 3. Extent of major vegetation types, Cousin Island. Vegetation type Hill Woodland (Pisoilia gt-andis dominant) (> 10 m asl) Woodland (figs, other native spp.) Scrub (native) Bare rock Plateau Woodland (Pisotlia grandis dominant) (< 10 m asl) Woodland (other native spp.) Scrub (native) Coconuts Freshwater marsh Mangrove Beach crest vegetation (including Casuarina) Bare rock Grasslandlgarden Area (ha) 1.5 0.4 2.4 1.1 17.2 0.7 0.1 0.1 0.2 0.8 1.9 1.5 Table 4. Vegetation plot summary. Habitat Plateau woodland Hill woodland Plots Mean Mean Mean shrub Mean herb Open leaf Bare Dead wood altitude trees layer cover layer cover litter rock (pieces per (m asl) ha-' (%) (%) cover (%) (%) plot) 20 <5 990 41.9 29.9 44.4 21.4 3.8 20 2 1 390 15.9 29.6 22.1 47.1 1.3 P m m a woodland FCUS woodland Bare rock Grassland Glae~a/nalive scrub Beach eresl vegelal~on Marsh Mangrove [IIII] coconut Figure 2. Cousin Island vegetation. Table 5. Cousin Island: tree species recorded Introduced species Adenanthera pavonina Carica papaya Eucalyplus sp. Native species Euphorbia pyrifolia Ficus lutea Ficus rejlexa Hibiscus filiaceus Ochrosia opposififolia Pandanus baIfourii Pliyllan~hus pervilleanus Pisonia grandis Status unknown Morinda cifrifolia Total - - Hill No. stems % stems Plateau No. stems % stems Table 6. Cousin Island: most widespread shrub species. Shrubs occurring in five or more plots shown. Percentage shrub cover is the mean cover for those plots in which the species occurs. Introduced species Carica papaya Native species Cocos nucifera Euphorbia pyrifolia Ficus lutea Ficus rejlexa Ochrosia oppositifolia Phyllanthus pervilleanus Pisonia grandis Status unknown Morinda citrifolia Total Hill No. plots % shrub cover Plateau No. plots % shrub cover Flora And Vegetation: Discussion A vegetation survey of the island was competed by Diamond (1975) before the island had become dominated by Pisonia grandis woodland. At the time, the island (especially the plateau) was still dominated by plantation palms. The hill, largely unsuited for cultivation, was less extensively planted. Following the island's designation as a Nature Reserve, attempts to replant native vegetation were deemed largely unsuccessful (Diamond, 1975) and a process of natural succession occurred with coconuts removed to prevent the island being overtaken by coconut scrub. Fosberg (1970) predicted that the vegetation would undergo succession until dominated by Pisonia. This change has happened within a period of 30 years, assisted by the repression of coconut regrowth and the removal of mature fruiting palms. If mature palms had been left in place, and coconuts left to germinate, the plateau would probably now be a dense palmetum. Although Pisonia is a relatively fast-growing, short-lived tree with fragile wood, it can form climax vegetation through its ability to layer, and regenerate quickly from fallen stems (Schumacher and Wiithrich, 2000). It is possible that further change may result in areas of Ochrosia-dominated woodland (Fosberg, 1970); other abundant woody species on the plateau are small trees or large shrubs. The flora of Cousin has lost many of the introduced species that were recorded by Fosberg (1984). Of introduced woody species, the most widespread in natural habitats were Carica papaya and Adenanthera pavonina (although a number of other species occur, especially in previously cultivated areas around the marshes). There was evidence for widespread regeneration of both species. Although the most abundant woody exotic on the island, Carica is probably not of major conservation concern: its fruits are eaten by a number of endemic vertebrates including Foudia sechellarum (Collar and Stuart, 1985) and Mabuya spp. (Brooke and Houston, 1983). Individual plants are relatively short-lived and small (the mean height of Carica in the tree layer was 7.4 m compared to 10.7 m for Pisonia), so they are unlikely to shade out other tree species. Mature coconut palms were not found in any of the vegetation plots; large Cocos now have a restricted distribution on the island (mainly around the marsh; see Fig. 2). However, young Cocos plants were relatively widespread and abundant in the shrub layer on the plateau (more restricted on the hill). Management of coconut regrowth remains important. INVERTEBRATES Pitfall Trapping Pitfall trap assemblages were relatively large, compared to those from other islands surveyed (Table 7). Assemblages (excluding ants) were larger in the north west monsoon period than in the dry season dominated by south east trade winds. The high value for hill plots in the SE season is due to extremely high ant numbers trapped in one plot. Ants dominated all pitfall assemblages forming between 57% of the total invertebrate individuals (NW, hill) and 98% of invertebrate individuals (SE, hill). Other than ants, dominant invertebrate groups included Crustacea (including both Isopoda and Amphipoda), Blattodea, Dermaptera and Araneae (Fig. 3). In Hill plots, larger numbers of Crustacea were trapped. Only isopods were collected on the hill; amphipods were abundant but only trapped in plateau plots. Cockroaches (Blattodea) were also abundant in hill plots in both seasons. Plateau woodland sites were dominated by ants which made up 78.6% of the total individuals in pitfall assemblages. The most abundant species was the native Odontomaclzus troglodytes (4 1.5% of individuals), followed by ?Cardiocondyla emelyi (35.6% of individuals). The most abundant non-ant species (and the third most abundant species) was an amphipod crustacean which formed 5.0% of individuals. An earwig species (Dermaptera) made up 4.0% of individuals. A total of 73 morphospecies were collected in 20 plots. In hill woodland/scrub, assemblages were similar but less species-rich. A total of 48 taxa were collected in 16 plots. Ants were again dominant, foming 90.0% of the total individuals. Cardiocondyla emelyi was the most abundant species (88.2% of individuals). An isopod crustacean was the second most abundant species (4.9% of individuals). Other species form much smaller proportions of the total assemblage: a cockroach species made up 2.3% of individuals, Odontomachus troglodytes 0.7%. The crazy ant Anoplolepis gracilipes was collected twice. One individual was collected in a hill plot and one in a plateau plot. Table 7. Pitfall assemblages from Cousin Island. Only invertebrates of body length >2 mm included. (Number in parentheses = number of invertebrates excluding ants). Habitat I Mean no. individuals ~ e r 5 tram Hill Plateau Hill Plateau SE SE NW NW Cousin Plateau woodland Hill woodland Mean for all granitic islands H Blattodea bl Derrnaptera H Diptera Pa larvae El Lepidoptera Crustacea spider Ul others SE season NW season 58.0 (16.9) 122.9 (2 1.6) 4 10.2 (6.7) 62.7 (27.0) 6 1.8 (9.4) 61.1 (16.0) Figure 3. Composition of pitfall assemblages on Cousin Island, excluding ants. Leaf-insect Counts Leaf-insect counts were carried out for six tree and shrub species, five of these in both seasons (Table 8). For four of the species counted in both seasons, invertebrate densities were higher in June. For one species, invertebrate counts were higher in December, during the north west monsoon. As found on some other islands, the highest density of invertebrates was on the shrub Morinda citrifolia. Pisonia grandis also had high invertebrate densities (especially in June). Together, these two species dominate woodland vegetation on the plateau of Cousin. Table 8. Density of invertebrates on foliage, Cousin Island n = no. of leaves counted; NI = number of individual invertebrates. Native species Euphorbia pyrifolia Ficus lutea Ficus reflexa Ochrosia oppositifolia Pisonia grandis Status unknown Morinda citrifolia Species Malaise Trapping Malaise trapping was carried out in hill and plateau woodland habitats, during both seasons. Five Malaise traps (three in plateau plots, two in hill plots) were run in June, and four (two in each habitat) in December 1999 (Table 9). Assemblages were larger in the north west monsoon season (December), than in the south east season. However, there was no consistent difference in catch size between habitats. The major insect order in most seasons was the Diptera. In June, in hill plots, Hemiptera (especially Auchenorrhyncha) dominated assemblages. The majority of taxa collected have yet to be identified to species level. SE season (June) n mean NI mean NI leaf ' n ~ - ~ N W season (December) N mean NI mean NI l e a f ' rn-' 5 8 Table 9. Malaise trap assemblages, Cousin. NI = Number of Individuals. No. traps Mean NI trap-' Total NI Diptera Total NI Hemiptera Total NI Hymenoptera Total NI Lepidoptera Total NI Orthoptera Total NI Other orders SE (June) Hill Plateau 2 3 699.5 1038.0 NW (December) Hill Plateau Observation A list of species observed or collected in the current survey, and by previous workers, is given in Table 10. Terrestrial invertebrates were collected on both assessment visits; aquatic invertebrates were only collected when there was water in the marsh, in December. At this time, the marsh had standing water with a combined area of about 1,000 m2 and to a depth of up to 50cm. An aquatic light trap operated overnight collected two crustacean species in very large numbers. Discussion: Invertebrates Pitfall assemblages from Cousin Island were relatively large and assemblages on the plateau (excluding ants) were larger than those on the hill: plateau areas are more suitable for Seychelles magpie-robin than hill areas. The presence of the crazy ant Anoplolepis gracilipes in pitfall assemblages, albeit in small numbers, is of concern. This pest species was introduced in Seychelles in the early 1960s (Haines et al., 1994) and has since been spread to many islands including Marianne and FdicitC. On Bird Island, especially high concentrations of ants have caused tree death (Hill, in prep.) and the eradication of native reptiles from large parts of the island (Feare, 1999a). Crazy ants were not recorded on Cousin in 1982 (Bathe, 1982b) but their presence has been reported on several occasions, and ants in the vicinity of buildings have been eradicated. It is possible that the species had been present on the island for some time but has not been able to reach the pest proportions found on other islands due to competitive exclusion by other ant species favoured in the semi-natural habitats of Cousin Island. Leaf invertebrate counts were highest for the two tree species that currently dominate Cousin's woodland (especially plateau woodland). For most tree species (contrary to results for several islands) invertebrate densities were higher in the dry season (June) than in the north west monsoon season (December). Few aquatic invertebrates were collected on Cousin, probably as a result of the seasonality of standing water on the island. No dragonflies were recorded, although six species have been recorded on the island, four breeding (Bathe, 1982~) . Species lists have also been produced for Cousin bees (5 species: Bathe, 1982a) and ants (14 species: Bathe l982b). Table 10. Invertebrates, Cousin Island. Previous records (in notes); 1 = Bathe and Bathe, 1982a; 2 = Miihlenberg 1977; 3 = Bathe and Bathe, 1982b; 4 = Bathe and Bathe, 1982c; 5 = Blackman 1965, in Blackman and Pinhey, 1967. Order Family Species Notes Mollusca Achatinidae Achafina sp.t Many empty shells Arachnida: Amblypygi Araneae Scorpiones Crustacea: Decapoda Myriapoda: Chilopoda Diplopoda Insecta: Coleoptera Hymenoptera Subulinidae Tarantulidae Tetragnathidae Buthidae Coenobitidae Grapsidae Ocypodidae Scolopendridae Spirostreptidae Spirobolellidae Trichopolydesmidae Trigoniulidae Scarabaeidae Anthophoridae Apidae Formicidae Subulina octoua Bruguiere, 1792 ?Opeas sp. ?Charinus seychellarum Krapelin, 1898 Nephila inaurita (Walckenaer, 184 1) Isometrus maculatus (de Geer, 1778) Coenobita brevimanus Dana, 1 852 Grapsus tenlticrustatus (Herbst, 1783) Ocypode ceratophthabnus (Pallas, 1772) Ocypode cordimana Desmarest, 1825 Scolopendra subspinipes (Leach, 19 18) Seychelleptus seychellarum (Desjardins, 1834) ?Benoitiulusflavicollis Mauries, 1980 Cylindrodesmus hirsutus (Pocock, 1888) Spiromanes ?braueri (Attems, 1900) Spiromanes seychellarum Saussure & Zehntner, 1902 Oryctes monoceros (Olivier, 1789) Cerafina nodosivenfris Cockerel1 19 12 * Xylocopa caffra (Linnaeus, 1767) Apis mellifera adansoni Latreille, 1804 Anoplolepis gracilipes (Smith, 1857) Brachymyrmex cordemoyi Forel 1895 * Camponofus grandidieri Forel, 1886 * Camponofus hova Forel, 189 1 Cardiocondyla emetyi Forel, 188 1 Lepfogenys maxillosa (Smith, 1858) * Monomoriumfloricola (Jerdon, 185 1) * Odontomachus troglodytes Santschi, 19 14 ?Pachycondyla melanaria (Emery, 1894) Paratrechina bourbonica (Forel, 1886) * Paratrechina longicornis (Latreille, Recorded 1982' Recorded 1982' and 199912000 Recorded 1975' Recorded 1 9 8 2 ~ Recorded 1 9 8 2 ~ Recorded 1975' Recorded 1975', 1999- 2000 Recorded 1975' Recorded 1975' Table 10 (cont.) Order Fan~ilv S~ec ies Notes Lepidoptera Neuroptera Odonata Halictidae Megachilidae Vespidae Hesperiidae Lycaenidae Myrmeleontidae Coenagrionidae Aeshnidae Libellulidae Pheidole tnegacephala (Fabricius 1793) * Recorded 1982' Strumigenys rogeri Emery, 1890* Recorded 1982) Tapinoma melanocephalu?~l (Fabricius, Recorded 1 9752 1793)* Technotnyrtnex albipes (Smith, 186 1) Tetratnorium ?bicarinatutn (Nylander, 1846) Tetrarnoriutn languinosa Mayr, 1870 * Tetratnoriutn sitnillitnum (F. Smith, 185 1)* Pac/~yhalictus tnahensis (Cameron) * Megachile seychellensis Cameron, 1907 * Polistes olivaceus (de Geer, 1773) Borbo sp. Leptotes pirithous Linnaeus, 1767 Myrmeleon obscurus Rambur, 1852 Ceriagrion glabrutn (Burmeister, 1839)* Hetnianax ephippiger (Burmeister, 1839)* Diplocodes trivialis (Rambur, 1 842)* Orthetrum sfemtnale wrightii (Selys, 1869)* Tramea limbata (Selys, 1869)* Zyxomma petiolatum (Rambur, 1842)* Recorded 1975', 1 9U3 , 1999-2000 Recorded 1 982) Recorded 1982) Recorded 1982' Recorded 1982' Recorded 1980-8 l 4 Recorded 1980-8 l4 Recorded 1980-8 l 4 Recorded l965', 1980- 8 1 4 Recorded 1980-8 l4 Recorded 1965' t extinct? species recorded by previous workers but not observed in current survey VERTEBRATES Reptiles and Amphibians Six terrestrial reptiles were observed (Table 1 l), all native to Seychelles although one (Aldabra tortoise) was introduced in the granitic islands and was first recorded on Cousin in the 1960s (Bour, 1984). Four species of reptile previously recorded on Cousin were not observed in the current survey, the geckos Urocotyledon inexpectata and Gehyra mutilata, the Brahminy blind snake Ramphotyphlops braminus and the freshwater terrapin Pelusios subniger. Three of these (excluding G. mutilata) are rather cryptic, rarely observed species and were probably overlooked. U. inexpectata was recorded once, in 1979 (Shah et al., 1999); its current status is unknown.. The introduced gecko Gehyra mutilata has been observed in houses (Shah et al., 1999). It is common on larger islands such as Praslin and, if extinct, is likely to reinvade. The blind snake is a widespread introduced species found on many of the islands where agriculture formerly occurred, and probably survives on Cousin. The terrapin was introduced to the island from La Digue in c. 1940 (Bour, 1984). It is rarely observed by island staff but may survive. Two of the native skinks of Cousin Island, Seychelles skink Mabuya sechellensis and Wright's skink Mabuya wrightii, reach extremely high population densities on Cousin with a bioinass of between 96 kg and 184 kg per hectare (Hunter, 1978: Brooke and Houston, 1983). Such high bioinass is supported by the seabird colonies of the island. M. wriglztii is restricted to islands with seabird colonies although the apparent association may be simply the result of its inability to survive on islands with introduced rats (Cheke, 1984). M. seclzelleizsis, although endemic, is widespread in the granitic islands and the near coralline islands. The large gecko Ailuronyx seychellensis also survives on islands with rat populations, although it is most obvious on rat-free islands, where (as on Cousin) i t is diurnal and often found in houses (Cheke, 1984). In addition to the land reptiles, two marine turtle species breed on Cousin Island: green sea turtle Clzeloizia iizydas (L.) and hawksbill Eretmochelys imbricata (L.). Breeding hawksbills were observed in December. October to January is the peak breeding season for hawksbill sea turtles on Cousin (Frazier, 1984). One species ol'amphibian, an unidentified species of caecilian (possibly Hypogeoplzis I-osti-rltus) has been recorded on Cousin Island (Nussbaum, 1984b), but was not observed during the cui-rent survey. Table 1 1. Reptiles observed on Cousin. Status: E =endemic, I = introduced, N = native (in central Seychelles). Family Species Status Gekkonidae Ailurv~zys ej~cheller~sis (Dunieril & Bibron, bronze-eyed gecko E 1836) Pllels~ci1z~1 l s t r - i ~ ~ ~ n Tornier, 190 1 day gecko E Scincidae MNDIIJYI secIzc./I~~~sis (Dunieril & Bibron, 1836) Seychelles skink E MnDuja wr-ighrii (Boulenger) Wright's skink E Pa~nelatxirlc~is gclridir1er.i Boulenger, 1909 burrowing skink E Testudinidae Gc.odrc.lorle giganterr (Schweisger, 18 12) Aldabra giant tortoise I Birds In total, 15 land birds and waders were recorded (Table 12). Five of these were endemic species, three of which are regarded as endangered or vulnerabIe species in Seychelles (Watson, 1984). For much of the twentieth century, Cousin was the only island on which the Seychelles warbler Acrocephalus sechellensis occurred (Komdeur, 1988). In 1988-90 birds were translocated tc Aride and Cousine and further populations established (Komdeur, 1994). The Seychelles magpie-robin Copsychus sechellarum was translocated to Cousin in 1994 and the Cousin population is now the second largest of three island populations (Parr et al., 1999). The Seychelles fody Foudia sechellarum is currently restricted to three islands in the granitic archipelago, with an introduced population surviving on D ~ A ~ ~ O S . Cousin probably holds the major population of this species (Collar and Stuart, 1985). Penny (1974) noted that the endemic Seychelles form of the "Madagascar" turtle dove, Streptopeliu yicturata i-osti-ata, appeared to survive on the island but a survey in 1990 suggested that very few individuals display the characteristics of true S. p. rostrata. Most individuals bclonged to an intermediate form showing characteristics of both S. y. rostrata and the introduced Madagascar form S. p. yicturata (den Boer and Geelhoed, 1990), suggesting that S. y. rostrnta has become effectively extinct through cross- breeding. Two additional resident land bird species are known on Cousin. The black- crowned night heron Nycticorax izycticorax was found to be breeding on the island in 2000 (Anon, 2000), following natural colonisation of the island. There are also occasional records of the introduced barn owl Tyto alba and it seems likely that there is at least one resident bird. On Cousin, where rats are unavailable, barn owls prey on birds, especially fairy terns Gygis nlbn (Penny, 1975). Other bird species are also taken, suggesting that \he presence of the barn owl represents a threat to endemic land birds on the island. In addition to the land birds, Cousin Island supports breeding colonies of seven seabird species. Ten seabird species were observed (Table 13), seven of which breed on the island. Diamond (1975) lists 52 bird species that had been recorded from Cousin Island, including migrants and vagrants not recorded in this survey. Since his list was written, two new resident breeding birds have been added to the fauna of Cousin: Seychelles magpie-robin and black-crowned night heron, and the Seychelles blue pigeon Alectroeizas y~rlcherriina, which only occurred occasionally at the time of Diamond's list, is now resident. Table 12. Land birds and waders observed on Cousin. M = migrant species; E = Seychelles endemic species. Species Notes One observed in mangrove, 14/6/99 Bubulcus ibis cattle egret Butorides striatus green-backed heron Gallinulu clzlo~-opi~r comn~on moorhen Dromus urdeolu M crab plover Arenaria intelpres M ruddy turnstone Calidris alba M sanderling Streptopeliu pictulnta ssp. turtle dove Geopelia striuta barred ground dove Alectroenas pulcherri~na E Seychelles blue pigeon Copsychus sechellrrrrr~x E Seychelles magpie robin Acrocephalus seclrellensis E Seychelles warbler Nectarinia duss~rnrio-i E Seychelles sunbird Acridotheres tristis common mynah Foudia inadagascarie~zsis Madagascar fody Foudia seclzellar~l~n E Seychelles fody One observed near Roche Canon, 7/12/99 Common at main marsh, and in a variety of plateau and hill habitats One individual, December. Regularly observed on beaches and plateau woodland, in small groups, both June and December One group of 5-6 birds observed on beach, June Regularly seen around houses and in woodland, June and December Occasional at houses, and on hill glacis, June and December Nesting close to houses. Flock of 7-10 seen feeding on figs 2016199 (observed by Alan Burger) Regularly seen in woodland Very common in woodland Very common in woodland One observed in Casuarina close to research house, 14/6/99 Rarely seen Very common in woodland and around houses, June and December Table 13. Seabirds observed on Cousin Island. Species PufJinus pucificus wedge-tailed shearwater PufJinus llrernrinieri Audubon's shearwater Phaeton leptums white-tailed tropicbird Sterna ametherrrs bridled tern Anous sto1irl~r.s brown noddy Anous te~luirostris lesser noddy Gygis alba fairy tern Notes Breeding birds present (June) Breeding birds present (June & December) Breeding birds present (June & December) Breeding birds present (June) Breeding birds present (June) Breeding birds present (June) Breeding birds present (June & December) Fregata minor great frigatebird Seen overflying island several times, in both June and December Sterna dorrgalli roseate tern Seen from beach 23/6/99 (observed by Alan Burger) Sterna firscrita sooty tern Seen from beach 23/6/99 (observed by Alan Burger) Mammals Two mammal species were observed in the course of the survey, the endemic fruit bat Pteropus seychellensis and the introduced black-naped hare Lepus nigricollis. During both assessments, Seychelles fruit bats were observed feeding on fruit on Cousin. Most or all appear to roost on Praslin; bats were observed flying over the sea from Praslin to Cousin on the evening of 21st June. Black-naped hares are the only terrestrial mammal on the island. They were seen every day of the survey, usually singly, throughout the island in woodland, scrub and grassy areas. The population of hares was estimated to be between 50 and 100 animals in 1974 (Diamond, 1975). In 1981, the population was estimated as 120-170 individuals (Kirk and Racey, 1992). The effect of the animals on the vegetation of Cousin has not been fully documented. In the 1980s, faecal pellets were dominated by plants that are now rather rare on the plateau (grasses and sedges). Hares may also distribute Boerlzavia and Aclzyranthes, although the former species is also now rare on Cousin in comparison to many other islands. It is also possible that hares reduce the regeneration of Casuarina (Kirk and Racey, 1992). Rats (Rattus spp.), although widespread on other islands of the granitic Seychelles (and introduced soon after human colonisation to many of the islands: Fauvel, 1909), have never been present on Cousin. The absence of rats and cats accounts for the survival here of the Seychelles warbler and large colonies of breeding seabirds. CONSERVATION RECOMMENDATIONS Conservation recommendations have been given in various management plans for the Nature Reserve, including the most recent (Shah et al., 1999). Recommendations generally centre on the preservation of the island's existing wildlife values, rather than on habitat restoration, as a natural process of rehabilitation has occurred since the island was acquired as a nature reserve. In 30 years, Pisonia forest has replaced coconut plantations and the forest existing today, at least on the plateau, probably resembles the original vegetation of the island (Fosberg, 1970). The major recommendations of management plans concern the need to prevent invasion of alien species currently absent from the island, especially mammals. Vegetation management measures in the most recent management plan are limited to the removal of fallen coconuts and the management of beach-crest vegetation by encouraging native species and removing casuarinas. Additional measures that could be proposed in the light of this report include: 1) Monitoring of crazy ant populations and (if feasible) eradication of this species. Crazy ants are present, but apparently in very small numbers. It is important to monitor populations. The species tends to undergo "boom and bust" demography after introduction to a new area (Haines et al., 1994) and it can have important conservation implications (Haines et al., 1994; Feare, 1999). 2) Removal of mature coconut palms around marsh. Although probably a native species in the granitic Seychelles (Sauer, 1967), the present abundance of coconuts is a function of planting in the nineteenth and twentieth centuries. On Cousin, coconuts can be regarded as a weed because the regrowth of young palms from fallen nuts produces dense vegetation unsuitable for foraging by Seychelles magpie-robin, which prefers open areas of leaf litter (McCulloch, 1994). Coconut palms are currently controlled by removal of seedling growth and fallen nuts. Both are still abundant near the main area of mature palms surviving on the plateau at the marsh. Here mature palms shade the marsh and prevent the growth of aquatic macrophytes. Removal of most (or all) of these palms would allow more light to reach the seasonal marsh and reduce the need for management of coconut seedling growth. 3) Controlleradication of other invasive introduced species. Few introduced plant species appear invasive in Cousin's semi-natural habitats. Adenanthera pavonina was rather widespread in vegetation plots and produces many seedlings; it should be removed. The introduced ornamental vine Rangoon creeper Quisqualis indica only occurs in one place near the marsh but is potentially invasive through vegetative propagation and could also be removed. Bamboo Barnbusa vulgaris also has the potential for vegetative spread. The species rarely flowers so is unlikely to spread by seed at least one clump could be left in place. Because a number of endangered endemic birds already exist on the small island of Cousin, further translocations of endemic birds to the island are not recommended unless a greater understanding of habitat requirements and compatibility of species can be gained. Appendix 1. Plant species recorded from Cousin Island (excluding seagrasses) Plants recorded in the current survey (mainly sight records) are numbered. For plants only recorded by previous authors, not in current survey, date of most recent record is given (see below). Taxonomy of dicotyledons as given by Friedmann (1994). Of Monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>lo00 individuals observed); C = Common (100 - 1000 individuals observed); F = Frequent (10 - 100 individuals observed); Occasional (3 - 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: Cu = Cultivation/settlement area; PG = Plateau grassland; PW = Plateau woodland; HW = Hill Woodland; G1 = Glacis; BC = Beach Crest; Ma = Marsh; Mg = Mangrove. Historical records (in Notes): 1= Fosberg 1970; 2 = Bathe & Bathe 1982; 3 = Robertson 1989,4 = Schumacher & Wiithrich 2000. Species Status Abund. Habitats Notes PTERIDOPHYTA Adiantaceae 1 Acrostichum aureum L. Davalliaceae 2 Nephrolepis ?biserrata (Sw.) Schott Nephrolepis multi'ora (Roxb.) Jarrett Polypodiaceae 3 Phymatosorus scolopendrin (Burm. f.) ANGIOSPERMAE: Dicotyledons Acanthaceae 4 Asystasia sp B. (sensu Friedmann) Asystasia gangetica (L.) T . Anders. Justicia gendarussa Aizoaceae 5 Glitzus oppositifolius (L.) A. DC. Amaranthaceae 6 Achyrantlzes aspera L. 7 Amaranthus dubius Mart. ex Thell. 8 Lagrezia cf. madagascariensis (Poir.) Moq. Anacardiaceae Mangifera indica L. Spotzdias cytherea Sonn. Annonaceae Annona muricata L. 9 Annona reticulata L. Mg PW HW, PW PC, G1 PW, Cu PW PW, Cu BC Cu Recorded 1970, 1982l.'. = N. biserrata? Recorded 1970, 1982, 1999' .*.~. = A. sp. B? Recorded 19701, not 1982~. Extinct on Cousin Recorded 1970, 1982l .~ . Extinct on Cousin Recorded 19701, not 1982 2. Extinct on Cousin Recorded 1970, 1982, 19991.2.4 10 Annona squamosa L. Cu 66 Species Status Abund. Habitats Notes Apocynaceae 11 Cafharanthus roseus (L.) G. Don. 12 Ocllrosia opposififolia (L.) K . Schum. 13 Plunzeriu rubra L. Avicenniaceae 14 Avicennia marina (Forssk.) Vierh. Boraginaceae 15 Cordia subcorduta Lam. 16 Heliotropiunz indicum L. Tournefortia argentea L. f. Caesalpiniaceae 17 Caesalpiniu bonduc (L.) Roxb. I8 Setznu occidentalis (L.) Link Capparidaceae 19 Cleotne viscosa L. Caricaceae 20 Curica papaya L. Casuarinaceae 21 Casuarina equisetifoliu J. R. & G. Foster Combretaceae 22 Quisqualis indica L. 23 Tertninulia catappa L. Composi tae Synedrella nodiflora (L.) Gaertn. 24 Vernonia cinerea (L.) Less. Convulvulaceae 25 Ipotnoea macrantha Jacq. 26 Ipomoea pes-caprae (L.) R. Br. 27 Ipotnoea venosa (Desr.) Crassulaceae 28 Kulanclzoe pinnata (Lam.) Pers. Cucurbitaceae C~tcurnis p. Clrcwbita moschata (Lam.) Poir. Momordica charantia L. Triclzosanthes cucumerina L. Euphorbinceae 29 Aculypha indica L. E~rphor-bia hirta L. E~rphorbia prostrata L. 30 E~iphorbia pyrifolia Lam. 3 1 E~iplzorbia thymifolia L. E~rplzorbia tirucalli Manihot esculenta Crantz HW, Cu PW Cu Mg BC Ma PW Ma, HW GI PW BC Cu PW PW BC BC, GI PW PW PW HW, G1 G1 Recorded 19701, 1982'. Extinct on Cousin Recorded I 970'. 1982' Recorded 19701, not 1982'. Extinct on Cousin Recorded 19701, not 1982~. Extinct on Cousin Recorded 19701, not 1982'. Extinct on Cousin Recorded 19701, not 1982'. Extinct on Cousin Recorded 1970, 1982'.' Recorded 1970' Recorded 1982~, extinct on Cousin Recorded 1970, 1982',', extinct on Cousin Pcdilanthus tithymaloides (L.) Poit. I Recorded 1 9 9 9 ~ Species Status Abund. Habitats Notes Phvllar~rh~rs acidus (L.) Skeels Recorded 1970, 1982l.'. 32 Phyllurithrrs arnarus Schumach. et Thonn. 33 Pl~yllarzthrrs pervilleuruts (Baillon) Mull. Arg. Pl~vllantkus terzell~ls Roxb. 34 Ricirirrs corimrr~zis L. Goodeniaceae 35 Scaevola sericea Vahl. Guttiferae 36 Calophyll~im inophyllurn L. Labiatae 37 Plectranth~is cirilboiriic~rs (Lour.) Spreng. Lauraceae Persea arizericurzn Mill. Lecythidaceae 38 Bur-rir~gtonia usiatica (L.) Kurtz Malvaceae 39 Abutilorz irldicurn (L.) Sweet 40 Gossypiurn hirsuturil L. Hibiscus sriratterzsis L. 41 Hibiscus tiliaceus L. Malachra capitata (L.) L. Sidu acuta Burm. f. 42 Sidu corcfijoliu L. Sicfa sstipulata Cav. 43 Tllespesia populrleu (L.) Soland. ex Correa Mimosaceae 44 Aderlanthera pavorlirla L. Moraceae Ar-tocarpus altilis(Parkins.) Fosb. Ficus benghalerzsis L. 45 Ficus lustea Vahl. 46 Ficus rejexa Thunb. seychellensis (Baker) Berg 47 Ficus rubra Vahl. Moringaceae 48 Morirzga oleifera Lam. Myrtaceae 49 Eucalyptus canzald~ilerzsis Dehnh. Syzygium samararzgerzse (Bl.) M e n & Pen. Nyctaginaceae 50 Boerhavia reperzs L. 5 1 Mirabilis jalapa L. 52 Pisonia randi is R. Br. PW PW PW BC PW, HW PW, PG BC PW, Cu PW BC GI, HW BC HW HW, PW HW PW Cu HW PG Cu Extinct on Cousin Recorded 1 9994 Recorded 1 970', 1982'. Extinct on Cousin? Recorded 1982'. Probably extinct on Cousin Recorded 1970'. Not in Seychelles? Recorded 1 9701 Recorded 1 98g3 Recorded 19701, not 1982'. Extinct on Cousin Recorded 1999~ . = F. rubra? Recorded 19701, 1982'. Extinct on Cousin Species Status Abund. Habitats Notes Onagraceae 53 Ludwigia octovalvis (Jacquin) Raven Oxalidaceae 54 Averrhoa bilimbi L. Papilionaceae 55 Canavalia cathartica Thouars 56 Gliricidia sepium (Jacq.) Walp. Sesbmia bispinosa (Jacq.) W. F . Wight Vigna unguiculata (L.) Walp. 57 Sesbatlia cannnbinu (Retz.) Poir. Passifloraceae 58 Passifloru foetidu L. Passiflora s~rberosa L. Piperaceae 59 Pepet-omia pellucidu (L.) H . B. K. Polygonaceae Polygonum senegalense Meisn. Portulacaceae 60 Portulaca oleracea L. Rhizophoraceae 61 Rhizoplzora nzucrotlata Lam. Rubiaceae 62 Coffea sp. 63 Guettarda speciosa L. Hedyotis coryrnbosa (L.) Lam. 64 Morinda citrifolia L. Rutaceae Clausena nnisata (Willd) Hook f. 65 Citrus sp. 66 Murraya koenigii (L.) Spreng.. Solanaceae 67 Capsicum frutescens L. 68 Datura metel L Nicotiana tabacum L. 69 Solanum americarzurn Mill. 70 Solunum lycopersicurn L. Solanum rnelongena L Surianaceae 7 1 Suriana tnaritima L. Turneraceae 72 Turnera arzgustifolia Miller Umbelliferae Centella asiatica (L.) Urb. Verbenaceae Ma Cu PW PW Ma HW PW GI Mg Cu BC PW, HW Cu PW Cu PG Ma Cu BC PW Recorded 1970', 1982'. = S. cannabina? Recorded 19701, not 1982~. Extinct on Cousin Recorded 1970'. 1 9 8 2 ~ Recorded 1970'. 1 9822. Recorded 1970' Recorded 1970', 1982'. = Murraya koenigii? Recorded 1982'. Probably extinct on Cousin Recorded 19701, not 1982, 1999*4. Cultivated occasionally Recorded 19701, not 1982'. 73 Stachytarpheta jamaicensis (L.) Vahl. I L PW, PG Species Status Abund. Habitats Notes ANGIOSPERMAE: Monotyledons Agavaceae Furcrrrea foetirla (L.) Haw Amaryllidaceae 74 Crinuul asiaticurn L. 75 Hynenocallis littorrrlis (Jacq) Salisb. 76 Scadosus rnultrj7oru.s (Martyn.) Raf. Araceae 77 Alocnsia ~nacrorrl~ixi (L.) G. Don. Colocasia escule~zta (L.) Schott Bromeliaceae 78 Ananas co~msrrs (L.) Merr. Cannaceae 79 Catlncc hybrids Commelinaceae 80 Co~n~nelina diff~rsa Burn1 f. Cyperaceae 81 Bulbostylis barbata (Rottb.) C.B.Cl. Cyperus alopecuroirles Rottb. 82 Fitnbristylis cotnplulata (Retz.) Link 83 Fimbristylis qm~osa R. Br. 84 Finlbristylis sp. (glacis sedge) Kyllinga ~no~~ocephala Rottb. 85 Kyllinga polyphylla Willd. Ex Kunth Mariscus dubius (Rottb) Fischer 86 Mariscus ligrrlaris (L.) Urb. 87 Pycreus polystacl~yos (Rottb.) P. Beauv. Dioscoriaceae Dinscorea alata L. Gramineae 88 Ba~nbusa vulgaris Schrad. Ex Wend1 var. aureo-variegata Braclziaria subquadriyara (Trin.) Hitchc. Dactylocteniunz ctenoirIes (Steud.) Bosser or D. aegypticum (L.) Willd. Digitaria horizontalis WiIld. Digitaria radicosa (Presl.) Miq. Digitaria setigera Roth. Eleusine indica (L.) Gaertn. Enteropogon seclzellensis (Baker) Dur & Schinz PG PW PW PW Cu, GI Cu G1 G 1 GI GI GI PW, GI G 1 HW Mar Recorded 19701, 1982' Probably extinct on Cousin Recorded 19701, 1982'. Probably extinct on Cousin Recorded 19701, not 1 9 8 2 ~ Recorded 19701, 1 9 8 2 ~ Recorded 1970'. 1999 Recorded 197u1, not 1982*. Extinct on Cousin Recorded 19701, not 1 9 8 2 ~ Recorded 19701, 1982'. Probably extinct on Cousin Recorded 19701, 1 9 9 9 ~ Recorded 1 9701, 1 9 9 9 ~ Recorded 19701, not 1 9 8 2 ~ Recorded 19701, not 1 9 8 2 ~ Recorded 1 WO', 1 9822 Recorded 1970, 1982, 1999 2* Species Status Abund. Habitats Notes Recorded 1970'. 199gJ Erqrostis tenella (L.) Beauv. Eragrostis suOaequiglurt~is Renvoize 89 Putlicunz brevifoliutn L. 90 Patlicutn nm~inzunl L. 91 SporoOolus virgit~icus (L.) Kunth. 92 Stetzotaplzrunl dinlicliatunr (L.) Brogn. Sterzotuplmm tnicr.atztlzut~ (Desv.) Hubb. Lemnaceae Letma sp. Musaceae 93 M~r.su ?supiet~tutri L. Pal mae 94 cocos t1ucifer.u L. Pandanaceae 95 Patldatlus Oalfourii Mart. A PW, PG R Mar A BC A PG F Cu F PW, HW C G1, HW Recorded 1970'. not Recorded 1999 '. Recorded 1970'; occasional outbreaks in marsh introduced species. However, the most abundant single species was takamaka (28 trees, 28.6% of total trees). Cinnamon was again the second most abundant tree species (17 trees, 17.3% of total trees). Tree species diversity was higher in hill plots than in plateau plots, and the hill woodland contained a number of endemic shrub species including Paragenipa wrightii, Erythroxlurn sechellarurn and Syzygium wrightii. The shrub layer of low hill woodland was again dominated by Chrysobalanus icaco, found in 14 of 15 plots, with a mean cover of 23.6%. Phoeizicophorium borsigianurn was as widespread as Chrysobalanus, but contributed less to the shrub cover within plots where it occurred (mean cover was 13.9%). Canthiurn bibracteattun occurred in 13 of 15 plots, with mean cover of 7.8%. Cinnamon was found in 1 1 of 15 plots forming 1 1.5% cover in those plots in which it occurred. The woodland of plateaux and low hills showed great similarity. In both cases, most of the trees present belonged to native species. The presence of native and endemic shrubs in hill woodland indicated that high woodland vegetation appeared to be advancing up-slope into areas previously occupied by native scrub. In early 2000, several Calophyllunz trees on the eastern plateau were suffering from symptoms of takamaka wilt disease caused by the fungus Leptogr*aphiunz (Verticillium) calophylli (Ivory et al., 1996: Wainhouse et al, 1998). This disease has caused extensive death of Calophyllum trees on several other islands including North Island and Mahe and could threaten all high forest on Curieuse, which is dominated by this species. INVERTEBRATES Pitfall Trapping Pitfall trap assemblages were smaller than average for granitic islands (Table 4); in part, this reflects the lower abundance of ants on Curieuse compared to some other islands, notably those infested with crazy ant Anoplolepis gracilipes such as Marianne and Fdicitk In fact, plateau sites were rather rich in invertebrates other than ants. In both habitats, invertebrate assemblages were larger during the north west monsoon season, and on the plateau. Lowest invertebrate counts came from hill woodland in the dry south east season. The composition of assemblages also differed between the plateau and hill woodland, although both were dominated by ants (Hymenoptera: Formicidae). Ants formed a larger proportion of the total assemblage in hill woodland than in plateau woodland sites (Fig. 3). Plateau woodland contained greater numbers of earwigs (Dermaptera), beetles (Coleoptera) and woodlice (Crustacea: Isopoda). Woodlice were absent in hill plots. In both hill and plateau woodland, the most abundant invertebrate was the ant Odontomachus troglodytes, which formed 39.1% of all individuals in the plateau woodland and 4 1.3% of all individuals in hill woodland. In hill woodland, the four most commonly trapped species were all ants. The most abundant invertebrate other than ants was an earwig (4.9% of individual invertebrates belonged to this species). In plateau plots, the two most abundant species were ants, and the third was an earwig (making up Table 2. Extent of major vegetation types, Curieuse Island Vegetation type Hill Woodland (predominantly native) (> 10 nl asl.) Woodland (mixed) Scrub (native spp.) Scrub (mixed) Scrub (Introduced: predonlinantly Chrysobalai7us) Bare rock Plateau Woodland (predominantly native) (< 10 nl asl.) Woodland (mixed) Coconut with regeneration Scrub (native spp.) Scrub (mixed) Scrub (Introduced: predonlinantly Clzrysobalanus) Mangrove Freshwater marsh Beach crest vegetation Grasslandlgarden Bare rock Approx. area (ha) 27.4 Twenty-five plots were carried out in plateau woodland with a combined area of 2,500 m2 (approximately 0.7% of the total area of this vegetation type), and 15 in low hill woodland covering 1,500 m2 or 0.3% of the total area of the habitat. A summary of results is shown in Table 3. Table 3. Curieuse vegetation plot summary Plateau plots had a relatively high density of trees and a relatively complete canopy (mean canopy cover = 72%). At ground level, vegetation cover was less than 50% and there was a high proportion of open leaf litter. The tree layer was dominated by a Habitat Plateau Hill native species, takamaka Calophyllum inophyllum (127 trees, 68% of total trees), although the introduced cinnamon Cinnamomum verum was also abundant (3 1 trees, 17% of total trees). The shrub layer was dominated by the invasive introduced shrub Chrysobalanus icaco, which was present in 18 of 25 plots and covered 25% of the shrub Plots Mean Mean Mean shrub Mean herb Open leaf Bare Dead wood altitude trees layer cover layer cover litter rock (pieces per (m asl) ha-' ("h) (%) cover (%) (%) plot) 2 5 <5 744 53.0 42.6 50.0 9.2 1.3 15 2 1 653 46.0 34.0 41.0 26.6 1.1 layer in plots where it occurred. Other widespread species of the shrub layer included cinnamon (in 17 plots, forming on average 14.2% cover), Phoenicophorium borsigianu~n (in 11 plots, mean 9.1% cover) and takamaka (10 plots, mean 2.6% ccver). Plots in low hill woodland had a lower density of stems and a less complete canopy (mean canopy cover=62%). Vegetation of the herb layer was less dense than that in plateau plots, but a larger proportion of the ground was outcrops of bare rock. The tree layer contained less natives than that in plateau woodland; 30.6% of stems were W Takamaka woodland Mlxed woodland - U Grasslandlgarden Marsh Figure 2. Curieuse Island: vegetation Vegetation The extents of major vegetation types on Curieuse are shown in Table 2 and Figure 2. Curieuse has a wide range of vegetation types and several were not studied in detail. Upland areas of Curieuse are dominated by scrublands that have a variety of endemic species together with one abundant introduced species, cocoplum Chrysobalanus icaco. There are some areas of open rock, and the plateaux have wetland vegetation including mangrove and freshwater marsh. The vegetation survey concentrated on areas of greatest value for endemic bird conservation: the woodland and scrub of plateaux and low hills. FLORA AND VEGETATION Flora A total of 242 plant species was recorded on Curieuse, including 1 1 ferns, one gymnosperm (introduced) and 230 angiosperms (Appendix 1). Of the angiosperms, 13 1 (57.0%) species are regarded as introduced (Friedmann, 1994) and 8 1 (35.2%) native. Of the native plants, 23 taxa are endemic to the Seychelles (10.0% of the total flora). At least 43 species of introduced angiosperm (1 8.7% of the flora) recorded on Curieuse were restricted to gardens around houses and were not found away from cultivation. Most would probably become extinct were cultivation to cease. The proportions of the total flora made up of introduced species and Seychelles endemics were similar to those for the Seychelles as a whole (of the total Seychelles flora, around 54% is introduced and 9% endemic; Procter, 1984). Compared to the flora of smaller islands, Curieuse is relatively rich in endemic plants. Several endemic species are abundant on Curieuse, notably the Coco-de-Mer palm Lodoicea maldivica; Curieuse and Praslin have the only natural populations of the species although planted specimens exist on many other islands (Procter, 1974). In addition, some of the endemic species recorded by previous observers but not in the current survey may still survive on the island (see Appendix 1). Two are known to be extinct there: wild vanilla Vanilla phalaenopsis has not been recorded on the island since the nineteenth century, and the parasitic shrub Bakerella clavata ssp. sechellensis is apparently completely extinct (Carlstrom, 1996a). Ten species recorded by previous observers may still survive on the island, bringing the total number of plants on the island to 252, with 25 Seychelles endemics. Of the introduced plants established on Curieuse, 15 are invasive weedy species. Several of the woody weeds which are most invasive on the smaller islands of Seychelles are present, including cocoplum Chrysobalanus icaco and cinnamon Cinnamomum verum, both of which are abundant. Coconuts Cocos nucfera were not widely planted on the island and, although abundant in the north of the island, they are less common elsewhere; Curieuse has far fewer coconuts than most other small islands in Seychelles. Table 1. Area of Curieuse by altitude (calculated from maps published by Directorate of Overseas Survey (UK)/Seychelles Government) Altitude range (m. ad.) Area (ha) Percentage total area > 150 2 0.7 100 - 150 32 11.1 50 - 100 6 7 23.4 10 - 50 111 38.8 0 - 10 74 25.9 HISTORY Curieuse was first named Ile Rouge (after its exposed red earth soils) but its name was changed to that of one of the vessels of the Marion Dufresne expedition of 1768 (prior to settlement of the Seychelles). The same expedition noted little timber on the island, and very few land tortoises (this population later became extinct). Both coconut and Coco-de-Mer Lodoicea maldivica were recorded (Lionnet, 1984). Malavois (1 787) recorded that the hill was covered with Coco-de-Mer (in Fauvel, 1909). In October 18 17, the island was leased, but it reverted to the control of the colonial government in 1827. A leper colony was established in 1829 for lepers from Mauritius and Seychelles, and 78 people were housed there by 1830 (McAteer, 200 1). Lepers were later joined by old and infirm paupers, but by the late 1860s the colony was dwindling. When Edward Newton visited in 1866, there were only three lepers and "a few old decrepit paupers" remaining (Newton, 1867). The settlement was not closed until 1900, when the few remaining lepers and paupers were moved to new facilities on Round Island, Praslin, and Curieuse was commercially leased again. Coconut plantations were established, production reaching 300,000 nuts per year in 1930 (Anon, n.d.). Vanilla was introduced as a commercial crop in the early twentieth century; production ceased in the 1930s (IUCN, 1993). In 1909- 10, a 500 m wall was constructed across Baie La Raie, enclosing the bay which was used for rearing sea turtles for meat. However, the project failed in 19 14 when most of the turtles died of disease (Anon, n.d.). In 1937, the government regained control of the island and reopened the leper colony to replace overcrowded facilities on Round Island, Praslin, and Round Island, Mahk (McAteer, 200 1). The colony was abandoned in 1965 and the island and 1,370 ha of the surrounding seas were declared a Marine National Park in 1979 (IUCN, 1993). The island is still managed by the Seychelles Marine Parks Authority. The population is small (around 10 people). A large number of tourists make day visits from Praslin. In July 2000, a project of rat and cat eradication was undertaken on Curieuse, to eliminate alien mammals and enhance the conservation value of the island. Aerial application of pelleted bait was used for rats, and poisoningltrapping for cats.