Conservation of bats on remote Indo-Pacific islands.

Bat Biology and Conservation Edited by Thomas H. Kunz and Paul A. Racey SMITHSONIAN INSTITUTION PRESS Washington and London 23 Conservation of Bats on Remote Indo-Pacific Islands WILLIAM E. RAINEY Oceanic island biotas have played key roles in both the theory and practice of conservation biology. They provided the basis for the theory of equilibrium island biogeography (MacArthur and Wilson 1967), which has since been widely applied to other discontinuous habitats. They furnish some of the best-documented examples of anthropogenic extinctions and introductions (Simberloff 1995), and offer sites of manageable scale where experimental intervention, such as translocation or predator extermination, can be undertaken on behalf of endangered species (Clout and Craig 1995). While research and management efforts on remoteisland vertebrates have emphasized endemic land birds and seabirds, the less-diverse bat communities have recently attracted attention, driven by concerns about biodiversity, ecosystem function, and the maintenance of traditional human resources (Falanruw 1988; Cox et al. 1991). Three recent compilations (Mickleburgh et al. 1992; Wilson and Graham 1992; Flannery 1995) covered many topics relevant to bat conservation on paleotropical islands, including systematics, biogeography, human utilization, and the status of species. Additionally, Mickleburgh et al. (1992) have offered a program of conservation action for pteropodids. The following discussion emphasizes the special circumstances of the small, largely endemic bat faunas of remote Indo-Pacific islands but draws on the more-diverse faunas from Southeast Asia and Australia to examine specific themes. Bats from remote islands are largely pteropodids of the wide-ranging genus Pteropus, most of whose members are island endemics (Rainey and Pierson 1992). Evolutionary and Ecological Context Among mammals, bats are outliers in terms of maximum life span in relation to body size (Austad and Fisher 1991). Long mass-specific life spans in birds and volant mammals link flight and low mortality which, in turn, are correlated with low annual reproductive output (Holmes and Austad 1995). While constraints of flight may have shaped the reproductive specializations of bats (Hayssen and Kunz 1996), populations are adapted to low predation and low stochastic adult mortality. Evolutionary responses of vertebrate populations to altered selection pressures on islands can be rapid. The most numerous examples involve morphological change (Smith et al. 1995), but Austad (1993) demonstrated that an island population of Virginia opos326 Conservation of Remote Indo-Pacific Island Bats 327 sums (Didelphis virginiana), with low predation for about 5,000 years, had both reduced Utter size and reduced rates of senescence relative to mainland populations. Assuming evolutionary scope for even lower reproductive rate in island-dwelling bats, such adaptations could heighten the risk of extinction with the abrupt increase in predation that accompanies human colonization of islands. While trends in body size versus island area vary across bat taxa (Krzanowski 1967), McNab (1994) demonstrated a general trend toward smaller body size and lower massspecific metabohc rates for some species of Pteropus on small islands. He noted that the long-term persistence of small populations is highly sensitive to population size and that decreased individual requirements permit larger populations of resource-Hmited species. Ornithologists, in particular, have intensively explored (without reaching consensus on cause) an "insular syndrome" of increased densities, broadened habitat or dietary niches, and, occasionally, reduced territoriaUty in birds on islands relative to the same or related taxa on larger adjacent land masses (ThioUay 1993). Interactions among different species are simplified in the depauperate communities of small islands. In what are typically evolutionarily asymmetrical relationships, small guilds of generalists, including ffugivorous and nectarivorous bats, polfinate or disperse seeds of numerous plants (Woodell 1979; Cox et al. 1991). There are notably few vertebrate dispersers of the often large-seeded fruits of island canopy trees. Thus, declines or extinctions in this guild raise questions about long-term impacts on forest regeneration (Rainey et al. 1995), and about cascading effects on other species, including humans, whose traditional subsistence systems may exploit large-seeded forest trees (Wiles and Fujita 1992). Nocturnal aerial insectivores on remote islands are few, and the ecosystem role of insectivorous bats in these locales is little known. Extinctions and Extirpations of Bats on Islands Archaeological Perspectives on Human Impact Accumulating archaeological data (Flannery 1995; Steadman 1995) make it clear that human colonization of smaller oceanic islands in the Pacific was accompanied by numerous extinctions of endemic vertebrates (largely land birds) and local extirpations of indigenous species. As human populations grew on many of these islands, faunas were increasingly influenced by widespread introductions of domesticated and commensal vertebrates and by alterations in vegetation structure and composition, especially in lowland forests (Steadman and Rolett 1996). Identifying taxa found in archeological deposits as anthropogenic extinctions requires careful interpretation. Bones may be prehistorical imports, vagrants (Wragg 1995), or taxa extirpated by environmental change (Weisler and Gargett 1993). Nonetheless, models of biogeographic processes that treat human-influenced islands as isolated exceptions (Lack 1976; Adler 1992) must be reviewed carefully against evidence of pervasive human colonization and extensive defaunation of islands in the tropics and sub tropics. Then, as now, exploitation of island wildlife emphasized subsistence, and easily harvested forms declined first (e.g., colonial ground-nesting seabirds, large pigeons, and terrestrial or flightless species). Additionally, cultural preferences sometimes emphasized particular taxa (e.g., the red feathers of the Rimatara lorikeet, Vini kuhlii) and contributed to local declines (Watling 1995). Archeological evidence for reductions, extirpations, and extinctions of bat populations on Indo-Pacific islands are summarized in Table 23.1. Although archaeological surveys have revealed numerous extinctions of bird taxa, there is only one record of bat extinction, an undescribed microchiropteran from Maui, Hawaii (James et al. 1987). The record does, however, suggest or document declines and local extirpation for a number of other taxa. Remains of bats from the two East Pacific islands are not from human-occupied sites, but radiocarbon dates, stratigraphy, and records for other fauna are correlated with the disappearance or extirpation of these species with human colonization (Steadman 1986; James et al. 1987, personal communication). The apparent pattern of extirpation and extinction may be biased against detection of small vertebrates, including microchiropteran bats, particularly at human occupation sites. Small vertebrates are less likely to be harvested, and their remains are less likely to survive food processing, consumption, and extended burial. Additionally, coarser screens, more commonly used in the past for sampling archaeological deposits, have selected against recovery (Flannery et al. 1988). The only island archaeofauna showing loss of several bat species is on 'Eua, Tonga (Koopman and Steadman 1995). The extirpated species—Pteropus samoensis, Notopteris macdonaldi, and Chaerephon jobensis—are currently unknown elsewhere in the Tongan archipelago, although all are extant in Fiji (Flannery 1995). Notopteris macdonaldi and C. jobensis are present in Vanuatu and P. samoensis in Samoa. Pteropus tonganus and Emballonura semicaudata have been recovered from prehuman strata on 'Eua, and both species persist to the present (Koopman and Steadman 1995). The prehistoric extirpation of N. macdonaldi and C. jobensis may be attributed to the high vulnerability of relatively largebodied, aggregated, cave-roosting species to overharvesting and disturbance. Flannery (1995) reported that C. jobensis is currently collected for food from caves in Fiji. Although in 328 W. E. RAINEY Table 23.1 Archaeological Evidence of Reductions in Indo-Pacific Populations of Island Bats Locality Species Impact Local distribution Comments Source Rodrigues Round Island, Mauritius Okinoerabu, Ryukyu Island Rota, Marianas Island 'Eua, Tonga Mangaia, Cook Island Aitutaki, Cook Island Ma'uke, Cook Island Maui, Hawaiian Island Floreana (=Santa Maria), Galapagos Island Pteropus niger Pteropus rodricensis Pteropus dasymallus Emballonura semicaudata Pteropus satnoensis Notopteris macdonaldi Chaerephon jobensis Pteropus tonganus Pteropus tonganus Pteropus tonganus Undescribed vespertilionid Lasiurus borealis Prehistoric extirpation? Prehistoric extirpation? Prehistoric extirpation? Prehistoric extirpation Prehistoric extirpation Declining harvest through time Prehistoric extirpation Prehistoric extirpation Prehistoric extinction Historic extirpation Persists on Mauritius Persists on Rodrigues Extant elsewhere in archipelago Extant elsewhere in archipelago Absent elsewhere in Tonga; present in adjacent archipelagoes Present in island interior Extant elsewhere in archipelago Extant elsewhere in archipelago Remains also recovered elsewhere in archipelago Extant elsewhere in archipelago Skull in cave with extinct taxa Skull in bone fissure fill Occupation site; limited remains Occupation site; limited remains Raptor prey deposits and occupation sites; two other bat species persist to present Human occupation site Occupation site; limited remains Occupation site Cave trap; bones of extant Lasiurus cinereus semotus also present in deposit Barn owl prey deposit; owl extirpated mid1800s Cheke and Dahl 1981 Cheke and Dahl 1981 Nishinakagawa et al. 1994 Steadman 1992 Koopman and Steadman 1995 Kirch et al. 1992 Steadman 1991 Walter 1990 (in Koopman and Steadman 1995) James et al. 1987; H. F. James, personal communication Steadman 1986 Samoa today P. samoensis is much less numerous than P. tonganus (Craig et al. 1994), the extirpation of one of the two large (0.3-0.5 kg) canopy-roosting bats on 'Eua is difficult to explain without invoking cultural prey preference or severe prehistorical reduction in primary forest (on which the regional endemic P. samoensis appears more dependent). Behavioral observations (Wilson and Engbring 1992; Pierson et al. 1996) of P. samoensis and P. tonganus do not suggest differential vulnerability to hunting methods traditionally used by Polynesians. Historical and Recent Extinctions and Extirpations Several bat species, collected on Indo-Pacific islands after the onset of European exploration, are either extinct or locally extirpated (Table 23.2). For those first collected in the nineteenth century, the record is frequently enigmatic. There are usually one or a few specimens with uncertain provenance, and natural history descriptions provide no clues on the course and causes of decline. Similar events in the twentieth century are sometimes better documented, so that ecological traits which made them (and presumably other extant species) vulnerable can be identified. The nineteenth-century demise of Pteropus subniger on both Mauritius and Reunion (with the larger Pteropus niger extirpated on Reunion, but still extant on Mauritius) is well documented (Cheke and Dahl 1981). Both species were initially so common that plans were made to export rendered bat oil. This study suggested that the extinction of P. subniger was linked to its unusual roosting habits. While most Pteropus species for which roosting habits are known cling externally to tree branches (Pierson and Rainey 1992), P. subniger roosted in aggregations as many as 400 individuals in tree cavities and rock crevices, where it was highly vulnerable to collection (Cheke and Dahl 1981). Risks to this species likely intensified as more forest was cleared. The fate of P. subniger suggests we should pay particular attention to other species with similar roosting habits. Review of museum records and recent field studies indicates that cavity roosting may be more common than was previously realized among smaller, little-known Pteropus. For example, Pteropus vetulus on New Caledonia is one of several extant species that resembles P. subniger in having short, furred ears which barely protrude above a dense, woolly pelage. Information on specimen tags at the American Museum of Natural History indicates several P. vetulus were captured from a hollow tree limb at 1,200 m elevation. Conservation of Remote Indo-Pacific Island Bats 329 Table 23.2 Historical Extirpations and Extinctions of Indo-Pacific Island Bats Date of extinction or Locality Species extirpation Probable cause Comments Source" Mauritius, Pteropus subniger ca. 1870, 1860 Hunting; habitat Aggregated tree roosts Cheke and Dahl 1981 Reunion alteration vulnerable Reunion Pteropus niger Extirpated Hunting; habitat Persists on Mauritius Cheke and Dahl 1981 before 1801 alteration Reunion Scotophilus borbonicus Late 19 th Unknown; habitat Taxonomic status uncertain; Cheke and Dahl 1981 century? alteration extensive possible species persists; two other extant Microchiroptera Okinawa, Ryukyu Pteropus mariannus After 1849 Unknown; habitat Two specimens; Andersen 1912; Island loochoensis alteration extensive; P. dasymallus persists K. Koopman, personal locality error communication; possible H. Ohta, personal communication Palau Pteropus pilosus After 1874 Unknown; habitat Two specimens; large bat; Andersen 1912; Wiles 1997 relatively intact P. m. pelewensis persists Tobi, Palau Pteropus mariannus After 1908 Hunting? Persists elsewhere in Palau Wiles 1997 pelewensis Nendo, Solomon Nyctimene ca. 1900 Unknown; possibly One specimen; no Flannery 1995 Island sanctacrucis habitat alteration contemporary natural history data Panay, Philippine Acerodon lucifer After 1892 Habitat alteration; Persisted in periphery of Utzurrum 1992 Island hunting agricultural landscapes Addu Atoll, Pteropus hypomelanus After 1922 Unknown; possibly a One specimen; no Hill 1958; Holmes 1994 Maldives maris waif or locality error contemporary natural history data; P. giganteus ariel persists Guam Pteropus tokudae After 1968 Uncertain; habitat Three specimens Wiles 1987a alteration; bat hunting Negros, Dobsonia chapmani After 1964 Foraging habitat Mortality from guano Heaney and Heideman Philippine clearance; hunting; mining and hunting 1987 Island roost disturbance in the caves Kashoto Island, Pteropus dasymallus After 1986 Hunting; habitat — H. Ohta, personal Taiwan formosus alteration communication "Species accounts for all except Scotophilus borbonicus are in Mickleburgh et al. (1992). In contrast to earlier reports (Sanborn and Nicholson 1950) in which Pteropus ornatus was common and P. vetulus rare, Flannery (1995) recently found that P. vetulus was common in subcanopy mist net captures, despite intensive local bat hunting. Supposing that cavity roosting is common for this species, a key difference from the Mascarene species may be that New Caledonian bats have recently been hunted by spotlighting and shooting, often at night from vehicles (A. Bauer, personal communication). With this method, cryptic aggregated roosts and strict nocturnality may in fact reduce vulnerability to hunters. Flannery (1995) also reported a tree-cavity colony of about 30 Pteropus admiralitatum on Malaita, Solomon Islands, and noted the Moluccan Pteropus caniceps roosts as pairs in tree hollows. Flannery (1995) also suggested that all members of the little-studied genus Pteralopex may roost in tree cavities. He reported that an unnamed Pteralopex in lowland New Georgia and Vangunu, Solomon Islands, roosts communally in cavities of large trees and is easily captured by hand. Flannery also described how this species was observed flying away from areas of logging on Kolombangara and has not been seen there since the mid-1970s. In lowland forests now subject to intensifying timber management or other activities that truncate the age structure of trees, bats which 330 W. E. RAINEY depend on large hollow trees are certainly more vulnerable than those that roost in canopy foliage. Acerodon lucifer, from Panay, Philippines, was last collected in 1892 from the margins of agricultural areas (Utzurrum 1992). The clearance of land on Panay has now reduced forest cover to 10%, with residual forests confined primarily to ridges. Extensive hunting and habitat loss have presumably led to the extinction of A. lucifer (Mickleburgh et al. 1992). Dobsonia chapmani, an aggregated cave-roosting species, was still common on southern Negros, Philippine Islands, in 1964 (Heaney and Heideman 1987). In later surveys these authors concluded that rapid clearing of foraging habitat in lowland forest near cave roosts, along with disturbance and mortality from guano mining and hunting in the caves, caused extinction before 1981. Reasons for the recent decline and presumed extinction of Pteropus tokudae on Guam are obscure (Wiles 1987a; Mickleburgh et al. 1992). When discovered, this small species was very rare relative to the sympatric Pteropus mariannus mariannus. Two specimens were collected in 1930, and a third was 1 of 100 bats shot during the hunting season of 1968. Remaining forest habitat on Guam, although heavily altered, could probably still support many more than the several hundred P. m. ariannus currently on the island. Rapid population increase of Boiga irregularis, the predatory arboreal snake introduced after World War II, postdates the disappearance of P. tokudae (Wiles 1987a; Rodda et al. 1992). This species is not known from the adjacent, less disturbed island of Rota or elsewhere in the Marianas, despite repeated surveys (G. Wiles and D. Worthington, personal communication). Pteropus dasymallus formosus, which persisted until at least 1986 on Kashoto, an offshore island of Taiwan, is apparently the most recent extinction of Pteropus. Several other subspecies of P. dasymallus in the Ryukyus barely survive (Mickleburgh et al. 1992; H. Ohta, personal communication). Forest cover on Kashoto has been greatly reduced by agricultural conversion, but the ultimate cause of extinction is likely hunting for food. Kuroda (1933) concluded that historical specimens of P. d. formosus from localities on Taiwan (Andersen 1912) originated elsewhere, but no zooarchaeological surveys are available to test this hypothesis. Inventory, Status Assessment, and Population Monitoring Inventory Scientific knowledge of many bat species, particularly in the more diverse faunas of the southwest Pacific, has often been limited to their taxonomic description based on a few specimens. Early bat collections were frequently incidental to bird sampling, and thus inventories were incomplete. With accelerating habitat alteration in recent decades, the continued existence of species on small islands, especially those dependent on lowland forest areas, has been an open question. Partly from concern for the potential loss of biodiversity, the museum tradition of faunal inventories has been renewed, especially by the Australian Museum, the Western Australian Museum, and regional collaborators. From these surveys Flannery (1995) has reported recent collections of many of the little-known Pteropus from the southwest Pacific (e.g., P. chrysoproctus, P. jundatus, P. mahaganus, P. melanopogon, P. nitendiensis, P. ocularis, P. pohlei, P. rayneri cognatus, and P. temmincki). These surveys also yielded two new species (one discussed earlier) of Pteralopex from the Solomon Islands (Flannery 1991, 1995). On Guadalcanal, Pteralopex pulchra is unusual in that it appears restricted to high, mossy, montane forest, where it replaces the (now declining) lowland species Pteralopex atrata. The wet, high-elevation habitat is analogous to that of the rare Fijian endemic, Pteralopex acrodonta (Hill and Beckon 1978; also recollected by Flannery 1995). In Fiji, however, no lowland Pteralopex species is known. Status Assessments and Population Monitoring Several surveys that have assessed the status of bat populations postdate the megachiropteran compilation by Mickleburgh et al. (1992). A 1991 survey of bats in Palau found that Pteropus mariannus pelewensis, formerly very heavily hunted for commercial export to the Marianas, was common to abundant at 40% of 54 evening census localities and that Pteropus pilosus is almost certainly extinct (Wiles et al. 1997). Grant (1994) observed Pteropus tonganus on the isolated island of Niue, and obtained local estimates that 1,200-5,000 individuals are taken annually by shooting, suggesting a much larger population than previously reported. In reviewing the distribution and current status of bats known from Tonga, Koopman and Steadman (1995) reported at least 2,400 P. tonganus on 'Eua and several thousand at Kolovai, Tongatapu, in 1988. Holmes (1994) described Pteropus giganteus ariel in the Maldives as widespread, but not numerous, and subject to lethal control efforts intended to reduce fruit depredation. Surveys conducted over several years for Pteropus livingstonii, the rarer of the two Pteropus species in the Comores, yielded minimum population estimates of 380 on Anjouan and 60 on Moheli (W Trewhella, personal communication). Reason and Trewhella (1994) noted that the primary threat to this species is habitat loss as forest fragments are converted to agricultural use to support a rapidly growing human population. Pteropus livingstonii currently roosts in Conservation of Remote Indo-Pacific Island Bats 331 the canopy of montane forest patches on steep slopes and relies more extensively on native fruits for food than the other Pteropus species, Pteropus seychellensis comorensis. Netting efforts to collect P. livingstonii for an ex situ captive breeding program incidentally captured more than 150 Rousettus obliviosus, a third little-known pteropodid (Reason et al. 1994). In more affluent American Samoa, human population growth is comparably rapid, deforestation of limited lowlands is well advanced, and clearing of steeper slopes is ongoing. However, the major factor affecting recent population trends for P. tonganus and P. samoensis has been mortality, largely from hunting, rather than habitat limitation. Craig et al. (1994) has summarized the results of roost counts and diurnal surveys, which began in 1987 on Tutuila after local legislation was enacted to halt commercial export of bats to the Marianas (see following). These authors showed that bat counts dropped precipitously following a cyclone in 1990. While some bats died or starved, increased opportunistic hunting was the primary cause of postcyclone mortality. Hunters reported double the typical annual harvest in the year following that storm. A second severe cyclone less than 2 years later compounded effects on bat populations. Craig et al. (1994) estimated an 80%-90% population decline for both species over 5 years and tentatively concluded that 200-400 P. samoensis and 1,500-2,500 P. tonganus were on the island in late 1992. Diurnal roost counts of P. tonganus on Tutuila have shown a steady increase from 1,700 in 1991 to 5,700 in 1996. Radiotracking indicates that diurnal flight observations underestimate P. samoensis numbers, which may be closer to 1,000 (A. Brooke, personal communication). Perhaps partly as a consequence of continued illegal hunting, roosts for both species are concentrated on steep forested slopes in undeveloped areas. A substantial area of forest is contained within the recently established National Park of American Samoa, but this may not be adequate to maintain viable populations of bats and other wildlife if forest clearance in other areas continues at the current rate. A study conducted in Western and American Samoa found differences between the two Pteropus species in response to a postcyclone reduction in food availability (Pierson et al. 1996). The less abundant, regionally endemic P. samoensis remained in the forest, initially feeding largely on leaves, while the more widespread P. tonganus foraged extensively on residual or fallen fruit in inhabited areas and experienced higher mortality from human hunters and predation by domestic animals. This study found that forest reserves on Savai'i, Western Samoa, appeared to protect small numbers of P. samoensis because their limited diurnal foraging movements remained within the reserve where hunting was banned. Pteropus tonganus frequently flew outside the reserve to feed and was likely subject to heavier hunting pressure. The remnant P. mariannus mariannus population on Guam, usually found roosting as a single colony on a U.S. military base (a de facto reserve), has been monitored since 1981 (Wiles et al. 1995). These authors reported seasonal fluctuations in population size, with 200-400 animals present from June to September and 400-750 from November to February. Wiles and Glass (1990) reported observations of offshore bat flights among the Marianas and used changes in colony size to infer interisland group movements, including several (60 km over the ocean) between Guam and Rota in the Commonwealth of the Northern Marianas (CNMI). Wiles et al. (1995) suggested that the seasonal fluctuations in bat numbers on Guam reflect annual movement between the two islands. Predation on nonvolant juvenile bats by the introduced snake Boiga irregularis apparendy prevents local recruitment (Wiles 1987b), so that the persistence of the Guam population could depend on movement from Rota. Historically, bats were heavily hunted on Guam, but poaching has not been a threat to the resident bat colony in recent years (G. Wiles, personal communication). Guam is an unusually affluent, regional transportation hub with rapidly expanding tourist facilities and related infrastructure. In 1993, the U.S. government created a wildlife refuge from relatively intact forest on military lands. While this has met with some local support, there has also been considerable resistance, based partly on pre-World War II private land claims to these areas (Wiles 1994). In addition to development pressures, remaining forest areas are subject to ongoing degradation by introduced ungulates (Wiles et al. 1995). Rota harbors the only substantial population of P. mariannus in the southern islands of the CNMI (Stinson et al. 1992). Estimates of bat numbers on Rota from 1986 until a major cyclone in January 1988 were 2,000-2,500. Subsequent counts dropped to approximately 1,000, owing to postcyclone hunting and possibly emigration. The population has remained at this lower level through 1995, probably because of chronic illegal hunting (Worthington and Taisacan 1996). Wiles et al. (1989) surveyed the less-developed islands north of Saipan and estimated that 7,450 bats were present in 1983. Illegal market hunting has since increased. Also, a survey of Anatahan identified rapidly growing feral goat populations as a serious new threat to forest habitat (Marshall et al. 1995). The CNMI has a regulatory framework for achieving sustainable bat harvest, but public and institutional resistance to restrictions on bat hunting and trade are strong. Habitat conservation areas have been out- 332 W. E. RAINEY lined, but enforcement of local wildlife laws remains minimal. Wiles and Glass (1990) suggested, as a way to rationalize the varied taxonomic and regulatory status of populations on different islands, that all P. mariannus in the southern Marianas should be managed as a single unit. Recent reports of Emballonura semicaudata, the only microchiropteran bat in much of Micronesia and Polynesia, suggest that a patchy, rangewide decline is in progress. At the eastern limit of its current range in Polynesia, Grant et al. (1994) reported a rapid reduction of E. semicaudata to only a few individuals in American Samoa. They noted that similar declines, from hundreds or perhaps thousands of bats to isolated individuals, seem to have occurred contemporaneously for colonies on Upolu, Western Samoa. These declines lag by decades similar changes for populations of E. semicaudata and cave swiftlets (Collocalia vanikorensis) in Guam and adjacent islands in the CNMI (Lemke 1986; Steadman 1992). In Samoa, however, swiftlet populations that share caves with E. semicaudata have remained stable or increased. Grant et al. (1994) discussed the role of a severe cyclone in the reduction of E. semicaudata populations in American Samoa, but did not link the long-term declines to the explanations offered for the Marianas—military destruction of caves, extensive pesticide use for vector control, and guano mining. Recent surveys in the Marianas have generally confirmed a pattern reported by Lemke (1986) suggesting that E. semicaudata is extinct on Guam and Rota and absent on all other islands, except Aguiguan (no human inhabitants) and perhaps Saipan (Wiles et al. 1995; Worthington and Taisacan 1996). Island-by-island patterns of persistence for bat and swiftlet populations in the Marianas are also not congruent (D. Worthington, personal communication). Flannery (1995) related a long-term resident's report of similar declines of E. semicaudata on Viti Levu, Fiji, from abundance in the 1950s to virtual absence in the 1990s. The informant attributed declines to roost disturbance and the burning of forests near caves. Flannery (1995) also reported a small colony of E. semicaudata residing in an inaccessible cave roost on Taveuni, Fiji, presumably in the 1990s. This species may have also declined on the isolated island of Rotuma, Fiji. Clunie (1985) reported the bats as present in multiple thousands in caves and observed foragers "in far larger numbers than is usual in Fiji." In 1993-1994, Cox (personal communication) visited Rotuman caves several times and noted a marked reduction in numbers, consistent with reports offered by local residents. In surveys of more than 50 caves on 'Eua, Tonga, in 1988-1989, only a single colony of 25 E. semicaudata was observed (Koopman and Steadman 1995). In several other areas of Micronesia, E. semicaudata has been recently present. Wiles and Conry (1990) reported a cave colony of 200 in Palau. Observations at multiple sites in Palau in 1991 showed the species to be widespread and common, with foraging movements by several thousand bats observed (G. Wiles, personal communication). In 1989, tens of foraging E. semicaudata and swiftlets were also seen at dusk over the streets on Moen Island, Chuuk, but, as observed earlier by Bruner and Pratt (1979), this species is considerably less common on Pohnpei (Rainey, unpublished observations). A common cause for these seemingly parallel declines is not evident. Both the southern Marianas (with few bats) and Palau (with many) share a history of intense military activity during World War II and former use of DDT for insect control (Baker 1946), but the Marianas have few bats and Palau has many. Unlike the Marianas, Palau has numerous small outlying karstic islands that likely offer more extensive bat refuges. Chronic roost disturbance is a welldocumented cause for declines in cave-dwelling bats, especially at sites close to concentrations of humans and domestic or feral animals. Colonies of E. semicaudata persist, however, close to habitations on densely populated, heavily altered Moen, Chuuk, and are declining on much larger, less densely populated islands such as Viti Levu, Fiji, and Upolu, Western Samoa. Introduced pathogens, which are apparently responsible for declines of native Hawaiian birds in relatively intact habitat (Atkinson et al. 1995), offer another possible mechanism. Resources for wildlife conservation often focus on charismatic, endemic "flagship" species, but the regional decline of this small insectivorous bat deserves careful scrutiny. Systematics and Molecular Genetics In the 1980s, use of protein electrophoresis in surveys of Australian Microchiroptera revealed or confirmed numerous well-differentiated sibling species and sometimes considerable geographic differentiation within species (Adams et al. 1982; Baverstock et al. 1987). More recent populationand species-level surveys of Pacific pteropodids, using several molecular techniques, offered contrasting results with both evolutionary and management implications. For example, protein electrophoresis of Cynopterus populations in Indonesia revealed relatively small genetic distances among species and little evidence of geographic differentiation within islands, suggesting the ocean is the primary barrier to gene exchange (Schmitt et al. 1995). Peterson and Heaney (1993) compared Haplonycteris fischeri, a Philippine endemic restricted to primary forest, and populations of the wide-ranging Cynopterus brachyotis in the Philippines Conservation of Remote Indo-Pacific Island Bats 333 and noted higher levels of genetic differentiation among populations of H. fischeri. In contrast, Kitchener et al. (1993) used electrophoretic analysis to examine variation, on several Indonesian islands, in Aethalops alecto, a small pteropodid restricted to montane forest. They concluded that populations were neither well differentiated nor genetically isolated. An extensive study of the highly migratory Australian flying-fox, Pteropus scapulatus, using both allozymes and random amplified polymorphic DNA, showed low levels of population structure and indicated that this species, now independently managed by several jurisdictions, was effectively panmictic (Sinclair et al. 1996). Webb and Tidemann (1996) reported similar results for Pteropus alecto and Pteropus poliocephalus and suggested they should be managed as migratory species. Their analysis of putative hybrids from areas of sympatry revealed only one or two fixed alleles in 23 loci differentiating P. alecto from P. poliocephalus or Pteropus conspicillatus, which suggests relatively recent divergence among these species (Webb and Tidemann 1995). The low levels of intraspecific differentiation in Pteropus and Cynopterus suggest that populations of Pteropus (or other largeto moderate-sized unspecialized pteropodids) on small oceanic islands can generally be viewed as single management units. The inference that P. mariannus regularly crosses as much as 60 km of ocean (Wiles and Glass 1990; Wiles et al. 1995) highlights the need to use molecular approaches to identify appropriate management units in species that lack obvious morphological discontinuities and whose ranges encompass multiple islands separated by significant water gaps. While the description of new species and subspecies of smaller pteropodid and microchiropteran bats from the more diverse communities of the western Pacific has continued to the present (Kitchener et al. 1994), higher-level megachiropteran systematics has remained essentially that of Andersen (1912), which is inexplicit by modern standards. Mickleburgh et al. (1992) presented a conservation ranking scheme for geographic areas that incorporated weights for both "taxonomic distinctiveness" and species richness using a morphologically based cladogram of megachiropteran genera (by J. E. Hill; but see also Heaney 1991). More recently, Colgan and Flannery (1995), Kirsch et al. (1995), and Springer et al. (1995) presented independent molecular data sets on megachiropteran systematics. While these inevitably differ, they are consistent with some earlier morphological and biochemical studies (Hood 1989; Haiduk 1983) in one major finding: the morphologically specialized nectar-feeding genera, historically grouped in the subfamily Macroglossinae, are not a clade. With new tools and renewed interest in this topic, we can expect a gradual consensus on phylogenetic relationships that will provide new criteria for conservation ranking schemes. Threats to Bat Populations Among declining vertebrate species, one can make a heuristic division between those that are lost with their habitat and those that vanish long before their habitat. The latter are usually animals that are either large (e.g., sirenians) or are selectively hunted for their perceived high value to humans (e.g., musk deer, birds with unusual plumes). Although bats have relatively small body mass and might be expected to closely track habitat loss, low reproductive output and, for some species, aggregated roosting habits at traditional sites make them vulnerable to selective hunting. Loss or degradation of forest habitat is clearly an important threat to the long-term persistence of bat populations on islands. The relative importance of habitat loss, exploitation, and other factors in determining population trends is however quite varied among islands and generally is poorly known. A few of the more discrete threats to island bat populations are discussed next. International Trade Partly as a consequence of the large body size of some Megachiroptera (and the limited array of animals available on isolated oceanic islands), human consumption of bats is a significant factor affecting bat populations on Indo-Pacific islands and in adjacent areas of Asia. Attitudes toward bats as food vary across religions, cultures, and geography (Kirch and Yen 1982; Fujita and Turtle 1991). In Micronesia, for example, residents of both the Marianas and Yap have a long tradition of consuming bats. In the Marianas, they are highly favored (Sheeline 1991), while in Yap they are "not esteemed" (Falanruw and Manmaw 1992). To the east in Chuuk and Pohnpei, bats are viewed as somewhat repellent and are generally not part of the local diet (Rainey, unpublished observations). The major focus for international trade in bats (primarily Pteropus spp.) has been Guam and the adjacent CNMI. Wiles (1992) summarized trade history and tabulated legal imports, showing that subsequent to local depletion bats were initially acquired from nearby islands. In the 1980s the radius of trade expanded, reaching as far as Papua New Guinea and the Philippines. The mean number of bats recorded as imported to Guam in 1981-1989 was roughly 13,000 annually (Wiles 1992). The mean number of bats imported annually into the CNMI in 1986-1989 was 3,300 (Stinson et al. 1992). In some instances, small islands such as Yap and American Samoa noted rapid declines in Pteropus 334 W. E. RAINEY populations and imposed local restrictions on export hunting (Craig and Syron 1992; Falanruw and Manmaw 1992). In 1989, seven central and west Pacific small island Pteropus species were added to Appendix I of the Convention on Trade in Endangered Species of Wild Flora and Fauna (CITES), while the remaining species of Pteropus and all species of the allied genus Acerodon were placed on Appendix II (Braiitigam and Elmqvist 1990). This listing obliged countries who were parties to the treaty (including the United States) to cease international trade in Appendix I species and monitor trade in Appendix II taxa. After enforcement of CITES provisions on Guam in 1990, legal imports from 1990-1993 came from Palau, which was still under U.S. jurisdiction (annual mean: for Guam, 7,688 bats; for CNMI, 5,755) (Wiles et al. 1997). This practice continued until late 1994 when Palauan independence ended legal trade in Pteropus mariannus pelewensis. Also in 1994, Acerodon jubatus and Acerodon lucifer (the latter probably extinct) were transferred to Appendix I, based on a petition from the Philippines, which emphasized ongoing illegal trade into Guam and CNMI. Subsequent to closure of the legal trade from Palau, documented imports have essentially ceased and prices within CNMI have risen to more than US$50 per bat (Worthington and Taisacan 1996). It is generally presumed that, as a response to market forces, illegal hunting has increased in the northern Marianas, and that some international smuggling also occurs (Wiles 1994; Worthington and Taisacan 1996). No legal barrier exists to commercial imports of Appendix II or unlisted species from a number of countries. There are, however, practical barriers, such as market reluctance to accept unfamiliar species, complications regarding trade arrangements, and the risk of flight delays spoiling highly perishable cargo. In the past, local preference for large, strongly scented Pteropus with few parasites led to preferential market hunting and pricing. For example, buyers visiting Samoa preferred the less common P. samoensis to P. tonganus. Smaller Pteropus from Palau and the Federated States of Micronesia (FSM) were initially of less interest. Acceptance of smaller cave-dwelling pteropodids with obvious tails (e.g., Rousettus) was also poor (G. Phocas, personal communication; Sheeline 1991; D. Worthington, personal communication). Reemerging proposals to import Rousettus from mainland Asia or Pteropus from Australia (G. Wiles, D. Worthington, personal communication) increase the risk that people who prepare frozen bats would be exposed to lethal pathogens, such as lyssaviruses, which are present in at least some species of Australian Pteropus (Fraser et al. 1996; Young et al. 1996). Although these risks may not alter the behavior of individual consumers, public health authorities will be obliged to reinterpret import regulations for vectors of communicable diseases to allow international trade to expand along these lines. The only recurring international trade outside of the Marianas for bats listed on CITES involves a few hundred Pteropus exported annually from Vanuatu to New Caledonia (J. Caldwell, personal communication). Introduced Predators Although introduced predators have had a serious impact on island biotas (Atkinson 1989), they have not generally been implicated as the primary agents in the long-term declines or extinction of island bats. A notable exception is the fate of two species endemic to New Zealand, Mystacina robusta and Mystacina tuberculata. The last known population of M. robusta went extinct during an irruption of Rattus rattus in the mid-1960s (Daniel 1990). Also, a key role can be inferred for rats and other introduced predators in the extensive range contraction of both species throughout New Zealand (Daniel and William 1984; Daniel 1990). The tendency for Mystacina species to roost and forage close to the ground may account for their differential vulnerability (Daniel and William 1984). Even though rats (especially R. rattus) and feral cats commonly climb trees and rock surfaces, bats roosting in tree canopies, in bole cavities, and on the ceilings of caves have managed to coexist with these predators in most settings. Their ability, lacking in birds, to move threatened nonvolant young has likely helped. On Christmas Island in the eastern Indian Ocean, Tidemann et al. (1994) found that the canopyroosting endemic Pteropus melanotus natalis was vulnerable to feral cat predation when individuals foraged near the ground in fruiting shrubs. Limited observations of a second endemic, Pipistrellus murrayi (included in Pipistrellus tenuis by Koopman 1993), showed that it forms small groups in trees rather than caves (Tidemann 1985). Despite these introduced predators and considerable hunting of flyingfoxes by humans, both bat species were present in substantial numbers in the 1980s (Tidemann 1985; Tidemann et al. 1994). However, as discussed for Samoa, single tropical cyclones can sharply increase the short-term vulnerability of canopy frugivores and nectarivores to introduced terrestrial predators. The best-documented example of an introduced nonhuman predator reducing island bat populations is Boiga irregularis, an arboreal Australasian snake on Guam. Probably arriving in post-World War II military shipments from the Admiralty Islands, this snake slowly increased to high density, eliminating most of the island's avifauna and apparently preventing local recruitment in Pteropus mariannus Conservation of Remote Indo-Pacific Island Bats 333 (Savidge 1987; Wiles 1987b; Rodda et al. 1992; Wiles et al. 1995). Extensive investigations, including control and containment methods, suggested that this snake will persist on Guam indefinitely (McCoid 1991), leaving long-term prospects for the local bat population in doubt. Guam is a regional center for military transport, and individuals of B. irregularis have been recovered on Saipan, Kwajalein, Oahu, and Diego Garcia (McCoid 1991). Because it is likely that dispersal will continue and that vigilance on islands receiving shipments may not always be sufficient, research on emergency eradication methods is important (McCoid 1991). Investigations of reproduction in Australian B. irregularis indicated that sperm storage may enhance its success as an invader (Whittier and Limpus 1996). Greene's (1989) observations on the diet and habits of other Boiga spp. suggested that they too pose serious invasion risks. Differences that permit coexistence between Boiga and Pteropus in portions of their natural range are unknown, but it is likely that snake densities are lower. A nocturnal, commensal snake from southeast Asia, Lycodon aulicus, which was first detected on Christmas Island in 1987, now appears established (Fritts 1993). Its maximum reported size (84 cm total length [TL]; Fritts 1993) and limited gape (H. Greene, personal communication) make predation on adult P. m. natalis highly improbable. Its broad dietary habits and arboreality suggest that it may, however, be a major threat to the survival of the much smaller Pipistrellus murrayi. A scenario, similar to that observed in Guam, of high snake densities causing the extinction of indigenous vertebrates of lower fecundity, including bats, is likely unless this snake can be quickly eliminated. Another possible instance of an introduced predator having an impact on an island bat population is the decline of Coleura seychellensis. Racey and Nicoll (1984) outlined a history of reports, indicating that the species was "very common" in 1868 and reduced to 16 individuals in their recent surveys. Suggested causes of decline are loss of forest habitat, human disturbance of roosts, and occupancy of roost caves by barn owls (Tyto alba). Barn owls were introduced to the Seychelles in 1949 (Cheke and Dahl 1981), and have been shown elsewhere to be significant predators on insectivorous bats (Speakman 1991). Mass Mortality from Disease Anecdotes of introduced diseases decimating island vertebrates are not uncommon (Simberloff 1995), but only recently has there been recognition that mass mortality from pandemic disease is a rare but widespread phenomenon among Pacific island flying-fox populations in the postEuropean-contact era (Flannery 1989, 1995; Pierson and Rainey 1992) (Table 23.3). Perhaps because such events might go undetected (or not occur) in less-colonial species, reports all concerned Pteropus, which form large aggregations at traditional roosts. Descriptions are dramatic, with incapacitated bats falling from the sky and carcasses or bones accumulating in piles at roost sites (Coultas 1931; Degener 1949; Flannery 1989). Few or no bats of the affected species were seen after epidemics, and, consistent with the population biology of Pteropus, recovery is reported as slow (Stair 1887; Flannery 1989, 1995). The two oldest reports link these events to simultaneous epidemics in humans or domestic animals (Stair 1887; Coultas 1931). As Flannery (1989) pointed out, high mortality favors the hypothesis of a human-introduced pathogen to which bats had no prior exposure. Again by analogy to Hawaii, because few bats that come into contact with humans are later released, transfer of pathogens to forest-dwelling bats tenTable 23.3 Mass Mortalities of Pteropus from Disease on Indo-Pacific Islands Locality Samoa Kosrae (FSM) Vanua Levu, Fiji New Caledonia Manus, Papua New Guinea Bougainville and Buka, Solomon Island Species Date P. tonganus and/or P. samoensis P. mariannus ualanus P. tonganus P. ornatus P. neohibernicus hilli P. rayneri grandis Comments 1839 Prior epidemic among residents; gradual bat population recovery; species not identified 1926-27 Measles and dysentery epidemic in residents; thousands of bats died; few survivors Before 1949 Hundreds dead under roosts Early 1960s Formerly common; no subsequent population recovery under hunting pressure 1985 Masses dead in roost areas; slow recovery; sympatric P. admiralitatum unaffected; unaffected P. neohibernicus on adjacent islands 1987 Unaffected populations on adjacent islands Source Stair 1887 Coultas 1931 Degener 1949 Flannery 1995 Flannery 1989 Flannery 1989 336 W. E. RAINEY tatively suggests an arthropod or other animal vector. The lack of evidence for recurrent mass mortalities from disease in better-studied temperate zone bat populations suggests that these events are not part of the prehuman evolutionary history of island bats. However, birds transport pathogens and arthropod vectors with broad host ranges to islands (Olsen et al. 1993). Interisland transportation by humans continues to improve, increasing the prospect of dispersing microbes, arthropod vectors, and alternate hosts. Any new bat epidemic that is detected deserves careful study, given the risks of stochastic mortality to the long-term persistence of small populations. Global Climate Change Current models of global warming suggest that oceanically buffered climates in tropical regions are expected to show small increases in temperature (Lighthill et al. 1994), the consequences of which are unknown for island vertebrates. Two other projected changes, rising sea levels and altered cyclone regimes, would however almost certainly have major impacts on island biotas. In the absence of local tectonic uplift, sea level rise threatens current terrestrial communities on low-relief atolls, which account for many of the world's remote oceanic islands. On such islands, relatively large areas of land would be lost with only a small rise in sea level (17-26 cm by 2030 and increasing thereafter). The decreasing lens of fresh groundwater and increased effects from salt spray would also affect vertebrate consumers because decreasing plant diversity will reduce food resources (Roy and Connel 1991). Roy and Connel (1991) discussed prospects for humans who inhabit nations composed largely of atolls (e.g., Kiribati or Maldives), concluding that the current pattern of economic emigration will likely be transformed during the next several decades into an exodus of environmental refugees. For countries (e.g., FSM, Cook Islands) that include both scattered low atolls and uplifted carbonate or emergent volcanic islands (typically with greater population and infrastructure), this migration may be partly internal but will increase human density and demand for natural resources on already crowded islands. A few bat species and populations endemic to low-relief atolls would be directly threatened by rising sea levels (e.g., Pteropus hoxvensis on Ontong Java; P. mariannus ulthiensis on Ulithi; the P. insularis population on Namonuito Atoll, FSM (Rainey and Pierson 1992); P. phaeocephalus in the Mortlocks, FSM; P. giganteus ariel in the Maldives). Several other species (e.g., P. tonganus in Fiji and Tonga, P. insularis on Chuuk, P. mariannus subspp. in Yap and Palau) occur both on highand low-lying islands and thus are less acutely threatened. However, at a scale of a few kilometers, lost or altered vegetation will eliminate foraging habitat and refuges from human hunting. At a scale of many kilometers, the distribution of even small numbers of bats and patches of foraging habitat over several islands offers escape in space and time from the recurring but relatively narrow paths of tropical cyclones. The risk of extinction increases as the total geographic range of a species declines toward an area potentially swept by cyclones in a high-frequency year. Mangrove forests are recognized as an important coastal habitat for bats, especially Pteropus. They provide relatively protected sites for aggregated roosting (e.g., P. vampyrus on Timor [Goodwin 1979], P. molossinus on Pohnpei, and P. mariannus ualanus on Kosrae [Rainey 1990]), with some common trees, notably Sonneratia, seasonally offering an important nectar resource (Start and Marshall 1976). Inputs of sediment from major rivers may allow mangrove forests on continental coastlines to keep pace with projected sea level rise (Jelgersma et al. 1993). On small islands where terrestrial inputs to coastal sediments are much lower, sea level rise, in the absence of tectonic uplift, will exceed soil accretion in mangrove forests, making forest death a likely scenario (Ellison and Stoddart 1991). An altered tropical cyclone regime could be a major consequence of global warming. These cyclic disturbances play a key role in shaping forest structure and species composition, and, for low-lying islands, they can alter coastal geomorphology (Whitmore 1974; Shaw 1983; Tanner et al. 1991; Stoddart and Walsh 1992; Elmqvist et al. 1994; Foster and Boose 1995). Marked reductions in bat populations, followed by deferred reproduction, accompany severe cyclones (Cheke and Dahl 1981; Wiles 1987a; Pierson and Rainey 1992; Stinson et al. 1992; Craig et al. 1994; Gannon and Willig 1994; Grant et al. 1994; Pierson et al. 1996). Increased cyclone frequency or intensity would bode ill for the long-term persistence of low-fecundity vertebrate populations on small islands. Assuming higher surface temperatures for tropical seas, as predicted by global climate models, several studies have projected increases in the maximum intensity, mean intensity, frequency, and latitudinal range of tropical cyclones and modeled their biological or economic consequences (Emanuel 1987; Gable and Aubrey 1990; O'Brien et al. 1992). This is a controversial topic. A recent review suggested that the latitudinal range of cyclones will not increase and that current climate models cannot evaluate what will happen to frequency or average intensity of cyclones (Lighthill et al. 1994). Some investigators, however, have argued strongly that maximum possible intensity will increase (Emanuel 1995). Reanalysis of relatively detailed cyclone data for the North Atlantic, Caribbean, and Gulf of Conservation of Remote Indo-Pacific Island Bats 337 Mexico shows a significant decline in maximum intensity during the past 50 years (Landsea et al. 1996). Conclusions The zooarchaeological record of remote Indo-Pacific islands, which is drawn largely from limited samples in the less-diverse faunas of Polynesia, shows that bats of the genus Pteropus generally survived extensive prehistorical defaunation. Their survival relative to ground-nesting seabirds or numerous extinct flightless endemic land birds is not surprising. However, survival of bats relative to smaller, canopy-dwelling, nectarivorous or frugivorous birds likely reflects widespread cultural preferences for hunting birds, combined with the high vulnerability of avian eggs and young to predators. Extinctions and extirpations of island bats, from the prehistoric to the present, include many that are too poorly documented to interpret. Several losses and declines, however, underline the vulnerability of bats to overhunting (even with limited technologies), especially those species that roost colonially in caves or tree cavities. Endemic taxa that rely on lowland or lower montane primary forest have undergone substantial population reductions with forest clearance. Yet, in areas where bat hunting is not intense, several species have persisted, albeit at low numbers, on islands with high human densities. Several such species, now confined to dwindling forest fragments, are being aided by conservation intervention. Especially on atolls, traditional agricultural practices on islands, which emphasize tree crops, may increase the abundance and predictability of fruit resources for bats and thus enhance the carrying capacity for those Pteropus that have catholic diets. Frugivorous bats that roost in secondary forest can often coexist successfully with man so long as their real or perceived impact on fruit crops does not trigger extermination efforts. Recent status assessments suggest that pteropodid populations are highly vulnerable to overhunting, and ready availability of guns is a significant risk factor. Cultural perspectives on bats can play a key role in determining prospects for survival. During the 1970s and 1980s, commercial harvest of bats to supply the traditional luxury food markets in Guam and the Northern Marianas had a pervasive influence on the Pteropus populations on a number of islands in Polynesia and Micronesia. A partial exception to this pattern was that of bat populations in Palau, which declined during one period of commercial hunting but recovered and appeared to remain relatively common during a second, perhaps lessintense period (Wiles et al. 1997). While demand for bats is still high in the relatively affluent Marianas, little legal international trade now takes place. Limited evidence suggests that demand is partially met with bats taken illegally within CNMI under a regime of minimal enforcement. Also, forest degradation by expanding populations of introduced herbivores threatens bat habitat on some islands. Accumulating data on molecular variation in bats from Australia and the Pacific Islands suggest that, for larger habitat generalists, practical management units based on current water gaps among islands will approximate units that would be delineated by genetic surveys. However, some montane forest endemics have shown more withinpopulation genetic variation. Although similar bats in Australasia and elsewhere coexist with a wide range of predators, the introduced arboreal snake Boiga irregularis apparently prevents local recruitment in the Pteropus population on Guam. Guam is a transportation hub, and transport of snakes to other islands has already occurred. Introductions of predators pose a severe threat to the near-term survival of endemic island vertebrates, including bats, even where habitat is still relatively intact. A second threat of uncertain importance, but which can also disperse through intact habitat, is disease. Outbreaks have been documented to cause severe reductions of Pteropus population at several localities. While projected anthropogenically induced climate change is rapid relative to the Pleistocene record of natural climate change, its effects, except for inundation of low atolls, on remote island bat populations will likely be undetectable against the greater magnitude and pace of change induced by human population growth, resource consumption, and habitat alteration. Acknowledgments I thank A. Brooke, E. Pierson, D. Steadman, E. Towle, G. Wiles, and D. 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