The Herpetofauna of Grenada and the Grenada Grenadines: Conservation Concerns

The herpetofauna of Grenada and the Grenada Grenadines: Conservation concerns

Robert W. Henderson1,CraigS.Berg2

1 Section of Vertebrate Zoology, Milwaukee Public Museum, 800 W. Wells St., Milwaukee, Wisconsin 53233-1478, USA 2 Milwaukee County Zoo, 10001 W. Blue Mound Rd., Milwaukee, Wisconsin 53226, USA

Abstract. Grenada and the politically associated Grenadines harbor 19 species of terrestrial herpetofauna, and four species of marine turtles either nest on their beaches or forage in the surrounding waters. The islands have a 2000-year history of human activity, but the past ﬁve centuries had the most adverse impact on the environment. Although some members of the herpetofauna have responded well to dramatically altered habitats (Anolis spp.), others have not (e.g., Eleutherodactylus euphronides). Similarly, the introductions of alien predators (most notably Herpestes javanicus) have likely impacted some species (e.g., Ameiva ameiva, Mabuya sp.), but not others. Several species appear to be genuinely rare (e.g., Clelia clelia, Typhlops tasymicris), and sharp declines in numbers have been documented for the arboreal boa Corallus grenadensis. The future of marine turtles in the area is threatened by habitat destruction (development of beachfront habitat for the tourist industry), slaughter of adults, and poaching of nests. Eco-tourism may hold the key for protection of forested habitats and the herpetofauna of this important group of islands.

Key words: Conservation; frogs; Grenada; mongoose; reptiles.

Introduction

The southernmost of the main islands in the Lesser Antilles, Grenada is situated about 135 km off the northern coast of Trinidad and about 140 km off the northern coast of Venezuela. The island has had a long history of human activity with dramatic effects on the ecology of its herpetofauna. For the vast majority of that time, the impact of humans on the herpetofauna has probably been negligible. The past ﬁve centuries, however, have witnessed tremendous growth of the human population coupled with widespread habitat destruction or alteration. Studying the ecology of any member of Grenada’s herpetofauna without taking into account the impact of human activity is virtually impossible today (e.g., Germano et al., 2003).

Our ﬁeldwork in Grenada commenced in 1988, and since then we have witnessed changes to the island’s landscape and to its herpetofauna.

The Setting Grenada is about 34 km long and 19 km wide, and has an area of 311 km2 (ﬁg. 1). It is a moderately eroded volcanic pile, apparently intermediate in age between young St. Vincent and old St. Lucia. The highest peak, Morne St. Catherine (840 m), rises in the northern half of the island as the center of a massif surrounded by lesser peaks and ridges. South of this peak is a low depression, and beyond it the land rises again into a long, curving ridge (or system of ridges), running ﬁrst to the south and then to the east and northeast. This chain contains numerous peaks and high points (Morne QuaQua 735 m, Mt. Sinai 701 m, and Southeast Mountain 219 m) and embraces several old crater basins, one of which is occupied by the lake Grand Etang. From these central mountains the land descends gradually to the sea. A true coastal plain is missing, but lowlands occur in the northeast at Levera and in the southwest, where a long, low peninsula runs out to Pointe Salines. A large portion of the island has been cleared for cultivation (table 1) due to the small size of the island and the fact that mountain slopes are not excessively steep except at extreme elevations. Orchard crops form the bulk of the cultivations. Because of the gentle topography along most of the coastline, eroded hills covered with thorny scrub are not a common feature except in the extreme south (rough grazing land with Acacia covers most of the Pointe Salines Peninsula). The Grenadine Islands are part of the Grenada Bank (Grenada plus the Grenadines) and are situated between St. Vincent to the north and Grenada to the south, but of the populated islands, only Carriacou and Petit Martinique are politically associated with Grenada; the remainder are governed by St. Vincent. Approximately 120 islands comprise the group, and the composite surface area of the islands is about 130 km2. According to Howard (1952), if the current sea level was lowered 38 m, all of the islands between Bequia and Carriacou would be united. Europeans have inhabited the Grenadines continuously since 1650, and deforestation, poor farming practices, and rapidly increasing erosion have caused agriculture to deteriorate over the past 200 years (Kingsbury, 1960). The islands were divided into estates, with the smaller islands representing single plantations. The human population on the Grenadines waxed and waned with the sugar economy and the associated slave population. In 1831, the total human population was 9,500, of which 6,000 were slaves, and sugar production was about 25,000 tons. A more-or-less gradual population decline occurred through the remainder of the 19th century, and, by 1859, sugar production was down to 8,000 tons. By 1910, the human population was re- ported to be 2,500 persons. The 20th century, however, saw a gradual increase in human population on the islands (Howard, 1952), but sugar was grown only for local consumption. With the abolition of slavery and the sugar crisis, cotton became the important crop in the economy of the Grenadines in the latter half of the 19th The herpetofauna of Grenada and the Grenada Grenadines 199

Figure 1. Map of Grenada indicating most of the localities mentioned in the text. Contour lines are at 120 m, 365 m, and 610 m. century, and that continues to some degree today. Both sugar and cotton rely on having open, treeless (or nearly treeless) ﬁelds, and the impact of this requirement on forest-dependent species is obvious. However, as on Grenada and St. Vincent, cutting of forests on the Grenadines probably increased potential edge habitat used by species such as Corallus grenadensis (or C. cookii on St. Vincent). Howard (1952) presented detailed descriptions of the vegetation for each of the main Grenadine islands and felt that “The forested areas of the Grenadines are secondary formations. At one time practically every possible acre of land has been under cultivation and those not cultivated have been extensively cut back by the 200 Robert W. Henderson, Craig S. Berg

Table 1. Land use on Grenada in the year 2000 Vegetation category Area (ha)1 (%) Foodcrops and vegetables 441 1.4 Foodcrops, vegetables, and fruit trees 790 2.5 Mixed cultivation 10305 33.1 Sugarcane 224 0.7 Abandoned cultivation 337 1.1 Bananas 22 0.1 Bananas with cacao and/or nutmeg 1095 3.5 Cacao 575 1.8 Coconut 498 1.6 Nutmeg 3382 10.9 Nutmeg and cacao 245 0.8 Moist deciduous and semi-deciduous rainforest 4007 12.9 Mixed primary and secondary evergreen rainforest 5247 16.9 Scrub/cactus 1718 5.5 Mangrove 172 0.6 Inland swamp 17 0.1 Pastures 182 0.6 Urban/suburban 1650 5.3 Industrial 44 0.1

1 Based on data provided December 2005 by the Land Use Division, Ministry of Agriculture. pressure of [human] population needs.” More than 50 years later, his reference to the pressures of human population needs is just as applicable. Carriacou is the largest of the Grenadines with an area of 32.0 km2, its highest elevation is 291 m. Annual rainfall is about 1310 mm (Howard, 1952). Carriacou had a long history of sugar cultivation, followed by cotton. Lime trees were also extensively planted. In the remaining woodland areas, the dominant tree species are Bursera simaruba, Pisonia fragrans, Ficus lentiginosa,andLonchocarpus benthamianus. Beard (1949) encountered woodland of almost pure mahogany (Swietenia mahogani), about 18 m high; he considered it to be a pioneer community on old agricultural land. According to Kingsbury (1960), Carriacou is the longest continually occupied of the Grenadine Islands and, in 1784, it had about 50 estates varying in size from 6.5Ð223 ha. In the late 1950s, 64% of the island’s area was divided into 2,270 “peasant holdings” — cultivable land amounting to 1700 ha. Lime production was on the increase, and 162 ha were designated as forest reserves (Kingsbury, 1960). More recently, tourists have discovered Carriacou and accommodations for them are proliferating. Petit Martinique has an area of 0.7 km2 and the highest elevation is c. 243 m. We have not been to this island. However, according to Howard (1952), most of Petit Martinique’s area is devoted to crops and pasture for grazing animals, and what few woodlands remain are badly decimated. The dominant and largest tree species is Gumbo Limbo (Bursera simaruba), with lower numbers of Hippomane mancinella, Tabebuia pallida,andFicus laevigata. The herpetofauna of Grenada and the Grenada Grenadines 201

Many small (1-28 ha) islands and islets are situated off the coast of Grenada, and additional smaller islands (1-170 ha) comprise part of the Grenada Grenadines. Many of these smaller islands have been surveyed herpetologically and found to support small subsets (e.g., Eleutherodactylus johnstonei, Anolis spp., Gymnoph- thalmus underwoodi, Ameiva ameiva) of the Grenadian herpetofauna (Lazell, 1972; Corke, 1992; Williamson et al., 2002). Nevertheless, one of the St. Vincent Grenadines was recently found to harbor an endemic species of Gonatodes currently not known to occur anywhere else (Powell and Henderson, 2005b). Unquestionably, additional species will be added to the herpetofaunal lists of many of the Grenadine Islands.

History The impact of humans on the distribution, abundance, and ecology of reptiles (especially on islands) has been well documented in recent years (e.g., Case and Bolger, 1991; Case et al., 1992; Henderson, 1992; Rodda et al., 1997). According to Wilson (2001), a human migration from South America into the Lesser Antilles began about 2000 B.C. Habitat alteration undoubtedly occurred with their arrival in the region. A human population density estimate for the Lesser Antilles at the time of discovery is 500 per 100 km2 (Newson, 1976), but, by the late 1700s, “most aboriginal peoples had been extirpated through warfare, disease, enslavement, and interbreeding...” (Pregill et al., 1994). Whether involved in subsistence hunting or farming, indigenous peoples had the potential of encountering species of amphibians and reptiles on a daily basis, as did the early colonizers from Great Britain and France. Today, several members of Grenada’s herpetofauna have ecologies that are often closely associated with humans: they live in human-disturbed habitats (even entering human dwellings in search of food and shelter), eat prey species introduced into their ranges by humans, and try to avoid predators introduced into their ranges by humans (Henderson and Powell, 2001). The history of agricultural exploitation on Grenada goes back at least 2000 YBP (years before present; Bullen, 1964, 1965). The ﬁrst attempt to establish a settlement on Grenada by the British in 1609 was a failure. The ﬁrst successful attempt was by the French in 1650 (Brizan, 1984). The plantation system ushered in the era of mass clearing of forests for sugarcane, and most cultivable areas were cleared of forests. “In the interior [of Grenada], practically all of the land right to the mountain tops was originally sold to estates, and cultivations were pushed to the highest practicable limit in most cases” (Beard, 1949). From 1700-1750, sugar, indigo, cotton, cacao, and coffee were cultivated, with the latter crop the most important. In 1700, only three sugar plantations existed on Grenada, but, by 1763, they numbered 81, in addition to 208 coffee plantations (Brizan, 1984). In 1772, 334 estates were established on Grenada, and 125 of them devoted 12,955 ha to sugarcane (Brizan, 1984). Grenada’s economy, however, did not rely on a monoculture, and, in the last half of the 18th century, it was the leading producer of coffee, cotton, sugar, and 202 Robert W. Henderson, Craig S. Berg cacao in the Windward Islands. Therefore, although considerable land was cleared of trees for sugarcane, other land was planted in trees, albeit for other crops. By 1852, only 2,581 ha were planted in sugarcane and, in 2000, 200+ years after sugar had reached its economic apex, only 224 ha were devoted to sugar (M. Mason, in litt.). In the meantime, cacao, bananas, and nutmeg became economically important with 5319 ha devoted to one of the three crops, or some combination of the three, in 2000 (M. Mason, in litt.).

The Herpetofauna and Associated Conservation Concerns Nineteen species of frogs and reptiles comprise the terrestrial herpetofauna on Grenada and its Grenadines, and four species of sea turtles have been known to either nest on the island or to forage in the waters surrounding the island (table 2; Germano et al., 2003). Of the 19 terrestrial species, two are deﬁnite introductions (Eleutherodactylus johnstonei and Anolis sagrei), and another (Geochelone carbonaria) is a possible introduction. Four species are CITES-listed (all Appendix II), and only one (E. euphronides) has been Red-listed by the IUCN. Two species are island endemics (E. euphronides and Typhlops tasymicris), three are bank endemics (Anolis aeneus, A. richardii,andCorallus grenadensis), and two are restricted to the Grenada and St. Vincent banks (Leptodactylus validus, Mastigodryas bruesi). The terrestrial herpetofauna is South American in origin (Hedges, 1996; Hender- son, 2004; Lescure, 1987), with all genera and several of the species represented on the Neotropical mainland. All of the marine turtles have very broad geographic ranges and are CITES-listed (table 2). Although virtually the entire herpetofauna of Grenada has, to one degree or another, been impacted by human activity, some species have been more adversely affected than others. Herein we single out only those species for which we feel especial concern for their future on Grenada (with the exception of Geochelone carbonaria which is likely already extirpated). We make critical appraisals of their current status, discuss conservation concerns, and offer suggestions for their management. Perhaps not surprisingly, the species discussed below are a combination of taxa with which we have great familiarity, and others whose paths we have yet to cross or rarely cross.

Eleutherodactylus euphronides With a remaining range of only 16 km2 (Hedges, 1999), this frog’s status is among the most vulnerable in the West Indies. Restricted to montane forest situations at elevations >300 m, E. euphronides is threatened by habitat alteration and, possibly, by the invasive congener E. johnstonei. At Grand Etang (St. Andrew Parish, c. 525 m), both species have been encountered in the forest calling within close proximity to each other. In February 2004, E. euphronides was encountered at the rate of 6.75/man-hour (mh), while E. johnstonei was encountered at 40.8/mh. The herpetofauna of Grenada and the Grenada Grenadines 203

Table 2. The herpetofauna of Grenada. Species names followed by (I) are introduced or presumed to be so. Species Grenada West Indian Conservation distribution1 distribution status Frogs Bufo marinus G Widespread Eleutherodactylus euphronides G Grenada endemic EN Eleutherodactylus johnstonei (I) G Widespread Leptodactylus validus G Grenada Bank, St. Vincent Land turtles Geochelone carbonaria (I) G, C Widespread CITES II Sea turtles Caretta caretta G, C Widespread CITES I, EN Chelonia mydas G, C Widespread CITES I, EN Eretmochelys imbricata G, C, PM Widespread CITES I, CR Dermochelys coriacea G, C Widespread CITES I, CR Lizards Hemidactylus mabouia G, C, PM Widespread Thecadactylus rapicauda G Widespread Anolis aeneus G, C, PM Grenada Bank endemic Anolis sagrei (I) G Widespread Anolis richardii G, C Grenada Bank endemic Iguana iguana G, C Widespread CITES II Mabuya sp. G, C Uncertain Bachia heteropa G Grenada Bank Gymnophthalmus underwoodi G Guadeloupe, Dominica, St. Vincent, Grenada Bank, Barbados Ameiva ameiva G Grenada Bank, St. Vincent Snakes Corallus grenadensis G, C, PM Grenada Bank endemic CITES II Clelia clelia G Grenada CITES II Mastigodryas bruesi G, C Grenada Bank, St. Vincent Typhlops tasymicris G Grenada endemic

1 G = Grenada, C = Carriacou, PM = Petit Martinique.

We are monitoring the impact of Hurricane Ivan on both species at Grand Etang, as much of the shade-providing canopy has been greatly reduced (ﬁg. 2 in Henderson and Berg, 2005). We have found E. euphronides less common on Mt. William (above Providence, St. Andrew Parish; c. 410 m): 3.0/mh and 2.2/mh in February and November 2004, respectively; and at 5.7/mh and 3.4/mh in February 2005 and February 2006, respectively (E. johnstonei was encountered at 42.7/mh, 26.2/mh, 38.6/mh, and 57.0/mh during the same months). In the forest at the Cable and Wireless Station above Blaize (St. Andrew Parish; c. 690 m; ﬁg. 2), E. johnstonei (3.3/mh and 0.7/mh in February 2005 and February 2006, respectively) was absent from the forest interior and E. euphronides was very common (30.7/mh and 204 Robert W. Henderson, Craig S. Berg

Figure 2. Eleutherodactlylus study site at the Cable & Wireless Station above Blaize at 690 m (February 2005). (Colour original Ð see www.ahailey.fg.co.uk/appliedherpetology/cariherp.htm).

17.3/mh). Eleutherodactylus euphronides, probably more than any other member of the Grenadian terrestrial herpetofauna, needs to be carefully monitored.

Geochelone carbonaria It is possible that this species was introduced to Grenada either by indigenous peoples or by colonial Europeans. We have not encountered it during our many The herpetofauna of Grenada and the Grenada Grenadines 205 visits to the island, and it is now considered extirpated (Ministry of Finance, 2000), likely eliminated by subsistence hunting. The species is not uncommon on some of the Grenadines.

Marine turtles Four species of marine turtles nest and/or forage in the area of Grenada and its Grenadines (table 2). On Grenada, leatherbacks (Dermochelys coriacea)are the most frequent nesters (Levera and Bathway are the highest density beaches, with occasional nesting at Grand Anse and Pink Gin beaches; fig. 1), followed by hawksbills (Eretmochelys imbricata). Loggerheads (Caretta caretta) and green turtles (Chelonia mydas) nest only rarely on Grenada (Bräutigam and Eckert, 2006; Carr et al., 1982). Nesting by hawksbills has been documented on Caille and Ronde islands (between Grenada and Carriacou; Bräutigam and Eckert, 2006), whereas leatherbacks and hawksbills are the predominant species around Carriacou (Fastigi, 2002). The history of marine turtle exploitation on and around Grenada is extensive, and recent surveys of local fishermen indicate that fewer turtles are now caught compared to years past, and that total numbers of turtles in Grenada are lower than in the past (Shirley, 2002). Although 2004’s Hurricane Ivan has disrupted non- governmental organization (NGO) population monitoring and other conservation efforts, the impact on nesting and foraging has not yet been assessed (Bräutigam and Eckert, 2006). Based on their field research in Grenada, Eckert and Eckert (1990) estimated that 25-50% of nesting leatherbacks were killed each year and that at least 50% of the eggs laid were collected by humans. Since February 2001, however, the leatherback is completely protected. Intensive beach monitoring by an NGO at Levera began in 1999. In 2000, fewer than 100 nests were recorded, more than 500 in 2003, and between 300 and 400 in 2005 (Bräutigam and Eckert, 2006). Nevertheless, as elsewhere in the range of marine turtles, poaching and habitat destruction remain constant threats.

Iguana iguana Although this species has one of the widest geographic distributions of any reptile in the American tropics, populations have been severely impacted by over-hunting. Iguanas are one of the primary game animals on Grenada, along with opossum (Didelphis marsupialis), armadillo (Dasypus novemcinctus), mona monkey (Cer- copithecus mona), and pigeon (Columba squamosa): Ministry of Finance (2000). Informal surveys by the Forestry Department indicate that numbers of I. iguana are dropping, although no reason was provided. Our encounters with iguanas have been few and far between. We occasionally observe sleeping individuals during searches for treeboas (at Levera, Pearls, Beausejour, and Westerhall), and we have seen them captured for food at Pearls. Because this species is exploited as a source of food for 206 Robert W. Henderson, Craig S. Berg human consumption, surveys designed to monitor numbers captured and the status of local populations should be conducted.

Mabuya sp. Because the taxonomy of Lesser Antillean Mabuya is in a state of ﬂux, we have opted to not assign Grenadian populations to species. We have had but a single encounter with this lizard on Grenada, and that occurred in 1989 on the Point Salines Peninsula. Over a period of 25 days in 1961, Albert Schwartz and associates collected full-time on Grenada and did not encounter Mabuya; they did, however, collect and observe it in the mongoose-free Grenadines (Albert Schwartz, ﬁeld notes). Although this species will ascend into bushes (M. de Silva, in litt.; pers. obs. on other Lesser Antillean islands), it is largely ground-dwelling and diurnal and, therefore, like species of Ameiva throughout much of the West Indies (Powell and Henderson, 2005a), is vulnerable to mongoose (Herpestes javanicus) predation. It is unlikely that the species has been extirpated from Grenada. However, we believe that the mongoose is likely responsible for its rarity, and that eventual extirpation by this introduced predator is certainly a possibility.

Ameiva ameiva Several populations of Lesser Antillean Ameiva have been eliminated from islands in the Lesser Antilles, and Powell and Henderson (2005a) attributed these extirpations to the mongoose (although domestic and feral cats and dogs also prey on them). Ameiva ameiva has a very wide distribution on the Neotropical mainland, and it occurs on several continental and oceanic islands. On Grenada, its distribution now appears to be highly fragmented and restricted to open areas with considerable human activity and minimal mongoose activity (e.g., the grounds of hotels). A study conducted on the grounds of the Rex Grenadian Hotel on the Point Salines Peninsula in June 2002 indicated an adult population size of 23.0±0.2, and a density estimate of 460 adults/ha (Simmons et al., 2005). About two months after Hurricane Ivan hit Grenada (November 2004), Henderson and Berg (2005) found Ameiva of all age and size classes to be very common on the grounds of the Rex Grenadian. At the time, the hotel was closed for repairs and human activity was considerably less than when the hotel was open for guests. This species likely will persist in small, scattered enclaves on Grenada in open situations where mongoose activity is either absent or minimal.

Corallus grenadensis The distribution, ecology, and potential conservation concerns regarding this snake species have been described and discussed at length in Henderson (2002). Dur- ing the past 500 years, original habitat was altered or destroyed, native rodents The herpetofauna of Grenada and the Grenada Grenadines 207

(rice rats, probably Oryzomys; Lippold, 1991; Pregill et al., 1994) that were probable prey species became extinct, and alien predators were introduced. Treeboas on the Grenada Bank have had to adapt to new habitat (orchard trees), introduced prey species (Rattus rattus and Mus musculus), and new predators (Her- pestes javanicus, Didelphis opossums, humans). Considering the impact of humans on treeboa ecology in Grenada and despite the creation of more edge habitat, that Corallus grenadensis is widespread and locally common is remarkable. We believe that this can be attributed to a number of factors: 1) Arboreal, cryp- tically colored, compactly coiled on a branch, and sheltered by leafy vegetation, these snakes are inconspicuous during daylight hours. Being arboreal, they are able to avoid non-human predators (e.g., dogs, largely ground-dwelling mongooses). 2) Although they may actively forage at night, without the aid of a light to detect reflection from a boa’s eyes, they remain inconspicuous to humans in their leafy arboreal surroundings. 3) They prey on common vertebrates (some commensal) that occur in high densities, so wide-ranging foraging is not mandatory for locat- ing prey. We have documented decreases in encounter rates of C. grenadensis over the past four years at Pearls, in mangrove (Rhizophora)andAcacia habitats bordering Mt. Hartman Bay (St. George Parish), and at Beausejour and Westerhall in areas of native vegetation and mixed agriculture (Henderson, 2002). Although housing devel- opments at Beausejour and Westerhall may be partially responsible for population declines at those sites, we are at a loss to explain the depressed numbers at Pearls and Mt. Hartman. Mongooses are not uncommon at Mt. Hartman, and they have been observed foraging in trees. Whether they are a significant predator on arboreal boas is unknown, but surely they do occasionally eat them. Opossums (Didelphis marsupialis) are common everywhere on Grenada, are scansorial, and will prey on C. grenadensis (Henderson, 2002). The Pearls site deserves additional attention. It is a site we have visited off and on since 1988. Between 1988 and 2000, treeboa encounter rates ranging from 2.9±0.3 to 8.4 ± 1.8/mh were recorded (Henderson, 2002). In 2002, work was intensified at the site and we began marking snakes with microchips. Between February 2002 and February 2005, the capture rate dropped from 1.5/mh to 0.7/mh, and the encounter rate dropped from 3.3/mh to 0.7/mh (i.e., often more snakes are encountered than we are able to capture). In June 2004, a two-night survey of the study site produced no snakes. Thus, encountering treeboas is now difficult where, five years earlier, two observers could encounter more than 20 C. grenadensis in an hour. In 2005, no large (>950 mm SVL) treeboas were encountered, only young-of-the-year and a single yearling. Likewise, the proportion of treeboas captured in the 700-950 mm SVL size class decreased markedly: in 2002, they represented 32.6% of our sample (n = 46), 20.4% in 2003 (n = 54), and 10.7% in 2004 (n = 28). Pearls was no more developed in 2005 than it was in 1988. If anything, the study site was less developed, human activity was diminished, and wide, previously cleared trails became overgrown through lack of use. As these snakes are conspicuous edge 208 Robert W. Henderson, Craig S. Berg inhabitants, the loss of edge habitat along our transect trails may have contributed to decreased treeboa activity. This explanation, however, is inadequate to explain the dramatic decline in snake numbers, as is the damage wrought by Hurricane Ivan in September 2004 (since we had witnessed declines prior to the hurricane). Similarly, at Mt. Hartman Bay, encounter rate dropped from 2.4 ± 0.1/mh in 1994 to 0.2 ± 0.2/mh in 1998 (Henderson, 2002). Again, no evidence of habitat destruction was noted at this site, nor could we document an increase in human activity. Snakes were scale-clipped at this site and, although snakes that are captured once may move out of an area, we are not convinced that this is a plausible explanation for depressed numbers at either Mt. Hartman or Pearls. As adaptable as C. grenadensis appears to be in terms of habitat, habitat loss is undoubtedly the greatest threat it faces. As areas become devoid of trees, or as patches of trees become smaller and smaller, portions of Grenada and the Grenadines will no longer be able to sustain treeboa populations. As a consequence of continued development, C. grenadensis will face at least local extirpations (Henderson, 2002).

Clelia clelia Possibly three species of Clelia inhabited the Lesser Antilles at one time: Clelia sp. on Guadeloupe, C. errabunda on St. Lucia, and C. clelia on Grenada. The Guadeloupean and St. Lucian species are extinct; only C. clelia survives and, to the best of our knowledge, it has not been collected or observed by a herpetologist on Grenada since 1964 (Greer, 1965). This large (>2.0 m SVL), diurnal, ground- dwelling trophic generalist has a wide geographic distribution on the Neotropical mainland. As noted previously (Henderson, 2004), it seems out of place in the Lesser Antilles where colubrids rarely exceed 1.0 m SVL. Despite its size, it may have been as vulnerable to predation by Herpestes as the smaller Alsophis and Liophis on other islands in the Lesser Antilles — or, as suggested by Henderson (2004), Clelia populations in the West Indies may have, for a variety of reasons, been on a downward trajectory for many hundreds of years. Only three specimens of Clelia are known from Grenada, and only two of those have reliable locality data. Both were collected on the leeward side of the island, one at Beausejour (St. George Parish) and the other in the Duquesne Valley (St. Mark Parish). Both were collected in the morning, and James Lazell (in Greer, 1965) believed the species to be “fairly common” in the wet lowlands. Although we have never encountered this snake despite many months of ﬁeld work, which has included hundreds of hours driving the roads at all hours of the day and night (including the road where one Clelia was collected), we are not prepared to consider it extirpated. While taking a Coke¨ break at a small store south of Grenville near the windward coast in November 2004, we entered a conversation with a group of men relaxing outside the store. We explained what we were doing (looking for snakes after the hurricane) and they mentioned cribos (the local name for Clelia). As with virtually everyone we have ever queried about this species, most The herpetofauna of Grenada and the Grenada Grenadines 209 were familiar with it but had not seen it since they had been children. One man, however, said he had seen one just recently; based on his excellent description, it could not have been anything but Clelia.

Mastigodryas bruesi Although fairly widespread on Grenada (Schwartz and Henderson, 1991), we have had only two encounters (the St. Paul’s area in St. David Parish and dead on the road below Birch Grove in St. Andrew Parish) with this species; a third was observed by one of our students at Westerhall (St. David Parish), a fourth in December 2005 (A. Sánchez, in litt.) and a fifth in February 2006 (N. Fleming, pers. comm.), both in the environs of St. George’s. Another was observed on Carriacou. During 25 days of intensive collecting on Grenada in 1961, Schwartz and associates collected three M. bruesi (Albert Schwartz, field notes). This is a diurnal frog and lizard predator that is encountered at ground level and in trees and bushes. Certainly mongooses prey on it, and this may account for its seeming rarity on Grenada. We suspect this species is still fairly widespread on the island, but at low population densities. All indications are that it is still fairly common on several of the Grenadines (RWH, pers. obs.; Albert Schwartz, field notes; M. de Silva, in litt.).

Typhlops tasymicris This small secretive snake was ﬁrst collected near Vincennes (St. David Parish) in 1968 and described in 1974, and only one additional specimen (also collected in 1968 at Pearls, St. Andrew Parish) has been added to scientiﬁc collections since then (Wallach, 2000). We have worked extensively near the site where the second specimen was collected, and have described the snake to people involved in agriculture at this site; so far, no one has expressed any familiarity with the species. Whether this species is genuinely rare or if its secretive habits have precluded frequent encounters is unknown. It is not familiar to Grenadians we have queried at several sites on the island.

Discussion Members of Grenada’s terrestrial herpetofauna have demonstrated ecological plas- ticity in habitat, climatic regimes, and diet. Persistence in human-disturbed habitats is testimony to the adaptability of most reptilian species on the island. Nevertheless, two factors are having a negative impact on frog and reptilian populations: 1) habitat loss or alteration, and 2) introduced species. Neither factor is unique to Grenada, and both are widespread concerns throughout the West Indies and elsewhere in the world. The greatest threats to Grenada’s marine turtles are illegal slaughter, poaching of nest contents, and habitat destruction for development associated with the tourist industry (e.g., hotels, golf courses). Again, none of these threats is unique to Grenada. 210 Robert W. Henderson, Craig S. Berg

Although Grenada’s human population growth between the years 2000 and 2010 is estimated to be static (MacDonald, 1992), and land area devoted to forested habitats actually increased between 1981 and 1990 (World Resources Institute, 1994), habitat loss or modification still affects every native species of frog and reptile on Grenada. Over 60% of the island’s area is devoted to agriculture or is developed residentially or for industry (table 1), and the island is a mosaic of habitat fragments. Flying over the island on a clear February morning in 2005, we were able to observe the patchwork of human enclaves interspersed with small stands of forest. Houses lined the roads from one end of the island to the other and, seeing this, we were amazed at recalling the numbers of Corallus encountered from time to time in habitats that were intermixed with residential areas (e.g., Beausejour, Pearls). Now, however, we have documented unsettling population declines in C. grenadensis. To identify these declines as the direct result of habitat loss/alteration or part of a natural cycle of waxing and waning numbers is premature. What is a certainty, however, is that some areas that once supported treeboa populations no longer do so, or that treeboa numbers in other areas have been dramatically reduced. The impact of alien species on West Indian herpetofaunas has been ongoing since the arrival of Europeans. Although the introduced rodents Mus musculus and Rattus rattus are now an important source of food for treeboas (and, possibly, C. clelia) on Grenada (and elsewhere), identifying a positive facet of other introductions is difficult. The frog Eleutherodactylus johnstonei has become en- trenched on many West Indian islands outside of its native range, and it now occurs on the Neotropical mainland as well. Eleutherodactylus johnstonei may even- tually be found everywhere on Grenada and it is likely that nothing can be done to halt its invasion of new habitats. It is uncertain at this time if it is actually dis- placing the Grenadian endemic E. euphronides. They co-occur at Grand Etang (a National Park and a favorite recreational destination for Grenadians and tourists) where E. johnstonei has invaded the forest, and our encounter rates at this site favor E. johnstonei.However,aspre-johnstonei rates are lacking from the forest interior, we do not know if E. euphronides numbers have been reduced. If they have not, and, if habitat alteration is halted at forested elevations over 300 m, E. euphronides should survive. We are unsure of the long-term impact of 2004’s Hur- ricane Ivan. In the short-term, E. euphronides seems to be doing well (Henderson and Berg, 2005) and, over the past several thousand years, E. euphronides has undoubtedly withstood many hurricanes, certainly many as powerful and destructive as Ivan. The introduction of Herpestes javanicus into the West Indies is correlated with the disappearance of several species of ground-dwelling lizards, snakes, and birds (Powell and Henderson, 2005a). As with E. johnstonei, eradication of this species on Grenada is unlikely. Ameiva, Mabuya, and, possibly, Clelia, are the reptiles most vulnerable to this efficient predator. The Grenadian herpetofauna has shared the island with Herpestes for over 120 years (Hoagland et al., 1989), and, with the The herpetofauna of Grenada and the Grenada Grenadines 211 probable exceptions of ground-dwelling snakes, Ameiva ameiva,andMabuya sp., most members have survived its depredations. All steps must be taken to prevent the accidental introduction of mongooses onto the Grenadines. The Division of Forestry in the Ministry of Agriculture on Grenada is sincere in its efforts to protect wildlife, including amphibians and reptiles. Over many years and many visits to their offices, we have witnessed increasing concerns for the herpetofauna and a growing emphasis on educating the public regarding the island’s natural history. More than half of Grenada’s native herpetofauna has a CITES and/or IUCN listing (table 2), and every effort is made to abide by the CITES designations by the Division of Forestry and the Ministry of Agriculture. Based on personal experience, we are aware of the many layers of paperwork that must accompany any export of herpetofauna, including assurances to Forestry by U.S. Fish and Wildlife personnel that the desired animals are not CITES listed. Grenada is promoting tourism and it is experiencing a growing interest in eco- tourism. The Grand Etang Reserve is a favored stop for bus tours on Grenada, and it is often the only site visited by tourists traveling by cruise ship who have only a short time to sightsee on their island-hopping itinerary. Lizards are often the most conspicuous vertebrates on West Indian islands, and may be the only wildlife tourists observe on the manicured grounds of luxury hotels on or near Grand Anse Beach and the Pointe Salines Peninsula. In short, active protection of the island’s native herpetofauna by way of responsible stewardship of its natural resources can only enhance the nature experience for Grenadians and eco-tourists alike.

Acknowledgements. Over the years, the Windway Foundation, the Milwaukee Public Museum, the National Science Foundation (Grant No. DBI-9732257 to R. Powell), the late Albert Schwartz, the late Jack A. Puelicher, Milwaukee County Zoo, the Milwaukee Zoological Society, the J. C. Penney Golden Rule Foundation, and the Robert Bourgeois family have generously funded our fieldwork. Alan Joseph and other Forestry Division personnel on Grenada have been supportive of our fieldwork for many years, and for that we are most appreciative. The Division of Herpetology at the University of Kansas graciously provided copies of the field notes of the late Albert Schwartz. Michael Mason of the Ministry of Agriculture provided data on land use on Grenada. Recent treeboa fieldwork has been facilitated by the enthusiastic participation of Ky Henderson, Rich Sajdak, and Aaron Savit. John Parmerlee provided the map in fig. 1, Karen Eckert provided helpful information regarding the status of sea turtles in Grenada, and James Lazell, Bob Powell, and Peter Tolson reviewed earlier versions of this paper and offered constructive criticisms. We remain grateful to Nigel Fleming, owner of Lazy Lagoon Cottages, for charging us the “herpetologists’ rate” for our living quarters. 212 Robert W. Henderson, Craig S. Berg

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Accepted: March 20, 2006 (BSW).