Conservation of the Lesser Antillean , Iguana delicatissima, on

by Glenn P. Gerber representing

Fauna & Flora International

and the

Anguilla National Trust

January 1998 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

TABLE OF CONTENTS

SECTION CONTENTS PAGE

1. INTRODUCTION 1 1.1 Background 1 1.2 Objectives 2 2. ANGUILLA 2 2.1 Physical Geography 2 2.2 Climate 2 2.3 Fauna 3 2.4 Flora 3 2.5 Human History 4 3. LESSER ANTILLEAN 4 3.1 Previous and Ongoing Research 4 3.2 Morphology 5 3.2.1 Body Size and Sexual Dimorphism 5 Table 1. Morphology of adult I. delicatissima on Anguilla 6 3.2.2 Coloration and Sexual Dichromatism 6 3.3 Distribution 7 3.3.1 Anguilla Proper 7 3.3.2 Offshore Cays 7 3.4 Abundance 7 3.5 Suitability of Offshore Cays 8 3.6 Natural History 9 3.6.1 Sex Ratio 9 3.6.2 Age Structure 9 3.6.3 Behavior 9 3.6.4 Habitat 9 3.6.5 Thermoregulation 9

ii Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

TABLE OF CONTENTS (continued)

SECTION CONTENTS PAGE

Table 4. Body temperatures of I. delicatissima on Anguilla 10 3.6.6 Feeding Habits 10 3.6.7 Nesting Sites 10 3.6.8 External Parasites 10 3.7 Blood Samples and Genetic Studies 11 3.8 Probable and Potential Causes of Decline 11 3.8.1 Hunting and Collecting 11 3.8.2 Introduced Predators 11 3.8.3 Introduced Competitors 12 3.8.4 Habitat Loss and Degradation 12 3.8.5 Common Iguanas 13 4. RECOMMENDATIONS 14 4.1 Iguana Studies 14 4.2 Habitat Protection 14 4.3 Control of Introduced Mammals 14 4.4 Control of Common Iguanas 15 4.5 Headstarting and Captive Breeding 15 4.6 Satellite Populations 16 5. ACKNOWLEDGEMENTS 16 6. REFERENCES 17 7. APPENDIX 17 Figure 1. Map of 18 Figure 2. Map of Anguilla 19 Table 2. Iguanas captured on Anguilla during the survey 20 Table 3. Characteristics of islands within Anguillan territory 21 Table 5. Plants in the diet of I. delicatissima on Anguilla 22

iii Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

1. INTRODUCTION

1.1 Background

The family is comprised of eight genera and about 30 species of large herbivorous found in the Americas, the Fiji Islands, the Galapagos Islands, and the islands of the West Indies. Many of these lizards, particularly those restricted to islands, are presently considered to be in danger of extinction (IUCN, 1996).

Two genera of the Iguanidae, and Iguana, occur in the West Indies. The genus Cyclura is restricted to the Bahamas and Greater Antilles, and is comprised of eight species, all of which are endangered. The genus Iguana is native to the Lesser Antilles and parts of Central and South America, and is comprised of two species, one of which is endangered. As a group, West Indian iguanas are the most endangered lizards in the world (Alberts, in press).

The two species comprising the genus Iguana are the Lesser Antillean iguana (I. delicatissima) and the common iguana (I. iguana). Lesser Antillean iguanas are endemic to the islands of the northern Lesser Antilles and are endangered, whereas common iguanas are native to the islands of the southern Lesser Antilles as well as much of Central and South America and are not endangered. Common iguanas have also been introduced to several areas, including some of the islands in the northern Lesser Antilles.

Historically, Lesser Antillean iguanas were probably common on every island from Anguilla to . Due to impacts associated with European colonization, however, this is no longer the case. , hunting, the introduction of exotic predators and competitors, and hybridization with common iguanas threaten Lesser Antillean iguanas with extinction across their range. Indeed, Lesser Antillean iguanas have already been extirpated from several islands, including St. Kitts, Nevis, Barbuda, and Marie-Galante.

As a species, Lesser Antillean iguanas are listed as “vulnerable” to extinction by the International Union for the Conservation of Nature (IUCN, 1996). However, individual populations on several islands, including Anguilla, are acknowledged to be critically endangered.

The population of Lesser Antillean iguanas on Anguilla is very small, only occupies a tiny fraction of its original range, and is threatened by habitat loss as well as competition and predation from a variety of introduced mammals. In addition, as a result of hurricanes Luis and Marylin in September 1995, a significant number of common iguanas were swept off of an island in the southern Lesser Antilles, most likely , and onto Anguilla where they may have established a breeding population. Elsewhere in the Lesser Antilles, the establishment of common iguanas has resulted in the rapid disappearance of Lesser Antillean iguanas due to competition and hybridization. Consequently, measures to protect Lesser Antillean iguanas on Anguilla are needed now more than ever.

The historical and present distributions of I. delicatissima and I. iguana in the Lesser Antilles are shown in Figure 1 (see Appendix).

1 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

1.2 Objectives

The primary aims of the fieldwork conducted on Anguilla between the 18th of August and the 26th of September, 1997 were:

• To assess the current distribution and abundance of Lesser Antillean iguanas and common iguanas on Anguilla and all offshore cays

• To identify the probable threats to the continued survival of Lesser Antillean iguanas and propose solutions

• To initiate studies of the natural history and population biology of Lesser Antillean iguanas on Anguilla

2. ANGUILLA

2.1 Physical Geography

Located at the north end of the Lesser Antilles at latitude 18o13’N and longitude 63o03’W, Anguilla is part of a chain of limestone islands, known as the Limestone Caribbes, extending from Sombrero to Marie Galante (see Figure 1 in Appendix). Anguilla lies on a large, shallow, ocean bank (the Anguillan Bank) and was likely connected to other islands on the bank, including St. Martin and St. Barts, during the last glacial maximum, about 10,000 years ago.

Anguilla is approximately 24 km long and 5 km wide at its broadest point, with an area of about 70 km2. A number of smaller islands are found near Anguilla on the Anguillan Bank, including Anguillita, Dog Island, the Prickly Pear Cays, Scrub Island, and Little Scrub Island (see Figure 2 in Appendix). These islands are part of Anguillan territory, as is the small island of Sombrero which occupies its own bank about 60 km northwest of Anguilla.

Anguilla is a low island with a maximum elevation of about 70 m. The long axis of the island runs approximately east to west and much of the north coast, which is generally higher in elevation than the south coast, forms bluffs and cliffs. Coves with sand beaches are common along the entire coast. There are no surface streams, and all ponds are salt or brackish water.

Weathered limestone pavement, with little soil cover and pitted by solution hollows, is the most common substrate on Anguilla. What little soil does exist on the limestone is an alkaline, reddish brown clay of low fertility known as terra rossa (or red earth). In poorly drained depressions, a blackish, highly alkaline clay called rendzina accumulates.

2.2 Climate

Anguilla’s climate is tropical but dry. Average daily temperatures range from 22 - 29 oC in January to 24 - 32 oC in July. Mean relative humidity is close to 70% throughout the year. Mean

2 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla annual rainfall is just over 1000 mm with peaks in May and August-November. Tropical storms account for much of the rainfall received.

2.3 Fauna

In addition to Lesser Antillean iguanas, the reported herpetofauna of Anguilla includes one frog (the whistling frog, Elutherodactylus johnstonei), one tortoise (the red-footed tortoise, Geochelone carbonaria), one snake (the racer, Alsophis rijersmai), and six lizards (the ground , Ameiva pleei; the tree lizard, Anolis gingivinus; the wood slaves, Hemidactylus mabouia and Thecadactylus rapicauda; the pygmy geckos, Sphaerodactylus sputator and S. macrolepis parvus; and the slippery back, Mabuya mabouya). Descriptions of these species can be found in Schwartz and Henderson (1991). All of these species are native to the Lesser Antillean region, except for the wood slave, H. mabouia, which is introduced from Africa. In addition, two species of ground lizard are endemic to specific offshore cays of Anguilla: Ameiva corax to Little Scrub Island and A. corvina to Sombrero Island. Finally, three other species have only recently been found on Anguilla. These include a blind snake (genus Typhlops), the Cuban treefrog (Hyla septentrionalis), and the common iguana (I. iguana). The treefrogs were probably inadvertently introduced, the snake may be native but previously over looked due to its small size and secretive habits, and common iguanas were transported to Anguilla during in 1995 (see Sections 1.1 & 3.8.5).

Approximately 130 species of birds have been reported from Anguilla, but a large percentage of these represent transients or migrants. About 40 species of birds are known to breed on Anguilla. In addition, many of Anguilla’s offshore cays support large rookeries of one or more species of seabird, including brown pelicans (Pelicanus erythrorhynchus), magnificant frigatebirds (Fregata magnificens), brown boobies (Sula leucogaster), masked boobies (Sula dactylatra), brown noddys (Anous stolidus), sooty terns (Sterna fuscata), and laughing gulls (Laurus atricilla).

The only mammals native to Anguilla are a few species of bats. However, humans have introduced a large number of mammals to the island, including rats, cats, dogs, goats, sheep, and cattle (see Sections 3.8.2 and 3.8.3).

2.4 Flora

Under the Beard (1955) system of classifying types of tropical American vegetation, Anguilla’s natural vegetation is predominately dry evergreen thickets and bushlands, with some woodlands. This type of vegetation is commonly referred to as thorn scrub. Although large areas have been cleared of vegetation, particularly surrounding settlements, a significant amount of the native thorn scrub is still intact on Anguilla. Unfortunately, none of the island’s vegetation has escaped the impact of free-ranging goats and sheep.

Due to the paucity of soil and rainfall, agriculture is at best tenuous on Anguilla. Historical records show that cultivation of sugar cane and cotton, and the planting of mahogany were

3 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla largely unsuccessful. Today, agriculture consists largely of small home gardens and a few larger plots.

The most recent published flora of the island (Howard and Kellogg, 1987) lists 443 species. Recent work by Mary M. Walker (unpublished) has expanded this list to over 500 species. Most of the plants are common to other islands in the Lesser Antilles, and are also found on the drier parts of Puerto Rico and Hispaniola. Only one plant species, Rondeletia anguillensis, is considered endemic to Anguilla.

2.5 Human History

Archeological evidence suggests that archaic age Amerindians were present on Anguilla by approximately 3,300 years ago, and ceramic age Amerindians were present on Anguilla by at least 1,600 years ago. Around 1000 years ago, Anguilla most likely became an Amerindian Cheifdom, and the appearance of imported stone in archeological sites of this period suggests that trade with other islands was well established by that time.

European contact with the Lesser Antilles began with the second voyage of Christopher Columbus in 1493. In the decades that followed, millions of Amerindians were killed or died from European diseases, and by 1600 almost no island Amerindians remained. The first historical documentation of Anguilla by Europeans was in 1564 by a French expedition, and in 1631 the Dutch built a fort on the island. Anguilla was not officially colonized by Europeans until 1650, however, when a group of English settlers from St. Kitts moved to the island. The island has remained with the British ever since, and today is one of five United Kingdom Dependent Territories in the Caribbean. Anguilla presently has a population of about 10,000 people, primarily of African decent, and much of the local economy centers around tourism.

2.5 Protected Areas

A National Park has been proposed for a 2 ha tract of land surrounding Fountain Cave, an Amerindian site of considerable significance, located adjacent to Shoal Bay on the northeast coast of Anguilla. Aside from this small area, however, Anguilla has no terrestrial preserves.

3. LESSER ANTILLEAN IGUANAS

3.1 Previous and Ongoing Work

Little research has been published concerning Lesser Antillean iguanas, or common iguanas that inhabit the Lesser Antilles (see species accounts in Schwartz and Henderson, 1991). Indeed, aside from faunal lists, anecdotal notes, and early taxonomic accounts, the only substantial publication concerning the iguanas of the Lesser Antilles is that of Lazell (1973), and much of his work is now outdated.

Fortunately, several studies are now underway on the iguanas of the Lesser Antilles. Mark Day (of FFI) is conducting doctoral research at the University of Aberdeen and the University

4 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

College of North Wales on the population biology of iguanas throughout the Lesser Antilles. Aspects of his research include geographic variation using molecular genetic and multivariate statistical techniques, hybridization, home range and habitat use, diet, and ectoparasites. Michel Breuil of the Museum National d’Histoire Naturelle de Paris is conducting ecological research on both Lesser Antillean and common iguanas in Guadeloupe, Martinique, St. Barts, and St. Martin. Results of these studies are not yet published, but a species account for I. delicatissima which summarizes many of the recent findings concerning this species is in press (M. Day, M. Breuil, and S. Reichling).

In addition, following Hurricane Luis in September 1995, Karim Hodge of the Anguillan National Trust, aided by Ellen Censky of the Carnegie Museum of Natural History, began capturing and marking Lesser Antillean iguanas and common iguanas on Anguilla as part of the Trust’s conservation program. A total of 11 I. delicatissima and 11 I. iguana were captured, marked, and released prior to the present survey. In addition, a tissue sample was obtained from each , and sex and snout-vent length (SVL) were recorded. Data on these were made available and are incorporated where appropriate.

Note: One of the Lesser Antillean iguanas previously marked by the Anguilla National Trust was recaptured during the present survey. Unfortunately, it was determined that the sex and snout-vent length of this animal had been previously misreported. The recaptured animal had originally been identified as an adult male with a SVL of 360 mm, but upon recapture the animal was found to be an adult female with a SVL of 305 mm. Consequently, data on the size and sex of iguanas collected prior to the survey are excluded from this report. Nevertheless, the previous captures provided valuable information regarding the distribution and abundance of Lesser Antillean iguanas and common iguanas on Anguilla, and tissue samples collected from these animals will be instrumental to genetic investigations (see Section 3.7).

3.2 Morphology

3.2.1 Body Size and Sexual Dimorphism

Table 1 compares the morphological measurements taken for adult male and female I. delicatissima captured on Anguilla during the survey. On average, males were longer, more massive, and had wider heads than females. None of these differences are statistically significant, however, mostly likely due to the small sample sizes. Nevertheless, these data are consistent with sexual size differences reported for other populations of I delicatissima (Day et al., in press). Adult males also possessed longer dorsal crest scales on the neck, back, and tail than adult females, and these differences are significant (even when the effect of body size is removed using analysis of covariance). Finally, although not quantified, adult males were observed to have greater development of the occipital scales and jowls than adult females. Combined with stereotypical body postures, such as lateral compression of the body and gular extension, males use dimorphic features to increase their apparent size during territorial interactions with other males.

5 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

Table 1. Mean (+ standard deviation) of morphological measures taken for adult male and female I delicatissima captured on Anguilla in August-September, 1997.

Character Adult Males (n=5) Adult Females (n=5) P-value*

Probe depth (mm) 39 + 7 19 + 3 < 0.01 Mass (g) 1212 + 236 1023 + 249 ns Snout-vent length (mm) 295 + 23 279 + 30 ns Tail length (mm) 737 + 27 677 + 75 ns Total length (mm) 1036 + 46 956 + 103 ns Head width (mm) 40 + 5 34 + 4 ns Neck crest scale length (mm) 21 + 3 14 + 3 < 0.01 Body crest scale length (mm) 19 + 10 10 + 3 < 0.01 Tail crest scale length (mm) 8 + 2 3 + 1 < 0.01

* t-test for sex difference: ns = not significant (P > 0.05).

3.2.2 Coloration and Sexual Dichromatism

On Anguilla, juvenile I. delicatissima are a brilliant lime-green in coloration. With age, however, the bright green coloration is gradually and completely replaced by a drab gray-brown coloration. The ontogenetic change from green to gray-brown occurs first on the extremities and last on the torso. The tail changes color first, progressively from tip to base, followed by similar changes on the limbs, the head, and finally the torso. The last areas to retain any green coloration are the ventral sides of the body. Females retain green coloration longer than males, but individuals of both sexes eventually turn completely gray-brown (see Table 2 in Appendix).

Accompanying the overall change in color from green to gray-brown are additional changes in head coloration. With age, the jowls, jaws, throat, and snout take on an off-white coloration. In addition, in 3 of 5 adult males and in all 5 adult females the jowls were distinctly pinkish in coloration. Three of the 5 adult females had a significant amount of pink coloration in the occipital region as well. The later, however, appears to be related to the presence of scar tissue. That is, animals with scar tissue on top of the head also had pink coloration on top of the head, whereas animals without scaring on top of the head did not. As male iguanas frequently bite females about the head and neck to hold them during copulation, these injuries are most likely a consequence of mating.

Finally, the dorsal crest scales and dorsal head scales were pale blue in a few adult males. This was the only apparent difference in coloration noted between adult male and female I. delicatissima on Anguilla. In contrast, populations of I. delicatissima in the southern, more mesic part of the species’ range often exhibit pronounced sexual dichromatism (Lazel, 1973; Day et al., in press). For example, adult females and subadult males retain an overall green coloration on Martinique and , and only dominant males become completely gray-brown. Further, in all other populations, pink jowls are apparently only observed in dominant males

6 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

(Day et al., in press). Consequently, there appears to be less sexual dichromatism on Anguilla than in other populations of I. delicatissima.

3.3 Distribution

3.3.1 Anguilla Proper

Much of Anguilla was systematically searched for iguanas over a six week period in August and September of 1997. Efforts were split between sites along the northeast coast where iguanas were known to occur and other relatively undisturbed areas throughout the island thought to support habitat suitable for iguanas. A minimum of several hours was spent slowly walking through the habitat at each site visited. In addition to trying to flush iguanas, we also examined these areas for indicators of iguana presence, such as feces, signs of digging, and claw marks on trees.

All of the I. delicatissima observed or captured during the survey were located within 100 m of the shoreline along the northeast coast of Anguilla between Little Bay in the west and the Brimigen Coast in the east (see Figure 2 in Appendix). With the exception of Little Bay, iguanas were previously known to occur at (or near) each of these sites. The cumulative area of all sites found to support iguanas during the survey is estimated to be no greater than 2 km2. This represents less than 3% of Anguilla’s total land area (70 km2). However, during the two years prior to the survey, individual I. delicatissima were reported to the ANT and subsequently captured from Lower and Upper Shoal Bay, The Quarter, and South Hill (see Figure 2 in Appendix). Together, these locations roughly circumscribe the area where iguanas were found during the survey. Consequently, although the I. delicatissima population is clearly centered along the northeast coast, iguanas may be spread over a much larger area at extremely low densities. Alternatively, these isolated captures may represent animals that wandered or were transported (by humans) away from the known population center.

3.3.2 Offshore Cays

During the course of the survey five offshore cays were visited and searched for iguanas: Anguillita, Dog Island, the Prickly Pear Cays (East & West), and Sombrero. No signs of iguanas were observed on any of these islands. Two other offshore cays were not visited during the survey - Scrub Island and Little Scrub Island. Of these, only Scrub Island has the potential to support iguanas (see Section 3.5), but it is not believed to do so.

It is not known whether I. delicatissima ever occupied any of Anguilla’s offshore cays, but the species does occur on small cays elsewhere in the Lesser Antilles. In addition, except for Sombrero Island, all of Anguilla’s offshore cays would have been connected to Anguilla during the last glacial advance, approximately 10,000 years ago.

3.4 Abundance

Undisturbed populations of West Indian iguanas are among the most abundant vertebrate herbivores in the world. Biomass of West Indian iguanas often exceed 20 kg per hectare, an order

7 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla of magnitude greater than that reported for any mammalian herbivore (Alberts, in Press). Because of this, it is generally easy and straight forward to estimate the actual abundance of iguana populations using distance sampling techniques.

Distance Sampling methods were originally planned to estimate the actual population density of iguanas on Anguilla. However, it quickly became apparent that iguanas were far too rare on Anguilla to employ this methodology. That is, distance sampling requires sample sizes of at least an order of magnitude larger than could be obtained on Anguilla. Consequently, we were forced to rely on estimates of relative abundance (number of animals sighted per hour of searching). In addition, we captured and marked as many iguanas as possible with the prospect of eventually being able to estimate the actual abundance using mark-recapture models.

Over a five week period, approximately 80 hours of actual field time were spent searching for iguanas at sites where they were known to occur (Little Bay, Limestone Bay, Blackgarden Bay, Brimigen Coast), and a total of 50 iguanas were sighted. Thus, on average, an iguana was sighted once every 1.6 hours of searching. This is approximately one to two orders of magnitude below what would be expected for a normal (i.e., undisturbed) population of this species.

In order to crudely approximate the actual number of animals present in the known range of I. delicatissima on Anguilla, a basic mark-recapture method was employed. Given that 11 iguanas were captured by the Trust prior to the survey and 11 animals were captured during the survey, only one of which was a recapture, the estimated population size using the Petersen mark- recapture method is 121 animals (11×11/1 = 121). However, it is critical to note that (1) this method is biased and unreliable when used with such small numbers, and (2) use of this model requires that a number of assumptions be met, most of which are violated by using the data in this manner. Based on personal experience with a large number of iguana populations on other islands, and the likelihood that there are still areas on Anguilla with iguanas that have not been identified, it is estimate that there are approximately 300 animals on the island. However, if it turns out that iguanas do not occur outside of the areas already identified, 300 animals would likely be an overestimate. In either case, the population of I. delicatissima on Anguilla is far below the environmental carrying capacity for this species and is in serious danger of extinction.

3.5 Suitability of Offshore Cays

In addition to determining the presence of iguanas on offshore cays, these islands were assessed as potential sites for the introduction of iguanas should it be decided to establish a satellite population in the future as a hedge against extinction (see Section 4.6). Table 3 (see Appendix) lists some of the characteristics of these islands that are relevant to their potential to support iguana populations. Based on these characteristics, West Prickly Pear Cay appears to be the most appropriate of the offshore cays for a future introduction of I delicatissima.

8 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

3.6 Natural History

3.6.1 Sex Ratio

The sex of each I. delicatissima captured during the survey was determined by probing for the presence/absence of hemipenes in the tail base through the cloacal opening. Of the 11 I. delicatissima captured during this survey, 5 were male and 6 were female (see Table 1 for differences in probe depths between adult males and females). Thus, based on this small sample, the sex ratio appears to be even. Unfortunately, because sex is difficult to determine by other means, animals sighted during the survey but not captured could not be included in the analysis of sex ratio.

3.6.2 Age Structure

Of the 11 I. delicatissima captured during the survey only one was a juvenile (see Table 2 in Appendix). Furthermore, all of the animals observed but not captured during the survey were of adult size. Thus, the age structure of the population appears to be heavily skewed towards adults. Juveniles may be more difficult to locate than adults simply because of their smaller size, however, and thus may have been under-represented in our survey.

3.6.3 Behavior

Most animals were encountered between the hours of 0900 and 1630, and were 2 m or more above the ground in vegetation. In general, iguanas were extremely wary and could not be approached closely; most animals descended to the ground and entered holes or crevices among the rocks while we were still some distance away. At Little Bay, iguanas were observed to occupy holes and crevices along a vertical, 25 m high coastal cliff face, and to forage in the vegetation growing above the cliff.

3.6.4 Habitat

Along the northeast coast where iguanas were observed, the vegetation rarely exceeded 5 m in height, but was dense and relatively diverse. The substrate was largely weathered limestone, characterized by an abundance of solution hollows and crevices, with little accumulated soil. This area is presently one of the least disturbed regions of the island and appears to be representative of Anguilla’s native thorn scrub.

3.6.5 Thermoregulation

Body temperatures and corresponding ambient air temperatures were taken for eight I. delicatissima at the time of capture using a cloacal thermometer. Body temperatures were consistently higher than ambient air temperatures (see Table 4), illustrating that I. delicatissima, like other iguanas, are heliothermic. Capture times ranged from 0930 to 1600 hrs, with a mean of 1220 hrs.

9 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

Table 4. Body temperatures and corresponding ambient air temperatures for I. delicatissima captured on Anguilla in August-September, 1997.

Variable n Mean + SD Minimum Maximum

Body Temperature (oC) 8 34.7 + 2.0 32.6 37.6 Air Temperature (oC) 8 30.9 + 0.8 30.3 32.5

3.6.6 Feeding Habits

Feeding habits were determined through the analysis of fecal content and by direct observation. Unfortunately, only 10 fecal samples were located during the survey, and feeding was difficult to observe due to the extreme wariness of the iguanas. Nevertheless, 16 plant species were identified in the diet of I. delicatissima on Anguilla. Table 5 (see Appendix) lists these species as well as the parts of the plant (leaves, flower, fruit) known to be eaten. Among the most preferred foods were the fruits of Bourreria succulenta, commonly known as chink bush. Six of the 11 I. delicatissima captured were in chink trees.

3.6.6 Nesting Sites

Reproduction is seasonal and, like other iguanas, female I. delicatissima deposit their eggs in underground nest chambers which they excavate. Consequently, nesting is limited to substrates which permit digging. Furthermore, because successful incubation of the eggs requires appropriate thermal and hydric conditions, only sites which receive an appreciable amount of sunlight and that do not flood are potentially suitable. On islands where most of the substrate is rock, such as Anguilla, nesting typically takes place in one of two places: (1) along the coast in deposits of sandy soil just inland of beaches, or (2) in small clearings of soil that accumulate over the limestone substrate.

In the course of the survey on Anguilla, no nest sites were definitively located. This is not particularly surprising, as nesting is seasonal and probably occurred a couple of months prior to the beginning of the survey. Nests are difficult to locate once the eggs have been deposited underground. However, evidence of nesting behavior, in the form of exploratory digs and uncompleted nest holes, was found in two locations along the dirt road which runs along the bluff between Blackgarden Bay and Limestone Bay, as well as in two locations on the hillside just east of Blackgarden Bay. Thus, it appears likely that nesting occurs in this general area.

3.6.7 External Parasites

Many , including most species of iguana, are parasitized by ticks and mites. However, no external parasites were observed on any of the iguanas captured during the survey. In addition, no ticks or mites were reported for any of the iguanas captured prior to the survey by the Anguilla National Trust (n=11) or M. Day (n=5). Thus, it appears that external parasites of iguanas are not present (or are rare) on Anguilla.

10 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

3.7 Blood Samples and Genetic Studies

A blood sample was collected from the caudal vein of each iguana captured during the survey. These samples were preserved and will be used to extract DNA for genetic analyses. Along with DNA extracted from iguana tissue samples collected previously on Anguilla and on other islands in the Lesser Antilles, this DNA will be used to determine the following:

• The amount of genetic diversity within the Anguillan population of I. delicatissima relative to that within I. delicatissima populations on other islands

• The degree of genetic similarity between the Anguillan population of I. delicatissima and I. delicatissima populations on other islands.

• The source island(s) of the common iguanas that colonized Anguilla as a consequence of Hurricane Luis in 1995.

3.8 Probable and Potential Causes of Decline

3.8.1 Hunting and Collecting

Iguanas have been hunted for food throughout human history. Iguana delicatissima and I. iguana remains have been recovered from archeological sites throughout the Lesser Antilles, suggesting that iguanas were hunted by Amerindians on all islands, including Anguilla. Furthermore, hunting iguanas for food continued with European colonization and has persisted on many islands to this day. At the present time, however, hunting does not appear to occur on Anguilla. This may be due to the fact that iguanas have been rare on Anguilla for long enough that most residents have never seen one and many are unaware of their existence. Whether or not past hunting contributed to the decline of the iguana population on Anguilla is unknown, but a recent increase in hunting on St. Eustatius has contributed to the decline of I. delicatissima on that island (Day et al., in press).

A more recent threat facing many species of West Indian iguanas is illegal collection for the pet trade. Although nearly all West Indian iguanas, including I. delicatissima, are legally protected by the Convention on the International Trade of Endangered Species (CITES), many species bring substantial prices on the black market and preventing illegal collection is difficult. Apparently, collecting does not occur on Anguilla.

3.8.2 Introduced Predators

As a group, West Indian iguanas have few natural predators. Juvenile iguanas are known to be preyed upon by native birds and snakes, but adults have few (if any) natural predators. Consequently, the introduction of mammalian predators by humans has had devastating effects on nearly all species of West Indian iguanas. For example, the introduction of domestic cats and

11 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

dogs all but eliminated a population of more than 15,000 Cyclura carinata on Pine Cay in the Turks and Caicos Islands in just three years (Iverson 1978).

Domestic cats (Felis domesticus) and dogs (Canis familiaris), and rats (Rattus rattus and R. norvegicus) were all present on Anguilla. Pet dogs and cats were frequently allowed to roam freely. Rats and cats, both of which are typically nocturnal, were occasionally encountered in the field during daylight hours, suggesting that there are significant populations of both on Anguilla. These predators likely have a significant effect on Anguilla’s iguana population. Dogs can easily kill adult iguanas and have been observed to do so on other islands, and feral cats are suspected of killing a large percentage of juvenile iguanas. Rats may eat iguana eggs, and are reported to attack juvenile iguanas on other islands.

Finally, domestic chickens (Gallus varius) have been introduced to Anguilla, and feral chickens were encountered in several areas. Whether these pose a threat to iguanas is not known, but feral chickens have been reported to consume fairly large snakes elsewhere, and so could easily kill juvenile iguanas.

3.8.3 Introduced Competitors

Because there are no large herbivorous mammals native to the West Indies, the effects of introduced livestock on native iguanas and their habitats can be devastating. For example, in the Turks and Caicos Islands, Cyclura carinata have been extirpated from almost all islands with feral livestock, but are abundant on islands without feral livestock (Gerber and Iverson, In press). This negative association between livestock and iguanas is believed to have three components. First, by eating many of the same plant species as iguanas, livestock likely compete with iguanas for food. Second, by overbrowsing and selectively eating certain plant species, livestock alter the species composition and structure of native plant communities. Finally, because of their large size, livestock physically damage sensitive habitats, such as iguana nesting sites. Extreme overbrowsing by goats in combination with a series of droughts is believed to have resulted in the extinction of several populations of I. delicatissima on the offshore islands of St. Barts (Day et al., in press).

Introduced livestock are a serious problem on Anguilla. Although cattle appeared to be tethered or penned appropriately, goats, and to a lesser extent sheep, were frequently allowed free-range and some appeared to have gone feral. Furthermore, there appeared to be no place on Anguilla that goats did not frequent; even in the most remote areas, goats were often encountered and their feces were always present. Introduced goats were also encountered on Dog Island, although they were much less abundant than on Anguilla, and are reported to be on Scrub Island as well (see Table 3 in Appendix).

3.8.4 Habitat Loss and Degradation

Although there were serious attempts at agriculture on Anguilla in colonial times, these failed due to the scarcity of soil and rainfall. Consequently, Anguilla has retained more of its natural vegetation than some of the neighboring islands where agriculture has been more successful.

12 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

Nevertheless, large tracts of land have been cleared at one time or another, and much of Anguilla’s present vegetation is comprised of secondary growth. Furthermore, free-ranging and feral livestock are degrading all terrestrial habitats, whether characterized by primary or secondary growth, and habitat is increasingly being lost to development.

The northeast coast, which contains the entirety of the known iguana population, is one of the least disturbed regions of Anguilla. It seems quite likely that iguanas persist there because of this. Unfortunately, this area is not protected and development is steadily encroaching.

3.8.5 Common Iguanas

Over the past several decades, common iguanas have almost completely replaced Lesser Antilles iguanas on several islands on the Guadeloupean Bank (Day et al, in press). Although the details by which replacement occurs are not fully understood, both hybridization and competition are believed to be involved. Consequently, if common iguanas become established on Anguilla it is feared that they could eventually replace the native population of Lesser Antillean iguanas.

As a result of hurricanes Luis and Marylin in 1995, a significant number of common iguanas “colonized” Anguilla. Most of these animals were found in beach areas, but at least one animal was found clinging to a log just offshore. In addition to Anguilla, common iguanas washed ashore on St. Martin, St. Barts, Barbuda, and Antigua after Hurricane Luis.

Common iguanas can be readily distinguished from Lesser Antillean iguanas based on the presence of an enlarged scale on each side of the head below the ear opening, known as a subtympanic plate, which Lesser Antillean iguanas do not possess. In addition, common iguanas have a series of dark bands on the tail, whereas Lesser Antillean iguanas do not. Furthermore, although hatchlings and juveniles of both species are bright green, adults of the species generally differ in coloration. As Lesser Antillean iguanas age they gradually lose their green coloration and eventually become completely gray-brown with a whitish head and pink jowls. The change from green to gray-brown begins at the tail and moves forward to cover the rest of the body (see Section 3.2.2). In contrast, common iguanas tend to retain a greenish coloration throughout their lives, especially on the tail.

Prior to the present survey, the National Trust had captured, marked, and released 11 common iguanas on Anguilla since 1995. Furthermore, two common iguanas were captured on Anguilla during the survey, one of which was a recapture of a previously marked animal (see Table 2 in Appendix), and another common iguana has been captured by the National Trust since the survey. To date, no common iguanas have been observed along the northeast coast where Lesser Antillean iguanas are known to occur (see Figure 2 in Appendix). Thus, competition and hybridization between the two species may not be a significant threat at the present time. Nevertheless, as a precaution, captured common iguanas are no longer being released back into the field.

Finally, although Hurricane Luis appears to be responsible for most of the common iguanas captured on Anguilla, several common iguanas illegally imported as pets from Florida and

13 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

St.Thomas in the U.S. Virgin Islands are known to have been released. In fact, both of the common iguanas captured during the survey were likely released pets.

4. RECOMMENDATIONS

4.1 Iguana Studies

It is important that the population of Lesser Antillean iguanas on Anguilla continues to be monitored and studied. We still lack important life history information for I. delicatissima on Anguilla, such as when and where female iguanas nest, and information of this nature is needed if efforts to protect the species are to succeed. In addition, our estimates of abundance would be greatly improved by conducting a long-term mark-recapture study. Such a study would also allow abundance to be tracked over time, and thus provide a barometer for detecting any sudden change in numbers.

Finally, although many areas of Anguilla were covered during the survey, there are areas which remain to be investigated. In particular, there is a need to more precisely define the extent of the species’ range along the northeast coast. There are almost certainly a number of small enclaves of iguanas that remain to be discovered, just as it was discovered during the present survey that iguanas inhabit the cliff at Little Bay.

4.2 Habitat Protection

If Lesser Antillean iguanas are to survive on Anguilla, it is critical that native terrestrial habitats receive protection. In particular, the habitat along the northeast coast from Little Bay to Shoal Bay needs protection, as this is the only area which still supports Lesser Antillean iguanas on Anguilla (see Figure 2 in Appendix). Unfortunately, protecting native habitats on Anguilla will be especially difficult, as most of the land is privately owned. Nevertheless, given that the local economy is based largely on tourism, and increasingly on ecotourism, it is in the long-term economic interest of all Anguillans to preserve (and restore) native habitats and species.

4.3 Control of Introduced Mammals

To ensure the long-term survival of iguanas as well as the habitats they depend upon, introduced mammalian populations need to be brought under control. In the case of livestock, a great deal could be accomplished if domestic animals were not allowed to range freely in native habitats. This may be difficult to legislate, however, given that most of the land is privately owned. In addition, resources need to be allocated for the removal of feral goats.

Controlling introduced mammalian predators may be more difficult. On very small islands, feral cats and rats can be controlled or even eliminated, but on larger islands such as Anguilla this is extremely difficult. Cats have been eliminated on some relatively large uninhabited islands by introducing feline panleukemia, a fatal communicable disease specific only to cats, followed by an intensive trapping effort to remove resistant animals. However, it is unlikely that the introduction of feline panleukemia would be permitted on an inhabited island such as Anguilla, even though a vaccine is available which could be administered to pet cats. Consequently, the best options for reducing the feral cat population are (1) to encourage residents to have their pets spayed or neutered and (2) to institute a trapping program to remove feral cats from those areas

14 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla where iguanas occur. Residents should also be encouraged to spay and neuter their pet dogs and to keep all of their pets confined to their yards or houses.

4.4 Control of Common Iguanas

Because common iguanas present a potential threat to the survival of Lesser Antillean iguanas, those caught during the survey were removed from the field and placed in captivity. It is recommended that all common iguanas captured in the future also be removed from the wild. Some may view this as interfering with a natural process - the hurricane-induced colonization of a new species. However, human-related impacts are so severe on Anguilla that the island can hardly be touted as a natural stage on which to observe such processes. In addition, common iguanas are believed to be a relatively recent introduction to Guadeloupe, the presumed source of common iguanas transported to Anguilla by Hurricane Luis. Thus, little more than the hurricane appears to be completely natural in this colonization.

Furthermore, at least some of the common iguanas captured on Anguilla were not washed in by Hurricane Luis, but were imported and intentionally released by humans. Measures should be taken to insure that common iguanas are not imported to Anguilla, and that those already in captivity are not released into the wild. This would probably be best accomplished through public education, although legislation banning the importation or release of common iguanas should also be enacted.

Finally, it is suggested that common iguanas removed from the wild be used as “guinea pigs” for a headstarting/captive breeding program for I. delicatissima (see Section 4.5). In order to be successful, captive rearing and breeding requires a certain amount of expertise and experience. Consequently, in addition to formal training at an established facility, it is advised that rearing and breeding proficiency be obtained with I. iguana on Anguilla before any I. delicatissima are removed from the wild and brought into captivity for breeding purposes. Because the species are very similar, much of the knowledge gained with common iguanas will likely apply to Lesser Antilles iguanas as well.

4.5 Headstarting and Captive Breeding

The scarcity of juvenile I. delicatissima on Anguilla suggests a problem with reproduction and (or) recruitment. Given the abundance of goats and the presence of rats and feral cats, it seems likely that many nests are destroyed before the eggs can hatch, and (or) that many of the juveniles that do emerge from nests are preyed upon (see Sections 3.8.2 & 3.8.3). Although the best way to correct these problems is to remove the threats, this will be costly and time consuming, and is probably not possible in the case of rats or cats. Consequently, it is recommended that a captive breeding and (or) headstarting program be established for I. delicatissima on Anguilla, so that animals can be raised in captivity until they are too large to be vulnerable to predation from rats or cats.

If nesting sites can be located, it may be possible to protect these from livestock using fencing as well as to capture a certain percentage of the juveniles after they hatch. These juveniles can then be raised in captivity until they are too large to be preyed upon by cats and subsequently released back into the wild. This process is commonly referred to as headstarting. If nest sites cannot be located, it may be necessary to establish a captive breeding population using wild-caught adults in order to obtain juveniles.

15 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

4.6 Satellite Populations

Due to the magnitude of the threats facing Lesser Antillean iguanas on Anguilla, the long-term prospects for survival are poor. Consequently, it is recommended that efforts be made to establish a population of Anguillan I. delicatissima on at least one of the offshore cays. The cay presently most suited for this is West Prickly Pear (see Table 3 in Appendix). To avoid further depleting the wild population on Anguilla, animals used to establish a satellite population could come from a captive breeding or headstarting program (see Section 4.5).

Initial releases should involve a small number of animals, preferably young adults of both sexes, and these should be monitored closely to determine their success or failure. Given the size of West Prickly Pear Cay, and the density of vegetation there, relocating released animals will probably require radiotelemetry. This approach is presently being used successfully on Jamaica to track headstarted Cyclura collei.

Assuming the initial releases are successful, they should be continued for several years to assure that (1) enough animals have been introduced to successfully found a breeding population and, (2) the new population is provided with as much genetic diversity from the ancestral population on Anguilla as possible. It may not be necessary to radiotrack later releases, but all introduced animals should be implanted with Passive Integrated Transponders (commonly called PIT tags) for future identification. In addition, the population should be monitored closely using mark- recapture techniques to determine relevant parameters, such as rates of growth and survival.

In addition to providing a hedge against extinction, a satellite population might also provide a valuable source of animals for repopulating Anguilla someday if conditions there improve.

5. ACKNOWLEDGEMENTS

This project was supported by a grant from the Foreign & Commonwealth Office of the UK Government to the Anguillan National Trust and conducted in collaboration with Fauna & Flora International. In addition, the project benefited greatly from the generous assistance of many other individuals and organizations. Ellen Censky, of the Carnegie Museum of Natural History, was instrumental in documenting the colonization of common iguanas after hurricanes Luis and Marylin in 1995 and in laying the foundation for the National Trust’s iguana conservation program. Permission to collect and export blood samples was granted by Rev. John A. Gumbs, Parliamentary Secretary of the Environment for Anguilla. Transportation to offshore cays was provided by Roland Hodge, Director of the Anguilla Department of Fisheries and Marine Resources. Oliver Hodge, of the Anguilla Public Health Department, aided in the identification of plant specimens. Housing of field-captured common iguanas was provided by Dr. Patrick Vanterpool and the Anguilla Department of Agriculture. References on Amerindian culture were furnished by John Crock of the Anguillan Archeological Society. Access to the unpublished work of Mary M. Walker on the plants of Anguilla was provided by Dr. Judy Dudley, UDNP Environmental Specialist and Ecologist. Finally, many Anguillan citizens assisted with this project by providing information on iguanas and other wildlife; without their interest and participation this project would have been far more difficult and less rewarding.

6. REFERENCES

16 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

Alberts, A.C. (ed.). In press. West Indian Iguanas: Status Survey and Conservation Action Plan, IUCN SSC Captive Breeding Specialist Group/Fauna and Flora International. Day, M., M. Breuil, and S. Reichling. In press. Lesser Antillean iguana, Iguana delicatissima. In West Indian Iguanas: Status Survey and Conservation Action Plan, A.C. Alberts (ed.). IUCN SSC Captive Breeding Specialist Group/Fauna and Flora International. Gerber, G.P., and J.B. Iverson. In press. Turks and Caicos iguana, Cyclura carinata carinata. In West Indian Iguanas: Status Survey and Conservation Action Plan, A.C. Alberts (ed.). IUCN SSC Captive Breeding Specialist Group/Fauna and Flora International. Howard, R.A., and E.A. Kellogg. 1987. Contributions to a flora of Anguilla and adjacent islets. Journal of Arnold Arboretum 68: 105-131. IUCN 1996. 1996 Red List of Threatened Animals. International Union for the Conservation of Nature, Gland, Switzerland. Iverson, J.B. 1978. The impact of feral cats and dogs on populations of the West Indian rock iguana, Cyclura carinata. Biological Conservation 14:63-73. Lazell, J.D. 1973. The lizard genus Iguana in the Lesser Antilles. Bulletin of the Museum of Comparative Zoology 145:1-28. Rouse, I. 1991. The Tainos: rise and decline of the people who greeted Columbus. Yale University Press, New Haven, Conneticut. Schwartz, A., and R.W. Henderson. 1991. Amphibians and reptiles of the West Indies: descriptions, distributions, and natural history. University of Florida Press, Gainesville. Wadge, G. 1994. The Lesser Antilles. In Caribbean Geology: An Introduction, p 167-177, S.K. Donovan and T.A. Jackson (eds). University of the West Indies Publishers’ Association, Kingston, Jamaica. Wing, E.L. 1989. Human exploitation of animal resources in the Caribbean. In Biogeography of the West Indies, p 137-152, C.A. Woods (ed). Sandhill Crane Press, Gainesville, Florida.

7. APPENDIX (next 5 pages)

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Figure 1. (see powerpoint file: AnguillaFig1.ppt)

18 Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla

Figure 2. (see powerpoint file: AnguillaFig2.ppt)

19