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Occurrence of microhabitat conditions under rocks which harbored Sphaerodactylu s parvus versus occurrence of microhabitat conditions under all rocks examined (D, dirt; G, gravel; L, leaves; R, rocks). Asterisks indicate that ratios varied signi cantly (2 £ 2 contingency tests, df D 1).
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Sphaerodactylus parvus is a dwarf gecko endemic to the Anguilla Bank in the Lesser Antilles, West Indies. Aspects of S. parvus ecology were studied at six sites on Anguilla. Geckos were encountered most frequently in association with rock spills, and gecko population densities (0-5.2/m2) were correlated positively with rock densities. A disproporti...
Citations
... Almost all geckos encountered at night were completely exposed and not hidden by leaf litter, rocks, or other debris. If exposed during the day, we would expect that someone would have detected the species considering the amount of diurnal surveys in the past, that diurnal dwarf gecko activity is relatively easy to detect (Bentz et al. 2011, Hensley et al. 2004, Leclair and Leclair 2011, López-Ortiz 1999, Nava et al. 2001, Rodda et al. 2001, Steinberg et al. 2007, Thomas and Kessler 1996, Turk et al. 2010, and the substantial effort the team spent walking the entire island during the day in 2014 and 2016. ...
... While avoiding diurnal exposure, the Monito Gecko takes advantage of lower temperatures and increased humidity within the hostile environment of Monito Island, and also avoids potential predation by anoles. Monito Island may also lack the diurnal microhabitats that provide the necessary temperature and humidity gradients preferred by other diurnal Sphaerodactylus (Nava 2004, Nava et al. 2001, Steinberg et al. 2007. ...
... On Mona Island, S. monensis also occur in the presence of cats. In fact, Sphaerodactylus in Puerto Rico and the Caribbean are known as some of the most numerous lizards in the region despite also occurring with rats and other invasive mammals such as cats and mongoose (Bentz et al. 2011, Hensley et al. 2004, Leclair and Leclair 2011, López-Ortiz 1999, Nava et al. 2001, Rodda et al. 2001, Steinberg et al. 2007, Thomas and Kessler 1996, Turk et al. 2010. ...
Sphaerodactylus micropithecus (Monito Gecko) is an endemic species restricted to Monito Island, an island ~75 km west of mainland Puerto Rico that consist of ~14.7 ha of protected habitat. This species was listed as endangered in October 1982 under the Endangered Species Act (ESA) based on the best available science, which indicated that the species had 1 small population where suspected predation by Rattus rattus (Black Rat) was limiting population growth. Between 1982 and 1994, diurnal visual surveys resulted in a direct maximum count of 21 individuals. Furthermore, 3 capture–mark–recapture surveys conducted in 1993, 1994, and 1997 indicated population densities of 4100, 6000, and 3500 geckos, respectively, based on Petersen-method estimation. A rat eradication campaign was conducted in 1992–1993 and 1998–1999. After the last rat eradication event and gecko survey in 1997, neither formal rat searches nor gecko population estimates were conducted until 2014. When we re-surveyed Monito Island in 2014, no rats were found, and 23 geckos were directly counted in the first nocturnal survey on the island. The discovery of nocturnal activity led to the development of the first nocturnal systematic survey for the gecko in 2016 within 40 randomly distributed plots across the island. Survey and estimation results indicated an occupancy of 27.8% (50% CI: 11.3–68.6%) and a population estimate of 7661 geckos (50% CI: 5344–10,590). Based on these results and alleviation of rat predation, the Monito Gecko was removed from the ESA list in October 2019. Here, we describe the history of conservation efforts for the Monito Gecko, highlight the collaborative efforts between governmental and non-governmental entities for the recovery of the species, and describe the foundation for systematic surveys for this gecko that may work for other threatened species throughout the region.
... Although ENM are simplifications of the relationships between species and the environment, they allow us to determine how exposed they are to this phenomenon and assess their degree of vulnerability to the predicted conditions [43]. The development of more precise models seems to be the best strategy to improve the quality of the predictions and provide an appropriate response [37], mainly when the available biological knowledge about the species is scarce [45], as in the case of most of the Cuban members of suborder Sauria. ...
Climate change has modified the distribution and abundance of numerous species. Being ectotherms, reptiles are especially susceptible to this phenomenon, which worldwide threatens almost 40 % of known species of lizards. Its impact on the herpetofauna of Cuba has been little studied. Therefore, we estimate the possible effects of climate change on the distribution of 46 endemic lizard species. To modelling the climatic niche of the species with the MaxEnt program, we used 3 698 presence records and 17 WorldClim bioclimatic variables. For transferring to the future, we used two climate scenarios with RCP 2.6 and RCP 8.5, at two times periods (2050 and 2070). We assumed vulnerability as the potential reduction of future areas of climatic suitability (ACS) compared to current ones. We superimposed the distributions to detect sites of greater potential richness and those of greater exposure to climate change. We evaluated the models obtained as useful and excellent according to the AUC values, reflecting their high predictive capacity. The most extensive current ACS corresponded to Anolis equestris (98 213 km 2), and the smallest to A. quadriocellifer (3 074 km 2). With the most alarming scenario (RCP 8.5), a loss of more than 30 % of the ACS and a greater probability of extinction in their current areas of occupation was predicted in almost 85 % of the species by 2070. Mesophilic species showed greater vulnerability, losing 30.8 to 100 % of their future ACS for the RCP 8.5 scenario. The trend in all projections was the reduction of ACS, mainly in the West and Center regions. The greater richness of lizards, and the greater gain and stability of future ACS, corresponded to the main mountainous massifs of the country, so that these regions could act as climatic refuges against the conditions of climate change. However, the little dispersal capacity of these species and low landscape connectivity resulting from anthropic activities could limit the future colonization of available habitats.
... The peak of gecko activity during the first three hours following sunset at Naqbain may be explained by lizards' searching for food after a rather long time resting in retreat. Similar conclusions were also reported for the Egyptian geckos which have a unimodal activity pattern, with highest activity instantly after dusk and a rather steady decline until first daylight (Ibrahim, 2004(Ibrahim, , 2007(Ibrahim, , 2008(Ibrahim, & 2013Ibrahim and Ghobashy, 2004) as well as for other nocturnal geckos (Pianka and Pianka, 1976;Huey, 1979;Huey et al., 1977;Cooper et al. 1985;Nava et al., 2001). The decline of lizard activity at night, especially in winter, is probably attributable to the decrease in body temperature of these lizards (Parker and Pianka 1974). ...
Ecology of the fan-toed Gecko, Ptyodactylus hasselquistii, was studied in Naqbain village, Ha'il province, Saudi Arabia from January to December 2014. The maximal number of active geckos was recorded in spring and summer, with peaks of activity during the first three hours following sunset. Geckos showed irregular unimodal patterns of activity throughout different seasons; and exhibited diurnal activity most of the day time inside concrete buildings. More than a half number of geckos were active in direct artificial night lighting, 26.5% in partial light, 12% in full darkness, 6% in daylight. The present geckos were usually encountered on fences and walls of buildings and they were occasionally seen on rocks and on the ground. Individuals frequently assumed positions at heights ranging from 15– 350 cm above the ground. Lizards fed upon a wide range of food comprising insects, spiders, and plant materials. Coleopterans were the most important item in terms of number, volume, frequency of occurrence and the index of relative importance. P. hasselquistii displaced a sit – and – wait feeding strategy. Diversity of food items was greatest in spring and summer with the maximum number of prey per stomach recorded in spring. There was a seasonal variation of food items taken by P. hasselquistii. Adult geckos showed no significant difference in prey size selection. The reproductive season extends from April through August; and hatchling may occur in September and October. The youngest female having two oviductal eggs measured 61 mm SVL. The relative clutch mass of females (RCM) varied from 0.015-0.096. The relative ova size (ROS) averaged from 0.13– 0.27. Testicular volume increased from March with peaks in April and May then decreased from July to November. The relative testes size (RTS) ranged from 0.022-0.09 and the relative testes mass (RTM) reached its maximum in May and varying from 0.0015-0.005. The youngest male having enlarged testes measured 61 mm, and was captured in May.
... Sphaerodactylus levinsi prefers rock cover in forested areas and tends to avoid grassy or shrubby habitat (Meier and Noble, 1990). Sphaerodactylus parvus also appears to choose rocks over other cover types, but the complexity of the substrate under and around the rock plays a major role in rock choice (Nava et al., 2001). Rock cover may be an important aspect of sphaerodactyl microhabitat selection because it provides shelter from predators as well as protection against overheating and desiccation (Nava et al., 2001). ...
... Sphaerodactylus parvus also appears to choose rocks over other cover types, but the complexity of the substrate under and around the rock plays a major role in rock choice (Nava et al., 2001). Rock cover may be an important aspect of sphaerodactyl microhabitat selection because it provides shelter from predators as well as protection against overheating and desiccation (Nava et al., 2001). Because of their small size, sphaerodactyls are highly susceptible to desiccation (Leclair, 1978;Snyder, 1979;Steinberg et al., 2007;Turk et al., 2010;Johnson et al., 2013). ...
... In nature, sphaerodactyls occur in extremely high population densities (to 57,000/ha in S. parvus [Nava et al., 2001] and 67,600/ha for S. macrolepis [Rodda et al., 2001]). Other studies (e.g., Leclair and Leclair, 2011) found that, despite these high population densities, more than one individual is rarely found under the same cover item. ...
Abstract Both environmental factors and social factors affect an animal's choice of microhabitat. We explored the effects of humidity and the presence of conspecifics and predators on microhabitat selection by Brown-Speckled Sphaeros (Sphaerodactylus notatus; Squamata: Sphaerodactylidae). To test the effect of environmental moisture, we provided geckos a choice between shelters of varying humidity and determined that individuals were significantly more likely to choose more humid shelters. In interaction trials between conspecifics of different sizes and sexes and between geckos and predators, we found that lizards were unwilling to share shelters with conspecifics in all situations. We observed aggressive behaviors such as chasing, biting, and head bobbing and noted that subordinate geckos were unwilling to enter a shelter occupied by a dominant individual even in the presence of a predator.
... Reptiles in more xeric environments are generally more resistant to desiccation than even closely related forms from more mesic habitats (e.g., Warburg, 1966;Perry, Dmi'el and Lazell, 2000;Steinberg et al., 2007). These adaptations can be anatomical, such as decreasing epidermal permeability to fluids (Cohen, 1975) or behavioural, such as seeking microhabitats that retain moisture (Maclean, 1985;Steinberg et al., 2007) or limiting activity during warmer times of day (Nava et al., 2001) or year (Dawson, Shoemaker and Licht, 1966). ...
In June 2012 on Eleuthera, Commonwealth of the Bahamas, we examined water-loss rates of Hemidactylus mabouia and Sphaerodactylus notatus to test the prediction that the larger, nocturnally active H. mabouia will experience comparatively lower mass-specific water-loss rates and percentage mass lost than the diminutive, diurnally active S. notatus. During the first hour, S. notatus experienced a faster rate of water loss than H. mabouia, and juvenile H. mabouia lost proportionately more water than adults. After the first hour, water-loss rates did not differ significantly between the two species or between adult and juvenile H. mabouia. In terms of percentage loss of original mass, S. notatus was indistinguishable from adult and juvenile H. mabouia. Desiccation rates were near the lower limits reported for congeners of both species, which might be attributable to the relatively xeric conditions on Eleuthera. In general, these data supported our prediction that H. mabouia will experience lower mass-specific water loss rates than S. notatus.
... Similar findings were also reported for the Suez Canal and Sinai geckos, which have a unimodal activity pattern, with the highest activity immediately after sunset and then a steady decline until first daylight (Ibrahim, 2004(Ibrahim, , 2007(Ibrahim, , 2008Ibrahim and Ghobashy, 2004). This activity pattern applies to other nocturnal geckos as well (Pianka and Pianka, 1976;Huey et al., 1977;Huey, 1979;Cooper et al., 1985;Nava et al., 2001). The decline of lizard activity at night, especially in winter and spring, is probably attributable to a decrease in air temperature and, hence, body temperature of these lizards (Parker and Pianka, 1974). ...
Field observations and lab studies were carried out on the Rough-tailed Gecko (Cyrtopodion scabrum) in the Suez Canal Zone to assess sexual size dimorphism, activity, habitat selection, growth rate, diet, and reproduction. Cyrtopodion scabrum showed no significant sexual difference in body size and head shape characters. The lizard's maximum activity was in autumn and the minimum in winter, with peaks of daily activity during the first 3 h following sunset; air temperature was a major factor controlling daily and seasonal activity of C. scabrum. Lizards were solitary and had small home ranges. They occupied all available substrates and assumed different positions at heights ranging from 5 to 500 cm above the ground. The greatest rate of growth occurred in spring, and growth ceased altogether during winter. Lizards with the smallest snout vent length had the highest growth rate. A total of 14 arthropod orders were recorded in the diet of C. scabrum; dipterans and hymenopterans dominated in number and volume, respectively. Cyrtopodion scabrum showed evidence of a sit-and-wait foraging mode. Males and females both ate prey of similar numbers and sizes; however, lizard stomachs were filled with food in spring more than any other season, which may indicate the lizard's increased need for energy for reproduction. The reproductive season extended from March through September. Peak reproductive activity for both sexes was in June and July. Female C. scabrum deposited single-egg clutches more commonly than two-egg clutches and displayed communal nesting, which was previously unrecorded for the species.
... Dwarf geckos normally and naturally occur at very high densities. For example, S. parvus reaches 52,000 per hectare on Anguilla (Nava et al. 2001), and S. macrolepis numbers up to 67,000/ha on Guana Island, British Virgin Islands (Rodda et al. 2001). On Grand Terre, S. fantasticus has been recorded at densities of 10,000 per hectare (Breuil, 2002, cited by Henderson & Powell, 2009). ...
Rodents have been successfully eradicated from hundreds of islands ranging in size from 1 to 11,200 hectares throughout the world, including more than 20 islands in the Caribbean. These cases demonstrate how safely and effectively rats can be eliminated, and the remarkable benefits their removal can bring to both wildlife and people. Some of the best examples are in Antigua and Barbuda, where a dozen islands have been cleared of alien invasive black rats Rattus rattus since 1995.
In recent years, a number of organisations and individuals, including technical staff of the Environmental Awareness Group and Government of Antigua and Barbuda, have put forward the idea of eradicating rats from Redonda to support the recovery and conservation of the island’s biodiversity. At approximately 53 ha, planar area (or circa 80 ha, surface area), Redonda is one of the largest islands in Antigua and Barbuda and has been identified in the national land use plan as a priority site for environmental conservation.
This report presents the findings of a study to determine the methods and cost of eradicating rats from Redonda, and examines the possible benefits this could bring to wildlife and people. The study entailed a trip to Redonda from 10-14 April and 18 April 2012, a literature review, and a series of consultations with key government and non-governmental stakeholders on Antigua. While the main focus of our study was on the rats, this report also contains new information on the status and ecology of native wildlife and the feral goats on Redonda, which will also assist with conservation planning.
Redonda has been formally recognised as an Important Bird Area and supports rare and unique animals and plants of both national and global importance. At least three endemic lizards still remain: Redonda ground lizards Ameiva atrata, Redonda tree lizards Anolis nubilis and an unnamed dwarf gecko Sphaerodactylus sp.; all of which qualify as globally threatened according to the findings from this survey. Birds include regionally, even globally, significant colonies of brown boobies (774 pairs), masked boobies (164 pairs), red-footed boobies (over 150 pairs) and magnificent frigatebirds (119 pairs), plus smaller numbers of red-billed tropicbirds, brown noddies and bridled terns. However, the seabird colonies appear smaller and less diverse than they ought to be, and there is a dearth of terrestrial birds - only two peregrines and a few zenaida doves were observed in April 2012. Seventy species of plants and a few invertebrates have been recorded, but some species are also feared to be extinct and more extensive surveys are warranted. No amphibians or native mammals have been recorded.
The Eurasian black rats on Redonda are unusually large and their density is exceptionally high. Use of trapping lines indicated that Redonda has at least 70 rats per hectare, or a total population of approximately 5,500 rats. Only black rats are known to be present: brown rats R. norvegicus and house mice Mus musculus were not detected during this or previous studies and it appears that previous reports of brown rats were in error. The omnivorous black rats are having a very severe impact on the wild animals and plants of Redonda. Rats were observed killing seabird chicks larger than themselves, while autopsies of trapped rats found the rats eating a wide range of food items including various plants, seabird eggs and chicks, lizards and goat droppings. Many native birds, reptiles, plants and invertebrates have already disappeared, and many remaining species are now critically scarce. Species not seen for many years include the last Antiguan burrowing owls Athene cunicularia amaura and the endemic Redonda skink Copeoglossum redondae. Their decline is almost certainly linked to predation by rats.
The island’s high density of rats, remote location and very rugged terrain presents a number of challenges. As described in this report, the research team carried out a full site assessment, measured rat density and distribution, identified and evaluated risks, difficulties and mitigation measures, conducted bait trials to test whether the rats would accept rodenticide, identified non-target species, and evaluated different methods and materials. This assessment concludes that the eradication of black rats from Redonda is technically feasible, and this report outlines the set out the operational options and technical requirements for the proposed eradication.
The aim of the proposed operation should be to eradicate all rats from Redonda while minimising any adverse impacts on the environment, non-target species and people. It is recommended that the eradication takes place outside the hurricane season, ideally January to April, in a combined aerial and ground-based operation using rodenticide containing the anticoagulant brodifacoum. The proposed eradication techniques have proven to be safe and effective and are supported by similar operations in the Caribbean and around the world. Up to 13 persons will be required to complete this work effectively: five helicopter team members (including pilot and ground crew) and eight ground-based operators. Additional persons will be required to monitor wildlife, logistical support, communications and outreach on Antigua & Barbuda and Montserrat.
This rat eradication operation would involve a number of stages. Necessary tasks include: (i) produce a detailed Operational Plan; (ii) obtain required permits and approvals; (iii) continue stakeholder consultation; (iv) prepare tenders and contracts; (v) establish monitoring and research programmes; (vi) appoint eradication personnel; (vii) purchase all equipment and bait; (viii) implement the rat eradication (i.e. baiting and evaluation); (ix) develop and implement a post-eradication biosecurity strategy to prevent rats and other species from (re)invading Redonda; and (x) design and implement long-term monitoring of flora and fauna species and the ecosystem to measure the effects of the rat eradication. It may also be necessary to (xi) move some of the endemic lizards to a temporary ex-situ facility on Antigua during the eradication operation to remove any risk of direct or secondary poisoning. Monitoring to detect any surviving or invading rats should also be continued, with a final evaluation of the success of the eradication carried out after two years.
Taking into account the relatively large size of Redonda and its remote location, rugged terrain, high transport costs and lack of infrastructure, the rat eradication operation would cost approximately US$250,000. We recommend allocating up to US$630,000 over four years to include necessary pre- and post-eradication monitoring, biosecurity, contingency costs and a temporary ex-situ facility for lizards, should this prove necessary. After the eradication, the long-term maintenance costs will be low and could realistically be sustained from small grants or nature-based revenue generated by the island. A detailed inventory of equipment and manpower is provided in this report.
There would be significant benefits to eradicating rats from Redonda, as detailed in this report. Populations of some of the island’s rare and endemic species would increase significantly, including the reptiles, seabirds, certain plants and invertebrates. Furthermore, in the near future, the rat-free Redonda could potentially be recolonised by animals and plants that historically occurred there, such as the iconic burrowing owl. Eradicating rats from Redonda would therefore be a major achievement and a very clear demonstration of Antigua and Barbuda’s commitment to the Convention on Biological Diversity.
However, it is conceded that the island’s ecological recovery will be limited as long as feral goats remain on the island. This report strongly recommends the goat herd also be removed in the interests of animal welfare, to conserve native biodiversity, to reverse the ongoing process of deforestation and desertification, and to strengthen the island’s natural resilience to climate change. Fewer than 50 goats inhabit Redonda at the time of writing, the majority of them adult males, and mass die-offs from starvation have been observed during droughts.
In our consultations we found strong interest among stakeholders, including technical agencies in the Government of Antigua and Barbuda, the Environmental Awareness Group, in this proposed eradication of rats. It is imperative that all of the relevant government agencies maintain an integral role in the planning, preparation and implementation of this project, working alongside civil society to ensure its success. Redonda is uninhabited and rarely visited, but excites great curiosity and excitement. Ongoing consultation and communication about the proposed eradication to Antiguans, Barbudans and the neighbouring Montserratian communities will also be essential to ensure lasting success.
In summary:
1. Black rats Rattus rattus have a very severe impact on the native biodiversity of Redonda, and additional species are predicated to disappear if rats remain. The rats were confirmed to feed on a wide variety of items including plants, eggs, chicks, lizards, goat droppings and invertebrates.
2. Using index trapping, the mean rat density on Redonda was estimated to be at least 70 rats per hectare, giving a total population of approximately 5,500 rats. This is a very high density.
3. The eradication of black rats from Redonda is technically feasible, using a combined aerial (helicopter) and ground-based operation. The entire operation, including post-eradication monitoring and establishment of biosecurity measures, is estimated to cost approximately US$630,000.
4. To achieve success, the rat eradication would require experienced operators and the combined support of the Government of Antigua and Barbuda, the Environmental Awareness Group and international partners. All stakeholders consulted in 2012 appeared very interested and supportive of the proposal to eradicate rats from Redonda.
5. The recommended rat poison for the proposed eradication operation should be brodifacoum, an anticoagulant rodenticide. Approximately 2 tonnes of bait will be needed.
6. The proposed rat eradication should be undertaken during the dry season, from January to April, but preparatory work – including further stakeholder consultations and fundraising – are needed at least one year in advance.
7. As described in this report, the design and implementation of the proposed eradication programme must include measures to minimise risks to non-target species, especially the Redondan endemics, and contingency plans to deal with any incidents.
8. Rats, birds, reptiles, invertebrates, vegetation and goats should be monitored before and after the eradication programme to assess the project’s success and impacts. Data in this report can serve as a baseline for evaluating future changes.
9. Adequate biosecurity protocols need to be established and maintained to reduce the risk of rats re-invading Redonda in the future. Surveillance by boat owners and operators will be vital to ensure rodents are not accidentally brought to the island on their boats.
10. Based on field data gathered during this study it is strongly recommended that the feral goats are also removed for both conservation and animal welfare reasons. The herd is under extreme stress and their presence is driving deforestation, desertification and the loss of native biodiversity.
Before eradicating rats, we also recommend developing a site management strategy to determine whether and how Redonda will be used for biodiversity conservation, cultural heritage preservation, tourism, education, research, and/or other functions in the future. This will clarify the context of the rat eradication and help to ensure that post-eradication biosecurity measures are fully compatible with other management activities.
... However, our estimates for S. kirbyi are very low when compared to those of most other West Indian Sphaerodactylus. For example, Turk et al. (2010) recorded a high of 7,650 S. fantasticus fuga/ha on Dominica (mean 1,210.0 ± 823.0/ha for 10 transects in coastal forest), Steinberg et al. (2007) recorded mean densities of 2,562.5 ± 632.5 S. vincenti/ha (maximum 5,625/ha) on St. Vincent at sites where at least one lizard was found, Breuil (2002) recorded 10,000 S. fantasticus kerukera/ha on Grand Terre (Guadeloupe) and 7,900 S. phyzacinus/ha on Grand Îlet (Îles des Saintes), Nava et al. (2001) recorded ecological densities (under rocks) to 52,000 S. parvus/ha on Anguilla, and Thomas and Kessler (1996) recorded a density of 10,000 S. klauberi/ha on Puerto Rico. Our estimates also were substantially lower than the maxima recorded for other West Indian congeners in Henderson and Powell (2009), which ranged as high as 67,600/ha for S. macrolepis in continuous Seagrape (Coccoloba uvifera) habitats on Guana Island in the British Virgin Islands (Rodda et al. 2001). ...
The slopes above Chatham Bay on Union Island, St. Vincent and the Grenadines, support one of the last mature secondary forests in the Grenadines. The characteristics of the forest allow it to support a unique herpetofauna that includes four small crevice- and litter-dwelling reptilian species (Gonatodes daudini, Bachia heteropa, Sphaerodactylus kirbyi, and Typhlops tasymicris). We examined population sizes and densities, activity periods, microhabitat use, thermal biology, and water loss rates of these four presumably syntopic species to better understand these poorly known species and the unique ecological system of the forest floor on which they depend. Our findings show that G. daudini, S. kirbyi, and B. heteropa are present in the similar to 37-ha area of forest above Chatham Bay at a ratio of approximately 2: 1: 12, respectively, and tentatively estimated total population sizes are about 6,600 G. daudini, 3,200 S. kirbyi, and 39,000 B. heteropa. Each of the four species was found to exploit separate microhabitats based on specific needs for cover, moisture, and thermal environments. The conditions necessary for these species to thrive apparently are available only in relatively mature forest situated to receive and hold moisture. This unique assemblage and the forest that supports it are under severe and imminent threat from exotic mammals and development, and the preservation of the area above Chatham Bay should be a high conservation priority of regional governmental agencies and non-governmental organizations.
... Thus, these findings point toward a historical or genetic constraint on visual performance given that diurnal Sphaerodactylus geckos have evolved from nocturnal ancestors. Because of their diminutive size and extraordinarily high rates of evaporative water loss, Sphaerodactylus are vulnerable to heat stress and desiccation, and as a result are generally restricted to humid, leaf litter microhabitats under the shade of trees (Nava et al. 2001; Hensley et al. 2004; Steinberg et al. 2007). Microhabitat preferences for ectotherms, especially tiny ones, are greatly influenced by physiological functions, such as heat regulation and water balance (Huey 1991; Wolf & Walsberg 1996; Chown & Nicholson 2004). ...
Recent studies of the sensory drive hypothesis suggest that communicative signals evolve readily whereas change in sensory perception is more constrained by the demands of the physical environment.
Here, we find that diurnal Sphaerodactylus macrolepis geckos collected from dark, forested habitats were best able to detect motion in very dim light (< 10 lux), whereas geckos collected in brightly‐lit coastal areas exhibited optimal motion detection at a much brighter light range 200–300 lux.
Motion detection by geckos from both habitat types declined as light intensity increased above 300 lux. These differences were observed after the lizards had been living in a common laboratory environment for 1 full year and are hence unlikely to be due to acclimation effects.
Light conditions for optimal visual performance match the light conditions of the natural habitats in which the lizards are found. Our results support the suggestion that visual performance may evolve quickly and that the sensory drive process may be best described as repeated co‐evolution between signals and receiver sensory systems.
Thus, for animals that inhabit wide ranges of visual habitats, the sensory drive process may potentially act differently on separate visual response properties, resulting in diverse levels of variation and divergence in visual performance and communication systems.
... Across all surveyed sites on Saint Lucia (n=55) and Montserrat (n=43), the density of pygmy geckos was three times higher on Montserrat. This appears to indicate a real difference in densities, not one that can be explained by differences in behaviour On other islands, species for which densities have been published include Sphaerodactylus sputator (801 per hectare on Saint Eustatius: Hensley et al. 2004); S. sabanus (188/ha: Hensley et al. 2004), S. parvus (up to 52,000/ha on Anguilla: Nava et al. 2001) and S. macrolepis (up to 67,000/ha on Guana Island, British Virgin Islands: Rodda et al. 2001). Based on my experience of working on many of these islands, I consider the density of Sphaerodactylus microlepis on Saint Lucia to be unnaturally low, with the possible exception of relatively small patches of high quality deciduous forest on Grande Anse and Maria Major where these pygmy geckos were easy to find. ...
This study of Saint Lucia’s forest herpetofauna was carried out as part of the National Forest Demarcation and Bio-Physical Resource Inventory Project. It entailed a literature review, interviews, and nationwide field surveys.
Nineteen native species of reptiles and amphibians (three extinct), and nine alien species (three extinct) have been recorded in Saint Lucia to date, all of which are illustrated and described in this report Endemicity is remarkably high among the native forest community, with seven nationally endemic species, and five endemic subspecies. All but one of the extant species were seen during the present survey.
To assess and compare the diversity and relative abundance of reptiles and amphibians in different forest types, 55 sites were intensively surveyed for an hour apiece using visual search techniques. The forest class with by far the greatest diversity and abundance of species was mature Deciduous Seasonal Forest (seven species confirmed, and a mean encounter rate of 36.8 individuals per hour), followed by mature Freshwater Swamp Forest and Semi-Evergreen Seasonal Forest. Forests that naturally had significantly lower species diversity and abundance were Elfin Shrubland (only one species confirmed), Lower Montane Rainforest, Fumarole Vegetation and Mangrove. Human degradation of all forest classes was significantly associated with an increased number of alien invasive species. These findings were corroborated with additional, opportunistic surveys, interviews with local experts, and the literature.
These findings tell us that the existing forest reserve system on Saint Lucia is woefully inadequate in representing and protecting the nation’s herpetofauna. Ironically, the forest classes that are best represented in the protected area system have the lowest diversity and abundance. The species-rich Deciduous Seasonal Forests and Freshwater Swamp Forests are largely outside of the protected zone and thus at risk. An important exception to this rule are the xeric Maria Islands (12ha), which supports seven native species, many of which are scarce or absent from the ‘mainland’. This survey also found encouraging signs that the rare and important Semi-Evergreen Seasonal Forest - a mesic forest type that was largely cleared for agriculture in the past – is regenerating where farms have been abandoned for economic or other reasons.
After assessing and comparing the conservation significance of major forest classes, the conservation status of every native forest species was examined. Drawing on historical records and comparisons with other West Indian islands, this study found most of Saint Lucia’s native forest species have declined significantly in distribution range and population size; some to critically low levels. By applying the IUCN categories of threat, at least six endemics now qualify as globally threatened with extinction, i.e. Critically Endangered: Saint Lucia racer; Endangered: Saint Lucia whiptail; or Vulnerable: Saint Lucia pygmy gecko (both subspecies), Saint Lucia thread snake, and, perhaps surprisingly, Saint Lucia fer-de-lance. If it is taxonomically distinct, the Saint Lucia iguana also qualifies as Critically Endangered. When these findings are pooled with additional considerations of economic use, cultural values and ecological importance, the reptiles that emerge as the nation’s highest conservation priorities are the iguana, racer and whiptail lizard.
The greatest threats to Saint Lucia’s native forest herpetofauna - and the root cause of most of their declines - are alien invasive animals. These include predatory mammals, e.g. the opossum, rats, dogs, cats and feral pigs and, most importantly, the mongoose. Alien invasive reptiles and amphibians also pose a great danger to native species through predation, competition and hybridization. The introduced green iguanas near Soufriere present a clear hazard to the native iguana through competition and hybridization. This field survey also discovered that the alien Watts’ anole has become widely dispersed and appears to be displacing the endemic Saint Lucia anole in disturbed habitats. There is an extremely high risk of more alien species invading the near future, assisted by human transport. There are a number of other threats to the forest herpetofauna which are also important and are discussed in this report, including habitat loss, hunting and agrochemical pollution. Loss of genetic diversity, stochastic effects and climate change are serious impending threats to the species and subspecies that are scarce or confined to offshore islands.
In addition to identifying gaps in the protected area system, this study highlighted some disturbing weaknesses in the Wildlife Protection Act 1980 (revised 2001). While this important piece of legislation has been very successful in combating over-exploitation, it was not designed to - and thus largely fails to - address other, greater threats to Saint Lucia’s herpetofauna. Furthermore, the legal status of only five of the 12 extant native forest species, and none of the six extant alien species, is explicitly defined in the Act, leaving many species in a legal grey area.
Taking into account the legislative limitations and other known constraints to the management of Saint Lucia’s herpetofauna (public attitudes, human and financial resources, information, technological limitations), a series of practical management recommendations are proposed. The objective of these is to conserve Saint Lucia’s unique and important forest herpetofauna, including enabling the most threatened species to recover:
Management Recommendations (See Chapter 6 for more details)
Objective: Control the introduction and spread of alien invasive species that endanger forest herpetofauna
• Keep the offshore islands free of alien invasive species [TOP PRIORITY]
• Eradicate the introduced green iguanas to conserve the Saint Lucia iguana [TOP PRIORITY]
• Control harmful alien invasive mammals from priority sites on the main island
• Minimise the probability of non-native species invading Saint Lucia [TOP PRIORITY]
• Minimise the probability of species from Saint Lucia invading other countries
Objective: Revise the national legislation to reflect the current needs of Saint Lucia’s herpetofauna
• Revise the next edition of the Wildlife Protection Act [TOP PRIORITY]
Objective: Secure the protection and regeneration of important dry and mesic forest sites on Saint Lucia
• Establish at least one new nature reserve to protect dry forest wildlife communities on the main island of Saint Lucia [TOP PRIORITY]
• Formulate local agreements to preserve important wildlife habitats and forest corridors
Objective: Update and use the Red List system to guide and support improved management
• Enable IUCN to list all native Saint Lucia reptiles with appropriate categories of threat on the international Red List [TOP PRIORITY]
• Develop a National Red List
• Prepare and implement species conservation action plans for Saint Lucia’s most threatened herpetofauna
Objective: Conduct applied research to inform and monitor the management of Saint Lucia’s herpetofauna
• Assess the status and ecological needs of, and threats to, the least-known species [TOP PRIORITY]
• Elucidate the impacts of different alien invasive animals on native reptiles and amphibians
• Monitor selected populations and forest habitats to evaluate and guide management decisions
• Conduct applied research on improved medical treatment for snakebites
Objective: Strengthen local and national understanding and support for conservation
• Increase public interest in and awareness of Saint Lucia’s reptiles and amphibians
• Heighten public understanding of the impact of alien invasive species
