Cyclura Cychlura Research Articles

Complex tourism and season interactions contribute to disparate physiologies in an endangered rock iguana.

To promote survival and fitness, organisms use a suite of physiological systems to respond to both predictable and unpredictable changes in the environment. These physiological responses are also influenced by changes in life history state. The continued activation of physiological systems stemming from persistent environmental perturbations enable animals to cope with these challenges but may over time lead to significant effects on the health of wildlife. In the present study, we tested how varying environmental perturbations driven by tourism and associated supplemental feeding affects the energetics, corticosterone and immunity of six discrete populations of the northern Bahamian rock iguana (Cyclura cychlura inornata and Cyclura cychlura figginsi). We studied populations within and outside the reproductive season and quantified tourist numbers during sample collection. Specifically, we measured clutch size, body condition, plasma energy metabolites, reactive oxygen species, baseline corticosterone concentrations and immune function of male and female iguanas from each population to address whether (i) disparate physiologies are emerging across a gradient of tourism and feeding, (ii) both subspecies respond similarly and (iii) responses vary with season/reproductive condition. We found significant effects of tourism level, season and their interaction on the physiology of both C. c. inornata and C. c. figginsi, supporting the idea that tourism is leading to the divergence of phenotypes. Specifically, we found elevated plasma energy metabolites, oxidative stress and a measure of innate immunity (bactericidal ability), but reduced corticosterone concentrations with increasing tourism in both subspecies of rock iguanas. These physiological metrics differ according to the level of tourism in both subspecies and persist across seasons despite variation with natural seasonal and reproductive changes. These findings suggest that anthropogenic disturbance results in disparate physiologies in northern Bahamian rock iguanas.

Correlated Population Genetic Structure in a Three-Tiered Host-Parasite System: The Potential for Coevolution and Adaptive Divergence.

Three subspecies of Northern Bahamian Rock Iguanas, Cyclura cychlura, are currently recognized: C. c. cychlura, restricted to Andros Island, and C. c. figginsi and C. c. inornata, native to the Exuma Island chain. Populations on Andros are genetically distinct from Exuma Island populations, yet genetic divergence among populations in the Exumas is inconsistent with the 2 currently recognized subspecies from those islands. The potential consequences of this discrepancy might include the recognition of a single subspecies throughout the Exumas rather than 2. That inference also ignores evidence that populations of C. cychlura are potentially adaptively divergent. We compared patterns of population relatedness in a three-tiered host-parasite system: C. cychlura iguanas, their ticks (genus Amblyomma, preferentially parasitizing these reptiles), and Rickettsia spp. endosymbionts (within tick ectoparasites). Our results indicate that while C. c. cychlura on Andros is consistently supported as a separate clade, patterns of relatedness among populations of C. c. figginsi and C. c. inornata within the Exuma Island chain are more complex. The distribution of the hosts, different tick species, and Rickettsia spp., supports the evolutionary independence of C. c. inornata. Further, these patterns are also consistent with two independent evolutionarily significant units within C. c. figginsi. Our findings suggest coevolutionary relationships between the reptile hosts, their ectoparasites, and rickettsial organisms, suggesting local adaptation. This work also speaks to the limitations of using neutral molecular markers from a single focal taxon as the sole currency for recognizing evolutionary novelty in populations of endangered species.

Obtaining plasma to measure baseline corticosterone concentrations in reptiles: How quick is quick enough?

There is growing interest in the use of glucocorticoid (GC) hormones to understand how wild animals respond to environmental challenges. Blood is the best medium for obtaining information about recent GC levels; however, obtaining blood requires restraint and can therefore be stressful and affect GC levels. There is a delay in GCs entering blood, and it is assumed that blood obtained within 3 min of first disturbing an animal reflects a baseline level of GCs, based largely on studies of birds and mammals. Here we present data on the timing of changes in the principle reptile GC, corticosterone (CORT), in four reptile species for which blood was taken within a range of times 11 min or less after first disturbance. Changes in CORT were observed in cottonmouths (Agkistrodon piscivorus; 4 min after first disturbance), rattlesnakes (Crotalus oreganus; 2 min 30 s), and rock iguanas (Cyclura cychlura; 2 min 44 s), but fence lizards (Sceloporus undulatus) did not exhibit a change within their 10-min sampling period. In both snake species, samples taken up to 3–7 min after CORT began to increase still had lower CORT concentrations than after exposure to a standard restraint stressor. The “3-min rule” appears broadly applicable as a guide for avoiding increases in plasma CORT due to handling and sampling in reptiles, but the time period in which to obtain true baseline CORT may need to be shorter in some species (rattlesnakes, rock iguanas), and may be unnecessarily limiting for others (cottonmouths, fence lizards).

Marine subsidies likely cause gigantism of iguanas in the Bahamas.

We utilized natural experiment opportunities presented by differential conditions (presence/absence of seabirds and invasive species) on cays in the Bahamas to study whether interisland variations in food resources contributed to gigantism in Allen Cays Rock Iguanas (Cyclura cychlura inornata). We analyzed the stable carbon (δ13C) and nitrogen (δ15N) isotope values from iguana tissues and resources from each island food web to test the predictions that (1) food webs on islands with seabirds exhibit the influence of marine subsidies from seabird guano, whereas those from non-seabird islands do not, and (2) size differences in iguanas among cays were due to either (a) supplemental food availability from mice and/or seabird carcasses killed by barn owls (Tyto alba) and/or (b) access to more nutrient-rich vegetation fertilized by seabird guano. Food web components from the seabird island (Allen Cay) had 5-9‰ higher δ15N values than those on the other cays and Allen Cay plants contained nearly two times more nitrogen. Bayesian stable isotope mixing models indicated that C3 plants dominated iguana diets on all islands and showed no evidence for consumption of mice or shearwaters. The iguanas on Allen Cay were ~ 2 times longer (48.3 ± 11.6cm) and ~ 6 times heavier (5499 ± 2847g) than iguanas on other cays and this was likely from marine-derived subsidies from seabird guano which caused an increase in nitrogen concentration in the plants and a resultant increase in the δ15N values across the entire food web relative to non-seabird islands.

Host sex, size, and hemoparasite infection influence the effects of ectoparasitic burdens on free-ranging iguanas.

Investigations focusing on host–ectoparasite interactions in animals have revealed asymptomatic to severe health and fitness consequences suggesting that species mobilize different interspecific response mechanisms. Fewer studies, however, have examined intraspecific responses to ectoparasitic burdens. In this study, we analyzed host health and fitness responses to increasing ectoparasite burdens along with the presence/absence of hemoparasites of free‐ranging insular rock iguanas (Cyclura cychlura) in The Bahamas. Using hematology, plasma biochemistry, as well as body condition and growth rate comparisons, we failed to find significant associations of tick burdens with annual growth rate, corticosterone, packed cell volume, total white blood cell, and heterophil, monocyte, eosinophil or hemoglobin measures. We did, however, find mixed and significant associations of tick burdens with lymphocyte and basophil counts, heterophil‐to‐lymphocyte ratios, and body condition indices. These associations varied by sex, size, and hemoparasite infection status suggesting that different life stages of iguanas may invest differently in immune responses, and impacts may be modulated based on size and sex of hosts, and coinfection status.

Genetic diversity and structure in the Endangered Allen Cays Rock Iguana, Cyclura cychlura inornata.

The Endangered Allen Cays Rock Iguana (Cyclura cychlura inornata) is endemic to the Allen Cays, a tiny cluster of islands in the Bahamas. Naturally occurring populations exist on only two cays (<4 ha each). However, populations of unknown origin were recently discovered on four additional cays. To investigate patterns of genetic variation among these populations, we analyzed nuclear and mitochondrial markers for 268 individuals. Analysis of three mitochondrial gene regions (2,328 bp) and data for eight nuclear microsatellite loci indicated low genetic diversity overall. Estimates of effective population sizes based on multilocus genotypes were also extremely low. Despite low diversity, significant population structuring and variation in genetic diversity measures were detected among cays. Genetic data confirm the source population for an experimentally translocated population while raising concerns regarding other, unauthorized, translocations. Reduced heterozygosity is consistent with a documented historical population decline due to overharvest. This study provides the first range-wide genetic analysis of this subspecies. We suggest strategies to maximize genetic diversity during ongoing recovery including additional translocations to establish assurance populations and additional protective measures for the two remaining natural populations.

Influence of morphological, chemical and physical leaf traits on food selection of a herbivorous iguana from The Bahamas

Abstract:Herbivores are predicted to forage on a variety of plants in order to obtain a nutritionally sufficient diet. Most herbivores, however, forage non-randomly and may be influenced by morphological, chemical and physical traits in their food. We examined the influence of several leaf traits on food selection for the Exuma rock iguana (Cyclura cychlura figginsi). We expected the iguana to prefer leaves with higher nutrient concentration and lower physical defences, such as reflected by high N, P, Ca, K, Mg concentrations and low leaf density and per cent concentrations of cellulose, hemicellulose and lignin, respectively. We quantified selection by examining 30 faecal samples and analysing traits of leaves from the 10 most common plants on the island. Our results showed substantial variability in all measured traits among species but food preference only for less-dense leaves, a good indicator of low leaf toughness. Our results are the first to demonstrate that physical leaf traits can influence food selection in a true herbivorous lizard and offer a basis for future testing.

Staying high and dry: a unique nesting strategy for an insular iguana

Staying high and dry: a unique nesting strategy for an insular iguana

Reptile-associated ticks from Dominica and the Bahamas with notes on hyperparasitic erythraeid mites.

Ticks were collected or recorded from 522 individual reptiles on Dominica and from 658 reptiles from the Bahamas. Two species of ticks were collected on Dominica: Amblyomma antillorum and Amblyomma rotundatum. Similarly, 2 species were collected in the Bahamas: Amblyomma albopictum and Amblyomma torrei. On Dominica, A. antillorum was recorded from 517 Lesser Antillean iguanas (Iguana delicatissima), 2 boa constrictors (Boa nebulosa), 1 Antilles snake (Alsophis sibonius), and 1 Dominican ground lizard (Ameiva fuscata), whereas A. rotundatum was recorded from 1 Lesser Antillean skink (Mabuya mabouya). In the Bahamas, A. albopictum was recorded from 131 Andros iguanas (Cyclura cychlura cychlura), 271 Exuma Island iguanas (Cyclura cychlura figginsi), and 1 Andros curlytail lizard (Leiocephalus carinatus coryi), whereas A. torrei was recorded from 255 Exuma Island iguanas. In the Bahamas, A. albopictum parasitized iguanas on Andros Island and the central Exuma Islands, and A. torrei parasitized iguanas in the southern Exumas. An exception to this trend was that A. torrei was collected from iguanas on Pasture Cay in the central Exumas, an anomaly that is explained by the fact that iguanas (with attached ticks) on Pasture Cay were introduced by humans in the past from islands further south. External hyperparasitic larval erythraeid mites ( Leptus sp.) were recorded from A. torrei in the Bahamas.

Inferred vs realized patterns of gene flow: an analysis of population structure in the Andros Island Rock Iguana.

Ecological data, the primary source of information on patterns and rates of migration, can be integrated with genetic data to more accurately describe the realized connectivity between geographically isolated demes. In this paper we implement this approach and discuss its implications for managing populations of the endangered Andros Island Rock Iguana, Cyclura cychlura cychlura. This iguana is endemic to Andros, a highly fragmented landmass of large islands and smaller cays. Field observations suggest that geographically isolated demes were panmictic due to high, inferred rates of gene flow. We expand on these observations using 16 polymorphic microsatellites to investigate the genetic structure and rates of gene flow from 188 Andros Iguanas collected across 23 island sites. Bayesian clustering of specimens assigned individuals to three distinct genotypic clusters. An analysis of molecular variance (AMOVA) indicates that allele frequency differences are responsible for a significant portion of the genetic variance across the three defined clusters (Fst = 0.117, p0.01). These clusters are associated with larger islands and satellite cays isolated by broad water channels with strong currents. These findings imply that broad water channels present greater obstacles to gene flow than was inferred from field observation alone. Additionally, rates of gene flow were indirectly estimated using BAYESASS 3.0. The proportion of individuals originating from within each identified cluster varied from 94.5 to 98.7%, providing further support for local isolation. Our assessment reveals a major disparity between inferred and realized gene flow. We discuss our results in a conservation perspective for species inhabiting highly fragmented landscapes.

Physiological effects of tourism and associated food provisioning in an endangered iguana.

Deliberately feeding wildlife is an increasingly popular tourism-related activity despite a limited understanding of long-term impacts on the species being fed. As a result, tourist behaviours that may have adverse impacts on imperiled species have often been encouraged without the necessary evaluation or oversight. Here, we report the responses of Northern Bahamian Rock Iguanas (Cyclura cychlura) to human-visitation pressure and associated food provisioning. We compared a variety of blood chemistry parameters of iguanas subjected to supplemental feeding at popular tourist destinations with iguanas occurring on islands where supplemental feeding does not take place. We demonstrate that male and female iguanas inhabiting tourist-visited islands where supplemental feeding occurs do not differ in body condition or baseline stress and stress response (determined by corticosterone levels) compared with iguanas from non-visited islands. Both males and females from tourist-visited sites experienced a greater incidence of endoparasitic infection and atypical loose faeces. Indicators of dietary nutrition, including glucose, potassium, and uric acid values, also differed for both sexes from tourist-visited and unvisited islands. Male iguanas from visited islands differed significantly from those on non-visited islands in calcium, cholesterol, cobalt, copper, magnesium, packed cell volume, selenium, and triglyceride concentrations, whereas female iguanas from visited islands differed significantly in ionized calcium. Although the interpretation of these differences is challenging, chronic biochemical stressors could compromise individual health over time or decrease survivorship during periods of environmental stress. We suggest protocols that can be adopted throughout the region to ensure that supplemental feeding has fewer impacts on these long-lived iguanas.

OCULAR HEALTH ASSESSMENT, TEAR PRODUCTION, AND INTRAOCULAR PRESSURE IN THE ANDROS ISLAND IGUANA (CYCLURA CYCHLURA CYCHLURA)

The purpose of this study was to assess the ocular health of a wild population of Andros Island iguanas (Cyclura cychlura cychlura) and determine reference values for tear production and intraocular pressure (IOP) for this species. Fifty-two iguanas, 20 males and 32 females, ranging in size from 11.1- to 51.0-cm snout-to-vent length (SVL), were included in the sample set, with measurements obtained from each eye. No abnormalities were found on ophthalmic examination, with the exception of mild, focal chemosis in one individual and periocular ticks in 52% of iguanas. Tear production was measured using the phenol red thread test, and IOP was measured using the TonoVet rebound tonometer set on the P (undefined species) setting. No significant difference was found between males and females for either measurement. No significant difference was found between right and left eyes for intraocular pressure; however, a significant difference was found between eyes for tear production values. The mean (+/- SD) of IOP in the left and right eyes were 4.77 +/- 1.88 mm Hg and 5.12 +/- 2.52 mm Hg, respectively, with a range of 1-11 mm Hg. The mean (+/- SD) of tear production in the left and right eyes were 10.63 +/- 6.89 mm/15 sec (range 1-28 mm/15 sec) and 12.44 +/- 7.52 mm/15 sec (range 1-23 mm/15 sec), respectively. A positive correlation was found between SVL and all ocular parameters measured. This study provides an assessment of ocular health, as well as baseline values for IOP and tear production, in the Andros Island iguana.

Hosts of Amblyomma dissimile Koch, 1844 and Amblyomma rotundatum Koch, 1844 (Acari: Ixodidae)

Host records of Amblyomma dissimile Koch, 1844 and Amblyomma rotundatum Koch, 1844 from the literature were critically reviewed. A total of 417 records on 101 species of tetrapods, and 193 records in 74 species of tetrapods were determined for A. dissimile and A. rotundatum, respectively. Aves have been found only once infested with A. dissimile. This tick has been detected on four species of Bufonidae, while A. rotundatum has been recorded on 13 species from six families of Anura. Crocodilia has been recorded infested by A. rotundatum (captive host, one species) and A. dissimile (two species). Sixteen species of Mammalia from ten families and eight species from eight families have been found infested with A. dissimile and A. rotundatum, including humans, respectively. A total of 63 species of Squamata (10 families) were found infested with A. dissimile, while the corresponding numbers for A. rotundatum are 45 species in nine families. A total of 15 species of Testudines (four families) and nine species (three families) have been found infested with A. dissimile and A. rotundatum, respectively. When infestation on captive and laboratory hosts were excluded from the analysis the number of species naturally infested with A. dissimile diminished to 88 and 58 for A. rotundatum. However, natural hosts infested with larvae, nymphs and adults of A. dissimile are Bufo marinus (Linnaeus), Bufo peltocephalus Tschudi, Proechimys semispinosus (Tomes), Boa constrictor Linnaeus, Epicrates striatus (Fischer), Oxybelis aeneus (Wagler), Cyclura cychlura (Cuvier), Iguana iguana (Linnaeus), Tupinambis teguixin (Linnaeus) and Trachemys scripta (Thunberg), but the commonest hosts harbouring all parasitic stages are B. marinus, B. constrictor and I. iguana. Hosts for all parasitic stages of A. rotundatum are B. marinus, Bufo schneideri Werner and B. constrictor, although records on B. marinus are considerably higher than the records on the other two hosts. The contribution of sheep and Hydrochoerus hydrochaeris (Linnaeus) as hosts of A. dissimile, and Dasypus novemcinctus Linnaeus as host of A. rotundatum, were overestimated in previous studies. The ample host-range of these tick species may partly explain their wide distribution from southern U.S.A. to northern Argentina, but there are also chances that more than one species are represented under the names A. dissimile and A. rotundatum.

The Influence of Landscape Heterogeneity and Dispersal on Survival of Neonate Insular Iguanas

Abstract The relationship between dispersal and predator–prey interactions in heterogeneous landscapes is an underappreciated factor influencing species persistence. This relationship, however, is critical for understanding population dynamics and for implementing management strategies for species. We investigated the influence of habitat heterogeneity and dispersal patterns on neonate survival for the iguana Cyclura cychlura cychlura inhabiting Andros Island in the Bahamas. Contrary to our hypothesis, there was a clear survival advantage for neonates that spent more time in open mangrove habitat than relatively more closed-canopy habitats, most likely because of fewer primary predators in mangroves relative to other habitats. Snake predation was the most significant cause of mortality for neonates dispersing away from nest sites and was highest during the first week after release. The probability of survival to 28 days ranged from 16.7 to 28.4%. Most neonates displayed rapid, nearly linear movements away...

Juvenile Survival in the Allen Cays Rock Iguana (Cyclura Cychlura Inornata)

Study of the population biology of the Allen Cays Rock Iguana (Cyclura cychlura inornata) in the Bahamas has been ongoing since 1980, and most aspects of the reproductive biology and demography of this taxon have been elucidated. I used recapture data to produce the first estimate of juvenile survival. Of 16 juveniles captured and marked at age 0.5 years, nine were alive at age 12.5 yrs (typical age at maturity), an annualized rate of 95.3%. Of four other juveniles marked at age 1.5 yrs, three were still alive ten years later, an annual rate of 97.2%. These rates are the highest recorded for juveniles of any lizard. A life table generated for this taxon demonstrates extreme longevity, very high survival throughout life, greatly delayed maturity (longer than for any studied lizard), extreme iteroparity, and low reproductive output. Net reproductive rate (R0 = 3.4) and cohort generation time (21 yrs) match the 3.2-fold population size increase estimated between 1982 and 2004.

Geographic variation in nesting behavior and reproductive biology of an insular iguana (Cyclura cychlura)

Intraspecific comparisons among geographically separated populations of wide-ranging species are particularly useful in elucidating variation in behavioral and reproductive life histories resulting from proximate and ultimate causes. From 2001 to 2004, we investigated geographic variation in nesting behavior and reproductive biology of a large-bodied Bahamian iguana ( Cyclura cychlura Cuvier, 1829) inhabiting two distinct island systems varying in area, topography, and rainfall. Studies of C. cychlura cychlura were conducted on Andros Island (approx. 6000 km2; annual rainfall 1100 to 1300 mm) and the results were compared with those for C. cychlura inornata Barbour and Noble, 1916 inhabiting two cays (each &lt;4 ha; annual rainfall &lt;600 mm) in the northern Exuma Island chain (approx. 140 km distant). Female iguanas from Andros Island initiated oviposition 5 to 6 weeks earlier than females from the Exumas. The Andros Island population deposited eggs primarily in termitaria, whereas the lizards in the Exumas deposited eggs in subterranean sand chambers. Female iguanas from Andros deposited significantly more eggs per clutch, heavier total clutches, and wider eggs than conspecifics from the Exumas. Despite egg size differences, hatchling snout–vent length and body mass per clutch did not differ significantly between the Andros and Exuma populations. Our results support the hypothesis that proximate environmental factors play an important role in determining geographic variation associated with not only reproductive output but also reproductive behavior.

Changes in sex ratio over time in the endangered iguana Cyclura cychlura inornata

Changes in sex ratio of a population over time can indicate possible conservation concerns. Using population estimates for males and females, we examined changes in the sex ratio of two populations of the endangered Allen’s Cay Rock Iguana ( Cyclura cychlura inornata Barbour and Noble, 1916) in the Bahamas over nearly 25 years. The sex ratios of both populations changed from strongly male-biased early in the study to nearly 1:1 in recent years. We hypothesize that this shift has occurred because of the recovery of these populations from intense harvesting (particularly of females) over the previous 100 years and, more recently, because of the removal of large males from the islands either by poachers or by tourists.

Long-term trends in the demography of the Allen Cays Rock Iguana ( Cyclura cychlura inornata): Human disturbance and density-dependent effects

Allen Cays Rock Iguanas ( Cyclura cychlura inornata) are native to two small islets (Leaf and U Cay) in the north-central Bahamas. These populations were nearly extirpated in the early 1900s because of heavy hunting pressure (for food), but increased to a total of ca. 150 lizards in 1970, and now number over 500 (not including juveniles). Over the past several decades poaching has declined, but tourist visitation (including nearly daily supplemental feeding of iguanas) has increased. To examine human impacts on the demography of these iguanas, survival, population growth rates, and population sizes for subadult and adult (>25 cm snout-vent length) males and females on the two cays were estimated based on mark–recapture data collected over a 25-year period (1980–2004). As predicted, annual survival probability was higher on U Cay (with less human visitation) than on Leaf Cay, was higher in females than in males (which are bolder), and exhibited a declining trend. Both populations more than doubled during this study, but population growth rates declined to near zero in recent years. These data reflect the importance of human impacts, but also suggest that the populations may be nearing carrying capacity. The rapid population growth observed on these cays, and that seen for several other translocated iguana populations, suggest that if unnatural causes of mortality are reduced or eliminated, island populations of iguanas are capable of rapid recovery. The inexpensive establishment of assurance colonies on undisturbed “islands” should be considered for any comprehensive management plan for endangered species of iguanas.

Health Assessment of Allen Cays Rock Iguana, Cyclura cychlura inornata

ABSTRACT The Allen Cays rock iguana, Cyclura cychlura inornata, though endangered, has stable and natural populations in the Allen Cays, in the Exuma Islands of the northern Bahamas. Thirty-seven animals (20 male and 17 female) were sampled during a long-term mark and recapture study in May 2004. Complete blood counts were performed on 18 animals and plasma biochemical analyses were performed on all 37 animals. Results of hematologic and plasma biochemical analyses for all animals showed that male Cyclura cychlura inornata had significantly lower levels of aspartate aminotransferase than female Cyclura cychlura inornata. Fecal parasite screens were completed on six animals and fecal cultures were performed on 17 animals. Oxyurid sp. were found in four of six fecal samples, and multiple bacteria, including Salmonella spp., were isolated from cloacal cultures.

Home range and habitat associations of a Bahamian iguana: implications for conservation

The Bahamian Andros iguana (Cyclura cychlura cychlura) is an endangered lizard threatened by habitat loss, illegal hunting, impacts from historic large-scale logging practices and predation by feral animals (e.g. cats, dogs and hogs). There is interest by local and national conservation organisations to demarcate protected areas for the iguana in the southern portion of its range. However, no life history information is available for the lizard. In order to provide data that can be applied in a science-based management strategy for the Andros iguana, we investigated seasonal variation in home-range size and habitat selection of the iguana using radio telemetry. Home ranges were the largest reported to date for free-ranging Cyclura iguanas (Fixed 95% Kernel maximums: 30.58 ha for males, 5.63 ha for females). Habitat selection using the Euclidean Distance method revealed that open pine was the only habitat type out of four where iguanas occurred more than expected by chance. However, the pair-wise comparisons of habitat types reveal that iguanas were found significantly closer to open pine and shrubland than to closed pine. We failed to uncover selection of cumulative home-range placement throughout our multi-habitat study areas. Conservation implications of the dynamic seasonal home-range fluctuations and habitat usage are discussed and recommendations are offered for establishing protected areas.