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Ctenosaura bakeri 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Iguanidae

Scientific Name: Ctenosaura bakeri Stejneger, 1901
Common Name(s):
English Utila Spiny-tailed Iguana, Baker's Spiny-tail Iguana, Swamper, Wishiwilly
Spanish Garrobo
Synonym(s):
Enyaliosaurus bakeri (Stejneger, 1901)
Taxonomic Notes: Synonym = Enyaliosaurus bakeri (Stejneger, 1901). Not a basionym.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(i,ii,iii,v) ver 3.1
Year Published: 2018
Date Assessed: 2018-02-04
Assessor(s): Maryon, D., Ardon, D., Martinez, A., Clayson, S. & Pasachnik, S.
Reviewer(s): Grant, T.D.
Contributor(s): Brown, T., Lee, D., Albergoni, A., Black, H. & Lonsdale, G.
Justification:
The Útila Spiny-tailed Iguana is known only from the island of Útila, Honduras. Total known extent of occurrence is 41 km2. The iguana and its eggs are harvested heavily and sold both locally and on the adjacent mainland. Other primary threats to the population are habitat loss and fragmentation associated with development for tourism; decreasing quality of habitat from introduced invasive vegetation and degradation of nesting habitat due to local and oceanic pollution. The population is currently thought to be declining due to the above threats.
Previously published Red List assessments:

Geographic Range [top]

Range Description:The Útila Spiny-tailed Iguana is known only from the island of Útila, Bay Islands, Honduras. The extent of occurrence is 41 km2. However, suitable mangrove habitat available for Ctenosaura bakeri estimated at less than 8 km2 (D. Maryon, D. Lee and E. Higgins unpublished data 2017). This iguana occurs from sea level up to 20 m asl.
Countries occurrence:
Native:
Honduras (Honduran Caribbean Is.)
Additional data:
Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:41
Continuing decline in extent of occurrence (EOO):YesExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):20
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The total population size is unknown but analyses are currently underway and it is likely to be less than 6,000 individuals (D. Maryon and D. Lee unpublished data 2017). Although more rigorous data are needed, observations suggest the population has continually declined in association with increased habitat degradation and destruction over the last 15 years. The population has also been severely affected by harvesting for human consumption (D. Maryon pers. obs. 2017). Effects of this practice are exacerbated by hunters specifically targeting gravid females, and thus dramatically impacting annual reproduction rates. Genetic variation in the population does not follow a specific geographic pattern indicating that this iguana appears to have been mating randomly across the island (Pasachnik et al. 2009). However, with ever-increasing habitat loss, further fragmentation of local subpopulations appears imminent, and a reassessment is currently underway to establish whether these subpopulations are becoming genetically isolated.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:3000-6000Continuing decline of mature individuals:Yes
Extreme fluctuations:UnknownPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:No
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes

Habitat and Ecology [top]

Habitat and Ecology:The Útila Spiny-tailed Iguana is found primarily in mangrove forests and vegetated sandy shores, though occasionally they can be found in disturbed areas such as coastal/beachfront developments and gardens. They are typically most active during the morning, when adults can be seen basking from 0–15 m above ground in Black (Avicennia germinans), White (Laguncularia racemose), and Red (Rhizophora mangle) Mangrove trees, as well as on the ground. Individuals are commonly observed hiding in the hollows of Black and White Mangrove trees, which they use as retreats. Juveniles occur in both small and large mangrove trees, on the mangrove forest floor, and within coastal beach vegetation shortly after hatching (Schulte and Köhler 2010, D. Maryon pers. obs. 2017). This iguana makes special use of mangrove roots and lagoons by diving into them and swimming or submerging themselves to avoid predation (D. Maryon pers. obs. 2017).

The main breeding season occurs from January to late July and mating occurs on or near the ground in the mangrove forests. Females then migrate from the mangroves to beachfronts to nest in a variety of areas, including those with full sun exposure, under piles of leaf litter and oceanic litter, beneath large beachfront trees, and within short shrub vegetation (D. Maryon pers. obs. 2017). Nesting takes place from February to August. Females lay an average of 11 to 16 eggs in nests that can be up to a few metres long but not more than 60 cm deep (Gutsche 2006, D. Maryon pers. obs. 2017). Double-clutching has been observed in some individuals. The incubation period is approximately 85 days and hatching occurs from April through October. Upon emerging, hatchlings seem to spend little time inhabiting coastal vegetation before dispersing into the mangrove forests, where they are active on the ground, volcanic coralline rocks, and on the branches of trees as they mature (D. Maryon pers. obs. 2017).
Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: Iguanas and their eggs continue to be sought for human consumption year-round and are sold both locally and on the adjacent mainland. Groups of hunters with dogs are reported in mangrove habitats between February and May (D. Maryon pers. obs. 2017), coinciding with the presence of gravid females which are often selectively targeted. Females containing eggs are cooked and eaten as a traditional cultural delicacy, especially throughout the Easter period. From 2006 to 2011, the sex ratio of iguanas became increasingly more male-biased, which may be indicative of increasing hunting pressure on adult females (Pasachnik et al. 2012).

Threats [top]

Major Threat(s): The primary threat to the Útila Spiny-tailed Iguana is habitat loss due to mangrove degradation, deforestation, and fragmentation attributable to infrastructure development for the tourism industry. Mangrove forest habitats are used as garbage dumping sites, and there is a potential risk posed by water contamination from terrestrial landfills and agricultural chemicals (fertilisers and pesticides). Oceanic and local pollution (plastics, polystyrene, etc.) covers sandy beaches, affecting prime nesting sites by obscuring laying sites and also potentially affecting sand and incubation temperatures (D. Maryon pers. obs. 2017). There is extensive deforestation of mangrove habitat for housing and marina construction, and for future potential crop plantations. Mangroves near developed areas and roads are also becoming isolated from their water sources, causing the trees to die and leaving large patches of dead mangrove in dry lagoons. Natural beach habitat is being lost through the removal of vegetation in preparation for development. This coupled with the introduction of invasive alien plants is making beach habitat increasingly unsuitable for egg laying. Cattle have been observed trampling over nests; with expanding agriculture this may become a more prevalent threat in the future (D. Maryon pers. obs. 2017).

Invasive alien predators such as rats and free-roaming dogs and cats are threats to this iguana. Northern Raccoons (Procyon lotor) were also recently observed and may be a potential concern (D. Maryon pers. obs. 2017).

Many native predators of this iguana have been observed and may become out of balance with habitat changes that provides less shelter. Hatchlings in particular are easy prey for: birds, such as Great-tailed Grackle (Quiscalus mexicanus), Common Black Hawk (Buteogallus anthracinus), Great Egret (Ardea alba), and Green Heron (Butorides virescens); snakes, including Salmon-bellied Racer (Mastigodryas melanolomus), Mexican Parrot Snake (Leptophis mexicanus), Mexican Vine Snake (Oxybelis aeneus), Green Vine Snake (Oxybelis fulgidus), and Boa Constrictor (Boa imperator); and lizards, such as Brown Basilisk (Basiliscus vittatus) and Common Spiny-tailed Iguana (Ctenosaura similis) (D. Maryon pers. obs. 2017). The Common Black Hawk, Great Egret, and Boa Constrictor have been observed to prey on adults as well (D. Maryon pers. obs. 2017).

The wide-ranging Common Spiny-tailed Iguana (Ctenosaura similis) is also native to the island but primarily occupies a different habitat niche than C. bakeri. This iguana is capable of hybridizing with the endemic Útila Spiny-tailed Iguana in areas of habitat overlap. Although this is currently occurring too infrequently to greatly threaten this species, hybridization could become a greater problem with increasing habitat destruction (Pasachnik et al. 2009). An updated genetic analysis is currently in progress.

Conservation Actions [top]

Conservation Actions: The Útila Spiny-tailed Iguana is protected by Honduran law through a ban on hunting, in place since 1994, however, actual enforcement of this law is inadequate. The iguana is listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Two local organizations, Kanahau Útila Research and Conservation Facility (Kanahau URCF) established in 2012, and the Útila Iguana Research and Breeding Station (IRBS) established in 1997, work to protect the species through raising awareness in local communities.

Currently, Kanahau URCF and the University of South Wales, United Kingdom, are conducting population, behavioural, and genetic studies on the iguana across the island. This research aims to locate important migration routes of gravid females across the island, identify nesting areas, and assess the size, structure, and current rate of hybridization of the population. All signs of hunting and habitat destruction are recorded. Questionnaires among the local community are used to determine harvesting rates and perceptions of iguanas. An environmental education program in local schools run by Kanahau URCF, in conjunction with the Bay Island Conservation Association and the Útila Whale Shark Oceanic Research Centre, focuses on environment awareness and includes presentations on biology and conservation of the Útila Spiny-tailed Iguanas, their habitats, and other natural resources.

The Útila IRBS has been run by a local non-government organization, The Bay Island Foundation, since 2008. The foundation coordinates a breeding program with captive and wild female iguanas. Captive-hatched juveniles are released on the beaches where the females were captured and in other suitable areas. To date, the survival rate of these released iguanas has not been documented.

Recommended conservation measures include active management and protection of the wild iguana population and their habitats. It is critical that local authorities be supported and encouraged to enforce existing legislation, and prosecute individuals caught hunting or selling iguanas to send a strong local message. Protected areas should be created that include mangrove, coastal nesting habitats, and migration routes to ensure year-round refuge. Given that the entire island is currently under private ownership (with the exception of Turtle Harbour Wildlife Refuge), suitable habitat areas may need to be privately purchased and designated as a reserve. Education of both locals and tourists about the iguana is also crucial for long-term survival. These programs should highlight the endangered status of the species, an understanding of its legal protection, and the environmental and economic benefits of protecting the iguana and its habitat. Environmental tours should be developed to raise tourist’s awareness of iguanas and their fragile ecosystem, which could provide an alternative livelihood to local people. 

Research needs include: 1) continued monitoring of population and habitat trends; 2) further investigation of breeding behaviour and requirements; 3) habitat classification and quantification of the scale and rates of degradation, deforestation, and fragmentation across the entire island; 4) quantifying other potential threats; and 5) a detailed study of the effects of human harvesting.

Citation: Maryon, D., Ardon, D., Martinez, A., Clayson, S. & Pasachnik, S. 2018. Ctenosaura bakeri. The IUCN Red List of Threatened Species 2018: e.T44181A125203850. . Downloaded on 18 September 2018.
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