Blue iguana

Appearance

The blue iguana is the largest native land animal on Grand Cayman with a total nose-to-tail length of 5 ft and weighing as much as 30 lb . It may be the heaviest species of iguana and most massive lizard in the Western Hemisphere. Its body length is 20–30 inches with a tail equal in length. The blue iguana's toes are articulated to be efficient in digging and climbing trees. Although not known to be arboreal, the blue iguana has been observed climbing trees 15 feet and higher. The male is larger than the female by one third of his body size. The mature male's skin color ranges from dark grey to turquoise blue, whereas the female is more olive green to pale blue. Young animals tend to be uniformly dark brown or green with faint darker banding. When they first emerge from the nest the neonates have an intricate pattern of eight dark dorsal chevrons from the crest of their necks to their pelvic area. These markings fade by the time the animal is one year old, changing to mottled gray and cream and eventually giving way to blue as adults. The adult blue iguana is typically dark gray matching the karst rock of its landscape. The animal changes its color to blue when it is in the presence of other iguanas to signal and establish territory. The blue color is more pronounced in males of the species. Their distinctive black feet stand in contrast to their lighter overall body color.

Blue iguanas are sexually dimorphic; males are larger and have more prominent dorsal crests as well as larger femoral pores on their thighs, which are used to release pheromones.

Status

The blue iguana is listed as endangered on the IUCN Red List. The population is restricted to the eastern interior of Grand Cayman, where it had been reduced to a critically low level, only three animals having been observed before the survey in 1988....hieroglyph snipped... The range of the blue iguana has contracted significantly over the past 25 years, with many sites once populated now showing no signs of iguanas. Surveys in 2003 indicated a total population in the range of 5–15 individuals. By 2005 the unmanaged wild population was considered to be functionally extinct. The species is one of the most endangered animals on Earth. A further blow to the dwindling population came in May 2008 when six individuals were found butchered in a nature preserve.

As the blue iguana consumes a variety of plant material, favoring fruits and flowers over leaves and stems when available, it is valuable on Grand Cayman as a seed disperser throughout its range. A study in 2000 by Dr Allison Alberts revealed that seeds passing through the digestive tracts of ''Cycluras'' germinate more rapidly than those that do not. These seeds in the fruits consumed by the blue iguana have an adaptive advantage by sprouting before the end of very short rainy seasons. The blue iguana is also an important means of distributing seeds to new areas and, as the largest native herbivore of Grand Cayman's ecosystems, it is essential for maintaining the delicate balance between climate and vegetation necessary to survive under harsh conditions.

Restored free-roaming subpopulations in the Queen Elizabeth II Botanic Park and the Salina Reserve numbered approximately 125 individuals in total after an initial release in December 2005. The restored subpopulation in the Queen Elizabeth II Botanic Park has been breeding since 2001, and the subpopulation in the Salina Reserve was deemed to be breeding in 2006 after a nest of three hatched eggs was discovered in the wild. As of April 2007, after another large-scale release, there were 299 blue iguanas living in the wild, with hundreds more being raised in captivity on Grand Cayman. In late 2012, the blue iguana Recovery Program estimated that the wild population had risen to approximately 750 individuals, and the IUCN subsequently downlisted the species from critically endangered to endangered.

Reproduction

Mating occurs from May through June. Copulation is preceded by numerous head-bobs on the part of the male, who then circles around behind the female and grasps the nape of her neck. He then attempts to restrain the female in order to maneuver his tail under hers to position himself for intromission. Copulation generally lasts from 30 to 90 seconds, and a pair is rarely observed mating more than once or twice a day. A clutch of anywhere from 1 to 21 eggs are usually laid in June or July depending on the size and age of the female, in nests excavated in pockets of earth exposed to the sun. Several exploratory nests are begun before one is completed. These burrows can range from 16 inches to over 60 inches in length, with an enlarged chamber at its terminal portion to allow the female to turn around. The temperature within nests that have been monitored by researchers remained a constant 32 °C throughout the incubation period which ranges from 65–90 days. The blue iguana's eggs are among the largest laid by any lizard.

Individuals are aggressively territorial from the age of about three months onward. Females occupy overlapping areas of the order of 0.6 acres seemingly regardless of age, while males occupy progressively larger and more extensively overlapping territories as they age and grow.

Food

Like all ''Cyclura'' species, the blue iguana is primarily herbivorous, consuming leaves, flowers, and fruits from over 45 species of plant. This diet is very rarely supplemented with insect larvae, crabs, slugs, dead birds, and fungi. The iguanas are presented with a special problem for osmoregulation: plant matter contains more potassium and as it has less nutritional content per gram, more must be eaten to meet the lizard's metabolic needs. As they are not capable of creating urine more concentrated than their bodily fluids, they excrete nitrogenous wastes as uric acid salts through a salt gland in the same manner as birds. As a result, they have developed this lateral nasal gland to supplement renal salt secretion by expelling excess potassium and sodium chloride.

Longevity in the wild is unknown but is presumed to be many decades. A blue iguana named "Godzilla" captured on Grand Cayman in 1950 by naturalist Ira Thompson was imported to the United States in 1985 by Ramon Noegel and sold to reptile importer and breeder, Tom Crutchfield in 1990. Crutchfield donated Godzilla to the Gladys Porter Zoo in Brownsville, Texas in 1997 and the lizard remained there until its death in 2004. Thompson estimated Godzilla to be 15 years of age at the time of his capture. At an estimated 69 years of age , Godzilla may be the world's longest-living lizard for which there is reliable record. A closely related Lesser Caymans iguana has been documented as living 33 years in captivity.

Uses

Habitat destruction is the main factor threatening imminent extinction for this iguana. Land clearance within remnant habitat is occurring for agriculture, road construction, and real estate development and speculation. Conversion of traditional crop lands to cattle pasture is also eliminating secondary blue iguana habitat.

Predation and injury to hatchlings by rats, to hatchlings and sub-adults by feral cats, and killing of adults by roaming dogs are all placing severe pressure on the remaining wild population. Automobiles and motorscooters are an increasing cause of mortality as the iguanas rarely survive the collisions. Trapping and shooting is a comparatively minor concern, but occasional trapping continues despite legal protection and sustained efforts to increase public awareness.

The common Green Iguana, , has been introduced from Honduras and is well-established on Grand Cayman as an invasive species. It far outnumbers the endemic blue iguana. No direct negative consequences of this introduction on the blue iguana are known, but the mere presence of the Green Iguana confuses public attitudes and understanding. For example, the people of the island are told that blue iguanas are endangered and rare, and when they subsequently see large numbers of the introduced Green Iguana, they do not understand the difference.

Blue iguanas used to regularly be sold to tourists as pets, as their rarity made them appealing to exotic-animal collectors, despite this being illegal under the CITES treaty. In 1999 a World Wildlife Fund international conservation officer, Stuart Chapman, said, "The British government has turned a blind eye for over 20 years to these overseas territories which are home to many rare and endangered species. Many of these face extinction if Britain fails to honour its treaty obligations. The British Caribbean islands are extremely rich in biodiversity with many critically endangered species that are unique to the islands—yet there is virtually zero enforcement or implementation of CITES."

In May 2008, six blue iguanas were found dead in the preserve within Queen Elizabeth II Botanic Park on Grand Cayman. The iguanas were apparently killed by human vandals armed with knives and two of the slaughtered animals were gravid females about to lay eggs.

The wild population of blue iguanas had been reduced from a near island-wide distribution to a non-viable, fragmented remnant. By 2001, no young hatched in the unmanaged wild population were surviving to breeding age, meaning the population was functionally extinct, with only five animals remaining in the wild.