Cyclura stejnegeri (iguana de Mona)

Cyclura stejnegeri (Mona Rhinoceros Iguana/ Mona ground iguana)

Cyclura stejnegeri (Mona Rhinoceros Iguana/ Mona ground iguana)

Family: Iguanidae

Mona Island rhinoceros iguana is one of our species of herpetological fauna (reptiles and amphibians) endemic to that island, which means that it exists nowhere else in the world. This animal is a reptile and its scientific name is Cyclura stejnegeri; (Cyclas = gold border, ura = tail), which refers to the dorsal crest of its tail, and stejnegeri in honor of L. Stegneger, a famous scientist of the early 20th century. This iguana belongs to a group of lizards from the West Indies called rock iguanas. All populations of this species are considered threatened or endangered.

Iguanas similar to ours can still be found in Cuba (Cyclura nubila), Jamaica (C. carinata), Hispaniola (C. cornuta), and Anegada (C. pinguis). The latter used to live in Puerto Rico, but disappeared probably with arrival of the Spaniards.

What is the Mona island rhinoceros iguana like?
Our Mona island rhinoceros iguana is the largest lizard found in Puerto Rico. It reaches 1.3 meters in length, of which half is for the tail. Its body and legs are robust. Its head is large, with bony bumps and has small horn at the tip of the snout. A dorsal crest goes from the head to the tail. Its body is olive green or grayish olive, and sometimes has brown or blue lines across. These lines are more conspicuous in young animals than in adults.

This species should not be confused with another lizard introduced by pet shops, the green iguana or gallina de palo (iguana iguana). It is a native of South America and has been introduced in many Caribbean islands. It has a bright green color with black or brown lines. This animal is abundant in Cayo Icacos, where it was introduced some time ago.

On the other hand, the island of Magueyes in La Parguera has a large population of the Cuban iguana (Cyclura nubila) introduced in 1960 when the island was operating a zoo. It is similar to the Mona island rhinoceros iguana but lacks the small piece of skin at the tip of the snout, and its body is less robust.

How does the iguana reproduce?
This animal is oviparous: its offspring are born from eggs. It reproduces only once a year. In the first week of June, the iguana mates and after two to four weeks lays about a dozen eggs in a nest it builds by digging a tunnel in the ground that is large enough for the animal to fit in. After laying the eggs, it covers the entrance to the tunnel leaving an air space between the ground and eggs. This space is crucial so that the offspring can get rid of the shell. There is no care after the nest is covered. Eggs hatch after three months and the small iguanas 25-30 centimeters (10-12 inches) long, dig a tunnel to reach the surface. Iguanas reach reproductive age when they are four or five years old.

What do iguanas feed on?
Mona island rhinoceros iguana is herbivorous-omnivorous, which means it feeds mostly on plant matter, although it can eat animal matter. It eats fruits that fall to the ground and leaves they tear from bushes. Occasionally, it feeds on crabs and insect larvae.

What threatens Mona`s population?
The causes that have led to the deterioration of the iguana populations are all associated with human activities. Mona island, during Taíno times and then during Spanish times, was used as a port for obtaining on water when traveling in the West Indies. Spaniards released goats and pigs with the idea that they would feed on them in future trips, establishing a feral population in a short time.

These mammals were not compatible with the system in Mona island and have caused a deterioration of the vegetation, modifying, and eating plants the iguanas feed on. When feeding, goats form a shepherding layer devoid of leaves which prevents the iguana from having food available at a low altitude. They also feed on fruit from the floor; therefore, the food for iguanas has also decreased. With their weight, goats can bring down the roof of the iguana’s nests and destroy the eggs.

Pigs uproot and feed on the roots of many plants, eliminating the plants most desired by iguanas. They are being replaced by other thorny, poisonous, or less nutritious plants. But the greatest effect of pigs is the predation of eggs. They dig nests and consume iguana eggs. Sometimes, they have eliminated up to 15 nests from one place (15 nests x 12 eggs = 180 small iguanas that are never born). This occurs to a greater extent in years of little rain. Another predator that was introduced about 30 years ago is the domestic cat. This presents a danger because it could kill the small iguanas, those that are less than a year old.

How can we help avoid the extinction of this species?
Avoid annoying, following, or harassing the iguanas. Some iguanas around the facilities at Playa Sardinera have adapted to the presence of humans so it is easy to feed them and take pictures near them. However, it is not our intention to domesticate other iguanas because it is not their natural behavior.

Courtship and nesting activities of iguanas are crucial for the survival of the population. From June to November, iguanas are in their reproductive period. The presence of humans near them may affect courtship activities as well as their building nests or laying eggs. That is why during this time visitors will have to limit their movement to sidewalks, roads, and beaches, and not venture into the forest.

Nesting sites are not detectable by visitors; only an experienced researcher can identify them. If a person steps on a nest, his weight will collapse the air chamber in the nest and destroy the eggs. For every nest that is destroyed, up to 12 new iguanas are lost. This will affect the possible recovery of the species.

What laws protect the Mona island rhinoceros iguana?
Mona island rhinoceros iguana is considered an endangered species and is protected under the U.S. Endangered Species Act of 1973. Anyone who disturbs injures, or kills an iguana may be fined up to a maximum of $30,000 and/or may have to serve one year in prison. Mona island is considered a critical habitat for this and other endangered species; therefore, anyone who harms this habitat could also be penalized under this Act.

Ley de Vida Silvestre (Ley 70 de 1977) [Wildlife Act 70 of 1977] and Puerto Rico Forest Act (No. 133 of 1975) protect all fauna and flora in the country. These consider any organism in its natural state as national heritage; therefore, it belongs to and is for the enjoyment of the people of Puerto Rico.

Author: Grupo Editorial EPRL
Published: August 27, 2014.

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