PROJECT DESCRIPTION
BACKGROUND
The Hierro giant lizard (Gallotia simonyi) is the most threatened reptile in Europe and one of five most threatened species in the world. As a consequence, it is listed in the Habitats Directive as a priority species. Although it was originally widespread over much of the island of Hierro in the Canaries, its distribution is now confined to a mere hectare situated along an inaccessible cliff edge. Here the last remaining 200 individuals can be found.
Numerous factors have led this species to the brink of extinction: severe degradation of its habitat, losses due to capture of individual specimens, introduction of predators on the island and competition with the Canarian lizard, which is widespread in the area. The limited number of surviving individuals is a major problem for the long-term viability of the species.
OBJECTIVES
The project aimed to expand the lizard's territory and increase its existing wild population. This would be done through a series of onsite monitoring and surveillance measures, and will be complemented by a captive breeding programme. It was intended that the progeny of this programme would eventually be reintroduced into other areas where suitable habitat has been identified.
RESULTS
The project significantly increased knowledge of the management of this species as well as established a suitable captive breeding population.
Monitoring of the species helped determine the exact distribution area of the species in la Fuga de la Gorreta (sole population distribution); it was slightly bigger than it was thought, and, as a result, the protected area needed to be modified. Surveys carried out made it possible to determine that the species distribution area covered 3.65 hectares between 100 and 500 m above sea level as far as the lower slopes of the Tibataje cliffs. Estimations of the total population ranged from 120 to 150 individuals, a lower figure that initially supposed.
Studies on feeding of the natural population were carried out through the collection and analysis of faeces and through direct observation. The results confirmed that an adult lizard typically grazes on a total of 16 plant species, including lichens. Although they have a tendency to eat plants, they are omnivores and also eat arthropods and small vertebrates.
The project consolidated the captive breeding programme, which had started the year before. Genetic studies showed a low genetic variability in the captive population, which explained problems with fertility and malformations in individuals. A specific programme devised to correct these problems enabled researchers to rear a healthy captive population, with a population of more than 200 individuals by the end of the project (nearly twice the size of the non-captive population).
Biological studies on captive populations revealed the behaviour patterns of the species (e.g. the emission of sounds by the species), health and sanitary conditions, competition strategies with other lizard species, data on running speed and thermic and food preferences within the natural diet.
Habitat studies determined that availability of natural refuges was not a problem either in current distribution areas or in areas foreseen for reintroductions. The place selected for reintroduction (‘La Dehesa’) was also deemed suitable in terms of food availability. Carrying capacity of the area was estimated at 67.64 individuals/ha. The main predators (kestrels, crows and gulls) were not considered critical pressure on the species. Feral cats were studied to determine their behaviour.
Animals bred in captivity were prepared to survive in similar conditions to those in the reintroduction areas. Two lizards were released with radio-tracking transmitters (the first time such tracking has been carried out for this species). Follow up of these specimens showed that they were perfectly adapted to the wild and they gained weight. However, one of the individuals was predated by a cat.
As regards public awareness, several scientific papers were published in specialised journals and an international meeting was held in El Hierro in March 1997 to present the results of the project to scientific and conservation institutions. A video on the project was produced in collaboration with the Spanish TV. The project also produced three posters, two t-shirts, a booklet, a leaflet and stickers. Most of these materials were distributed at schools on the island.The project significantly increased knowledge of the management of this species as well as established a suitable captive breeding population.
Monitoring of the species helped determine the exact distribution area of the species in la Fuga de la Gorreta (sole population distribution); it was slightly bigger than it was thought, and, as a result, the protected area needed to be modified. Surveys carried out made it possible to determine that the species distribution area covered 3.65 hectares between 100 and 500 m above sea level as far as the lower slopes of the Tibataje cliffs. Estimations of the total population ranged from 120 to 150 individuals, a lower figure that initially supposed.
Studies on feeding of the natural population were carried out through the collection and analysis of faeces and through direct observation. The results confirmed that an adult lizard typically grazes on a total of 16 plant species, including lichens. Although they have a tendency to eat plants, they are omnivores and also eat arthropods and small vertebrates.
The project consolidated the captive breeding programme, which had started the year before. Genetic studies showed a low genetic variability in the captive population, which explained problems with fertility and malformations in individuals. A specific programme devised to correct these problems enabled researchers to rear a healthy captive population, with a population of more than 200 individuals by the end of the project (nearly twice the size of the non-captive population).
Biological studies on captive populations revealed the behaviour patterns of the species (e.g. the emission of sounds by the species), health and sanitary conditions, competition strategies with other lizard species, data on running speed and thermic and food preferences within the natural diet.
Habitat studies determined that availability of natural refuges was not a problem either in current distribution areas or in areas foreseen for reintroductions. The place selected for reintroduction (‘La Dehesa’) was also deemed suitable in terms of food availability. Carrying capacity of the area was estimated at 67.64 individuals/ha. The main predators (kestrels, crows and gulls) were not considered critical pressure on the species. Feral cats were studied to determine their behaviour.
Animals bred in captivity were prepared to survive in similar conditions to those in the reintroduction areas. Two lizards were released with radio-tracking transmitters (the first time such tracking has been carried out for this species). Follow up of these specimens showed that they were perfectly adapted to the wild and they gained weight. However, one of the individuals was predated by a cat.
As regards public awareness, several scientific papers were published in specialised journals and an international meeting was held in El Hierro in March 1997 to present the results of the project to scientific and conservation institutions. A video on the project was produced in collaboration with the Spanish TV. The project also produced three posters, two t-shirts, a booklet, a leaflet and stickers. Most of these materials were distributed at schools on the island.