Mohamed bin Zayed Species project number 13055714

Ecology and conservation of the emblematic dragon blood tree's gecko (Hemidactylus dracaenacolus) and Grant's leaf-toed gecko (Hemidactylus granti) of Socotra Island

The objectives of this project on the ecology of the Critically Endangered dragon blood tree's gecko (Hemidactylus dracaenacolus) of Socotra Island, Yemen, are collecting distribution and diet data for predicting the occurrence of the species, understanding its ecological limitations and preferences as habitat and diet, and reviewing its conservation status to assist conservation actions. 

This project on the Critically Endangered dragon blood tree's gecko (Hemidactylus dracaenacolus) and the Grant's leaf-toed gecko (Hemidactylus granti) will explore the Diksam and Haggeher mountains of the Socotra Island, a UNESCO world natural heritage site included in the Horn of Africa Biodiversity Hotspot.

The six main objectives of the present project are to:

1) Collect presence point data. There are very few presence data available in the bibliography for these two species, even fewer if we consider that most were not genetically confirmed. During the field expedition to Socotra, presence data will be collected with GPS precision for both taxa and a certain identification of the species will be performed based on detailed observation and photographic documentation of all specimens found.

2) Characterize habitat and microhabitat. Habitat and microhabitat descriptors will be collected during fieldwork, which will contribute for the accurate characterisation of selected features for each species.

3) Derive predictive models of occurrence. We will combine presence data, based on bibliography and data collected during fieldwork, with high resolution layers of environmental factors (topography, solar radiation, vegetation cover) using Maxent modelling software to quantify relationships between species presence and environmental variability. This will result in a map of probability of occurrence, which will be useful for conservation purposes as it might identify possible new areas where the target species are likely to be present. It will also measure the importance of each environmental factor on the distribution of each species.

4) Identify contact zone and areas of sympatry. Combination of the predictive models for both species will allow identifying the contact zone areas between these geckos and if sympatric areas would be possible between them. This will test if the presence of H. granti is limiting the presence of H. dracaenacolus at higher altitudes by competition or vice-versa.

5) Study the diet. Faecal pellets will be collected from both species and tissue analyzed with stable isotopes to understand if the two species ecological feeding niches are different or overlapping. This will gives clues to understand if competition for feeding resources might occur and will help to explain the species distribution patterns.

6) Produce data for conservation status assessments. The information gathered and results obtained will be used to redefine the areas of occupancy (AOO) and extent of occurrence (EOO) for H. dracaenacolus and H. granti and compare with previous values to check if those are declining or not, a valuable information for the next conservation status assessment.