Long-Term Conservation Management of the Endangered Canarian Lizards Gallotia simonyi and G. bravoana (Fam. Lacertidae) (2006–2024)

Gallotia simonyi and G. bravoana are large lacertids inhabiting the islands of El Hierro and La Gomera, respectively, in the Canary Archipelago. Both species are critically endangered, but over the last several decades, they have been bred in outdoor terraria (G. simonyi since the 1990s and G. bravoana since 2000). In this study: (1) we describe all procedures carried out in the breeding centres and quantitatively analyse the long-term trajectory of breeding success throughout the study period; (2) we examine whether any parental individuals or specific pairs had a stronger influence on the number of successfully hatched offspring; (3) we report the trials of reintroducing individuals into the wild on each island in different years; (4) we provide information on several predator (cat-control) campaigns conducted on each island; (5) we detail the veterinary protocols and the results obtained when assessing the health status of breeding lizards; and (6) we report several educational activities carried out on each island. Gravid females laid eggs in suitable laying boxes; the eggs were then kept inside incubators with controlled temperature and humidity until hatching. Breeding produced 1267 offspring during the years considered for G. simonyi and 499 for G. bravoana. The mean NEL was 8.8 for G. simonyi and 5.2 for G. bravoana, and the mean HO was 6.4 and 3.54, respectively. Both NEL and HO were significantly higher in G. simonyi than in G. bravoana. NEL was significantly influenced by species and year, and by female snout–vent length (SVL) as a covariate, but not by male SVL. HO was significantly affected by year and by both male and female SVL, but not by species. There were significantly higher or lower values of both variables in specific years, but no clear long-term trend. Some breeding pairs had a greater influence on the dependent variables. Reintroduction into the wild has resulted in a currently stable population of G. simonyi on a small islet off the north-western coast of El Hierro, and some individuals are still present at an inland reintroduction site. For G. bravoana, some live specimens have recently been detected at a new reintroduction site. We conclude that: (1) captive breeding has been successfully carried out over the years in both centres; (2) there have been significant differences between the two species in NEL and HO; (3) female SVL was significantly related to both NEL and HO; and (4) reintroduction attempts have been only partially successful in each species. Veterinary monitoring revealed high dehydration tolerance, seasonal fluctuations in microbial flora, previous mineral imbalances that were corrected by improved nutrition, and effective parasite control that maintained overall lizard health. Except for a few individuals, most lizards were in good health.