Population resilience of the Mediterranean monk seal Monachus monachus at Cabo Blanco peninsula

Abstract

Environmental and demographic stochasticity alone can push small populations to extinction. However, some small populations can persist for a long time at a low density, maintaining potential for rapid growth. We investigated the demographic mechanisms underlying the response of the population of the Mediterranean monk seal Monachus monachus on the Cabo Blanco peninsula (Mauritania/Morocco). The population was dramatically reduced after a demographic crash in 1997, which was initially thought to have pushed the population toward extinction. Census data, individual-based data on presence−absence and breeding state data were obtained by direct observation, by photo-identification and through the analysis of video images at the only known breeding sites for the species. We found that the monk seal population at Cabo Blanco is recovering, with means of 31 (24.8, 36.8) sub-adults, 46 (42.3, 49.7) adult females and 39 (29.1, 48.4) adult males using the 2 breeding sites in 2007. The population structure is similar to proportions prior to the mass mortality event. Annual survival probabilities for sub-adults, adult females and adult males were 0.81 (0.676 to 0.904), 0.99 (0.926 to 0.998) and 0.87 (0.81 to 0.94), respectively. At present, juvenile survival is unknown, but the high survival of females and the high breeding potential are likely to be responsible for the population recovery.

The Mediterranean monk seal Monachus monachus: status, biology, threats, and conservation priorities

“…In the North Atlantic, two subpopulations exist: one at Cabo Blanco (also known as Cap Blanc) at the border of Mauritania and Western Sahara (González & Fernandez de Larrinoa , Martínez‐Jauregui et al. ), and one at the archipelago of Madeira (Pires et al. ).…”

“…Since then, the subpopulation has been showing encouraging signs of recovery: in 2013, 159 individual adult seals were identified and it is estimated that approximately 220 seals currently compose the second largest monk seal subpopulation (Martínez‐Jauregui et al. , unpublished data, Fundación para la Conservación de la Biodiversidad y su Hábitat; CBD Habitat). The third largest subpopulation is located in the archipelago of Madeira and numbers approximately 40 monk seals (Pires et al.…”

“…The monk seal populations at Cabo Blanco in the Atlantic (Martínez‐Jauregui et al. ), and at Gyaros Island in the eastern Mediterranean (Karamanlidis et al. ), are the only large extant aggregations of the species that still preserve the structure of a colony; the other subpopulations in the eastern Mediterranean are usually small, fragmented groups of <20 individuals.…”

“…, Martínez‐Jauregui et al. ), in the archipelago of Madeira and in the eastern Mediterranean, monk seals may occupy dozens or even hundreds of caves (Gücü et al. , Karamanlidis et al.…”

Prehistoric and historic distributions of the critically endangered Mediterranean monk seal (Monachus monachus) in the eastern Atlantic

“…), and the Cape Blanco Peninsula on the southern coast of the Western Sahara (Martínez‐Jaurégui et al . ), with occasional records in northern Morocco, Senegal, Gambia, and Cape Verde (Hazevoet , Bayed , Armstrong and Nevin , Johnson et al . ).…”