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

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. © Inter-Research 2012 · www.int-res.com.