On the Challenge of Interpreting Census Data: Insights from a Study of an Endangered Pinniped

摘要: Population monitoring is vital for conservation and management. However, simple counts of animals can be misleading this problem exacerbated in seals (pinnipeds) where individuals spend much time foraging away from colonies. We analyzed a 13-year-series census data Galapagos sea lions (Zalophus wollebaeki) the colony Caamano, an islet center archipelago large proportion was individually marked. Based on regular resighting efforts during cold, reproductive (cold-R; August to January) warm, non-reproductive (warm-nR; February May) season, we document changes numbers different sex age classes. During cold-R season number adults increased as newborn pups increased. Numbers were larger morning evening than around mid-day not significantly influenced by tide levels. More frequented warm-nR season. Raw suggested decline over 13 years, but Lincoln-Petersen (LP-) estimates (assuming closed population) did support that conclusion. LP correlated, demonstrating overwhelming importance variability attendance patterns individuals. The probability observing given adult varied between 16% (mean season) 23% (warm-nR may less independent 2 4 year olds. Dependent juveniles (up about years) are observed more frequently ashore (35% 50% seasons). Simple underestimate real population size factor 4–6 lead erroneous conclusions trends size.