Abstract
In long-lived species, reproductive skipping is a common strategy
whereby sexually mature animals skip a breeding season, potentially
reducing population growth. This may be an adaptive decision to protect
survival, or a non-adaptive decision driven by individual-specific
constraints. Understanding the presence and drivers of this behaviour is
key to effective population management, yet in many species such as the
endangered African penguin (Spheniscus demersus ), these factors
remain unknown. This study uses multistate mark-recapture methods to
estimate African penguin survival and breeding probabilities at two
colonies between 2013 and 2020. Overall, survival was higher at Stony
Point (0.82) than Robben Island (0.77). Inter-colony differences were
linked to food availability; under decreasing sardine (Sardinops
sagax ) abundance, survival decreased at Robben Island and increased at
Stony Point. Additionally, reproductive skipping was evident across both
colonies; at Robben Island ~22% of breeding individuals
skipped reproduction each year, versus ~10% at Stony
Point. Penguins skipping reproduction had a lower probability of future
breeding than breeding individuals; this lack of adaptive benefit
suggests reproductive skipping is driven by individual-specific
constraints. Lower survival and breeding propensity at Robben Island
places this colony in greater need of conservation action. However,
further research on the drivers of inter-colony differences is needed.
Keywords: Benguela ecosystem, breeding propensity,
mark-recapture, population dynamics, seabirds, survival.