Data from: The conservation status and population decline of the African penguin deconstructed in space and time

Understanding changes in abundance is crucial for conservation, but
population growth rates often vary over space and time. We use 40 years of
count data (1979–2019) and Bayesian state-space models to assess the
African penguin Spheniscus demersus population under IUCN Red List
Criterion A. We deconstruct the overall decline in time and space to
identify where urgent conservation action is needed. The global African
penguin population met the threshold for Endangered with a high
probability (97%), having declined by almost 65% since 1989. An historical
low of ~17,700 pairs bred in 2019. Annual changes were faster in the South
African population (−4.2%, highest posterior density interval, HPDI: −7.8
to −0.6%) than the Namibian one (−0.3%, HPDI: −3.3 to +2.6%), and since
1999 were almost −10% at South African colonies north of Cape Town. Over
the 40-year period, the Eastern Cape colonies went from holding ~25% of
the total penguin population to ~40% as numbers decreased more rapidly
elsewhere. These changes coincided with an altered abundance and
availability of the main prey of African penguins. Our results underline
the dynamic nature of population declines in space as well as time and
highlight which penguin colonies require urgent conservation attention.