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

Abstract

29African Penguin Spheniscus demersus numbers have declined steadily over three 30 generations, resulting in a loss of nearly 60% since of 1989. The breeding population reached 31 an historic low of ~20,850 pairs in 2019. We use count data and JARA, a generalized Bayesian 32 state-space tool for estimating extinction risk estimates under IUCN Red List Criterion A, to 33 assess the current status of the African penguin population at a global scale. We then 34 deconstruct the overall decline in time and space to identify the regional populations most in 35 need of urgent conservation action. The population in South Africa has declined at a faster 36 annual rate (−5.1%, highest posterior density interval, HPDI: −9.1 to −1.1%) than the 37 population in Namibia, which has remained relatively stable since 1989 (−0.1%, HPDI: −3.7 38 to +3.6%). And within South Africa, the most rapid rate of change has been seen in the 39 Western Cape colonies to the north of Cape Town, which have declined at nearly 10% per 40 annum over the last 20 years. The large declines in the Western Cape (particularly at Dassen 41 Island and Dyer Island), coupled with slower declines at colonies further east have resulted in 42 the Eastern Cape colonies containing ~50% of the South African penguin population in 2019, 43 as compared to ~27% in 1989. These changes have been coincident with changes in the 44 2 abundance and availability of the main prey of the African penguin and eastward 45 displacements of a number of other marine resources in South Africa. Our results highlight the 46 dynamic nature of the decline of the African penguin population in both space and time, and 47 identify clear regions in which urgent conservation action is required.

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

“…The data underlying this article are available in the Dryad digital repository: https://doi.org/10.5061/dryad.vx0k6 djp7 (Sherley, Crawford, et al, 2020).…”

Intercolony variation in reproductive skipping in the African penguin

“…Since 1989, the African penguin population has declined by almost 65% (Sherley et al, 2020). While historically driven by egg collection and guano scraping (Crawford et al, 2018;Frost et al, 1976), current declines are predominantly attributed to reduced prey availability (Crawford et al, 2011;Sherley et al, 2020). Shifting geographic distributions of sardine (Sardinops sagax) and anchovy (Engraulis encrasicolus), the main prey of African penguins, apparently exacerbated by competition with fisheries, has been linked to both reduced survival (Robinson et al, 2015;Sherley, Abadi, et al, 2014) and lower breeding success (Crawford, Barham, et al, 2006;Sherley et al, 2013Sherley et al, , 2021.…”

“…The African penguin is endemic to the Benguela upwelling system, where they currently breed at 28 localities in Namibia, South Africa's Western Cape, and South Africa's Eastern Cape (Sherley et al, 2020). Breeding is based around social monogamy and strong breeding site fidelity, with >90% of birds historically expected to retain the same mate in the absence of partner mortality (Crawford et al, 1995).…”

Reproductive skipping behaviour in the African penguin (Spheniscus demersus)

“…The African penguin is endemic to South Africa and Namibia, feeding on sardine (Sardinops sagax ) and anchovy (Engraulis encrasicolus ) stocks in the Benguela upwelling system (Wilson 1985). Since 1989, the African penguin population has declined by almost 65%, with the fastest declines occurring at colonies in South Africa's Western Cape (Sherley et al 2020). While historically driven by egg collection and guano scraping (Frost et al 1976;Crawfordet al 2018), current declines are predominantly attributed to reduced prey availability (Crawford et al 2011;Sherley et al 2020).…”

“…Since 1989, the African penguin population has declined by almost 65%, with the fastest declines occurring at colonies in South Africa's Western Cape (Sherley et al 2020). While historically driven by egg collection and guano scraping (Frost et al 1976;Crawfordet al 2018), current declines are predominantly attributed to reduced prey availability (Crawford et al 2011;Sherley et al 2020). Shifting geographic distributions of sardine and anchovy, the main prey of African penguins, apparently exacerbated by competition with fisheries, have been linked to both reduced survival (Sherleyet al 2014, Robinson et al 2015 and lower breeding success (Crawford et al 2006;Sherley et al 2013Sherley et al , 2021.…”