Date Published: November 7, 2018
Publisher: Public Library of Science
Author(s): Romy Klusener, Renata Hurtado, Nola J. Parsons, Ralph Eric Thijl Vanstreels, Nicola Stander, Stephen van der Spuy, Katrin Ludynia, Ulrike Gertrud Munderloh.
The African penguin (Spheniscus demersus) population is estimated at 25,000 breeding pairs, approximately 5% of that at the start of the 20th century, and the species is currently classified as Endangered. In the last two decades, the hand-rearing of penguin chicks that were abandoned by their parents due to oil spills or other circumstances has become a valuable conservation tool to limit mortality and to bolster the population at specific colonies. We summarize and evaluate the techniques employed by the Southern African Foundation for the Conservation of Coastal Birds (SANCCOB) to incubate and hand-rear African penguin eggs and chicks. From 2012 to 2016, a total of 694 eggs and 2819 chicks were received by SANCCOB’s Chick Rearing Unit. It was estimated that 13% of the eggs were infertile, and 81% of the fertile eggs hatched successfully. The overall release rate for chicks was 77%, with a higher release rate for chicks that were pre-emptively removed (93%) followed by chicks that had been abandoned by their parents (78%), chicks admitted due to avian pox lesions (61%), chicks that hatched from artificially-incubated eggs (57%), and chicks admitted due to injuries or deformities (25%). Rescuing and hand-rearing eggs and chicks has been a successful strategy for African penguins, and might be also applicable for the conservation of other threatened seabird species whose population are critically low or during natural or anthropogenic events that could have disastrous population impacts (e.g. oil spills, disease outbreaks, catastrophic weather events, strong El Niño years, etc.).
The African penguin (Spheniscus demersus) is endemic to the greater Agulhas-Benguela upwelling ecosystem of southern Africa. The present population is approximately 5% of that at the start of the 20th century, when it was estimated at over 1.45 million adults . Historically, African penguin eggs were harvested in large numbers, causing large-scale population declines . By the late 1970s the population had declined to 220,000 adults, due to unsustainable egg harvesting and oil pollution [1,3]. By the 1990s only 179,000 adults remained due to massive disturbance and habitat alteration caused by the collection of guano , and the species was classified as Near Threatened . The species’ population continued declining in the 21st century due to changes in the abundance, distribution and quality of food, and between 2001 and 2009 the number of African penguins further declined by 60%, reaching a global population of 26,000 breeding pairs (c. 83,200 individuals) and was reclassified as Vulnerable [4,5]. The last assessment on the global population of African penguins was conducted in 2015 and estimated the global population at 25,000 breeding pairs (c. 80,000 individuals), and the species was classified as Endangered in 2010 .
Incubation and hand-rearing procedures are conceptually outlined in Fig 1. Chicks were classified into six stages of development based on their size, plumage and other external characteristics (Fig 2) based on Barham et al.  and Sherley et al. . The rehabilitation protocols were based on incubation and hand-rearing protocols developed for other penguin species [12–14], and were empirically adapted based on the breeding biology of the African penguin [3,15–17] and on the continuous re-evaluation of the rehabilitation results. A detailed description of the African penguin incubation and hand-rearing procedures is provided in S1 File.
A total of 694 eggs were admitted between 2012 and 2016, and 489 of those eggs (70%) hatched successfully. The number of eggs admitted was highest from February to May (Fig 3A) and the hatching rate was highest for eggs admitted in fall (April to June) (Fig 3B). Of the eggs that did not hatch successfully and were necropsied, 110 eggs (57%) contained a dead embryo, 83 eggs (43%) did not contain a visible embryo and were presumed to be infertile; no necropsy was conducted for 12 eggs. The stage of embryonic development upon death was determined for 72 embryonated eggs: 22 eggs (31%) were in an early stage, 12 eggs (17%) were in an intermediate stage, 26 eggs (36%) were in a late stage, and 12 chicks (17%) died during hatching. If it is presumed that 43% of the eggs that were not necropsied were infertile, it may be estimated that 87% of the eggs were fertile (i.e. 606 fertile eggs, 88 infertile eggs), and therefore 81% of the fertile eggs hatched successfully.
Rehabilitation is valuable strategy for the mitigation of human impacts on the African penguin population, as exemplified by the large-scale rescue and rehabilitation operations conducted in response to the Apollo Sea (1992) and Treasure (2000) oil spills [1,9,22–24]. In recent years, SANCCOB’s rehabilitation efforts have been redirected to address an emerging challenge, with the recurring abandonment of eggs and chicks and the resulting poor breeding success. The African Penguin Chick Bolstering Project was established in 2006 in an attempt to mitigate the impacts of the abandonment of eggs and chicks, aiming to slow the rate of population decline [7,11].