Pygoscelis Adeliae) at Cape Crozier, Ross Island, Antarctica PARKER M
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Antarctic Science page 1 of 9 (2021) © Antarctic Science Ltd 2021 doi:10.1017/S0954102021000158 Breeding behaviour of colour-aberrant Adélie penguins (Pygoscelis adeliae) at Cape Crozier, Ross Island, Antarctica PARKER M. LEVINSON 1, ANNIE E. SCHMIDT 1, VIRGINIA MORANDINI2, MEGAN ELROD1, DENNIS JONGSOMJIT1 and GRANT BALLARD1 1Point Blue Conservation Science, 3820 Cypress Dr #11, Petaluma, CA 94954, USA 2Oregon State University, 104 Nash Hall, Corvallis, OR 97331, USA [email protected] Abstract: Plumage colour variation occurs widely among bird species and is often associated with individual fitness. More specifically, colouration can affect thermoregulatory ability, mate selection and conspicuousness during foraging. Colour aberrations can be caused by genetic mutations, dietary imbalances, environmental conditions or disease and are rare. Plumage variations have previously been noted in Adélie penguins, although without any follow-up to measure implications for behaviour or fitness. To assess how this low-frequency condition affects breeding in Adélie penguins, we monitored the breeding of several colour-aberrant Adélie penguins during the 2019–2020 nesting season at the large Cape Crozier, Ross Island colony (> 300,000 pairs). In total, we found 12 individuals with unusual plumage for a frequency of 1:50,000 breeding penguins. There were seven dark brown Adélie penguins, three progressive greying Adélie penguins, one dilute Adélie penguin and one brown Adélie penguin, of which five were female, three male and four of unknown sex. Six colour aberrants initiated breeding with a normal-coloured mate, and five raised at least one chick to crèche. The likelihood of breeding and breeding success of colour aberrants were similar to those of normal-coloured Adélie penguins, suggesting that colour aberrations do not negatively affect breeding. Received 20 July 2020, accepted 16 March 2021 Key words: dark brown, dilute, ino, leucistic, progressive greying Introduction colour may still be used to select mates. Both male and female king penguins (Aptenodytes patagonicus, Miller) Unusual colour morphs, or colour aberrations, exist across have yellow and orange pigmentation, the intensity of many taxa and species. They can arise from a variety which signals their overall health and is used for mate of causes, including dietary imbalances, environmental selection (Nolan et al. 2006, Jouventin et al. 2007). In conditions, disease or genetic mutations (van Grouw one study, females selected males with larger coloured 2013). The Wright and Haldane models predict that the patches, and when a male's pigmentation was more deleterious a genetic mutation, the more recessive it experimentally covered up, they had a much harder time tends to be (Huber et al. 2018). However, while recessive pairing (Jouventin et al. 2007, Dobson et al. 2011). mutations lie dormant in a given population, the variation However, males appeared to be less selective when they encode may hold important value in different choosing mates and paid less attention to the female's conditions, such as after a sudden environmental change. manipulated patch (Jouventin et al. 2007). A classic example is the peppered moth in Britain during Colour variation may also be linked to differences in the Industrial Revolution. The white-bodied morph of the individual behaviour. For example, dark and light species was predominant, using its colouration as morphs of the Pacific reef heron (Egretta sacra, Gmelin) camouflage from predators; however, as pollution levels employ different foraging tactics, with light morphs increased and tree trunks darkened, the once-rare utilizing flight in their pursuit of prey, whereas dark melanistic individuals rapidly proliferated until they morphs rely more on land-based attacks. They can even became the common colour morph. When air pollution forage in different locations. On Mangaia in the decreased, the white-bodied morph once again became Southern Cook Islands, light morphs favoured foraging more abundant (Maderson 1975,Cooket al. 2012). on the windward side of the island and dark morphs on Variation in colour can also signal individual condition the leeward side (Rohwer 1990). Additionally, there is and breeding ability (MacDougall & Montgomerie 2003, evidence of colour expression being related to Reudink et al. 2009). Even in monomorphic species, thermoregulation on a genetic level. In a single common 1 Downloaded from https://www.cambridge.org/core. UC Davis, on 18 May 2021 at 20:24:19, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0954102021000158 2 PARKER M. LEVINSON et al. murre (Uria aalge, Pontopippidan) population, the bridled Antarctica and are an important indicator of climate morph showed greater survival during colder years, while change (Ainley 2002, Lynch & LaRue 2014). As such, the unbridled morph did better in warmer years (Reiertsen they are potentially useful for understanding the frequency et al. 2012). Because the difference in colouration is of colour variation, the effects that it has on mate selection slight between these two morphs, this indicates that and the possible implications in a warming climate. Adélie colour expression could be correlated with specific penguin plumage is sexually monomorphic, with both thermoregulatory genes (https://www.biorxiv.org/content/ sexes exhibiting countershading (black-pigmented feathers 10.1101/507384v1). As climate change continues to alter on the dorsal region, neck, head and upper side of the the environment, different colour variations or morphs may flipper and white feathers on the ventral sides of their body have an advantage, like with the peppered moth during the and flippers). Chicks have dark or light grey down until Industrial Revolution. Darker morphs with more melanin they fledge ∼46–55 days after hatching (Fig. 1)(Ainley may become more advantageous because of the increased et al. 1983). Any variation from this colouration is protection against ultraviolet radiation (Roulin 2014). On considered a colour aberration, and we focus on the other hand, it may become increasingly difficult for aberrations that affect the entire body as opposed to ones darker-pigmented birds to thermoregulate, leading to affecting just a small area, most probably due to some overheating (Margalida et al. 2008). form of trauma (van Grouw 2006, 2013). Because Adélie The little blue penguin (Eudyptula minor, Forster) is populations are well studied, they are among the penguins the only penguin species with an accepted colour with the most aberrations reported in the scientific morph, the white-flippered penguin, though its status as literature. In fact, the first record of a colour aberrant is an a morph vs a subspecies (Eudyptula minor albosignata, 'isabelline' or brown (sex-linked) Adélie painted by Finsch) is under debate (Banks et al. 2002). E.A. Wilson from R.F. Scott's early polar expeditions Nevertheless, colour variations have been recorded in at (Wilson 1907). Since then, at least five additional varieties least 13 of 17 penguin species (combining the southern have been recorded (leucism, melanism, brown, dilute and rockhopper (Eudyptes chrysocome, Forster) and northern ino: Falla 1937 as cited in Finger et al. 2017,Araya& rockhopper (Eudyptes moseleyi, Matthews & Iredale) Arrieta 1971, Forrest & Naveen 2000, Juáres et al. 2011, because data are not detailed enough post-speciation; Finger et al. 2018). However, nomenclature for the Stevens 2000,Everitt&Miskelly2003,Fingeret al. 2017, aberrations is diverse. For this paper, we follow van 2018, https://www.youtube.com/watch?v=NuIczQ4W7oU). Grouw's (2013, 2018)definitions and descriptions. Continuing to understand and monitor the occurrence of these aberrations is important as species adapt to environmental changes (Le Corre 1999). Adélie penguins (Pygoscelis adeliae, Hombron & Jacquinot) are an abundant species that breed only in Fig. 2. Location of Adélie penguin colour aberrants in blue stars overlaid on yellow sub-colony boundaries with inset of Cape Crozier location (noted by red star) on Ross Island, Antarctica. Note higher concentration of blue stars (i.e. colour aberrants) towards the middle of West Crozier. Satellite image from WorldView-3, 20 November 2014 (copyright 2014 DigitalGlobe, NextView License). Ross Island image acquired by moderate-resolution imaging spectroradiometer (MODIS) on board Aqua satellite on 29 November 2011 (courtesy of Fig. 1. Two normal-coloured Adélie penguins with the Rapid Response Imagery from Land, Atmosphere Near traditional black and white countershading standing next to Real-Time Capability for Earth Observing System operated by two normal-coloured (although muddy), downy Adélie chicks. NASA/GSFC/Earth Science Data and Information System Photograph credit: Parker M. Levinson. with funding provided by NASA/HQ). Downloaded from https://www.cambridge.org/core. UC Davis, on 18 May 2021 at 20:24:19, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0954102021000158 BREEDING BEHAVIOUR OF COLOUR‐ABERRANT ADÉLIE PENGUINS 3 Todate, little has been done to understand the frequency numbered plastic tag attached to an 8 inch stake into the of various colour mutations or how they might affect ground ∼6 inches from the territory edge. Territories breeding behaviour. In this paper, we aim to document were then monitored weekly for the rest of the season the variety, frequency and sex