Sex-specific foraging behaviour and a field sexing technique for Endangered African penguins

Pichegru, Lorien; Cook, Timothée R.; Handley, Jonathan; Voogt, Nina; Watermeyer, Jessica; Nupen, Lisa J.; McQuaid, Christopher D.

doi:10.3354/esr00477

Cited by 39 publications

(57 citation statements)

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“…Female African Penguins show higher foraging effort than do males and the overlap between male and female foraging habitat is lower in years of low food availability (Pichegru et al. ). Unlike at Punta Tombo, juvenile and adult survival have shown temporal declines at African Penguin colonies (Sherley et al.…”

Section: Discussionmentioning

confidence: 99%

Sex‐biased survival contributes to population decline in a long‐lived seabird, the Magellanic Penguin

Gownaris

Boersma

2019

Ecological Applications

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We developed a Hidden Markov mark–recapture model (R package marked) to examine sex‐specific demography in Magellanic Penguins (Spheniscus magellanicus). Our model was based on 33 yr of resightings at Punta Tombo, Argentina, where we banded ~44,000 chicks from 1983 to 2010. Because we sexed only 57% of individuals over their lifetime, we treated sex as an uncertain state in our model. Our goals were to provide insight into the population dynamics of this declining colony, to inform conservation of this species, and to highlight the importance of considering sex‐specific vital rates in demographic seabird studies. Like many other seabirds, Magellanic Penguins are long‐lived, serially monogamous, and exhibit obligate biparental care. We found that the non‐breeding‐season survival of females was lower than that of males and that the magnitude of this bias was highest for juveniles. Biases in survival accumulated as cohorts aged, leading to increasingly skewed sex ratios. The survival bias was greatest in years when overall survival was low, that is, females fared disproportionality worse when conditions were unfavorable. Our model‐estimated survival patterns are consistent with independent data on carcasses from the species’ non‐breeding grounds, showing that mortality is higher for juveniles than for adults and higher for females than for males. Juveniles may be less efficient foragers than adults are and, because of their smaller size, females may show less resilience to food scarcity than males. We used perturbation analysis of a population matrix model to determine the impact of sex‐biased survival on adult sex ratio and population growth rate at Punta Tombo. We found that adult sex ratio and population growth rate have the greatest proportional response, that is, elasticity, to female pre‐breeder and adult survival. Sex bias in juvenile survival (i.e., lower survival of females) made the greatest contribution to population declines from 1990 to 2009. Because starvation is a leading cause of morality in juveniles and adults, precautionary fisheries and spatial management in the region could help to slow population decline. Our data add to growing evidence that knowledge of sex‐specific demography and sex ratios are necessary for accurate assessment of seabird population trends.

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Section: Discussionmentioning

confidence: 99%

Sex‐biased survival contributes to population decline in a long‐lived seabird, the Magellanic Penguin

Gownaris

Boersma

2019

Ecological Applications

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“…Pichegru et al . () derived a DFA containing only beak measurements and determined the sex in African Penguins Spheniscus demersus with over 90% confidence. In the comprehensive study by Polito et al .…”

Section: Discussionmentioning

confidence: 99%

“…Studies on sex determination by morphological measurements in other penguin species used beak and feet length measurements (Pichegru et al . , Lee et al . ) but, recently, differences in flipper length between female and male King Penguins (Viblanc et al .…”

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confidence: 99%

Sex identification in King Penguins Aptenodytes patagonicus through morphological and acoustic cues

Kriesell

Aubin

Planas‐Bielsa

et al. 2018

Ibis

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In the context of sexual selection, animals have developed a variety of cues conveying information about the sex of an individual to conspecifics. In many colonial seabird species, where females and males are monomorphic and do not show obvious differences in external morphology, acoustic cues are an important signal for individual and sex recognition. Here, we study the vocal and morphological sex dimorphism in the King Penguin Aptenodytes patagonicus, a colonial, monomorphic seabird for which our knowledge about the role of vocalizations and morphology in mate choice is very limited. Data were collected at Possession Island, Crozet Archipelago, in a breeding colony consisting of about 16 000 breeding pairs. Using measurements of six morphological features and analysing acoustic parameters of call recordings of adult individuals, we show that King Penguins can be sexed based on a single morphological measurement of the beak with an accuracy of 79%. We found a sex‐specific syntax in adult King Penguin calls that provided a 100% accurate method to distinguish between the sexes in our study population. To confirm the method at the species level, we analysed calls recorded from King Penguin adults in Kerguelen Island, 1300 km away from our study population and found the same accuracy of the sex‐specific syntax. This sex‐specific syllable arrangement is rare in non‐passerines and is a first step in understanding the mate choice process in this species. Furthermore, it offers a cost‐effective, non‐invasive technique for researchers to sex King Penguins in the field.

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“…Female African Penguin Spheniscus demersus foraging effort has been shown to be higher than that of males when rearing chicks (Pichegru et al . ), indicating that a sex‐specific parental investment might exist in this species. African Penguins provide bi‐parental care to a clutch of two eggs laid 3 days apart (Hockey et al .…”

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confidence: 88%

“…), and males are slightly larger than females (5–10% in body size, Pichegru et al . ), although overlap exists between the sexes in mass and morphometric measurements, such as bill size and flipper length (Cooper , Pichegru et al . ).…”

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confidence: 99%

Sex allocation and sex‐specific parental investment in an endangered seabird

Spelt

Pichegru

2017

Ibis

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Biased offspring sex ratio is relatively rare in birds and sex allocation can vary with environmental conditions, with the larger and more costly sex, which can be either the male or female depending on species, favoured during high food availability. Sex‐specific parental investment may lead to biased mortality and, coupled with unequal production of one sex, may result in biased adult sex ratio, with potential grave consequences on population stability. The African Penguin Spheniscus demersus, endemic to southern Africa, is an endangered monogamous seabird with bi‐parental care. Female adult African Penguins are smaller, have a higher foraging effort when breeding and higher mortality compared with adult males. In 2015, a year in which environmental conditions were favourable for breeding, African Penguin chick production on Bird Island, Algoa Bay, South Africa, was skewed towards males (1.5 males to 1 female). Males also had higher growth rates and fledging mass than females, with potentially higher post‐fledging survival. Female, but not male, parents had higher foraging effort and lower body condition with increasing number of male chicks in their brood, thereby revealing flexibility in their parental strategy, but also the costs of their investment in their current brood. The combination of male‐biased chick production and higher female mortality, possibly at the juvenile stage as a result of lower parental investment in female chicks, and/or at the adult stage as a result of higher parental investment, may contribute to a biased adult sex ratio (ASR) in this species. While further research during years of contrasting food availability is needed to confirm this trend, populations with male‐skewed ASRs have higher extinction risks and conservation strategies aiming to benefit female African Penguin might need to be developed.

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Sex-specific foraging behaviour and a field sexing technique for Endangered African penguins

Cited by 39 publications

References 50 publications

Sex‐biased survival contributes to population decline in a long‐lived seabird, the Magellanic Penguin

Sex‐biased survival contributes to population decline in a long‐lived seabird, the Magellanic Penguin

Sex identification in King Penguins Aptenodytes patagonicus through morphological and acoustic cues

Sex allocation and sex‐specific parental investment in an endangered seabird

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