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

Abstract

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.

Males’ calls carry information about individual identity and morphological characteristics of the caller in burrowing petrels

“…the resonant frequencies (Titze 1994, Taylor andReby 2010). Although this theory is valid in mammals, the relationships between frequencies and body size remains unclear in birds (Galeotti et al 1997, Mager et al 2007, Favaro et al 2017, Kriesell et al 2018 but see Patel et al 2010).…”

“…A well-known example is the fundamental frequency (or pitch) which negatively correlates with body size (e.g. Galeotti et al 1997, Mager et al 2007, Favaro et al 2017, Kriesell et al 2018. In many species, larger males have a higher breeding success because body mass is an indicator of physical strength and/or foraging success (Chastel et al 1995, Salton et al 2015 and females rely on fundamental frequency as a sexual signal (review in Cardoso 2012).…”

A field study of auditory sensitivity of the Atlantic puffin, Fratercula arctica

“…Species such as Adélie (Pygoscelis adeliae), king (Aptenodytes patagonicus) and gentoo penguins (P. papua) use their calls to facilitate mate and chick identification as parents or partners return to the noisy colonies. Individuality can be conveyed through certain parameters including call duration, amplitude modulation rates, spectrum bandwidth and distribution of energy among harmonics (Humphries et al, 2016;Jouventin et al, 1999;Kriesell et al, 2018;Ligout et al, 2016;Mathevon, 1997). In Wilson's storm-petrels (Oceanites oceanicus) and several auk species, chicks in poorer condition emit higher frequency calls, and these higher pitched calls also result in the chick receiving increased care, including larger meals (Gladbach et al, 2009;Klenova, 2015).…”

Vocal tract anatomy of king penguins: morphological traits of two-voiced sound production

“…The display calls of king penguins Aptenodytes patagonicus have been shown to be emitted during mate choice [39] and sex-differences in the fundamental frequency of the calls and the syllable pattern have been identified [40]. Furthermore, playback experiments have shown that the king penguin call is vital for individual recognition [41,42].…”