Female Calls Research Articles

Gender Matters in Hospitality (invited paper for ‘luminaries’ special issue of International Journal of Hospitality Management)

This article is a review paper, which examines the place of gender in hospitality research and education and discusses the significance of hospitality for women's employment and entrepreneurship opportunities. The paper’s main purpose, however, is to speculate on the future of hospitality gender research and women’s employment prospects in the industry. It suggests that, despite the emergence of gender perspectives in hospitality research and the recent rise of popular feminism in response to high-profile sexual harassment cases and a well-publicised gender pay gap, gender still does not occupy mainstream territory in the field. The paper stresses the continued missed opportunities of neglecting female talent and calls on female and male leaders to shape a gender-just future in hospitality study and practice by mentoring and holding hierarchies to account. The paper identifies AI and robotics and sexual exploitation and harassment as two areas in which hospitality gender scholars could lead scholarship and policy debates on gendered human experiences.

Different Audio-lures Lead to Different Sex-biases in Capture of Northern Saw-whet Owls (Aegolius acadicus)

Northern Saw-whet Owls (Aegolius acadicus) are banded across the United States, yet neither migration nor dispersal of Northern Saw-whet Owls are fully understood. In spring of 2007 and 2008, the banding station at Whitefish Point Bird Observatory in Michigan's Upper Peninsula began broadcasting male and female (respectively) audio lures at dedicated net arrays to complement the passive mist netting performed since 1994. We analyzed data from spring owl captures (1994–2016) that used either male “advertising call” audio lures, female “tssst” audio lures, or no audio lures. From the analysis of 6659 owls captured during that period, we found that (1) there was a substantial female-bias in the owls caught at the passive and male audio lure nets, (2) a more extreme female-bias in the owls caught at the male audio-lure nets than the passive nets, and (3) a nearly equal proportion of male and female owls caught at the female audio-lure nets. These results corroborate a model of differential migration, in which females compose a larger portion of migrating Northern Saw-whet Owls than males. We also found that audio lures that use female calls can increase relative capture rates of male Northern Saw-whet Owls during spring migration.

Male and female signaling behavior varies seasonally during territorial interactions in a tropical songbird

In many tropical birds, both sexes use conspicuous vocal signals during territorial interactions. Although a growing number of studies examine male and female signals in the context of coordinated vocal duets, the use of vocal signals by both sexes in non-duetting species is poorly documented, even though these species are more numerous than duetting species. Furthermore, few studies of tropical non-duetting species test for seasonal variation in signaling behavior. We studied season-specific and sex-specific variation in signaling behavior of a tropical resident songbird, the Rufous-capped Warbler (Basileuterus rufifrons), by conducting a playback experiment where we simulated conspecific territorial intruders producing three types of vocalizations (male songs, female calls, or a “pair” with simultaneous male songs and female calls) and a heterospecific control. We repeated playback during the pre-breeding and breeding seasons. Response intensity to playback varied with season and sex of the focal birds. During the pre-breeding season, both sexes showed strong physical approach responses and vocal responses to all conspecific intrusions, especially paired intrusions. During the breeding season, males responded strongly to all conspecific treatments, whereas females showed little response. Although females primarily used calls in response to conspecific playback, many females also sang, especially during the non-breeding season. Our results therefore suggest that both male and female signals are used for shared territory defense, but that the contributions of each sex to territory defense vary seasonally. Our results also contribute to our understanding of the evolution of combined male and female signaling during territory defense. In resident tropical animals, both males and females often use conspicuous signals during territorial interactions with conspecifics. Seasonal and sex-specific variation in vocal behavior of tropical resident birds during these territorial interactions has received little research attention. We conducted a playback experiment to investigate season- and sex-specific variation in signaling behavior of tropical Rufous-capped Warblers (B. rufifrons). In the pre-breeding season, both sexes responded strongly to all conspecific intrusions, especially paired intrusions, by approaching the playback speakers and vocalizing. In the breeding season, males actively defended the territory alone whereas females rarely responded. Our results suggest that both sexes of Rufous-capped Warbler use vocal signals for shared territory defense, although the contributions of each sex to territory defense differ seasonally.

Acoustic fine structure may encode biologically relevant information for zebra finches

The ability to discriminate changes in the fine structure of complex sounds is well developed in birds. However, the precise limit of this discrimination ability and how it is used in the context of natural communication remains unclear. Here we describe natural variability in acoustic fine structure of male and female zebra finch calls. Results from psychoacoustic experiments demonstrate that zebra finches are able to discriminate extremely small differences in fine structure, which are on the order of the variation in acoustic fine structure that is present in their vocal signals. Results from signal analysis methods also suggest that acoustic fine structure may carry information that distinguishes between biologically relevant categories including sex, call type and individual identity. Combined, our results are consistent with the hypothesis that zebra finches can encode biologically relevant information within the fine structure of their calls. This study provides a foundation for our understanding of how acoustic fine structure may be involved in animal communication.

Stress-induced flexibility and individuality in female and male zebra finch distance calls

Vocal recognition is central to the coordination and organization of behavior in pair-bonding species such as zebra finches. Zebra finches’ vocalizations are individualized and support acoustic discrimination processes. Physiological states - such as the ones involved in emotional stress - can modify vocal production and consequently the structure of vocalizations. These modifications might signal the state of the caller but also impair individual recognition processes. This may represent a signaling trade-off, especially in contexts where both pieces of information can be critically important, for example when mates use calls to reunite after social isolation. Here we study the impact of a stress on the individual vocal signature in both female and male zebra finch distance calls.We built a manually curated database of distance calls of several individuals (both females and males) recorded in control and stress conditions. The stress was induced either by social isolation of the bird or using exogenous corticosterone. We developed a machine learning approach to assess the impact of stress on the individual characterization of calls.We show that while calls’ spectral structure is significantly modified by stress, it still allows for the correct classification of calls to the caller. Moreover, we also show that the stress-induced modification of calls’ structure is not a 'general feature signal' that can be detected as a 'stress' signal regardless of identity. Thus, female and male zebra finch calls’ structure show stress-induced flexibility that stays within the range of individual vocal signatures.

Application of a semi-automated vocal fingerprinting approach to monitor Bornean gibbon females in an experimentally fragmented landscape in Sabah, Malaysia

Vocal individuality has been documented in a variety of mammalian species and it has been proposed that this individuality can be used as a vocal fingerprint to monitor individuals. Here we provide and test a classification method using Mel-frequency cepstral coefficients (MFCCs) to extract features from Bornean gibbon female calls. Our method is semi-automated as it requires manual pre-processing to identify and extract calls from the original recordings. We compared two methods of MFCC feature extraction: (1) averaging across all time windows and (2) creating a standardized number of time windows for each call. We analysed 376 calls from 33 gibbon females and, using linear discriminant analysis, found that we were able to improve female identification accuracy from 95.7% with spectrogram features to 98.4% accuracy when averaging MFCCs across time windows, and 98.9% accuracy when using a standardized number of windows. We divided our data randomly into training and test data-sets, and tested the accuracy of support vector machine (SVM) predictions over 100 iterations. We found that we could predict female identity in the test data-set with a 98.8% accuracy. Using SVM on our entire data-set, we were able to predict female identity with 99.5% accuracy (validated by leave-one-out cross-validation). Lastly, we used the method presented here to classify four females recorded during three or more recording seasons using SVM with limited success. We provide evidence that MFCC feature extraction is effective for distinguishing between female Bornean gibbons, and make suggestions for future vocal fingerprinting applications.

The flight ecology of ants (Hymenoptera: Formicidae)

Most of the world’s ant species rely on flight for reproduction and dispersal, during a solitary phase in which colony fitness depends only on the survival of individual queens. Flight-related selection shapes ant physiology, such that queens and males fly for short durations but carry heavy loads due to the nutrient demands of mating and colony founding. Ants vary by four orders of magnitude in flight distance, with larger ants or those with lighter abdomens flying farther than smaller or heavier ones. Flight tradeoffs explain much variation in ant life history, including the temporal segregation of flight and egg production, the continuum of ant mating systems from male aggregation to female calling syndromes, and the evolution of alternate colony founding strategies. Flight performance also constrains range expansions or shifts in response to invasions or climate change. Flying queens and males act as dispersal vectors for pathogenic or symbiotic organisms, and are eaten in large numbers by aerial insectivores. By entering aerial food webs, flying ants help mediate the flow of energy and materials through ecosystems. They are also model systems for addressing several questions, including nutrient allocation tradeoffs and the evolution of reproductive polymorphisms.

Male white-handed gibbons flexibly time duet contributions

Vocal duetting occurs when two individuals produce repeated, stereotyped vocalizations, often with alternating contributions. It evolved independently in many pair living taxa. Among hominoids, only hylobatids duet, but little is known about how mated pairs coordinate singing and if individuals adjust their song to spectral and temporal aspects of another’s song. If they do, this would demonstrate vocal flexibility not yet well documented in apes. To test this hypothesis, we analyzed duets of wild white-handed gibbons (Hylobates lar), quantifying female notes and the timing of male notes relative to them. We measured changes in female notes that preceded her great call phrase and that she initiated only after her mate had stopped singing. We predicted males would suspend their own song during a female’s great call phrase in anticipation of her climax, and thus should interrupt abnormal female calls, because these typically fail to climax. We compared (1) interrupted great call phrases females aborted, (2) interrupted phrases that were completed, and (3) uninterrupted, completed phrases. We found that abnormal great call phrases were interrupted by males, likely because the male anticipated that the phrase would be abandoned before reaching its climax. Although female call phrases varied in length, we also found that males replied in close synchrony with their ending. Subtle spectral and temporal variations in song influenced the timing of a mate’s singing and thus the structure and delivery of duets. Although ape vocal behavior is thought to be largely innate, our findings show unexpected flexibility in song expression. Vocal duets by mated pairs occur in many animal species but only in one ape family, the hylobatids (gibbons and siamang). Although gibbon duetting has been described for many species, little is still known about how partners coordinate singing. We show that individuals rapidly and flexibly adjust their song in direct response to changes in a mate’s singing. This coordinated adjustment to a mate’s ongoing singing likely allows for precise turn-taking during duets, which centers around the female great call phrase, and especially its climax notes. Although vocalizations of nonhuman apes are thought to be largely developmentally fixed, this plasticity suggests that turn-taking duets may be an exception. Turn-taking duetting requires gibbons to adjust their singing to that of the partner, perhaps similar to vocal exchange behaviors that contributed to increased flexibility in the precursors of speech.

Comparing functions of copulation calls in wild olive baboons, Papio anubis, using multimodel inference

Female copulation calls are species specific, distinct vocal signals sometimes given during or shortly after mating. Despite being common in primates and despite much empirical work, their function remains largely unclear for most species. Here, we used an information-theoretic approach to examine simultaneously three main competing hypotheses for the evolution of copulation calls. Two of the three hypotheses predict that female copulation calls function to incite competition between males, either directly (the male–male competition hypothesis) or indirectly (the sperm competition hypothesis), while the third predicts that females use calls to choose mating partners (the female choice hypothesis). We collected data on copulations of wild female olive baboons in Kibale National Park, Uganda, to compare the relative support for these hypotheses by modelling whether or not females produced copulation calls after mounts. Our analytical approach enabled us to objectively rank models corresponding to the three hypotheses according to how well our data fitted the models. Our data favoured the sperm competition hypothesis over the female choice hypothesis although much variation in calling remained unexplained. The male–male competition hypothesis seems unlikely given our data. We also discuss the possibility that copulation calls have no function, functions not included in our analysis, or that they are multifunctional, a reflection of the species' social evolution history. • Several hypotheses of female copulation calls exist with no clear consensus. • We used multimodel inference to test the main hypotheses in olive baboons. • We found strongest support for the sperm competition hypothesis. • We discuss alternative hypotheses and advantages of multimodel inference.

Coalition formation, mate selection and pairing behaviour of the Crested Francolin

Transect field observations were conducted on the behaviour of Crested Francolin Dendroperdix sephaena to describe male coalitions in the Borakalalo National Park, North West province, South Africa during May, August, October and December 2008, and again in July 2009. Crested Francolin form male coalitions following the breeding season in May. Young males leave their natal coveys and join old males in these coalitions, which are not based on kinship and consist of up to nine members. These coalitions are joined by a young female from June to October, followed by the breeding season when pairs replace coalitions. The coalition is a prelude to successful mating. The single female calls in the coalition, which triggers a cacophony, and her presence often erupts in physical conflicts between males. This cacophony is interpreted as signal jamming where males prevent one another from forming a duet with the female, clearly showing competition between them for winning over the female for mating. A well-synchronised duet forms the basis of pair formation. Old females are not particularly selected for pairing. The coalition is also a surrogate covey for young males because it optimises predator surveillance. The pair bond also optimises predator surveillance for each other throughout the year.

Rivalry between Stink Bug Females in a Vibrational Communication Network

In the field, male pheromone attracts stink bugs to meet on the same plant and triggers females to call a male by the emission of the calling song. As first among Pentatomidae we describe female rivalry in Chinavia impicticornis, C. ubica and Euschistus heros. Rivalry starts in C. impicticornis by synchronized exchange of the first type of the female calling song pulse trains and proceeds by one of them either to change pulse trains from the first to the second type or to produce readily repeated single pulses. Both reactions either inhibit calling of the rival female or trigger her to respond by alternation with the second type of the calling song pulse trains. Female rivalry in C. ubica differs by the emission of the rival song that replaces alternation with the second type of the calling song typical for C. impicticornis. E. heros females synchronize pulses of the calling song duets and induce emission of the female rival song by one of them that partly inhibits singing of the other. These competitive interactions in Chinavia species reduce the proportion of couples when compared with single couples on a plant. Contrary to both Chinavia species, E. heros female rivalry does not inhibit male response, male signals overlap female emissions and create complex vibrations with modified amplitude modulation pattern caused by interference.

Bionomics of Comadia redtenbacheri (Hammerschmidt, 1847) (Lepidoptera: Cossidae)

Boring insects feed on the internal tissues of their hosts, and their activity is detected only after a severe damage to the host has occurred; therefore, studying their biology in the wild is difficult. The objective of the study was to complement knowledge about the biology, ecology and taxonomic position of Comadia redtenbacheri (Hammerschmidt, 1847), an agave borer with a long lifecycle. Laboratory observations were made on life stages obtained from larvae collected in Hidalgo, Mexico, which were induced to pupate in tubes with vermiculite and soil. Emerged adults were placed in cloth bags where they mated and laid eggs. Larvae that emerged from these eggs were raised on an artificial diet. Field observations were made in some localities of the State of Mexico; for this, external leaves and rhizomes of Agave plants were examined to look for eggs and larvae. Eggs and larvae were found in Agave salmiana Otto ex Salm-Dyck and Agave applanata Lem. ex Jacobi. Eggs are brown; they are found mainly at the base of external leaves. Neonate larvae bore a hole in the chorion and feed on it for a few days; they are gregarious and migrate towards the rhizome as they mature; last instar larvae are aposematic and release a volatile odoriferous secretion; their development is not uniform and can last more than a year. Pupation takes place in a silken cocoon under the soil. Adults are nocturnal; female calling starts one hour after the start of the scotophase, and can last until 5:30 am; oviposition happens a few hours after mating. The parasitoids Lisonnota fascipennis Townes, 1978 (Hymenoptera: Ichneumonidae), and Acantholespesia texana (Aldrich & Webber, 1924) (Diptera: Tachinidae) and fungal and bacterial pathogens are commonly found in larvae. Predators of larvae and adults include ants, rodents and birds.

Female cuckoo calls misdirect host defences towards the wrong enemy.

Prey are sensitive to even subtle cues of predation risk, which provides the evolutionary potential for parasites to exploit host risk perception. Brood parasitic common cuckoos (Cuculus canorus) lay their eggs in the nests of host species and their secretive laying behaviour enables them to evade host defences. Therefore, it seems paradoxical that female cuckoos often give a conspicuous 'chuckle' call after parasitizing a host's clutch. Here, we show that this hawk-like chuckle call increases the success of parasitism by diverting host parents' attention away from the clutch and towards their own safety. In our field experiments, reed warbler (Acrocephalus scirpaceus) hosts paid no more attention to the 'cuck-oo' call of the male common cuckoo than the call of a harmless dove. However, the chuckle call of the female cuckoo had the same effect as the call of a predatory hawk in distracting the warblers' attention and reducing rejection of a foreign egg. Our results show that the female cuckoo enhances her success by manipulating a fundamental trade-off in host defences between clutch and self-protection.

Sublethal Effects of Neonicotinoid Insecticide on Calling Behavior and Pheromone Production of Tortricid Moths.

In moths, sexual behavior combines female sex pheromone production and calling behavior. The normal functioning of these periodic events requires an intact nervous system. Neurotoxic insecticide residues in the agroecosystem could impact the normal functioning of pheromone communication through alteration of the nervous system. In this study we assess whether sublethal concentrations of the neonicotinoid insecticide thiacloprid, that competitively modulates nicotinic acetylcholine receptors at the dendrite, affect pheromone production and calling behavior in adults of three economically important tortricid moth pests; Cydia pomonella (L.), Grapholita molesta (Busck), and Lobesia botrana (Denis & Schiffermüller). Thiacloprid significantly reduced the amount of calling in C. pomonella females at LC0.001 (a lethal concentration that kills only 1 in 105 individuals), and altered its calling period at LC1, and in both cases the effect was dose-dependent. In the other two species the effect was similar but started at higher LCs, and the effect was relatively small in L. botrana. Pheromone production was altered only in C. pomonella, with a reduction of the major compound, codlemone, and one minor component, starting at LC10. Since sex pheromones and neonicotinoids are used together in the management of these three species, our results could have implications regarding the interaction between these two pest control methods.

The acoustic repertoire of the Atlantic Forest Rocket Frog and its consequences for taxonomy and conservation (Allobates, Aromobatidae).

The use of acoustic signals is a common characteristic of most anuran species to mediate intraspecific communication. Besides many social purposes, one of the main functions of these signals is species recognition. For this reason, this phenotypic trait is normally applied to taxonomy or to construct evolutionary relationship hypotheses. Here the acoustic repertoire of five populations of the genus Allobates from the Brazilian Atlantic Forest are presented for the first time, on a vulnerable to extinction Neotropical taxon. The description of males’ advertisement and aggressive calls and a female call emitted in a courtship context are presented. In addition, the advertisement calls of individuals from distinct geographical regions were compared. Differences in frequency range and note duration may imply in taxonomic rearrangements of these populations, once considered distinct species, and more recently, proposed as a single species, Allobates olfersioides. Calls of the male from the state of Rio de Janeiro do not overlap spectrally with calls of males from northern populations, while the shorter notes emitted by males from Alagoas also distinguishes this population from the remaining southern populations. Therefore, it is likely that at least two of the junior synonyms should be revalidated. Similarities among male advertisement and female calls are generally reported in other anuran species; these calls may have evolved from a preexisting vocalization common to both sexes. Male aggressive calls were different from both the male advertisement and female calls, since it was composed by a longer and multi-pulsed note. Aggressive and advertisement calls generally have similar dominant frequencies, but they have temporal distinctions. Such patterns were corroborated with the Atlantic Forest Rocket Frogs. These findings may support future research addressing the taxonomy of the group, behavioral evolution, and amphibian conservation.

Acoustic Analysis of Novel Female Calls in Japanese Pond Frogs, Pelophylax nigromaculatus and Pelophylax porosus brevipodus

Abstract: In most frogs, males emit calls in the reproductive seasons, whereas females usually do not emit calls. Females of only several frog species have been known to vocalize. I here report female vocalization in two ranid species, Pelophylax nigromaculatus and P. porosus brevipodus in their overlapping reproductive season. Females of these species called in both intraspecific and interspecific interactions. There were no clear differences in acoustic characteristics of female calls between the two species or between interspecific and intraspecific interactions. Based on the situations in which females called, it is implied that functions of the female calls of P. nigromaculatus and P. p. brevipodus are quite different from those of female calls in frogs hitherto reported.

¿Por qué jugar? Sport socialization among Hispanic/Latina female NCAA division I student-athletes

Representation of Hispanics/Latinas in intercollegiate athletics is lacking. During the 2014-2015 National Collegiate Athletic Association (NCAA) athletic season, only 2.2 percent of all female Division I student-athlete’s identified as Hispanic or Latina (NCAA, 2015). This low percentage of Hispanic/Latina female participants calls into question how these young women become involved in athletics and sustain their involvement within sport. While previous research has examined the socialization processes of youth athletes and parents of youth athlete participants, there is little research aimed at examining these processes for elite-level athlete participants (Dorsch, Smith, & McDonough, 2015; Greendorfer, Blinde, & Pellegrini, 1986;). Thus, the aim of this current study was to examine the potential factors that may have contributed to consistent sport participation for an elite group of Hispanic/Latina female athletes throughout their youth and collegiate careers. Participants for this study identified as current NCAA Division I Hispanic/Latina female student-athletes. Results showed that family, specifically parents and siblings, contributed to socializing Hispanic/Latina athletes into sport, while family and coaches contributed to the persistence of their athletic endeavors. Findings also show a sense of cultural indifference, youth coaches who invested in the participants long-term, and a significant involvement of the patriarch of the family in their athletic success.

Sexual pair-formation in a cicada mediated by acoustic behaviour of females and positive phonotaxis of males

The functions of female song found in a few cicadas have rarely been studied. In the cicada Subpsaltria yangi we investigated the acoustic behaviour and signal structure of songs produced by females, the phonotaxis of males, and mate choice, as well as the selective pressure imposed on this species by predators. Pair-formation in S. yangi occurs when males signal, females respond, then males move to signaling females, which is opposite to that in most other cicadas where females move to calling males. Females only mate once and are sexually unreceptive after copulation. Most males mate once, but ~25% mate multiply. Females display little direct evidence of mate preference or choice of males, and all mate encounters led to a successful mating. Only males are attacked by a robber fly, Philonicus albiceps, while flying to females. This imposes strong selection on males – only males who can evade predators mate. Males are also attracted to human simulations of female calls. This behaviour exposes the mating system to impacts from anthropogenic noise systems which could disrupt mating activity of this species. Our results improve the understanding of mate choice/competition in cicadas, and are valuable for future studies of the evolution of sound communication in the Cicadoidea.

Lack of alarm calls in a gregarious bird: models and videos of predators prompt alarm responses but no alarm calls by zebra finches

Many vertebrates use vocalizations to communicate about the presence of predators, and some encode information about predator type or behavior. A fast-approaching predator typically elicits a “flee alarm call,” prompting others to escape to safety. In a field experiment, we presented gliding models of a predatory bird to several species representing four families of passerine, including our model species, the zebra finch (Taeniopygia guttata). All families presented with the glider gave a distinct call on at least one occasion, apart from the zebra finch, for which no specific alarm call was recorded. Following on from this unexpected result, we conducted an experiment in which we exposed captive zebra finches to video of a looming raptor. Results of the captive study showed that birds responded to the looming raptor with escape behavior and responded to less threatening stimuli with orienting or startle behavior. Despite this anti-predator response, birds did not give any distinct alarm call, and the distance calls of both males and females did not differ in structure or rate of delivery after exposure to a stimulus. Zebra finches are one of the most studied birds in the world, are gregarious, and have a rich vocal repertoire, yet their alarm communication has not been investigated experimentally. Our results are consistent with the hypothesis that zebra finches lack a flee alarm call and appear not to signal about immediate danger through a change in calling rate. Many animals emit alarm calls when faced with a threatening event in order to communicate with nearby group members. Threatening events can be simulated with models or by presenting a video of a looming stimulus on a screen. In separate studies, we presented gliding models and computer animations of a hawk to zebra finches, a bird species used in studies around the world, in order to test if they gave alarm calls to warn others of approaching danger. Although birds fled in response to the simulated predators, they did not emit a distinct alarm call. The birds also did not change their rate of calling or the acoustic structure of their distance calls. Surprisingly for a social and highly vocal species, the birds appear to lack alarm calls warning flockmates of immediate danger.

Subharmonics increase the auditory impact of female koala rejection calls

AbstractAlthough non‐linear phenomena are common in human and non‐human animal vocalisations, their functional relevance remains poorly understood. One theory posits that non‐linear phenomena generate unpredictability in vocalisations, which increases the auditory impact of vocal signals, and makes animals less likely to habituate to call repetition. Female koalas (Phascolarctos cinereus) produce vocal signals when they reject male copulation attempts that contain relatively high levels of non‐linear phenomena, and thus may function as attention grabbing vocal signals during the breeding season. To test this hypothesis, we used playback experiments: firstly, to determine whether female rejection calls induce heightened behavioural responses in free‐ranging male koalas during the breeding season, and secondly, to examine how the relative amount of non‐linear phenomena in rejection calls influences male behavioural response. The results show that male koalas look for longer towards speakers broadcasting playback sequences of male bellows followed by a series of female rejection calls than those broadcasting only male bellows. In addition, female rejection call sequences with more subharmonics, higher harmonics‐to‐noise ratios, and less biphonation produced the greatest male looking responses. Our findings support the hypothesis that female koala rejection calls function to grab male attention during the breeding season, and indicate that subharmonics are the main acoustic feature that increases the auditory impact of these vocal signals.