Interspecific differences in male vocalizations of three sympatric fur seals (Arctocephalus spp.) (original) (raw)
Related papers
Bioacoustics, 2005
Australian fur seals Arctocephalus pusillus doriferus are colonial breeding animals forming dense social groups during the breeding season. During this time, males establish and defend territories through physical conflicts, stereotyped posturing and vocalisations. While vocalisations are suggested to play an important role in male recognition systems, it has received little attention. Recordings of nine adult male Australian fur seals were made during the 2000 and 2001 breeding seasons at Kanowna Island (39° 10′S, 146° 18′ E), Bass Strait, Australia. The in-air bark vocalisations of territory-holding males were used to characterise the Bark Call and to determine whether males produce individually distinct calls, which could be used as a basis for vocal recognition. Seventeen frequency and temporal variables were measured from a total of 162 barks from nine individual males. The Bark Series was more reliably classified (83%) to the correct caller compared to the Bark Unit. This was assigned with less certainty (68%), although the classification was still relatively high. Findings from this study indicate that there is sufficient stereotypy within individual calls, and sufficient variation between them, to enable vocal recognition in male Australian fur seals.
Vocal traits of hybrid fur seals: intermediate to their parental species
Animal Behaviour, 2001
Vocal communication is important for species recognition in colonial breeding species such as fur seals, especially where closely related species that can hybridize breed sympatrically. This is the first study to describe the calls of hybrid fur seals. We investigated whether these vocalizations are intermediate to those of their parental species (Antarctic, Arctocephalus gazella, subantarctic, A. tropicalis, and New Zealand, A. forsteri) and discuss the evolutionary implications of hybrids having intermediate vocal traits. Hybrid males' bark calls were intermediate between two distinct groups formed by A. tropicalis and A. gazella/A. forsteri. Patterns of intermediate call characteristics were also discernible for pup attraction calls (given by females) but not for full threat calls (given by males), nor female attraction calls (given by pups); however, for all call types hybrid calls were distinct from those of their parental species. The pattern of hybrid calls being intermediate is consistent with the expectation that call traits are genetically inherited.
Australian Journal of Zoology, 2009
In polygynous mammals, the status of many males does not allow them to have a high social rank and theory predicts selection for alternative mating tactics. Alternative tactics were suggested to explain discrepancies between mating and paternity successes in several pinniped species. However, information on alternative tactics in fur seals is limited. Here, we focus on the polygynous New Zealand fur seal, Arctocephalus forsteri, predicting that competition for females is likely to cause a diversification of male mating tactics and that non-territorial tactics can yield reproductive success. We describe the behaviour of 38 males in a medium to large colony. Paternity success was assessed using CERVUS and PASOS, from a pool of 82 pups sampled at the study site and at neighbouring breeding areas. To see whether size is correlated with mating tactic, the length of 17 males was estimated using photogrammetry. Cluster analysis identified three male behavioural profiles: one corresponding to large territorial males and two illustrating alternative tactics employed by smaller non-territorial males. Of the 13 pups born at the study site that were assigned a father, eight were sired by three territorial males and five were sired by non-territorial males. Our study highlights that holding a territory is not a necessary condition for reproductive success in all otariids.
Behavioral Ecology and Sociobiology, 2021
The ability to recognize the identity of conspecifics is a key component for survival of many animal species and is fundamental to social interactions such as parental care, intra-sexual competition or mate recognition. In group-living species, the simultaneous coexistence of many individuals increases the number of interactions and reinforces the need for individual recognition. Acoustic signals are widely used by birds and mammals to communicate and to convey information about identity, but their use in very dense colonies becomes challenging due to the high level of background noise and the high risk of confusion among individuals. The Cape fur seal (CFS) is the most colonial pinniped species and one of the most colonial mammals in the world, with colonies of up to 210,000 individuals during the breeding season. Here, we investigated the individual stereotypy in vocalizations produced by pups, females and male CFS using Random Forests and index of vocal stereotypy (IVS). We thus compared IVS values of CFS to other pinniped species. Within CFS we identified individuality in all call types but the degree of individual stereotypy varies in regards to their social function: affiliative calls produced in a mother-pup reunion context and territorial calls produced by mature bulls holding harem were more individualized than vocalizations involved in agonistic interactions. Our inter-species comparisons among pinnipeds showed that CFS affiliative and territorial calls displayed higher degrees of individuality compared to other species with similar or lower ecological constraints (colony density and social structure).
Molecular Ecology, 2001
Microsatellites were used to conduct an analysis of paternity of Antarctic fur seals ( Arctocephalus gazella ) from Bird Island, South Georgia. At most, only 28% of pups at our study site could be assigned a father, even though the majority (~90%) of candidate males within this colony were sampled. The behavioural and genetic evidence from this study suggests that a number of alternative mating strategies may exist within this fur seal population. Holding a land-based territory conferred an advantage to male reproductive success. However, this advantage was much smaller than expected from behavioural observations. At least 70% of fur seal pups born at our study site in a given year are not fathered by males who held a territory or were observed copulating with females in the previous year, implying that there exists a pool of males that seldom venture ashore at this site. To explain this discrepancy we suggest that female choice is an integral component of the Antarctic fur seal mating system and that aquatic mating may play a much larger role in the Antarctic fur seal than previously thought.
Characterization of Australian fur seal vocalizations during the breeding season
Marine mammal …, 2008
The vocal repertoire, structure, and behavioral context of airborne vocalizations produced by Australian fur seals (Arctocephalus pusillus doriferus) are described using recordings made at a breeding colony on Kanowna Island, Bass Strait, Australia. The study identified six different call types: three produced by males (bark, guttural threat, and submissive call); five produced by females (bark, guttural threat, submissive call, growl, and pup attraction call) and the female attraction call produced by pups and yearlings. Vocalizations were compared according to age and sex classes. The overall structure and function of the pup attraction and female attraction call produced by females, yearlings, and pups, was similar. However, while similar in their overall appearance, certain call types have a lower fundamental frequency when compared with other fur seals. In addition, the male bark call alters in rate of production according to the context used, where calls are slower when males are stationary and advertising their territorial status and faster when males are involved in confrontations with other males or actively herding females. Further research is required to investigate changes in environmental conditions and 913 914 MARINE MAMMAL SCIENCE, VOL. 24, NO. 4, 2008 their effects on shaping the call structure and communication in Australian fur seals.
The Journal of the Acoustical Society of America, 2011
Whether an animal truly recognizes an individual or a simple rule-based category (e.g. neighbor or offspring) has important behavioral and evolutionary implications such as the accuracy of social reciprocity. Many tests of individual recognition have focused on neighboring territorial males ("dear enemy" or "neighbour-stranger" recognition). Unfortunately the static territorial context of these tests, mostly with male songbirds, opens them to the criticism of being merely associative habituation. More dynamic mating assemblages, such as leks where vocally advertising animals encounter numerous others, are a potentially rich and largely untested alternative. The female defense polygyny practiced by male northern elephant seals during terrestrial breeding is such a dynamic system. To examine whether elephant seals were recognizing individuals or dominance categories we conducted a total of 53 playback experiments to 18 males at Año Nuevo State Reserve. Each playback was a series of threat calls assigned to four dominance conditions relative to the subject. Dominance was based on the outcomes of interactions among contesting male dyads. Responses were measured using three assays in situ and from video records of each experiment. Results indicate that males do recognize familiar individuals although responses are primarily based on relative dominance rank.
Marine Mammal Science, 2003
Like most otariids species, the Subantarctic fur seal breeds on land in large, dense colonies. Pups are confronted by the long and repetitive absences of their mother throughout lactation. At each mother's return, pups have to find her among several hundreds of congeners. This recognition process mainly relies on acoustic signals. We performed an acoustic analysis on 125 calls from 20 females recorded during the 1999-2000 breeding season on Amsterdam Island (Indian Ocean). Ten variables were measured in both temporal and frequency domains. To find the acoustic parameters supporting individual signature, we assessed the differences between individuals using Kruskall-Wallis univariate analysis of variance. For each variable, we also calculated the potential of individuality coding (PIC) as the ratio between the between-individual coefficient of variation and the mean value of the within-individual coefficients of variation. We found that the frequency spectrum, the characteristics of the frequency modulation of the initial and middle part of the call and the call duration exhibit an important individual stereotypy (PIC values ranging between 1.5 and 3), whereas features relative to amplitude and the frequency modulation 161 162 MARINE MAMMAL SCIENCE, VOL. 19, NO. 1, 2003 of the final part of the call are weakly individualized (PIC values between 1 and 1.2).
Relationships between underwater vocalizations and mating systems in phocid seals
Aquatic Mammals, 2003
In this paper, we considered the number and diversity of underwater vocalizations given by aquaticbreeding phocids, and two species that copulate both in the water and on ice, in relation to what is known or hypothesized about their mating systems. Underwater recordings made throughout the year by both bearded ( Erignathus barbatus ) and Weddell (Leptonychotes weddellii ) seals indicated that most of the vocalizations could be attributed to males and were given almost exclusively during the breeding season. Less extensive studies of other species indicated the same pattern. Thus, for this study, we considered only underwater vocalizations known, or suspected, to be given by adult males during intra-specie c agonistic behaviour, defence of territories or access to females, or attraction of females. A one-way ANOVA and linear regression indicated a signie cant relationship between the numbers of underwater vocalizations given by individual species and their mating systems. A Pearson’ s correlation analysis discerned the following: the mating system and the number of vocalizations were positively correlated; female gregariousness was positively correlated with the number of underwater vocalizations and geographic variation in vocalizations, but there was no correlation with the duration of lactation. The degree of predation was negatively correlated with the number of vocalizations, geographic variation in vocalizations, and the number of days of lactation. A principal component analysis showed that 66.1% of the variation in this data set was explained by Factor 1, a suite of variables that included mating system, number of underwater vocalizations, intensity of predation, female gregariousness, and geographic variation in vocalizations. The number of days of lactation explained an additional 19.5% of the variability. These results suggest that additional selection pressures, more specie c to the ecological circumstances of individual species, also ine uence the size of the underwater repertoire. The development of a diverse underwater repertoire with geographic variations was consistently associated with the development of population genetic structure and geographic e delity. Within each category of social system, the species with the greatest number of underwater vocalizations consistently occurred at higher densities during the breeding season than did the species with the lowest vocal diversity. The role of predators on the evolution of social systems is not well known, but could be signie cant for some species. Characteristics of the underwater vocalizations of walruses during the breeding season were found to share similar characteristics to phocids occurring at similar densities in similar habitats, suggesting that the most important selection factors ine uenced both phocids and odobenids similarly. On the basis of the available information from better-studied species, some testable hypotheses are proposed for further investigations of spotted ( Phoca largha ), Ross (Ommatophoca rossii ), Hawaiian monk (Monachus schauinslandi), and ribbon ( Phoca fasciata) seals.