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The outcome of male–male encounters affects subsequent sound production during courtship in the cichlid fish Oreochromis mossambicus
Abstract
Social status in lek-breeding species is highly correlated with mating success. Reproductive failure of subordinates may be caused either by direct aggression by dominant males or by induced physiological changes. We hypothesized that recent social status (winning or losing an encounter with another male) affects the production of courtship sounds in male Mozambique tilapia, Oreochromis mossambicus, in the absence of dominant males. We staged dyadic encounters between males and subsequently allowed full access to a female to either the winner or the loser (one fish per dyad). We minimized possible effects of social experience by isolating the subject males before the experiments. All males courted the females but winners produced more courtship sounds than losers and showed significantly shorter courtship latencies and longer courtship durations. The sounds of winners had longer pulse durations and lower peak frequencies. Male size and condition factor, fighting latency and duration, and number of escalated agonistic acts were not correlated with number of sounds or any of the courtship parameters measured. Differences between winners and losers in courtship were probably related to transient physiological changes induced by the encounter outcome, such as changes in levels of circulating monoamines, cortisol and androgens, which can modulate courtship behaviour including sound production. We suggest that in nature the outcome of recent social interactions between males may affect the production of courtship sounds and courtship behaviour in general from the early stages of hierarchy formation.
... Species divergence in closely related sympatric cichlids, especially in the Great Lakes of Africa has been hypothesized to have occurred, in part, due to assortative mating. Cichlid mate choice studies confirm that assortative mating does occur in several species in the field and in captivity (Blais et al. 2009;Egger et al. 2008;Knight and Turner 2004; (1) Myrberg et al. (1965) Amorim et al. (2004Amorim et al. ( , 2008, Simoes et al. (2006); Simoes et al. (2008a, b), Bertucci et al. (2010), Van Staaden and Smith (2011), Danley et al. (2012), Bertucci et al. (2012a, b), Bertucci et al. (2013) Copadichromis conophorus Mchenga conophoros (Stauffer, LoVullo and McKaye, 1993) (2) Lobel (1998Lobel ( , 2001 Melanochromis auratus (Boulenger, 1897) (3) Smith (2007), Smith and Van Staaden (2009), Van Staaden and Smith (2011) Neochromis omnicaeruleus (Seehausen and Bouton, 1998) (1) Verzijden et al. (2010) Neolamprologus pulcher (Trewavas and Poll, 1952) (2) Spinks et al. (2017); Pisanski et al. (2015) Tilapia mossambicus Oreochromis mossambicus (Peters, 1852) (9) Rodman (1966), Konstantinova et al. (1979), Amorim et al. (2003), Amorim and Almada (2005), McPherson (2012), Pujiyati et al. (2016), Lanzing (1974), Marshall (1971Marshall ( , 1972 ...
... However, in one other cichlid, Pundamilia nyererei, sounds produced in different contexts were the same (Verzijden et al. 2010). Acoustic contests in a laboratory setting between males did not show a correlation between male size, increased fighting intensity, and call number (Amorim and Almada 2005). Studies of O. niloticus demonstrated that in male-male contests winners were quick to court, courtship duration was extended and their calls were greater in number with longer pulse durations and lower peak frequencies than previous contest losers (Amorim and Almada 2005), traits that correlate with increased fitness in other vertebrate species. ...
... Acoustic contests in a laboratory setting between males did not show a correlation between male size, increased fighting intensity, and call number (Amorim and Almada 2005). Studies of O. niloticus demonstrated that in male-male contests winners were quick to court, courtship duration was extended and their calls were greater in number with longer pulse durations and lower peak frequencies than previous contest losers (Amorim and Almada 2005), traits that correlate with increased fitness in other vertebrate species. Dyadic contests elicited agonistic sound production in P. nyererei (Verzijden et al. 2010). ...
Bioacoustics has become a key feature of cichlid behavioral studies over the last 20 years, due in large part to new technologies and software. The hypothesis that some cichlid species produce species-specific sounds is gaining support with data from several studies. Sounds are specific to behavioral context for many species. Cichlids are advanced teleost fishes possessing a complex pharyngeal jaw. This morphological feature has been proposed as the key functional innovation responsible for the evolutionary success and explosive adaptive radiation of the group. This evolutionary success has been mostly attributed to their expanded adaptability to process a wide variety of food types due to the capability of thoroughly grinding food in the pharyngeal apparatus, an ability that most other fishes lack. The evidence regarding the role of the pharyngeal jaw complex in sound production is evaluated, and suggests that this same morphology enables cichlids to produce a complex and varied acoustic repertoire. Although, the sonic mechanism may be more complex morphologically than just the pharyngeals clacking. More studies are needed to carefully document the sounds correlated to specific behaviors of cichlids and to statistically examine the species specificity of sympatric species sounds. Future research is needed that experimentally tests the response of female fish to acoustic playback combined with visual and chemical cues in order to determine how critical sound communication is to the sympatric evolution of cichlid species.
... A variety of African cichlids are known to produce acoustic signals in the context of courtship, including both riverine (Myrberg et al., 1965), and rift lake species (Amorim et al., 2004;Lobel, 1998Lobel, , 2001. Sound production is influenced by behavioral and social lability (Amorim and Almada, 2005). Although there is little experimental evidence for the influence of sound on mating decisions of females (but see Verzijden et al., 2010), a range of behavioral (Fay and Popper, 1975), psychophysical (Tavolga, 1974;Yan and Popper, 1992) and noninvasive physiological experiments (Ladich and Wysocki, 2003;Ripley et al., 2002;Smith et al., 2004) support a general correlation between hearing sensitivity and acoustic signals in cichlids. ...
... In the case of cichlids, we advocate a return to the motivational approach, harnessing the power of automated stimulus generating and tracking techniques, to overcome the limitations inherent in the traditional choice paradigm. Such an approach is appropriate and effective because we know cichlids have complex brains generating complex cognition (Huber et al., 1997;van Staaden et al., 1995), whereby both learning (Verzijden and ten and experiential effects (Amorim and Almada, 2005;Kotschal and Taborsky, 2010) lead to variability. In this way, the field of cichlid behavioral research might advance by returning to its classic ethological roots. ...
... Balshine-Earn and Lotem, 1998; 2 Rosenthal, 2000; 3 Saverino and Gerlai, 2008; 4 Baldauf et al., 2009; 5 Elliot, 2006; 6 Dunlop et al., 2006; 7 Yue et al., 2004; 8 Paul et al., 2005; 9 Braithwaite and Boulcott, 2007; 10 Braithwaite, 2006; 11 Pierotti et al., 2008; 12 Amorim and Almada, 2005. ...
The active transmission of information from sender to receiver is a fundamental component of communication, and is therefore a primary facet in evolutionary models of sexual selection. Research in several systems has underlined the importance of multiple sensory modalities in courtship signals. However, we still tend to think of individuals as having a relatively static signal in consecutive communicative events. While this may be true for certain traits such as body size or coloration, behaviorally modulated signals can quickly violate this assumption. In this work, we explore how intraspecific variation may be an important component of interspecific signal divergence using cichlid fishes from Lake Malawi. Behavioral analyses were made using six species of Malawian cichlids from two divergent genera. While interspecific differences were found between congeners based on species-level analyses of both acoustic and audiovisual signals, intraspecific variation was of a similar magnitude. Specifically, individual fishes were found to possess highly plastic signal repertoires. This finding was ubiquitous across all species and resulted in a great deal of overlap between heterospecific individuals, despite statistically distinct species means. These results demonstrate that some aspects of courtship in Malawian cichlids are more plastic than previously proposed, and that studies must account for signal variability within individuals. We propose here that behavioral variability in signaling is important in determining the communication landscape on which signals are perceived. We review potential complexity deriving from multimodal signaling, discuss the sources for such lability, and suggest ways in which this issue may be approached experimentally.
... (Tricas and Boyle, 2015). Many fish species produce multi-pulse sounds, commonly referred to as 'grunts', during reproductive and aggressive interactions (Lobel et al., 2010(Lobel et al., , 2021Amorim and Almada, 2005;Ladich and Myrberg, 2006;Myrberg and Lugli, 2006;McIver et al., 2014). Several damselfish species, including Stegastes partitus, make multi-pulse 'chirps' during reproductive interactions (Myrberg et al., 1978). ...
... Future studies would benefit from examining whether and how males might utilize acoustic communication and other signaling modalities (e.g. vision) to structure possible dominance hierarchies and determine nest ownership in a community (Conti et al., 2015;Chase et al., 2002;Amorim and Almada, 2005;Arnott and Elwood, 2009;Barata et al., 2007;Myrberg and Riggio, 1985). While the acoustic parameters we describe here can be correlated with features of agonistic displays, it is essential to first study what components, if any, of this information are perceived by members of a contest and any observers before characterizing a behavior as a signal or a cue, or to determine what features may or may not mediate mutual or selfassessment (Bradbury and Vehrencamp, 2011;Arnott and Elwood, 2009). ...
Acoustic behavior is widespread across vertebrates, including among fishes. We report robust acoustic displays during aggressive interactions for a laboratory colony of Danionella dracula, a miniature and transparent species of teleost fish closely related to zebrafish (Danio rerio), which are hypothesized to be sonic based on the presence of a hypertrophied muscle associated with the male swim bladder. Males produce bursts of pulsatile sounds and a distinct postural display–extension of a hypertrophied lower jaw, a morphological trait not present in other Danionella species—during aggressive, but not courtship interactions. Females show no evidence of sound production or jaw extension in such contexts. Novel pairs of size-matched or -mismatched males were combined in resident-intruder assays where sound production and jaw extension could be linked to individuals. In both dyad contexts, resident males produced significantly more sound pulses than intruders. During heightened sonic activity, the majority of highest sound producers also showed increased jaw extension. Residents extended their jaw more than intruders in size-matched, but not -mismatched contexts. Larger males in size-mismatched dyads produced more sounds and jaw extensions compared to their smaller counterparts, and sounds and jaw extensions increased with increasing absolute body size. These studies establish D. dracula as a sonic species that modulates putatively acoustic and postural displays during aggressive interactions based on residency and body size, providing a foundation for further investigating the role of multimodal displays in a new model clade for neurogenomic and neuroimaging studies of aggression, courtship, and other social interactions.
... (Tricas and Boyle, 2015). Many fish species produce multi-pulse sounds, commonly referred to as 'grunts', during reproductive and aggressive interactions (Lobel et al., 2010(Lobel et al., , 2021Amorim and Almada, 2005;Ladich and Myrberg, 2006;Myrberg and Lugli, 2006;McIver et al., 2014). Several damselfish species, including Stegastes partitus, make multi-pulse 'chirps' during reproductive interactions (Myrberg et al., 1978). ...
... Future studies would benefit from examining whether and how males might utilize acoustic communication and other signaling modalities (e.g. vision) to structure possible dominance hierarchies and determine nest ownership in a community (Conti et al., 2015;Chase et al., 2002;Amorim and Almada, 2005;Arnott and Elwood, 2009;Barata et al., 2007;Myrberg and Riggio, 1985). While the acoustic parameters we describe here can be correlated with features of agonistic displays, it is essential to first study what components, if any, of this information are perceived by members of a contest and any observers before characterizing a behavior as a signal or a cue, or to determine what features may or may not mediate mutual or selfassessment (Bradbury and Vehrencamp, 2011;Arnott and Elwood, 2009). ...
Individuals can reveal their relative competitive ability or mate quality through acoustic communication, varying signals in form and frequency to mediate adaptive interactions including competitive aggression. We report robust acoustic displays during aggressive interactions for a laboratory colony of Danionella dracula, a recently discovered miniature and transparent species of teleost fish closely related to zebrafish (Danio rerio). Males produce bursts of pulsatile, click-like sounds and a distinct postural display, extension of a hypertrophied lower jaw, during resident-intruder dyad interactions. Females lack a hypertrophied lower jaw and show no evidence of sound production or jaw extension under such conditions. Novel pairs of size-matched or mismatched males were combined in resident-intruder assays where sound production and jaw extension could be linked to individuals. Resident males produce significantly more sound pulses than intruders in both dyad contexts; larger males are consistently more sonic in size-mismatched pairs. For both conditions, males show a similar pattern of increased jaw extension that frequently coincided with acoustic displays during periods of heightened sonic activity. These studies firmly establish D. dracula as a sound-producing species that modulates both acoustic and postural displays during social interactions based on either residency or body size, thus providing a foundation for investigating the role of these displays in a new model clade for neurogenomic studies of aggression, courtship and other social interactions.
... Furthermore, social attributes could influence the vocal output. The males produce more courtship sounds than losers and show significantly shorter courtship latencies and longer courtship durations in the cichlid fish Oreochromis mossambicus (Amorim and Almada, 2005). Male Saccopteryx bilineata with a higher reproductive success trend to utter more territorial songs per day (Behr et al., 2006). ...
Animals living in a complex social environment emit diverse acoustic signals and thus serve as excellent subjects for understanding the evolution of acoustic communication. Previous studies have focused on the complexity of social calls in some group-living animals, yet the determinants of vocal complexity at the intraspecific level remain unclear. Here, we aimed to assess the influence of group composition on social call complexity in Himalayan leaf-nosed bats (Hipposideros armiger) in the non-breeding season. The bats divided into three groups with the same number of individuals but with different sex ratio compositions. We monitored social vocalizations for the all-male group, the all-female group, the mixed group, and also quantified vocal complexity for each group based on multiple acoustic metrics, including vocal repertoire, call sequences, the diversity index, and information capacity. The results showed that there were significant differences in the composition of call sequences among the three bat groups. The number of vocalizations was the highest in the mixed group, while the social call complexity was the highest in the all-male group, followed by the all-female group, and was the lowest in the mixed group. The results suggest that sex ratio potentially influence the vocal repertoire in Himalayan leaf-nosed bats. Our findings might provide a cue for vocalization research to investigate sex ratio in social groups as a potential driver for vocal complexity.
... My research on fish acoustic communication continued with a post-doctoral (post-doc) fellowship at ISPA-Instituto Universit ario (Portugal). During my first post-doc, I carried out research with the Mozambique tilapia, Oreochromis mossambicus (Amorim et al., 2003;Amorim and Almada, 2005) and stayed 6 months in Michael Fine's laboratory (Virginia Commonwealth University, USA) investigating the metabolic costs of sound production in the oyster toadfish, Opsanus tau (Amorim et al., 2002). While establishing my research in Portugal, and until now, Michael Fine has been my unseen mentor, providing valuable guidance, including numerous and extremely constructive reviews of my papers. ...
This paper outlines my research path over three decades while providing a review on the role of fish sounds in mate choice and reproduction. It also intends to provide advice to young scientists and point toward future avenues in this field of research. An overview of studies on different fish model species shows that male mating acoustic signals can inform females and male competitors about their size (dominant frequency, amplitude, and sound pulse rate modulation), body condition (calling activity and sound pulse rate), and readiness to mate (calling rate, number of pulses in a sound). At least in species with parental care, such as toadfishes, gobies, and pomacentrids, calling activity seems to be the main driver of reproductive success. Playback experiments ran on a restricted number of species consistently revealed that females prefer vocal to silent males and select for higher calling rates. This personal synthesis concludes with the suggestion to increase knowledge on fish mating signals, especially considering the emerging use of fish sounds to monitor aquatic environments due to increasing threats, like noise pollution.
... It can be argued that the social competence of asip1-Tg, defined as an individual's ability to use social information in order to optimise its social behaviour [39,40], allows such fish to conserve energy (by avoiding the fight for dominance) and evade aggression. In such a context, it is noteworthy that being subordinate may be costly for the individual, as it is associated with low activity levels, reduced growth, suppressed feeding, and reduced reproduction [41][42][43]. Nevertheless, such negative outcomes are unobserved in the asip1-Tg, as overexpression of Asip1 results in increased food intake and linear growth. ...
Simple Summary
Enhanced feeding can be associated with aggressive behaviour since food resources are the main reason for agonistic behaviour (any social behaviour related to fighting). The overexpression of the gene agouti-signalling protein (Asip1) in transgenic zebrafish (asip1-Tg) results in enhanced food intake and linear growth. Our next question was if asip1-Tg animals exhibit a dominant phenotype associated with the feeding-enhanced levels when compared to wild-type (WT) fish. To address this question, we quantified the aggressive behaviour by conducting dyadic fights with real opponents as well as by exposing the animals to their specular image using mirrors. The results indicate that asip1-Tg are less aggressive than WT zebrafish in both dyadic fights and mirror-stimulus tests. These findings provide direct evidence of the role of the melanocortin system in the regulation of fish behaviour. The subordinate personality observed in asip1-Tg suggests that this transgene would be non-threatening to native populations in the event of an escape from aquaculture facilities. These results provide a genetic modification strategy to enhance growth in fish through high feeding motivation without promoting aggressiveness. This suggests that inhibiting the melanocortin system could be a viable target for genetically engineered fish. It is worth noting that the regulatory approval for such genetically engineered fish would be subject to the guidelines and regulations of the U.S. Food and Drug Association.
Abstract
Feeding motivation plays a crucial role in food intake and growth. It closely depends on hunger and satiation, which are controlled by the melanocortin system. Overexpression of the inverse agonist agouti-signalling protein (ASIP) and agouti-related protein (AGRP) leads to enhanced food intake, linear growth, and weight. In zebrafish, overexpression of Agrp leads to the development of obesity, in contrast to the phenotype observed in transgenic zebrafish that overexpress asip1 under the control of a constitutive promoter (asip1-Tg). Previous studies have demonstrated that asip1-Tg zebrafish exhibit larger sizes but do not become obese. These fish display increased feeding motivation, resulting in a higher feeding rate, yet a higher food ration is not essential in order to grow larger than wild-type (WT) fish. This is most likely attributed to their improved intestinal permeability to amino acids and enhanced locomotor activity. A relationship between high feeding motivation and aggression has been previously reported in some other transgenic species showing enhanced growth. This study aims to elucidate whether the hunger observed in asip1-Tg is linked to aggressive behaviour. Dominance and aggressiveness were quantified using dyadic fights and mirror-stimulus tests, in addition to the analysis of basal cortisol levels. The results indicate that asip1-Tg are less aggressive than WT zebrafish in both dyadic fights and mirror-stimulus tests.
... In all experiments, the weight difference between members of the dyad was on average 7.3 ± 1.2 g (1.2 ± 0.2% of mean body weight). As recent social experience can affect subsequent behavior (Amorim and Almada, 2005;Oliveira et al., 2009) and as individuals were kept in groups in 500 l tanks, each member of the dyad was isolated in a 250 l aquarium (100 × 50 × 50 cm) for at least four days prior to being placed in experimental aquaria. These aquaria were in visual isolation from each other to prevent any interaction between individuals prior to the encounters. ...
In some fish species, sex is determined by the combination of genetic and environmental factors. In most species concerned, extreme temperatures during the sensitive period of sex differentiation drives masculinization, independently of the female sex chromosomes. In Nile tilapia (XY male heterogamety), XX juveniles exposed to high temperatures (>32 °C) can masculinize and become phenotypical males (neomales). Whether these neomales exhibit a different behavior than XY males remains however unclear. Sex reversal being naturally relevant, we investigated the agonistic behavior of neomales during dyadic fights and the preference of gravid females for one of the two male types. We quantified the behavior, size of the nest, hormone circulating levels (testosterone, 11-ketotestosterone and cortisol) and sound production of the two male types in both contexts. Independently of the individual they face, neomales seem to display more aggressive behaviors than XY males but often fail to become dominant. Agonistic interactions were mainly silent, suggesting that sounds are unnecessary for the establishment of social hierarchy. Although males and neomales produce different kinds of sounds when facing a gravid female, the female does not exhibit a preference. Overall, no differences were observed for hormone circulating concentrations between the two male types. We suggest that the sex chromosomes and/or the sex reversal procedure may have differently shaped the brain of neomales, resulting in differences in the expression of behavior.
... The female may consider the males' activity level in her choice and associate for more time with more active males. A similar positive association between dominance and courtship activity has been demonstrated in guppies (Poecilia reticulata Peters 1859;Kodric- Brown, 1996), Mozambique tilapia (Oreochromis mossambicus (Peters 1852);Amorim & Almada, 2005)) and minnows (Phoxinus phoxinus (L. 1758);Kekäläinen et al., 2010), and dominance is generally associated with male's courtship ability(Desjardins et al., 2012). ...
It is widely assumed that female preference and male competition operate simultaneously during sexual selection. Dominance is likely an honest indicator of male quality, and females can identify and choose the dominant male to reproduce with individuals with greater competitive abilities, thus improving the quality and competitiveness of their offspring. In this context, few studies have investigated female preference in relation to male fighting ability. The Mexican mojarra, Cichlasoma istlanum, is a cichlid species native to the Balsas River basin. It is territorial during reproduction and provides parental care. Males commonly engage in territorial defence, whereas females care directly for offspring. This study examined whether females prefer dominant males that exhibit more aggressive behaviour. The authors conducted experiments using groups of two males and one female to test competitive ability in males and female preference. They also quantified the time during which the female associated with the dominant male and the subordinate male after observing the outcome of a fight between the two males. They found that Mexican mojarra females preferred dominant males and that the time females spent associating with males was positively related with their aggressive behaviours during competition. These results indicate that dominant males were more attractive than subordinate males to female Mexican mojarra. The relationship between female preference and male dominance in the Mexican mojarra demonstrates the importance of male competitive ability for future parental care in reproduction.
... Within teleosts, different cichlid species produce sounds either in aggressive contexts (Amorim and Almada, 2005;Amorim et al., 2003Amorim et al., , 2004 or during courtship behaviour (Amorim et al., 2003(Amorim et al., , 2004. In Nile tilapia Oreochromis niloticus (Linnaeus 1758) sounds are produced during nest defence by territorial males and egg protection by females (Longrie et al., 2008(Longrie et al., , 2013. ...
We characterised, for the first-time, the sound production of black-chinned tilapia Sarotherodon melanotheron and show differences with that of Nile tilapia Oreochromis niloticus in a hybridization pairing context. Although both species were able to produce drum sounds, they showed different acoustic features. Drum sounds were produced in aggressive (chasing or lateral attack) and non-aggressive (courtship) contexts by O. niloticus but only in aggressive situations (fleeing or avoidance) by S. melanotheron. The second type of sounds produced by O. niloticus were grunts, produced in both aggressive (chasing and after biting) and non-aggressive contexts (nest building). The second type of sound produced by S. melanotheron was a rolling sound, produced only during courtship. Each species was able to produce common sounds (drum) and species-specific sounds (grunts and rolling). This implies that species can communicate without being able to understand each other because the sounds emitted may probably have different significance. Drumming corresponded only to aggressivity in S. melanotheron, whereas this was not true for O. niloticus. 11-ketotestosterone (11-kt) levels were significantly higher in male O. niloticus than male S. melanotheron, but there was no significant correlation between 11-kt or estradiol concentrations and the number of sounds produced in aggressive or non-aggressive behavioural contexts in either species. During interspecies interactions, O. niloticus drum sounds are likely considered to be aggressive by S. melanotheron and could potentially constitute a reproductive barrier between the two species.
... 2002). The outcomes of these aggressive interactions beyond influencing access to food, has also been shown in prior studies to greatly influence the sounds produced by the cichlid Oreochromis mossambicus during courtship, with the dominants having relatively longer pulse durations than defeated males (Amorim and Almada, 2005). ...
In order to get access to limited resources in the environment, the Oreochromis niloticus has been observed to resort to agonistic interactions, the winner of such interaction generally being a high-ranking individual in the observed group. This study investigated the effects of dominance hierarchies on behavior and physiological
responses within three groups of Nile tilapia in an experimental setup consisting of clear glass aquaria.
Several trials were run to observe how scale loss, gill ventilation rates and aggression with reducing oxygen levels, as well as food deprivation 72 hours were influenced by hierarchy expression in the different social groupings and how that affected observed growth and
biological indices and hematological evaluations of dominant and subordinate fish.
The results of this study provide evidence to the fact that out of the practice of graded culture must therefore be adopted in order to reduce the effects of hierarchies in aquaculture production of Nile tilapia.
... This is in agreement with the literature on social competence, which proposes that animals within a social context will optimise their behaviour based on the available information and previous experiences 12,13 . Even though it is highly adaptive for individuals to know when to show submissive behaviour, being subordinate is costly for the individual, as it is associated with reduced reproduction, low activity levels, reduced growth and suppressed aggression and feeding 10,37,48,49 . In this context, it is important to consider that even though behavioural inhibition may have negative consequences for the www.nature.com/scientificreports ...
Recent theories in evolutionary medicine have suggested that behavioural outputs associated with depression-like states (DLS) could be an adaptation to unpredictable and precarious situations. In animal models, DLS are often linked to diverse and unpredictable stressors or adverse experiences. Theoretically, there are a range of potential fitness benefits associated with behavioural inhibition (typical to DLS), as opposed to more active/aggressive responses to adverse or uncontrollable events. This stance of evolutionary medicine has to our knowledge not been tested empirically. Here we address a possible key benefit of behavioural inhibition in a comparative model for social stress (territorial rainbow trout). By treating fish with the fast-acting antidepressant ketamine, we reversed the behavioural inhibition (i.e. stimulated an increase in activity level) in subordinate fish. During confrontation with a previously unfamiliar larger, aggressive and dominant individual, this increase in activity led to higher amounts of received aggression compared to sham-treated subordinates. This suggests that the behavioural inhibition characterizing animal models of DLS is indeed an effective coping strategy that reduces the risk of injuries in vulnerable social situations.
... These activities might be credited to dominance and subordinate hierarchies established within the aquaria. Dominant tilapia are known to swim freely in the aquarium, chasing or attacking subordinate fish; subordinate tilapia are known to swim slowly, withdraw in the face of a challenge by dominant fish, stay at the top or bottom of the water column and exhibit more injuries than dominant fish (Amorim and Almada, 2005;Correa et al, 2003). The ability of fish to access food is a prime factor determining discrepancy in weight (Yousif, 2002). ...
To investigate the impacts of rearing density and oregano essential oil (OEO) supplementation on growth, behavioral and stress response of Nile tilapia, a factorial design (3 × 3 × 2) was assembled using 18 (100 L) glass aquaria where each aquarium had a rearing density and an OEO supplemental level. Six aquaria had a density of 10 fish aquarium⁻¹ (low rearing density; LRD), another six had a density of 20 fish aquarium⁻¹ (medium rearing density; MRD) and the remaining six aquaria had a density of 40 fish aquarium⁻¹ (high rearing density; HRD). For each rearing density, fish were fed three diets with variable OEO levels (0.0, 1.0, and 2 ml kg⁻¹ diet) and were assayed in two replicas for 10 weeks. OEO improved the growth performance of fish maintained at LRD and MRD. Tilapia exhibited behavioral changes in all densities with a reduced aggression in the HRD group. The OEO reduced the oxidative stress and the aggressiveness of juvenile tilapia as deduced from stress and welfare indicators’ levels (cortisol antioxidant enzymes). In addition, a density-stress related effect as well as a nonspecific immune stimulant effect of OEO was detected from the increased antioxidant and NO activity in this study.
... In mosquitofish, the winner effect might increase the frequency of male pursuit of females if the experience of winning boosts androgen production and male harassment is correlated with higher androgen levels, as is courtship behaviour in other fishes (e.g. [13]). Males that lose aggressive contests often incur greater costs than those that win them (e.g. ...
Winning or losing a fight can have lasting effects on competitors. Controlling for inherent fighting ability and other factors, a history of winning often makes individuals more likely to win future contests, while the opposite is true for losers (the 'winner-loser effect'). But does the winner-loser effect also influence a male's mating success? We experimentally staged contests between male mosquitofish (Gambusia holbrooki) such that focal males either won or lost three successive encounters with stimulus males. We then placed a size-matched (to control for inherent fighting ability) winner and loser with a female and monitored their behaviour (n = 63 trios). Winners spent significantly more time associating with the female. Winners did not make more copulation attempts, nor have a greater number of successful attempts. There was, however, a significant effect of male size on the number of successful copulation attempts: success decreased with male size for losers, but size had no effect on the success rate of winners.
... Moreover, Eitan and Timmers [52] reported that participants when asked tend to match low pitch to words that are related to bigness such as attributes like "thick, heavy, strong, and male" or objects like "crocodile", while the opposite holds for high pitch. Finally, evidence from studies of animal behavior indicates that in many animal species, the voice pitch of males predicts their social status and mating success [53][54][55]. Similarly, studies of human verbal interaction revealed that voice pitch is a good indicator of a male's attractiveness for females, as well as his-actual or alleged-physical or social dominance [56][57][58][59][60][61][62]. ...
The concept of sound iconicity implies that phonemes are intrinsically associated with non-acoustic phenomena, such as emotional expression, object size or shape, or other perceptual features. In this respect, sound iconicity is related to other forms of cross-modal associations in which stimuli from different sensory modalities are associated with each other due to the implicitly perceived correspondence of their primal features. One prominent example is the association between vowels, categorized according to their place of articulation, and size, with back vowels being associated with bigness and front vowels with smallness. However, to date the relative influence of perceptual and conceptual cognitive processing on this association is not clear. To bridge this gap, three experiments were conducted in which associations between nonsense words and pictures of animals or emotional body postures were tested. In these experiments participants had to infer the relation between visual stimuli and the notion of size from the content of the pictures, while directly perceivable features did not support–or even contradicted–the predicted association. Results show that implicit associations between articulatory-acoustic characteristics of phonemes and pictures are mainly influenced by semantic features, i.e., the content of a picture, whereas the influence of perceivable features, i.e., size or shape, is overridden. This suggests that abstract semantic concepts can function as an interface between different sensory modalities, facilitating cross-modal associations.
... Dominance may also directly affect factors involved in mate choice. For example, males of some species court females more after winning a contest than losing males (Greenberg & Crews, 1990;Amorim & Almada, 2005;LaManna & Eason, 2010). In addition, the physiological stress response associated with being subordinate may cause reproductive impairment or decreased sexual behaviour (Cameron, 1997;Fox et al., 1997;Creel, 2001;Hardy et al., 2002;Moore et al., 2005;Edeline et al., 2010). ...
For species in which individuals spend at least some time in groups, dominance relationships and various social cues are often important for mate assessment and choice. For pair bonding species, social experiences may affect reproductive decisions in both sexes. We tested whether prior experience in a mixed-sex group and having a higher dominance status coincides with faster pair formation or spawning in a monogamous fish. Individuals having prior experience in mixed-sex groups paired with a novel fish more frequently than fish from same-sex groups. Fish in mixed-sex groups performed more bites and lateral displays. Although spawning occurred infrequently across pairs, dominant fish from mixed-sex groups spawned more than dominant fish from same-sex groups. Otherwise, there were no clear behavioural relationships between treatment group and subsequent pair formation or spawning, nor were behaviours of the paired fishes related to their prior treatment group. We do not know how mixed-sex social experience may have affected the physiology of those individuals, although our results support a reproductive priming effect.
... Fish also rely on pressure waves created by the shoal, which play a role in alarm, distress signalling [116] and spawning [117]. Fish also respond to sound [118][119][120] and produce it [121,122], for example during swimming, at least within shoals [123,124] and during spawning [125][126][127]. Pressure waves and noise emitted from boats are, therefore, likely to interfere with social behaviour, including communication [110], orientation and avoidance behaviour, and interrupt spawning. ...
Recreational fishing in freshwater ecosystems is a popular pastime in Australia. Although most native fish are endemic, the fauna is depauperate compared to any landmass of similar size. With commercial fishing no longer a major industry in the country’s freshwaters, the future sustainability of these ecosystems will depend heavily on the actions of recreational fishers. However, there has been limited focus on the consequences of recreational fishing in freshwaters. There is particularly a dearth of information on the indirect consequences of fishers on the waterbodies they depend on for their sport. After outlining the respective trends in commercial and recreational fishing in Australia as a basis for placing the sport in context, the indirect impacts of fishers on water quality, movement (walking, off-road vehicles), the introduction/translocation of fauna (particularly fish), the dispersal of flora and the transmission of fish disease and pathogens are reviewed. It is concluded that with the decline of commercial fishing, the competition between commercial fin-fishing and recreational fishing is negligible, at least throughout most of the country. It is also concluded that each of the issues addressed has the potential to be detrimental to the long-term sustainability of the freshwater ecosystems that the fishers depend on for their recreation. However, information on these issues is scant. This is despite the current and predicted popularity of freshwater recreational fishing continuing to increase in Australia. Indeed, there has been insufficient quantitative assessment of the impacts to even determine what is required to ensure a comprehensive, adequate and representative protection of these freshwater ecosystems. To underpin the sustainability of inland recreational fishing in the country, it was concluded that research is required to underpin the development and implementation of appropriate policies. The alternative is that the integrity and biodiversity loss of these ecosystems will ultimately result in their collapse before the indirect consequences of recreational fishing have been directly assessed and appropriately protected. However, the lack of protection of wetlands is not restricted to Australia; there is a deficit of freshwater protected areas worldwide.
... However, a study by Lobel and Mann (1995) demonstrated that while such a correlation exists, it was highly variable suggesting that other factors were influencing individual peak frequency values. It was further demonstrated in the cichlid, Oreochromis mossambicus, that social status influenced spectral properties of male vocalizations, including peak frequency (Amorim & Almada 2005). Vocalizations can vary among species in measurements of pulse number, pulse duration and interpulse interval (Maruska et al. 2007). ...
Damselfishes are well known for their aggressive, territorial behaviour during which the use of vocalization behaviour has been well documented. However, agonistic acoustic signalling has been understudied in particular when the vocalizations are interspecific. In this study, we characterize and compare the previously undescribed vocalization behaviour of longfin damselfish (Stegastes diencaeus), in an agonistic context, with the closely related and sympatric dusky damselfish (Stegastes adustus). Next, we examined if these congeneric species modulate their vocalizations in a similar pattern to previously described aggressive behaviour patterns. Audio field recordings of territorial males were obtained in response to three separate stimuli: (1) conspecific male damselfish, (2) heterospecific male damselfish and (3) a common intruder, the slippery dick wrasse (Halichoeres bivittatus). The vocal repertoires of both longfin and dusky damselfish comprised the same three distinct call types: chirps, pops and pulse trains. However, temporal measures of the calls showed significant differences between species. Additionally, dusky damselfish were more vocal overall, producing more calls and spending more time calling than longfin damselfish. These responses were stimulus and species dependent, as the two species modulated acoustic response by modulating pulse number based on intruder species. These results suggest that these closely related species of damselfish use vocalization behaviours that are both unique and context dependent.
... When fighting for a territory and establishing social hierarchies, males engage in frequent male-male agonistic interactions where they use both visual and chemical signals (Keller-Costa et al. 2015). Besides visual and chemical displays (Keller-Costa et al. 2015), territorial males also produce low-frequency pulsed acoustic signals (drums) during courtship and spawning (Amorim et al. 2003;Amorim and Almada 2005). ...
Multimodal communication is essential in social interactions in cichlid fish, including conspecifics’ recognition, agonistic interactions and courtship behaviour. Computer-manipulated image stimuli and sound playback offer powerful tools to assess the relative relevance of visual and acoustic stimuli in fish behavioural studies, but these techniques require validation for each taxon. The aim of the present study was to investigate whether Mozambique tilapia Oreochromis mossambicus responds to computer-manipulated visual stimuli and acoustic playback. Six experiments were conducted: computer animation playback, video playback, interaction with a mirror, presentation of a live male in a jar alone and combined with courting sound playback or with white noise playback. Individual agonistic interactions (lateral displays, up and down swimming, butting) and courting behaviours (tilting leading, digging) were tallied for each experiment. Our results suggest that non-interactive computer-manipulated visual stimuli is not a suitable tool in behavioural research with Mozambique tilapia. In contrast, interaction with a live male in a jar seems to remain the best visual research instrument inducing significant strong behavioural responses. Although none or only a few agonistic interactions were observed towards video playbacks or computer animations, such interactions significantly increased towards a male in jar and were modulated by courtship sound playback, suggesting the additional relevance of sound playback as a tool in behavioural research with Mozambique tilapia, including the study of multimodal signalling.
... In Figure 2 showed pulse length, frequency spectra, and oscillogram in highest value in frequency. This results clearly show that the calculations or methods bioacoustic to fish is needed to determine the productivity and health of the fish [17][18][19][20][21][22][23]. ...
Sound production of male fish-black Tilapia (Oreochromis mossambicus) used bioacoustic method where this method can be analyze behavior and characteristics of the sound production bubbles of tilapia fish swimming in freshwaters with different salinity. Research activities conducted in June 2013, fish were reared in our Institute's laboratory (Marine Acoustic) as much as 65 males fish-black Tilapia (Oreochromis mossambicus). Sounds were recorded with a High Tech SQ 03 hydrophone (sensitivity-162 dB re 1 VµPa-1 @20°C, frequency response within ± 1 dB from 7 Hz to 22 kHz) placed just above the rim of a territorial in aquaria with connected to sea phone sensor (Dolphin Ear), with recording software is Wavelab 6, and analysis software of Source Level, and Power Spectral Density (PSD) is Matlab R2008 b. Source level (SL) value is highest on first day after adding saline to 39.11 dB, while the lowest values were also in first day after adding salt levels are 38.72 dB, it clearly proves that the addition of salt levels can affect the value of source level (SL). Highest of PSD in after adding salinity first day with-39.03 dB/Hz, and the lowest value of the PSD which in adding to the salt levels in second day is-49.04 dB/Hz. The results shown prove the effect of salinity on the value of the PSD and also SL. Addition of salt levels greatly affect the value of the intensity, frequency, source level (SL), and power spectral density (PSD) of male fish-black Tilapia (Oreochromis mossambicus).
... For example, in males of the house cricket, Acheta domesticus, winners exhibit higher mating success Fig. 2 The median of the copulation attempts for the experimental males throughout the experiment, before, and after fights than losers but do not show clear differences in courtship behavior (Nelson and Nolen 1997). Conversely, winners in the Mozambique tilapia, Oreochromis mossambicus, court females more than losers (Amorim and Almada 2005). Finally, in the neriid fly Telostylinus angusticollis, loser male copulations are longer than winner male copulations, which results in increased reproductive success (Fricke et al. 2015). ...
In animals, correlations exist among behaviors within individuals, but it is unclear whether experience in a specific functional context can affect behavior across different contexts. Here, we use Drosophila melanogaster to investigate the effects of conflict-induced behavioral modifications on male mating behavior. In D. melanogaster, males fight for territories and experience a strong winner-loser effect, meaning that winners become more likely to win subsequent fights compared to losers, who continue to lose. In our protocol, males were tested for courtship intensity before and after fighting against other males. We show that male motivation to copulate before fights cannot predict the fight outcomes, but that, afterwards, losers mate less than before and less than winner and control males. Contrarily, winners show no differences between pre- and post-fight courtship intensity, and do not differ from control males. This suggests that the physiological modifications resulting from fight outcomes indirectly affect male reproductive behavior.
... 2005). This species is thought to be highly socialized, using pulsed acoustic signals to communicate before, during and after mating (Amorim and Almada 2005), and females are mouth brooders meaning that buccal protection maximizes early survival in the offspring (Merrick and Schmida 1984). ...
Exotic speCies complicate the management of native biological diversity and their ecosystems, because their effects are pervasive and varied (Cox 2004). For example, they can be beneficial and integral components of global agricultural economies (Sax et al, 2007), but when unmanaged and by definition invasive, they can negatively change important variables such as the genetics and population size of individual species, the diversity and structure of ecological communities, disturbance regimes and biogeochemical cycling (Vitousek 1990).
... A study with males of the croaking gourami T. vittata revealed that the sounds of winners had higher sound pressure levels and lower dominant frequencies than losers, and that these acoustical features were good predictors of male body mass (Ladich 1998). In the tilapia Oreochromis mossambicus, males that won encounters with other males produced more courtship sounds when subsequently allowed to court with females, and presented longer pulse durations and lower dominant frequencies for a given length (Amorim and Almada, 2005). ...
Fish sound characteristics are associated with different sound-generating mechanisms. Sounds produced by swimbladder-related mechanisms usually comprise low-frequency pulses produced at different rates. Fishes emit one to five sound types that do not show such outstanding variability as found in other taxa. However, closely related species show consistent differences in their sounds and in some species even individuality is found. Of particular interest are differences in courtship sounds made by closely related sympatric species that may promote reproductive isolation. Differences between individuals of the same species may in turn play a role in sexual selection through male-male competition and female mate choice. Other known sources of variability are related to context, including motivation and recent social status, season, time of day, ontogenetic changes and sexual dimorphism. Fish sound variability is mainly based on temporal patterning of sounds or pulses within a sound and on frequency variation (sometimes modulation). Such variability has been found to play a role in the social life of fishes.
... During courtship, calls can be used by females to assess species identity and the quality of potential sexual partners (18)(19)(20)(21). During agonistic behaviors, sound features enable the receiver to assess the fighting capacity of the opponent because acoustic parameters can provide information on the size, the social status, the motivation, or the physiological state of the emitter (22)(23)(24)(25). However, how fish sounds are organized at the level of the community remains unknown. ...
Significance
More and more studies stress the potential deleterious effect of anthropogenic sounds on fish acoustic communication. Paradoxically, how the communication between fishes in a community is organized remains extremely poorly known, as studies using passive acoustic recordings are typically restricted to one or two species. At a single site, we were able to follow 16 different vertebrate sounds for 15 days. We demonstrate that the fish population can be distributed into two groups: one diurnal and one nocturnal. Most interestingly, fish calling at night do not show overlap at the level of the main calling frequency, in contrast to fish calling during the day. This shows that at night, in the absence of visual cues, sound communication is more important.
The importance of olfaction in spawning of medaka Oryzias latipes was established for the first time by observation of spawning behavior by fish subjected to an olfactory blockage. Experimental fish were prepared by (1) covering the nostrils on both sides (bilateral treatment), thereby excluding all olfactory stimuli, and (2) covering nostrils on one side only (unilateral treatment), thereby giving partial exclusion. A control group comprised untreated (intact). Experiments conducted for both males (bilateral male-intact female, unilateral male-intact female and intact male-intact female) and females (bilateral female-intact male, unilateral female-intact male and intact female-intact male) resulted in no spawning by intact females paired with bilateral males, whereas spawning occurred in intact females paired with both unilateral and intact males. Spawning also occurred when intact males were paired with intact, unilateral or bilateral females, indicating that olfactory stimuli were necessary for males to complete spawning, but not so for females. Spawning acts exhibited from pairing started by bilateral males-intact female pairs included “following” (initial act of following female), “positioning” (lateral courtship display), and “quick circle” (turning in front of female), but they did not include “contact” (bodies in contact posteriorly prior to gamete release), “wrapping” (male embracing female using their dorsal and anal fins during gamete release). On the other hand, intact and unilateral males participated in all of the above spawning acts, indicating that olfactory stimuli are indispensable for behavior concerning emitting semen.
The maintenance of high health and welfare in breeding and juvenile tilapias is impacted, on the one hand, by the natural reproductive biology and behaviour of the animals and, on the other, by system design and management. The nature and level of risks that pathogens, parasites, and pests impose is linked to scale and intensity of hatchery operation, and potential for implementing biosecurity measures. The demand for more productive and consistent grow-out performance has led to the application of monosex technology and the development of selectively superior stocks, necessitating intensive hatchery approaches. Achieving favourable health and welfare outcomes in breeding and juvenile fish requires careful consideration of handling, density, and environmental factors. Selective breeding, nutrition and water quality management all have important roles in maintaining or improving health and robustness of stocks. Temperature control has particular importance in juvenile production in many locations, particularly those experiencing seasonality. The core strategy involves selective breeding for disease-resistant traits, that can be accelerated by advancements in genomic selection. Optimal hatchery design, site selection, and husbandry practices contribute to reducing stress and enhancing the immune systems of tilapia. General handling, sedation, grading, and transportation during juvenile production are considered in terms of practical application and best practice to reduce physical and physiological trauma that leads to poor health outcomes. Crucial components of robust biosecurity protocols include quarantine measures and a comprehensive understanding of vertical pathogen transmission, fostering sustainable practices in tilapia farming.
Kobayashi.2012. Involvement of olfaction in spawning success of medaka Oryzias latipes. Japan. J. Ichthyol., 59(2): 111-124. Abstract The importance of olfaction in spawning of medaka Oryzias latipes was established for the first time by observation of spawning behavior by fish subjected to an olfactory blockage. Experimental fish were prepared by (1) covering the nostrils on both sides (bilateral treatment), thereby excluding all olfactory stimuli, and (2) covering nostrils on one side only (unilateral treatment), thereby giving partial exclusion. A control group comprised untreated (intact). Experiments conducted for both males (bilateral male-intact female, unilateral male-intact female and intact male-intact female) and females (bilateral female-intact male, unilateral female-intact male and intact female-intact male) resulted in no spawning by intact females paired with bilateral males, whereas spawning occurred in intact females paired with both unilateral and intact males. Spawning also occurred when intact males were paired with intact, unilateral or bilateral females, indicating that olfactory stimuli were necessary for males to complete spawning, but not so for females. Spawning acts exhibited from pairing started by bilateral males-intact female pairs included "following" (initial act of following female), "positioning" (lateral courtship display), and "quick circle" (turning in front of female), but they did not include "contact" (bodies in contact posteriorly prior to gamete release), "wrapping" (male embracing female using their dorsal and anal fins during gamete release). On the other hand, intact and unilateral males participated in all of the above spawning acts, indicating that olfactory stimuli are indispensable for behavior concerning emitting semen.
Kobayashi.2012. Involvement of olfaction in spawning success of medaka Oryzias latipes. Japan. J. Ichthyol., 59(2): 111-124. Abstract The importance of olfaction in spawning of medaka Oryzias latipes was established for the first time by observation of spawning behavior by fish subjected to an olfactory blockage. Experimental fish were prepared by (1) covering the nostrils on both sides (bilateral treatment), thereby excluding all olfactory stimuli, and (2) covering nostrils on one side only (unilateral treatment), thereby giving partial exclusion. A control group comprised untreated (intact). Experiments conducted for both males (bilateral male-intact female, unilateral male-intact female and intact male-intact female) and females (bilateral female-intact male, unilateral female-intact male and intact female-intact male) resulted in no spawning by intact females paired with bilateral males, whereas spawning occurred in intact females paired with both unilateral and intact males. Spawning also occurred when intact males were paired with intact, unilateral or bilateral females, indicating that olfactory stimuli were necessary for males to complete spawning, but not so for females. Spawning acts exhibited from pairing started by bilateral males-intact female pairs included "following" (initial act of following female), "positioning" (lateral courtship display), and "quick circle" (turning in front of female), but they did not include "contact" (bodies in contact posteriorly prior to gamete release), "wrapping" (male embracing female using their dorsal and anal fins during gamete release). On the other hand, intact and unilateral males participated in all of the above spawning acts, indicating that olfactory stimuli are indispensable for behavior concerning emitting semen.
During courtship, prezygotic barriers are thought to maintain the diversity of species since differences in phenotypic traits and reproductive behaviours are likely to be involved in maintaining species boundaries. However, introgressive hybridization has been reported in many different taxa and the resulting hybrids usually possess phenotypic features, including behaviours, that are intermediate between those of the parents. The outcome of hybrids may depend on the interactions between the intrinsic viability of the hybrids, the ecological environment of the species, and the fitness of hybrids in that ecological context. In cichlids, the mechanism of hybridization is increasingly documented as an important factor in their evolutionary radiation since it may provide novel gene combinations that promote speciation and adaptive radiation by generating new transgressive phenotypes. Cichlid species are separated mostly by pre-mating isolating mechanisms. Like colour patterns, acoustic communication is involved in sexual selection, but this pattern has been much less studied and the outcome of hybridization on acoustic features has never been examined. To gain novel insights into the evolution of their acoustic communication behaviour, we performed a hybrid cross between Chindongo saulosi and Maylandia estherae. Qualitative examination of courtship showed that the three groups possess the same sequence of behaviours. However, sounds produced during courtship showed specific signatures since all three groups differ at the level of sound duration and pulse period, with both features being intermediate in hybrids in comparison to the two parent species. Colour patterns in hybrids were also different from those of the parent species. These results show that hybridization can affect at least two kinds of prezygotic barriers, which may be important in the cichlid evolutionary process. However, playback experiments are required to test the strength of these features in sexual selection.
Contests are an important aspect of the lives of diverse animals, from sea anemones competing for space on a rocky shore to fallow deer stags contending for access to females. Why do animals fight? What determines when fights stop and which contestant wins? Addressing fundamental questions on contest behaviour, this volume presents theoretical and empirical perspectives across a range of species. The historical development of contest research, the evolutionary theory of both dyadic and multiparty contests, and approaches to experimental design and data analysis are discussed in the first chapters. This is followed by reviews of research in key animal taxa, from the use of aerial displays and assessment rules in butterflies and the developmental biology of weapons in beetles, through to interstate warfare in humans. The final chapter considers future directions and applications of contest research, making this a comprehensive resource for both graduate students and researchers in the field.
Contests are an important aspect of the lives of diverse animals, from sea anemones competing for space on a rocky shore to fallow deer stags contending for access to females. Why do animals fight? What determines when fights stop and which contestant wins? Addressing fundamental questions on contest behaviour, this volume presents theoretical and empirical perspectives across a range of species. The historical development of contest research, the evolutionary theory of both dyadic and multiparty contests, and approaches to experimental design and data analysis are discussed in the first chapters. This is followed by reviews of research in key animal taxa, from the use of aerial displays and assessment rules in butterflies and the developmental biology of weapons in beetles, through to interstate warfare in humans. The final chapter considers future directions and applications of contest research, making this a comprehensive resource for both graduate students and researchers in the field.
Fight outcomes often affect male fitness by determining their access to mates. Thus, "winner-loser" effects, where winners often win their next contest while losers tend to lose, can influence how males allocate resources toward pre- and postcopulatory traits. We experimentally manipulated the winning/losing experiences of pairs of size-matched male Gambusia holbrooki for 1 day, 1 week, or 3 weeks to test whether prior winning/losing experiences differentially affect the plasticity of male investment into either mating effort (precopulatory) or ejaculates (postcopulatory). When winner/loser pairs directly competed for a female, winners had better precopulatory outcomes than losers for three of the four traits we measured: mating attempts, successful attempts, and time spent with the female (but not aggression). However, winners and losers did not differ in either total sperm counts or sperm velocity. Interestingly, absolute male size, an important predictor of fighting success, mediated winner-loser effects on how long males then spent near a female. Compared with losers, smaller winners spent more time with the female than did larger winners, suggesting that how males respond to prior social experiences is size dependent. We discuss the general importance of controlling for inherent male condition when comparing male investment into condition-dependent traits.
Animals often need to signal to attract mates and behavioural signalling may impose substantial energetic and fitness costs to signallers. Consequently, individuals often strategically adjust signalling effort to maximize the fitness payoffs of signalling. An important determinant of these payoffs is individual state, which can influence the resources available to signallers, their likelihood of mating and their motivation to mate. However, empirical studies often find contradictory patterns of state-based signalling behaviour. For example, individuals in poor condition may signal less than those in good condition to conserve resources (ability-based signalling) or signal more to maximize short-term reproductive success (needs-based signalling). To clarify this relationship, I systematically searched for published studies examining animal sexual signalling behaviour in relation to six aspects of individual state: age, mated status, attractiveness, body size, condition and parasite load. Across 228 studies and 147 species, individuals (who were predominantly male) invested more into behavioural signalling when in good condition. Overall, this suggests that animal sexual signalling behaviour is generally honest and ability-based. However, the magnitude of state-dependent plasticity was small and there was a large amount of between-study heterogeneity that remains unexplained.
‘Winner’ and ‘loser’ effects have been demonstrated in a broad range of species, but such investigations are often limited to the effects of prior contest outcomes on future agonistic interactions. Much less is known about the impacts of winning or losing contests on other aspects of individual behavior, like courtship interactions and sheltering behavior. In this investigation, I examined the effect of prior contest outcomes on sheltering behavior in the crayfish Faxonius virilis. I predicted that winners of contests would spend less time inside shelters and more time exploring, while losers of contests would spend more time inside shelters and less time exploring. I compared individual sheltering behavior before and after staged dyadic encounters between competitively mismatched individuals. This experiment revealed strong effects on the behavior of contest losers, which showed significant increases in the amount of time spent inside the shelter immediately after the contest. However, there was no significant change in the sheltering behavior of contest winners. These results reinforce the idea that contest outcomes can affect individual behaviors other than agonistic behavior, and suggest that losing a contest may motivate individual crayfish to engage in less-risky behavior, at least for a brief period after the contest.
Animal interactions such as competition are mediated by complex social strategies, which consist of behaviours and cognitive mechanisms that guide their production. As a result, behaviour is highly flexible. This poses a challenge to understanding how competition plays out in natural systems, because the course of a contest can essentially be rewritten by prior experience and/or changes in social context. Here we addressed this gap by studying how both of these factors interact to reconfigure competitive strategies used in territorial defence by a wild bird. After experimentally inducing the winner effect, a cognitive-behavioural phenomenon in which winning a contest increases the probability of winning again in the future, we found that male red-bellied woodpeckers, Melanerpes carolinus, adopted a new social strategy marked by more flexible transitions between different aggressive displays, as well as increasing overall aggressive output. However, this effect was mitigated by the arrival of the female social mate; in response to this momentary shift in social context, males decreased their use of territorial drum displays and became less likely to move around the territory or switch display modes during competition. In other words, the winner effect increased spatiotemporal diversity of territorial strategies, such that males frequently changed their location and display output. A female's arrival, however, reversed this effect. More specifically, males tended to revert to advertisement and social vocalizations on female arrival, which suggests that the need to attend to the social mate may supersede the threat of territorial intrusion. This is consistent with a model in which competitive outcomes are impacted by the interactive effects of an individual's past experiences and shifts in present-day social context, which may allow monogamous animals to effectively manage the competing demands of driving off intruders and attending to the social mate.
Fish respond to their “reproductive duty” and their reproductive needs by adopting a large diversity of adaptive behaviors in relation to constraints exerted by environmental conditions. Most spawners abandon their offspring and return to their feeding habitats. The reproductive scenario can be broadly divided into four major phases: an anticipatory phase, a preparatory or pre‐spawning phase, a phase of realization or spawning, and a terminal or postspawning phase. The partners of both sexes, having made the effort to promote themselves and to display their qualities, owe it to themselves to reap the benefits and to carry out couplings which promise beautiful reproductive success as quickly as possible. Reproductive migrations involve movements of spawners of varied magnitude and variable duration according to the species. Most species practice large sexual freedom with frequent changes of partners, which offers the advantage of a large mixing of genes inducing a large genetic diversity that is beneficial to the population.
Information transfer between individuals typically depends on multiple sensory channels. Yet, how multi-sensory inputs shape adaptive behavioural decisions remains largely unexplored. We tested the relative importance of audio and visual sensory modalities in opponent size assessment in the vocal cichlid fish, Metriaclima zebra, by playing back mismatched agonistic sounds mimicking larger or smaller opponents during fights of size-matched males. Trials consisted in three 5-min periods: PRE (visual), PBK (acoustic+visual) and POST (visual). During PBK agonistic sounds of smaller (high frequency or low amplitude) or larger (low frequency or high amplitude) males were played back interactively. As a control, we used white noise and silence. We show that sound frequency but not amplitude affects aggression, indicating that spectral cues reliably signal fighting ability. In addition, males reacted to the contrasting audio-visual information by giving prevalence to the sensory channel signalling a larger opponent. Our results suggest that fish can compare the relevance of information provided by different sensory inputs to make behavioural decisions during fights, which ultimately contributes to their individual fitness. These findings have implications for our understanding of the role of multi-sensory inputs in shaping behavioural output during conflicts in vertebrates.
Animals engage in costly agonistic contests during which winners procure resources. During these interactions, the combatants obtain and use information to make decisions on whether to persist or to withdraw from the fight, which is termed assessment. Recent theory and work have suggested that the types of assessment employed may be more variable than previously thought, with the use of different strategies possibly being influenced by social and ecological conditions during priming. This study addresses the contextual components (social and ecological) that affect the utilization of one assessment strategy over another. Male tilapia were primed with different combinations of social (large and small animals) and ecological (resource rich or poor) contexts 24 hr prior to fighting in staged, dyadic contests. When opponents were primed with the same context, a clear assessment strategy emerged and differed as a function of priming treatment. Conversely, when fish were primed with different treatment contexts, there was no discernible assessment. In addition, priming conditions had differing effects for large and small fish. Thus, assessment strategies in cichlids are dependent upon a combination of social, ecological contexts and size of the animal. Since assessment strategies change as a function of both of these contexts, as well as others, future framework investigating assessment strategies should include both intrinsic and extrinsic factors that may shape fighting dynamics.
The presence of a predator can result in the alteration, loss or reversal of a mating preference. Under predation risk, females often change their initial preference for conspicuous males, favouring less flashy males to reduce the risk of being detected by predators. Previous studies on predator-induced plasticity in mate preferences have given females a choice between more and less conspicuous conspecific males. However, in species that naturally hybridize, it is also possible that females might choose an inconspicuous heterospecific male over a conspicuous conspecific male under predation risk. Our study addresses this question using the green swordtail (Xiphophorus helleri) and the southern platyfish (Xiphophorus maculatus), which are sympatric in the wild. We hypothesized that X. helleri females would prefer the sworded conspecific males in the absence of a predator but favour the less conspicuous, swordless, heterospecific males in the presence of a predator. Contrary to our expectation, females associated more with the heterospecific male than the conspecific male in the control (no predator) treatment, and they were non-choosy in the predator treatment. This might reflect that females were attracted to the novel male phenotype when there was no risk of predation but became more neophobic after predator exposure. Regardless of the underlying mechanism, our results suggest that predation pressure may affect female preferences for conspecific versus heterospecific males. We also found striking within-population, between-individual variation in behavioural plasticity: females differed in the strength and direction of their preferences, as well as in the extent to which they altered their preferences in response to changes in perceived predation risk. Such variation in female preferences for heterospecific males could potentially lead to temporal and spatial variation in hybridization rates in the wild.
Females often prefer males with bright, showy, or large secondary sexual characters. However, social experience can result
in variation in female preferences, with evidence of sexual imprinting in some taxa. In the brush-legged wolf spider, Schizocosa ocreata, asynchrony of maturation provides a time period in which imprinting may occur. We tested whether adult females demonstrated
plasticity in their visual preferences for male leg tuft size after experience with digitally courting males during their
penultimate stage. Penultimate instar females were presented visual courtship signals from males with small, average, or large
tufts; a mixture of tuft sizes; or no males at all. During Week 2 of adulthood, each female was presented playback of digital
courting small- and/or large-tufted males in both no-choice and two-choice presentations. Adult female preferences varied
significantly with prior experience. Females exposed to only large-tufted males or males with a mixture of tuft sizes demonstrated
more receptivity displays to large-tufted males than small-tufted males. Females exposed to only small-tufted males demonstrated
more receptivity displays toward small-tufted males than large-tufted males. Because results suggested the possibility of
sexual imprinting, we tested for reversibility. A subset of females was retested for selectivity in two-choice trials, revealing
a positive correlation between Week 2 and Week 5 female selectivity. Females previously exposed to small-tufted males, however,
no longer maintained their preference for small-tufted males in Week 5. This study demonstrates the effects of an individual’s
social environment on mating preferences, and the importance of age and timing when studying sexual imprinting.
It has been demonstrated from free mating experiments using multiple males and females of the medaka, Oryzias latipes species complex, that lower-latitude males exhibit more active courtship behavior than higher-latitude males. In this study, courtship activeness in males from two latitudinal populations of Northern medaka, Oryzias sakaizumii, was measured in the presence of only one male and one female, where male–male interactions were completely eliminated. We found that males from the low-latitude population performed quick circles (i.e., courtship dance) and approached females more frequently than males from the high-latitude population. Moreover, the low-latitude males tended to start courtships sooner after encountering a female than the high-latitude males. Thus, the latitudinal variation in male courtship activeness persisted even in the absence of rival males. These probably reflect that sexual selection pressures are stronger at low latitudes.
Sexual selection is one of the main evolutionary forces that drive signal evolution. In previous studies, we have found out that males of Pleurodema thaul, a frog with an extensive latitudinal distribution in Chile, emits advertisement calls that show remarkable variation among populations. In addition, this variation is related to intense inter-male acoustic competition (intra-sexual selection) occurring within each population. However, the extent to which female preferences contribute to the signal divergence observed is unclear. To study the responsiveness of females in each population, we stimulated females with synthetic calls designed with the acoustic structure of their own population and subsequently responsive females were subjected to a two-choice experiment, where they were stimulated with synthetic calls of their own population versus a call of a foreign population. Females do not show phonotactic preferences for calls of their own or foreign populations as measured with both linear and circular variables. The lack of phonotactic preferences suggests an absence of participation of inter-sexual selection processes in the divergence of the acoustic signals of P. thaul, highlighting the importance of intra-sexual selection for the evolution of these signals. These results concur with studies in other vertebrates emphasizing the relevance of interactions among males for the evolution of acoustic communication systems.
Copyright © 2015. Published by Elsevier B.V.
Various species of fish are known to produce sounds in different social contexts suggesting an important communicative role of acoustic signals. The aim of this thesis is to study the structure and the function of sounds produced during aggressive interactions between males of the cichlid fish Metriaclima zebra. By means of playback experiments, the relative role of acoustic and visual cues during agonistic interactions is evaluated. The results show that aggressive behaviour is essentially based on visual stimuli. Acoustic stimuli alone never trigger aggression but modulate males' behavior by decreasing the high level of aggressiveness found when only the visual channel is present. A fine analysis of the structure of sounds produced during disputes shows that signals emitted by M. zebra encode information related to the size of the emitter. The individual signature remains poorly defined. In order to understand the decoding process of information by receivers, I set up a paradigm allowing to show that territorial males increase their territorial activity and approach loudspeakers in response to playbacks. Playback experiments using signals with artificially modified acoustic parameters suggest a large tolerance for temporal variations. This thesis thus participates to the comprehension of the biological function of acoustic communication in a fish. It calls for further studies concerning the transmitted information and its encoding process
While female preferences may vary depending on population-level differences in density or sex ratio, factors affecting mate choice may act at the individual level, i.e., females may encounter males with varying frequency or encounter multiple males simultaneously. The “socially cued anticipatory plasticity” hypothesis suggests that females may bias mate preferences based on prior experience. In the wolf spider, Schizocosa ocreata, males typically mature before females, allowing females to experience male courtship before maturation. Using video playback, we simulated differences in the encounter rate and the number of males simultaneously encountered to examine effects on female preference for a secondary sexual character (foreleg tufts). Penultimate females were exposed to video playback of zero, one, or three courting males either once every 2 days (low encounter rate) or twice per day (high encounter rate). At adulthood (week 2 post-maturity), females were presented video playback of courting males with small or large tufts to test for preferences in no-choice and two-choice designs. In two-choice (but not no-choice) presentations, female receptivity varied significantly with treatment. Females exposed to three males simultaneously at a higher encounter rate during their penultimate stage exhibited greater receptivity to large-tufted than small-tufted males as adults. Subsequent analyses revealed that females were more selective as adults if they encountered cumulatively more males during their penultimate stage, which was a repeatable trend when re-testing some individuals 3 weeks later. This study adds to the growing literature that demonstrates that invertebrates exhibit plasticity in mating preferences depending on social experience.
Mate choice is an important evolutionary process influencing a vast array of traits and ecological processes. Although the study of mate choice has proved to be hugely popular, the number of ways in which mate choice can be described is complex and a bewildering array of terminology has developed. The author begins by summarizing some examples of the range of terms used to describe choice that expose this complexity. The author then shows how the information conveyed by different mate choice descriptors can be better understood by comparison to null expectations, that is, the expected variation in a trait when mate choice is not expressed. This comparison is important because many traits that might be affected by mate choice, such as mating rate, mate search effort, and responsiveness, also vary in non-choosy individuals. This is in contrast to other traits, such as the slope of a preference function and mate assessment effort, for which null expectations are predictable. By understanding the null expectation for a trait, its utility as a descriptor of mate choice can be gauged. From this basis, the author suggests an alternative approach to the description of mate choice based upon a principle of describing variation in both “what” is preferred and “by how much” it is preferred. Crucially, the author describes how this approach might apply to a wide range of preference function shapes, thus aiding comparisons across taxa. Finally, the author considers how an improved appreciation of the way mate choice is described can inform future research.
Background: Energy and time constraints experienced by dispersing animals often limit individual dispersal and subsequent habitat selection decisions. When substantial variation in individual dispersal capability is present, these constraints may have significant impacts on populations where condition-dependent evaluation of habitat sites interacts with state-dependent habitat selection. Latty and Reid (2010) hypothesize that internal state of the dispersers and characteristics of their habitat mediate habitat selection ("condition matching"). Hypothesis: Individual beetles in better energetic condition are more likely to attack better-defended trees (i.e. riskier habitat). Organism: Mountain pine beetle (Dendroctonus ponderosae Hopkins). Field sites: Two field sites were used, and work at both sites coincided with the start of the beetles’ emergence and flight period. Beetles used for lipid extraction analysis were collected near Merritt, BC, Canada in 2006, and host tree acceptance experiments were performed in 2010 near Field, BC, Canada. Methods: We sampled a population of beetles to characterize the relationship between beetle size and lipid content, then examined the variation in individual somatic energy condition and date of emergence. We separately tested the effect of somatic energetic condition on habitat (host) selection decisions by experimentally manipulating beetles’ somatic energy reserves, placing them on host trees of different nutritional qualities, and measuring the latency in beetles’ host tree acceptance. Results: Most beetles emerged early. Their somatic energy condition is higher at the start of the emergence period than near the end, although there is substantial individual variation in both timing and condition upon beetle emergence. Beetles’ host selection decisions are influenced by both host tree nutritional quality and individuals’ lipid reserves. Good nutritional quality trees are accepted sooner than poor nutritional quality trees. Individuals with lower energy reserves are less selective, accepting poorer quality host trees sooner than beetles with higher energy reserves.
Vítor Almada was undoubtedly one of the most learned, inspiring and charismatic biologists of his generation in Portugal. His intelligence, generosity and charm attracted many students and colleagues to his chosen field of fish behaviour, a topic a bit surprising in a person who was born blind. But his blindness was never a defining feature, rather an inconvenience that he surpassed elegantly, with the help of family, friends and technology. And when one talked to the man, sometimes it was unbelievable that he could not actually see whatever he was discussing. His love of nature was expressed in his detailed knowledge of animals and plants; although he was comfortable in a classroom, his office or the lab, he clearly felt much better on a beach, a mountain river bank or a forest. Vítor was an enthusiastic and contagious thinker, infinitely curious about evolution, a lover of good living, of savoury foods (hence his famously robust waistline…), of art, history, politics and lively conve ...
Reproductive success is determined by the presence and timing of encounter of mates. The latter depends on species-specific reproductive characteristics (e.g. initiation/duration of the mating window), season, and reproductive strategies (e.g. intensity of choosiness) that may potentially mitigate constraints imposed by mating windows. Despite their potentially crucial role for fitness and population dynamics, limited evidence exists about mating window initiation, duration and reproductive strategies. Here, we experimentally tested the mechanisms of initiation and the duration of the common lizard's Zootoca vivipara mating window, by manipulating the timing of mate encounter and analyzing its effect on (re-)mating probability. We furthermore tested treatment effects on female reproductive strategies, by measuring female choosiness. The timing of mate encounter and season did not significantly affect mating probability. However, a longer delay until mate encounter reduced female choosiness. Re-mating probability decreased with re-mating delay and was independent of mating delay. This indicates that mating window initiation depends on mate encounter, that its duration is fixed, and that plastic reproductive strategies exist. These findings contrast with previous beliefs and shows that mating windows per se may not necessarily constrain reproductive success, which is congruent with rapid range expansion and absence of positive density-effects on reproductive success (Allee effects). In summary, our results show that predicting the effect of mating windows on reproduction is complex and that experimental evidence is essential for evaluating their effect on reproduction and reproductive strategies, both being important determinants of population dynamics and the colonization of new habitats.
For humans, the act of hearing results in a set of experiences that can lead to knowledge, but may or may not lead to overt
behaviors. Ordinary experience suggests that most humans share these experiences and acquired knowledge, and thus share a
sense of hearing. However, hearing in other species can be inferred only from behaviors that may or may not reveal experience
and knowledge. If we are careful not to anthropomorphize, as many of us have been taught, our view of hearing in nonhuman
animals tends to be tied to the behaviors most easily observed and understood, such as predator avoidance, prey identification,
courtship, and vocal social interaction. Since experience and knowledge are impossible to observe directly, we may tend to
deny their existence in other species, particularly those with which we do not readily identify, and those that are most distantly
related to us. This makes it difficult for us to evaluate and understand the sense of hearing in other species in terms other
than naturally occurring, sound-related behaviors. We may be led to believe, for example, that hearing in a given species
or class can be fully explained as an adaptation for initiating and directing behaviors that occur in close temporal association
with those sound sources that seem to require a prompt response, that is, those thought to be of “biological significance.”
In this view, we are probably fated to regard the sense of hearing in these species as simplified or impoverished compared
with our own.
In the literature on dominance hierarchies, "winner" and "loser" effects usually are denned as an increased probability of winning at time T, bated on victories at time T-l, T-2, etc, and an increased probability of losing at time T, based on losing at T-l, T% etc, respectively. Despite some early theoretical work on winner and loser effects, these factors and how they affect the structure of dominance hierarchies have not been examined in detail. I developed a computer simulation to examine winner and loser effects when such effects are independent of one another (as well as when they interact) and when combatants assess each other's resource- holding power. When winner effects alone were important, a hierarchy in which all individuals held an unambiguous rank was found. When only loser effects were important, a dear alpha individual always emerged, but the rank of others in die group was often unclear because of die scarcity of aggressive interactions. Increasing winner effects for a given value of the loser effect increase the number of individuals with unambiguous positions in a hierarchy and die converse is true for increasing the value of die loser effect for a given winner effect Although winner and loser effects have been documented in a number of species, no study has documented both winner and loser effects (using some controlled, padrwise testing system) and die detailed nature of behavioral interactions when individuals are in groups. I hope die results of this model will spur such studies in die future. Key words: aggression, dominance hierarchies, resource-holding power, winner and loser effects. (Behav Ecol 8:583-587 (1997))
Fish sounds are often associated with agonistic and courtship behavior, and in many cases sounds are produced by males with sexually dimorphic sound‐producing mechanisms. This review focuses on the sounds and sexually dimorphic sonic neuromuscular system of the oyster toadfish Opsanus tau, compares it with findings on a related toadfish, the midshipman Porichthys notatus and finally reviews data on steroid levels and their effect on seasonal changes in mass of the sonic muscles and sound characteristics in the weakfish Cynoscion regalis. Highlights of the work on the oyster toadfish include the following. (1) Quantitative seasonal changes in the male boatwhistle mating call in a manner suggesting that steroids modulate the output of central nervous system pattern generators for fundamental frequency and duration. (2) Larger sonic muscles in males comprised of a greater number of smaller and therefore more energy efficient fibers than in females. Male muscles have greater activities of anaerobic and aerobic enzymes and enzyme activities and muscle size are increased by andro‐gens. (3) Neurons in the spinal sonic motor nucleus (SMN) are small in females and either small (S) or large (L) in males. The same three morphs are present in Porichthys, but there are major differences in somatic growth patterns, dendrite development and sonic abilities among morphs in the two species. Development of sexual dimorphism in the SMN suggests major differences between amniotic vertebrates (birds and mammals) and fishes, particularly with regard to perinatal critical periods and cell death. (4) As in other vertebrates, toadfish sonic centers in the central nervous system (including the supracommissural nucleus of the ventral telencephalon, nucleus preopticus parvocellularis anterior, the torus semicircularis and the inferior reticular nucleus) possess gonadal steroid‐concentrating neurons. Although endocrine investigation of sound production has been attempted in only three species, its relevance to important life history events of commercially‐important species and the availability of large numbers of basic biological questions suggest the field is ripe for further investigation.
Adult male copperheads (Agkistrodon contortrix) fight for priority of access to females during the mating periods in spring and late summer. During fights, one male abruptly quits and retreats, and the other chases in pursuit. One male thus emerges as the winner and the other as the loser. Reversal of this outcome does not occur during the time of observation (30 min) nor in 24 hr postfight trials. In all cases, winners gain priority of access to females. Losers, in contrast, do not pursue females nor gain access to them, even when winners are removed from the arena. In this study, courtship performance of male A. contortrix was studied in the laboratory using subjects with either winning or losing experience from staged fights. All males used first were tested with a single female to determine courtship performance prior to the agonistic trials. From these tests, each male was given a single courtship score of 0 (no courtship) to 3 (most intense courtship). Only males receiving a score of 2–3 were used in the initial agonistic trials. All staged fights were conducted in a large arena and involved two males and one female. Following fights, winners and losers were tested again for courtship performance. In trials conducted at 24 hr and 7 days postfight, only losers were tested. It was found that prefight courtship scores were not significantly different between winners and losers. At 30 min postfight, most losers showed complete suppression of courtship behavior (score 0). Winners, in contrast, showed equivalent or an increase in their courtship scores. At 24 hr postfight, courtship scores of losers remained significantly lower than their prefight scores. At 7 days postfight, courtship scores of losers were not significantly difference from their original prefight scores. Fighting behavior in free-ranging A. contortrix represents a potentially significant cost to losers if it is associated with loss of reproductive opportunities. Recent evidence from hormonal studies indicates that inhibition of courtship and fighting behavior in male A. contortrix is stress-induced. © 1996 Wiley-Liss, Inc.
This study imposed stress upon spawning cod Gadus morhua in the laboratory to evaluate the potential effects of trawl avoidance on their reproductive physiology and spawning behaviour. Plasma cortisol levels of stressed fish were significantly higher than controls. Stressed cod initiated fewer courtships and often performed an altered courtship sequence. Both control and stressed fish spawned and there was little difference in the production of eggs, fertilization rate, hatching success or time to starvation of larvae. However, stressed fish produced abnormal larvae more frequently. Cod exposed to a chronic stressor are able to spawn successfully, but there appears to be a negative impact of this stress on their reproductive output, particularly through the production of abnormal larvae.
Bird song, like many other male secondary sexual characters, may have evolved as intra- or inter-sexual signals of male phenotypic quality. The hypotheses that song rate and song features reflect androgen levels and body condition, qualities useful in male–male competition, and that they are also influenced by social context, was tested for the first time in the present correlational study. The relationships between song rate and 14 variables describing song structure, respectively, and absolute plasma testosterone levels, body mass, body condition, number of neighbouring males and distances between nest sites in male barn swallows,Hirundo rustica, were analysed. Song rate was not correlated with any of the song features nor with male or social context characteristics. By contrast, a harsh song syllable, the ‘rattle’, was positively related to plasma testosterone levels, and its peak amplitude frequency varied inversely with male body mass and condition. In addition, eight features of song varied according to the social environment of each male. In particular, males sang longer and more varied songs when they had few or no neighbours, whereas males in highly competitive contexts uttered short songs, interrupted them more frequently, and emphasized the rattle. Neighbouring males also sang more similar songs than distant males, and this resulted in matched countersinging. The quality of song output therefore reflects aspects of male competitive potential, and relationships between song structure and social context suggest that some features, such as the rattle, might have originally evolved to serve in male–male interactions; a female preference may have further promoted song evolution leading to complex syllable repertoires.
Adult males of the small arboreal iguanid lizard, Anolis carolinensis, will fight and form social dominance hierarchies when placed in habitats with limited resources. The relationships between time since initial aggressive interaction, relative social dominance, reproductive activity, and corticosterone and androgen levels were determined for 34 pairs of lizards. A discriminant analysis established a “dominance index” which indicated that over 90% of the difference between individuals who had won or lost aggressive interactions (putative social dominants and subordinates) was attributable to a single discriminant function reflecting altered body color, perch site selection, and circulating androgen. Animals that had darker body color also selected lower perch sites and had depressed rates of courtship relative to winners of fights and were thus designated as social subordinates. These animals also had levels of circulating androgen significantly lower than that of dominants, but circulating corticosterone was not significantly affected. Winners of fights showed a dramatic surge in circulating androgen at 1 hr but returned to near control values by 1 week; losers, however, showed depressed circulating androgen levels at 1 week.
In Experiment 1, when previously isolated male mice were paired and given a female, they fought before beginning to mount, and the more aggressive male ejaculated somewhat more frequently. Males housed together for several days showed little aggression when jointly given a female, but those that were more aggressive in the home cage clearly ejaculated more frequently. In Experiment 2, males were paired for 4 days after a period of isolation. More aggressive males showed more ejaculations when subsequently tested individually with females, but not when pair members conjointly encountered females. In Experiment 3, males were paired for several weeks before encountering females. In cases in which home cage dominance was constant, the more aggressive males ejaculated more frequently both when tested individually and when tested as pairs.
We present the first analysis of scaling effects on the motor pattern of a feeding vertebrate. Data are presented for the effects of body size on the pattern of activity in four head muscles during prey capture in the largemouth bass, Micropterus salmoides. Electromyographic (EMG) recordings were made from three expansive-phase muscles (the epaxialis, the sternohyoideus and the levator arcus palatini) and one compressive-phase muscle (the adductor mandibulae), during the capture of small fish prey. Recordings were made of 181 prey-capture events from 19 bass that ranged in size from 83 to 289 mm standard length. We measured seven variables from the myogram of each capture to quantify the temporal pattern of muscle activation, including the duration of activity in each muscle and the onset time of each muscle, relative to the onset of the sternohyoideus muscle. Regressions of the mean value of each variable for the 19 individuals on standard length revealed that only the onset time of the adductor mandibulae changed with fish body size. The increase in onset time of the adductor muscle appears to reflect the longer time taken to open the mouth fully in larger fish. Other research shows that the kinematics of the strike in this species slows significantly with increasing body size. The combined results indicate that the duration of the EMG signal is not directly correlated with the duration of force production in muscles when compared between fish of different sizes. The lack of scaling of burst duration variables suggests that the reduced speeds of prey-capture motion are explained not by changes in the envelope of muscle activity, but rather by the effects of scale on muscle contractile kinetics. These scaling effects may include changes in the relative resistance of the jaw and head structures to movement through water and changes in the intrinsic contractile properties of the muscles of the feeding apparatus.
An important question in state-dependent behaviour is how multiple influences on state are integrated to determine current behaviour. Aggressive behaviour is known to be affected by a prior contest experience. Nevertheless, whether and how multiple prior fighting experiences are integrated into a fighting decision remain unexplored. In this study, individuals of Rivulus marmoratus (Cyprinodontidae), a hermaphroditic fish, were given different combinations of two prior fighting experiences to investigate: (1) the effect of penultimate experiences on the probability of winning a subsequent contest; (2) the relative effect of a recent win and loss; and (3) whether the effect of a winning experience was as short lived as observed in other species. Penultimate and recent fighting experiences were given to the test fish approximately 48 and 24 h prior to the dyadic contests, respectively. From the results of the five types of contests staged, we conclude that: (1) penultimate fighting experiences had a significant effect on the probability of winning a subsequent contest; (2) a more recent experience had a more pronounced effect than an earlier experience, which suggested that the effect of a fighting experience would decay and/or the effect of a recent experience would interfere with the effect of an earlier experience; (3) no asymmetric effect between a winning experience and a losing experience was detected; and (4) the effect of both a winning and a losing experience lasted for at least 48 h in R. marmoratus which was the maximum time tested in these experiments. The possible reasons for the differences in results among studies of experience effects on contest outcomes are discussed. Copyright 1999 The Association for the Study of Animal Behaviour.
We report changes in brain serotonergic, noradrenergic and dopaminergic activity, along with plasma cortisol concentrations, occurring during the initial 24-h period following the establishment of dominant-subordinate relationships in pairs of rainbow trout. Immediately (within 5 min) after the termination of staged fights for social dominance, a large increase in blood plasma cortisol was observed in both fight losers (future subordinate fish) and winners (future dominant fish). In dominant fish, cortisol decreased rapidly (within 3 h) to the level of unstressed controls, while continuing to increase in subordinate fish. At 3 h following fights, the brain serotonergic system was activated in both dominant fish and subordinate fish, at least in some brain regions (telencephalon). This effect was reversed in dominant individuals within 24 h of social interaction, whereas in subordinate fish a substantial activation of the serotonergic system was manifest in all brain regions by 24 h. Similarly, a strong increase in brain catecholaminergic activation was indicated after 24 h of social interaction in subordinate fish, but not in dominant fish. Relationships between plasma cortisol and brain serotonergic and noradrenergic activity in the various experimental groups suggest that these systems influence cortisol secretion under normal conditions and during moderate or short-term stress.
To categorize variation in disturbance calls of the weakfish Cynoscion regalis and to understand their generation, we recorded sounds produced by different-sized fish, and by similar-sized fish at different temperatures, as well as muscle electromyograms. Single, simultaneous twitches of the bilateral sonic muscles produce a single sound pulse consisting of a two- to three-cycle acoustic waveform. Typical disturbance calls at 18 degrees C consist of trains of 2-15 pulses with a sound pressure level (SPL) of 74 dB re 20 microPa at 10 cm, a peak frequency of 540 Hz, a repetition rate of 20 Hz and a pulse duration of 3.5 ms. The pulse duration suggests an incredibly short twitch time. Sound pressure level (SPL) and pulse duration increase and dominant frequency decreases in larger fish, whereas SPL, repetition rate and dominant frequency increase and pulse duration decreases with increasing temperature. The dominant frequency is inversely related to pulse duration and appears to be determined by the duration of muscle contraction. We suggest that the lower dominant frequency of larger fish is caused by a longer pulse (=longer muscle twitch) and not by the lower resonant frequency of a larger swimbladder.
During the mating seasons (late summer and spring), male copperheads (Agkistrodon contortrix; Serpentes, Viperidae) engage in aggressive physical interactions for priority of access to females. These fights generally involve two individuals and are characterized by prominent vertical displays, a high degree of physical contact, and the absence of biting. Ritualized aggression does not occur in females. Although intrasexual aggression in conspecifics has obvious energetic costs (e.g., lactate accumulation) that can affect subsequent behavior, few studies have addressed these costs in reptiles, and no studies have examined snakes. Moreover, recent studies suggest psychoneuroendocrine (catecholamines, glucocorticoids) regulation of metabolism during and following aggressive episodes. There were three main questions addressed in this study. Do winners and losers of staged, pair-wise encounters show differences in post-fight (60-min) levels of plasma lactate and corticosterone (CORT)? Are levels of plasma lactate correlated with levels of plasma CORT? Is fight duration correlated with levels of plasma lactate and CORT? Two different control groups (cage and arena) were used. Body length, body mass, duration of fighting, and season of testing were not correlated with levels of plasma lactate and CORT. At 60-min post-fight, losers had significantly higher levels of mean plasma lactate and CORT when compared to levels in winners and controls, and there were no significant differences between winners and controls. From our results, we suggest the following conclusions. First, elevated levels of CORT in losers, but not winners, result from psychoneuroendocrine factors rather than simple exercise. Second, elevated levels of CORT in losers retard metabolic recovery resulting in higher lactate levels in losers, whereas winners return to pre-fight levels within 60-min post-fight. Last, the CORT response has a net negative effect on metabolic recovery and may be implicated in the protracted suppression of aggressive behavior in losers.
Although sound-producing (sonic) muscles attached to fish swimbladders are the fastest known vertebrate muscles, the functional requirement for such extreme speed has never been addressed. We measured movement of the swimbladder caused by sonic muscle stimulation in the oyster toadfish Opsanus tau and related it to major features of the sound waveform. The movement pattern is complex and produces sound inefficiently because the sides and bottom of the bladder move in opposite in and out directions, and both movement and sound decay rapidly. Sound amplitude is related to speed of swimbladder movement, and slow movements do not produce perceptible sound. Peak sound amplitude overlaps fundamental frequencies of the male's mating call because of muscle mechanics and not the natural frequency of the bladder. These findings suggest that rapid muscle speed evolved to generate sound from an inefficient highly damped system.
Owing to its high degree of complexity and plasticity, the cichlid pharyngeal jaw apparatus has often been described as a key evolutionary innovation. The majority of studies investigating pharyngeal muscle behavior and function have done so in the context of feeding. Analysis of enzyme activities (citrate synthase, 3-hydroxyacyl-CoA dehydrogenase and L-lactate dehydrogenase) of pharyngeal muscles in the Lake Malawi cichlid Tramitichromis intermedius revealed differences between pharyngeal jaw muscles and between males and females. Therefore, these muscles have different performance characteristics, resulting in different functional characteristics of the muscles within the complex. Furthermore, the differences between muscles of males and females represent fundamental differences in muscular metabolic processes between sexes. This study is the first to demonstrate that the pharyngeal anatomy is not only used for food processing but is possibly responsible for sound production, in turn influencing sexual selection in cichlid fish.
After a period of social isolation all-male groups of O. mossambicus were observed for 5 days after which ovulated females were added. The frequency of different types of social interactions and behavioural activities along the observation period were recorded, and their patterns of temporal variation were studied. The relationships among the different variables were analysed using PCA. During the process of group formation the following regular temporal sequence of predominant activities was detected: (a) mutual assessment and hierarchy formation; (b) territorial establishment and nest digging; (c) courtship. We suggest that these results reflect the probable sequence of events during the process of lek formation in nature at the onset of each breeding period.
Data are presented on the breeding behaviour of Oreochromis mossambicus under captive conditions. Males tended to synchronize their occupation of territories and breeding activities. Different mate mating tactics were observed, namely establishing a breeding territory, acting as a floater, or behaving as a sneaker. The majority of spawnings observed involved dominant males and were subjected to interference from other males. Males were found to court other males that frequently responded to these attempts by adopting a female-like behaviour. Results are discussed in terms of a probable time constraint in territoriality, which promotes male-male competition and a low level of sex discrimination by territorial fish.
The scores of three aggression parameters in a standard-opponent test correlated significantly with individual androgen concentrations measured in tissue as well as in blood samples taken immediately after the test (bites: r = +.62/+.82, threats: r = + 0.75/+.70, latency: r = −.66/−.53). If the test was performed after 28 days of social isolation no correlations were found. There were also no correlations between behavioural measures and corticoids.
Evidence is provided that the ''chirp,'' a sound commonly produced by males of the bicolor damselfish (family: Pomacentridae) possesses an anatomical constraint: The peak frequency within its power spectrum reflects a clear inverse relationship to body size. For every 1-mm change in the standard length of a male (range: 50-69 mm), the peak frequency of its sounds shifts by approximately 20 Hz. The ultimate constraint appears to be the volume of an individual's gas bladder. This provides an individualistic feature to the sounds of different sized colony members, all of whose sounds possess an otherwise extremely stereotyped temporal pattern of their included pulses. This finding may aid in clarifying the mechanism that provides the clue for the already established acoustical recognition of individuals within colonies of the species.
An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1–7 m deep. Adult fishes (over 8 cm standard length) are usually absent from water deeper than 12m and shallower than 0–5 m, whereas juveniles may occur at all depths, and fry only in very shallow water.
T. mossambica inhabits the littoral and sublittoral in the warm and transition periods (August–April) but moves into deep water in the cool season (May–July). Exposed and sheltered areas are utilized for different purposes by adult fishes, the former for nesting, and latter for feeding and mouth–brooding. Habitat selection by males is governed by the availability of suitable nest sites. Nests are most common in sparsely–vegetated sheltered areas. Brooding females preferred sheltered littoral areas but ventured onto the terrace to release the fry. Juveniles and fry inhabited exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour is described. The biology of T. mossambica in Lake Sibaya is compared to data on the same, and similar species, in other systems. The utilization of available resources in the lake by T. mossambica is discussed and reference is made to the importance of the retention of generalized characters for the successful habitation of the cyclically–renewed habitat of the littoral.
Data are presented on the breeding behaviour of Oreochromis mossambicus under captive conditions. Males tended to synchronize their occupation of territories and breeding activities. Different male mating tactics were observed, namely establishing a breeding territory, acting as a floater, or behaving as a sneaker. The majority of spawnings observed involved dominant males and were subjected to interference from other males. Males were found to court other males that frequently responded to these attempts by adopting a female-like behaviour. Results are discussed in terms of a probable time constraint in territoriality, which promotes male-male competition and a low level of sex discrimination by territorial fish.
The role of sound production of the Mozambique tilapia Oreochromis mossambicus in agonistic and mating interactions observed during hierarchy formation and in established groups was examined. Only territorial males produced sounds, during male–female and male–male courtship interactions and during pit-related activities (e.g. dig, hover and still in the nest). Sound production rate was positively correlated with courting rate. Although sounds in other cichlids are typically emitted in early stages of courtship, O. mossambicus produced sounds in all phases, but especially during late stages of courtship, including spawning. It is suggested that the acoustic emissions in this species may play a role in advertising the presence and spawning readiness of males and in synchronizing gamete release.
Dominance hierarchy was determined in 5 groups of juvenile Arctic charr (Salvelinus alpinus), each group consisting of 4 fish. Telencephalon and brain stem (remaining parts of the brain) were analyzed with regard to their content of monoamines and monoamine metabolites. No significant differences were observed in the concentrations of norepinephrine (NE), dopamine (DA), or serotonin (5-hydroxytryptamine, 5-HT) between fish with different social rank. However, the concentration of 5-hydroxyindoleacetic acid (5-HIAA), the principle metabolite of 5-HT, was significantly higher in subordinate fish, and a significant inverse linear correlation was found between 5-HIAA concentration and social rank (as measured by dominance index) in the brain stem. In the telencephalon the dominant fish had a significantly higher level of homovanillic acid (HVA), a major DA metabolite. These findings indicate a greater serotonergic activity, possibly associated with increased stress, as well as a lower dopaminergic activity, possibly associated with reduced aggression, in subordinate charr. The differences between dominant and subordinate fish could either be caused by social interactions or reflect innate individual differences in monoamine utilization, predisposing individuals for dominant or subordinate positions in the dominance hierarchy.
Abstract. Considerable evidence across many taxa demonstrates that prior social experience affects the outcome of subsequent aggressive interactions. Although the 'loser effect', in which an individual losing one encounter is likely to lose the next, is relatively well understood, studies of the 'winner effect', in which winning one encounter increases the probability of winning the next, have produced mixed results. Earlier studies differ concerning whether a winner effect exists, and if it does, how long it lasts. The variation in results, however, may arise from different inter-contest intervals and procedures for selecting contestants employed across previous studies. These methodological differences are addressed through a series of experiments using randomly selected winners and three different inter-contest intervals in the pumpkinseed sunfish, Lepomis gibbosus. The results indicate that a winner effect does in fact exist in pumpkinseed sunfish, but that it only lasts between 15 and 60 min. Based on these results, predictions about the behavioural dynamics of hierarchy formation are discussed, and it is suggested that it may be impossible, in principle, to predict the outcome of dominance interactions between some individuals before they are actually assembled to form a group. Finally, the possible mechanisms underlying the winner effect are explored.
Thesis (M.A. in Zoology)--University of California, Berkeley, June 1961. Includes bibliographical references (leaves 123-124).
In the protogynous stoplight parrotfish (Sparisoma viride), large males defend territories that encompass the home-ranges of several mature females. However, high-quality habitat is in short supply, such that smaller, competitively inferior males do not defend territories. We investigated the role of 11-ketotestosterone (11KT) and testosterone (T) in the regulation of territorial behavior in a wild population of a protogynous reef fish, the stoplight parrotfish, at Glover's Reef, Belize. Radioimmunoassay of plasma samples from individuals of known social status revealed that nonterritorial males have lower levels of T and 11KT than territorial males. Nonterritorial males allowed access to vacant territories underwent pronounced increases in T and 11KT. When sampled 1 week after territory acquisition, levels of T and 11KT in new territorial males were significantly higher than the levels in established territorial males, but by 3 weeks after territory acquisition, there was no significant difference. We further investigated the hypothesis that such short-term increases in androgen levels are a response to intense male-male interactions during territory establishment. Simulated territorial intrusion promoted increased plasma levels of both T and 11KT while access to vacant territories without neighboring territorial males did not. These findings suggest that the endocrine system plays a role in fine-tuning the levels of territorial aggression exhibited by male stoplight parrotfish. We discuss these results in light of recent theory in behavioral endocrinology.
Aggression consumes important amounts of energy (e.g., in fish the effort of "routine" social life may be as costly as life-long forced swimming at moderate speeds). In fish the amount of energy spent and the metabolic compartment mobilized seem to depend on the length of cohabitation, the number of contestants and the result of the fight. In mammals, metabolic preparations for fights were shown. The fights cause elevations of both body temperature and metabolic rate, as well as important changes in carbohydrate and lipid metabolism. There are evidences which show that the energetic aspects of aggressive behavior have a significant impact on the behavioral tactics and survival chances in free living animals. The relevance of these studies to game theoretical analyses and to practical aspects of the aggression-energy metabolism interrelationship are also outlined. Although many details of the phenomenon are known, important issues have to be clarified, among them the possible neuroendocrinologic co-regulation of this behavior and of its energetic background.
The relationship between urinary concentrations (free + sulfates + glucuronides) of the steroids testosterone (T), 11-ketotestosterone (11KT), 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17, 20 beta-P) and 17 alpha, 20 alpha-dihydroxy-4-pregnen-3-one (17, 20 alpha-P), and the social behavior of males of the cichlid fish Oreochromis mossambicus was investigated. After 8 days of isolation none of the steroids were good predictors of social dominance developed after subsequent formation of all-male groups. One day after group formation dominance indexes were good predictors of the urine concentrations of all sex steroids. Dominance indexes and androgen concentrations measured after all-male group formation were positively correlated with territoriality, courtship rate, and nest size. Similar relationships were found for progestins with the exception that they were not correlated with courtship rate. All-male group formation was also accompanied by an increase in urinary sex steroid concentrations in fish that became territorial and a decrease in non-territorial fish with the exception of T, which increased in both groups. Addition of ovulating females caused steroid concentrations to return to levels near isolation, except for 17, 20 alpha-P in territorials, which underwent a large increase. Thus, social interactions may have an important modulatory effect on sex steroid concentrations in O. mossambicus.
Evidence for the presence of a serotonin1A (5-HT1A) receptor subtype in the salmonid fish brain has recently been presented. In the present study the potent 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) was tested for its effect on plasma cortisol concentrations in rainbow trout (Oncorhynchus mykiss). Blood was sampled and 8-OH-DPAT administered through a catheter in the dorsal aorta. Thirty minutes after the injection of 40 microg of 8-OH-DPAT/kg, plasma cortisol levels had increased from 12 to 149 ng/ml, whereupon they fell, reaching baseline levels after 4 h. The effect of 1-40 microg 8-OH-DPAT/kg on plasma cortisol concentrations was dose-dependent. The results lends further support to the hypothesis that the brain serotonergic system plays a key role in integrating autonomic, behavioral and neuroendocrine stress-responses in fish as well as mammals, suggesting that not only the structural and biochemical organization, but also the function of the serotonergic system has been conserved during vertebrate evolution.
While much is known about the functional significance of strategic decisions in animal fighting, relatively little is understood about the mechanisms that underlie the making of those decisions. In mechanistic terms, strategic decisions, such as either escalating a fight or giving up, are made in relation to the proximate costs that opponents inflict (or can potentially inflict) upon one another. These costs include physical injury and also the physiological consequences of engaging in an energetically demanding activity. We studied the role of injury and energy metabolism during fights between male cichlid fish, Tilapia zillii. In relation to injuries incurred during fights, scale loss differed depending on whether the winner was smaller or larger than its opponent; smaller winners inflicted significantly more damage on their opponents than they received, whereas this difference was not apparent in those fights won by the larger fish. In relation to energy metabolism, escalated fighting resulted in a significant depletion of total sugar reserves in the muscle and the liver. It appears that the muscle energy reserves are respired anaerobically, as was evident from the accumulation of lactate in the muscle. Losers had significantly higher levels of muscle lactate than winners. Together, the injury data and the metabolic data suggest that escalated fighting is costly for both winners and losers, but especially so for losers. These data are discussed in relation to models of animal decision making and we conclude that the difference between opponents in the proximate costs incurred during fighting is likely to underlie the making of decisions such as continuing, giving up or escalating the fight. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.
The midshipman fish, Porichthys notatus, generates acoustic signals for intraspecific communication. Nesting males produce long-duration "hums" which attract gravid females and can be effectively mimicked by pure tones. In this study we examine the encoding of tonal signals by the midshipman peripheral auditory system. Single-unit recordings were made from afferents innervating the sacculus while presenting sounds via an underwater loudspeaker. Units were characterized by iso-intensity spike rate and vector strength of synchronization curves, as well as by peristimulus time histograms. Additionally, response-intensity curves and responses to long-duration (up to 10 s) stimuli were obtained. As has been seen in other teleosts, afferents had highly variable activity profiles. Excitatory frequencies ranged from 60 to over 300 Hz with most units responding best around 70 or 140 Hz. Thresholds at 90 Hz ranged from 95 to 145 dB re 1 microPa. Strong synchronization provided a robust temporal code of frequency, comparable to that described for goldfish. Spike rate showed varying degrees of adaptation but high rates were generally maintained even for 10-s stimuli. The midshipman peripheral auditory system is well suited to encoding conspecific communication signals, but nonetheless shares many response patterns with the auditory system of other teleosts.
Courtship behavior in frogs is an ideal model for investigating the relationships among social experience, gonadal steroids, and behavior. Reception of mating calls causes an increase in androgen levels in listening males, and calling, in turn, depends on the presence of androgens. However, previous studies found that androgen replacement does not always restore calling to intact levels, and the relationship between androgens and calling may be context dependent. We examined the influence of androgens on calling behavior in the presence and the absence of social signals in male green treefrogs (Hyla cinerea). We categorized calling during an acoustic stimulus (mating chorus or tones) as evoked and calling in the absence of a stimulus as spontaneous. Intact males received a cholesterol implant, castrated males were castrated and received a cholesterol implant, and T-implanted males were castrated and received a testosterone implant. The androgen levels (mean +/- SE ng/ml of plasma) achieved by the implants were as follows: castrated males, 1.2 +/- 0.2; intact males 21.9 +/- 7.0; T-implanted males, 254.6 +/- 39.5. As in other frogs, calling depends on the presence of androgens, as castration abolished and T replacement maintained calling. However, among intact and T-implanted males, the influence of androgens on calling differed between spontaneous and evoked calling. There was a positive effect of androgen treatment on spontaneous call rate and a positive correlation between spontaneous call rate and androgen levels. The influence of androgen levels on evoked call rate was more complex and interacted with acoustic treatment. Surprisingly, T implants suppressed the chorus-specific increase in calling that is evident in intact males. In addition, in response to the chorus, T-implanted males called less than did intact males, in spite of higher androgen levels. Furthermore, variation in androgens did not explain variation in evoked call rate. These data indicate that androgens influence the motivation to call, but that, when socially stimulated, androgens are necessary but insufficient for calling.
Effects of stress of reproduction and growth in fish
- N W Pankhurst
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- G Kraak
Pankhurst, N. W. & Van Der Kraak, G. 1997. Effects of stress of reproduction and growth in fish. In: Fish Stress and Health in Aquaculture (Ed. by G. K. Iwama, A. D. Pickering, J. P. Sumpter & C. B. Schreck), pp. 73–93.
Etologia social e endocronologia comporta-mental da tilá Oreochromis mossambicus
- R F Oliveira
Oliveira, R. F. 1995. Etologia social e endocronologia comporta-mental da tilá Oreochromis mossambicus (Teleostei, Cichlidae).
- F Huntingford
- A Turner
Huntingford, F. & Turner, A. 1987. Animal Conflict. London:
Chapman & Hall.
Effects of stress of reproduction and growth in fish In: Fish Stress and Health in Aquaculture
- N W Pankhurst
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Pankhurst, N. W. & Van Der Kraak, G. 1997. Effects of stress of
reproduction and growth in fish. In: Fish Stress and Health in
Aquaculture
(Ed. by G. K. Iwama, A. D. Pickering, J. P.
Neuroendocrinology of the stress-response
- Sapolsky
Effects of stress of reproduction and growth in fish
- Pankhurst
Etologia social e endocronologia comportamental da tilápia Oreochromis mossambicus (Teleostei, Cichlidae)
- R F Oliveira
Depletion of energy reserves during reproductive aggression in male three-spined stickleback, Gasterosteous aculeatus L.
- Chellapa