Article

Different or alike? Female rainbow kribs choose males of similar consistency and dissimilar level of boldness

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Although the existence of consistent between-individual differences in behaviour (‘personality differences’) has been well documented during the last decade, the adaptive value of such behavioural limitations remains an open field for researchers of animal behaviour. Personalities clearly restrict individuals in their ability to adjust their behaviour to different conditions. However, sheer costs of flexibility cannot explain the polymorphism created by personality variation. In a correlative approach, we here tested whether mate choice might act as a major driving force maintaining personality variation in the monogamous, biparental rainbow krib, Pelvicachromis pulcher. We personality-typed all males and females for their boldness (activity under simulated predation risk) and allowed females to choose between two males that differed in their boldness (behavioural level and consistency). Prior to the choice, females were allowed to observe both males, expressing their natural boldness towards a video-animated natural predator. Both sexes showed personality differences in boldness over the short and long term. Furthermore, when removing side-biased females, we found a disassortative mating preference for the behavioural level and an assortative preference for behavioural consistency in boldness. These preference patterns might facilitate effective parental role allocation during offspring care and/or provide genetic benefits. Our results suggest that sexual selection plays an important role in the evolution of personality differences.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... However, it has not been widely accepted that female choice simply acting on male sexual ornaments (Andersson and Simmons, 2006). Personality is also subjected to sexual selection pressures (Scherer et al., 2017;Collins et al., 2019). Animal personality is the manifestation of behavioral traits consistent over time (Sih et al., 2004;Reale et al., 2007) and can be characterized by aggression, exploration, boldness, and fear (Gosling, 2001;Dall et al., 2004;Sih et al., 2004). ...
... Mate choice of females is closely related with their own personalities (Scherer et al., 2017;Laubu et al., 2016Laubu et al., , 2017Schuett et al., 2010). The preference for males with dissimilar personality types may promote genetic compatibility between mates, which will facilitate the production of heterozygous offspring (Tregenza and Wedell, 2000). ...
... A study of the convict cichlid (Amatitlania siquia) found that partners increased behavioral similarity after pairing (Laubu et al., 2016). Other studies have reported that behavioral convergence increased the success of assortative pairing (Laubu et al., 2016;Both et al., 2005), which makes it more difficult to clarify whether mate choice is influenced by personality or behavioral convergence (Scherer et al., 2017;Laubu et al., 2016). Thus, it is necessary to distinguish the personality of all individuals by exploration at the beginning of this study. ...
Article
A major challenge in behaviour and evolutionary ecology is to understand the evolution and maintenance of animal personality. Theory suggests that females can benefit by choosing a high-quality mate, but largely ignores the potential interaction between male and female personality during mate choice. Here, we examined the influence of exploration on mate choice by captive female Java sparrows (Lonchura oryzivora). Females preferred high exploratory males as mates rather than choosing mates according to their own exploration, and thus showed no assortative mating. Our results highlight the role of exploration of males in the mate preference of birds and suggest that mate compatibility plays minor role in the mate preference.
... Therefore, it seems likely that sexual selection may play a key role in shaping stable personality variation within populations (Schuett et al. 2010). Indeed, previous studies showed that personality traits, such as boldness (Godin and Dugatkin 1996;Scherer et al. 2017b), aggression (Ophir and Galef 2003;Kralj-Fišer et al. 2013) and exploratory behaviour (Schuett et al. 2011b;Pogány et al. 2018), affect mate choice in several species. ...
... The few empirical data collected so far differ regarding their direction of effects found. That is, previous studies on mate choice for aggressiveness and boldness have revealed either directional (Scherer et al. 2018a), assortative (Kralj-Fišer et al. 2013;Pogány et al. 2018), dis-assortative (Scherer et al. 2017b) or no effects (Laubu et al. 2017;Scherer and Schuett 2018) of individual behavioural types on mating preferences. Moreover, existing studies have often focused on potential effects of the behavioural level of a given personality trait on female mating preferences while neglecting the importance of individual differences in the consistency of its expression (but see Scherer et al. 2017bScherer et al. , 2018a. ...
... That is, previous studies on mate choice for aggressiveness and boldness have revealed either directional (Scherer et al. 2018a), assortative (Kralj-Fišer et al. 2013;Pogány et al. 2018), dis-assortative (Scherer et al. 2017b) or no effects (Laubu et al. 2017;Scherer and Schuett 2018) of individual behavioural types on mating preferences. Moreover, existing studies have often focused on potential effects of the behavioural level of a given personality trait on female mating preferences while neglecting the importance of individual differences in the consistency of its expression (but see Scherer et al. 2017bScherer et al. , 2018a. Additionally, most previous studies on the potential role of individual personality on mate choice are correlative in nature (but see Schuett et al. 2011b). ...
Full-text available
Article
Consistent between-individual differences in behaviour, known as personality differences, are heritable and have consequences for individual survival and reproductive success. Therefore, it is likely that personality differences are not just under natural but also under sexual selection. Indeed, the recently developed idea that individuals choose their mate based on its personality finds empirical support. However, most studies on mate choice based on personality traits are correlative pioneering work and there is a paucity of experimental studies that test for causality by disentangling personality measures from other, potentially correlated traits that may be important during mate choice. Here, we tested female preference for the apparent level and consistency of either male aggression (measured as mean distance of approach towards an animated opponent, manipulated by locating males at a fixed distance) or male boldness (measured as activity under a simulated predation threat, manipulated using a gradient in ambient water temperature) in a bi-parental West African cichlid, Pelvicachromis pulcher. Females could observe the apparent behaviour of paired stimulus males and were allowed to choose between the two stimulus males in a subsequent choice test. We found no direct effect of male apparent aggression/boldness on female choice, but an indirect effect such that female preference for the apparently bold male increased with increasing within-male pair contrast in their apparent level of boldness. Our results indicate females consider male boldness per se during mate choice, suggesting male boldness is sexually selected in our study species. Significance statement Ever since Darwin introduced the concept of sexual selection, female choice has been studied extensively. However, the hypothesis that consistent between-individual differences in behaviour (known as personality differences) affect mate choice is relatively new. Correlative studies support this idea but provide only suggestive evidence. Here, we used behavioural manipulations in order to disentangle male behaviour from other, potentially correlated male traits, allowing us to test for causality between female choice and personality differences in male aggression and boldness (both in level and consistency of behaviour) in a bi-parental cichlid. We found no overall female preference for male apparent behaviour, but female preference for the bold-appearing male increased with increasing between-male contrast in apparent boldness. Our results indicate a causal link between female choice and male boldness. In future, behavioural manipulations using a temperature gradient could provide further valuable insights.
... While some studies suggest the existence of a directional preference for risk-taking mating partners, others reported contrasting patterns in that risk-taking females preferred risk-taking males and vice versa, leading to assortative mating (Jiang et al. 2013). Assortative mating can affect individuals' reproductive success (Both et al. 2005;Kralj-Fišer et al. 2013;Scherer et al. 2017). For instance, guppy females that were paired with males showing similar risk-taking tendencies had a higher parturition success than females that were paired disassortatively (Ariyomo and Watt 2013). ...
... Shown are the mean (± SE) times focal individuals (a females, b males) spent associating with risk-taking and risk-averse stimulus individuals of the opposite sex Fig. 3 Scattergrams showing the correlation between focal individuals' own risk-taking scores and their strength of preference (SOP) for risktaking mating partners (testing for assortative mate choice). Females (a) but not males (b) showed a pattern where the choosing individual's risk-taking tendency predicted variation in SOP values, and risk-taking females showed stronger preferences for risk-taking stimulus males (post hoc Pearson correlations) be dependent on the choosing individuals' own tendency to take risks (assortative mate choice; Scherer et al. 2017). We found a pattern in which both preference functions appear to interact: female (but not male) P. mexicana generally preferred risk-taking over risk-averse mating partners, but the strength of preference (SOP) for risk-taking males was dependent on the choosing females' own personality type (i.e., risk-taking females exhibited stronger preferences for risk-taking males than risk-averse females). ...
... Why did risk-taking females show a stronger preference for risk-taking males than risk-averse ones? One possible explanation would be that a trade-off between benefits of mating with risk-taking males and reproductive benefits of assortative mating (Ariyomo and Watt 2013;Both et al. 2005;Kralj-Fišer et al. 2013;Scherer et al. 2017) explains females' mate choice. Clearly, more research is needed to investigate the underlying mechanisms and potential reproductive benefits of assortative mating in species without parental care, such as poeciliids. ...
Article
Variation in risk-taking versus risk-averse behaviour can become a target of natural and/or sexual selection. However, the link between animal personality and mate choice—as a major component of sexual selection—remains understudied. We asked (1) whether females and males of the livebearing fish Poecilia mexicana prefer risk-taking mating partners (directional mating preference), (2) or if their preferences are dependent on the choosing individual’s own personality type (assortative mating). We characterized each individual for its risk-taking behaviour, assessed as time to emerge from shelter and enter an unknown area. In dichotomous association preference tests, we offered two potential mating partners that differed in risk-taking behaviour but were matched for other phenotypic traits (body size, shape, and colouration). Females, but not males, exhibited a strong directional preference for risk-taking over risk-averse mating partners. At the same time, the strength of females’ preferences correlated positively with their own risk-taking scores. Our study is the first to demonstrate that an overall preference for risk-taking mating partners does not preclude effects of choosing individuals’ own personality type on (subtle) individual variation in mating preferences. More generally, two different preferences functions appear to interact to determine the outcome of individual mate choice decisions.
... livebearing fish Poecilia mexicana, we investigated whether a directional mating preference 253 for risk-taking mating partners provides those individuals with a reproductive advantage 254 (Godin & Dugatkin, 1996;Kortet, Niemelä, Vainikka & Laakso, 2019) and/or if the strength 255 of preference for risk-taking individuals would be dependent on the choosing individuals' 256 own tendency to take risks (assortative mate choice; Scherer, Kuhnhardt & Schuett, 2017). 257 ...
... Why did risk-taking females show a stronger preference for risk-taking males than 287 risk-averse ones? One possible explanation would be that a trade-off between benefits of 288 mating with risk-taking males and reproductive benefits of assortative mating (Ariyomo & 289 Watt, 2013;Both, Dingemanse, Drent & Tinbergen, 2005;Kralj-Fišer, Sanguino Mostajo, 290 Preik, Pekár & Schneider, 2013;Scherer, Kuhnhardt & Schuett, 2017) explains females' mate 291 choice. Moreover, risk-taking males tend to be more aggressive (Sih, Bell & Johnson, 2004) 292 and risk-taking females could be more willing to accept the risk of interacting with aggressive 293 males than risk-averse females. ...
... Overall then, while mate choice based on directional preferences (Godin & Dugatkin 314 1996;Kortet, Niemelä, Vainikka & Laakso 2012;Reaney & Backwell) and assortative mate 315 choice (Ariyomo & Watt, 2013;Both, Dingemanse, Drent & Tinbergen, 2005;Kralj-Fišer, 316 Sanguino Mostajo, Preik, Pekár & Schneider, 2013;Scherer, Kuhnhardt & Schuett, 2017) ...
Full-text available
Preprint
Consistent individual differences in behaviour (animal personality) are widespread throughout the Animal Kingdom. This includes variation in risk-taking versus risk-averse behavioural tendencies. Variation in several personality dimensions is associated with distinct fitness consequences and thus, may become a target of natural and/or sexual selection. However, the link between animal personality and mate choice - as a major component of sexual selection - remains understudied. We asked (1) whether females and males of the livebearing fish Poecilia mexicana prefer risk-taking mating partners (directional mating preference), (2) or if their preferences are dependent on the choosing individual's own personality type (assortative mating). We characterized each test subject for its risk-taking behaviour, assessed as the time to emerge from shelter and enter an unknown area. In dichotomous association preference tests, we offered two potential mating partners that differed in risk-taking behaviour but were matched for other phenotypic traits (body size, shape, and colouration). Females, but not males, exhibited a strong directional preference for risk-taking over risk-averse mating partners. At the same time, the strength of females' preferences correlated positively with their own risk-taking scores. Our study is the first to demonstrate that a strong overall preference for risk-taking mating partners does not preclude effects of choosing individuals' own personality type on (subtle) individual variation in mating preferences. More generally, two different preferences functions appear to interact to determine the outcome of individual mate choice decisions.
... Little is known about male mating preference for consistent differences in behavioural traits (e.g., aggression, boldness and explorative tendency), also referred to as personality differences, coping styles or temperaments (Schuett, Tregenza & Dall, 2010). To the best of our knowledge, the relatively few studies examining mate choice for personalities mainly consider female but not male mate choice (Schuett, Godin & Dall, 2011a;Kralj-Fišer et al., 2013;Teyssier et al., 2014;Montiglio et al., 2016;Scherer, Kuhnhardt & Schuett, 2017a;but see Laubu et al., 2017). Male mate choice for personality traits is especially interesting in bi-parental species because (I) female behaviour can directly affect reproductive success through amount and style of parental care (reviewed in Chira, 2014). ...
... In contrast, males could be expected to show no preference for female boldness because the benefit of a high behavioural level in female boldness during direct offspring care might be rather low. However, we previously tested female preference for male boldness in this species (Scherer, Kuhnhardt & Schuett, 2017a) and found a dis-assortative preference for the behavioural level and an assortative preference for the consistency of male boldness. Most importantly, (dis-)assortment indicates mutual mate choice because it results from a joint assessment process (Johnstone, 1997). ...
... Such a preference pattern may ease parental care coordination through a facilitation of labour division with the bold parent performing territory defence and the shy parent providing direct offspring care. That is, roles might be based on individual behavioural predisposition rather than on the sex (Scherer, Kuhnhardt & Schuett, 2017a). Here, we used an experimental design similar to our female choice study testing for the male perspective: males were allowed to choose between two females that differed in their level and consistency of boldness (activity under simulated predation risk). ...
Full-text available
Article
Background In many species, males have a lower reproductive investment than females and are therefore assumed to increase their fitness with a high number of matings rather than by being choosy. However, in bi-parental species, also males heavily invest into reproduction. Here, reproductive success largely depends on costly parental care; with style and amount of parental effort in several cases being associated with personality differences (i.e., consistent between-individual differences in behaviour). Nonetheless, very little is known about the effect of personality differences on (male) mate choice in bi-parental species. Methods In the present study, we tested male mate choice for the level and consistency of female boldness in the rainbow krib, Pelviachromis pulcher , a bi-parental and territorial West African cichlid. Individual boldness was assumed to indicate parental quality because it affects parental defence behaviour. For all males and females, boldness was assessed twice as the activity under simulated predation risk. Mate choice trials were conducted in two steps. First, we let a male observe two females expressing their boldness. Then, the male could choose between these two females in a standard mate choice test. Results We tested for a male preference for behavioural (dis-)similarity vs. a directional preference for boldness but our data support the absence of effects of male and/or female boldness (level and consistency) on male mating preference. Discussion Our results suggest female personality differences in boldness may not be selected for via male mate choice.
... Some studies found a general preference for [17][18][19] or against [20,21] certain behavioural traits among females of a species. Other studies found females to differ in their mating preference, depending on their own behavioural type, leading to positive assortment [22][23][24] or dis-assortment [25]. In addition, existing studies on the role of behaviour during mate choice have often neglected the role of between-individual differences in behavioural consistency (but see: [26]), although this is an important personality component that can have diverse fitness implications itself [27][28][29]. ...
... Female mating preference was then quantified from both test periods as the strength of preference for each male: the association time for one male was divided by the association for both males (e.g. [25,46,47]). Further, we calculated female side bias as the time a female spent in one preference zone relative to the amount of time spent in both preference zones (sum of both test periods). ...
... Further, we calculated female side bias as the time a female spent in one preference zone relative to the amount of time spent in both preference zones (sum of both test periods). A female was considered side-biased when she spent more than 80% of the test time in just one preference zone [25,48,49]. We decided a priori to exclude side-biased preference data from the analysis (N = 1 mate choice trial) (e.g. ...
Full-text available
Article
Although personality traits can largely affect individual fitness we know little about the evolutionary forces generating and maintaining personality variation. Here, we investigated the hypothesis that personality variation in aggression is sexually selected in the monogamous, bi-parental cichlid Pelvicachromis pulcher. In this species, breeding pairs form territories and they aggressively defend their territory and offspring against con- and heterospecific intruders. In our mate choice study, we followed up two alternative hypotheses. We either expected females to show a directional preference for a high level and high consistency of aggression (potentially indicating mate choice for male parental quality). Alternatively, we expected females to choose males for (dis-)similarity in the level/consistency of aggression (potentially indicating mate choice for compatibility). Individual level and consistency of aggression were assessed for males and females using mirror tests. After eavesdropping on aggressive behaviour of two males (differing in level and consistency of aggression) females were then allowed to choose between the two males. Males, but not females, showed personality variation in aggression. Further, females generally preferred consistent over inconsistent males independent of their level of aggression. We did not detect a general preference for the level of male aggression. However, we found an above average preference for consistent high-aggression males; whereas female preference for inconsistent high-aggression did not deviate from random choice. Our results suggest behavioural consistency of aggression in male rainbow kribs is selected for via female mate choice. Further, our study underlines the importance of considering both the level and the consistency of a behavioural trait in studies of animal behaviour.
... These terms encapsulate the notion of linked social traits that are expressed across various environments, including both social and nonsocial contexts. Indeed, evidence in some species demonstrates heritability of displayed boldness (Ballew et al., 2017;Mont et al., 2018;Scherer et al., 2017), suggesting a genetic basis for the stability of individual differences across time. Likewise, the level of an individual's boldness is often consistent across social contexts (Colléter and Brown, 2011;Koolhaas et al., 2010;Qu et al., 2018;Reaney and Backwell, 2007), where individuals that may be shy within a reproductive social encounter may also be shy within an agonistic encounter (Kabelik et al., 2021). ...
... Correlated boldness measures are often referred to as behavioral syndromes (Colléter and Brown, 2011;Koolhaas et al., 2010;Qu et al., 2018;Reaney and Backwell, 2007). The stability of boldness across time, on the other hand, supports the notion that these traits are at least partly hard-wired, as would be expected if boldness has strong heritable components, as has been suggested by previous studies (Ballew et al., 2017;Mont et al., 2018;Scherer et al., 2017). Various selective pressures appear to maintain variability in exhibited boldness within populations (Koolhaas et al., 2010;Smith and Blumstein, 2010). ...
Article
Across species, individuals within a population differ in their level of boldness in social encounters with conspecifics. This boldness phenotype is often stable across both time and social context (e.g., reproductive versus agonistic encounters). Various neural and hormonal mechanisms have been suggested as underlying these stable phenotypic differences, which are often also described as syndromes, personalities, and coping styles. Most studies examining the neuroendocrine mechanisms associated with boldness examine subjects after they have engaged in a social interaction, whereas baseline neural activity that may predispose behavioral variation is understudied. The present study tests the hypotheses that physical characteristics, steroid hormone levels, and baseline variation in Ile³-vasopressin (VP, a.k.a., Arg⁸-vasotocin) signaling predispose boldness during social encounters. Boldness in agonistic and reproductive contexts was extensively quantified in male green anole lizards (Anolis carolinensis), an established research organism for social behavior research that provides a crucial comparison group to investigations of birds and mammals. We found high stability of boldness across time, and between agonistic and reproductive contexts. Next, immunofluorescence was used to colocalize VP neurons with phosphorylated ribosomal protein S6 (pS6), a proxy marker of neural activity. Vasopressin-pS6 colocalization within the paraventricular and supraoptic nuclei of the hypothalamus was inversely correlated with boldness of aggressive behaviors, but not of reproductive behaviors. Our findings suggest that baseline vasopressin release, rather than solely context-dependent release, plays a role in predisposing individuals toward stable levels of displayed aggression toward conspecifics by inhibiting behavioral output in these contexts.
... For example, female guppies prefer to mate with bolder males (e.g. Godin and Dugatkin 1996), but female rainbow kribs (Pelvicachromis pulcher) preferentially mate with males who display a dissimilar level of boldness to themselves (Scherer et al. 2017), and pairs of great tits (Parus major) that mated assortatively at either extreme of the boldness spectrum had the greatest reproductive success (Both et al. 2005). A meta-analysis by Smith and Blumstein (2008) on multiple taxa, including fishes, found a significant positive correlation between boldness and reproductive success in captive animals. ...
... Sneddon 2003;Wilson and Stevens 2005;Adriaenssens and Johnsson 2010) that are heritable (Vilhunen et al. 2008;Kortet et al. 2014) and evidence that personality can affect mate choice (e.g. Godin and Dugatkin 1996;Both et al. 2005;David and Cézilly 2011;Scherer et al. 2017). ...
Full-text available
Article
Mate choice in most organisms is not random, but determined by a suite of interacting traits and environmental factors. While the selective pressures underlying differences in mate choice between species, populations, individuals and even within individuals has been gaining interest, there still remains unexplained variation in mate preferences especially in non-model systems. Despite being of social, environmental and economic importance there is comparatively little known about how salmonids and other tetraploids make mate choice decisions in the wild and the resultant reproductive success (i.e. the number of offspring which survive to sexual maturity). Resolving questions related to salmonid mate choice is of particular importance given that humans have been supplementing salmon populations through aquaculture for decades. Despite these efforts, hatchery produced fish have lower reproductive success relative to their wild counterparts and salmon populations are declining. Most studies on mate choice and reproductive success in salmonids focus on body size and major histocompatibility complex based choice. However, mate choice can also be affected by other factors including other genetic factors, predation risk and social environment. Here, we (a) synthesize what is presently known about mate choice and reproductive success in salmonids, (b) identify gaps in knowledge and areas where there is a lack of consensus in results, and (c) suggest interdisciplinary ways of advancing our understanding of mate choice in salmonids and other polyploids.
... Consistent with Xu et al. [45], we found the existence of personality and behavioural syndrome in male mosquitofish from the same population. Some studies have found negative assortative preference related to behavioural traits and speculated that dissimilarity may increase behavioural compatibility between paired mating partners [66], and thus facilitate parental labour division, which may benefit offspring in biparental species [67]. Conversely, it has also been argued that cooperation between mating partners during the reproduction period could be promoted by behavioural synchronization (i.e., positive assortment), thus increasing reproductive success [61,68]. ...
Full-text available
Article
Background Despite its important implications in behavioural and evolutionary ecology, male mate choice has been poorly studied, and the relative contribution of personality and morphological traits remains largely unknown. We used standard two-choice mating trials to explore whether two personality traits (i.e., shyness and activity) and/or body size of both sexes affect mate choice in male mosquitofish Gambusia affinis. In the first set of trials involving 40 males, we tested whether males would prefer larger females and whether the preference would be affected by males’ body length and personality traits, and females’ activity level. In the second set of trials (using another 40 males), we tested whether males would prefer more active females and whether the preference would be affected by males’ body length and personality traits. Results Both shyness and activity in males were significantly repeatable and constituted a behavioural syndrome. No overall directional preference for large (or small) females with the same activity levels was detected because larger males preferred larger females and smaller males chose smaller females. Males’ strength of preference for larger females was also positively correlated with the activity level of larger females but negatively with the activity level of smaller females. Males spent more time associating with active females regardless of their body lengths, indicating males’ selection was more influenced by female activity level than body size. Males’ preference for inactive females was enhanced when females became active. There was no convincing evidence for the effect of males’ personality traits or body length on their preferences for females’ activity level. Conclusions Our study supports the importance of body size in male mate choice but highlights that personality traits may outweigh body size preferences when males choose mating partners.
... intriguing role in many taxa. Depending on a species' respective environmental conditions, assortative mate choice of similarly behaving individuals or disassortative mate choice of apparently antagonistic, but complementary behaving individuals may be favored (mammals: e.g., Ihara and Feldman, 2003;Massen and Koski, 2014;Rangassamy et al., 2015;Martin-Wintle et al., 2017; birds: e.g., Both et al., 2005;van Oers et al., 2008;Schuett et al., 2011;Gabriel and Black, 2012;Horton et al., 2012;Fox and Millam, 2014;Pogány et al., 2018;Clermont et al., 2019;Collins et al., 2019; fish: e.g., Ariyomo and Watt, 2013;Laubu et al., 2017;Scherer et al., 2017;Schweitzer et al., 2017;Chen et al., 2018; invertebrates: e.g., Kralj-Fišer et al., 2013;Montiglio et al., 2016;Baur et al., 2019). This could be a decisive competitive advantage both genotypically and phenotypically in the context of bi-parental brood care. ...
Full-text available
Article
The idea of “smart is sexy,” meaning superior cognition provides competitive benefits in mate choice and, therefore, evolutionary advantages in terms of reproductive fitness, is both exciting and captivating. Cognitively flexible individuals perceive and adapt more dynamically to (unpredictable) environmental changes. The sex roles that females and males adopt within their populations can vary greatly in response to the prevalent mating system. Based on how cognition determines these grossly divergent sex roles, different selection pressures could possibly shape the (progressive) evolution of cognitive abilities, suggesting the potential to induce sexual dimorphisms in superior cognitive abilities. Associations between an individual’s mating success, sexual traits and its cognitive abilities have been found consistently across vertebrate species and taxa, providing evidence that sexual selection may well shape the supporting cognitive prerequisites. Yet, while superior cognitive abilities provide benefits such as higher feeding success, improved antipredator behavior, or more favorable mate choice, they also claim costs such as higher energy levels and metabolic rates, which in turn may reduce fecundity, growth, or immune response. There is compelling evidence in a variety of vertebrate taxa that females appear to prefer skilled problem-solver males, i.e., they prefer those that appear to have better cognitive abilities. Consequently, cognition is also likely to have substantial effects on sexual selection processes. How the choosing sex assesses the cognitive abilities of potential mates has not been explored conclusively yet. Do cognitive skills guide an individual’s mate choice and does learning change an individual’s mate choice decisions? How and to which extent do individuals use their own cognitive skills to assess those of their conspecifics when choosing a mate? How does an individual’s role within a mating system influence the choice of the choosing sex in this context? Drawing on several examples from the vertebrate world, this review aims to elucidate various aspects associated with cognitive sex differences, the different roles of males and females in social and sexual interactions, and the potential influence of cognition on mate choice decisions. Finally, future perspectives aim to identify ways to answer the central question of how the triad of sex, cognition, and mate choice interacts.
... For instance, in the zebra finch, Taeniopygia guttata, intermediate and highly exploratory females showed an assortative preference for highly exploratory males (assortative preference; Schuett, Godin, & Dall, 2011). In rainbow kribs, Pelvicachromis pulcher, bold females preferred docile males, showing a disassortative mate preference, but females preferred males with a similar level of boldness predictability to themselves, indicating an assortative mate preference (Scherer, Kuhnhardt, & Schuett, 2017). ...
Full-text available
Article
Consistent interindividual differences in behaviour (i.e. personality) and intraindividual variability in behaviour (higher intraindividual variability means lower behavioural predictability) are common across animal taxa. However, how personality and behavioural predictability of males and females influence female mate choice and maleemale competition remains poorly understood. Here, we investigated this in the jade jumping spider, Siler semiglaucus. After assessing the level of aggression (an individual's average aggression) and aggression predictability (the variability around average aggression within an individual) of both S. semiglaucus males and females, we performed female mate choice trials to test whether aggression and aggression predictability in females, males or both would affect female mate choice. We also conducted male contest trials to test whether male aggression or aggression predictability would influence the outcomes of male contests. We found that both females and males showed consistent interindividual differences in aggression, and aggressive spiders were more predictable than less aggressive ones. Despite a positive correlation between aggression and predictability, male aggression predicted female mate choice better than aggression predictability. Females showed a directional preference for aggressive males over docile males regardless of female aggression or male aggression predictability. Predictable aggressive males were also more likely to win contests. Our results suggest that both female mate choice and maleemale competition favour males with high aggression, and thus total sexual selection that acts on male aggression may be reinforcing. These findings also highlight that male S. semiglaucus with a higher level of aggression may have better reproductive performance.
... Behavioral boldness and stress coping styles appear to have strong heritable components (Ballew et al., 2017;Mont et al., 2018;Scherer et al., 2017) and variability of these traits within a population appears to be maintained by selective pressures Smith and Blumstein, 2010). Furthermore, as in this study, behavioral boldness in various species is stable, including across social contexts (hence eliciting the term behavioral syndrome) (Colléter and Brown, 2011;Koolhaas et al., 2010;Qu et al., 2018;Reaney and Backwell, 2007). ...
Article
Within populations, some individuals tend to exhibit a bold or shy social behavior phenotype relative to the mean. The neural underpinnings of these differing phenotypes – also described as syndromes, personalities, and coping styles – is an area of ongoing investigation. Although a social decision-making network has been described across vertebrate taxa, most studies examining activity within this network do so in relation to exhibited differences in behavioral expression. Our study instead focuses on constitutive gene expression in bold and shy individuals by isolating baseline gene expression profiles that influence social boldness predisposition, rather than those reflecting the results of social interaction and behavioral execution. We performed this study on male green anole lizards (Anolis carolinensis), an established model organism for behavioral research, which provides a crucial comparison group to investigations of birds and mammals. After identifying subjects as bold or shy through repeated reproductive and agonistic behavior testing, we used RNA sequencing to compare gene expression profiles between these groups within various forebrain, midbrain, and hindbrain regions. The ventromedial hypothalamus had the largest group differences in gene expression, with bold males having increased expression of neuroendocrine and neurotransmitter receptor and calcium channel genes compared to shy males. Conversely, shy males express more integrin alpha-10 in the majority of examined regions. There were no significant group differences in physiology or hormone levels. Our results highlight the ventromedial hypothalamus as an important center of behavioral differences across individuals and provide novel candidates for investigations into the regulation of individual variation in social behavior phenotype.
... While selecting a mate relative to their own traits, animals may indicate preferences for mates that are similar to them (positive assortative, or assortative mating), or exhibit a preference for individuals that are dissimilar (negative assortative, or disassortative mating). For example, individuals may pair assortatively (orb weaving spiders, Kralj-Fiser et al., 2013) or disassortatively (cockatiels, Fox & Millam, 2014;giant pandas, Martin-Wintle et al., 2017) by aggression, and assortatively (dumpling squids, Sinn et al., 2006) or disassortatively (rainbow kribs, Scherer et al., 2017) by boldness. Moreover, exploratory male great tits may prefer exploratory females (Groothuis & Carere, 2005) and pairs can achieve greater reproductive success through assortative mating (Both et al., 2005). ...
Article
In species with long-term pair bonds, such as zebra finches, evaluating the quality of potential mates is critically important. Courtship is an opportunity to evaluate information from dynamic behavioural cues. Personality traits, as stable individual differences in behaviour, could predict the quality of a potential mate. How might personality traits influence mate choice? We examined the influence of several personality traits, including exploration, aggression, and social preference, on pair formation in zebra finches. We provided birds with a variety of potential mates and allowed them to select a pair partner. Our semi-naturalistic mate choice paradigm allowed birds to observe social information over an extended period, simulating the challenges of social evaluation that birds encounter in the wild. We found that pairing is influenced by personality, with birds selecting mates similar to them in exploration. The partner’s exploration score relative to their own was more important than the absolute exploration score.
... However, the evidence for such a link is overall mixed (Schuett et al., 2010). For example, individual personality has been found to influence mate choice, leading to personality-based (dis-) assortative mating in some species (e.g., Kralj-Fišer, Mostajo, Preik, Pekár, & Schneider, 2013;Montiglio, Wey, Chang, Fogarty, & Sih, 2016;Scherer, Kuhnhardt, & Schuett, 2017;Schuett, Godin, & Dall, 2011;Sommer-Trembo et al., 2016;Sommer-Trembo, Schreier, & Plath, 2020), but other studies did not find any relationship between personality and mate choice (e.g., Bierbach, Sommer-Trembo, Hanisch, Wolf, & Plath, 2015;Laubu, Schweitzer, Motreuil, Louâpre, & Dechaume-Moncharmont, 2017;Muraco, Aspbury, & Gabor, 2014;Scherer & Schuett, 2018). Therefore, there is scope for additional studies to further illuminate the nature and direction of the relationship between individual personality and mate choice and the underlying mechanisms (Schuett et al., 2010), perhaps more so for males than females because of the historical bias of previous mate-choice studies towards females (Andersson, 1994;Rosenthal, 2017). ...
Article
Within populations, individual animals vary considerably in their behaviour, including mate choice and personality. There is mounting interest in the potential covariation between these two behaviours within individuals, such that personality would influence mate choice. We experimentally tested this proposition under controlled laboratory conditions using male Trinidadian guppies (Poecilia reticulata ) as a model study system. We assayed repeatedly the mating preference of individual males for females based on their body size. Additionally, we assayed repeatedly two ecologically relevant personality traits in males, namely exploration of a novel environment and boldness under a simulated predation threat. Finally, we analysed whether male mating preference and personality traits were repeatable, and tested whether the personality of individual males was correlated (covaried) with their mating preference scores. Although all but one of the measures of exploration and boldness behaviour were repeatable over time, male mating preference scores were not repeatable. Measures of male exploration and boldness were not inter‐correlated among individuals, suggesting the absence of a behavioural syndrome between exploration and boldness. Unexpectedly, males did not exhibit on average a significant mating preference for larger females over smaller ones; they chose randomly between the paired stimulus females. Overall, we found no compelling evidence for a relationship between individual personality traits and mating preference in male guppies, suggesting that personality does not predict mate choice, at least in our study population and under our experimental conditions. We discuss potential factors, other than male personality and body length, that might maintain inter‐individual variation in male mating preferences in the guppy in the wild.
... Choosing a male with a complementary BT could allow a female to balance out shortcomings in her own parental care. Although the effect of different BTs on parenting behavior was not considered, this could explain the behavior of female rainbow krib (Pelvicachromis pulcher) that prefer males that are dissimilar in terms of level of boldness but similar in terms of consistency [104]. ...
Article
Consistent individual differences in behavior [i.e., behavioral types (BTs)], are common across the animal kingdom. Consistency can make behavior an adaptive trait for mate choice decisions. Here, we present a conceptual framework to explain how and why females might evaluate a male’s BT before mating. Because BTs are consistent across time or context, a male’s BT can be a reliable indicator of his potential to provide direct benefits. Heritable BTs can enable informed mate choice via indirect benefits. Many key issues regarding patterns of mate choice, including sensory biases, context dependence, and assortative mating apply to BT-dependent mate choice. Understanding the relationship between BTs and mate choice may offer insights into patterns of variation and consistency common in behavioral traits.
... We gave the focal individual 3 min for acclimation, during which it could see both animations. Then, we gently removed the cylinder and measured the time the focal individual spent in each preference zone during a 5 min observation period (Sato and Karino 2006;Scherer et al. 2017b). To avoid potential side-biases, we interchanged both animations (from left to right and vice versa) immediately after the first 5 min observation period and repeated the assessment of association preferences. ...
Full-text available
Article
While many mating preferences have a genetic basis, the question remains as to whether and how learning/experience can modify individual mate choice decisions. We used wild-caught (predator-experienced) and F1 laboratory-reared (predator-naïve) invasive Western mosquitofish (Gambusia affinis) from China to test whether mating preferences (assessed in a first mate choice test) would change under immediate predation threat. The same individuals were tested in a second mate choice test during which one of three types of animated predators was presented: (a) a co-occurring predator, (b) a co-evolved but not currently co-occurring predator, and (c) a non-piscivorous species as control. We compared preference scores derived from both mate choice tests to separate innate from experiential effects of predation. We also asked whether predator-induced changes in mating preferences would differ between sexes or depend on the choosing individual’s personality type and/or body size. Wild-caught fish altered their mate choice decisions most when exposed to the co-occurring predator while laboratory-reared individuals responded most to the co-evolved predator, suggesting that both innate mechanisms and learning effects are involved. This behavior likely reduces individuals’ risk of falling victim to predation by temporarily moving away from high-quality (i.e., conspicuous) mating partners. Accordingly, effects were stronger in bolder than shyer, large- compared to small-bodied, and female compared to male focal individuals, likely because those phenotypes face an increased predation risk overall. Our study adds to the growing body of literature appreciating the complexity of the mate choice process, where an array of intrinsic and extrinsic factors interacts during decision-making.
... Boldness broadly encompasses various animal behaviors that indicate an individual's response to a risky environment or situation (Réale et al. 2007). Bold individuals, those that are more risk-prone, are often more dominant and successful at acquiring mates compared to less bold individuals (Reaney and Backwell 2007;Colléter and Brown 2011;Ballew et al. 2017;Scherer et al. 2017). Because of their enhanced ability to acquire resources, males that are bolder tend to also have higher growth rates and be larger in body size (Brown and Braithwaite 2004;Adriaenssens and Johnsson 2010;Shine et al. 2016), which might also be preferred by potential female mates (Endler and Houde 1995;Rosenthal and Evans 1998). ...
Full-text available
Article
Male sexually selected signals can indicate competitive ability by honestly signaling fitness-relevant traits such as condition or performance. However, behavior can also influence contest outcomes; in particular, boldness often predicts dominance rank and mating success. Here, we sought to determine whether male ornament size is associated with consistent individual differences in boldness in water anoles Anolis aquaticus. We measured the relative size of the dewlap, a flap of skin under the chin that is a sexually-selected ornament in Anolis lizards, and tested for associations with responses to a novel and potentially risky environment: time to emerge from a refuge into an arena and number of head scans post-emergence. We found that individuals consistently differed in both time to emerge and head scanning (i.e., individual responses were repeatable), and that dewlap size was negatively related to number of head scans. This suggests that ornament size could indicate male boldness if scanning represents antipredator vigilance. We found that that males that had larger relative dewlaps were also in better body condition, but boldness (i.e., head scanning) was not related to condition. Lastly, we found consistent differences in behavior between trials, showing that anoles were becoming habituated or sensitized to the testing arena. Overall, our study shows that in addition to indicating condition and performance, dewlap size could also honestly indicate male boldness in Anolis lizards.
... After a 5 min habituation period, during which the fish could see both animations, we gently removed the cylinder. During the following 5 min observation period we measured association times, i.e., times spent in each preference zone [104,106,107]. Association time in this experimental situation has been demonstrated to be a good indicator of female mating preferences in related species [5,51,[108][109][110]. ...
Full-text available
Article
Consistent individual differences in behavioral tendencies (animal personality) can affect individual mate choice decisions. We asked whether personality traits affect male and female mate choice decisions similarly and whether potential personality effects are consistent across different mate choice situations. Using western mosquitofish (Gambusia affinis) as our study organism, we characterized focal individuals (males and females) twice for boldness, activity, and sociability/shoaling and found high and significant behavioral repeat-ability. Additionally, each focal individual was tested in two different dichotomous mate choice tests in which it could choose between computer-animated stimulus fish of the opposite sex that differed in body size and activity levels, respectively. Personality had different effects on female and male mate choice: females that were larger than average showed stronger preferences for large-bodied males with increasing levels of boldness/activity (i.e., towards more proactive personality types). Males that were larger than average and had higher shoaling tendencies showed stronger preferences for actively swimming females. Size-dependent effects of personality on the strength of preferences for distinct phenotypes of potential mating partners may reflect effects of age/experience (especially in females) and social dominance (especially in males). Previous studies found evidence for assortative mate choice based on personality types or hypothesized the existence of behavioral syndromes of individuals' choosiness across mate choice criteria, possibly including other personality traits. Our present study exemplifies that far more complex patterns of personality-dependent mate choice can emerge in natural systems.
... After a 5 min habituation period, during which the fish could see both animations, we gently removed the cylinder. During the following 5 min observation period we measured association times, i.e., times spent in each preference zone [104,106,107]. Association time in this experimental situation has been demonstrated to be a good indicator of female mating preferences in related species [5,51,[108][109][110]. ...
Full-text available
Article
Consistent individual differences in behavioral tendencies (animal personality) can affect individual mate choice decisions. We asked whether personality traits affect male and female mate choice decisions similarly and whether potential personality effects are consistent across different mate choice situations. Using western mosquitofish (Gambusia affinis) as our study organism, we characterized focal individuals (males and females) twice for boldness, activity, and sociability/shoaling and found high and significant behavioral repeat-ability. Additionally, each focal individual was tested in two different dichotomous mate choice tests in which it could choose between computer-animated stimulus fish of the opposite sex that differed in body size and activity levels, respectively. Personality had different effects on female and male mate choice: females that were larger than average showed stronger preferences for large-bodied males with increasing levels of boldness/activity (i.e., towards more proactive personality types). Males that were larger than average and had higher shoaling tendencies showed stronger preferences for actively swimming females. Size-dependent effects of personality on the strength of preferences for distinct phenotypes of potential mating partners may reflect effects of age/experience (especially in females) and social dominance (especially in males). Previous studies found evidence for assortative mate choice based on personality types or hypothesized the existence of behavioral syndromes of individuals' choosiness across mate choice criteria, possibly including other personality traits. Our present study exemplifies that far more complex patterns of personality-dependent mate choice can emerge in natural systems.
Article
Biological invasions and continued salinization of freshwater are two global issues with largely serious ecological consequences. Increasing salinity in freshwater systems, as an environmental stressor, may negatively affect normal life activities in fish. It has been documented that salinity limits the invasive success of alien species by mediating physiological and life-history performances, however, there are few studies on how salinity affects its invasive process via altered behaviors. Using wild-caught invasive western mosquitofish (Gambusia affinis) as animal model, in this study, we asked whether gradual increasing salinity affects behaviors (personality and mate choice decision here), life-history traits, as well as the correlation between them by exposing G. affiins to three levels salinity (freshwater, 10 and 20‰). Results showed that, with increased salinity, male tended to be shyer, less active, less sociable, and reduced desire to mate, and female tended to be shyer, less active and lost preferences for the larger male. Furthermore, across salinity treatments, male exhibited reduced body fat content and rising reproduction allocation, however, pregnant female revealed diametrically opposed trends. In addition, the correlation between life-history traits and behaviors was only identified in pregnant female. It seems that either salinity or life-history traits directly affects mosquitofish behaviors. In summary, our results partially emphasize the harmful consequences of salinity on both life-history traits and behavioral performances. These findings provide a novel perspective on how salinity potentially affect fish fitness via altering personalities, mate choice decisions, as well as body condition, and hence supports the idea that salinity could affect the spread of invasive mosquitofish.
Article
Within populations, individuals often show repeatable variation in behaviour, called 'animal personality'. In the last few decades, numerous empirical studies have attempted to elucidate the mechanisms maintaining this variation, such as life-history trade-offs. Theory predicts that among-individual variation in behavioural traits could be maintained if traits that are positively associated with reproduction are simultaneously associated with decreased survival, such that different levels of behavioural expression lead to the same net fitness outcome. However, variation in resource acquisition may also be important in mediating the relationship between individual behaviour and fitness components (survival and reproduction). For example, if certain phenotypes (e.g. dominance or aggressiveness) are associated with higher resource acquisition , those individuals may have both higher reproduction and higher survival, relative to others in the population. When individuals differ in their ability to acquire resources, trade-offs are only expected to be observed at the within-individual level (i.e. for a given amount of resource, if an individual increases its allocation to reproduction, it comes at the cost of allocation to survival, and vice versa), while among individuals traits that are associated with increased survival may also be associated with increased reproduction. We performed a systematic review and meta-analysis, asking: (i) do among-individual differences in behaviour reflect among-individual differences in resource acquisition and/or allocation, and (ii) is the relationship between behaviour and fitness affected by the type of behaviour and the testing environment? Our meta-analysis consisted of 759 estimates from 193 studies. Our meta-analysis revealed a positive correlation between pairs of estimates using both survival and reproduction as fitness proxies. That is, for a given study, behaviours that were associated with increased reproduction were also associated with increased survival, suggesting that variation in behaviour at the among-individual level largely reflects differences among individuals in resource acquisition. Furthermore, we found the same positive correlation between pairs of estimates using both survival and reproduction as fitness proxies at the phenotypic level. This is significant because we also demonstrated that these phenotypic correlations primarily reflect within-individual correlations. Thus, even when accounting for among-individual differences in resource acquisition, we did not find evidence of trade-offs at the within-individual level. Overall, the relationship between behaviour and fitness proxies was not statistically different from zero at the among-individual, phenotypic, and within-individual levels; this relationship was not affected by behavioural category nor by the testing condition. Our meta-analysis highlights that variation in resource acquisition may be more important in driving the relationship between behaviour and fitness than previously thought, including at the within-individual level. We suggest that this may come about via heterogeneity in resource availability or age-related effects, with higher resource availability and/or age leading to state-dependent shifts in behaviour that simultaneously increase both survival and reproduction. We emphasize that future studies examining the mechanisms maintaining behavioural variation in populations should test the link between behavioural expression and resource acquisition-both within and among individuals. Such work will allow the field of animal personality to develop specific predictions regarding the mediating effect of resource acquisition on the fitness consequences of individual behaviour.
Preprint
Across species, individuals within a population differ in their level of boldness in social encounters with conspecifics. This boldness phenotype is often stable across both time and social context (e.g., reproductive versus agonistic encounters). Various neural and hormonal mechanisms have been suggested as underlying these stable phenotypic differences, which are often also described as syndromes, personalities, and coping styles. Most studies examining the neuroendocrine mechanisms associated with behavioral boldness examine subjects after they have engaged in a social interaction, whereas baseline neural activity that may predispose behavioral variation is understudied. The present study tests the hypotheses that physical characteristics, steroid hormone levels, and baseline variation in Ile3-vasopressin (VP, a.k.a., Arg8-vasotocin) signaling predispose social boldness. Behavioral boldness in agonistic and reproductive contexts was extensively quantified in male green anole lizards (Anolis carolinensis), an established research organism for social behavior research that provides a crucial comparison group to investigations of birds and mammals. We found high stability of boldness across time, and between agonistic and reproductive contexts. Next, immunofluorescence was used to colocalize VP neurons with phosphorylated ribosomal protein S6 (pS6), a proxy marker of neural activity. VP-pS6 colocalization within the paraventricular and supraoptic nuclei of the hypothalamus was inversely correlated with aggression boldness, but not reproductive behavior boldness. Our findings suggest that baseline vasopressin release, rather than solely context-dependent release, plays a role in predisposing individuals toward stable levels of aggressive boldness toward conspecifics by inhibiting behavioral output in these contexts.
Full-text available
Preprint
Background Despite its important implications in behavioural and evolutionary ecology, male mate choice has been little studied, and the relative contribution of personality and morphological traits remains largely unknown. Using standard two-choice mating trials, we studied whether personality traits (i.e. shyness and activity) and body size of both sexes affect mate choice in male mosquitofish Gambusia affinis. Results Both shyness and activity in males were significantly repeatable and constituted a behavioural syndrome. No overall directional preference for large (or small) females with the same activity levels was detected because larger males preferred larger females and smaller males chose smaller females. However, males spent more time associating with active females regardless of their body lengths and had an enhanced preference for inactive females when they increased activity levels. We also found that more proactive (bolder and more active) males had stronger preferences for more active females. Conclusions Our study supports the importance of body size in male mate choice but highlights that personality traits may outweigh body size preferences when males choose mating partners.
Full-text available
Article
Virtual stimuli represent an increasingly popular tool in the study of animal behaviour. Modern techniques have the potential to simplify and improve traditional experiments using live stimuli. However, the increasing availability of diverse techniques is associated with problems and limitations. Although many new methods have been developed, their validation remains largely untested. In the present study, we therefore performed two experiments to test whether 2-D animations of predators and conspecifics elicit biologically appropriate behavioural responses in male rainbow kribs, Pelvicachromis pulcher. Individual responses towards a sympatric natural fish predator, Parachanna obscura, were tested using live predators and still colour photographs, animated using PowerPoint©. Compared to control trials (empty aquarium and white computer screen, respectively), individuals decreased their activity in response to both live and animated predators. We found no difference in activity between live and animation trials. Further, we tested individual aggression (frequency of aggressive behaviours) exhibited towards live and animated conspecifics. Individual aggressive behaviours shown towards live and animated conspecifics were positively correlated. Moreover, an individual's mean distance towards the opponent was a suitable proxy for individual aggression permitting the facilitation and standardisation of an individual's aggression through the use of a tracking software compared with the more laborious, traditional manual assessment. Our results show that simple, inexpensive animation techniques have the potential to provide an easy-to-apply and useful technological advance in animal behaviour research.
Full-text available
Article
It is well established that living in groups helps animals avoid predation and locate resources, but maintaining a group requires collective coordination, which can be difficult when individuals differ from one another. Personality variation (consistent behavioural differences within a population) is already known to be important in group interactions. Growing evidence suggests that individuals also differ in their consistency, i.e. differing in how variable they are over time, and theoretical models predict that this consistency can be beneficial in social contexts. We used three-spined sticklebacks (Gasterosteus aculeatus) to test whether the consistency in, as well as average levels of, risk taking behaviour (i.e. boldness) when individuals were tested alone affects social interactions when fish were retested in groups of 2 and 4. Behavioural consistency, independently of average levels of risk-taking, can be advantageous: more consistent individuals showed higher rates of initiating group movements as leaders, more behavioural coordination by joining others as followers, and greater food consumption. Our results have implications for both group decision making, as groups composed of consistent individuals are more cohesive, and personality traits, as social interactions can have functional consequences for consistency in behaviour and hence the evolution of personality variation.
Full-text available
Article
Behavioral similarity between partners is likely to promote within-pair compatibility and to result in better reproductive success. Therefore, individuals are expected to choose a partner that is alike in behavioral type. However, mate searching is very costly and does not guarantee finding a matching partner. If mismatched individuals pair, they may benefit from increasing their similarity after pairing. We show in a monogamous fish species—the convict cichlid—that the behavioral similarity between mismatched partners can increase after pairing. This increase resulted from asymmetrical adjustment because only the reactive individual became more alike its proactive partner, whereas the latter did not change its behavior. The mismatched pairs that increased their similarity not only improved their reproductive success but also raised it up to the level of matched pairs. While most studies assume that assortative mating results from mate choice, our study suggests that postpairing adjustment could be an alternative explanation for the high behavioral similarity between partners observed in the field. It also explains why interindividual behavioral differences can be maintained within a given population.
Full-text available
Article
Research on mate choice has primarily focused on preferences for quality indicators, assuming that all individuals show consensus about who is the most attractive. However, in some species, mating preferences seem largely individual-specific, suggesting that they might target genetic or behavioral compatibility. Few studies have quantified the fitness consequences of allowing versus preventing such idiosyncratic mate choice. Here, we report on an experiment that controls for variation in overall partner quality and show that zebra finch (Taeniopygia guttata) pairs that resulted from free mate choice achieved a 37% higher reproductive success than pairs that were forced to mate. Cross-fostering of freshly laid eggs showed that embryo mortality (before hatching) primarily depended on the identity of the genetic parents, whereas offspring mortality during the rearing period depended on foster-parent identity. Therefore, preventing mate choice should lead to an increase in embryo mortality if mate choice targets genetic compatibility (for embryo viability), and to an increase in offspring mortality if mate choice targets behavioral compatibility (for better rearing). We found that pairs from both treatments showed equal rates of embryo mortality, but chosen pairs were better at raising offspring. These results thus support the behavioral, but not the genetic, compatibility hypothesis. Further exploratory analyses reveal several differences in behavior and fitness components between "free-choice" and "forced" pairs.
Full-text available
Article
Females that mate multiply have the possibility to exert postcopulatory choice and select more compatible sperm to fertilize eggs. Prior work suggests that dissimilarity in Major Histocompatibility Complex (MHC) plays an important role in determining genetic compatibility between partners. Favouring a partner with dissimilar MHC alleles would result in offspring with high MHC diversity, and therefore with enhanced survival thanks to increased resistance to pathogens and parasites. The high variability of MHC genes may further allow discrimination against the sperm from related males, reducing offspring homozygosity and inbreeding risk. Despite the large body of work conducted at precopulatory level, the role of MHC similarity between partners at postcopulatory level has been rarely investigated. We used an internal fertilizing fish with high level of multiple matings (Poecilia reticulata) to study if MHC similarity plays a role in determining the outcome of fertilization when sperm from two males compete for the same set of eggs. We also controlled for genome-wide similarity by determining similarity at 10 microsatellite loci. Contrary to prediction, we found that the more MHC-similar male sired more offspring while similarity at the microsatellite loci did not predict the outcome of sperm competition. Our results suggest that MHC discrimination may be involved in avoidance of hybridization or outbreeding rather than inbreeding avoidance. This, coupled with similar findings in salmon, suggest that the preference for MHC-dissimilar mates is far from being unanimous, and that pre- and postcopulatory episodes of sexual selection can indeed act in opposite directions. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Full-text available
Article
Consistent individual differences in personality or temperament have been observed in many animal taxa, and one particular trait, boldness, has been studied extensively. Most studies on mate choice and personality have focused on female preference and have showed that females prefer to mate with bolder males. However, the influence of the females personality on this mate preference and on her compatibility with a mate with particular traits has been largely neglected. Here, using the guppy Poecilia reticulata, we investigated the effect of female boldness on mate choice and of the combinations of this trait in the male and female of a mating pair on parturition and brood size. Our results showed that female boldness did not affect mate choice, and brood size was independent of the boldness of the male and female in a pair. However, overall, females who mated with males with a dissimilar degree of boldness to themselves had a lower parturition success than females who mated with males with a similar degree of boldness. This work suggests that the combination of boldness characteristics within a pair influences reproductive success and that individuals of similar personality are more compatible in reproduction. The lower success of disassortative matings is consistent with the hypothesis that variation in personalities is maintained by disruptive or frequency-dependent selection, driven by contrasting physical or social environments that favor alternative rather than intermediate behavioral phenotypes.
Full-text available
Article
Recent theory predicts that personality traits contributing to resource intake rates could reflect the individual's condition-dependent capacity to resist parasites and pathogens. Since females often prefer mates with strong immune defence, females could potentially gain fitness benefits by using male's behavioral type (BT) as one mate choice criteria. We studied if female field crickets base their mate choice on male boldness and if the boldness would predict survival under challenge to opportunist pathogen Serratia marcescens. In addition, we tested if three different females would prefer the same males. Boldness did not explain individual's lifespan in experimental infection. All the three females preferred one male within pair over the other male in 26.9% of the mate choice tests, but the preferred male varied between the females. Our results suggest that females show preferences for bold BTs, but that male boldness may not reflect his capacity to resist bacterial pathogens.
Full-text available
Article
The development of preferences for males with sexual ornaments is still not well understood. Therefore, we investigated whether the use of public information in mate-choice copying can explain the development of mate preferences for a novel phenotype in male and female zebra finches (Taeniopygia guttata castanotis). In a binary choice situation, birds could choose between two conspecifics of the opposite sex of two different phenotypes: an unadorned phenotype, and an adorned phenotype with a red feather on the forehead, simulating the novel phenotype. When no public information was provided, females and males spent a similar amount of time in front of individuals of both phenotypes. After observing a single, unadorned individual and a pair with one adorned partner for 2 hours, females and males could choose between other individuals of both phenotypes in two consecutive mate-choice tests. Females spent significantly more time in front of males of the adorned phenotype after the observation period than before the observation period. This shows that females copied and generalized the mate choice of other females for males of the new phenotype. In contrast to females, males did not copy the mate choice of other males. Results from controls provided no alternative explanation for the change in mate choice in females. Our study shows that sexes differ in using public information in mate-choice decisions and that mate-choice copying is a meaningful mechanism for the cultural inheritance of mate preferences in female zebra finches.
Full-text available
Article
Investigating the role of visual information in animal communication often involves the experimental presentation of live stimuli, mirrors, dummies, still images, video recordings or computer animations. In recent years computer animations have received increased attention, as this technology allows the presentation of moving stimuli that exhibit a fully standardized behaviour. However, whether simple animated 2D-still images of conspecific and heterospecific stimulus animals can elicit detailed behavioural responses in test animals is unclear thus far. In this study we validate a simple method to generate animated still images using Power Point presentations as an experimental tool. We studied context-specific behaviour directed towards conspecifics and heterospecifics, using the cooperatively breeding cichlid Neolamprologus pulcher as model species. N. pulcher did not only differentiate between images of conspecifics, predators and herbivorous fish, but they also showed adequate behavioural responses towards the respective stimulus images as well as towards stimulus individuals of different sizes. Our results indicate that even simple animated still images, which can be produced with minimal technical effort at very low costs, can be used to study detailed behavioural responses towards social and predatory challenges. Thus, this technique opens up intriguing possibilities to manipulate single or multiple visual features of the presented animals by simple digital image-editing and to study their relative importance to the observing fish. We hope to encourage further studies to use animated images as a powerful research tool in behavioural and evolutionary studies.
Full-text available
Article
This work investigates assortative mating and convergence in personality and their effect on marital satisfaction. Measures of personality were collected from a sample of married couples before they met and twice after they were married. Results showed evidence for assortative mating but not for convergence in an average couple. Similarity and convergence in personality predicted later marital satisfaction. These results indicate that similarity and convergence in psychological characteristics may benefit relationships and that while spouses may choose partners with similar personalities they do not become more like their partners in the early part of their marriage.
Full-text available
Article
Maximum likelihood or restricted maximum likelihood (REML) estimates of the parameters in linear mixed-effects models can be determined using the lmer function in the lme4 package for R. As for most model-fitting functions in R, the model is described in an lmer call by a formula, in this case including both fixed- and random-effects terms. The formula and data together determine a numerical representation of the model from which the profiled deviance or the profiled REML criterion can be evaluated as a function of some of the model parameters. The appropriate criterion is optimized, using one of the constrained optimization functions in R, to provide the parameter estimates. We describe the structure of the model, the steps in evaluating the profiled deviance or REML criterion, and the structure of classes or types that represents such a model. Sufficient detail is included to allow specialization of these structures by users who wish to write functions to fit specialized linear mixed models, such as models incorporating pedigrees or smoothing splines, that are not easily expressible in the formula language used by lmer.
Full-text available
Article
Research on animal personality variation has been burgeoning in the last 20 years but surprisingly few studies have investigated personalities in invertebrate species although they make up 98% of all animal species. Such lack of invertebrate studies might be due to a traditional belief that invertebrates are just ‘minirobots’. Lately, studies highlighting personality differences in a range of invertebrate species have challenged this idea. However, the number of invertebrate species investigated still contrasts markedly with the effort that has been made studying vertebrates, which represent only a single subphylum. We describe how investigating proximate, evolutionary and ecological correlates of personality variation in invertebrates may broaden our understanding of personality variation in general. In our opinion, personality studies on invertebrates are much needed, because invertebrates exhibit a range of aspects in their life histories, social and sexual behaviours that are extremely rare or absent in most studied vertebrates, but that offer new avenues for personality research. Examples are complete metamorphosis, male emasculation during copulation, asexual reproduction, eusociality and parasitism. Further invertebrate personality studies could enable a comparative approach to unravel how past selective forces have driven the evolution of personality differences. Finally, we point out the advantages of studying personality variation in many invertebrate species, such as easier access to relevant data on proximate and ultimate factors, arising from easy maintenance, fast life cycles and short generation times.
Full-text available
Article
Territorial aggression influences fitness and, in monogamous pairs, the behavior of both individuals could impact reproductive success. Moreover, territorial aggression is particularly important in the context of interspecific competition. Tree swallows and eastern bluebirds are highly aggressive, secondary cavity-nesting birds that compete for limited nesting sites. We studied eastern bluebirds at a field site in the southern Appalachian Mountains that has been recently colonized (<40 yr) by tree swallows undergoing a natural range expansion. The field site is composed of distinct areas where bluebirds compete regularly with tree swallows and areas where there is little interaction between the two species. Once birds had settled, we measured how interspecific competition affects the relationship between assortative mating (paired individuals that behave similarly) and reproductive success in eastern bluebirds. We found a strong tendency toward assortative mating throughout the field site. In areas of high interspecific competition, pairs that behaved the most similarly and displayed either extremely aggressive or extremely non-aggressive phenotypes experienced higher reproductive success. Our data suggest that interspecific competition with tree swallows may select for bluebirds that express similar behavior to that of their mate. Furthermore, animal personality may be an important factor influencing the outcome of interactions between native and aggressive, invasive species.
Full-text available
Article
Animal personalities, composed of axes of consistent individual behaviors, are widely reported and can have important fitness consequences. However, despite theoretical predictions that life-history trade-offs may cause and maintain personality differences, our understanding of the evolutionary ecology of personality remains poor, especially in long-lived species where trade-offs and senescence have been shown to be stronger. Furthermore, although much theoretical and empirical work assumes selection shapes variation in personalities, studies exploring the genetic underpinnings of personality traits are rare. Here we study one standard axis of personality, the shy-bold continuum, in a long-lived marine species, the wandering albatross from Possession Island, Crozet, by measuring the behavioral response to a human approach. Using generalized linear mixed models in a Bayesian framework, we show that boldness is highly repeatable and heritable. We also find strong differences in boldness between breeding colonies, which vary in size and density, suggesting birds are shyer in more dense colonies. These results demonstrate that in this seabird population, boldness is both heritable and repeatable and highlights the potential for ecological and evolutionary processes to shape personality traits in species with varying life-history strategies.
Full-text available
Article
Brood defense behaviour of parental Midas cichlids, Amphilophus xiloaensis, was observed in Lake Xiloá, Nicaragua. The research was conducted during two study periods separated by 22 years, 1972-73 and 1995. Role-differentiation was observed between the male and female during brood defense. The male defended the territory from adult conspecifics, while the female defended the brood from predators. These observations were consistent in two different study periods 22 years apart and at two different locations within the lake. Attack rates increased as the brood matured, contradicting laboratory findings on this species. These findings reinforced the use of brood defense behavior as a possible diagnostic tool to differ- entiate sibling species. The pattern of brood care and role differentiation remained stable over many gen- erations, and should be a useful character for distinguishing sibling species.
Full-text available
Article
The convict cichlid fish (Archocentrus nigrofasciatus) has a parental division of roles in which the male spends much of his time defending the territory while the female remains near to the offspring. This division is not obligate because both parents do switch roles for brief periods and, in the absence of the mate, both sexes will perform all roles. We predicted that the division of roles depended on each parent being able to successfully complete its task. If a task could not be completed by a single parent, role specializations would be reduced resulting in a division of labor. That is, both parents would perform the same task. We modified the relative importance of the defensive role by changing the number and location of conspecific intruders. When we increased the number of distant intruders from one to two, we found that the division of roles was unaffected. Neither parent increased its defensive activities, although they did attack both intruders. Furthermore, when females did attack an intruder, it was usually the same intruder being attacked by the male. This too resembled pairs attacking single intruders. We concluded that, for distant intruders, both sexes seemed to invest a fixed amount in protecting the territory and the division of roles remained unchanged when intruder numbers changed. Placing one intruder near to the offspring greatly escalated the amount of time both parents spent attacking the intruder resulting in less time either parent spent near the offspring. A second intruder placed at a greater distance to the offspring was largely ignored by both parents. We believe we succeeded in modifying the division of roles by increasing the importance of one parental task and, in this way, the parental care in the convict cichlid resembled a division of labor around a single task.
Full-text available
Article
A comparison of male and female parental investment patterns is needed before predictions can be generated from parental investment theory. One aspect of parental investment is parental care, therefore behavioral observations were conducted to compare the parental behavior of male and female prairie voles. Females brooded pups more frequently than did males during the first week of pup life and, in the absence of their mates in the nest, brooded pups more frequently throughout the preseparation period (between birth and separation from parents on day 20). Females also licked pups more frequently than did males during the entire preseparation period. Conversely, males spent more time outside the nest throughout the preseparation period. There were no differences between the sexes in the proportion of time spent in indirect parental behaviors such as nest building, food caching, or runway maintenance. These differences in direct parental care combined with a female's energetic investment in gestation and lactation result in greater total parental investment for female than for male prairie voles.
Full-text available
Article
Abstract Assortative mating occurs when there is a correlation (positive or negative) between male and female phenotypes or genotypes across mated pairs. To determine the typical strength and direction of assortative mating in animals, we carried out a meta-analysis of published measures of assortative mating for a variety of phenotypic and genotypic traits in a diverse set of animal taxa. We focused on the strength of assortment within populations, excluding reproductively isolated populations and species. We collected 1,116 published correlations between mated pairs from 254 species (360 unique species-trait combinations) in five phyla. The mean correlation between mates was 0.28, showing an overall tendency toward positive assortative mating within populations. Although 19% of the correlations were negative, simulations suggest that these could represent type I error and that negative assortative mating may be rare. We also find significant differences in the strength of assortment among major taxonomic groups and among trait categories. We discuss various possible reasons for the evolution of assortative mating and its implications for speciation.
Full-text available
Article
Animals within a population differ consistently in behavior over time and/or across conditions. A general question is how such differences referred to as personalities are maintained through evolution. One suggested mechanism is a nonrandom mate choice, which has been supported in species in which mate choice associates with direct material benefits. Much less is known about mating patterns and personality in species where males provide only sperm and in which the benefits of female choice are based only on good and/or compatible genes. The bridge spider Larinioides sclopetarius Clerck (Araneidae) exhibits heritable between-individual differences in intrasex aggressiveness. We studied mating probabilities by aggressiveness type of both sexes, and success in sperm competition of aggressive versus nonaggressive males. We staged trials that resemble field conditions: 4 males (2 aggressive and 2 nonaggressive) had simultaneous choice between an aggressive and a nonaggressive female. Although there were no differences in initial approaches of male types toward female types, aggressive males mainly mated with aggressive females, and nonaggressive males more likely mated with nonaggressive females. Female aggressiveness type was not related to fecundity, which may be a consequence of equal food supply in the laboratory. However, in double-mating trials using the sterile-male technique to measure paternity of aggressive versus nonaggressive males, we found that sons of aggressive parents fathered relatively more offspring. We conclude that assortative mating by aggressiveness type might maintain between-individual differences in aggressiveness in L. sclopetarius.
Full-text available
Article
A major challenge in behavioural and evolutionary ecology is to understand the evolution and maintenance of consistent behavioural differences among individuals within populations, often referred to as animal ‘personalities’. Here, we present evidence suggesting that sexual selection may act on such personality differences in zebra finches (Taeniopygia guttata), as females seem to choose males on the basis of their exploratory behaviour per se, while taking into account their own personality. After observing a pair of males, whose apparent levels of exploration were experimentally manipulated, females that exhibited low-exploratory tendencies showed no preference during mate choice for males that had appeared to be either ‘exploratory’ or ‘unexploratory’. In contrast, intermediate and highly exploratory females preferred apparently exploratory males over apparently unexploratory ones. Our results suggest that behavioural or genetic compatibility for personality traits might be important for mate choice, at least for exploratory individuals.
Full-text available
Article
Although behavioural plasticity should be an advantage in a varying world, there is increasing evidence for widespread stable individual differences in the behaviour of animals: that is, [`]personality'. Here we provide evidence suggesting that sexual selection is an important factor in the evolution of personality in species with biparental care. We carried out a cross-fostering breeding experiment on zebra finches, Taeniopygia guttata, and found that parental personality traits and the combination of personalities within breeding pairs had positive effects on correlates of (foster) offspring fitness (body mass and condition). Furthermore, these nongenetic parental effects were pervasive and carried over into the next generation. Our results suggest that similarity in behavioural traits of biparental species can have important, long-lasting effects on reproductive success, probably because of reduced sexual conflict over the provision of parental investment.
Full-text available
Article
In most biparental, substrate-brooding species of cichlid fishes, female and male roles differ. Females are usually more involved in direct care of the young while males spend more time away patrolling the territory. This study tested the flexibility of these sex roles with removal experiments in the convict cichlid, Cichlasoma nigrofasciatum. When males were removed, female fanning activity increased. When females were removed, males spent more time fanning and less time away from the brood. Other behavioural variables (frequency of digging, mouthing, foraging and retrieving) were not affected. Being alone or paired during a first breeding episode did not affect parental behaviour during a subsequent episode in which all fish were paired. Observations were carried out during the day and at night, and nocturnal fanning of fry is reported here for the first time. Female role appears less flexible than male role, as befits the more direct care normally given by females.
Full-text available
Article
When an individual is repeatedly observed or tested in the same context, it does not always express the same behaviour. Intraindividual variability (IIV) refers to the short-term, unpredictable, reversible variation in behaviour that often occurs in this situation. Although individual differences in IIV have been well documented in humans, this topic has been virtually ignored by researchers studying other animals. Here, we review evidence from humans and animals that IIV can vary in important ways across individuals (e.g. as a function of age or prior experience) and that individual differences in IIV may be related to differences in performance. However, most statistical models currently used to study individual differences in behaviour in animals rely on the assumption that IIV does not vary across individuals. Using ‘boldness’ data for hermit crabs, Pagurus bernhardus, and Ward's damselfish, Pomacentrus wardi, we show how to measure IIV when behaviour systematically changes over a series of obs
Full-text available
Article
A behavioral syndrome is a suite of correlated behaviors expressed either within a given behavioral context (e.g., correlations between foraging behaviors in different habitats) or across different contexts (e.g., correlations among feeding, antipredator mating, aggressive, and dispersal behaviors). For example, some individuals (and genotypes) might be generally more aggressive, more active or bold, while others are generally less aggressive, active or bold. This phenomenon has been studied in detail in humans, some primates, laboratory rodents, and some domesticated animals, but has rarely been studied in other organisms, and rarely examined from an evolutionary or ecological perspective. Here, we present an integrative overview on the potential importance of behavioral syndromes in evolution and ecology. A central idea is that behavioral correlations generate tradeoffs; for example, an aggressive genotype might do well in situations where high aggression is favored, but might be inappropriately aggr
Full-text available
Article
For the past 25 years NIH Image and ImageJ software have been pioneers as open tools for the analysis of scientific images. We discuss the origins, challenges and solutions of these two programs, and how their history can serve to advise and inform other software projects.
Full-text available
Article
Male mate choice has evolved in many species in which female fecundity increases with body size. In these species, males are thought to have been selected to favour mating with large females over smaller ones, thereby potentially increasing their reproductive success. While male mate choice is known to occur, it is less well studied than female mate choice and little is known about variation in mating preference among individual males. Here, we presented individual male eastern mosquitofish (Gambusia holbrooki) with paired females that differed in body size, and we quantified their mate preference on two consecutive days, allowing us to assess repeatability of preferences expressed. When males were allowed to view paired stimulus females, but not to acquire chemical or tactile cues from them, they exhibited a strong preference for large females over smaller ones. However, individual males were not consistent in the strength of their preference and repeatability was not significant. When individual males were allowed to fully interact with pairs of females, the males again exhibited a preference for large females over smaller ones, as revealed by a greater number of attempted copulations with large females than with smaller ones. In the latter social context, individual male preference was significantly repeatable. These results indicate that male eastern mosquitofish from our Florida study population possess, on average, a mating preference for larger females and that this preference is repeatable when males socially interact freely with females. The significant repeatability for mating preference, based on female body size, obtained for male mosquitofish in the current study is consistent with the presence of additive genetic variation for such preferences in our study population and thus with the opportunity for the further evolution of large body size in female mosquitofish through male mate choice.
Full-text available
Article
Individual humans, and members of diverse other species, show consistent differences in aggressiveness, shyness, sociability and activity. Such intraspecific differences in behaviour have been widely assumed to be non-adaptive variation surrounding (possibly) adaptive population-average behaviour. Nevertheless, in keeping with recent calls to apply Darwinian reasoning to ever-finer scales of biological variation, we sketch the fundamentals of an adaptive theory of consistent individual differences in behaviour. Our thesis is based on the notion that such ‘personality differences’ can be selected for if fitness payoffs are dependent on both the frequencies with which competing strategies are played and an individual's behavioural history. To this end, we review existing models that illustrate this and propose a game theoretic approach to analyzing personality differences that is both dynamic and state-dependent. Our motivation is to provide insights into the evolution and maintenance of an apparently common animal trait: personality, which has far reaching ecological and evolutionary implications.
Full-text available
Article
Studies of the fitness consequences of behavioral types often focus on isolated behaviors and ignore potential across-context correlations that may affect fitness. This approach leads to heterogeneous results across studies because correlations themselves may be adaptive in populations under significant predation pressure. We quantified suites of behaviors in 4 different contexts and identified a consistent behavioral syndrome in a population of Trinidadian guppies (Poecilia reticulata). We then measured fitness effects of the correlated behaviors that made up this syndrome and found that more active, bold, and exploratory individuals survived longer when exposed to a predator. Behavioral syndromes may, therefore, be advantageous in populations under significant predation risk if an individual's behavior in the presence of a predator is an honest signal of escape abilities. Interestingly, we also found a significant effect of the individual cichlids (Aequidens pulcher) used as predators in our experiments. We suggest that future studies should test whether interactions between predator behavior and prey behavioral types maintain behavioral variation. Copyright 2010, Oxford University Press.
Article
Experimental individuals are frequently marked with coloured tags for individual identification. Except for birds, the consequences of such artificial tagging on mate choice have been rarely investigated even though individuals often prefer naturally brightly coloured or symmetrically ornamented mates. We tested whether differently coloured Visible Implant Elastomer (VIE) tags influence female mate choice in rainbow kribs, Pelvicachromis pulcher. Females were allowed to simultaneously choose between a control and a VIE-marked male. The VIE-marked male carried two tags of the same colour (red, blue, green or white) set symmetrically or asymmetrically. Females did not show a preference for or avoidance of males carrying any of the colours compared to control males, no matter if the tags had been set symmetrically or asymmetrically. Although we found no discrimination for or against colour-tags, we highlight the importance of considering potential influences of colour-marks on mate choice in behavioural and evolutionary studies.
Article
1.Understanding patterns of non-random mating is central to predicting the consequences of sexual selection. Most studies quantifying assortative mating focus on testing for correlations among partners’ phenotypes in mated pairs. Few studies have distinguished between assortative mating arising from preferences for similar partners (expressed by all or a subset of the population), versus from phenotypic segregation in the environment. Also, few studies have assessed the robustness of assortative mating against temporal changes in social conditions.
Article
The effect of two environmental variables, hunger level (fed or not fed before behavioural assays) and time of day (morning or afternoon), on the boldness and aggressiveness of male and female zebrafish Danio rerio, was tested. The results showed that neither hunger level nor time of testing influenced boldness in males and females, but hunger level significantly affected aggression in females when compared with males. © 2015 The Fisheries Society of the British Isles.
Article
(1) Parent male and female great tits and blue tits (Parus major and P. caeruleus) were removed when their nestlings were at various ages and the breeding success, development of the nestlings and the change of foraging behaviour were analysed. (2) There was no significant difference in the survival of blue tit nestlings more than 6 days old and great tit nestlings older than 8 days, whether they were fed by widows or two parents (control nests). This crucial point coincides with the time when nestlings reach approximately half of their maximum weight. All nestlings younger than 3-4 days old being fed by widowed males died, and there was a significant difference in nestling mortality between control nests and those of single parents widowed before 6 and 8 days old for the blue tits and great tits respectively. (3) In first broods the mortality of the nestlings of widowed blue tits was higher than that of great tits. In second broods this relationship was reversed; changes in the environment as the season progresses may affect the breeding success of the blue tit less than the great tit. (4) Both sexes of the two species increased their feeding frequency and the number of changes of departure direction after they became widows. The higher feeding frequency was apparently stimulated by more frequent begging of the hungry nestlings. The diversity of the food delivered by widowed parents increased during the 3-4 h after their mates were removed. The feeding frequency and the change of foraging patches by the widowed parents were determined jointly by the food source and the immediate demands of the nestlings. (5) The body weight of the widowed parents was significantly lower than that of the parents feeding with their mates.
Article
Parenting behaviors, such as the provisioning of food by parents to offspring, are known to be highly responsive to changes in environment. However, we currently know little about how such flexibility affects the ways in which parenting is adapted and evolves in response to environmental variation. This is because few studies quantify how individuals vary in their response to changing environments, especially social environments created by other individuals with which parents interact. Social environmental factors differ from nonsocial factors, such as food availability, because parents and offspring both contribute and respond to the social environment they experience. This interdependence leads to the coevolution of flexible behaviors involved in parenting, which could, paradoxically, constrain the ability of individuals to rapidly adapt to changes in their nonsocial environment.
Article
Nest attendance by male and female meadow voles, Microtus pennsylvanicus , was monitored in 24-h recordings. Fathers housed with mothers and their pups, but with no other adults present, were in the natal nest for much of the observation period. When unfamiliar males were present, instead of, or in addition to, the fathers, females prevented the unfamiliar males from entering the natal nest, and showed reduced tolerance to the fathers' attempts at nest entry. Females housed with unfamiliar males were the only voles to spend more time in the nest at night than during the day, which may be related to the only instance of infanticide occurring when an unfamiliar male successfully entered the nest at night. The introduction of an oestrous female did not reduce the amount of time the father spent in the nest, although several fathers mated with the oestrous females. In another experiment, females were found to be temporarily less tolerant of fathers that were removed during pregnancy and returned after the pups were born, but after renewed contact, the females allowed the males to enter the nest. Fathers tested in the absence of mothers spent a substantial portion of the test time with pups, and effectively prevented unfamiliar males from gaining access to their pups. These results were related to the seasonal changes in nest sharing in meadow voles, suggesting that male reproductive tactics should be flexible to accommodate changes in mating opportunities and changes in the value of biparental care.
Article
Boldness and aggressiveness are two behavioural traits that have received extensive attention in the field of animal behaviour. However, relatively little is known about how these traits are maintained in populations and the fitness of individuals that exhibit them. We tested the effect of boldness and aggressiveness on the reproductive success of zebrafish, Danio rerio. Using behavioural tests, we established groups of males that varied consistently in their boldness (bold, middling and shy) as well as groups of males that differed in their aggressiveness (aggressive, middling and nonaggressive) and paired them with randomly selected females. We found no difference in the total number of eggs laid by females mated to bold or aggressive males. However, the number of fertilized eggs differed, with the boldest and the most aggressive males fertilizing more eggs than the other groups. Furthermore, the proportion of fertilized eggs differed between groups. These results show that an individual's reproductive fitness can be associated with behavioural variations in boldness and aggressiveness.
Article
Reversed sexual size dimorphism in avian species (females larger than males) may be an adaptive consequence of different roles of males and females in parental care. We examined the alleged division of labour in two-chick broods of the blue-footed booby, using behavioural observation and frequent weighing of chicks. In the first week of parental care, males and females Fed broods at similar frequencies and provided similar masses of food, but females brooded more than males when broods were 5.10 d old. Subsequently, females provided a greater mass of food and frequency of feeds than males until chicks were at least 35 d old (mass) and 60 d old frequency), while attending the brood for just as much time as males until chicks were at least 35 d old. Males and females did nor differ in the tendency to feed frequency and mass the first-hatched-chick differentially. In nearly all components of parental care examined here. and in other studies, the female's contribution is equal to or greater than the male's. Only in clutch attendance and nest defence does the male contribute more than the Female, bur his small size seems unlikely to enhance performance in these activities. Overall, small size appears potentially to limit male provisioning of the brood, and is unlikely to be an adaptation For division of labour in parental care. This result casts doubt on the relevance of the division-of-labour hypothesis for adult size dimorphism.
Article
In the biparental convict cichlid fish, Archocentrus nigrofasciatum, males and females both spend time defending their territory and their offspring, but the typically larger male parent spends more time defending the territory and the female spends more time with the offspring. Because size correlates with a convict cichlid's ability to win a fight, the larger male parent has a clear advantage in repelling intruders compared with his smaller female mate. We tested the hypothesis that male and female convict cichlids accept their parental roles as a result of their relative sizes, rather than inherent sex differences (e.g. females are more nurturing). We allowed pairs to form in which one member was smaller or larger than the other member, or of the same size (both small Z 50-55 mm; both large Z 70-75 mm), thus producing four pairing types. During the 5-day stationary larval stage, we subjected each breeding pair each day to a conspecific intruder that was either larger or smaller than one of the parents, or of the same size. Male and female parents adjusted their parental roles based on the size of their mates and/or the size of the intruder. Large parents displayed more defensive behaviour than small parents, regardless of sex. Male parents responded to increased threat (i.e. increasing intruder size) by increasing their defensive behaviour, but only until intruder size matched their own size, after which defensive effort decreased. Large female parents similarly responded to increased threat by increasing their defensive behaviour, but only to support their smaller mates (i.e. they did not independently attack the intruder). Larger females also showed a corresponding reduction in time spent near the offspring. Small males, in contrast, showed only a marginal increase in their time with the offspring. We conclude that the female has a more flexible parental role and, when her relative abilities change, she is more likely to expand her parental roles.
Article
The use of both linear and generalized linear mixed-effects models (LMMs and GLMMs) has become popular not only in social and medical sciences, but also in biological sciences, especially in the field of ecology and evolution. Information criteria, such as Akaike Information Criterion (AIC), are usually presented as model comparison tools for mixed-effects models. The presentation of variance explained' (R2) as a relevant summarizing statistic of mixed-effects models, however, is rare, even though R2 is routinely reported for linear models (LMs) and also generalized linear models (GLMs). R2 has the extremely useful property of providing an absolute value for the goodness-of-fit of a model, which cannot be given by the information criteria. As a summary statistic that describes the amount of variance explained, R2 can also be a quantity of biological interest. One reason for the under-appreciation of R2 for mixed-effects models lies in the fact that R2 can be defined in a number of ways. Furthermore, most definitions of R2 for mixed-effects have theoretical problems (e.g. decreased or negative R2 values in larger models) and/or their use is hindered by practical difficulties (e.g. implementation). Here, we make a case for the importance of reporting R2 for mixed-effects models. We first provide the common definitions of R2 for LMs and GLMs and discuss the key problems associated with calculating R2 for mixed-effects models. We then recommend a general and simple method for calculating two types of R2 (marginal and conditional R2) for both LMMs and GLMMs, which are less susceptible to common problems. This method is illustrated by examples and can be widely employed by researchers in any fields of research, regardless of software packages used for fitting mixed-effects models. The proposed method has the potential to facilitate the presentation of R2 for a wide range of circumstances.
Article
Behavioural traits that are consistent over time and in different contexts are often referred to as personality traits. These traits influence fitness because they play a major role in foraging, reproduction and survival, and so it is assumed that they have little or no additive genetic variance and, consequently, low heritability because, theoretically, they are under strong selection. Boldness and aggressiveness are two personality traits that have been shown to affect fitness. By crossing single males to multiple females, we estimated the heritability of boldness and aggressiveness in the zebrafish, Danio rerio. The additive genetic variance was statistically significant for both traits and the heritability estimates (95 % confidence intervals) for boldness and aggressiveness were 0.76 (0.49, 0.90) and 0.36 (0.10, 0.72) respectively. Furthermore, there were significant maternal effects accounting for 18 and 9 % of the proportion of phenotypic variance in boldness and aggressiveness respectively. This study shows that there is a significant level of genetic variation in this population that would allow these traits to evolve in response to selection.
Article
Both parents of the monogamous Texas cichlid (Cichlasoma cyanoguttatum) participate in offspring care and territorial defense. These activities are typically synchronized, with and without intruders being present, such that only one parent is away from the offspring. During the egg and wriggler stage, the male spends more time patrolling the territory while the female devotes more time to offspring care. During the fry stage, both parents tend to remain with the offspring. Either sex can rear the offspring in the absence of the mate. With the removal of the mate, the female's activities remain largely unchanged while the male (in the absence of the female) becomes female-like. It appears as if the male adjusts his responses according to the activity of the female.
Article
Elaborate visual communication signals characterize many animal lineages. Often sex-limited, these signals are generally assumed to result from sexual selection, and in many cases, their evolution is thought to play a central role in speciation. The co-evolution of male visual signals and female preferences is hypothesized to result in behavioral isolation between divergent lineages; however, for many lineages characterized by elaborate visual signals, the importance of visual differences in behavioral isolation is not well established. Darters (fish genus Etheostoma) are particularly appropriate for examining the role of visual signals in behavioral isolation. They comprise one of the most diverse groups of North American freshwater fish, and nearly every species is characterized by unique nuptial coloration. Multiple darter species co-exist in sympatric populations, indicating that reproductive barriers are central to maintaining these extraordinarily diverse color patterns. This study demonstrates the presence of behavioral isolation between a pair of distinctly colored sympatric darter species, Etheostoma barrenense and Etheostoma zonale, through experimental observations using an artificial stream. In addition, a series of dichotomous mate-choice trials indicate that females prefer conspecific males over heterospecifics based on visual differences alone. We therefore provide the first evidence that visual signals are a critical trait maintaining behavioral isolation in darters, a lineage of fishes with spectacular diversification in visual communication.
Article
There is increasing interest in individual differences in animal behaviour. Recent research now suggests that an individual's behaviour, once considered to be plastic, may be more predictable than previously thought. Here, we take advantage of the large number of studies that have estimated the repeatability of various behaviours to evaluate whether there is good evidence for consistent individual differences in behaviour and to answer some outstanding questions about possible factors that can influence repeat- ability. Specifically, we use meta-analysis to ask whether different types of behaviours were more repeatable than others, and if repeatability estimates depended on taxa, sex, age, field versus laboratory, the number of measures and the interval between measures. Some of the overall patterns that were revealed by this analysis were that repeatability estimates were higher in the field compared to the laboratory and repeatability was higher when the interval between observations was short. Mate pref- erence behaviour was one of the best studied but least repeatable behaviours. Our findings prompt new insights into the relative flexibility of different types of behaviour and offer suggestions for the design and analysis of future research.
Article
In recent years analyzing animal behaviour in light of the social environment has become widely accepted. Especially many mating interactions do not happen in privacy, but in a public arena, raising the question of how this affects the behaviour of both the focal individual and the observing audience individual. We studied in feral guppies whether male preferences for female body size, a correlate of fecundity, are influenced by the presence of another male, the audience. We also studied whether the audience was influenced by the observed interactions. These two aspects are not normally studied together. Furthermore, we were also interested in the question of how long changes in the behaviour of the audience male might last. We found that male preferences measured as nipping/approaches decreased in the presence of an audience. Furthermore, the audience males showed no preference for larger females when tested right after the interaction with the focal male, but returned to the typical preference for larger females after 24 h. Our study highlights the relevance of the social conditions under which mating decisions are being made.
Article
We report two independent cases of female preferences for novel male traits in two species of poeciliid sh, Poecilia latipinna and Poecilia mexicana. In both cases the preference predates the occurrence of the trait, lending strong support to the pre-existing bias hypotheses. This support is independent of the assumptions associated with phylogenetic inference. Unlike the two sexual species, the unisexual hybrid P. formosa had no detectable preference for the novel male traits.
Article
In six horses, a 0.05% solution of chlorhexidine diacetate was used to lavage one tarsocrural joint; the contralateral control joint was lavaged with lactated Ringer's solution. Horses were evaluated daily for lameness. Synovial fluid samples were collected on days 1, 4, and 8 for determination of protein concentration, total and differential leukocyte counts, and mucin clot formation. After death on day 8, synovium and osteochondral samples were collected from the tarsocrural joints for examination of morphology and proteoglycan staining. Lavage with chlorhexidine solution caused lameness that was reduced but still evident at day 8. Synovial protein concentration was significantly increased by chlorhexidine lavage; the greatest increase occurred on day 1. Joint lavage increased synovial leukocyte counts on day 1, primarily by increasing polymorphonuclear (PMN) cell counts. Although total synovial leukocyte counts returned to normal by day 4, PMN cell counts remained elevated through day 8; PMN cell counts for chlorhexidine-lavaged joints were typically twice that of control joints. Chlorhexidine lavage caused synovial ulceration, inflammation, and abundant fibrin accumulation. Consistent differences in proteoglycan staining were not detected between control and chlorhexidine-lavaged joints. Joint lavage with 0.05% chlorhexidine diacetate, the lowest known bactericidal concentration, is not recommended for equine joints.
Article
Guppies (Poecilia reticulata) have a promiscuous mating system in which female choice for brightly coloured males plays an important role. Consequently, much research on guppies has examined how mate choice by females has lead to the evolution of male colour patterns. Much less attention has been devoted to mate choice by males in this species. In this study, we show that male guppies are choosy when selecting a female to associate with, significantly preferring the larger female when presented with two females that differed by ≥2 mm in standard length (SL). The strength of their preference for each female increased with absolute female size. The relative sizes of the females, however, also influenced male mating preferences: males showed stronger preferences for the larger female as the difference in SL between the two females increased. Such a preference for larger females is not unexpected as fecundity generally increases with body size in female fish. Thus, males choosing to mate with the larger female should have higher reproductive success. An apparent, but non-significant anomaly, whereby males appear to prefer the smaller of the two females when the difference between female SL was <4 mm, deserves further investigation.