(1). Master data file (in Excel.xls format) in support of the paper by Pusiak, Auld and Godin (20... more (1). Master data file (in Excel.xls format) in support of the paper by Pusiak, Auld and Godin (2020) in Animal Behaviour. Original raw data for mating preferences of individual focal male guppies tested in four independent experimental treatments. The data collected are organized into discrete columns (representing variables) in Sheet 1, and the definition of each column header title can be found in Sheet 2. (2) Data File (in Excel.xls format) in support of the paper by Pusiak, Auld and Godin (2020) in Animal Behaviour. Subset of original raw data on the mating preferences of individual focal male guppies for either Small or Large females in four independent experimental treatments. The data collected are organized into discrete columns (representing variables) in Sheet 1, and the definition of each column header title can be found in Sheet 2.
Although mate choice by males does occur in nature, our understanding of its importance in drivin... more Although mate choice by males does occur in nature, our understanding of its importance in driving evolutionary change remains limited compared with that for female mate choice. Recent theoretical models have shown that the evolution of male mate choice is more likely when individual variation in male mating effort and mating preferences exist and positively covary within populations. However, relatively little is known about the nature of such variation and its maintenance within natural populations. Here, using the Trinidadian guppy (Poecilia reticulata) as a model study system, we report that mating effort and mating preferences in males, based on female body length (a strong correlate of fecundity), positively covary and are significantly variable among subjects. Individual males are thus consistent, but not unanimous, in their mate choice. Both individual mating effort (including courtship effort) and mating preference were significantly repeatable. These novel findings support...
Female mate-choice copying is a social learning phenomenon whereby a female's observation of a su... more Female mate-choice copying is a social learning phenomenon whereby a female's observation of a successful sexual interaction between a male and another female increases her likelihood of subsequently preferring that male. Although mate-choice copying has been documented in several vertebrate species, to our knowledge it has not yet been investigated in insects. Here, we investigated whether female matechoice copying occurs in the fruit fly Drosophila serrata, a model system for the study of mate preferences and the sexual selection they generate. We used two complementary experiments in which focal females were given a choice between two males that differed in either their apparent (as determined visually by the focal female) or actual recent mating success. Mate-choice copying was evaluated by testing whether focal females mated more frequently with the 'preferred' male as opposed to the other male. In both experiments, however, we found no evidence for mate-choice copying. We discuss possible reasons for the apparent absence of mate-choice copying in this species.
Mobile young under parental care have a high potential for intermixing with other broods, which p... more Mobile young under parental care have a high potential for intermixing with other broods, which potentially increases the costs to the foster parents. Here, we examined for the first time the genetic composition of wild-caught broods of the convict cichlid (Amatitlania siquia), a socially monogamous biparental fish, for evidence of brood mixing and adoption. Our microsatellite genotyping data revealed that 79% of broods contained adopted young. Moreover, 25% of broods contained adopted sibsets likely arising from extra-pair matings, a phenomenon hitherto not documented for this species. Overall, adopted foreign fry and host fry in mixed broods were generally different in body length, as would be expected if they have different parents. However, fry from possible extra-pair matings were similar in body length to host fry, suggesting that they are of similar age. Our results are important because they reveal a very high prevalence and degree of brood mixing, and indicate that social m...
The project was conceived by Algera and Cooke. Field work was completed by Algera, Brownscombe, a... more The project was conceived by Algera and Cooke. Field work was completed by Algera, Brownscombe, and Zolderdo. Cortisol analyses were conducted by Gilmour and Lawrence. Data analysis and interpretation was conducted by Algera, Brownscombe, and Cooke. Manuscript was written by Algera, and all co-authors contributed with feedback.
Whether hiding from predators, or avoiding battlefield casualties, camouflage is widely employed ... more Whether hiding from predators, or avoiding battlefield casualties, camouflage is widely employed to prevent detection. Disruptive coloration is a seemingly well-known camouflage mechanism proposed to function by breaking up an object's salient features (for example their characteristic outline), rendering objects more difficult to recognize. However, while a wide range of animals are thought to evade detection using disruptive patterns, there is no direct experimental evidence that disruptive coloration impairs recognition. Using humans searching for computer-generated moth targets, we demonstrate that the number of edge-intersecting patches on a target reduces the likelihood of it being detected, even at the expense of reduced background matching. Crucially, eye-tracking data show that targets with more edge-intersecting patches were looked at for longer periods prior to attack, and passed-over more frequently during search tasks. We therefore show directly that edge patches en...
Proceedings of the Royal Society B: Biological Sciences, 2014
Phosphorus has been identified as an important determinant of nutrition-related biological variat... more Phosphorus has been identified as an important determinant of nutrition-related biological variation. The macronutrients protein (P) and carbohydrates (C), both alone and interactively, are known to affect animal performance. No study, however, has investigated the importance of phosphorus relative to dietary protein or carbohydrates, or the interactive effects of phosphorus with these macronutrients, on fitness-related traits in animals. We used a nutritional geometry framework to address this question in adult field crickets ( Gryllus veletis ). Our results showed that lifespan, weight gain, acoustic mate signalling and egg production were maximized on diets with different P : C ratios, that phosphorus did not positively affect any of these fitness traits, and that males and females had different optimal macronutrient intake ratios for reproductive performance. When given a choice, crickets selected diets that maximized both lifespan and reproductive performance by preferentially ...
The potential influence of social familiarity in shoal-choice decisions was investigated in two s... more The potential influence of social familiarity in shoal-choice decisions was investigated in two sympatric species of north temperate fishes, juvenile banded killifish Fundulus diaphanus and juvenile bluegill sunfish Lepomis macrochirus. Groups of socially familiar and unfamiliar conspecifics were formed in the laboratory using wild-caught fishes. Juvenile F. diaphanus demonstrated a strong preference for familiar conspecific shoalmates, whereas juvenile L. macrochirus exhibited no preference for either unfamiliar or familiar conspecific shoalmates. The differential influence of familiarity on shoalmate choice in juveniles of these two species could be due to their different ecologies, local population densities and life histories.
1. The distribution of transmittable parasites in group-living host species has been investigated... more 1. The distribution of transmittable parasites in group-living host species has been investigated in a number of studies. However, little is known about the distribution of parasites with indirect life cycles in this context. This study investigates the relationship between parasitism and ...
Animals are known to exhibit 'personality'; that is, individual differences in behaviour that are... more Animals are known to exhibit 'personality'; that is, individual differences in behaviour that are consistent across time and ⁄ or situations. One axis of personality of particular importance for behavioural ecology is boldness, which can be defined as the tendency of an individual to take risks. The relationship between individual personality and fitness correlates, particularly those involved in reproduction, remains largely unexplored. In the current study, we used female Eastern mosquitofish (Gambusia holbrooki) to ascertain whether certain reproductive traits (e.g. stage of pregnancy, fecundity) are correlated with individual personality in two wild populations in New South Wales, Australia. To quantitatively assess this relationship, we tested individual fish for their level of boldness, as measured by their latency to exit a refuge and tendency to shoal in a novel environment. We also quantified individual differences in general activity and tendency to swim near the water surface and substratum. For both populations taken together, bolder individuals tended to be smaller, relatively less fecund (when taking body size into account), and spent more time near the water surface than near the substratum compared with timid individuals. Individual boldness was not correlated with either general activity or stage of pregnancy. To our knowledge, our study characterizes for the first time a relationship between an individual personality trait (boldness) and a reproductive fitness correlate (fecundity) in fishes.
Many fish species exhibit size-assortative shoaling, which is often thought to be driven by preda... more Many fish species exhibit size-assortative shoaling, which is often thought to be driven by predation risk. Recent fieldwork has revealed that guppies (Poecilia reticulata) are more size assorted in high-predation populations than in low-predation ones. However, size assortment does nonetheless occur in some low-predation populations, suggesting that predation is unlikely the sole driving force behind size-assortment. Here, we investigated in the laboratory the potential role of active choice in size-assortative shoaling in wild-caught female guppies originating from two populations of the same river system in Trinidad. Small or large focal females from each population were offered a binary choice of shoaling with either four small female conspecifics or four large ones. Observed shoaling preferences depended on the body size of the focal fish, suggesting phenotype-mediated conflict over group composition. Large focal fish preferred to shoal with the size-matched stimulus shoal of large fish. In contrast, small focal fish did not shoal assortatively but also preferred to shoal with larger females. Our results suggest that sizeassortative shoaling in female guppies is likely to be due to factors other than active choice, such as habitat segregation and sexual harassment.
Theory predicts that individuals within social groups should be more similar (less variable) phen... more Theory predicts that individuals within social groups should be more similar (less variable) phenotypically than individuals between groups. We tested this hypothesis by comparing the variability of certain phenotypic characters (body size, parasite load) of individual fish within and between sampled shoals with the phenotypic variability of randomly constituted shoals of the same size. We caught 34 entire fish shoals in a lake, and for each shoal member, we identified the species, measured its body length, and counted the number of black spots (indicating the presence of a parasitic trematode worm) visible through their skin. We also recorded two habitat characteristics, water depth and distance to cover, at the location where each of the 34 shoals was caught to ascertain whether (and to which degree) the spatial distributions of different fish species and fish size classes were determined by certain habitat characteristics. A comparison between the observed and the randomly assorted shoals (obtained through computer simulations) revealed that fish at our study site exhibited'a significant association with conspecifics and with individuals of similar body size (within and across species); that is, shoals were assorted by species and by individual body size. Parasite-assortative shoaling was not observed. Different species (and to a lesser degree different size classes within species) showed a tendency to occur in different microhabitats. Nevertheless, despite some degree of habitat segregation, there remained considerable spatial overlap between the different species and fish body size classes. Furthermore, given the spatial proximity of different habitats and the relatively weak habitat association of most species, we therefore suggest that active shoal choice by individual fish was the most important determinant of shoal composition.
Canadian Journal of Fisheries and Aquatic Sciences, 2011
Size-selective harvesting associated with commercial and recreational fishing practices has been ... more Size-selective harvesting associated with commercial and recreational fishing practices has been shown to alter life history traits through a phenomenon known as fishing-induced evolution. This phenomenon may be a result of selection pathways targeting life-history traits directly or indirectly through correlations with behavioral traits. Here, we report on the relationship between individual differences in behavior and capture technique (beach seining versus angling) in wild-caught juvenile bluegill sunfish ( Lepomis macrochirus ). Both fish caught by using a seine net (seined) and fish caught by using a lure (angled) were individually tested under standardized laboratory conditions for their boldness, water-column use, and general activity. Observed inter-individual differences in boldness were strongly correlated with method of capture in the wild. Fish caught by angling were more timid and had fewer ectoparasites than fish caught using a seine net. However, this relationship did...
Following exposure to a predator, socially dominant individuals may reduce their risk of predatio... more Following exposure to a predator, socially dominant individuals may reduce their risk of predation by waiting until subordinates have resumed foraging before doing so themselves. Although such status-related ordering in the resumption of foraging activity has been observed in several bird species, the underlying mechanism(s) facilitating such a delay remains unknown. Social status per se and status-related foraging benefits prior to a threat of predation (i.e., individual hunger level) have both been suggested as possible mechanisms. We tested between these two alternative suggestions using pairs of stream-dwelling juvenile Atlantic salmon, for which the dominant-subordinate relationship was known. Fish were tested at equal and unequal hunger levels. Fish were presented with drifting prey, followed by a predation threat in the form of an aerial predator model. Which fish (i.e., dominant or subordinate) initially resumed foraging activity after exposure to the predator model was recorded. When both fish were at an equal hunger level, the dominant fish was more likely to resume foraging first. When the dominant and subordinate fish differed in their hunger level, the hungrier fish was the first to resume foraging regardless of social status. These results support the conclusion that hunger level, rather than social status per se, determines the order in which juvenile Atlantic salmon resume foraging after exposure to a predator.
In recent years, evidence for interindividual variation in ''personality'' within animal populati... more In recent years, evidence for interindividual variation in ''personality'' within animal populations has been accumulating. Personality is defined as consistency in an individual's behavioral responses over time and/or across situations. One personality trait that has potentially far-reaching implications for behavioral ecology, and may provide insight into the mechanisms by which consistent behavioral correlations arise, is that of boldness. Boldness is defined as the tendency of an individual to take risks and be exploratory in novel contexts. Using the framework of behavioral syndromes, we tested for individual differences in boldness in the laboratory among field-caught juvenile bluegill sunfish (Lepomis macrochirus) within and across the contexts of exploratory behavior, activity, and risk taking (e.g., antipredator) behavior. After such testing, individuals were tagged and returned to their lake of origin as part of a mark-recapture study testing for the repeatability of individual differences in boldness. Here, we report strong and consistent individual differences in boldness within and across all 3 behavioral contexts. Additionally, we observed that at least some boldness behaviors were repeatable after a 1-3 month recapture period. This study provides novel evidence for a boldness syndrome in sunfish, as well as insight into how behavioral types (e.g., shy/bold) may evolve and be maintained in natural populations.
Intermittent locomotion, characterized by moves interspersed with pauses, is a common pattern of ... more Intermittent locomotion, characterized by moves interspersed with pauses, is a common pattern of locomotion in animals, but its ecological and evolutionary significance relative to continuous locomotion remains poorly understood. Although many studies have examined individual differences in both intermittent locomotion and boldness separately, to our knowledge, no study to date has investigated the relationship between these 2 traits. Characterizing and understanding this relationship is important, as both locomotion and boldness are associated with several ecologically relevant behaviors such as foraging, mating, predator evasion, exploration, and dispersal. Here, we report on individual differences in boldness (risk-taking behavior) and intermittent locomotion in a novel laboratory environment in field-caught juvenile bluegill sunfish (Lepomis macrochirus). Our results show that juvenile bluegill sunfish exhibited individual-level variation in 2 modes of intermittent locomotion (undulatory and labriform swimming) and that this variation was correlated with differences in their boldness behavior. Generally, bolder individuals spent more time moving fast for longer durations and with shorter pauses than more timid individuals. Neither boldness nor locomotion was correlated with body size or body condition. This study provides the first empirical evidence for a link between an animal ''personality'' trait and intermittent locomotion.
Cichlid fish (Aequidens curvieeps) distributed themselves and allocated their foraging time betwe... more Cichlid fish (Aequidens curvieeps) distributed themselves and allocated their foraging time between two drift food patches in close approximation to the patch profitability ratio, as predicted by the ideal free distribution theory. The fish thereby achieved similar average feeding rates in the two patches, in two of three patch profitability ratio experiments. However, one major assumption of the ideal free model was violated, since individual fish differed in their competitive abilities for limited food resources, which resulted in unequal payoffs among individuals within each patch. Individual variation in feeding rates, and thus in competitive ability, was not related to despotism, but perhaps rather to individual differences in perceptual ability and in the ability to learn which patch was currently the more profitable. The strategy used by the fish to assess patch profitability included sampling available patches. However, individual fish switched (sampled) patches with varying frequency. Sampling had an associated cost, since high-frequency switchers had lower feeding rates on average than low-frequency switchers. Differences in foraging strategy among the fish therefore contributed to the observed inequality in individual payoffs within patches.
Males are generally expected to be discriminating in their choice of mates when females vary in q... more Males are generally expected to be discriminating in their choice of mates when females vary in quality and when under sperm competition from rival males. However, how sperm competition and female quality interact to influence male mating decisions remains poorly understood. Here, we explored the concurrent effects of sperm competition and female body length on male mating decisions in the Trinidadian guppy (Poecilia reticulata) as a model system. We used female body length as a proxy for fecundity and manipulated the relative size difference of paired stimulus females concurrently with sociosexual cues (i.e., presence of rival males) that may predict sperm competition. When all else was equal, males preferred the larger female when the paired females differed considerably in body length. The presence of either 1 or 2 rival males near, and sexually interacting with, the initially preferred female reduced a focal male's preference for that female and increased the probability that he would reverse his initial mate preference. However, focal males were more likely to reverse their initial preference when the females were similar in body length than when they differed considerably in body length after observing initially preferred females interacting with 1 rival male. Our novel results suggest that male guppies simultaneously evaluate sperm competition and female quality when making mating decisions.
(1). Master data file (in Excel.xls format) in support of the paper by Pusiak, Auld and Godin (20... more (1). Master data file (in Excel.xls format) in support of the paper by Pusiak, Auld and Godin (2020) in Animal Behaviour. Original raw data for mating preferences of individual focal male guppies tested in four independent experimental treatments. The data collected are organized into discrete columns (representing variables) in Sheet 1, and the definition of each column header title can be found in Sheet 2. (2) Data File (in Excel.xls format) in support of the paper by Pusiak, Auld and Godin (2020) in Animal Behaviour. Subset of original raw data on the mating preferences of individual focal male guppies for either Small or Large females in four independent experimental treatments. The data collected are organized into discrete columns (representing variables) in Sheet 1, and the definition of each column header title can be found in Sheet 2.
Although mate choice by males does occur in nature, our understanding of its importance in drivin... more Although mate choice by males does occur in nature, our understanding of its importance in driving evolutionary change remains limited compared with that for female mate choice. Recent theoretical models have shown that the evolution of male mate choice is more likely when individual variation in male mating effort and mating preferences exist and positively covary within populations. However, relatively little is known about the nature of such variation and its maintenance within natural populations. Here, using the Trinidadian guppy (Poecilia reticulata) as a model study system, we report that mating effort and mating preferences in males, based on female body length (a strong correlate of fecundity), positively covary and are significantly variable among subjects. Individual males are thus consistent, but not unanimous, in their mate choice. Both individual mating effort (including courtship effort) and mating preference were significantly repeatable. These novel findings support...
Female mate-choice copying is a social learning phenomenon whereby a female's observation of a su... more Female mate-choice copying is a social learning phenomenon whereby a female's observation of a successful sexual interaction between a male and another female increases her likelihood of subsequently preferring that male. Although mate-choice copying has been documented in several vertebrate species, to our knowledge it has not yet been investigated in insects. Here, we investigated whether female matechoice copying occurs in the fruit fly Drosophila serrata, a model system for the study of mate preferences and the sexual selection they generate. We used two complementary experiments in which focal females were given a choice between two males that differed in either their apparent (as determined visually by the focal female) or actual recent mating success. Mate-choice copying was evaluated by testing whether focal females mated more frequently with the 'preferred' male as opposed to the other male. In both experiments, however, we found no evidence for mate-choice copying. We discuss possible reasons for the apparent absence of mate-choice copying in this species.
Mobile young under parental care have a high potential for intermixing with other broods, which p... more Mobile young under parental care have a high potential for intermixing with other broods, which potentially increases the costs to the foster parents. Here, we examined for the first time the genetic composition of wild-caught broods of the convict cichlid (Amatitlania siquia), a socially monogamous biparental fish, for evidence of brood mixing and adoption. Our microsatellite genotyping data revealed that 79% of broods contained adopted young. Moreover, 25% of broods contained adopted sibsets likely arising from extra-pair matings, a phenomenon hitherto not documented for this species. Overall, adopted foreign fry and host fry in mixed broods were generally different in body length, as would be expected if they have different parents. However, fry from possible extra-pair matings were similar in body length to host fry, suggesting that they are of similar age. Our results are important because they reveal a very high prevalence and degree of brood mixing, and indicate that social m...
The project was conceived by Algera and Cooke. Field work was completed by Algera, Brownscombe, a... more The project was conceived by Algera and Cooke. Field work was completed by Algera, Brownscombe, and Zolderdo. Cortisol analyses were conducted by Gilmour and Lawrence. Data analysis and interpretation was conducted by Algera, Brownscombe, and Cooke. Manuscript was written by Algera, and all co-authors contributed with feedback.
Whether hiding from predators, or avoiding battlefield casualties, camouflage is widely employed ... more Whether hiding from predators, or avoiding battlefield casualties, camouflage is widely employed to prevent detection. Disruptive coloration is a seemingly well-known camouflage mechanism proposed to function by breaking up an object's salient features (for example their characteristic outline), rendering objects more difficult to recognize. However, while a wide range of animals are thought to evade detection using disruptive patterns, there is no direct experimental evidence that disruptive coloration impairs recognition. Using humans searching for computer-generated moth targets, we demonstrate that the number of edge-intersecting patches on a target reduces the likelihood of it being detected, even at the expense of reduced background matching. Crucially, eye-tracking data show that targets with more edge-intersecting patches were looked at for longer periods prior to attack, and passed-over more frequently during search tasks. We therefore show directly that edge patches en...
Proceedings of the Royal Society B: Biological Sciences, 2014
Phosphorus has been identified as an important determinant of nutrition-related biological variat... more Phosphorus has been identified as an important determinant of nutrition-related biological variation. The macronutrients protein (P) and carbohydrates (C), both alone and interactively, are known to affect animal performance. No study, however, has investigated the importance of phosphorus relative to dietary protein or carbohydrates, or the interactive effects of phosphorus with these macronutrients, on fitness-related traits in animals. We used a nutritional geometry framework to address this question in adult field crickets ( Gryllus veletis ). Our results showed that lifespan, weight gain, acoustic mate signalling and egg production were maximized on diets with different P : C ratios, that phosphorus did not positively affect any of these fitness traits, and that males and females had different optimal macronutrient intake ratios for reproductive performance. When given a choice, crickets selected diets that maximized both lifespan and reproductive performance by preferentially ...
The potential influence of social familiarity in shoal-choice decisions was investigated in two s... more The potential influence of social familiarity in shoal-choice decisions was investigated in two sympatric species of north temperate fishes, juvenile banded killifish Fundulus diaphanus and juvenile bluegill sunfish Lepomis macrochirus. Groups of socially familiar and unfamiliar conspecifics were formed in the laboratory using wild-caught fishes. Juvenile F. diaphanus demonstrated a strong preference for familiar conspecific shoalmates, whereas juvenile L. macrochirus exhibited no preference for either unfamiliar or familiar conspecific shoalmates. The differential influence of familiarity on shoalmate choice in juveniles of these two species could be due to their different ecologies, local population densities and life histories.
1. The distribution of transmittable parasites in group-living host species has been investigated... more 1. The distribution of transmittable parasites in group-living host species has been investigated in a number of studies. However, little is known about the distribution of parasites with indirect life cycles in this context. This study investigates the relationship between parasitism and ...
Animals are known to exhibit 'personality'; that is, individual differences in behaviour that are... more Animals are known to exhibit 'personality'; that is, individual differences in behaviour that are consistent across time and ⁄ or situations. One axis of personality of particular importance for behavioural ecology is boldness, which can be defined as the tendency of an individual to take risks. The relationship between individual personality and fitness correlates, particularly those involved in reproduction, remains largely unexplored. In the current study, we used female Eastern mosquitofish (Gambusia holbrooki) to ascertain whether certain reproductive traits (e.g. stage of pregnancy, fecundity) are correlated with individual personality in two wild populations in New South Wales, Australia. To quantitatively assess this relationship, we tested individual fish for their level of boldness, as measured by their latency to exit a refuge and tendency to shoal in a novel environment. We also quantified individual differences in general activity and tendency to swim near the water surface and substratum. For both populations taken together, bolder individuals tended to be smaller, relatively less fecund (when taking body size into account), and spent more time near the water surface than near the substratum compared with timid individuals. Individual boldness was not correlated with either general activity or stage of pregnancy. To our knowledge, our study characterizes for the first time a relationship between an individual personality trait (boldness) and a reproductive fitness correlate (fecundity) in fishes.
Many fish species exhibit size-assortative shoaling, which is often thought to be driven by preda... more Many fish species exhibit size-assortative shoaling, which is often thought to be driven by predation risk. Recent fieldwork has revealed that guppies (Poecilia reticulata) are more size assorted in high-predation populations than in low-predation ones. However, size assortment does nonetheless occur in some low-predation populations, suggesting that predation is unlikely the sole driving force behind size-assortment. Here, we investigated in the laboratory the potential role of active choice in size-assortative shoaling in wild-caught female guppies originating from two populations of the same river system in Trinidad. Small or large focal females from each population were offered a binary choice of shoaling with either four small female conspecifics or four large ones. Observed shoaling preferences depended on the body size of the focal fish, suggesting phenotype-mediated conflict over group composition. Large focal fish preferred to shoal with the size-matched stimulus shoal of large fish. In contrast, small focal fish did not shoal assortatively but also preferred to shoal with larger females. Our results suggest that sizeassortative shoaling in female guppies is likely to be due to factors other than active choice, such as habitat segregation and sexual harassment.
Theory predicts that individuals within social groups should be more similar (less variable) phen... more Theory predicts that individuals within social groups should be more similar (less variable) phenotypically than individuals between groups. We tested this hypothesis by comparing the variability of certain phenotypic characters (body size, parasite load) of individual fish within and between sampled shoals with the phenotypic variability of randomly constituted shoals of the same size. We caught 34 entire fish shoals in a lake, and for each shoal member, we identified the species, measured its body length, and counted the number of black spots (indicating the presence of a parasitic trematode worm) visible through their skin. We also recorded two habitat characteristics, water depth and distance to cover, at the location where each of the 34 shoals was caught to ascertain whether (and to which degree) the spatial distributions of different fish species and fish size classes were determined by certain habitat characteristics. A comparison between the observed and the randomly assorted shoals (obtained through computer simulations) revealed that fish at our study site exhibited'a significant association with conspecifics and with individuals of similar body size (within and across species); that is, shoals were assorted by species and by individual body size. Parasite-assortative shoaling was not observed. Different species (and to a lesser degree different size classes within species) showed a tendency to occur in different microhabitats. Nevertheless, despite some degree of habitat segregation, there remained considerable spatial overlap between the different species and fish body size classes. Furthermore, given the spatial proximity of different habitats and the relatively weak habitat association of most species, we therefore suggest that active shoal choice by individual fish was the most important determinant of shoal composition.
Canadian Journal of Fisheries and Aquatic Sciences, 2011
Size-selective harvesting associated with commercial and recreational fishing practices has been ... more Size-selective harvesting associated with commercial and recreational fishing practices has been shown to alter life history traits through a phenomenon known as fishing-induced evolution. This phenomenon may be a result of selection pathways targeting life-history traits directly or indirectly through correlations with behavioral traits. Here, we report on the relationship between individual differences in behavior and capture technique (beach seining versus angling) in wild-caught juvenile bluegill sunfish ( Lepomis macrochirus ). Both fish caught by using a seine net (seined) and fish caught by using a lure (angled) were individually tested under standardized laboratory conditions for their boldness, water-column use, and general activity. Observed inter-individual differences in boldness were strongly correlated with method of capture in the wild. Fish caught by angling were more timid and had fewer ectoparasites than fish caught using a seine net. However, this relationship did...
Following exposure to a predator, socially dominant individuals may reduce their risk of predatio... more Following exposure to a predator, socially dominant individuals may reduce their risk of predation by waiting until subordinates have resumed foraging before doing so themselves. Although such status-related ordering in the resumption of foraging activity has been observed in several bird species, the underlying mechanism(s) facilitating such a delay remains unknown. Social status per se and status-related foraging benefits prior to a threat of predation (i.e., individual hunger level) have both been suggested as possible mechanisms. We tested between these two alternative suggestions using pairs of stream-dwelling juvenile Atlantic salmon, for which the dominant-subordinate relationship was known. Fish were tested at equal and unequal hunger levels. Fish were presented with drifting prey, followed by a predation threat in the form of an aerial predator model. Which fish (i.e., dominant or subordinate) initially resumed foraging activity after exposure to the predator model was recorded. When both fish were at an equal hunger level, the dominant fish was more likely to resume foraging first. When the dominant and subordinate fish differed in their hunger level, the hungrier fish was the first to resume foraging regardless of social status. These results support the conclusion that hunger level, rather than social status per se, determines the order in which juvenile Atlantic salmon resume foraging after exposure to a predator.
In recent years, evidence for interindividual variation in ''personality'' within animal populati... more In recent years, evidence for interindividual variation in ''personality'' within animal populations has been accumulating. Personality is defined as consistency in an individual's behavioral responses over time and/or across situations. One personality trait that has potentially far-reaching implications for behavioral ecology, and may provide insight into the mechanisms by which consistent behavioral correlations arise, is that of boldness. Boldness is defined as the tendency of an individual to take risks and be exploratory in novel contexts. Using the framework of behavioral syndromes, we tested for individual differences in boldness in the laboratory among field-caught juvenile bluegill sunfish (Lepomis macrochirus) within and across the contexts of exploratory behavior, activity, and risk taking (e.g., antipredator) behavior. After such testing, individuals were tagged and returned to their lake of origin as part of a mark-recapture study testing for the repeatability of individual differences in boldness. Here, we report strong and consistent individual differences in boldness within and across all 3 behavioral contexts. Additionally, we observed that at least some boldness behaviors were repeatable after a 1-3 month recapture period. This study provides novel evidence for a boldness syndrome in sunfish, as well as insight into how behavioral types (e.g., shy/bold) may evolve and be maintained in natural populations.
Intermittent locomotion, characterized by moves interspersed with pauses, is a common pattern of ... more Intermittent locomotion, characterized by moves interspersed with pauses, is a common pattern of locomotion in animals, but its ecological and evolutionary significance relative to continuous locomotion remains poorly understood. Although many studies have examined individual differences in both intermittent locomotion and boldness separately, to our knowledge, no study to date has investigated the relationship between these 2 traits. Characterizing and understanding this relationship is important, as both locomotion and boldness are associated with several ecologically relevant behaviors such as foraging, mating, predator evasion, exploration, and dispersal. Here, we report on individual differences in boldness (risk-taking behavior) and intermittent locomotion in a novel laboratory environment in field-caught juvenile bluegill sunfish (Lepomis macrochirus). Our results show that juvenile bluegill sunfish exhibited individual-level variation in 2 modes of intermittent locomotion (undulatory and labriform swimming) and that this variation was correlated with differences in their boldness behavior. Generally, bolder individuals spent more time moving fast for longer durations and with shorter pauses than more timid individuals. Neither boldness nor locomotion was correlated with body size or body condition. This study provides the first empirical evidence for a link between an animal ''personality'' trait and intermittent locomotion.
Cichlid fish (Aequidens curvieeps) distributed themselves and allocated their foraging time betwe... more Cichlid fish (Aequidens curvieeps) distributed themselves and allocated their foraging time between two drift food patches in close approximation to the patch profitability ratio, as predicted by the ideal free distribution theory. The fish thereby achieved similar average feeding rates in the two patches, in two of three patch profitability ratio experiments. However, one major assumption of the ideal free model was violated, since individual fish differed in their competitive abilities for limited food resources, which resulted in unequal payoffs among individuals within each patch. Individual variation in feeding rates, and thus in competitive ability, was not related to despotism, but perhaps rather to individual differences in perceptual ability and in the ability to learn which patch was currently the more profitable. The strategy used by the fish to assess patch profitability included sampling available patches. However, individual fish switched (sampled) patches with varying frequency. Sampling had an associated cost, since high-frequency switchers had lower feeding rates on average than low-frequency switchers. Differences in foraging strategy among the fish therefore contributed to the observed inequality in individual payoffs within patches.
Males are generally expected to be discriminating in their choice of mates when females vary in q... more Males are generally expected to be discriminating in their choice of mates when females vary in quality and when under sperm competition from rival males. However, how sperm competition and female quality interact to influence male mating decisions remains poorly understood. Here, we explored the concurrent effects of sperm competition and female body length on male mating decisions in the Trinidadian guppy (Poecilia reticulata) as a model system. We used female body length as a proxy for fecundity and manipulated the relative size difference of paired stimulus females concurrently with sociosexual cues (i.e., presence of rival males) that may predict sperm competition. When all else was equal, males preferred the larger female when the paired females differed considerably in body length. The presence of either 1 or 2 rival males near, and sexually interacting with, the initially preferred female reduced a focal male's preference for that female and increased the probability that he would reverse his initial mate preference. However, focal males were more likely to reverse their initial preference when the females were similar in body length than when they differed considerably in body length after observing initially preferred females interacting with 1 rival male. Our novel results suggest that male guppies simultaneously evaluate sperm competition and female quality when making mating decisions.
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Papers by Jean-Guy Godin