Social partner preferences of male and female fighting fish (Betta splendens)

While the social interactions of Betta splendens have been studied in the contexts of dominance hierarchies, mate choice and communication networks, the social partner preferences of Betta have been largely overlooked. In this study, we presented male and female Betta with a single male, a single female, and a group of three females in dichotomous choice tests in order to better understand basic social interactions in this largely nonsocial species. The highly territorial Betta preferred associating with conspecifics in nearly every configuration we tested, with exceptions noted when single females were given the choice between a lone male and an empty chamber, and when males were presented with a single female and an empty chamber. Also, in most tests, the fish chose to spend more time with the larger group of females. The motivation for this preference certainly varied from reproductive to anti-predator. While such behavior might not suggest true shoaling behavior, it does demonstrate a subtle degree of sociality.     

Sex Differences in Retrieval Behavior by the Biparental Convict Cichlid

Biparental species occasionally demonstrate a division of roles in which parents perform sex-typical tasks, with females offering direct care and spending the majority of their time with the offspring while males are more indirect in their care, providing the majority of defense against potential brood predators. To examine the flexibility in the sex-typical roles shown by convict cichlids ( Amatitlania nigrofasciata ), we displaced non-swimming young at three different distances from the nest and then analyzed the retrieval behaviors of each parent. Retrieval of altricial young is a behavior commonly used to measure parental care in mammalian studies, but has rarely been used in other taxa. We found sex differences in retrieval behavior: on average, females retrieved young close to the nest and males retrieved young far from the nest. This difference in parental contribution suggests a division of labor with sex-specific roles. Sex differences may be due to proximity to young and/or apparent risk of offspring predation. Additionally, we found that latency to first retrieval and total time spent retrieving young remained consistent across the various displacement distances, suggesting that retrieval is an essential parental behavior. Additionally, we include observations of wriggler retrieval by parents in a natural population of Costa Rican convict cichlids.     

Caribbean damselfish with varying territory quality: correlated behaviors but not a syndrome

The behavioral syndrome hypothesis suggests that individualanimals within a population behave differently due to specificbehavioral types, and these should be consistent across behaviorsor in different contexts. In contrast, for animals that livewithin an environment in which territory quality can changeover time, natural selection should have favored behavioralflexibility and modulation of the cost of defense in relationto territory quality. This would require assessment of the territoryfollowed by displays of appropriate types and intensities ofbehavior. We examined the territorial behavior of male beaugregorydamselfish (Stegastes leucostictus) by enhancing territory qualityusing artificial breeding sites and comparing their behaviorto males on lower quality natural sites. When male fish weredefending high-quality artificial territories, they had higherlevels of aggression toward male conspecifics and courtshiptoward females than when on low-quality natural territories.We also found that aggression and courtship behaviors were correlatedon natural sites but not on artificial sites. Behaviors werenot correlated within individuals when males switched from naturalto artificial territories or from artificial to natural territories.These results indicate that males assess their current territoriesand adjust behaviors accordingly and that courtship and aggressivebehaviors are not linked within a permanent behavioral syndrome.     

Preservation of behavior after fifteen years of isolation: comparisons of wild and captive endangered pupfish in their natural habitat

Endangered species are often maintained in captivity to serve as a safeguard in the event of an extirpation of natural populations. However, wild and captive populations can rapidly diverge in genetic and phenotypic characteristics, including behavior, when maintained in isolation and under different environmental conditions. Here, we compare two populations of the endangered Leon Springs pupfish (Cyprinodon bovinus): a captive population maintained at the Southwestern Native Aquatic Resources and Recovery Center (SNARRC) and the only remaining wild population. Wild fish in the natural Texan Diamond Y desert spring are remnants of a past reintroduction of captive SNARRC fish, which occurred in 1998. The fifteen years of isolation have led to genetic and morphologic differences between the two populations. To assess the behavioral implications of such divergence, we released previously captive C. bovinus into natural habitat and quantified behaviors under natural conditions and in semi-controlled mesocosms and then replicated these conditions with the established natural population. Both populations exhibited similar levels of reproduction, foraging, and agonistic behavior. Despite divergence in genetic and morphometric characteristics, overall behavioral patterns of C. bovinus remained consistent in similar environments. This stability suggests that captive C. bovinus could again be successful establishing in their natural habitat. It is our hope that this investigation will help focus future conservation efforts towards monitoring the persistence of reintroduced C. bovinus in addition to providing a framework for other recovery plans reintroducing captive stock into ancestral habitats.     

Aggregation Behavior in Wildtype and Transgenic Zebrafish

Recent advances in the development and availability of genetically modified animals enable researchers to examine the effects of phenotypic characters on social behavior. In fish, shoaling behavior is known to be influenced by characteristics such as body coloration, striping pattern, body shape, and size. GloFish^TM are genetically engineered zebrafish (Danio rerio) that express red fluorescent protein (RFP), resulting in on overall red coloration under the dark longitudinal stripes. The GloFish pattern is distinct from the light body coloration underlying the dark longitudinal stripes seen in wildtype zebrafish. We presented wildtype and transgenic RFP zebrafish with same‐sex shoals of both strains of fish in dichotomous choice tests. No preference for either of the shoals was shown, however, both strains showed significant preferences for swimming near shoals vs. swimming near an empty tank compartment. When presented with opposite‐sex individuals of both strains, no preference was shown by either sex of either strain. Thus, the red body coloration of transgenic zebrafish does not appear to affect choice of social partner, in either a shoaling or a potentially reproductive context.     

Sex differences in biparental care as offspring develop: a field study of convict cichlids (<Emphasis Type="Italic">Amatitlania siquia</Emphasis>)

Parental investment theory states that parents should contribute more to older offspring. Differences between the sexes also influence how each parent contributes to offspring in biparental species. Here, we examined a naturally occurring population of biparental convict cichlids in Costa Rica to determine how each parent cared for offspring during two distinct offspring development stages. Consistent with the predictions of the reproductive value hypothesis, we hypothesized that the levels of parental contribution would be relative to the value that each parent places on a brood. We predicted that female parents would contribute more than male parents because female convict cichlids have lower future reproductive success than males. Additionally, we predicted that both parents should contribute more to older offspring, either due to the young’s increased susceptibility to predation (i.e., the vulnerability hypothesis) or because of the longer period of time parents have been interacting with older offspring (i.e., feedback hypotheses). This increase in investment by males should coincide with a change in the coordination of care between parents. Detailed observations of parental pairs in their natural habitat supported these predictions. Females contributed more to broods than males and were relatively unaffected by offspring age while males spent significantly more time with older, free-swimming fry. Additionally, males tended to leave younger offspring more than females did, and were more likely to do so consecutively with younger offspring. This suggests that the coordination of duties between parents changes as parental investment changes. Overall, these data support both the reproductive value and the vulnerability hypotheses, but not necessarily the feedback hypothesis.     

Juvenile convict cichlids shoaling decisions in relation to shoal size and age

Many animals form groups and socialize in response to evolutionary pressures such as predation, food availability, and mate acquisition. Evidence of social choice based on various phenotypic characters (Group Phenotypic Composition [GPC]) has been observed in several animal species. In addition to the physical characteristics of the social group, it is also interesting to consider how decisions of who to socialize with might be expected to change for an individual over time. Younger individuals with limited life experience may discriminate differently between social groups than older conspecifics who have had the opportunity to learn and who may be faced with different ecological or environmental pressures. Here, we used a traditional two‐choice design to explore the shoaling behavior of juvenile convict cichlids and determine whether the number of fish and/or the size/life stage of the individuals within a shoal influenced social choices. We found that juvenile convict cichlids spent more time shoaling with similarly sized juvenile individuals and also preferred to shoal with larger shoals, but not when shoals were comprised of adult fish. The size of the individuals in a shoal was a more influential factor than the size of the shoal itself. Size of individual juveniles was correlated with tendency to visit shoals, but was not correlated with overall time spent shoaling, regardless of shoal composition. As juveniles, convict cichlids can make discriminatory choices that are influenced by specific aspects of shoal composition.     

Conservation and conflict between endangered desert fishes

Conservation of naturally sympatric endangered species requires unique considerations. While impacts of invasive species garner much attention, interactions between endangered species must also be managed. The endangered Leon Springs pupfish, Cyprinodon bovinus, has suffered a population decline due to decreasing natural habitat. As breeding habitat is lost, C. bovinus is also adversely affected by the sympatric, endangered Pecos gambusia, Gambusia nobilis. Here, we document interactions between these species, finding significantly more G. nobilis accumulated at pupfish spawning events than randomly distributed on breeding grounds in the absence of spawning. As a known egg predator, our results suggest that G. nobilis presence at spawnings may further decrease pupfish numbers while also altering the evolutionary dynamics of C. bovinus breeding tactics. Habitat restoration may decrease Gambusia concentrations or influence C. bovinus breeding behaviour and increase the number of territorial males resulting in viable population sizes for both critically endangered fishes.