Social transmission of maladaptive information in the guppy

Many animals are capable of learning from others, a processreferred to as social learning. There is little doubt that acapacity for social learning is an adaptation and that it typicallyresults in adaptive behavior. What is less clear is whetherthere are circumstances under which social learning can resultin the transmission of outdated, inappropriate, or maladaptiveinformation. Here we report an experimental study that investigatedthe social learning and transmission of maladaptive foraginginformation through small social groups of guppies, Poeciliareticulata. This experiment used a transmission chain designin which fish in small founder groups were trained to take eitheran energetically costly circuitous route to a feeder or a lesscostly short route, with trained founder members gradually replacedby untrained conspecifics. Three days after all the foundershad been removed, the behavioral traditions of groups of untrainedfish were still strongly influenced by their founder's behavior.Moreover, the rate at which untrained subjects that shoaledwith founder conspecifics trained to take the long route learnedto take the short route was significantly slower than for fishforaging alone. The results provide unequivocal evidence thatmaladaptive information can be socially transmitted throughanimal populations and imply that socially learned informationcan inhibit learning of the optimal behavior pattern.     

Diel activity and home range size in relation to food supply in a drift-feeding stream fish

Individuals within a species often compete for resources inboth space and time. In dominance hierarchies individuals withthe greatest competitive ability will occupy prime locationsduring optimal periods. We compared spatial and temporal useof habitat, aggression, and feeding success among giant kokopu(Galaxias argenteus) in dominance hierarchies under normal andreduced food supply. Under normal food supply conditions dominantfish were predominantly nocturnal and maintained large homeranges at night. Conversely, subdominant fish were diurnal andoccupied large home ranges by day but were generally not observedat night. When the food supply was limited, the utilizationof pools was determined by social rank. Dominant fish from eachpool increased diurnal activity, home range size, aggressiveness,and the capture of food items offered by day while simultaneouslyreducing the spatial and temporal activity and habitat use ofsubdominant fish. These results indicate that behavioral changesin large dominant fish influence and reduce the amount of resourcesavailable to subdominant fish.     

Social Learning in Vespula Germanica Wasps: Do They Use Collective Foraging Strategies?

Vespula germanica is a social wasp that has become established outside its native range in many regions of the world, becoming a major pest in the invaded areas. In the present work we analyze social communication processes used by V. germanica when exploiting un-depleted food sources. For this purpose, we investigated the arrival pattern of wasps at a protein bait and evaluated whether a forager recruited conspecifics in three different situations: foragers were able to return to the nest (full communication), foragers were removed on arrival (communication impeded), or only one forager was allowed to return to the nest (local enhancement restricted). Results demonstrated the existence of recruitment in V. germanica, given that very different patterns of wasp arrivals and a higher frequency of wasp visits to the resource were observed when communication flow between experienced and naive foragers was allowed. Our findings showed that recruitment takes place at a distance from the food source, in addition to local enhancement. When both local enhancement and distant recruitment were occurring simultaneously, the pattern of wasp arrival was exponential. When recruitment occurred only distant from the feeder, the arrival pattern was linear, but the number of wasps arriving was twice as many as when neither communication nor local enhancement was allowed. Moreover, when return to the nest was impeded, wasp arrival at the bait was regular and constant, indicating that naive wasps forage individually and are not spatially aggregated. In conclusion, this is the first study to demonstrate recruitment in V. germanica at a distance from the food source by modelling wasps’ arrival to a protein-based resource. In addition, the existence of correlations when communication was allowed and reflected in tandem arrivals indicates that we were not in the presence of random processes.     

Social enhancement of foraging on an ephemeral food source in juvenile walleye pollock,Theragra chalcogramma

Synopsis The foraging effectiveness of walleye pollock juveniles, Theragra chalcogramma, was determined experimentally to test the hypothesis that social cues may facilitate the ability of individuals to exploit ephemeral food patches. Fish were tested when isolated, paired with one other fish, and in a group of six fish. Test fish exploited more food patches while in a group of six than when they were isolated. Patch exploitation by paired fish was intermediate to but not statistically different than isolate or grouped treatments. The number of pellets eaten by test fish in a group and a pair was more than 3.5 times that of when they were isolated, although the overall relationship between the amount of food eaten and group size was not statistically significant. Results support the hypothesis that juvenile walleye pollock exploit ephemeral food patches more effectively in the presence of conspecifics. In planktivores such as walleye pollock, social cues may enhance foraging on transient food sources either by facilitating detection of food patches (local enhancement) or by stimulating foraging activity when a food patch is located (social facilitation).     

Orientation behavior of butterflyfishes (family Chaetodontidae) on coral reefs: spatial learning of route specific landmarks and cognitive maps

Synopsis Foraging butterflyfishes follow predictable paths as they swim from one food patch to another within their territories and home ranges. The pattern is repeated throughout the day. The behavior is described in species belonging to the coral feeding guild. Habit formation and spatial learning are implicated. Foraging paths are based on learned locations of route specific landmarks. When a coral head is removed the fish look for it in its former location. If pairs of foraging fish are deflected from the path, they resume their routine pattern at the first landmark they encounter. Periodically, fish make excursions of 30 m or more to distant parts of the reef. Usually they follow different paths on the outbound and homeward legs of these excursions. The critical question is: Are the paths novel? If they are, it is evidence for the use of cognitive maps. Certainly fishes living in the highly structured coral reef environment are prime candidates to use cognitive maps in their orientation behavior.     

Prey selection by experienced and naive juvenile Atlantic salmon

Both in foraging groups and in a sequential prey encounter context, learning had a visible effect on the pattern of selection for three live prey types ( Ecdyonurus larvae, Hydropsyche larvae, and Gammarus ) by juvenile Atlantic salmon Salmo salar . Compared to wild-caught fish, naive, hatchery-reared fish that had not been exposed to natural prey ate Hydropsyche larvae in a remarkably low proportion, and consumed a higher proportion of Gammarus. Ecdyonurus experienced a high and rather steady predation rate across the experience gradient, but after a short period of experience with live prey the consumption rate for Hydropsyche increased drastically, and that of Gammarus decreased, matching the selection pattern exhibited by wild fish. Individual fish offered prey in a sequential encounter context increased consumption rates of all the prey types as they gained experience, but the improvement was higher for the prey that were less consumed initially. Fish became more selective as they approached satiation, conforming to the prediction of optimal foraging theory that higher predator's energy requirements, as well as low food availability, result in reduced selectivity. The results also suggest that fish from distinct populations can differ in the degree of diet selectivity according to their energetic requirements for growth. The fast learning response of Atlantic salmon parr towards novel prey probably allows fish to maintain a high foraging efficiency when faced with frequent changes in the availability of different prey types.     

Coevolution of foraging behavior with intrinsic growth rate: risk-taking in naturally and artificially selected growth genotypes of <Emphasis Type="Italic">Menidia menidia</Emphasis>

Although there is accumulating evidence of growth-rate optimization by natural selection, the coevolution of growth rate and risk-taking behavior has not been sufficiently documented. The Atlantic silverside fish, Menidia menidia, displays countergradient variation in growth across a latitudinal gradient: genotypes from Nova Scotia (NS), for example, grow in length twofold faster than those from South Carolina (SC). Past work has established that fast growth is adaptive in northern climates, but the trade-off is poorer swimming performance and higher susceptibility to predators. We compared escape behavior and willingness to forage under threat of predation among growth genotypes reared and tested under common-garden conditions. When chased with a predator model, NS fish occupied shelter more quickly than SC fish. When food was supplied after a chase, NS fish reemerged from the shelter much more quickly than SC fish and immediately commenced feeding, whereas many SC fish displayed timid behavior and did not feed. When food was absent following a chase, however, NS fish remained in the shelter longer than did SC fish and both displayed timid behavior. Hence, the fast-growing NS genotype was bolder than SC fish in the presence of food, but shyer in the absence of food. These behaviors are adaptive given the physiological constraints intrinsic to each genotype. Experiments on captive populations of silversides that had been artificially selected for fast or slow growth confirmed that foraging behavior is genetically correlated with intrinsic growth rate, although in these trials the fast-growth genotype was always more bold, regardless of food availability, as would be expected in the absence of predators. We conclude that risk-taking foraging behavior coevolves adaptively with intrinsic growth rate in M. menidia.     

The Response to Novel Foods in Common Marmoset (Callithrix jacchus): The Effects of Different Social Contexts

The main aim of this study was to verify if the response to novel foods in common marmoset (Callithrix jacchus) is influenced by different social settings. This question was tested in three tests involving four social groups. The data regarding the response to novel foods were collected from a total of eight food-naive young. In particular, we explored if direct contacts between food-naive and experienced individuals would have a different effect on the response to novel food by the first, in comparison with a situation in which only visual contacts were allowed. These two different social settings were then compared to a situation in which the response to novel food was not mediated by the experience of group-mates. The results showed a significantly higher number of intervals in which naive young, in social settings, were observed feeding compared with a control test. However, this result was confirmed only in the case of novel foods, not in the case of familiar foods. Furthermore, in the tests in which direct social contacts were allowed, naive young obtained food from group-mates significantly more often in the case of novel than familiar foods. This study suggests that although naive young, when left in pairs, responded quickly to novel foods without the need to observe or interact with experienced group-mates, a process of social facilitation was evident. Such a process was not observed in the case of familiar foods, confirming the hypothesis that social facilitation operates in order to acquire novel foods in the diet of the group in the long term.     

Effects of fish presence and simulated moonlight gradients on night-time horizontal movements of a predatory zooplankter, Chaoborus punctipennis

Some zooplankton, including Chaoborus punctipcnnis, have recentlybeen reported to undergo die1 horizontal migrations in additionto their widely known vertical migrations. In a series of laboratoryand field experiments, we tested the influences of gradientsin light intensity and fish presence on horizontal migrationin C.Punctipennis. In a small chamber, C.punctipennis showedno response to simulated moonlight gradients. They did, however,show significant movement away from fish held at one end ofthe chamber under uniform moonlight. A field experiment in alarge chamber indicated that the response to fish was inducedby chemical cues. When tested in the laboratory chamber withboth moonlight gradients and fish present, C.punctipennis becamepositively phototactic. This response increased the movementaway from fish when the fish were at the darker end of the gradient,or reduced it when the fish were at the brighter end. Ln combination,these experiments demonstrate that C.punctipennis show directedhorizontal movements in response to fish presence and moonlightgradients, suggesting a potential for these stimuli to influencehorizontal migrations observed in the field. Present address: Department of Biology, University of CaliforniaLos Angeles, CA 90095-1606, USA     

The physiology of rainbow trout in social hierarchies: two ways of looking at the same data

Salmonids form dominance hierarchies in environments, where space or food are limiting. Our first objective was to investigate the physiology of individual rainbow trout in 4-fish hierarchies. Our second was to compare conclusions drawn from grouping physiological data on the basis of social rank with those based on relating individual physiology to individual aggressive behavior. To create a social hierarchy, groups of 4 juvenile trout were fed (1 % ration) using a darkened feeding container, twice daily (morning and evening). Each morning feeding was videotaped to record aggressive behavior, thereby facilitating the assignment of a social status rank to each fish. On days 5 and 10–11, physiological parameters were measured in fish fasted for 24 h. Social hierarchies formed in all tested groups. One fish would become dominant, whereas the three subordinate individuals would each assume a stable social rank. When classified according to this social rank, the three subordinate individuals all displayed similar physiology, different from the physiology of the dominant fish. The latter included higher ammonia excretion rate, greater protein utilization in aerobic metabolism, greater feeding, higher specific growth rate, greater increase in condition factor, and lower routine oxygen consumption rate. However, when individual aggression was taken into account, a continuous gradient was observed between aggression and physiology for most parameters, regardless of social status. These relationships could be improved by normalizing the aggression score to the overall level of aggression in each hierarchy. We argue that individual behavior should be considered instead of just social rank when studying the physiology of trout in social hierarchies.     

Predation risk and social interference as factors influencing habitat selection in two species of stream-dwelling waterstriders

We investigated how an aggressive species of waterstrider, Aquariusremigis, and potential predators, green sunfish (Lepomis cyanellus),affected the habitat use and mating behaviors of a less aggressivecongeneric species, A. conformis. Although these species sometimesco-occur, A. remigis typically lives in small streams with fewor no fish, whereas A. conformis are typically in medium- orlarge-sized streams with large populations of potentially predatoryfish. We tested in separate experiments in seminatural streams:1) the effect of fish on behaviors of A. conformis; 2) the effectof A. remigis on A. conformis; and 3) the habitat use of A.conformis when given a choice between pools with A. remigisor fish. The first experiment showed no effect of fish on eithermating behaviors or microhabitat use of A. conformis. This isin surprising contrast to the strong effects of fish alreadydocumented in A. remigis. The second experiment showed thatthe mating activity of A. conformis was reduced when A. remigiswere present; hence, A. conformis should avoid A. remigis. Finally,when A. conformis were presented with a choice between two pools,one containing A. remigis and the other containing fish, bothsingle males and pairs of A. conformis chose the pools withfish. In contrast, the habitat use of single female A. conformiswas not affected by either fish or A. remigis. Results fromthese experiments demonstrate that closely related species exhibitcontrasting social and antipredator behaviors and that aggressivesocial behavior is an important determinant of habitat partitioning     

Past Experience: a Help or a Hindrance to <Emphasis Type="Italic">Vespula germanica</Emphasis> Foragers?

In this study we investigate associative learning related to food location in Vespula germanica social wasps. Wasps were trained to associate a certain location with food, and their behaviour after food displacement was recorded. The effect of a different number of previous feeding experiences on the detection of the novel food source was evaluated. When these wasps associated a certain location with food, they returned to the original site despite the fact that food was no longer available. This occurred even when a new food source was placed very close to the learned location. The results demonstrate that this learning seems to temporarily impair the detection of new food sources. We discuss how previous experience seems to condition perception, delaying the detection of more rewarding contexts.     

Territorial male color predicts agonistic behavior of conspecifics in a color polymorphic species

Male cichlid fish, Astatotilapia burtoni, live in a lek-likesocial system in shore pools of Lake Tanganyika, Africa, asone of two distinct social phenotypes: territorial (T) malesthat comprise approximately 10–30% of the population andnonterritorial (NT) males that make up the rest. T males arebrightly colored either blue or yellow with chromatic body patternsand are larger, reproductively capable, and defend territoriescontaining a food resource used to entice females to spawn withthem. NT males are camouflage colored, smaller, have regressedgonads, and shoal with females. Importantly, males shift betweenthese social states depending on their success in aggressiveencounters. It is not known whether there is a difference betweenyellow and blue T morphs. Here we asked whether T males preferentiallydefend their territory against a male of the same or oppositecolor. T males observed in social groups had agonistic interactionspredominantly with neighboring T males of the opposite color,and yellow morphs initiated significantly more aggressive interactions.When agonistic preference was tested experimentally, T maleshad significantly more agonistic interactions toward males ofthe opposite color, and yellow T males became territorial inthe majority of those interactions. Taken together, these resultssuggest that male coloration is an important social signal amongneighboring T males in this species and support the hypothesisthat T males differentially direct agonistic behavior dependingon the color of neighboring males.     

RAPID BEHAVIORAL CHANGES IN MEDAKA (ORYZIAS LATIPES) CAUSED BY SELECTION FOR COMPETITIVE AND NONCOMPETITIVE GROWTH

Behavior is a major component of growth rate variation in fish, but the genetic relationship between behavior and growth is largely unknown. In particular, it is not known how behavior responds to natural or artificial selection on growth. It has been argued that artificial selection for fast growth in competitive environments might lead to higher levels of overall aggression, and therefore there would be no net gain in assimilation efficiency or growth. The contrary has also been argued. It is not immediately obvious, therefore, whether fish that avoid interacting with conspecifics should grow faster, or whether more aggressive, dominant individuals should grow faster. In the present study, we artificially selected fish on the basis of growth in two environments that differed in the intensity of social interactions. In the high interaction environment (HI), food was provided to excess inside a floating cork ring, which limited access to the food and allowed fish to attempt to monopolize the food supply. In the low interaction environment (LI), an equivalent amount of food was spread over the container's surface. In each social environment, fish were selected within family for fast and for slow growth rate during two generations (G₁ and G₂). The response was measured in the third generation (G₃) on the directly selected trait (growth) and on a correlated trait (agonistic behavior). The magnitude of the direct response to selection on growth in medaka was directly related to population density, i.e., selection was most effective at high densities. Agonistic behavior was inversely related to growth when individuals were raised and selected in an environment where enforced social interaction took place, so long as food was not limited in quantity.     

Parasite-induced change in host behavior of a freshwater snail: parasitic manipulation or byproduct of infection?

Host behavioral changes due to parasitism are often assumedto be adaptations of the parasite. However, behavioral effectsof parasites may be a generalized response to parasitism andonly coincidentally beneficial for parasite transmission. Forthis reason, alternatives to the manipulation hypothesis shouldbe tested. Previous work demonstrated that the trematode parasiteMicrophallus sp. influences the behavior of the snail Potamopyrgusantipodarum in a way that may increase the probability of transmission.Here I report work conducted to test alternatives to the manipulationhypothesis. In a field study, the effect of Microphallus onbehavior was compared to that of two other castrating parasitegroups to determine if the behavioral change is simply a byproductof parasitism. Also, the foraging behaviors of infected anduninfected snails were examined in the presence and absenceof food resources to determine if the hunger level of Microphallus-infectedsnails could account for the parasite-induced behavioral change.First, Microphallus-infected snails were found on top of rocksduring the day less often than the two other parasite groups. Thisevidence suggests that the behavioral change caused by Microphallusis specific to Microphallus-infected snails. Second, Microphallus-infectedsnails responded to the lack of food differently from uninfectedsnails. Uninfected snails retreated to safer positions underrocks when the food source was removed from the top of the rocks,while Microphallus-infected snails remained on top of the rockswhere the risk of consumption by the final host is greater.Taken together with previous studies, these results suggestthat infection by Microphallus results in behavior that enhancesparasite transmission.     

Warning coloration associated with nematocyst-based defences in aeolidiodean nudibranchs

This study examines the mechanisms of aposematism (unprofitabilityof prey combined with a conspicuous signal) in the aeolidioideanCratena peregrina (Gmelin, 1791). We investigated if marinefish avoid attacking aeolidioidean nudibranchs, which are anunprofitable group of prey for most predators. We analysed theinteraction between aeolids and predatory fish in laboratoryand field assays, with both live aeolids and artificial models.In the first experiment, we offered normal and blue-dyed C.peregrina to fish in the field. The number of attacks by fishwas independent of the density of the prey, albeit the normalaeolids were attacked less frequently than the blue ones. Thefact that all normal C. peregrina survived, whereas 12–20%of the blue aeolids died after fish attacks, suggests that aposematiccoloration provides a selective advantage against fish predators.Field and laboratory assays with artificial aeolids were employedto test the effects of different factors (number of cerata,colour pattern, nematocysts), or a combination of factors, onfish learning. Fish learned to avoid unpalatable models withthe colour pattern of C. peregrina. After three to four trainingsessions with unprofitable models, fish avoided profitable modelswith the same colour pattern. Our results suggest that the colourpattern of C. peregrina combined with the presence of dorsalappendages and nematocysts make fish avoid aeolids. (Received 22 January 2004; accepted 18 August 2006)     

Social behavior of juvenile chum salmon, Oncorhynchus keta, under risk of predation: the influence of food distribution

Synopsis Social interactions can influence both foraging reward and vulnerability to predators. We examined social interactions in groups of juvenile chum salmon, Oncorhynchus keta, receiving food that was either spatially dispersed, with many food items appearing synchronously, or spatially clumped, with individual food items appearing asynchronously. These experiments were conducted both in the presence and absence of predators. when food was dispersed and predators were absent, juvenile chum formed schools and all individuals had access to food, despite frequent agonistic interactions. When predators were present, schooling and feeding continued, but agonistic interactions ceased. In contrast, when food was clumped, dominant fish utilized aggression to monopolize food regardless of whether predators were present or absent, resulting in decreased group cohesion. These results illustrate that food distribution and social interaction may play a role in determining how fish balance predation risk against foraging reward.     

The effect of group size on space use and aggression at a concentrated food source in blue gouramis, Trichogaster trichopterus (Pisces: Belontiidae)

Synopsis We examined how spatial distribution and the use of aggressive behavior by blue gouramis, Trichogaster trichopterus (Belontiidae), in the presence of a concentrated food source were affected by group size and by the short-term presence and absence of food. Gouramis aggregated in the area of the food source, and the frequency of aggressive acts per fish was higher for fish near the food source than for fish away from it. The frequency of aggressive acts per fish near the food source decreased with group size and was about 50 times higher in groups of 2 and 4 than it was in groups of 16 and 32. In group sizes 2 and 4, the frequency of aggression was unaffected by the presence and absence of food, but in larger group sizes aggression increased during short intervals without food. The mean proportion of time spent near the food source increased from group size 2 to group size 8 and decreased from group size 8 to group size 32 and was greater during intervals of food availability than during intervals in which food was not available. We suggest that gouramis adjust their relative use of contest and scramble competition according to the costs and benefits of aggression as determined by the number of competitors and by the potential for missed feeding opportunities. The average proportion of time spent in the vicinity of the food source appears to be influenced by both the rate of aggression and by the net rate of gain available.     

Traveling Companions Add Complexity and Hinder Performance in the Spatial Behavior of Rats

We sought to uncover the impact of the social environment on the spatial behavior of rats. Food-deprived rats were trained in a spatial task of collecting food items from 16 equispaced objects. Following training, they were tested, first alone and then with a similarly-trained cage-mate. It was found that the presence of another rat substantially altered the rats'' spatial behavior. Lone rats collected the food items faster while traveling a shorter distance, reflecting a higher efficiency of task completion. When accompanied by a partner, however, the rats traveled together, visiting the same set of objects in each trip with one of them leading. Whether alone or with a partner, rats continued to revisit the same objects; however, more such revisits occurred with a partner. We argue that revisiting objects is not necessarily an error, since returning to past places is an important aspect of rats’ natural behavior. Revisiting an object following food depletion implies that searching for food was not the main driving force in the rats'' spatial behavior. Specifically, despite food deprivation, rats were more attentive to one another than to the food. This could be adaptive, since foraging and feeding in groups is a way of poison avoidance in wild rats. Finally, the addition of a social component added complexity to the environment since the rats organized their spatial behavior in reference to one another in addition to their organization in the physical surrounding. Consequently, when tested with a partner, spatial behavior was less structured, less predictable and more chaotic.     

Extreme boldness precedes starvation mortality in six-lined trumpeter (<Emphasis Type="Italic">Pelates</Emphasis> <Emphasis Type="Italic">sexlineatus</Emphasis>)

Fishes are often subjected to seasonal and spatial patchiness of food sources. We tested how risk-taking behaviour in the six-lined trumpeter, an estuarine seagrass resident fish, changed with hunger level in a laboratory experiment. When repeatedly offered a risky source of food, well-fed fish did not approach it and all fish survived over a one-month trial. In contrast, fish deprived of all food boldly first approached the risky food source after only a few days without food in some cases, or after many days in other cases, and then continued to approach risky food each time it was presented. Larger individuals were more bold (and had longer starvation endurance) than smaller ones, and after statistically controlling for these size effects, there were consistent individual differences in the propensity to take risks (i.e. boldness). These results show that food- and individual-dependent boldness will together affect vulnerability to predators and influence predation rates when resources become scarce.