Jennifer J. Templeton

Producers, scroungers, and group foraging

We have developed a model that reconciles information-sharing and producer-scrounger models of group foraging. Our model includes producers, scroungers, and an opportunistic forager that can both produce and scrounge but with reduced efficiency. We show that these three strategies can coexist only in the unlikely case that the opportunists loss in searching ability is exactly equal to its gain in scrounging ability. However, all pairs of strategies can coexist. Three parameters control the proportions of coexisting strategists: the degree of compatibility between the opportunists producing and scrounging activities; the proportion of food patches that are shared with scrounging individuals; and the effective group size. When there is little incompatibility between producing and scrounging, opportunists will always be present, unless the producer is able to consume most of the patch without sharing. The opportunist strategy is always excluded when there is a high degree of incompatibility between producing and scrounging. We consider the organismal and ecological factors that are likely to affect all three parameters. Our model predicts that scrounging behavior is likely to be selected in a wide range of foraging groups and that it may impose a considerable cost on sociality.

Life skills training for hatchery fish: Social learning and survival

Abstract Recent investigations of social-learning processes have clear relevance for hatchery practice in the rearing of some species of fish. Research findings show that many fish learn to recognize the stimulus features of food, predators and habitat. The behavior of these fish may then serve as a source from which naive conspecifics can acquire recognition of the same stimulus. Learned behavior can result from simple exposure of fish to conspecifics engaged in particular activities. Fish that observe a conspecific consume a novel food later show an increased tendency to eat that food themselves. Fish that observe conspecifics displaying alarm behavior in the presence of a novel chemosensory stimulus (pseudopredator) later themselves display alarm behavior to the chemosensory stimulus. Fish that visually observe predators preying on conspecifics, later show enhanced ability to evade such predators. These findings suggest that large scale training of food and predator recognition may be feasible, effective, and economically undertaken before hatchery fish are released to the wild.

Vicarious sampling: The use of personal and public information by starlings foraging in a simple patchy environment

Abstract Group foragers may be able to assess patch quality more efficiently by paying attention to the sampling activities of conspecifics foraging in the same patch. In a previous field experiment, we showed that starlings foraging on patches of hidden food could use the successful foraging activities of others to help them assess patch quality. In order to determine whether a starling could also use another individual’s lack of foraging success to assess and depart from empty patches more quickly, we carried out two experimental studies which compared the behaviour of captive starlings sampling artificial patches both when alone and when in pairs. Solitary starlings were first trained to assess patch quality in our experimental two-patch system, and were then tested on an empty patch both alone and with two types of partner bird. One partner sampled very few holes and thus provided a low amount of public information; the other sampled numerous holes and thus provided a high amount of public information. In experiment 1, we found no evidence of vicarious sampling. Subjects sampled a similar number of empty holes when alone as when with the low and high information partners; thus they continued to rely on their own personal information to make their patch departure decisions. In experiment 2, we modified the experimental patches, increasing the ease with which a bird could watch another’s sampling activities, and increasing the difficulty of acquiring accurate personal sampling information. This time, subjects apparently did use public information, sampling fewer empty holes before departure when with the high-information partner than when with the low-information partner, and sampling fewer holes when with the low-information partner than when alone. We suggest that the degree to which personal and public information are used is likely to depend both on a forager’s ability to remember where it has already sampled and on the type of environment in which foraging takes place.

DEVELOPMENT OF FORAGING SKILLS AND THE TRANSITION TO INDEPENDENCE IN JUVENILE SAVANNAH SPARROWS

Abstract We investigated the timing and pattern of the development of foraging skills in juvenile Savannah Sparrows (Passerculus sandwichensis). Juveniles of known age, parentage, and in some cases sex were mist netted and tested in an aviary on Kent Island, an isolated island in the Bay of Fundy, Canada. Captive birds were exposed to three standardized and ecologically relevant foraging tasks: locating spittle bugs (Homoptera: Cercopidae) in spittle masses on goldenrod (Solidago rugosa) plants, small caterpillars under spruce (Picea glauca) bud scales, and beetle larvae under leaves. The feeding trials involved 33 juveniles aged 17–42 days, four independent juveniles whose precise ages were not known, and five adults for comparison. The performance of juvenile sparrows on all three tasks showed rapid improvement between 22 and 24 days of age. Thereafter, foraging proficiency (number of foraging attempts, number of prey obtained, foraging efficiency) did not improve significantly with age among juveniles; in fact, older juveniles performed as well as adults. Juvenile males obtained more prey items than juvenile females in aviary trials. Foraging proficiency in captivity was not a good predictor of survival to the following year, and it appeared not to be influenced by brood membership or parental age. The age at which foraging performance improved in captivity coincided with the age at which parents cease attending their fledglings in the field, suggesting that the duration of postfledging parental care may be determined by the speed at which juveniles can develop foraging skills. Desarrollo de Destreza para Forrajear y Transición a la Independencia en Juveniles de Passerculus sandwichensis Resumen.  Investigamos el tiempo y el patrón de desarrollo de destreza para forrajear en juveniles de Passerculus sandwichensis. Se capturaron y se evaluaron juveniles de edad, origen, y (en algunos casos) sexo conocidos en una pajarera en Kent Island, Bahía de Fundy, Canadá. Las aves capturadas se expusieron a tres tareas de forrajeo estandarizadas y ecológicamente relevantes: localizar insectos (Homoptera: Cercopidae) en su espuma en hierbas (Solidago), orugas pequeñas en las ramitas de Picea glauca, y larvas de escarabajo debajo de hojas. Utilizamos 33 juveniles de 17–42 días de edad, 4 juveniles independientes de edades desconocidas y 5 adultos para comparar. El desempeño de los juveniles en las tres tareas mostró una mejoría rápida entre 22 y 24 días de edad. A partir de entonces, la competencia al forrajear (número de intentos de forrajeo, número de presas obtenidas, eficiencia de forrajeo) no mejoró significativamente con la edad entre los juveniles; de hecho, los juveniles mayores se desempeñaron tan bien como los adultos. Los machos juveniles consiguieron más presas que las hembras en las pruebas. La competencia al forrajear en cautiverio predijo la sobrevivencia hasta el siguiente año adecuadamente, y pareció no ser influenciada por la nidada a que se pertenecía o por la edad de los padres. La edad en que la competencia al forrajear mejoró en cautiverio coincidió estrechamente con la edad en que los padres dejan de cuidar a los volantones en el campo, lo cual sugiere que la duración del cuidado de los padres después de que los polluelos salen del nido puede ser determinada por la rapidez con que los juveniles puedan desarrollar destreza para forrajear.

Mode of foraging competition is related to tutor preference in Zenaida aurita.

This study compared the direction of social learning in 2 populations of Barbados Zenaida doves (Zenaida aurita). One population (St. James) is territorial; it competes aggressively with conspecifics but scramble competes with heterospecifics. The other population (Deep Water Harbour) forages in large homospecific flocks. Field observations were conducted to quantify intraspecific and interspecific patterns of foraging association and aggression. Wild-caught doves from both areas were then tested on novel foraging tasks demonstrated by either a conspecific or a heterospecific tutor. In all experiments, St. James doves learned more readily from the heterospecific tutor (Carib grackle -Quiscalus lugubris-), whereas Deep Water Harbour doves learned more readily from the conspecific tutor. The type of competitive feeding interaction in the field (i.e., scramble vs. interference) appears to better predict the pattern of social learning in an experiment than does species identity.

Sociality and social learning in two species of corvids: The pinyon jay (Gymnorhinus cyanocephalus) and the Clark's nutcracker (Nucifraga columbiana)

The hypothesis that social learning is an adaptive specialization for social living predicts that social species should learn better socially than they do individually, but that nonsocial species should not exhibit a similar enhancement of performance under social learning conditions. The authors compared individual and social learning abilities in 2 corvid species: the highly social pinyon jay (Gymnorhinus cyanocephalus) and the less social Clarks nutcracker (Nucifraga columbiana). The birds were tested on 2 different tasks under individual and social learning conditions. Half learned a motor task individually and a discrimination task socially; the other half learned the motor task socially and the discrimination task individually. Pinyon jays learned faster socially than they did individually, but nutcrackers performed equally well under both learning conditions. Results support the hypothesis that social learning is an adaptive specialization for social living in pinyon jays.

Public information cues affect the scrounging decisions of starlings.

The foraging decisions that individuals make within groups should depend on the information available to them. An aviary experiment was conducted to examine whether a starlings, Sturnus vulgaris, decisions either to approach and feed from (scrounge) or to avoid the patches exploited by a partner bird are influenced by the information the partner provides. Both the type of information a subject could recognize and the point at which this information became available during the partners exploitation of a patch were manipulaed. Information concerning the quality of a patch was available in the form of a concealed colour cue and from the behaviour of the partner bird. The foraging environment was manipulated such that colour cues were either present or absent, and provided either correct or incorrect information concerning the presence of food. When cues corresponded with past foraging experience, test subjects responded selectively and profitably to the patch exploitations of the partner; they scrounged from a higher proportion of profitable patches than control birds, which lacked the ability to recognize colour cues. Test subjects also arrived more quickly at profitable patches that the partner bird discovered than did control birds; and consequently, were able to obtain more food at each food patch scrounged. Finally, test subjects avoided scrounging when the partner discovered empty patches and thus saved foraging time. Responding selectively to public information, therefore, allows an individual to compete more effectively for resources within a foraging group.

Learning from others' mistakes : a paradox revisited

Some researchers have reported the paradoxical finding of enhanced social learning when naive observers learn from unskilled rather than skilled demonstrators, particularly in discrimination tasks. In two experiments with starlings, Sturnus vulgaris, I considered whether this enhanced learning is because the observer (1) sees incorrect responses only, (2) sees both correct and incorrect responses or (3) sees an increase in the proportion of correct responses over trials. In experiment 1, individual starlings observed a demonstrator bird perform multiple simultaneous discrimination tasks. In one group, the demonstrator always picked the correct stimulus; in another group, the demonstrator always picked the incorrect stimulus; in a third group, the demonstrator consistently picked the correct stimulus 50% of the time. Those subjects that observed only incorrect choices performed significantly better than the other two groups, but none of the birds achieved the 90% correct performance criterion. Experiment 2 involved a single discrimination task; thus, a fourth group was added to control for individual learning. Again, subjects that observed only incorrect responses learned the discrimination significantly more quickly than the other three groups. Subjects that observed the demonstrator make both correct and incorrect responses were equally likely to select the same (correct) or opposite (incorrect) stimulus when the demonstrator picked the correct stimulus. When the demonstrator picked the incorrect stimulus, however, these subjects were significantly more likely to pick the opposite (correct) stimulus. These findings suggest that when learning a discrimination problem, observing a foraging companions lack of success is more informative than observing its success. Copyright 1998 The Association for the Study of Animal Behaviour.

The empirical question of thresholds and mechanisms of mate choice

SummaryTheoretical discussions concerning how animals might best sample and select mates have suggested that individuals could base decisions either on a sample of mates (sampled-based decisions) or on a threshold of comparison (threshold-based decisions). Recent theoretical work demonstrates that threshold-based mating decisions generate higher expected fitness than sample-based mating decisions when search costs exist. Empirical results from most unmanipulated systems, however, either conclude that females make sample-based decisions or are inconclusive. A few experimental studies designed to detect mating thresholds purport to demonstrate threshold-based choice but an examination of these studies indicates such conclusions were premature. We believe that few examples of threshold-based choice exist because protocols designed to identify mating thresholds were often inconsistent with models of threshold choice. We suggest that future empirical work strive not to document mating thresholdsper se. Rather, future work might best reveal decision rules by manipulating the distribution of quality among potential mates; such manipulations predict uniquely how females using sample-based and threshold-based decision rules should behave.

Conditioning Shelter Dogs to Sit

Human contact in the shelter may lessen effects of change in environment and smooth transition into a home. Training can increase a dogs interaction with people in a shelter environment. Experiments were conducted to determine how rapidly shelter dogs learn to sit, if the dogs can retain sitting behavior over time, and if sitting transfers to novel locations and people. Two experiments trained shelter dogs (n = 21) to sit when a stranger approached over a 10-trial session. Food and a verbal cue or a clicker reinforced the sit. The experiments measured latency to sit for each trial. Latency to sit decreased significantly over trials. Another experiment included reinforcement given to dogs (n = 20) on a noncontingent basis or for sitting. Five days of the experiment (condition training) were in the same room with the same experimenter. The last 4 days (testing) varied by both experimenter and location (familiar or strange). Results indicate that short training sessions are effective for teaching shelter dogs to sit, that dogs can retain sitting behavior over 2 days, and that training transfers to novel people and situations.