Kevin Warburton

Deep learning and education for sustainability

Deep learning is a key strategy by which students extract meaning and understanding from course materials and experiences. Because of the range and interconnectedness of environmental, social and economic issues, and the importance of interdisciplinary thinking and holistic insight, deep learning is particularly relevant in the context of education for sustainability. However, deep learning can be inhibited if the existing interests or backgrounds of students have a strong disciplinary focus. This paper reviews factors that influence deep learning and discusses some ways in which environmental educators can encourage students to use deep learning strategies. Such strategies are seen to be necessary to maximise the benefits from environmental courses and are likely to foster creative interdisciplinary approaches to sustainability beyond the institution.

Tendency-distance models of social cohesion in animal groups

Although it has been assumed that attraction and repulsion between social individuals constitute a basis for group cohesion, there has been no systematic study of the possible ways in which these tendencies might vary with inter-individual distance (IID), or of associated implications for group structure. In this paper, a family of attraction/repulsion--distance functions is described. Computer simulation was used to examine the effects of each function on group cohesion, as reflected by mean values and variability in IID and group shape. Our results showed that: (a) all models led to stability in group structure, but differed significantly in terms of stable IID and group shape characteristics; (b) cohesion was best served by an upwardly convex behaviour--distance function in which maximum attraction equaled maximum repulsion (and the biological plausibility of this function is discussed); (c) group elongation and variability in mean IID were significantly positively correlated; (d) although dyads maintained an equilibrial separation distance, at which attraction balanced repulsion, in larger groups stable nearest neighbour distances were often less than the equilibrium distance; and (e) individuals needed to monitor and respond to only relatively few of their companions in order to avoid group fragmentation.

The use of local landmarks by foraging goldfish

Goldfish, Carassius auratus, were introduced into an arena tank containing two symmetrically placed gravel-filled trays, one of which contained hidden food. In the absence of additional structures in the tank, the accuracy of food-patch choice (i.e. the proportion of individuals contacting the full tray before the empty tray) was close to that expected assuming random binary choice. Accuracy improved significantly, however, when landmarks (a rock/plant combination or multicoloured plastic columns) were positioned close to the food patch. Choice performance also improved when the plastic columns were placed in the opposite (non-food) half of the tank, indicating a capacity for indirect landmark usage as distinct from direct visual cueing. Latencies to feeding decreased with experience in all tratments, but were significantly lower in the presence of landmarks. Exploratory sampling behaviour, as indicated by the number of visits to the empty patch once food had been found during a trial, was significantly less frequent in the presence of strong landmarks. Fish in all treatments increased the frequency of sampling visits following a reversal of full and empty patches. Reliance on memory-based spatial behaviour may therefore vary according to the nature and complexity of the visual environment.

Predator recognition and anti-predator responses in the rainbowfish Melanotaenia eachamensis

Abstract Predator evasion behaviour patterns of three populations of rainbowfish (Melanotaenia eachamensis) were compared. The populations differed in the level of complexity of their natural habitats and the type and extent of predation. The predator recognition abilities of fish were assessed by exposing them to models differing in their degree of predator realism. The availability of vegetated cover and the location of the models with respect to cover were manipulated. Fish from Lake Tinaroo, a relatively open habitat containing numerous predators, showed strong changes in elective group size (EGS) in response to the different models but did not rely on cover as a place of refuge. In contrast, Dirran Creek fish originate from a small, fast-flowing, structurally complex stream lacking predatory fish species, and they showed little ability to distinguish between the different models and responded to threat by spending longer in vegetated areas. Members of the Lake Eacham captive stock increased their EGS in response to models representing low threat and with more threatening models increased the amount of time spent in vegetated regions of the arena. The contrasting reactions to predatory threat displayed by these populations highlights the need to use a number of different response indices when comparing the anti-predator responses of different fish populations. These data suggest that the level of habitat complexity as well as prior predator experience influence anti-predator responses of different fish popu-lations.

Species discrimination in guppies: Learned responses to visual cues

Abstract The possibility that animals can discriminate conspecifics and heterospecifics by integrating multiple-cue information obtained by a single sensory modality was tested using guppies, Poecilia reticulata . The influence of familiarity on guppy discrimination was examined through binary-choice experiments in which juvenile guppies were allowed to associate with familiar or unfamiliar siblings, unrelated conspecifics or heterospecifics (swordtails, Xiphothurus helleri ). Stimulus and subject (test) individuals were separated by partitions made of clear Perspex or plastic mesh, and the results of trials using the two partition types were compared to provide insight into the sensory modalities involved in recognition. Guppies associated more readily with familiar than unfamiliar conspecifics. The trials with the Perspex partition revealed that visual cues were involved in conspecific discrimination. Guppies were also visually attracted to familiar swordtails, and to unfamiliar swordtails as long as the guppies were originally reared with swordtails, showing that the formation of a recognition template in early life is flexible and not controlled by a closed genetic programme. However, there was evidence that attractive long-range swordtail cues were overridden by those permitting more detailed species discrimination at close range. In the trials with the mesh partition, attraction to siblings was apparent only at close range, suggesting that the mesh impaired the visual discrimination abilities evident from the Perspex trials. Heterospecific attraction to swordtails increased when the mesh partition was used, possibly for the same reason. It is likely that guppies integrate responses to distance-dependent visual (and possibly mechanical) stimuli to permit recognition of individuals, kin members or species. With regard to discrimination studies on aquatic vertebrates, the potential advantages to be obtained from the use of complementary behavioural assay techniques, and from analyses that take into account inter-brood variation and the length of the experimental acclimation period, are stressed.

Social mechanisms enhance escape responses in shoals of rainbowfish, Melanotaenia duboulayi

Shoaling behaviour has been shown to provide many benefits to group members. In this study we examined the ability of fish shoals to escape from a novel trawl apparatus. Fish in shoals of 5 found, and escaped through, a hole in the oncoming trawl more quickly than fish in pairs. Fish in the larger shoals displayed a significant decrease in escape latencies over a series of five trawls, providing clear evidence of net avoidance learning, whereas fish in pairs showed no evidence of learning over successive runs. Observations suggested that more information on the location of the escape route was available to fish in larger shoal sizes owing to social stimulation.

Generalists as sequential specialists: Diets and prey switching in juvenile silver perch

Diets of silver perch, Bidyanus bidyanus, in organically fertilised aquaculture ponds were dominated by chironomid larvae, Daphnia and calanoid copepods. Insects and crustaceans contributed approximately 80% and 20% by weight to the diet respectively. Classification of the stomach contents of individual fish revealed 8 diet groups, 4 of which were dominated by planktonic crustaceans and 4 by insects. Each diet group was strongly dominated by a different prey type. Fish from the same sample tended to belong to the same diet group and there was a non-random distribution of diet groups across ponds. Perch diets were influenced by the method of pond fertilisation (livestock effluent or pellet feed). Shifts in the representation of groups indicated that fish switched from one diet group to another over a 2–4 week period. The selection of planktonic prey by perch was related to prey densities in the ponds. Fish preferred Daphnia when these prey were common, but switched to calanoids and insects when Daphnia were scarce. A perfect rank correlation between the mean body size of planktonic prey and their contribution to the diet suggested that prey choice involved comparative decisions based on prey size. These findings indicate that, while classified as dietary generalists, silver perch exhibit consumption patterns which at the individual level are highly specialised at any given time. These patterns can be predicted, given information on prey densities in the environment.

Predator shoaling moderates the confusion effect in blue-green chromis, Chromis viridis

SummaryIn experiments, blue-green chromis [Chromis viridis (Cuvier 1830)] were fed on either scattered or aggregated swarms of brine shrimp (Artemia sp.). Ten runs with each prey dispersion treatment were performed with shoals of one, two, five and ten chromis. The mean lag in reaching peak feeding rate for fish fed on aggregated prey was significantly shorter in the larger chromis shoals. In contrast, with the scattered treatment all such lags were similar and very short. As foraging proceeded, higher feeding rates were observed in the larger feeding shoals, regardless of prey dispersion. Prey capture success (i.e. the rate of retention of intercepted prey) declined with time, but was significantly higher in groups of ten fish. Two main conclusions emerge. Firstly, grouping facilitated initiation of feeding by individuals preying on concentrated swarms and reduced the delay in reaching a maximum feeding level. This may have been due to a suppression of the confusion effect through reduced reliance upon vigilance. Secondly, reduced vigilance allowed larger shoals of chromis to feed effectively over more extended periods. Trends of increasing shoal cohesion and decreasing prey retention rate with time were consistent with a postulated increase in antipredator vigilance with declining feeding motivation.

Costs of learning : the dynamics of mixed-prey exploitation by silver perch, Bidyanus bidyanus (Mitchell, 1838)

Although generalist predators have been reported to forage less efficiently than specialists, there is little information on the extent to which learning can improve the efficiency of mixed-prey foraging. Repeated exposure of silver perch to mixed prey (pelagic Artemia and benthic Chironomus larvae) led to substantial fluctuations in reward rate over relatively long (20-day) timescales. When perch that were familiar with a single prey type were offered two prey types simultaneously, the rate at which they captured both familiar and unfamiliar prey dropped progressively over succeeding trials. This result was not predicted by simple learning paradigms, but could be explained in terms of an interaction between learning and attention. Between-trial patterns in overall intake were complex and differed between the two prey types, but were unaffected by previous prey specialization. However, patterns of prey priority (i.e. the prey type that was preferred at the start of a trial) did vary with previous prey training. All groups of fish converged on the most profitable prey type (chironomids), but this process took 15-20 trials. In contrast, fish offered a single prey type reached asymptotic intake rates within five trials and retained high capture abilities for at least 5 weeks. Learning and memory allow fish to maximize foraging efficiency on patches of a single prey type. However, when foragers are faced with mixed prey populations, cognitive constraints associated with divided attention may impair efficiency, and this impairment can be exacerbated by experience. (c) 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Microhabitat use by the rainbowfish Melanotaenia duboulayi in a subtropical Australian stream

Abstract. Microhabitat use and feeding behavior of the rainbowfish Melanotaenia duboulayi (Castelnau) were investigated in a slow-flowing stream adjacent to riparian forest in south-eastern Queensland, Australia. Fish were more abundant in vegetated areas, but did not enter dense Vallisneria beds, where predators were observed. In sunny conditions shoals of juveniles occurred near the water surface feeding floating material on the surface, but larger fish tended to occur at the bottom near submerged vegetation, often utilizing the overhanging aquatic plant community as a refuge and food source. In the middle of the day, juveniles and small fish seemed to show behavioral thermoregulation at the surface in the warmest site. Under cloudy conditions, however, fish of all sizes preferred deeper water. The present study suggests that in still and sunny pools thermal change caused by sunlight influences the microhabitat choice of small fish. A field experiment using a kingfisher model implies that fish swimming at the surface could escape from aerial predators in sunlit conditions by responding to moving shadows, but could not do so under cloudy conditions.