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Romano D, Stefanini C. Any colour you like: fish interacting with bioinspired robots unravel mechanisms promoting mixed phenotype aggregations. BIOINSPIRATION & BIOMIMETICS 2022; 17:045004. [PMID: 35439743 DOI: 10.1088/1748-3190/ac6848] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 04/19/2022] [Indexed: 06/14/2023]
Abstract
Collective behaviours in homogeneous shoals provide several benefits to conspecifics, although mixed-species aggregations have been reported to often occur. Mixed aggregations may confer several beneficial effects such as antipredator and foraging advantages. However, the mechanisms promoting phenotypically heterogeneous fish aggregations have been poorly explored so far. Herein, the neon tetraParacheirodon innesiwas selected as the ideal model organism to test the role of visible phenotypic traits in promoting fish shoaling. Robotic fish replicas of different colours, but with a morphology inspired byP. innesi, were developed to test the affiliation behaviour of neon tetra individuals towards fish replicas with different phenotypic traits.P. innesiindividuals showed a decreasing preference in shoaling with the biomimetic, the blue, the red, and the grey replicas. This could be due to the greater visibility of the blue colour even in dark conditions. Furthermore, an increased reddening of the livery is often caused by physiological processes related to a nonoptimal behavioural status. The time spent in shoaling with each fish replica was strongly influenced by different ecological contexts. The longest shoaling duration was observed when a biomimetic predator was present, while the shortest shoaling duration was recorded in the presence of food. This confirms the hypothesis that heterogeneous shoals are promoted by the antipredator benefits, and reduced by competition. This study allowed us to understand basic features of the behavioural ecology favouring heterogeneous aggregations in shoaling fish, and provided a novel paradigm for biohybrid robotics.
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Affiliation(s)
- Donato Romano
- The BioRobotics Institute, Sant'Anna School of Advanced Studies, Viale Rinaldo Piaggio 34, 56025, Pontedera, Pisa, Italy
- Department of Excellence in Robotics, A.I., Sant'Anna School of Advanced Studies, 56127, Pisa, Italy
| | - Cesare Stefanini
- The BioRobotics Institute, Sant'Anna School of Advanced Studies, Viale Rinaldo Piaggio 34, 56025, Pontedera, Pisa, Italy
- Department of Excellence in Robotics, A.I., Sant'Anna School of Advanced Studies, 56127, Pisa, Italy
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2
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Schons RF, Vitt S, Thünken T. Resource heterogeneity but not inbreeding affects growth and grouping behaviour in socially foraging juvenile cichlid fish. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13960] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rieke F. Schons
- Institute for Evolutionary Biology and Ecology University of Bonn Bonn Germany
| | - Simon Vitt
- Institute for Evolutionary Biology and Ecology University of Bonn Bonn Germany
| | - Timo Thünken
- Institute for Evolutionary Biology and Ecology University of Bonn Bonn Germany
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3
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Romano D, Stefanini C. Unveiling social distancing mechanisms via a fish-robot hybrid interaction. BIOLOGICAL CYBERNETICS 2021; 115:565-573. [PMID: 33730211 PMCID: PMC8960612 DOI: 10.1007/s00422-021-00867-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 02/20/2021] [Indexed: 06/12/2023]
Abstract
Pathogen transmission is a major limit of social species. Social distancing, a behavioural-based response to diseases, has been regularly reported in nature. However, the identification of distinctive stimuli associated with an infectious disease represents a challenging task for host species, whose cognitive mechanisms are still poorly understood. Herein, the social fish Paracheirodon innesi, was selected as model organism to investigate animal abilities in exploiting visual information to identify and promote social distancing towards potentially infected conspecifics. To address this, a robotic fish replica mimicking a healthy P. innesi subject, and another mimicking P. innesi with morphological and/or locomotion anomalies were developed. P. innesi individuals were attracted by the healthy fish replica, while they avoided the fish replica with morphological abnormalities, as well as the fish replica with an intact appearance, but performing locomotion anomalies (both symptoms associated with a microsporidian parasite infesting P. innesi and other fish). Furthermore, the fish replica presenting both morphology and locomotion anomalies in conjunction, triggered a significantly stronger social distancing response. This confirms the hypothesis that group living animals overgeneralize cues that can be related with a disease to minimize transmission, and highlights the important role of visual cues in infection risk contexts. This study prompts more attention on the role of behavioural-based strategies to avoid pathogen/parasite diffusion, and can be used to optimize computational approaches to model disease dynamics.
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Affiliation(s)
- Donato Romano
- The BioRobotics Institute, Sant'Anna School of Advanced Studies, Viale Rinaldo Piaggio 34, 56025, Pontedera, Pisa, Italy.
- Department of Excellence in Robotics and AI, Sant'Anna School of Advanced Studies, 56127, Pisa, Italy.
| | - Cesare Stefanini
- The BioRobotics Institute, Sant'Anna School of Advanced Studies, Viale Rinaldo Piaggio 34, 56025, Pontedera, Pisa, Italy
- Department of Excellence in Robotics and AI, Sant'Anna School of Advanced Studies, 56127, Pisa, Italy
- Healthcare Engineering Innovation Center (HEIC), Khalifa University, Abu Dhabi, UAE
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4
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Culbert BM, Tsui N, Balshine S. Learning performance is associated with social preferences in a group-living fish. Behav Processes 2021; 191:104464. [PMID: 34329728 DOI: 10.1016/j.beproc.2021.104464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 06/13/2021] [Accepted: 07/23/2021] [Indexed: 10/20/2022]
Abstract
Many animals live in groups yet grouping tendencies and preferences for groups of different sizes vary considerably between individuals. This variation reflects, at least in part, differences in how individuals evaluate and perceive their physical surroundings and their social environment. While such differences are likely related to individual variation in cognition, there have been few studies that have directly investigated how cognitive abilities are linked to individual grouping decisions. Therefore, in this study we assessed whether performance on a foraging-based reversal learning task is related to grouping preferences (a group of three fish versus a single fish) in a group-living cichlid fish, Neolamprologus pulcher. While most fish preferred to associate with the group over a single fish, individuals that completed the reversal learning task the quickest were the least interested in the group under elevated predation risk. In addition, fish that quickly completed the reversal learning task also adjusted their grouping preferences the most when predation risk increased. This result suggests that the observed relationship between learning performance and grouping decisions may be linked to individual differences in behavioural flexibility. Overall, our results offer valuable insight into the potential factors that underlie inter-individual variation in grouping decisions.
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Affiliation(s)
- Brett M Culbert
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario, Canada.
| | - Nicholas Tsui
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario, Canada
| | - Sigal Balshine
- Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario, Canada
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5
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Dynamic visual noise promotes social attraction, but does not affect group size preference, in a shoaling fish. Anim Behav 2021. [DOI: 10.1016/j.anbehav.2021.04.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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Gómez-Laplaza LM, Gerlai R. Food Quantity Discrimination in Angelfish ( Pterophyllum scalare): The Role of Number, Density, Size and Area Occupied by the Food Items. Front Behav Neurosci 2020; 14:106. [PMID: 32655384 PMCID: PMC7324792 DOI: 10.3389/fnbeh.2020.00106] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 05/28/2020] [Indexed: 11/29/2022] Open
Abstract
Quantity discrimination, the ability to identify, process, and respond to differences in number, has been shown in a variety of animal species and may have fitness value. In fish, the ability to distinguish between numerically different shoals has been well studied. However, little work has been devoted to the investigation of such ability in a foraging context. Nevertheless, angelfish (Pterophyllum scalare) have been previously shown to be able to discriminate numerically different sets of food items, with variables such as size and density of the food items playing important roles in making the choice. Here, we examine the possible role of other numerical and non-numerical variables. Using a spontaneous binary choice task, we contrasted sets of food items differing in specifically controlled ways: (1) different numerical size but equal inter-item distance; (2) different numerical size and different inter-item distance; and (3) identical total contour length and area occupied but different individual food size and inter-food distance between the contrasted food sets. In Experiment 1, angelfish were found to prefer the sets with a large number of food items. In Experiment 2, they preferred the numerically smaller sets with clustered items to the numerically larger sets with scattered items, but only when the sets were in the large number range (10 vs. 5 food items). Finally, in Experiment 3 fish preferred numerically smaller sets with large-sized and scattered food items in the large number range sets. We conclude that food item number, density, and size may not be considered individually by angelfish, but instead, the fish respond to all these factors attempting to maximize energy gained from eating the food while minimizing energy expenditure collecting and/or protecting the food.
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Affiliation(s)
| | - Robert Gerlai
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
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7
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Impact of social rearing-environment on performance in a complex maze in females of a cichlid fish. Behav Processes 2019; 167:103915. [PMID: 31349022 DOI: 10.1016/j.beproc.2019.103915] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 07/22/2019] [Accepted: 07/22/2019] [Indexed: 11/22/2022]
Abstract
Spatial orientation is an important skill as it improves, for example, foraging, localisation of recourses, predator avoidance or navigation. Habitat complexity positively affects spatial abilities in various fish species with a more complex environment promoting learning ability. However, to what extent a complex social environment affects cognitive abilities in fishes has received less attention. Here, we investigated differences in maze performance of adult females of the West African cichlid fish Pelvicachromis taeniatus, which had been reared and maintained either in a group or in isolation from an early age on. Fish had to master the route through a maze in order to gain a food reward. Our results indicate marked differences in performance contingent upon social rearing-environment: isolation fish ran successful trials (i.e. locating the food reward) significantly more often than group fish and were faster during trials, also in a reversed maze. However, the number of mistakes did not differ between isolation and group fish and the time needed to relocate the food reward did not diminish with elapsed training days. In a second experiment, the activity of group and isolation fish was analysed in an open field test. Here, isolation fish were less active than group fish. We discuss different possibilities for performance differences of group and isolation fish including enhanced cognitive abilities of isolation fish, motivational/emotional differences and hyperactivity.
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8
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Raveh S, Langen K, Bakker TCM, Josephs C, Frommen JG. Oddity, predation risk and social decisions in aquatic invertebrates. Ethology 2018. [DOI: 10.1111/eth.12835] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shirley Raveh
- Division of Behavioural Ecology, Institute of Ecology and Evolution; University of Bern; Hinterkappelen Switzerland
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences; University of Glasgow; Glasgow UK
| | - Kathrin Langen
- Institute for Evolutionary Biology and Ecology; University of Bonn; Bonn Germany
- Zoological Research Museum Alexander Koenig; Leibniz Institute for Animal Biodiversity; Bonn Germany
| | - Theo C. M. Bakker
- Institute for Evolutionary Biology and Ecology; University of Bonn; Bonn Germany
| | - Christian Josephs
- Institute for Evolutionary Biology and Ecology; University of Bonn; Bonn Germany
| | - Joachim G. Frommen
- Division of Behavioural Ecology, Institute of Ecology and Evolution; University of Bern; Hinterkappelen Switzerland
- Institute for Evolutionary Biology and Ecology; University of Bonn; Bonn Germany
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9
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Bai Y, Tang ZH, Fu SJ. Numerical ability in fish species: preference between shoals of different sizes varies among singletons, conspecific dyads and heterospecific dyads. Anim Cogn 2018; 22:133-143. [PMID: 30542940 DOI: 10.1007/s10071-018-1229-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 11/11/2018] [Accepted: 12/10/2018] [Indexed: 12/28/2022]
Abstract
Group living confers ecological benefits, and the associated fitness gain may be positively related to the size of the group. Thus, the ability to discriminate numerical differences may confer important fitness advantages in social fish. There is evidence that this ability can be improved by behavioral interactions among individuals of the same species. Here, we looked for this effect in both conspecific and heterospecific dyads. In Chinese bream and grass carp, we measured the sociability and shoal preferences of singletons, conspecific dyads and heterospecific dyads presented with different numerical comparisons (0 vs 8, 2 vs 8, 4 vs 8, 6 vs 8 and 8 vs 8). Chinese bream generally showed higher sociability than did grass carp, but grass carp in heterospecific dyads showed improved sociability that was similar to that of Chinese bream. Among the comparisons, both grass carp and Chinese bream singletons could only discriminate the comparison of 2 vs 8, suggesting lower quantitative abilities in these fish species compared to other fish species. Grass carp dyads were more successful in discriminating between 6 and 8 than were singletons, although no such improvement was observed in their discrimination between 4 and 8. In contrast, numerical ability did not vary between singletons and conspecific dyads in Chinese bream. More interestingly, Chinese bream and grass carp in heterospecific groups could discriminate between 4 and 8, but neither species showed a preference when presented with 6 and 8. Our results suggested that interaction between conspecific grass carp might improve their joint numerical ability, and a similar process might occur in Chinese bream in heterospecific dyads. However, the mechanism underlying the differences in improvements in numerical ability requires further investigation. The improved cognitive ability of heterospecific dyads might yield important fitness advantages for predator avoidance and efficient foraging in the wild.
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Affiliation(s)
- Yang Bai
- Laboratory of Evolutionary Physiology and Behavior, Chongqing Key Laboratory of Animal Biology, Chongqing Normal University, Chongqing, 401331, China
| | - Zhong-Hua Tang
- Laboratory of Evolutionary Physiology and Behavior, Chongqing Key Laboratory of Animal Biology, Chongqing Normal University, Chongqing, 401331, China
| | - Shi-Jian Fu
- Laboratory of Evolutionary Physiology and Behavior, Chongqing Key Laboratory of Animal Biology, Chongqing Normal University, Chongqing, 401331, China.
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10
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Quantity discrimination in angelfish, Pterophyllum scalare: a novel approach with food as the discriminant. Anim Behav 2018. [DOI: 10.1016/j.anbehav.2018.06.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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11
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Anders N, Fernö A, Humborstad OB, Løkkeborg S, Rieucau G, Utne-Palm AC. Size-dependent social attraction and repulsion explains the decision of Atlantic cod Gadus morhua to enter baited pots. JOURNAL OF FISH BIOLOGY 2017; 91:1569-1581. [PMID: 29139117 DOI: 10.1111/jfb.13453] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 08/07/2017] [Indexed: 06/07/2023]
Abstract
The present study tested whether the presence of already retained fishes inside baited fish pots acted as a social attraction and affected the entrance probability of Atlantic cod Gadus morhua in a fjord in northern Norway. Video analysis revealed that the probability of an entrance initially increased with the presence of low numbers of fishes inside the pot, but subsequently decreased at a critical number of caught fishes. The critical number was dependent on the size of the G. morhua attempting to enter. This demonstrates that social attraction and repulsion play a role in G. morhua pot fishing and has important implications for the capture efficiency of fisheries executed with pots.
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Affiliation(s)
- N Anders
- University of Bergen, Department of Biology, PO Box 7803, N-5020, Bergen, Norway
- Institute of Marine Research, PO Box 1870, N-5817, Bergen, Norway
| | - A Fernö
- University of Bergen, Department of Biology, PO Box 7803, N-5020, Bergen, Norway
| | - O-B Humborstad
- Institute of Marine Research, PO Box 1870, N-5817, Bergen, Norway
| | - S Løkkeborg
- Institute of Marine Research, PO Box 1870, N-5817, Bergen, Norway
| | - G Rieucau
- Louisiana Universities Marine Consortium, Chauvin, LA, 70344, U.S.A
| | - A C Utne-Palm
- Institute of Marine Research, PO Box 1870, N-5817, Bergen, Norway
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12
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13
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Sex composition modulates the effects of familiarity in new environment. Behav Processes 2017; 140:133-138. [DOI: 10.1016/j.beproc.2017.05.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 04/06/2017] [Accepted: 05/02/2017] [Indexed: 12/29/2022]
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14
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Cattelan S, Lucon-Xiccato T, Pilastro A, Griggio M. Is the mirror test a valid measure of fish sociability? Anim Behav 2017. [DOI: 10.1016/j.anbehav.2017.03.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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15
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Lucon-Xiccato T, Bisazza A. Sex differences in spatial abilities and cognitive flexibility in the guppy. Anim Behav 2017. [DOI: 10.1016/j.anbehav.2016.10.026] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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16
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Oshima M, di Pauli von Treuheim T, Carroll J, Hanlon RT, Walters ET, Crook RJ. Peripheral injury alters schooling behavior in squid, Doryteuthis pealeii. Behav Processes 2016; 128:89-95. [PMID: 27108689 DOI: 10.1016/j.beproc.2016.04.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 03/31/2016] [Accepted: 04/13/2016] [Indexed: 11/16/2022]
Abstract
Animals with detectable injuries are at escalated threat of predation. The anti-predation tactic of schooling reduces individual predation risk overall, but it is not known how schooling behavior affects injured animals, or whether risks are reduced equally for injured animals versus other school members. In this laboratory study we examined the effects of minor fin injury on schooling decisions made by squid. Schooling behavior of groups of squid, in which one member was injured, was monitored over 24h. Injured squid were more likely to be members of a school shortly after injury (0.5-2h), but there were no differences compared with sham-injured squid at longer time points (6-24h). Overall, the presence of an injured conspecific increased the probability that a school would form, irrespective of whether the injured squid was a member of the school. When groups containing one injured squid were exposed to a predator cue, injured squid were more likely to join the school, but their position depended on whether the threat was a proximate visual cue or olfactory cue. We found no evidence that injured squid oriented themselves to conceal their injury from salient threats. Overall we conclude that nociceptive sensitization after injury changes grouping behaviors in ways that are likely to be adaptive.
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Affiliation(s)
- Megumi Oshima
- Marine Science Department, Coastal Carolina University, 301 Allied Drive, Conway, SC 29526, United States
| | | | - Julia Carroll
- Biology Department, Williams College, 59 Lab Campus Drive, Williamstown, MA 01267, United States
| | - Roger T Hanlon
- Program in Sensory Physiology and Behavior, Marine Biological Laboratory, 7 MBL St Woods Hole, MA, United States
| | - Edgar T Walters
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, 6431 Fannin St, Houston, TX, 77030, United States
| | - Robyn J Crook
- Department of Biology, San Francisco State University, 1600 Holloway Ave, San Francisco CA 94132, United States.
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17
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Gómez-Laplaza LM, Gerlai R. Discrimination of large quantities: Weber's law and short-term memory in angelfish, Pterophyllum scalare. Anim Behav 2016. [DOI: 10.1016/j.anbehav.2015.10.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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18
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Thünken T, Hesse S, Bakker TC, Baldauf SA. Benefits of kin shoaling in a cichlid fish: familiar and related juveniles show better growth. Behav Ecol 2015. [DOI: 10.1093/beheco/arv166] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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Kimbell HS, Morrell LJ. 'Selfish herds' of guppies follow complex movement rules, but not when information is limited. Proc Biol Sci 2015; 282:20151558. [PMID: 26400742 DOI: 10.1098/rspb.2015.1558] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Under the threat of predation, animals can decrease their level of risk by moving towards other individuals to form compact groups. A significant body of theoretical work has proposed multiple movement rules, varying in complexity, which might underlie this process of aggregation. However, if and how animals use these rules to form compact groups is still not well understood, and how environmental factors affect the use of these rules even less so. Here, we evaluate the success of different movement rules, by comparing their predictions with the movement seen when shoals of guppies (Poecilia reticulata) form under the threat of predation. We repeated the experiment in a turbid environment to assess how the use of the movement rules changed when visual information is reduced. During a simulated predator attack, guppies in clear water used complex rules that took multiple neighbours into account, forming compact groups. In turbid water, the difference between all rule predictions and fish movement paths increased, particularly for complex rules, and the resulting shoals were more fragmented than in clear water. We conclude that guppies are able to use complex rules to form dense aggregations, but that environmental factors can limit their ability to do so.
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Affiliation(s)
- Helen S Kimbell
- School of Biological, Biomedical and Environmental Sciences, University of Hull, Yorkshire, UK
| | - Lesley J Morrell
- School of Biological, Biomedical and Environmental Sciences, University of Hull, Yorkshire, UK
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20
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Quantification acuity in spontaneous shoaling decisions of three-spined sticklebacks. Anim Cogn 2015; 18:1125-31. [PMID: 26099740 DOI: 10.1007/s10071-015-0884-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 05/28/2015] [Accepted: 06/08/2015] [Indexed: 10/23/2022]
Abstract
The ability to discriminate between different quantities is widespread throughout the animal kingdom, and the underlying mechanisms of quantity discrimination are currently intensely discussed. In contrast, questions elucidating the limits of quantity estimation received rather little attention so far. Here, we examined fine-tuned quantity estimation in the three-spined stickleback (Gasterosteus aculeatus) in a natural context, i.e. during shoaling decisions. Wild-caught focal fish were given the spontaneous choice between two shoals which differed in group size by 1 fish (0 vs. 1, 1 vs. 2, 2 vs. 3, 3 vs. 4, 4 vs. 5, 5 vs. 6 and 6 vs. 7), based on visual assessment. The results show that sticklebacks generally prefer to shoal with the larger group. They discriminated numerical contrasts up to 6 versus 7, equalling a numerical ratio of 0.86. Preference patterns followed Weber's law, i.e. decreased with increasing numerical ratio. This pattern was found across all numerical conditions as well as within the small number range (ranging from 1 vs. 2 to 3 vs. 4). The results suggest that wild-caught three-spined sticklebacks are spontaneously able (i.e. without prior learning) to detect subtle differences in shoal sizes. Further, they confirm findings of previous studies highlighting the contribution of the analogue magnitude system to quantity estimation in fishes.
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