Abstract
The number and strength of social relationships are generally the products of group living trade-offs. However, they can be at least partially influenced by asocial factors such as the spatiotemporal opportunities for individuals to interact. We explored the social patterns of the largest population of Guiana dolphins—from dyadic interactions to the large-scale structure of their social network—considering their use of space and demographic changes during 6 years. We found that their society displays fission-fusion dynamics, characterized mainly by brief associations among individuals, and is weakly structured into four social modules. Spatial use and temporal demographic changes had minor effects on the patterns of associations among individuals. This suggests that the social modules unlikely represented spatiotemporal aggregations of individuals due to resource availability but rather involved social preferences among individuals. We show that Guiana dolphins can form social modules even in a large population with high ranging overlap and few demographic changes over time, although these social boundaries are blurred by the dynamic nature of the social relationships. Our findings illustrate and support the recent claims for the need of taking asocial processes in account when studying social structure of any animal species.
Significance statement
Animal social relationships are dynamic, usually reflecting group living trade-offs. Simultaneously, they are influenced by the opportunities individuals have to interact. Group membership—co-occurrence in the same space and time—is the most used proxy for describing animal social relationships. Therefore, if the spatiotemporal context is not accounted for, the resultant social structure can be misrepresented. Here, we explore the social patterns of Guiana dolphins explicitly accounting for space use and temporal demographic changes. We show the largest population of Guiana dolphins displays fission-fusion dynamics, while it is structured into four distinctive sets of individuals. By accounting for asocial processes, we suggest such social modules were unlikely to result from unequal opportunities to interact but rather involved social preferences among individuals. Our findings highlight the importance of separating asocial from social processes while studying animal societies.
This is a preview of subscription content,
to check access.



Similar content being viewed by others
References
Andrade LG, Lima IMS, Macedo HS, Carvalho RR, Lailson-Brito J Jr, Flach L, Azevedo AF (2014) Variation in Guiana dolphin (Sotalia guianensis) whistles: using a broadband recording system to analyze acoustic parameters in three areas of southeastern Brazil. Acta Ethol 18:47–57
Aureli F, Schaffner CM, Boesch C et al (2008) Fission-fusion dynamics: new research frameworks. Curr Anthropol 49:627–654
Bejder L, Fletcher D, Brager S (1998) A method of testing association patterns of social animals. Anim Behav 56:719–725
Bisi TL, Dorneles PR, Lailson-Brito J, Lepoint G, Azevedo AF, Flach L, Malm O, Das K (2013) Trophic relationships and habitat preferences of delphinids from southeastern Brazilian coast determined by carbon and nitrogen stable isotope composition. PLoS One 8:e82205
Burnham KP, Anderson DR (2002) Model selection and multimodel inference: a practical information-theory approach. Springer Verlag, New York
Cantor M, Wedekin L, Guimarães PR, Daura-Jorge FG, Rossi-Santos MR, Simões-Lopes PC (2012a) Disentangling social networks from spatiotemporal dynamics: the temporal structure of a dolphin society. Anim Behav 84:641–651
Cantor M, Wedekin LL, Daura-Jorge FG, Rossi-Santos MR, Simões-Lopes PC (2012b) Assessing population parameters and trends of Guiana dolphins (Sotalia guianensis): an eight-year mark-recapture study. Mar Mammal Sci 28:63–83
Castles M, Heinsohn R, Marshall HH, Lee AEG, Cowlishaw G, Carter AJ (2014) Social networks created with different techniques are not comparable. Anim Behav 96:59–67
Croft DP, Arrowsmith BJ, Bielby J, Skinner K, White E, Couzin ID, Magurran AE, Ramnarine I, Krause J (2003) Mechanisms underlying shoal composition in the Trinidadian guppy, Poecilia reticulata. Oikos 100:429–438
Croft DP, James R, Krause J (2008) Exploring animal social networks. Princeton University Press, Princeton
Csárdi G, Nepusz T (2006) The igraph software package for complex network research. Int J Complex Syst 1695:1–9
Daura-Jorge FG, Cantor M, Ingram SN, Lusseau D, Simões-Lopes PC (2012) The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen. Biol Lett 8:702–705
Development Core Team R (2008) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, http://www.R-project.org
Development Team QGIS (2014) QGIS Geographic Information System., Open Source Geospatial Foundation Project, http://qgis.osgeo.org/
Dias LA, Herzing D, Flach L (2009) Aggregations of estuarine dolphins (Sotalia guianensis), in Sepetiba Bay, Rio de Janeiro south-eastern Brazil: distribution patterns and ecological characteristics. J Mar Biol Assoc UK 89:967–973
Farine DR (2015) Proximity as a proxy for interactions: issues of scale in social network analysis. Anim Behav 104:e1–e5
Fieberg J, Kochanny CG (2005) Quantification of home range overlap: the importance of the utilization distribution. J Wildlife Manage 69:1346–1359
Flach L, Flach PA, Chiarello AG (2008a) Aspects of behavioural ecology of the estuarine dolphin (Sotalia guianensis) in Sepetiba Bay, southeast Brazil. Mar Mam Sci 24:503–515
Flach L, Flach PA, Chiarello AG (2008b) Density, abundance and distribution of the estuarine dolphin (Sotalia guianensis) in Sepetiba Bay, Brazil. J Cetacean Res Manage 10:31–36
Ford JKB, Ellis GM, Balcomb KC (2000) Killer whales. UBC Press, Vancouver
Gero S, Gordon J, Whitehead H (2015) Individualized social preferences and long-term social fidelity between social units of sperm whales. Anim Behav 102:15–23
Gowans S, Wursig B, Karczmarski L (2008) The social structure and strategies of dephinids: predictions based on an ecological framework. Adv in Mar Biol 53:195–294
Hammond PS, Mizroch SA, Donovan GP (1990) Individual recognition of cetaceans: use of photoidentification and other techniques to estimate population parameters. Rep Int Whal Comm Spec Issue 12:3–17
Hinde RA (1976) Interactions, relationships and social structure. Man 11:1–17
Hollatz C, Flach L, Baker CS (2011) Microsatellite data reveal fine genetic structure in male Guiana dolphins (Sotalia guianensis) in two geographically close embayment at south-eastern coast of Brazil. Mar Biol 158:927–933
Irvine AB, Scott MD, Wells RS, Kaufmann JH (1981) Movements and activities of the Atlantic bottlenose dolphin, Tursiops truncatus, near Sarasota, Florida. Fish B-NOAA 79:671–688
Krause J, Ruxton GD (2002) Living in groups. Oxford University Press, Oxford
Kurvers RHJM, Adamcyzk VMAP, Kraus RHS, Hoffman JI, van Wieren SE, van der Jeugd HP, Amos W, Prins HHT, Jonker RM (2013) Contrasting context dependence of familiarity and kinship in animal social networks. Anim Behav 86:993–1001
Leu ST, Farine DR, Wey TW, Sih A, Bull CM (2016) Environment modulates population social structure: experimental evidence from replicated social networks of wild lizards. Anim Behav 31:23–31
Lunardi DG, Ferreira RG (2014) Fission-fusion dynamics of Guiana dolphin (Sotalia guianensis) groups at Pipa Bay, Rio Grande do Norte, Brazil. Mar Mam Sci 30:1401–1416
Lusseau D, Wilson B, Hammond PS, Grellier K, Durban JW, Parsons KM, Barton TR, Thompson PM (2006) Quantifying the influence of sociality on population structure in bottlenose dolphins. J Anim Ecol 75:14–24
Nery MF, Simão SM (2012) Capture-recapture abundance estimate of Guiana dolphin in southeastern Brazil. Cienc Mar 38:529–541
Newman MEJ (2006) Modularity and community structure in networks. Proc Natl Acad Sci U S A 103:8577–8582
Oliveira ECS, Tardin RH, Poletto FR, Simão SM (2013) Coordinated feeding behavior of the Guiana dolphin, Sotalia guianensis (Cetacea: Delphinidae), in southeastern Brazil: comparison between populations. Zoologia 30:585–591
Opsahl T, Colizza V, Panzarasa P, Ramasco JJ (2008) Prominence and control: the weighted rich club effect. Phys Rev Lett 101:168702
Pinter-Wollman N, Hobson EA, Smith JE et al (2013) The dynamics of social networks: analytical, conceptual, and theoretical advances. Behav Ecol 25:242–255
Rosas FCW, Barreto AS, Monteiro-Filho ELDA (2003) Age and growth of the estuarine dolphin (Sotalia guianensis) (Cetacea, Delphinidae) on the Paraná coast, southern Brazil. Fish Bull 101(2):377–383
Rossi-Santos MR, Flores PAC (2009) Feeding strategies of the Guiana dolphins Sotalia guianensis. Open Mar Biol J 3:70–76
Santos MCO, Rosso S (2007) Ecological aspects of marine tucuxi dolphins (Sotalia guianensis) based on group size and composition in the Cananéia estuary, southeastern Brazil. Lat Am J Aquat Mam 6:71–82
Santos MCO, Rosso S (2008) Social organization of marine tucuxi dolphins, Sotalia guianensis, in the Cananéia estuary of southeastern Brazil. J Mammal 88:347–355
Silk MJ, Jackson AL, Croft DP, Colhoun K, Bearshop S (2015) The consequences of unidentifiable individuals for the analysis of an animal social network. Anim Behav 104:1–11
Stanford CB (1995) The influence of chimpanzee predation on group size and anti-predator behaviour in red colobus monkeys. Anim Behav 49:577–587
Stanley R (1995) DARWIN: identifying dolphins from dorsal fin images. Senior Thesis, Eckerd College
Titcomb EM, O’Connary G, Hartel EF, Mazzoli MS (2015) Social communities and spatiotemporal dynamics of association patterns in estuarine bottlenose dolphins. Mar Mam Sci 31:1314–1337
Wedekin LL, Daura-Jorge FG, Piacentini VQ, Simões-Lopes PC (2007) Seasonal variations in spatial usage by the estuarine dolphin, Sotalia guianensis (Van Benéden, 1864) (Cetacea; Delphinidae) at its southern limit of distribution. Brazil J Biol 67:1–8
Wells RS, Scott MD, Irvine AB (1987) The social structure of free-ranging bottlenose dolphins. In: Genoways HH (ed) Current mammalogy, vol 1. Plenum Press, New York, pp 247–305
Whitehead H (1995) Investigating structure and temporal scale in social organizations using identified individuals. Behav Ecol 6:199–208
Whitehead H (1999) Testing association patterns of social animals. Anim Behav 57:26–29
Whitehead H (2008) Analyzing animal societies: quantitative methods for vertebrate social analysis. University of Chicago Press, Chicago
Whitehead H (2009) SOCPROG programs: analyzing animal social structures. Behav Ecol Sociobiol 63:765–778
Whitehead H, Dufault S (1999) Techniques for analyzing vertebrate social structure using identified individuals: review and recommendations. Adv Stud Behav 28:33–74
Whitehead H, James R (2015) Generalized affiliation indices extract affiliations from social network data. Method Ecol Evol 6:836–844
Wiszniewski J, Allen SJ, Möller LM (2009) Social cohesion in a hierarchically structured embayment population of Indo-Pacific bottlenose dolphins. Anim Behav 77:1449–1457
Worton BJ (1998) Kernel methods for estimating the utilization distribution in home-range studies. Ecology 70:164–168
Yeates LC, Houser DS (2008) Thermal tolerance in bottlenose dolphins (Tursiops truncatus). J Exp Biol 211:3249–3257
Acknowledgments
We thank the Instituto Boto Cinza and their volunteers for the logistical support and assistance in the fieldwork; the two anonymous reviewers for the insightful comments that helped us improved our work; and E. Zwamborn for proofreading the manuscript. This study was carried out as part of a M.Sc. thesis in the Graduate Program in Ecology at the Universidade Federal de Santa Catarina, Brazil.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Ethical statement
All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted.
Funding
LBC was supported by CAPES (Brazil) scholarship. MC was supported by doctoral scholarships from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq Brazil) and Killam Trusts (Canada); LF received funds from CAPES; and PCSL received funds from CNPq.
Conflict of interest
The authors declare that they have no conflict of interest.
Ethical approval
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
Informed consent
Not applicable.
Additional information
Communicated by L. M. Moller
Electronic supplementary material
Below is the link to the electronic supplementary material.
ESM 1
(PDF 396 kb)
Rights and permissions
About this article
Cite this article
Beirão-Campos, L., Cantor, M., Flach, L. et al. Guiana dolphins form social modules in a large population with high ranging overlap and small demographic changes. Behav Ecol Sociobiol 70, 1821–1830 (2016). https://doi.org/10.1007/s00265-016-2188-x
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00265-016-2188-x