The roosting spatial network of a bird-predator bat.

The use of roosting sites by animal societies is important in conservation biology, animal behavior, and epidemiology. The giant noctule bat (Nyctalus lasiopterus) constitutes fission-fusion societies whose members spread every day in multiple trees for shelter. To assess how the pattern of roosting use determines the potential for information exchange or disease spreading, we applied the framework of complex networks. We found a social and spatial segregation of the population in well-defined modules or compartments, formed by groups of bats sharing the same trees. Inside each module, we revealed an asymmetric use of trees by bats representative of a nested pattern. By applying a simple epidemiological model, we show that there is a strong correlation between network structure and the rate and shape of infection dynamics. This modular structure slows down the spread of diseases and the exchange of information through the entire network. The implication for management is complex, affecting differently the cohesion inside and among colonies and the transmission of parasites and diseases. Network analysis can hence be applied to quantifying the conservation status of individual trees used by species depending on hollows for shelter.

[1]  M. Newman,et al.  The structure of scientific collaboration networks. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[2]  A. Barabasi,et al.  Lethality and centrality in protein networks , 2001, Nature.

[3]  R. Guimerà,et al.  The worldwide air transportation network: Anomalous centrality, community structure, and cities' global roles , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[4]  K. Holekamp,et al.  INDIVIDUAL VARIATION IN SPACE USE BY FEMALE SPOTTED HYENAS , 2003 .

[5]  Gerald S. Wilkinson,et al.  Information transfer at evening bat colonies , 1992, Animal Behaviour.

[6]  R. Guimerà,et al.  Functional cartography of complex metabolic networks , 2005, Nature.

[7]  W. Fagan,et al.  Living in the branches: population dynamics and ecological processes in dendritic networks. , 2007, Ecology letters.

[8]  J. Bascompte,et al.  Invariant properties in coevolutionary networks of plant-animal interactions , 2002 .

[9]  D. Lindenmayer,et al.  Tree Hollows and Wildlife Conservation in Australia , 2002 .

[10]  L. Meyers,et al.  When individual behaviour matters: homogeneous and network models in epidemiology , 2007, Journal of The Royal Society Interface.

[11]  R. Arlettaz,et al.  Bats' Conquest of a Formidable Foraging Niche: The Myriads of Nocturnally Migrating Songbirds , 2007, PloS one.

[12]  B. Raymond,et al.  Applying Network Analysis to the Conservation of Habitat Trees in Urban Environments: a Case Study from Brisbane, Australia , 2006, Conservation biology : the journal of the Society for Conservation Biology.

[13]  R. Shine,et al.  Out on a limb: Conservation implications of tree-hollow use by a threatened snake species (Hoplocephalus bungaroides: Serpentes, Elapidae) , 1997 .

[14]  Carlos J. Melián,et al.  The nested assembly of plant–animal mutualistic networks , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[15]  Gang Li,et al.  Diet, Echolocation Calls, and Phylogenetic Affinities of the Great Evening Bat (Ia io; Vespertilionidae): Another Carnivorous Bat , 2007 .

[16]  G. Kerth,et al.  The reproductive success of the parasitic bat fly Basilia nana (Diptera: Nycteribiidae) is affected by the low roost fidelity of its host, the Bechstein’s bat (Myotis bechsteinii) , 2006, Parasitology Research.

[17]  Jordi Bascompte,et al.  Spatial network structure and amphibian persistence in stochastic environments , 2006, Proceedings of the Royal Society B: Biological Sciences.

[18]  C. D. Gelatt,et al.  Optimization by Simulated Annealing , 1983, Science.

[19]  Albert-László Barabási,et al.  Error and attack tolerance of complex networks , 2000, Nature.

[20]  Alessandro Vespignani,et al.  Epidemic dynamics and endemic states in complex networks. , 2001, Physical review. E, Statistical, nonlinear, and soft matter physics.

[21]  Gerald Kerth,et al.  Information transfer about roosts in female Bechstein's bats: an experimental field study , 2003, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[22]  G. Wardell-Johnson,et al.  Roost tree characteristics determine use by the white-striped freetail bat (Tadarida australis, Chiroptera: Molossidae) in suburban subtropical Brisbane, Australia , 2006 .

[23]  Roger Guimerà,et al.  Module identification in bipartite and directed networks. , 2007, Physical review. E, Statistical, nonlinear, and soft matter physics.

[24]  S. Low,et al.  The "robust yet fragile" nature of the Internet. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[25]  D. Lusseau.  Evidence for social role in a dolphin social network , 2006, Evolutionary Ecology.

[26]  P. Kaye.  Infectious diseases of humans: Dynamics and control , 1993 .

[27]  R. Albert,et al.  The large-scale organization of metabolic networks , 2000, Nature.

[28]  M E J Newman,et al.  Finding and evaluating community structure in networks. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[29]  Martin Rosvall,et al.  An information-theoretic framework for resolving community structure in complex networks , 2007, Proceedings of the National Academy of Sciences.

[30]  Timothy H. Keitt,et al.  LANDSCAPE CONNECTIVITY: A GRAPH‐THEORETIC PERSPECTIVE , 2001 .

[31]  G. Kerth,et al.  Roost selection and roost switching of female Bechstein’s bats (Myotis bechsteinii) as a strategy of parasite avoidance , 2007, Oecologia.

[32]  J. E. Cohen,et al.  Food webs and niche space. , 1979, Monographs in population biology.

[33]  R. May.  Food webs. , 1983, Science.

[34]  M. Rhodes.  Roost Fidelity and Fission–Fusion Dynamics of White-striped Free-tailed Bats (Tadarida australis) , 2007 .

[35]  Bernhard Voelkl,et al.  The influence of social structure on the propagation of social information in artificial primate groups: a graph-based simulation approach. , 2008, Journal of theoretical biology.

[36]  G. Kerth,et al.  Mean colony relatedness is a poor predictor of colony structure and female philopatry in the communally breeding Bechstein's bat (Myotis bechsteinii) , 2002, Behavioral Ecology and Sociobiology.

[37]  A. Popa-Lisseanu,et al.  Highly structured fission–fusion societies in an aerial-hawking, carnivorous bat , 2008, Animal Behaviour.

[38]  Jordi Bascompte,et al.  Asymmetric Coevolutionary Networks Facilitate Biodiversity Maintenance , 2006, Science.

[39]  Anne E. Pusey,et al.  Dominance rank influences female space use in wild chimpanzees, Pan troglodytes: towards an ideal despotic distribution , 2007, Animal Behaviour.

[40]  C. Ibáñez,et al.  Bat predation on nocturnally migrating birds , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[41]  M E J Newman,et al.  Modularity and community structure in networks. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[42]  L. Amaral,et al.  The web of human sexual contacts , 2001, Nature.

[43]  R. Paine.  Food Web Complexity and Species Diversity , 1966, The American Naturalist.

[44]  J. Bascompte,et al.  Structure in plant–animal interaction assemblages , 2006 .

[45]  Wirt Atmar,et al.  The measure of order and disorder in the distribution of species in fragmented habitat , 1993, Oecologia.

[46]  M. Gerstein,et al.  Genomic analysis of regulatory network dynamics reveals large topological changes , 2004, Nature.

[47]  J. Bascompte,et al.  The modularity of pollination networks , 2007, Proceedings of the National Academy of Sciences.

[48]  Albert-László Barabási,et al.  Internet: Diameter of the World-Wide Web , 1999, Nature.

[49]  Jasmine Novak,et al.  Geographic routing in social networks , 2005, Proc. Natl. Acad. Sci. USA.

[50]  Paulo Guimarães,et al.  Improving the analyses of nestedness for large sets of matrices , 2006, Environ. Model. Softw..

[51]  David Lusseau,et al.  A killer whale social network is vulnerable to targeted removals , 2006, Biology Letters.