Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 278 (1719), 2761-7

Bats Are Able to Maintain Long-Term Social Relationships Despite the High Fission-Fusion Dynamics of Their Groups

Affiliations

Bats Are Able to Maintain Long-Term Social Relationships Despite the High Fission-Fusion Dynamics of Their Groups

Gerald Kerth et al. Proc Biol Sci.

Abstract

Elephants, dolphins, as well as some carnivores and primates maintain social links despite their frequent splitting and merging in groups of variable composition, a phenomenon known as fission-fusion. Information on the dynamics of social links and interactions among individuals is of high importance to the understanding of the evolution of animal sociality, including that of humans. However, detailed long-term data on such dynamics in wild mammals with fully known demography and kin structures are scarce. Applying a weighted network analysis on 20,500 individual roosting observations over 5 years, we show that in two wild Bechstein's bat colonies with high fission-fusion dynamics, individuals of different age, size, reproductive status and relatedness maintain long-term social relationships. In the larger colony, we detected two stable subunits, each comprising bats from several family lineages. Links between these subunits were mainly maintained by older bats and persisted over all years. Moreover, we show that the full details of the social structure become apparent only when large datasets are used. The stable multi-level social structures in Bechstein's bat colonies resemble that of elephants, dolphins and some primates. Our findings thus may shed new light on the link between social complexity and social cognition in mammals.

Figures

Figure 1.
Figure 1.
Schematic of the fission–fusion dynamics of a representative Bechstein's bat colony and its social structure. (a) Typical roost occupation pattern for the colony (one to three roosting groups, occupying different roosts) on three randomly chosen census days (i, j, k). (b) Underlying social structure (with distinct communities) that may arise from this daily pattern, identified through a weighted network analysis [–16] based on the roosting associations of the colony members over the entire season (five months). For details of the methods, see the electronic supplementary material.
Figure 2.
Figure 2.
From pairwise association to social networks in two Bechstein's bat colonies. The upper graphs show the frequency distribution of the strength of associations (Iij) in the colonies BS (left) and GB2 (right), in the year 2007. The lower graphs show the corresponding social networks in each colony. The social network is fully connected as all pairs of bats roosted together at least once. For clarity purposes, however, only links belonging to the upper mode of the distribution are included in the visualization (strong links), even though all (weak and strong) links are used for the calculations. Networks layouts were produced with Cuttlefish (http://cuttlefish.sourceforge.net). GB2 forms two distinct communities whereas no modular structure is visible in BS. The bats (nodes of the network) are identified by their printed PIT-tag numbers. Different colours of the nodes depict different matrilines within each colony. Members of a given matriline always belong to the same community in GB2.
Figure 3.
Figure 3.
Genetic and social relationships in the Bechstein's bat colony GB2. The figure shows the genealogy and community membership of 61 adult female Bechstein's bats living in the colony GB2 during at least one year between 2004 and 2008. Broken circles symbolize three mothers that lived in the colony before 2004 but were not present during the study period. Bats born after 1995 (the year of birth is given on the right-hand side of the graph) are assigned to a specific mother or daughter using 11 polymorphic nuclear microsatellites [13]. In this colony two distinct mtDNA lineages occur [13], indicated by different colours (orange and dark blue). ‘Switchers’ are bats that have changed their community membership during the 5 years of the study.

Similar articles

See all similar articles

Cited by 29 PubMed Central articles

See all "Cited by" articles

Publication types

LinkOut - more resources

Feedback