Abstract
Animal social structure is shaped by environmental conditions, such as food availability. This is important as conditions are likely to change in the future and changes to social structure can have cascading ecological effects. Wood ants are a useful taxon for the study of the relationship between social structure and environmental conditions, as some populations form large nest networks and they are ecologically dominant in many northern hemisphere woodlands. Nest networks are formed when a colony inhabits more than one nest, known as polydomy. Polydomous colonies are composed of distinct sub-colonies that inhabit spatially distinct nests and that share resources with each other. In this study, we performed a controlled experiment on 10 polydomous wood ant (Formica lugubris) colonies to test how changing the resource environment affects the social structure of a polydomous colony. We took network maps of all colonies for 5years before the experiment to assess how the networks changes under natural conditions. After this period, we prevented ants from accessing an important food source for a year in five colonies and left the other five colonies undisturbed. We found that preventing access to an important food source causes polydomous wood ant colony networks to fragment into smaller components and begin foraging on previously unused food sources. These changes were not associated with a reduction in the growth of populations inhabiting individual nests (sub-colonies), foundation of new nests or survival, when compared with control colonies. Colony splitting likely occurred as the availability of food in each nest changed causing sub-colonies to change their inter-nest connections. Consequently, our results demonstrate that polydomous colonies can adjust to environmental changes by altering their social network.
Highlights
Changes to environmental conditions influence the composition of assemblages in different habitats, and affect the social structure of many animal societies (Sueur, Romano, Sosa, & Puga-Gonzalez, 2019)
We found that preventing access to an important food source causes polydomous wood ant colony networks to fragment into smaller components and begin foraging on previously unused food sources
Our study demonstrates that animal social networks adapt to changes in environmental conditions by changing their social network structure
Summary
Changes to environmental conditions influence the composition of assemblages in different habitats, and affect the social structure of many animal societies (Sueur, Romano, Sosa, & Puga-Gonzalez, 2019). There is some evidence from observational studies for the effect of resource distribution on social structure (Ansmann, Parra, Chilvers, & Lanyon, 2012; Foster et al, 2012; Henzi, Lusseau, Weingrill, Schaik, & Barrett, 2009; Silk, Croft, Tregenza, & Bearhop, 2014), few empirical tests exist (Bles, Deneubourg, & Nicolis, 2018; Firth & Sheldon, 2015; Sendova-Franks et al, 2010) This is because resource distribution is often difficult to manipulate in the field, and networks are time consuming to map, meaning that multiple time points or replication at the network level are often infeasible. Changes in resource distribution may cause significant disruption to trail networks To investigate this hypothesis, we experimentally manipulated resource availability in multiple polydomous ant colonies by removing a key food source. | Journal of Animal Ecolo gy 3 manipulation of resource distribution in polydomous colonies would cause changes to foraging networks and, subsequently, to inter-nest networks, as resource flow would be disrupted
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