Glossary:Animal aggregations have very diverse spatial and temporal conformations and probably occur in a continuum depending to biotic and abiotic factors (Allee, 1931; Parrish and Hammer, 1997; Camazine et al., 2001; Krause and Ruxton, 2002; Costa, 2006). As a common trend, aggregation isdefined as a patch of a higher density of individuals than in the surrounding environment (Jeanson et al., 2005). Because aggregation promotes closeness and interactions between individuals, it is intimately linked to the study of sociality; but the vocabulary related to sociality and the limits of the terms used vary a lot according to specialty areas of each. Here, we define the sense of the terms used in the present document to avoid confusion and misinterpretation.
Solitary / Qualified individuals living alone or establishing contacts with conspecifics at the time of reproduction. However, solitary individuals may also present non-social aggregations(see below).Non-social aggregation / Temporal and spatial gathering of individuals in response of environmental heterogeneities such as patches of food, light or humidity, or physical constraints of the environment such as marine currents. Solitary species may present non-social aggregations but it requires tolerance to the proximity of its neighbors (Wiens, 1976; Alldredge and Hammer, 1980).
Social aggregation / Temporal and spatial gathering of individuals with a mutual attraction. Further, the patterns of social aggregation are affected by the presence of conspecifics and interattractions between them, butresult also from the individual preferences for the environment. Social aggregation can lead, but not necessarily, to cooperative behaviors (see below).Social species with aggregative patterns are frequently called gregariousand also sometimes calledpre or parasocial (Parrish and Edelstein-Keshet, 1999; Jeanson et al., 2005; Sumpter, 2006; Thiel, 2011)
Subsociality / Subsociality is a degree of sociality including interattraction between individuals and parental care to young. In these family parent–offspring systems, parents can cooperate to build a nest, to forage for young or protect it. The length and complexity of care is variable depending on the species. Non-closely genetically related individuals are generally excluded of groups (Tallamy and Wood, 1986; Costa, 2006; Linsenmair, 2007; Thiel, 2011).
Bunching / Particular spatial conformation of gathering of individuals with a stacking of the bodies (see Fig. 1). Bunching represents a well-defined aggregate (synonym of cluster), regarded as a fully entity composed of several sub-units (i.e. individuals).
Crowding / Crowding represents a diffuse mass of individuals with high spatial and temporal amplitudes, according to the density of individuals, the frequency of contact, and the length of encounters. The term crowding is often associated to high densities (e.g. Ganter, 1984).
In some studies, crowding qualifies the saturation or the fullness of a place or a shelter (e.g. Amé et al., 2006). The term "crowd" can also be understood as a group without a social component. Hence it is a spatial description of the distribution of individuals and not a functional definition of the gathering of individuals.
Social information / Information generated by the presence or behavior of other individuals, whether provided intentionally or inadvertently by individuals (Danchin et al., 2004).
Cooperation / A strict definition to cooperation is difficult to establish because the same term describes different phenomena according to scientific specialty. However, cooperation is closely linked to the benefits of group living. This cooperation only implicates the presence of conspecifics (e.g. woodlice cooperate in aggregating to reduce desiccation) or exchange information, resources or services for reciprocal benefits (Alexander, 1974; Deneubourg et al., 2002; Clutton-Brock, 2009).
Thigmokinetic behavior / Behavior in response to a contact stimulus
Hygrokinteic behavior / Behavior in response to a humidity stimulus
Supralittoral zone / Area at the interface between the marine environment and the terrestrial environment. It is moistened, but never submerged, by the spray and strong tides.
Pleopodal lungs / Specialized respiratory structures of Oniscidea found in the pleopodexopodites (Schmidt and Wägele, 2001; Csonka et al., 2013).
Parturialmoult / In woodlice, moulting cyclechanges during reproduction. The parturialmoult is characterized by the development of the marsupium (brood pouch) in which eggs are laid before being incubated. The parturialmoult follows the preparturialintermoult which corresponds to the period of oocyte maturation and female receptivity to mating (Moreau and Rigaud, 2002; Kight, 2008).