Behavioural synchronization of large‐scale animal movements – disperse alone, but migrate together?

Abstract

Dispersal and migration are superficially similar large-scale movements, but which appear to differ in terms of inter-individual behavioural synchronization. Seasonal migration is a striking example of coordinated behaviour, enabling animal populations to track spatio-temporal variation in ecological conditions. By contrast, for dispersal, while social context may influence an individual's emigration and settlement decisions, transience is believed to be mostly a solitary behaviour. Here, we review differences in drivers that may explain why migration appears to be more synchronized than dispersal. We derive the prediction that the contrast in the importance of behavioural synchronization between dispersal and migration is linked to differences in the selection pressures that drive their respective evolution. Although documented examples of collective dispersal are rare, this behaviour may be more common than currently believed, with important consequences for eco-evolutionary dynamics. Crucially, to date, there is little available theory for predicting when we should expect collective dispersal to evolve, and we also lack empirical data to test predictions across species. By reviewing the state of the art in research on migration and collective movements, we identify how we can harness these advances, both in terms of theory and data collection, to broaden our understanding of synchronized dispersal and its importance in the context of global change.

Genetics of dispersal

“…Parent–offspring and sib–sib analyses typically yield higher heritability estimates than Animal Models (McCleery et al, ; Charmantier et al, ; Doligez et al, ), due to maternal and common environment effects (van Noordwijk et al, ; Zera & Brisson, ). Further, heritability estimates may also be inflated by biases in detectability due to limited study areas (van Noordwijk, ; Doligez & Pärt, ) and to more numerous social interactions among siblings synchronizing their movements (Matthysen, Van de Casteele & Adriaensen, ; Cote et al, ). As a whole, heritability studies suggest that variation in dispersal can arise as a result of additive genetic variation, but also that in many cases much of the phenotypic variation is explained by environmental variation, including transgenerational effects (Appendix I).…”

“…In fact, both the evolution of increased or decreased dispersal can be predicted for species expanding over fragmented landscapes or experiencing a sudden fragmentation event (Leimar & Norberg, ; Heino & Hanski, ; Gyllenberg, Parvinen & Dieckmann, ; Travis, Smith & Ranwala, ; Poethke, Gros & Hovestadt, ; Cote et al, ). On the one hand, as habitat fragmentation imposes diverse costs during transfer (Bonte et al, ; Baguette & Van Dyck, ), we can simply expect a reduction in dispersal propensity (reviewed in Cote et al, ). In the bog fritillary butterfly Boloria ( Proclossiana ) eunomia , dispersal propensity was dramatically decreased by landscape fragmentation, which induced higher dispersal mortality (Schtickzelle, Mennechez & Baguette, ; Schtickzelle et al, ).…”

“…Improved settlement capacities through increased perceptual ability are found in speckled wood butterflies Pararge aegeria in fragmented relative to more continuous habitat (Öckinger & Van Dyck, ). Whether dispersal will increase or decrease in response to habitat fragmentation will depend on factors such as the proportion of empty habitats to colonize, the degree of environmental heterogeneity and, importantly, the amount of genetic variation in dispersal traits (Cheptou et al, ; Cote et al, ).…”

Demographic and spatial determinants of hybridization rate

“…Our findings of reduced hybridization rates observed when the rare species is clustered can be viewed as a beneficial effect of group dispersal (García & Grivet ; Cote et al . ), since this mechanism results in aggregated patterns of related dispersers. Here, we have shown that this provides a local pollen pool biased towards more conspecific pollen, resulting in increased protection against hybridization.…”

Ecological and demographic correlates of cooperation from individual to budding dispersal

“…Goodnight, ; Gardner & West, ), a behaviour also observed in other social species such as in bacteria ( Myxococcus xanthus ; Velicer & Yuen‐Tsu, ) and banded mongooses ( Mungos mungo ; Cant et al ., ; Nichols et al ., ). This empirical evidence suggests an alternative evolutionary path to the emergence of cooperation, in which cooperation is mediated by the budding mode of dispersal, and yet this problem has received surprisingly little attention (for a review, see Cote et al ., ). Specifically, how different ecological and demographic factors, such as environmental stability and the cost of dispersal, influence the evolution of budding dispersal and cooperation remains unexplored.…”