Spatial reorganization during post-collapse population growth suggests conspecific attraction in baleen whale nursing grounds

Habitat use is strongly interlinked with population dynamics and plays an important role in population regulation. Animals frequently modify their habitat use behavior in response to major changes in population density. This is well studied in contexts wherein resources are limiting: for example, when changes in habitat use behavior reduce pressure from resource limitations. Situations wherein resource limitations are relaxed, such as upon recovery from severe declines, remain poorly studied. Here, we study how the spatial distribution of a nearly extirpated animal population changed during population recovery. We study a population of southern right whales ( Eubalaena australis ), a migratory species that was nearly extirpated by whaling. Using large-scale annual aerial survey data (1976–2023), we assess how spatial distribution patterns at nursing grounds changed as annual coastal abundances grew from few individuals to a few hundred. This includes assessment of the species’ characteristic site fidelity at a uniquely large spatiotemporal scale. We observed weaker fidelity to specific sites than generally assumed for Australian southern right whales and found strong indications that conspecific attraction influences the species’ coastal habitat selection. Distribution patterns initially displayed strong dispersal but became increasingly clustered coincident with substantial growth in annual whale abundances. This transition captures a rare example of a population crossing a behavioral threshold, possibly reflecting a switch in behavioral strategy or lack of conspecific cues. Our findings suggest that the behavioral processes governing habitat selection can shift with population density, driving substantial reorganization of populations’ spatial structure during substantial demographic change.