Agent-based modelling of southward coastal migration by humpback whale mother-calf pods off eastern Australia

Abstract

Humpback whales Megaptera novaeangliae encounter a variety of environmental conditions during seasonal migration between feeding grounds and breeding grounds. Relationships between environmental conditions and migratory movements are largely unknown due to a lack of oceanographic data coincident with their presence/absence. We begin to address this knowledge gap by developing a new agent-based modelling (ABM) approach designed to predict southward migration of mother–calf (MC) pairs along a stretch of the east Australian coast between the Great Barrier Reef (GBR) and Gold Coast (GC) bay, which includes a known resting area, Hervey Bay (HB). To assess our ability to reproduce observed migration patterns, numerical experiments were undertaken in which static (bathymetry) and dynamic (currents, sea surface temperature) variables between August and October 2017 governed movements. These experiments revealed how bathymetry influences HB usage, and a necessity to apply different directionality preferences to whales before and after negotiating HB, which appear to closely align with coastline orientation. The ABM provides a novel, suitable framework for simulating MC humpback whale migration, and an important first step in the development of predictive models of humpback whale behavior. Developing such tools is increasingly necessary to predict how changing ocean conditions are likely to affect their distribution.