Detecting range shifts in the remote Southern Ocean: First measurements for Oceania humpback whales

Ms Leena Riekkola¹, Dr Alexandre Zerbini^2,3, Dr Virginia  Andrews-Goff⁴, Assoc. Prof. Ari  Friedlaender⁵, Assoc. Prof Rochelle  Constantine¹

¹School of Biological Sciences, University of Auckland, Auckland, New Zealand, ²National Marine Mammal Laboratory – National Oceanic and Atmospheric Administration, Seattle, USA, ³Cascadia Research Collective, Olympia, USA, ⁴Australian Marine Mammal Centre – Australian Antarctic Division, Hobart, Australia, ⁵Institute of Marine Sciences – University of California, Santa Cruz, Santa Cruz, USA

To detect changes in species distribution we require a good understanding of their baseline distribution. Animal-borne loggers and movement models enable remote monitoring of animal distribution that would otherwise be hard to observe, such as for long ranging marine migrants.

We deployed 25 satellite tags on Oceania humpback whales at the Kermadec Islands (New Zealand) in 2015 to study their migration paths and distribution patterns within their Southern Ocean feeding grounds. We applied a state-space model to identify behavioural states in the data; transit, or search (indicative of foraging), and used statistical modelling and remotely sensed data to correlate whale behaviour with environmental parameters.

We identified two important feeding areas, one within Ross Sea and one within the Amundsen and Bellingshausen Seas regions. The choice of feeding area was influenced by the whales’ life history stage suggesting wider life-time use of the feeding grounds than other populations.

There were marked differences in the environmental features of the two feeding areas (e.g. oceanic vs. near continental shelf) and consequently the whales ended up utilising these areas very differently. Overall, whale behaviour was most strongly affected by season, time lagged ice-edge dynamics, and sea surface height.

The two feeding areas are experiencing different responses to climate change, which may elicit different responses from the whales. The observed behavioural plasticity should enable these animals to adapt to future changes, either by moving or prey switching, and with these first data on their distribution patterns within the Southern Ocean we can detect such changes.

Biography:

Leena Riekkola is a last-year PhD student at the University of Auckland, New Zealand. She uses spatial ecology, modelling and bio-logging tools to study animal movement and behaviour to inform conservation and management questions. In her PhD research she utilises satellite tracking data and spatial & statistical models to study the migration and habitat use patterns of Oceania humpback whales.