Humpback whales are found in oceans all around the world. They perform seasonal migrations between summer feeding grounds in cold waters and winter breeding grounds in tropical waters. Migratory species such as humpbacks face several challenges related to changing environmental conditions which alter their migration timing.
In the paper "Humpback whales extend their stay in a breeding ground in the Tropical Eastern Pacific", the authors evaluated for the first time long-term trends of change in the time of arrival and departure of humpback whales to a breeding ground in the Pacific Southeast Region. Thirty-one years of data (1988–2018) for Gorgona Natural Park, Colombia, show that migration times have changed significantly. Whales arrive now almost one month earlier than 31 years ago, particularly groups without calves. Departure time from the area remained more or less the same.
This change is probably linked to ice-sheet mass changes in the previous autumn in Antarctica, which in turn affects the availability of prey. The less ice-sheet accumulation, the earlier whales arrive at Gorgona. The increase in population size over the past decades could also be related to arrival timing trends to Gorgona, but further analysis are needed to evaluate this pattern.
The findings pin down periods in which anthropogenic activities would need to be restricted in Colombian breeding grounds in order to reduce stress. The authors anticipate that such changes are occurring also in other regions and therefore urge researchers and managers to revise their data and adjust management plans accordingly. Broader ecological studies would be required to understand the causes and implications of such migratory shifts and international collaboration are fundamental.
Read the full paper in ICES Journal of Marine Science.
Humpback whale and calf, Gorgona National Park, Colombia. Photo: A. Parra.