Data with a bloody past has positive spin-off for endangered whale species

Information gathered by whalers in the 19th century to support the systematic killing of southern right whales in Australasian offshore waters has been used by NIWA scientists to better understand – and ultimately help protect – the present-day habitats of this endangered species.

Funded by the Australian Marine Mammal Centre, the scientists analysed historic documents compiled by the World Whaling History project to predict present-day distribution patterns of this whale species. These predictions have, in turn, helped to identify habitats that may be at risk from shipping traffic and climate change.

"The historic whaling data proved an absolute goldmine," says NIWA Marine Ecologist Dr Leigh Torres. "There is very little modern information on the offshore habitats of southern right whales. The historic documents are derived from vessel log books dating from between 1825 and 1888, in which whalers recorded their daily location and encounters and strikes of whales. They identify about 1800 locations where whale strikes or sightings occurred and – importantly – indicate about 23,000 places where whalers searched for, but failed to find, their target."

The research team used sophisticated computer models to combine the historic data with up-to-date oceanographic information and predict the location of present-day habitats.

"We identified a number of factors that can be used as consistent and influential predictors of whale distribution," Dr Torres says. "For example, the data showed that the southern right is very sensitive to ocean temperature and has a distinct upper temperature limit. This makes them very vulnerable to the impacts of climate change."

"Our discoveries will help inform future research on these poorly understood and culturally important animals."

The research team also investigated potential threats to the habitats that their models identified.

Habitat predictions were combined with shipping traffic data to identify areas where there is an elevated risk of vessel strike. Whales are occasionally killed or injured by ships.

"We identified two areas – one on the Chatham Rise east of New Zealand and one in the waters south of Australia – where busy shipping lanes intersect key whale habitats," Dr Torres says. "We believe our findings will form an important basis for future management and conservation efforts."

Computer models were also used to predict how habitats may be affected by changes in ocean temperature driven by climate change. Forecast ocean temperatures for the years 2090–2100, based on one of the Intergovernmental Panel on Climate Change's moderate climate-change scenarios, were fed into the distribution model and, says Dr Torres: "substantial shifts in whale habitat suitability and availability in the Australasian area were indicated".

These findings, recently published in the scientific journal Diversity and Distributions, are the culmination of three years' intensive work. Dr Torres believes they validate the use of unconventional datasets, such as historical exploitation data, to predict present-day species distribution.

"We are confident in the predictive capacity of our models, and we are now familiar with the nuances of the historical information, so it is possible we could apply this technique to the entire Southern Hemisphere – and to other species of whale," she says. 

Background information

Southern right whales are nationally endangered, and are at risk of extinction in New Zealand waters. Before whaling, there were an estimated 27,000 southern right whales in New Zealand and east Australian waters. Today, there are an estimated 908 southern right whales in New Zealand waters.

Sperm whales are classified as threatened, which means they are likely to become endangered. The number of sperm whales in New Zealand waters is unknown, but a recent estimate placed the global population at about 32 per cent of the pre-whaling figure.