Mammal Research Institute of the University of Pretoria
October 09, 2015 by dyertrust
Meredith Thornton, Research Coordinator
Dyer Island Conservation Trust
The Dyer Island Conservation Trust has a long-standing relationship with the Mammal Research Institute of the University of Pretoria. Every year around this time we provide support to their team of researchers from their Whale Unit while they are conducting their annual aerial survey for southern right whales.
Dr Ken Findlay and his team were based at the Great White House for two nights this week, using the accommodation and restaurant as their base for downloading 100s of photographs, punching data and preparing for the next leg of their journey.
This year saw them completing the 37th consecutive annual survey which has resulted in one of the longest ever such data sets in the world!
They used a Bell Jet Ranger helicopter and surveyed from George to Muizenberg. They usually search for whales at around 1000ft above sea level, dropping down to around 400-600 feet when they need to collect photographs.
All species of whales are recorded, but only southern right whale cow-calf pairs and brindle adults are photographed. Luckily for the researchers every right whale is born with a unique pattern of roughened skin patches on its head called callosities. These callosities become covered with small, creamy-coloured crab-like creatures (cyamids) that eat whale skin and make the callosities easily visible to the human eye.
These photographs are added to the Whale Units catalogue of animals and the data are used to answer all sorts of questions on survival, births, deaths, calving intervals, age at first breeding, the numbers of animals in the population etc. For example, as a result of these studies we now know that most southern right whales have a breeding cycle of 3 years they are pregnant for a year, produce a calf in the 2nd year and rest, restoring their body condition, for the 3rd year. We also know that cows tend to come back to the same bays to nurse year-after-year and that there is a general westward movement along the coastline of animals towards the end of the whale season.
While last year was a so-called bumper year with record numbers of animals photographed, this year has shown much lower numbers of animals. The population has shown a steady increase of 7.5% and has been recovering at its biological maximum so it is going to be very interesting to see which animals were visiting this year and what is going to happen next year.
Not all southern right whales come to our coastline every year and lots of questions remain as to where they spend their time. We think that there are about 5000-6000 animals in our population (and 15000 across the whole southern hemisphere) but they still have a long way to go for the population to recover properly because we estimate that there were over 70000 southern right whales globally before whaling started in earnest in the late 1700s!
This research is carried out under a permit from the Department of Environmental Affairs and under specific Marine Protected Area permits from conservation authorities.