Southern right whale survey shows change in migration patterns and feeding
- Data shows that South African southern right whales have drastically changed their feeding locations in the past 20 years
- Researcher Dr. Els Vermeulen believes this is due to climate conditions in the Southern Ocean and "food availability issues"
- The Mammal Research Institute’s Whale Unit at the University of Pretoria conducted its 42nd annual aerial survey of southern right whales last week
- The photo-identification aerial survey is one of the longest uninterrupted datasets on any marine mammal worldwide
Southern right whales appear to be changing their movement along South Africa’s shores due to climate conditions in the Southern Ocean and fluctuations in food availability.
Research manager Dr. Els Vermeulen has been studying the trends observed by the Whale Unit at the University of Pretoria’s Mammal Research Institute.
The unit conducted its 42nd annual photo-identification aerial survey, flying between Nature’s Valley on the Garden Route and Muizenberg in Cape Town to count southern right whales in the coastal waters.
Dr. Vermeulen says the survey counted 191 females with calves, which is almost half of what is ideally expected. "In normal conditions, we could be expecting close to 400 females", she tells CapeTalk.
In another aerial survey between Hermanus and Witsand last month, researchers spotted 209 females with calves.
The researcher says southern right whales are changing their feeding locations and spending limited time along SA’s shores.
This is also impacting their body condition and the success of their calving and migration.
"Instead of giving birth every three years, a female is giving birth every four to five years", she adds.
The numbers are up from 2019 and 2020 so that is good news. However, the numbers are still quite a bit low compared to what we should expect in normal conditions.Dr Els Vermeulen, Research manager - Mammal Research Institute Whale Unit at University of Pretoria
We counted 191 but we're expecting that this was not the peak though.Dr Els Vermeulen, Research manager - Mammal Research Institute Whale Unit at University of Pretoria
I'm suspecting that whales are starting to leave already. Quite a few of the calves we saw were quite large already and getting ready for their migration start. So, the numbers are going to start decreasing now.Dr Els Vermeulen, Research manager - Mammal Research Institute Whale Unit at University of Pretoria
What we're seeing with our database is that there's a change in migration patterns and a change in calving interval.Dr Els Vermeulen, Research manager - Mammal Research Institute Whale Unit at University of Pretoria
We're looking at feeding conditions. Some of our research is confirming that the whales have gone skinnier in the past 20 years. So the body conditioned has decreased by about 20% since the late 80s. Feeding conditions we believe are being affected by climate change.Dr Els Vermeulen, Research manager - Mammal Research Institute Whale Unit at University of Pretoria