Whales are the largest krill predators in the UK Overseas territory of South Georgia, yet their impacts on krill stocks are poorly understood. Recently, whale surveys revealed high summer abundance and extended use of South Georgia waters into winter, coincident with the winter krill fishery. This DARWIN PLUS project measures how humpback whale foraging intensity varies across the feeding season in South Georgia, using UAV-based (drone) measurements of body condition and satellite-tracking of whale diving rates to measure season-specific krill consumption, and inform krill quota-setting for the Subarea 48.3 CCAMLR krill risk assessment.
The UAV pilots will collect calibrated UAV aerial images from humpback whales near Cumberland Bay, South Georgia. Small-boat surveys will also be conducted near Cumberland Bay, collecting whale sightings, photo-identifications and biopsy samples. Humpback whales will be instrumented with depth-recording satellite tags, to identify spatial habitat-use and how foraging depth and intensity varies across the feeding season.
This project will provide seasonal krill consumption estimates for humpbacks and generate satellite tracking-based winter habitat use models to describe whale distribution. Both datasets will be integrated into the CCAMLR Area 48.3 krill risk assessment and will provide baseline measurements of krill consumption in South Georgia waters by whales across seasons.
Funding: Darwin Plus, South Georgia Heritage Trust and Friends of South Georgia Island. Logistical support from the Government of South Georgia and the South Sandwich Islands.
Follow the progress of the project on X and Instagram.
HIGHLIGHTS SO FAR
The first Stakeholders meeting for the Hungry Humpbacks project was held on the 5th September 2023. You can find excerpts of this meeting here.
The second Stakeholders meeting was held on 11th October 2024, with updates from the three field seasons.
Abrolhos Bank fieldwork, Sept – Oct 2023
The first field leg of the project took place in Abrolhos Marine National Park, Brazil from 20 September to 17 October 2023, recording the body condition of humpback whales at the end of their breeding season before they migrate south towards their feeding grounds in South Georgia and the Scotia Arc.
During this field project, a total of 121 drone flights were carried out, and more than 200 aerial photographs were taken of individual humpback whales. In addition, 34 skin and blubber biopsy samples were collected to determine the sex and pregnancy status of some of the measured whales. The whales encountered included mothers with calves, sometimes accompanied by an escorting male, singing males, and competitive groups. The whales are now migrating towards their feeding grounds around South Georgia, where they will build up fat reserves for the next winter breeding season. Read the report here.
Estimating humpback whale ages, November 2023
During November/December 2023, BAS PhD student Henry Slesser visited the laboratory of project collaborator Dr Emma Carroll, to learn how to estimate the ages of the humpback whales that have been biopsy sampled at South Georgia since 2017. This cutting edge molecular approach is called “epigenetics“. The laboratory technique is still being optimised for humpback whales and we eagerly await the results of their work early in 2025.
South Georgia fieldwork, Dec 2023 – March 2024
The next stage of the project was fieldwork using drones to study whales from land at Cumberland Bay, South Georgia during December 2023-January 2024. This had not been tried before and the two man team worked hard to find good vantage points to overfly whales and overcome challenging weather conditions and difficult terrain (including many seals hiding in tussock!). You can read their report here.
Next, two months of boat-based surveys were conducted in South Georgia in February and March 2024, working on powerboats and staying close to Cumberland Bay and coastal waters. The six-person boat-based team arrived at KEP in mid-January with five scientists and one dedicated jet boat driver who had overwintered in previous seasons. Most whales were sighted in January and February before the breakup of iceberg D-30A to the north, which brought large tabular icebergs close to shore in the team’s survey area.
The team had a very busy season! Over 2,200 km of visual transect data were conducted, and 34 cetacean sightings were recorded during the field season. Drone images and identification photos were collected from humpback whales, southern right whales, Antarctic blue whales, fin whales, and Antarctic killer whales. Biopsy samples for genetic, hormone, and isotype analysis were collected from humpback whales, southern right whales, and an Antarctic blue whale. A particular highlight was February 12th, when the team observed a southern right whale mum and calf pair plus an Antarctic blue whale mum and calf pair within two miles of each other!
The main focus species for the season was humpback whales, but the swell conditions were too rough to attempt any satellite tagging when humpback whales were in the area. The team successfully tagged a southern right whale on 9th March (named “Disco” after Discovery House, where the team stayed at South Georgia). The tag transmitted until May 31st 2024, and Disco’s movements can be seen here.
The report of the 2024 South Georgia field season can be read here.
Cabo Frio fieldwork, June-July 2024
The third leg of the fieldwork took place offshore of Cabo Frio, Brazil from 4th June to 7th July 2024, recording the body condition of humpback whales at the start of their breeding season as they arrive in Brazil from their feeding grounds in South Georgia and the Scotia Arc. During fourteen days in the field, humpbacks were observed every day, as well as killer whales, bottlenose dolphins and a southern right whale.
A total of 69 drone flights were conducted and 98 individual humpback whales were measured. In addition, 20 skin and blubber biopsy samples were collected to determine the sex and pregnancy status of some of the measured whales. Humpback whales were mostly encountered in groups of 2 to 6 individuals. The majority (86%) of measured whales were adults, and 14% were potential juveniles. No mother-calf pairs were seen, but one mother-yearling pair was encountered and measured. Read the report here.
Hormone analysis, August 2024
BAS PhD student Henry Slesser visited Dr Joanna Kershaw at her laboratory in Aberdeen University (she has since moved to the University of St Andrews). Jo has now analysed the progesterone and testosterone hormone profiles of all South Georgia humpback whales collected by the project and we will be circulating her findings soon.
South Georgia fieldwork II, Jan 2025 – April 2025
This season, a smaller team of researchers are back at King Edward Point, doing small boat surveys and looking for humpback whales to get UAV images of body condition, track animals via satellite tags and collecting biopsy samples and photo ID. Weather conditions have been mixed but the team have encountered some good sized groups of humpback whales already and collected a number of UAV images, biopsy samples and photo ID. They have also seen Antarctic blue and southern right whales. Hoping to track some animals before the season is out! More news soon as it comes in.. check out updates on Instagram at @wildwaterwhales
Whales are the largest krill-predators at South Georgia, yet their impacts on krill stocks are poorly understood. Recently, BAS whale surveys revealed high summer abundance and extended use of South Georgia waters into winter, coincident with the Antarctic krill fishery.
This project aims to measure how whale foraging intensity varies across the feeding season in South Georgia, using UAV-based measurements of body condition and satellite-tracking of diving rates to measure season-specific krill consumption.
The project will be implemented by measuring humpback demography (age, sex, pregnancy status and size) and foraging rates at South Georgia from summer to winter, using UAV overhead images of whales to measure their body condition and size across the feeding season, and using satellite tags to measure whale diving rates throughout the feeding season. Whale body condition will also be investigated on their Brazil winter breeding grounds either side of the feeding season, on migration to South Georgia from Abrolhos Bank, and on their northbound migration after the feeding season at Cabo Frio.
Body condition variation and dive rates will be used to estimate rates of krill consumption across the feeding season, providing season-specific krill consumption estimates for humpbacks to the CCAMLR krill risk assessment. Satellite tracks will also be used to produce winter habitat use models to describe winter whale distribution. Both datasets will be integrated into the Area 48.3 Krill Risk Assessment and will provide the first baseline measurements of krill consumption in SG waters by whales, across seasons.
Project progress reports to Darwin Plus can be found here.
PROJECT TEAM
Principal Investigator Dr Jen Jackson, British Antarctic Survey
Project Coordinator Stephanie Martin, British Antarctic Survey
UAV fieldwork and analysis
Dr Fredrik Christiansen, Aarhus University, Denmark
UAV analysis of body condition. Conducted field surveys in Abrolhos Bank, Brazil (2023) and South Georgia (Feb-March 2024)
Nicolas Lewin, Instituto de Conservación de Ballenas, Argentina. Conducted field surveys in South Georgia (Dec 2023-Jan 2024)
Maria Glarou, PhD researcher, University of Iceland. Conducted field surveys off Cabo Frio, Brazil (June-July 2024)
Penny Clarke, PhD researcher, British Antarctic Survey. Conducted field surveys in South Georgia (Dec 2023-Jan 2024).
Habitat use patterns and dive rates
Dr Amy Kennedy, University of Washington, USA
Satellite tracking of humpback and southern right whales at South Georgia, Led field surveys in South Georgia (Feb-March 2023)
Dr Alexandre Zerbini, Marine Mammal Laboratory, NOAA, USA University of Washington, Instituto Aqualie, Marecotel. Advice on satellite tracking and analysis.
Professsor Ari Friedlaender, University of California at Santa Cruz. Advice on habitat use and dive rates.
Humpback whale demography and body condition in Brazil
Dr Eduardo Camargo, Executive Director Instituto Baleia Jubarte. Lead on fieldwork off Abrolhos Bank in 2023.
Professor Rodrigo Tardin, Federal University of Rio de Janeiero. Lead on fieldwork off Cabo Frio in 2024.
Pregnancy and age analysis
Dr Joanna Kershaw, University of St Andrews, Scotland. Conducted biopsy sampling in South Georgia (Feb-March 2024). Analysing pregnancy and testosterone condition of whales during feeding season.
Henry Slesser, PhD researcher, British Antarctic Survey. Genetic profiling of individual humpback whales and epigenetic analysis of whale age.
Dr Emma Carroll, University of Auckland, New Zealand. Epigenetic analysis of whale age, advisor on genetic analysis.
Krill risk assessment at South Georgia
Sue Gregory, Senior Marine and Fisheries Manager, Government of South Georgia and the South Sandwich Islands. Advice on South Georgia fieldwork and krill risk assesment.
Dr Vicky Warwick Evans, British Antarctic Survey. Incorporating whale habitat use into Area 48.3 krill risk assessment.
Professor Martin Collins, British Antarctic Survey. UK Head of Delegation to CCAMLR. Advice on South Georgia marine ecosystem and delivery of results for krill risk assessment.
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