First evidence of bubble-net feeding and the formation of
‘super-groups’by the east Australian population of humpback
whales during their southward migration
| Kylie Owen
| David Donnelly
| Madeleine J. Brasier
Marine Predator Research Group,
Department of Biological Sciences, Macquarie
University, Sydney, New South Wales,
Institute for Marine and Antarctic Studies,
Ecology & Biodiversity Centre, University of
Tasmania, Tasmania, Australia
Department of Environmental Research and
Monitoring, Swedish Museum of Natural
History, Stockholm, Sweden
Killer Whales Australia, Box Hill South,
Vanessa Pirotta, Marine Predator Research
Group, Department of Biological Sciences,
Macquarie University, Sydney, NSW 2109,
Australian Research Council Linkage Grant,
Grant/Award Number: LP160100162
1. The recovery of overexploited populations is likely to reveal behaviours that may
have been present prior to harvest but are only now reappearing as the
population size increases. The east Australian humpback whale (Megaptera
novaeangliae) population (group V, stock E1) has recovered well from past
exploitation and is now estimated to be close to the pre-whaling population size.
2. Humpback whales were thought to follow a ‘feast and famine’model historically,
feeding intensively in high-latitude feeding grounds and then fasting while
migrating and in calving grounds; however, there is growing evidence that animals
may feed outside of known foraging grounds.
3. This short article reports on the first photographically documented evidence of
bubble-net feeding by humpback whales in Australian coastal waters (n=10
groups observed) and provides the first evidence of a second site in the southern
hemisphere for the formation of ‘super-groups’(n=6 super-groups at discrete
4. The formation of super-groups may be linked to changes in the type or density of
prey available, either along the migratory route or in the feeding grounds of the
previous summer. It is also possible that the increased population size following
recovery make large group sizes while feeding more common. These findings
strongly support evidence that feeding behaviour is not restricted to high-latitude
foraging grounds in the Southern Ocean, and that prey consumption prior to
leaving the coastal waters of Australia may be a significant component of the
migratory ecology of this population.
5. Understanding how environmental variation influences the extent to which
humpback whales depend on foraging opportunities along their migratory route,
and where feeding occurs, will help to predict how future changes in the ocean
will influence whale populations. This will also allow for more effective
management measures to reduce the impact of threats during this important
period of energy consumption.
Robert Harcourt also contributed to field work for this paper.
Received: 11 November 2020 Revised: 2 March 2021 Accepted: 5 April 2021
Aquatic Conserv: Mar Freshw Ecosyst. 2021;1–8. wileyonlinelibrary.com/journal/aqc © 2021 John Wiley & Sons, Ltd. 1
Australia, bubble-net feeding, foraging effort, humpback whale, migration, super-group
Most rorqual whale species (Balaenopteridae) were severely
reduced as a result of industrial whaling, but many populations are
now recovering well with some approaching pre-whaling
abundance. The east Australian population of humpback whales
(Megaptera novaeangliae; group V, stock E1) was estimated to have
numbered around 30,000 animals prior to industrial whaling, but
was then reduced to a few hundred by the 1960s (Noad, Kniest &
Dunlop, 2019). Since whaling ceased, and protections were put in
place, the population had recovered to an estimated 24,545
(95% CI 21,631–27,851) whales in 2015 (Noad, Kniest &
Dunlop, 2019). The recovery of populations to pre-exploitation
numbers allows behaviours not seen when populations were under
stress to re-emerge, and, given the heightened interest in wildlife
behaviour, possibly even be seen for the first time (Jackson
et al., 2020).
Many rorqual whale species are assumed to be capital breeders
that acquire energy resources when conditions are favourable, before
foregoing feeding and relying on energy reserves for reproduction
(Jönsson, 1997; Stephens et al., 2009). This assumption is based on
the empty stomachs of harvested northward-migrating whales and
few sightings of feeding behaviour on the migratory route and in
calving grounds. Traditionally, it was assumed that the east Australian
humpback whale population feeds predominantly over the Austral
summer in high-latitude feeding grounds within the Southern Ocean
(Chittleborough, 1965). However, increasingly, there is evidence of
this population feeding during the migration, especially during the
spring migration as they return to the Southern Ocean feeding
grounds (Stamation et al., 2007; Owen et al., 2015; Owen et al., 2017;
Andrews-Goff et al., 2018). This suggests that the ‘feast and famine’
migration model may not apply (Gales et al., 2009).
Humpback whales in the east Australian population have been
documented to feed along the migratory route as far back as old
whaling records (Lockyer, 1981). As the population has grown after
the cessation of whaling (Noad, Kniest & Dunlop, 2019; Pirotta
et al., 2020), accounts in the scientific literature of feeding behaviour
along the east coast of Australia have also increased (Paterson, 1987;
Gill, Evans & Wapstra, 1998; Stockin & Burgess, 2005; Stamation
et al., 2007; Owen et al., 2015; Owen et al., 2016). Some individual
whales have been shown to remain in productive feeding areas for up
to 10 days, taking advantage of the presence of krill (Owen
et al., 2015; Owen et al., 2016). Recent empirically based calculations
suggest that humpback whales may consume prey at such high rates
during migration that they could initiate a reversal in the depletion of
energy stores imposed by migration and could even rebuild a
component of their energy supplies before they reach their feeding
grounds (Owen et al., 2017). However, it is yet to be determined
whether this migratory feeding is opportunistic, in response to an
abundance of prey availability, or an essential aspect of their
migratory ecology and annual energy budget (Owen et al., 2017).
Humpback whales feed using a process called lunge feeding.
Humpbacks have a range of morphological adaptations, such as a
non-fused and outward rotating lower jaw, ventral pleating that
expands the volume of the buccal cavity, and baleen plates to filter
out prey items (Jurasz & Jurasz, 1979; Orton & Brodie, 1987;
Shadwick, Potvin & Goldbogen, 2019). Lunge feeding involves a
whale swimming at speed towards a patch of prey and engulfing large
volumes of prey-laden water. As lunge feeding results in high levels of
drag, it is an energetically expensive feeding behaviour (Goldbogen
et al., 2012). Therefore, it is only efficient when targeting dense
patches of prey.
Humpback whales have developed specialized behaviours that
increase the efficiency of lunge feeding by aggregating prey prior to
lunge feeding in the prey patch. For example, flick feeding and
lob-tailing involve the rapid movement of the flukes to create noise
and bubbles in the water column that entrap and stun prey (Jurasz &
Jurasz, 1979; Hain et al., 1982; Weinrich et al., 1992). Whales can also
blow bubbles from their blowhole to entrap prey. In the northern
hemisphere and in Antarctica humpback whales use bubble-net
feeding, where whales swim in a circle, at depth, expelling air
underwater in such a manner as to create a ring of bubbles around
their prey, after which they lunge towards the surface inside the ring
of bubbles (Ingebrigtsen, 1929; Jurasz & Jurasz, 1979; Wiley
et al., 2011). In some cases this behaviour also involves multiple
animals lunging into the same bubble net, in what appears to be
cooperative behaviour (Parks et al., 2014). Bubble-netting has been
well documented in the northern hemisphere in Alaska (Jurasz &
Jurasz, 1979) and Canada (Hain et al., 1982), as well as on the east
coast of the USA (Wiley et al., 2011). In the southern hemisphere, this
behaviour is also observed on the Antarctic Peninsula (Herr
et al., 2016). To date, the feeding behaviour of humpback whales off
east Australia has been described as skimming, surface lunge feeding,
or lunging at depth (Stamation et al., 2007; Owen et al., 2015; Owen
et al., 2016; Owen et al., 2017). In addition, the formation of bubble
curtains and clouds were observed off Eden, New South Wales, in
2011 (K. Owen 2020, unpublished data), and off Bermagui, New
South Wales in 2015, 2016, and 2017 (R. Harcourt 2021, unpublished
data). Bubble curtains and clouds are also used by humpback whales
to aggregate prey prior to lunge feeding (Friedlaender et al., 2009;
Hazen et al., 2009). However, to the best of our knowledge, bubble-
netting behaviour has never been observed off the east coast of
In 2020, scientists, commercial whale-watching operators, and
recreational drone pilots captured feeding behaviours and mass
feeding aggregations along the coast of south-east Australia. In this
paper, we report on: (i) the first photographically documented
evidence of bubble-net feeding by humpback whales in Australian
2PIROTTA ET AL.
coastal waters; and (ii) evidence of a second southern hemisphere
‘super-group’location along a migratory route, previously only
documented in the waters of South Africa (Findlay et al., 2017).
Over the months of September and October 2020, a total of
10 observations of bubble-netting behaviour and six observations
of super-groups occurred over 43 days across two states (New
South Wales (NSW) and Tasmania (TAS); Figure 1; Table 1).
Observations of super-groups of humpback whales feeding began in
September 2020, between Narooma and Eden, NSW, Australia. This
is the same location where both Stamation et al. (2007) and Owen
et al. (2015; 2016; 2017) had previously documented feeding during
the southward migration of humpback whales. Anecdotal evidence
from the crew on whale-watching vessels suggests that the
numbers of whales seen off south-eastern Australia in 2020 began
increasing to surprising densities from 7 September 2020.
Super-group sizes ranged between 20 and 90 whales (n=6 groups)
On 14 September 2020, a drone (flown under permitted state
rules, New South Wales Government, 2020) captured a super-group of
humpback whales feeding off Bournda (36.8314S, 149.9003E), NSW
(Figure 2). Drone footage shows tightly grouped humpback whales
feeding both at shallow depths and at the surface. The authors
independently counted from the same stills/video and estimated a
mean of 33 ± 5 animals, within five body lengths of each other, within
the single frame. This is higher than the definition of a super-group
(20 or more whales within five body-lengths of their nearest
neighbour; Findlay et al., 2017) and is a larger group than has
previously been documented feeding in this region (with a maximum
group size of 12; Owen et al., 2015). The typical group size of
migrating humpback whales in the east Australian population is two,
and this has remained consistent even as the population has grown
(Noad, Kniest & Dunlop, 2019). This footage was estimated (by the
drone pilot) to capture only a quarter of the total number of humpback
whales in the area at the time. In at least two independent cases,
evidence of bubble-netting behaviour can be seen (Figure 2; Table 1).
On the same day, further south off Eden, NSW (37.0667S,
149.9000E), bubble-net feeding was also observed by whale-watching
operators, with photographs clearly showing the circular formation of
the bubbles, with the two whales emerging at the surface, mouth
agape, in the middle of the bubble net (Figure 3). The following day,
drone footage and boat surveys by scientists recorded super-groups
and bubble-net feeding off Bermagui, NSW (36250S, 150040E).
Bubble-net feeding behaviour was also documented on 17 September
2020 between these locations, with at least two individuals observed
by whale-watching operators apparently feeding in a coordinated
manner. The prey species targeted during these events remains
unknown; however, observations from reliable observers suggest
that both schooling fishes and krill were targeted by the whales.
Other feeding behaviours more typical of this population, such as
surface lunge feeding, were also observed along the coast at this time.
In 2020, humpback whales were observed to feed over a wide
latitudinal range along the east coast of Australia. Feeding behaviour
was observed off Sydney, NSW, on 11 September 2020 (33.8980S,
151.2680E), 200 km further north of Eden. Feeding behaviour was
also observed further south off Victoria, including Phillip Island
(38.4899S, 145.2038E), Portland (38.3609S, 141.6041E), and
Wilsons Promontory (39.0849S, 146.4588E). Feeding has been
observed in this area over the last 3 years by whale-watching
FIGURE 1 Locations of humpback
whale (Megaptera novaeangliae) bubble-
netting behaviour (B) and super-group
(SG) occurrences in 2020 off New South
Wales (NSW) and Tasmania (TAS),
Australia. Humpback whales were also
observed feeding off Victoria (VIC);
however, no bubble-netting behaviour or
super-groups were documented
PIROTTA ET AL.3
TABLE 1 Summary of bubble-net feeding events by east Australian humpback whales (Megaptera novaeangliae) observed off south-eastern Australia during the 2020 southward migration
Date Location No. of whales Prey targeted Feeding behaviour/s Super-group Method of observation
14 Sep 2020 Bournda, NSW Approx. 40–60 Unknown Bubble-net and surface lunge feeding Yes Drone, incidental sighting
14 Sep 2020 Eden, NSW Unknown Unknown Bubble-net and surface lunge feeding Unknown Whale-watching vessel,
15 Sep 2020 Bermagui, NSW 60+Unknown Bubble-net and surface lunge feeding Yes Drone by scientists on a
dedicated research vessel
17 Sep 2020 The Pinnacles, NSW Unknown Unknown Bubble-net and surface lunge feeding Unknown Whale-watching vessel,
22 Sep 2020 Narooma/Montague
20+Unknown Bubble-net and surface lunge feeding Yes Scientists on a dedicated
23 Sep 2020 Wallaga Lakes, NSW 60+Unknown Bubble-net and surface lunge feeding Yes Scientists on a dedicated
24 Sep 2020 Cuttagee, NSW 90+Unknown Bubble-net and surface lung feeding Yes Scientists on a dedicated
17 Oct 2020 South-East Tasmania 25+Unknown Bubble-net feeding No Drone and whale-watching
vessel, incidental sighting
19 Oct 2020 Fortescue Bay, TAS Approx. 50 (one bubble-netting) Krill Bubble-net feeding, echelon lunge feeding Yes Drone and whale-watching
vessel, incidental sighting
26 Oct 2020 Waterfall Bay, TAS Three within the bay, 20 in the
region, one bubble-netting
Krill Bubble-net feeding No Whale-watching vessel,
Note: A super-group was defined as 20 or more whales within five body lengths of their nearest neighbour (Findlay et al., 2017).
4PIROTTA ET AL.
operators. Feeding was also observed off Tasmania approximately
1 month later, on 17, 18, and 26 October 2020. Further events of
bubble-netting behaviour and super-groups were once again
observed (Figure 3; Table 1). This demonstrates that over a 2-month
period, feeding behaviour by this population, including the
formation of super-groups, occurred over approximately 1,000 km of
To our knowledge, this is the first time that bubble-net feeding has
been documented in the peer-reviewed literature for humpback
whales in the southern hemisphere outside of Antarctic waters, and,
importantly, this was observed across a widespread area off south-
east Australia. This is also the largest known group size of feeding
humpback whales ever recorded in Australian coastal waters. Prior to
this, the largest documented group size of feeding animals was
12 (Owen et al., 2015). This population is thought to feed
predominantly on Antarctic krill (Euphausia superba; Groß et al., 2020;
Harrison et al., 2020) in Antarctic waters (Franklin et al., 2012;
Constantine et al., 2014; Harrison et al., 2020). However, these
observations provide further evidence that extensive feeding occurs
prior to leaving the coastal waters of Australia.
These observations point to the plasticity of humpback whale
behaviour and their need to supplement their energy intake during
migration (Eisenmann et al., 2016; Owen et al., 2016; Andrews-Goff
FIGURE 2 Super-groups of east Australian humpback whales
(Megaptera novaeangliae) off the New South Wales coast, Australia.
Evidence of an estimated mean of 33 ± 5 animals (counted
independently by the authors) of humpback whales feeding below
and at the surface in two separate stills from the video (a and b). The
formation of a bubble column is visible at the lower left-hand corner
of (b). Images: Brett Dixon
FIGURE 3 Evidence of bubble-net feeding
by the east Australian population of humpback
whales (Megaptera novaeangliae) during the
southward migration from four different
locations off Australia’s south-east coast in 2020.
(a) An individual with expanded pleats feeding in
a bubble net in Eden, New South Wales (NSW),
Australia (photo: Cat Balou Cruises). (b) Two
individuals lunging in the same bubble net off
Eden (photo: Cat Balou Cruises). (c) Drone
footage of a bubble net visible at the bottom of
the image with a group of whales in the distance
off Bournda, NSW, Australia (photo: Brett Dixon).
(d) Bubble-net feeding documented at Haycock
Point (north of Eden), NSW (photo: Merimbula
Marina). (e) Evidence of bubble-net feeding from
drone footage, Tasmania, Australia (photo: Wild
Ocean Tasmania). (f) Humpback whale with
expanded throat pleats rising to the surface in a
bubble net off Tasmania, Australia (photo: Wild
PIROTTA ET AL.5
et al., 2018). Supplemental feeding has also been observed in other
southern hemisphere populations, both off South Africa (Barendse
et al., 2010; Findlay et al., 2017) and South America (Alves
et al., 2009; Acevedo et al., 2013). Further evidence that foraging
behaviour in humpback whales continues while migrating south, after
leaving Eden, in the waters off eastern Tasmania exists from satellite
tracking data (Andrews-Goff et al., 2018). These observations also
align with evidence of feeding outside of Antarctic waters from stable
isotope analysis of baleen plates (Stephens et al., 2009; Eisenmann
et al., 2016).
Super-groups of humpback whales feeding in east Australian
coastal waters have never been documented before. It is possible that
an abundance of prey and other environmental conditions (e.g. water
temperature and nutrients) may have created high ocean productivity
suitable for such events; however, detailed information on how prey
availability varied in this year relative to others is unavailable.
Individuals may have been able to obtain sufficient energy from this
feeding that the time investment is worthwhile, despite the delay in
migration to the feeding grounds (Owen et al., 2017). Variability
in prey type and abundance, both in high-latitude feeding grounds
and along the migratory route, may influence interannual differences
in whale numbers and the evolution or spread of new feeding
behaviours in these stopover areas (Owen et al., 2017). For example,
while feeding off Eden, whales have been observed to form larger
group sizes and feed at a higher rate when targeting krill at the
surface than fish at depth (Owen et al., 2015; Owen et al., 2016). It is
also possible that changes in the availability of krill in the Southern
Ocean feeding grounds in the previous summer influence the extent
to which whales rely on opportunities to feed along the migratory
route, with fatty acid profiles of humpback whales in this population
recently linked to changes in the Southern Annular Mode (Groß
et al., 2020).
It is unknown whether the use of bubble-net feeding by the east
Australian population has evolved independently or through the
cultural transmission of feeding behaviours. The use of bubble
columns and clouds has been observed to be used by the east
Australian population over the last decade, and these features are also
regularly used by other populations (such as the Western North
Atlantic humpback population) that also bubble-net feed (Hain
et al., 1982; Friedlaender et al., 2009; Wiley et al., 2011). It is possible
that learning to close the net is the next step in the independent
development of this behaviour. However, as documented with other
humpback whale feeding behaviours, such as lobtailing (Allen
et al., 2013) and the production of song (Garland et al., 2017),
humpback whales are capable of cultural transmission. Although there
are seven geographically identified humpback whale breeding stocks
in the southern hemisphere, the extent to which these populations
mix remains unclear (Amaral et al., 2016). There is some genetic (Steel
et al., 2018) and satellite tag evidence (Riekkola et al., 2018) to
suggest that at least some individuals in the southern hemisphere may
move between different populations. This may expose the east
Australian population to novel feeding behaviours. Humpback whales
on the Antarctic Peninsula use bubble-net feeding behaviour similar
to that observed in this study to target krill (Herr et al., 2016). It is
therefore possible that bubble-net feeding has been introduced to
this population through the emigration of individuals from
neighbouring populations. The appearance of bubble-net feeding in
this population may therefore be further support for the movement of
individuals between populations in the southern hemisphere.
The use of citizen science data has helped to document bubble-
net behaviour and the formation of super-groups during the
southward migration of the east Australian humpback whale. It also
enabled the detection of this behaviour over a broad area,
highlighting the significance of this behaviour at a population level
that would not have been possible through observations at a single
location. These opportunistic data, verified independently through
scientific assessment, highlight the role of citizen science in marine
mammal research (Pirotta et al., 2020), particularly where unexpected
behaviours may emerge as populations recover. This study also
demonstrates the value of citizen scientists and the scientific
community working collaboratively. These findings derive from both
land- and sea-based observations, which would not otherwise
have taken place in 2020 because of the COVID-19 global pandemic.
Working closely with scientists, citizen scientists provide an
opportunity to further disseminate the findings of this study.
The novel emergence of bubble-net behaviour and the formation
of super-groups observed in Australian coastal waters may have
conservation implications. First, observations of super-groups may
become more common off the east coast of Australia, as this
population of humpback whales continues to show adaptive
resilience. More whales may mean more opportunity to document
novel behaviours because of the higher number of individuals
transiting the Australian east coast. The possible cultural transmission
of behaviours may also indicate links and the potential presence of
individuals from other southern hemisphere populations, highlighting
the need for appropriate widespread population protections. As
environmental conditions change, the importance of annual feeding
during the southward migration may become more apparent. In this
region the East Australian Current (EAC) is strengthening, specifically
the EAC extension, which extends south along New South Wales into
Tasmanian waters (Ramos et al., 2018; Philips et al., 2020). As a result,
warmer waters occur further south, bringing a range shift of some
marine species, including some in their planktonic larval stages, which
may influence local productivity (Ramos et al., 2018). The enhanced
annual variability in local conditions has already been shown to impact
the foraging success of predators that feed on the same prey as these
whales, such as little penguins (Eudyptula minor) (Carroll et al., 2016),
suggesting that over time there may be large fluctuations in the
availability of prey, which may adversely affect whales if they become
reliant on this food source.
The continued growth of the east Australian humpback whale
population and the extension of southward migration feeding areas
supports the need for a reassessment of the conservation listing of
this population and the recognition of feeding locations federally.
Formal identification of feeding areas will help to ensure
additional protection of humpback whales in Australian waters from
6PIROTTA ET AL.
anthropogenic activities, such as tourism (e.g. whale watching),
commercial fisheries, and underwater seismic exploration. Further
research into the possible drivers of these occurrences will help to
better understand humpback whale ecology in Australian waters and
the importance of these feeding events to this population.
We would like to thank ecotourism companies Cat Balou Cruises, Eden,
Merimbula Marina, Merimbula and Wild Ocean Tasmania, Eaglehawk
Neck, Tasmania for contributing bubble net feeding images.
Observations in 2020 from the Narooma/Bermagui region occurred
during a project funded by an Australian Research Council Linkage
Grant to Ian Jonsen, R.H. and colleagues (LP160100162). We would
also like to thank Brett Dixon and Jason Iggleden (DroneSharkApp) for
contributing drone footage of humpback whale feeding.
CONFLICT OF INTEREST
All authors declare that they have no conflicts of interest associated
with this work. All drone footage was collected following state
regulations (New South Wales Government, 2020).
Vanessa Pirotta https://orcid.org/0000-0003-0395-1859
Kylie Owen https://orcid.org/0000-0002-8986-482X
Madeleine J. Brasier https://orcid.org/0000-0003-2844-655X
Robert Harcourt https://orcid.org/0000-0003-4666-2934
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How to cite this article: Pirotta V, Owen K, Donnelly D,
Brasier MJ, Harcourt R. First evidence of bubble-net feeding
and the formation of ‘super-groups’by the east Australian
population of humpback whales during their southward
migration. Aquatic Conserv: Mar Freshw Ecosyst. 2021;1–8.
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