Ursula Tscherter, Director of the Ocean Research and Education Society (ORES), tells us about her long-term research on minke whales off the east coast of Canada.
One has to close the eyes to imagine their fascinating hunting behaviours. Over and over again the dark body of Loca, the crazy minke whale, powerfully breaks the surface, her head each time facing a different direction. Although she arches her back strongly she is not going to dive; she rather moves fast below the surface and thus below the targeted prey. With each surfacing she moves closer towards the centre where the final feeding strike is going to take place. During some surfacings she raises her head obliquely far into the air and just after reaching the summit, she smashes it forcefully back onto the surface. The big splash of water, power waves and air bubbles created are believed to confuse the schooling fish which, within lightning speed, move close together to protect themselves from the predator they believe is going after one fish at a time. This reaction however is the worst to do when dealing with a minke whale which finally lunges into the dense prey with its mouth wide agape.
Long-term studies reveal their highly fascinating and complex lives.
The protected waters of the Saguenay - St. Lawrence Marine Park in Eastern Canada, some 800 km from the open Atlantic and 200 km East of Quebec City, is a main summer feeding ground where minke, humpback, finback and blue whales aggregate during the summer months. Here, strong tidal currents concentrate the prey along the steep slopes of the deep Laurentian Channel. In areas of upwellings krill and capelin fish concentrate near the surface where they become easier prey for the air breathing whales as they can feed and breathe at the same time.
Since more than twenty years, the Swiss-Canadian Foundation ORES dedicates its non-invasive research to the North Atlantic minke whale (Balaenoptera acutorostrata) known to be a rather difficult species to study. Thus not much is known about their lives despite their cosmopolitan distribution. The St. Lawrence Estuary however is not only a paradise for whales but also for researchers studying minke whales. During daily surveys up to thirty, sometimes even fifty individuals are identified often concentrating at certain hotspots. Many individuals have been seen every year since the early Nineties. Many of them visit the estuary thirty and more times during a summer. Others however have only been seen a few times every few years. Others only once.
Natural markings such as scars and spots on the skin but mainly nicks, dents and cuts along the dorsal fin edge allow ORES researchers to identify more than 90% of animals present at any time either by photographs or even visually in the field. The Dorsal Edge Mark (DEM) categorisation system developed by ORES facilitates the matching procedures tremendously. Today ORES maintains the most comprehensive minke whale identification catalogue with more than 300 individuals; almost half of which visit the study area in any given summer. The extremely high identification rate allows specific research questions not feasible anywhere else in the world like extended and repetitive focal follows of the same animals over many years.
Among others ORES’ research objectives are the population dynamics, long-term temporal and spatial distribution, breathing and feeding ecology, and habitat use with a special focus on individually different behaviours and specialisations. Research results reveal an unexpected adaptability, creativity and diversity in behaviours to my knowledge not matched by any other baleen whale species. Individual animals even show significant preferences for specific environmental parameters in their feeding areas!
Focal samples on individuals document the extremely fascinating creativity and ongoing invention of novel feeding strategies and techniques. Today seven different feeding manoeuvres (oblique, vertical, lateral and dorsal-ventral lunges and arcs) and an increasing numbers of entrapment manoeuvres are applied in general or by certain individuals. During lateral manoeuvres minke whales show a 95% preference for the right side which is just as high as the right handedness among humans. This preference of side is believed to be an indication for the high development of a species. When feeding ventrally the genital slits visible often reveal the sex of the animals. By today we identified 50 females but only one male supporting the theory that minke whales segregate by sex in their feeding grounds.
Always good for a surprise
“When you think you have learned something about their lives wait a minute and they will change.” The quote from the late Ned Lynas, founder of ORES, is as true as ever. In 2000 a minke whale performed a manoeuvre never seen before during more than 20 years of field observations. At first, ORES researchers did not understand the manoeuvre and therefore named the performing animal Loca, the crazy whale. This head slap, described at the beginning of this article, was her invention to scare the fish into a tight ball prior to a feeding strike. Over time more and more individuals specializing in feeding in the Saguenay Fjord “copied” Loca’s trick and even invented and developed other manoeuvres to entrap the prey. Today up to a dozen individuals create complex compositions of different entrapment manoeuvres such as chin-up blows, lateral surfacings, rolls, fountain blows and underwater exhales eventually leading to a final feeding strike. Some well-known individuals have developed such distinct strategies that they can even be identified just by their feeding signature; the whale ‘Loca’ prefers head slaps, ‘Speedy’ is extremely fast and agile, and ‘El International’ surfaces continuously at the same spot while lying on her right side. Today the novel feeding behaviours not only continue to spread among the population but are further developed and fine tuned with amazing creativity.
Although aggregating in high numbers at certain times and places North Atlantic minke whales are rather solitary and independently living animals. However since 2000 certain individuals form groups of two and three. Since then the number of animals involved, the sighting frequency and duration of grouping behaviours increased steadily. Although pairs have so far never been seen feeding together at the surface they are believed to hunt cooperatively at depth. To which extend however is not known.
Exposed to threats
Prior to 1993 a boat propeller cut deep into the back of the minke whale Three Scars, later named after the huge scars the accident left on her back. In 2004 ORES saved her life when she was entangled in fishing gear. In 2008 she carried an open wound caused from fishing nets. Since I know her Three Scars managed three times to escape certain death. She is a lucky one. Because entangled minke whales usually die.
Due to their coastal distribution minke whales are highly exposed to environmental threats caused by human activities. Therefore extended, dedicated research and long-term studies of minke whales in their natural environment is much needed in order to gain profound knowledge about their lives and needs because long-term conservation measures are crucial today. For instance, we do not know where Loca & Co. spend their winters, where they give birth and nourish their calves and what threats they face during their migration to their Northern feeding grounds. By the time they arrive in the estuary calves are already weaned of and therefore have to develop their hunting behaviours themselves.