The project began in the early 1980's, when minke research around the San Juan Islands, Washington was started by Eleanor Dorsey. This was as a behavioural study based on the ability to recognize individuals. Once this was accomplished, individual specific behaviors could be identified and minimum population estimates could be made.

The success of this work led us to similar studies in the Monterey Bay area, California and Johnstone Strait, British Columbia. These different areas provided other populations for a comparative approach to study minke whales in areas with different predominant ecological processes. 

Photo identification catalogues

Using photographic techniques to recognize individual whales, catalogues were created for the 3 study areas.  Several features were used to identify these minke whales, such as notches in the dorsal fin, scars on the body, unusual fin shape and lateral body pigmentation. Some of the scars on the body of the whales are oval and white, thought to be caused by parasitic lampreys.  

So once a whale is identified, subsequent "recapture" of that individual during a later encounter sheds some light on the movements and distribution of that individual. Some of the individuals were seen multiple times over the course of a summer field season, and from year to year. This "faithfulness" to an area is called site-fidelity. 

These studies  revealed that only a few individuals were identified, less than about 60 overall, throughout the 3 study areas. There were no matches of individuals between areas, suggesting populations were separate, at least as feeding aggregations. Most field effort, and thus more individuals were identified around the San Juan Islands. A total of 30 individual minkes whales were catalogued over 11 years of study around the San Juan Islands.

Distribution of minke whales around the San Juan Islands

In the 1980's minke whales were found in three areas of concentration around the San Juan Islands. These three areas A, B and C are shown in the map below.

Site-fidelity makes sense for a predator looking for ephemeral, or patchy resources such as fish shoals. The whales get to know an area, and increase the chances of finding food by repeatedly searching areas where an individual has previously found food. 

However, by the 1990's 2 of these areas were abandoned, and whales were only found in the Strait of Juan de Fuca (Area C), despite continued search efforts in areas A and B. This coincided with a general decline of herring associated with disturbance of adjacent herring spawning grounds. Also, we noted an overall qualitative change in the number of sea birds.

In 2005, we found whales foraging in all 3 areas again, and the number of birds was also much higher than in recent years. To read more about this please go to Current Research. 

Exclusive adjoining ranges

Sixteen whales were identified whales in 1980. The distribution of these individuals were very interesting, and unexpected.  Each whale  favoured one of the areas, or " exclusive adjoining ranges." Each area was shared by up to at least seven minke whales, with only two instances of crossover between the areas in 70 sightings. Feeding was observed in all three areas, and the whales within each area appeared most of the time to be acting independently of one another. No calves were seen, and no overt acts of territorial defence were observed. This is the first known report in baleen whales of small-scale non-overlapping ranges. 

Feeding behavior

We also studied the feeding techniques of 23 individually identified minke whales in the inland waters of Washington State and reported that each whale tended to specialize in one of two feeding techniques, lunge feeding or bird-associated feeding.

Bird-associated feeding involved the whale exploiting schools of fish fry concentrated by birds. Alcids  including rhinocerous aucklets, murres and pigeon guillemots and other diving birds such as cormorants pursue fish from below.  Predatory fish such as salmon and dogfish sharks concentrate and drive prey to the surface. Gulls feed from the surface and mark the spot.  Minke whales are then seen surfacing at the site where the birds are feeding.

Lunge feeding is described as the whale actively concentrating the prey against the air/water interface with no birds involved and then lunging through the fish with its mouth open. This occurs in deep basin areas or at the edge of tide rips. 

Dead fish and scales were collected at the site of observed feeding. Juvenile Pacific herring were found where lunge feeding had taken place and juvenile Pacific herring and juvenile sandlance were found on separate occasions after bird-associated feeding had taken place. 

As mentioned above, individual whales tended to feed in specific areas and return to these areas throughout the season and from year to year. The techniques were specific to a certain site implying that the whales specialised on a technique depending on the area that they return to annually. This suggests that individuals know area-specific environmental conditions, and the spatial and temporal distribution of prey within that area. The areas where lunge feeding mainly occurred consisted of open basins bounded at one side by a shallow bay and by a steep slope at the other. The area where most bird-associated feeding occurs consisted of shallow banks bounded by deep water with direct oceanic influence through the Strait of Juan de Fuca. 

Minke whale feeding strategies depend upon variations in the distribution of prey in a complex and patchy environment. Bird-associated feeding occurs when the prey is concentrated and transitory in its occurrence usually along the edge of banks and upwelling areas. Whereas lunge feeding occurs when the prey is patchy but predictable in locality, i.e. spawning grounds of fish, and is abundant every year. Thus, it is suggested that topography, and the hydrographic influences that this creates, affects the distribution of fish fry or their planktonic prey and that this in turn determines the feeding techniques most appropriate to exploit the prey.  

Distribution in the Monterey Bay Area

Minke whales in this area had a different distribution pattern, likely dictated by the environment. The edge of the continental shelf was relatively close to shore, less than 15km in most places, and closer in others. Thus minke whales were relatively close to shore, often at the edge of kelp beds, where they fed on schools of juvenile rockfish (Sebastes spp).

Minke whales were initially thought to be quite numerous, based upon sightings. We identified only a few individuals in the area, but their movement patterns were what suggested the large population size. Sightings were made from shore. When we followed a minke whale, it moved alongshore, back and forth along the coast. Therefore, the large number of sightings were actually sightings of a few individuals moving back and forth in front of the sightings platform. Instead of saying “there’s one...there’s one…there’s one” over and over, they should have said “there’s Springsteen… there’s Springsteen again… there’s Springsteen again” over and over.  

The Minke Whale Project continues! 

The work in the San Juan Islands has continued and there have been a number of significant findings. To read more about this please go to Current Research.