The common Minke Whale (Balaenoptera acutorostrata) is the smallest baleen whale in the North Pacific. Fully grown, it averages about 7.5 metres in length. It is greyish in colour with white flipper patches, has a small curved dorsal fin two-thirds of the way along its back, and does not often have a visible blow upon surfacing. The Minke Whale is known to feed on small schooling fish and invertebrates. It has 50 to 70 throat grooves on the underside of its body which can extend considerably when engulfing prey. Minke Whales are most often solitary, although they are sometimes encountered in pairs. Trios are uncommon. Minkes are not a highly surface active species, but do occasionally breach and exhibit curiousity towards vessels.
Off the coast of British Columbia, most Minke Whale sightings are recorded between May and October. More often than not, they are sighted in relatively shallow water (less than 200 metres in depth). Surveys along the west coast of North America suggest that minke whales are not particularly abundant in these waters. These low numbers of Minke Whales, combined with their small size, long dives, and elusive nature, make this species particularly difficult to study. For this reason, relatively little is known about the Minke Whales living in the Northeast Pacific. Studies of Minke Whales in both Washington and California have revealed some insight into their behaviour and distribution; however, much of what we know about this species' biology comes from research undertaken in other oceans on different populations of minkes. Some of this knowledge has unfortunately been derived through the use of lethal research methods.
Collisions with boats have been known to result in mortality for Minke Whales.
The parallel scars on this Minke Whale's back were caused by the propellor of a boat.
Natural threats can also lead to injury or mortality for Minke Whales; the scars seen here are from an encounter with Killer Whales.
In British Columbia, threats to minke whales include those from both anthropogenic and natural sources. Anthropogenic threats include ship strike and entanglement in fishing gear. Natural threats include those imposed by transient Killer Whales and possibly fluctuating prey resources. COSEWIC conducted a risk assessment on the population of Minke Whales in B.C. and concluded that the known risks to these whales are not severe enough to cause concern. It can be argued, however, that there is a considerable lack of data on the species.
Both ship strikes and entanglement in fishing gear are known to cause mortality to Minke Whales in the Pacific Ocean. It is thought that most incidents involving either threat go undetected or unreported and are likely to be fatal. Both surviving and stranded dead animals have been found with scars from such events on their bodies which can aid in determining the source of the wounds and/or the cause of death.
In the eastern North Pacific, Minke Whales were never targeted by commercial whaling due to their small size and lack of abundance. To this day, Minke Whales are not hunted in the eastern North Pacific; however, they are still hunted commercially in the western North Pacific. Movements of individual animals throughout the North Pacific are largely unknown so it is possible that Minke Whales seen in B.C. could be at risk from whaling if their migration routes, breeding grounds or alternate feeding areas are in waters west of 180 degrees longitude.
Pollution and underwater noise can also be considered potential threats to Minke Whales; however, it is difficult to evaluate the impacts of these threats.
Minke Whales have a small curved dorsal fin about 2/3 of the way along their backs.
A Minke Whale lunge feeding on small fish.
Minke Whales are not often active at the surface. Here, a rare view of one surfing behind a boat.
Photo identification is a method used for a number of studies on animal populations all over the world. Data derived through photo ID can be used to obtain insight into animal movements, population sizes, behaviour, threats, and habitat. Our dedicated field effort to collect photo ID data from Minke Whales in B.C. began in 2010; however, data from as far back as 1987 have been contributed to the study. Together, these data have shed light on Minke Whale movements within and between our study areas. These data have also helped reveal a minimum and maximum age of some known animals, as well as habitat preferences. Through our ongoing photo ID study of Minke Whales in B.C., we hope to gain further insight into their population structure, individual range and habitat use, and begin to answer questions regarding threats and behaviour.
Minke Whales in the eastern north Pacific Ocean are known to feed on various species of small schooling fish from spring through fall. Preferred feeding areas tend to not only contain sufficient prey but also usually have specific oceanic and geologic characteristics. In British Columbia and Washington several of these feeding areas are hundreds of kilometres apart. Through efforts in these areas we have been collecting identification photos as well as prey and scat samples from several Minke Whales to help determine patterns of residency as well as preferred prey species. These are important items to consider for effective management of both Minke Whale populations and their key prey species in these waters.
In 2012, we initiated a study aimed at recording vocalizations of individually known Minke Whales in waters off northern Vancouver Island. A total of 12 volunteers made 568 hours of shore-based Minke Whale observations over 56 days while a fixed hydrophone constantly recorded all sounds in the marine environment nearby. The Minke Whale vocalizations we recorded are the first known from the eastern North Pacific Ocean and provide valuable baseline data on the vocal repertoire of this species. This kind of information is important for consideration by governments and corporations when determining area specific biological diversity through acoustic surveys.
An identification photo of Minke Whale "Eclipse".
A Minke Whale at sunset.
A Minke Whale traveling at high speed. Minkes are one of the fastest cetaceans.