In association with the WDCS Species Guide every month from now on we’ll be bringing you a “species of the month” where we’ll take a closer look at the individual species, discuss in more detail the threats facing them and also hear from scientists and researchers who are in the field undertaking studies on the species we’re focusing on!
And April = Minke Madness!
Until recently all minke whales were considered to be one species, however science now recognises 2 distinct species, the Antarctic minke whale, which as its name suggests is found in the Antarctic, and the common minke whale, where currently 3 sub-species are recognised; (1) B. a. acutorostrata, found in the North Atlantic, (2) B. a. scammoni, found in the North Pacific, and (3) An as yet unnamed dwarf minke whale occurring mostly in the southern hemisphere. The smallest of the baleen whales, the common minke whale is widely distributed and although it is often found in offshore areas it tends to prefer more coastal and inshore waters, favouring continental shelves.
And so …. April is now officially dedicated to the common minke whale, otherwise known as Balaenoptera acutorostrata. I appreciate that although we’ve dedicated the month of April to this species, it may not have escaped your notice that we’re rapidly approaching the middle of the month … and this is the first posting for this species!! There was and is a very good reason for this, having just embarked on our bi-annual minke whale (and other cetacean) survey off the West coast of Scotland it was considered an appropriate time to launch this new feature … albeit 12 days late!! Our fieldwork coincides with the bi-annual NATO “Joint Warrior” exercise that takes place off the west coast of Scotland. The Exercise (the largest of its kind in Europe and occurring here twice a year) is taking place in April this year rather than May and this might be a good thing for our seasonal minkes, as it is the very beginning of the minke season and numbers are anticipated to be low (we await our first sighting with anticipation!).
As I post throughout the remainder of April, hopefully I can bring you up to the minute information on the common minke whale in this part of the world … and how they’re faring during this particular exercise!
So let us begin here at home in the UK …
Minke whale sightings are frequent and widespread from May to October in UK waters. The general pattern appears to be of an increased use of coastal areas as the season progresses, peaking July to September when large feeding aggregations can be observed in coastal waters. Outside of these months sightings are substantially fewer and very little is known about their winter distribution. Some individuals may remain close to Britain and Ireland but for the majority, it is unclear if they undergo a latitudinal migration or simply move further offshore for the winter months. Recently, minke whale vocalisations have been recorded in deeper waters of the North-east Atlantic, off the west coast of the UK, during these winter months. In some locations around the UK, photo ID studies have found individuals to be resident seasonally, or possibly even year round. But in the main … we know very little about where they go when they’re not hanging around off our shores.
?Everyone always wants to know “how many” of a particular species there are and when it comes to minke whales, this is no different and possibly more pertinent due to the fact that they are the staple of whalers around the world, specifically Norway and Iceland. Surveys in 1994 produced an estimate of 8,445 for minke whales in the North Sea whilst a similar survey in 2005 resulted in an estimate of 10,541 for the same area but this difference was not scientifically significant. Another offshore cetacean survey in 2007 produced an estimated abundance of 6,765 for minke whales, with sightings restricted to the northern blocks of the survey area, in British and Irish offshore waters. So as you can see …. Putting a figure on how many minkes there are can be difficult!
Scotland has the highest densities of minke whales in the UK and the west coast of Scotland is well-known for its populations of minke whales which migrate to the area in the summer months to feed in the rich and productive waters. Sandeels, herring and sprat have been noted as principal prey items of minke whales in British waters but other fish species, such as mackerel, cod and capelin, are also eaten. Minke whale distribution and abundance during the summer feeding season therefore will ultimately depend on the distribution and abundance of their prey. Whilst seabird and harbour porpoise declines have been linked to sandeel declines in Scottish waters, it has not been possible to make this link for minke whales. However as a primary prey source, it is likely that reductions in prey species, such as sand eels, would have a negative impact on minke whales in Scottish waters. In terms of other threats, the main known issues for minke whales in our waters are fisheries interactions, prey depletion and noise pollution. The Scottish Government is currently conducting an investigation into the extent of minke whale entanglements in fishing and / or mooring lines.
Naval sonar, more commonly linked to mass strandings events of deep diving whales, has also been associated with minke whale strandings in the Bahamas and in North Carolina. On the west coast of US, close to Seattle, similar rapid fleeing behaviour has been observed from killer whales and dolphins in response to sonar. Decreases in sightings of minke whales have already been reported off the west coast of Scotland during naval activities. It is not known how any disruption in the whales’ feeding behaviours will affect populations in the long term.
Whaling however obviously remains the greatest immediate threat to this species with Norway and Iceland both targeting them on an annual basis, in their thousands!! You’ll hear more about minke whales and their gruesome history with the whalers in a future minke blog as well as some updates from some common minke whale researchers around the world.
And so, that’s possibly enough to be getting on with for the moment, I’ll be back with more (from the field) soon …. !!