Same minke whale, different identifiable markings
The minke whale (Balaenoptera acutorostrata) is one of the most abundant baleen whales in the world, and yet due to their shy nature and agile manoeuvres through the water they are difficult to research and thus very little is known about them. However, here in Faxaflói we encounter many and often our interactions are both close and sociable, allowing us to obtain interesting insights into their world.
The dorsal fin is the main feature we use to identify minke whales, as they have unique shapes, sizes, characteristic scars or notable nicks and notches. Of course, some individuals are not so easy to identify, if we can include them in our research at all. Younger individuals for instance often have what we call “clean” dorsal fins because they generally haven’t been exposed to scar-causing events. Unfortunately, most markings are the result of entanglements, ship strikes, attacks by conspecifics, predators such as sharks or orcas, or infestations of parasites and diseases. Therefore, besides allowing us to recognise the individuals, dorsal fins also tell a story of what an individual has gone through.
One of those individuals is a minke whale called Tap. Tap is a regular visitor to Faxaflói and has been one of the crew's favourites since the beginning. He/she (the sex of minke whales is difficult to determine without a glimpse of their underside) has often been the star of some amazing encounters, seen on at least 40 different tours from 2007 until 2019. Unfortunately, due to COVID we are behind on the research and still processing the most recent data.
Tap can be identified by the unique round notch at the lower part of the trailing end of the dorsal fin (check out the photo below).
Over the last few years our minke whale sightings have declined, a few reasons being due to the pandemic and the lockdown of our company, reduction of tours and thus encounters, the exponential increase in a more dominant species - humpback whales - entering the bay and competing with the minkes for food, causing minkes to feed in other locals, and also climate change causing a shift if their preferred prey species. All of the above cause a reduction of encounters with many of our regularly sighted ´celebrity´ minke whales. However, in July 2021 we were pleased to encounter Tap again. It took some time and a few marine biologists to confirm it was Tap as this year he looked different: a brand new large notch had appeared on the upper part of the trailing edge, sometime in the two years since we last photographed Tap, the minke whale. We cannot say for certain what caused it, but we are glad Tap survived the incident and is still visiting Faxaflói.
Tap’s journey can give you a bit of an insight into the complexity of the popular research method “photo-ID” (in a nutshell, photo-ID is the identification of individuals based on body markings, which are captured on photographs and matched with existing photos in a catalogue). Firstly, this story shows that it is crucial to pay attention to every single detail: even though an individual looks completely different than it did before, it can still be the same minke whale! In the case of Tap, we were able to recognise him/her because of the lower, round notch and by inspecting the slight variations in coloration along the body.
Tap is not the first whale we noticed to have changed its identifiable markings, Spider is another example and this time there was only one year between encounters. It's incredible to see how quickly their body can recover from the injuries they obtain.
Below you can see the difference in markings between 2013 and 2014 and that we were able to identify this individual as Spider by the long indentation on the body, possibly obtained by a lamprey or cookiecutter shark which attach themselves to whales and feed on the skin, and the notch taken out of the top part of the dorsal’s trailing edge. Of course we are not always lucky to have other markings to confirm these as individuals already identified, once again reiterating the difficulties of researching this species.
Conversely, some minke whales look almost identical to each other when they are in fact different individuals. For example look at the photos below of Tap and another minke whale called Hook – at first glance they look similar, but when you inspect closely Hook has a more rounded notch and the fin has a slightly different shape.
Although markings like Tap’s are very helpful for identification purposes, it is on the other hand sad to see them because they suggest the whale was probably exposed to a dangerous situation. Of course some scars are an inevitable part of nature, but many minke whales and other species do have markings that suggest an anthropogenic impact. To understand what caused these markings and how we can mitigate man-made threats to prevent future serious injuries, it is crucial to understand more about cetacean individuals and populations. Ironically, that is where the markings come in handy again, because they allow us to conduct photo-ID studies and advance our knowledge on what is happening to Iceland’s whales and dolphins and how we can protect individuals such as Tap.
-By Megan Whittaker and Eline van Aalderink