Porpoise-full Blog!
This, like my “You Otter Know” blog, is aimed at clearing up species confusion and offering some support to my fellow marine educators.
Yes, I am writing this for much needed educational porpoises. Sorry! I will attempt to restrain myself from further bad puns (but I am counting on you, the readers, to come up with some doozies).
Oh the number of times I have had the joy of an exchange like this:
Me: “Look, a porpoise!”
Response: “Ja, ja, een delfin!” or “Oui, oui, un dauphin” or “Ja, ja, een dolfijn” or “Yes, yes, a dolphin!”.
Me (armed with images like those below): “Nein – een schweinswal” / “Non – un marsouin” / “Nee – een bruinvis” / “Nope – it really is a porpoise!”
It is so understandable that there is significant confusion. The words dolphin and porpoise were, colloquially, used as if they were synonyms into at least the 1970s.
But, dolphins and porpoises are more distinct than lions and tigers. Lions and tigers are not only in the same family but in the same genus. Dolphins and porpoises are in different families, having diverged around 15 million years ago.
That’s no dolphin! It’s a Dall’s Porpoise. ©2015 Jackie Hildering.
The differences between porpoises and dolphins span from fin and head shape, to behaviour, vocals and average group size.
In many resources, the three distinctions that are most often provided are – the difference in the shape of the teeth, rostrum (snout) and dorsal fins. But really, the first two are not likely to help you in the field! When at sea, in addition to dorsal fin shape, group size and behaviour are probably going to be of use more use in discerning porpoises from dolphins.
In the table below, I provide a summary of the differences with great thanks to Uko Gorter for his illustrations. This information will likely be useful too in making clear how it is that Orca are dolphins – the biggest member of that cetacean family.
Off the coast of British Columbia, in addition to Orca, commonly there is only one species of dolphin (Pacific White-Sided Dolphins) and two species of porpoise (Harbour Porpoises and Dall’s Porpoises).
Dall’s Porpoises most often get misidentified as dolphins because they are larger than other porpoise species and because they are far less cryptic e.g. when going at full speed at the surface at ~55 km/hour, there is a very distinctive spray of water known as a “rooster tail” and, they do sometimes interact with boats – bow riding like dolphins do. Please note that I very consciously choose to use “cryptic” as a descriptor rather than the very anthropomorphic term “shy”. Harbour Porpoises can be difficult to detect, but I assure you, that this highly promiscuous species is anything but “shy”!
Yes, I used the term on porpoise!
Uh oh, I did it again! I almost made it to the end of the blog without another bad pun. 🙂
The genetic work of Carla Crossman on stranded porpoises found that, Dall’s and Harbour Porpoises: (1) hybridize more often than was realized; (2) many hybrid individuals do not look different i.e. they can not be discerned as hybrids on the basis of appearance; (3) crosses go both ways i.e. Harbour Porpoise males with Dall’s Porpoise females and Dall’s Porpoise males with Harbour Porpoise females; AND (4) they backcross = the hybrids are reproductively viable! For more information, see page 8 of Crossman et al here www.int-res.com/articles/esr2015/26/n026p001.pdf
Matched! We documented a hybrid Dall’s / Harbour Porpoise in virtually the same location as almost a year earlier (within around 3 nm / 5.5 km just outside Telegraph Cove). See the scar? It’s faded but it’s a match. This was possible due to Head Naturalist Alison Ogilvie of Stubbs Island Whale Watching Vancouver Island. Why is it a big deal? Porpoises are very difficult to discern as individuals whereby it is challenging to learn about everything from population size to site fidelity / seasonal movements, etc! The DNA research of Carla Crossman on stranded porpoises has proven that hybridization between these species is far more common than was thought. Most often the hybrid does not look different than one of the parents and only DNA testing reveals it has genes from the parent of the other species. BUT sometimes, like with this individual you can tell. We noted this hybrid feeding in a group of Dall’s Porpoises. It was as big as they were but you’ll note the colouration is very different i.e. grey instead of black and no white frosted dorsal. DNA has been going back and forth between the species for a long time = the female hybrids are fertile but this cannot be confirmed for the males.
More information aimed at discerning species below.
Discerning gender in adult Dall’s Porpoises.
For information on the hybridization of Dall’s and Harbour Porpoise see Carla Crossman’s research here.
For more on how to discern British Columbia’s cetacean species, please see here for information from the BC Cetacean Sightings Network.
Below – illustrations of additional porpoise species and known ranges.
Additonal Dolphin and Porpoise species (not found in BC waters). Illustrations by Uko Gorter.
Known ranges o f global porpoises by Uko Gorter.
Related TMD Blog: Cetacean Gender – Male or Female? How to Know?
The Marine Detective 
11 Responses to “Porpoise-full Blog!”
great info thanks Jackie!
Thanks, Jackie! This will come in VERY handy when I talk with people about porpoises, dolphins, fishes and mammals in general….
A very happy holiday and my warmest wishes for a great new year.
Abby
Jackie, getting this stuff straight is a really good idea… thanks so much for clearing this up! I’m still not sure how effective I could be discerning on-site but there are a few really awesome tips in your entry that can really make a difference! Thank you!…. so a Dall’s fin is different from a dolphin’s?!!! 😉
Ha! Thanks for that wink Sonix!
Thanks for the simple yet effective info….I took quite awhile to ID one lone Dall’s Porpoise we spotted in Bute Inlet and the pair of White Sided Dolphins near Shoal Bay. This was the extra bit that put it all together for me.
wow. now i get it. thanks for the clarification. very humbling to see an organism that has effectively lived and adapted to live in the water for 15 million years.
Value knowing the blog is of use. Thank you Jennifer!
Thanks for the info. I witnessed what look like play in a few young porpoises today, is this common? Also, individuals swimming inverted? Seen this on two different occasions, Arklow, Co Wicklow, Ireland. (Have photos… )
Hello AJ – I do not have expertise on the porpoises in Ireland but this sounds much more like dolphin behaviour. I have read that there is are Bottlenose Dolphins near Wicklow. https://www.rte.ie/news/2011/0930/306801-dolphins/.
Hi There, thanks for getting back to me… I’ve posted some photos today… https://ouchmybackhurts.wordpress.com/2018/09/02/sunday-serene-seaside-special/
I can send you a few more… of the little one swimming up side down as well. I think I have previously seen dolphins here but these seem more like porpoises having fun! 😉
Those are Harbour Porpoises alright! Having fun seems right too. 🙂 They are a more cryptic species so I think we often miss such interactions / behaviours.