Among all the dolphin groups of the past weeks, one of the three small cetaceans we work with was still missing this field season: The Burmeister’s porpoise/marsopa espinosa/Phocoena spinipinnis.
Of course one reason for this was that the study areas we selected were presumably typical Chilean dolphin habitat, which is not where you would go look for the “marsopas”, as they prefer deeper waters. The other, probably more important reason was that it can be incredibly hard to spot marsopas. Picture a really shy animal, that disappears with its long diving phases once you have come somewhat close to its original position and then pops up 5 minutes later, 500 meters away. ...And then it doesn’t even have an appropriate dorsal fin that could be spotted at this distance. Well, marsopas do have fins, but they’re small and flat and don’t stick out of the water as dolphin fins do. So the only time one is ever able to spot those animals, is when there is nearly no wind at all and the sea is smooth and clear (which doesn’t happen too often in the Chiloé Archipelago).
Three Burmeister's porpoises barely break the surface with their backward pointing dorsal fins. Their low profiles make them really hard to spot. (photo: Sonja)
This is also why there is so little literature or photos of this species. Nearly all published articles are based on carcasses obtained from bycatch and few stranding incidents. That is where we know from that the Burmeister’s porpoise inhabits the coastal waters from northern Peru to Brazil and usually feeds on fish like anchovy and hake (Brownell et al., 1999).
But this day, we got very lucky: In a sheltered bay with deep waters just when heading back from our survey area for this day, a flat back with an unmistakable back-pointed low profile fin slowly disappeared in the distance. “Marsopa!” Despite our excitement, we tried to approach carefully to not scare them away, what didn’t seem to have worked at first: What we got was typical marsopa behaviour: two or three surfaces, then nowhere to be found for what seemed like ages and then popping up at the other side of the bay. Again, we approached them, but what happened then was really unexpected. Eight animals – the largest group of Burmeister’s porpoises we had ever seen – surfaced nearly simultaneously about 30 m next to the boat.
The friendly group of Burmeister's porpoises is still hard to spot..... (Photo: Lea)
The close-up view of the back of a Burmeister’s porpoise is somewhat bizarre. It always reminds me of that of a horseshoe crab, wide and round with a backwards pointed slim dorsal fin which is spiked with horny little tubercles that are the origin of its Latin second name “spinipinnis” (spina=lat.: thorn; pinna=lat.: spine). The purpose for this porpoise (to stress this word play certainly nobody has ever used before, hahaha ;-) ) is completely unknown.
Burmeister's porpoise showing off the tubercles (little nobules) along the back and dorsal fin. (photo: Sonja)
And that is about all you’ll ever get to see of this animal, if you’re lucky enough to encounter one alive. .... That is until you get exceptionally fortunate to meet those not-so-shy, very-friendly-indeed porpoises we found this day. The group started to show interest in our boat, circling it and appearing at close distances every time they surfaced. We confirmed eight individuals, including two calves. One of the porpoises then separated from the group and passed beneath the zodiac, curiously bending its neck to sneak a peek at us. It repeated to do so several times over the duration of about fifteen minutes, while the others also stuck around and from time to time passed beneath us, as our GoPro-camera footage revealed. The water was rather murky but the porpoise passed close enough to recognize its dark patches around the eyes and the “melon”, the frontal part of the head in cetaceans which they use for echolocation. This coloration pattern is not particularly well described for the species, as different shades disappear fast when the animal is exposed to air and there hadn’t been underwater pictures available (at least that we, Google or any public record knew of) until our quite spectacular sighting last year, where we filmed the Burmeister’s porpoise for the first time underwater.
A Burmeister porpoise takes a look at the underwater camera. Note the dark eye ring which is similar to that of the vaquita (the Mexico desert porpoise that is in danger of extinction....). Also spot the darker shaded melon above the snout- (photo: still image from GoPro video, yaqupacha Chile project)
Another pass of the camera by our friendly porpoise - revealing its body shape and funny fin (photo: still image from GoPro video, yaqupacha Chile project)
We stayed with the group – or rather: the group stayed with us – as long as they found entertainment in us. We took plenty of pictures and videos and then headed back home filled with delight and positive marsopa-vibes from nose to rubber boots.
Sightings like this are very valuable, because as mentioned before, there are few studies based on living animals. By recording where the porpoises were seen, what the conditions were at that spot, how many individuals we noted, we can make relevant assumptions about their habitat preferences and typical group sizes.
Give me a live porpoise any day and it will be a GREAT DAY!
Sonja and Poli photograph and film the friendly porpoise (centre). (photo: Lea)