Splashes, fins, and leaps!

Okay, here's a fun story.  Yesterday (21 March 2024) I was working at my desk, which at the moment has a view of the ocean, and something white offshore caught my eye.  I thought it might have been a whale spout at first, but I saw it again and could see it was more of a splash, so I grabbed my binoculars for a better view.  I could now see extensive splashing and backs of cetaceans that didn't look like whales, but they were ~3/4 mile offshore, so a bit distant. They were moving quickly to the south, but I had a spotting scope nearby, so I ran down the hall with it and set up just outside the door in hopes of identifying them.

Now I could see a very large group of dolphins, probably over 100 individuals!  I could see large distinct dorsal fins, some full-body breaches, some tail slapping — a very energetic group.  It was still far enough away that I wasn't sure about the species, but because it's rare to see so many dolphins close to shore off Bodega Head, I started shouting down the hallway for others to come see.

We had nice views of the dolphins, but I still wasn't sure about the species.  I could tell they weren't Bottlenose Dolphins (Tursiops truncatus) — they didn't have long beaks and the group size was too large.  I'd never seen Pacific White-sided Dolphins (Lagenorhynchus obliquidens) so close to shore, and usually they have some paler color on their dorsal fins and these dorsal fins looked dark to me.  Long-beaked Common Dolphins (Delphinus capensis) or Short-beaked Common Dolphins (Delphinus delphis) might have been possible, but they're not common in this area, and I couldn't see enough details to be sure.

At one point I had wondered about Risso's Dolphins (Grampus griseus) because some of the dorsal fins looked quite tall (tall enough that Orca even crossed my mind).  But I was thrown off because some of the smaller individuals leaping out of the water looked very pale below, especially in contrast with the darker backs.  I haven't seen Risso's Dolphins that often, but I think of them as being more uniform gray.  However, my lack of experience with the variation in this species likely biased my expectations.

I could see at least one boat out where the dolphins were, and was hopeful someone might have gotten a photo, so I sent out a few inquiries.  I didn't hear back...until this afternoon!  Bill Keener from The Marine Mammal Center let me know that they had a team on a research cruise out by Tomales Point around the same time.  They photographed a group of 100-200 Risso's Dolphins near Bird Rock.  The Marine Mammal Center kindly shared a couple of their photos, so here you go!  

Photo credit for both photos: N. Cristales/The Marine Mammal Center under NOAA permit # 26532.  [You can click on the images for larger versions.]

 

 

 

 

 

Such great photos!  

 

Risso's Dolphins are medium sized, reaching lengths of ~8.5-13 feet.  Note the prominent dorsal fin and the overall grayish coloration.  On a few individuals in the second photo you can also see that they're blunt-headed (similar to pilot whales).  Risso's Dolphins tend to prefer deeper water, but they are occasionally observed from shore.

 

With many thanks to The Marine Mammal Center crew for sharing their observations and wonderful photos.