Wednesday, December 10, 2014

Wildlife Wednesday - Risso's dolphin

Photo by Fish_Thinkers
A while back on our local news, they mentioned some Uni post-grad students who had a social media presence of Fish Thinkers, and I started following them on Instagram (fish_thinkers). They have a blog and Twitter (@fish_thinkers) too.

They're fascinating because they have underwater cameras recording sharks and fish behaviour, so I've been quite excited to see some of their footage. They also post about fish and fishing and have mentioned Lord Howe Island and Balls Pyramid (both in Deep Diving) and some of the fish species I've had on Wildlife Wednesday (like Luderick).

Last week, they featured a Risso's dolphin that had been found stranded on a beach north of Wollongong (south of Sydney).

I hadn't heard of a Risso's dolphin nor seen one. So I had to do a bit of digging. I asked them about the scarring on this dolphin but apparently these dolphins often have scarring - although this animal had more than most.

So here's some information about Risso's dolphin, from the Australian Government environment website:

Risso's Dolphins are robust, blunt-headed animals lacking a distinct beak. A distinctive deep crease runs up the forehead. The flippers are recurved, long and pointed. The dorsal fin is tall and falcate (sickle-shaped). The mouthline slopes upward and there are typically no more than seven pairs of peg-like mandibular teeth that are often badly worn in older individuals. No maxillary teeth are present. The colouration and markings of adults are conspicuous, the body being very light grey to white with a narrow cape sometimes being visible. Extensive scarring appears to be primarily from aggressive encounters with conspecifics. There is a large anchor-shaped light grey patch on a dark ventrum. Newborns are also light grey in colour.

Risso's Dolphin occur mainly on steep sections of the upper continental slope (Baumgartner 1997), usually in waters deeper than 1000 m (Ross 1984), in tropical and warm temperate latitudes.

Risso's Dolphins show a marked preference not only for water greater than 1000m deep, but also for warm temperate to tropical conditions, although they do sometimes extend their range into cooler latitudes in summer (Leatherwood & Reeves 1983). They are therefore generally found in waters with temperatures ranging between 15–30 °C. Although they are primarily found in pelagic oceanic waters, Risso's Dolphin frequently move over the continental slope. 

They're found throughout Australian oceans, but haven't been sighted around Tasmania and the Northern Territory.

Thanks to fish_thinkers for interesting posts!


  1. Isn't he the most beautiful colour and pattern. I've never heard of them.
    Did they save this one?

    1. It's amazing, isn't it Lily? I thought of you when I saw it. I'm glad you hadn't heard of them either...makes me happy I 'borrowed' it for the post.

      Sadly this one wasn't saved and from the comments on the post this wasn't the first. They were waiting on a post mortem to determine the cause of death(s).

      Cate xo