Sunday, February 24, 2013

Feresa attenuata vs Kogia sima

Ini adalah versi bahasa Inggris untuk artikel tentang pembelajaran kejadian terdampar di Sanur Bali (19 Feb'13). Klik link ini untuk versi Indonesia-nya.

The mysterius cetacean stranded in Bali (19 Feb'13). For future stranding cases, a mattress should be inserted between the body and the boat  to prevent more stress to the animal

The verdict is out! A team of online juries consisting of Danielle Kreb, Benjamin Kahn, Randall Reeves, Robert Pitman, John Wang, Charles W. Potter and Thomas Jefferson agreed that the suspect ‘Feresa attenuata’ stranded in Sanur (Bali) on 19 Feb 2013 was more likely to be Kogia sima (dwarf sperm whale). And before anyone conjures up the image of the great sperm whale (Physeter macrocephalus), I’d like to say that, No, this is not the small version of that sperm whale. They are two different species altogether, although they do belong to the superfamily of Physeteroidea.

My good friend Naneng Setiasih once said that a scientist can make mistakes. What a scientist should not do is lying. What a scientist must do when he/she realised the mistake is to come clean. I always remember that, particularly now. Hence, I am writing this post to come clean. I mis-identified the animal; I thought it was something else, and it was not.

Here, I’d also like to share why I thought it was Feresa attenuata (pygmy killer whale) instead of Kogia sima (dwarf sperm whale), what I should have done to avoid mis-identification, and lessons learned. Included under the cut is some guidance to differentiate the two animals, so that others won’t repeat my mistake.

First Impressions are not always correct

Any fan of Jane Austen will know that the main premise of First Impressions (the original title of Pride & Prejudice) was based on Elizabeth Bennet’s first impressions of Mr Fitzwilliam Darcy. During their first meeting, Elizabeth wasn’t impressed with Darcy. Given Darcy’s pride attitude, I’d say Lizzy’s impressions were actually justified. She did not conjure up those impressions from nothing. Darcy did invite those negative impressions, one way or the other. Eventually though, as time went by, Lizzy learned real facts and saw the real Darcy as who he really was.

Before you’re thinking that you’re not at anymore, let me tell you that you are still here at my cetacean blog. I mentioned the 18th CE Pride & Prejudice here because, apparently, first impressions can also be misleading in my cetacean world in the 21st CE. At least to me. My first impressions during the stranding event led me into thinking that the animal was a Feresa attenuata. Only after re-checking the facts, I understood why it was a Kogia instead of a Feresa.

Feresa attenuata, from the National University of Singapore

Kogia sima, from the Convention on Migratory Species

Why I thought it was a Feresa attenuata:

In retrospective, it indeed would be much easier for someone to identify this species if they have encountered it before (so one has intuitive comparisons to differentiate Kogia from Feresa). I have never encountered a Kogia before. I have seen short-finned pilot whales (Globicephala macrorhynchus) and false killer whales (Pseudorca crassidens), two species that belong to a group called ‘blackfish’. Feresa attenuata belongs to that group. Somehow, as I interviewed the rescuers last Tuesday (19 Feb), my mind directly went to the blackfish group.

Here’s the thing. The body of the animal from the photographs I obtained from Nunome Jun-san was black. The animal doesn’t have a beak (like that of bottlenose dolphins, spinner dolphins, spotted dolphins or even beaked whales). Those were the tick-boxes for blackfish (a group of large-sized dolphin under the subfamily of Globicephalinae – Shirihai & Jarrett 2006). The head was rounded (instead of rather pointy). When I asked whether the animal had white lips, some of the rescuers said yes. I showed some blackfish pictures. The guys picked Feresa attenuata.

I immediately dismissed the pilot whale identification when I saw the falcate dorsal fin. Short and long-finned pilot whales (Globicephala sp.) don’t have such falcate dorsal fin (they have bulky dorsal fins). False killer whales (Pseudorca crassidens) don’t have falcate dorsal fin either. Melon headed whale (Peponocephala electra) has somewhat pointy head, more pointy than Pseudorca or Feresa. The animal did not have extensive white scars the way a Risso’s dolphin (Grampus grisseus) does. And then I asked if it had white lips. Some said it did. Hence I thought it was Feresa.

Why the juries were convinced it was Kogia sima:

However, it was not a Feresa. From a compilation of comments from Danielle Kreb, Benjamin Kahn, Randall Reeves, Robert Pitman, John Wang, Charles W. Potter and Thomas Jefferson, here’s what I can summarise:

Head shape: distinctive pointy head with uppermost part jutting out; lumpy appearance at close range.

Shape and location of the dorsal fin: falcate; dorsal fin size quite large relative to the back length

Colour: light grey, not pitch black as in melon-headed whale Peponocephala electra or pygmy killer whale (Feresa attenuata). No evidence of a ‘saddle patch’ (i.e., an area of skin under the dorsal fin which has different colour tone from the surrounding skin).

Lips: can be lightly pigmented (lightly coloured, unlike the heavily-pigmented Feresa)

Verdict: Kogia sima, dwarf sperm whale.

Ground checking

The verdict was passed on Thursday night (21 Feb), but I still wondered why I made the mistake. I also wanted to tell the rescuers that the species was not Feresa as I thought it was. Hence, I went back to Sanur on Friday morning (22 Feb). I bought with me my ‘bible’, the Shirihai and Jarrett (2006) identification book.

I first met Made Sudarma who works at Ena Dive. He joined the first rescue attempt (at 7am on 19 Feb) by herding the animal back to the sea with three dinghies. I showed him the two pictures of Feresa attenuata and Kogia sima. He couldn’t tell which one. But he did say that he didn’t see the white lips. The belly wasn’t white either. Made didn’t detect any ‘gill-like feature’ common in Kogia. He noted that the eyes were small (as in, not prominent the way the illustration in Shirihai and Jarrett). The colour, he noted, was not pitch black (Feresa is usually pitch black). More like black-greyish.

I showed Made the picture of local beach boy Mochang taking care of the animal on board of the jukung. At that time, I realised how I have mis-interpreted the picture. I thought Mochang’s hand was extended leftward towards the head. Hence, I had dismissed that picture, thinking that we couldn’t see the animal’s head clearly. Only yesterday, back in ‘the crime scene’, I started to see that the animal’s head wasn’t of Feresa’s.

The photograph I should have examined more carefully

I then went to the local warung where I had obtained the photographs from Nunome Jun last Tuesday morning. I met Wayan Wiranata and Jun-san there. First, I showed the Feresa picture to Wayan. He was like, yeah, well… Then I showed him the Kogia sima picture. He almost jumped from his seat as he said with distinctive Balinese accent, ‘That’s it! That’s the one. The weird-looking dolphin!’

We then studied the Kogia sima picture again. Wayan repeatedly agreed that the head shape was the same. The eyes were small. The look was the weird look that animal had. He had doubted that it was a dolphin (perhaps what he meant was bottlenose, spinner, spotted or other more commonly known dolphins). He had actually thought whether it was a whale.

Wayan also dismissed that the skin was like rubber (I’ve touched a false killer whale before; its skin felt like rubber. I assume that is how the skin of a Feresa feels like). Then he said, ‘The skin was so soft. Like the skin of a tongkol [ed: Euthynnus sp.]. Like, you can easily scratch and hurt that skin. It didn’t feel like the skin of most dolphins.’

I informed Jun-san that her picture made us realise how unique this species was. She photographed the Kogia sima pages from Shirihai and Jarret for her references. Without her giving me the pictures, we would never know what species it was. I am very thankful to her, and also to Wayan for confirming the sighting.

Lessons learned

First impressions are not always correct. Hence, avoid rushing into identification. Send pictures to your network of experts and wait for the verdict. If you need to publish something (like I did with the blog and the Whale Stranding Indonesia), say ‘suspect’ Species X. I should have said ‘suspect Feresa’ instead of just ‘Feresa’.

Don’t just show the pic of what you thought it was. When I learned that the animal had black skin and rounded-ish head with no beak, I immediately jumped to the blackfish group. Instead, let them browse the book, just in case they can find that species themselves. I did let them browse the book, but I have to admit that I kept coming back to the blackfish.

Don't ask probing questions. Coming back to the white lips: In retrospective, I should have not asked, ‘Were the animal’s lips white?’ Sociologists would say that it was a probing question, and some informants do have the tendency to please interviewers by saying yes. Hence, I should have asked, ‘Any coloration on the lips?’

Listen carefully; don’t make immediate judgements. During my Tuesday (19 Feb) interview with the rescuers, I ignored one possible important information. A rescuer from Ena Dive asked me if the animal breathed with gills. I said no, whales and dolphins breathed with lungs. In retrospective, it is possible that the rescuer asked about the gill because he thought he saw something that looked like gill on the 19 Feb cetacean.  Only Kogia sp had gill-like features on their head. But then again, it was also possible that the rescuer was simply unaware that marine mammals breathe with lungs, not with gills. The point is: listen. Start with blank, clean slate, as clean as can be.

Study the photographs carefully. I confused the head of Kogia with the hand of one of the rescuers (Mochang) in the picture above. The picture had back lighting, and it was difficult to study it in Sanur (the reflected light from the ocean disturbed the details). But I should have just returned home and studied the photographs under better, more neutral lights. In my defence, I didn’t return home until 6pm that day due to other meetings I had to do.  I then rushed into editing the picture (to include Jun’s name for acknowledgement) and then published the story. I should have just said ‘suspect’ species Feresa. I did not.

The head shot of the Kogia sima in Sanur

Why is correct species identification necessary?

From the rescue point of view, correct species identification helps in grouping the size of cetaceans often stranded in Bali. This information will lead to better design of rescue efforts, including what stretcher specification should be prepared for each stranding site.

Correct species ID also helps us to confirm the existence of a species never sighted before in a place (in this case, Bali). So far I know, Bali has 12 species: spinner dolphins (Stenella longirostris spp.), spotted dolphins (Stenella attenuata), bottlenose dolphins (Tursiops sp.), short finned pilot whales (Globicephala macrorhynchus), Fraser’s dolphins (Lagenodelphis hosei), Risso’s dolphins (Grampus grisseus), pygmy killer whale (Feresa attenuata), false killer whale (Pseudorca crassidens), humpback whales (Megaptera novaeangliae), sperm whales (Physeter macrocephalus), rough-toothed dolphins (Steno bredanensis), and Bryde’s whales (Balaenoptera brydei). Now we can add dwarf sperm whale (Kogia sima) to the list.

If the species is never sighted before throughout the entire Archipelago, our cetacean list for Indonesia is expanding, thanks to that one sighting (or even one photograph) of that species. If the species is never sighted before in Asia, the photographs will add to our understanding of this species in this region. Now, imagine if the species is never sighted before around the world. The photographs or recordings of that one stranding event are contributing a significant leap to the whole marine mammal science. Of course, confirmation of such a case can take years. However, it will never start without that one photographed sighting.

So that’s it. Case closed. We had a Kogia sima stranded in Sanur on 19 Feb 2013. It is very likely that the 19 Feb stranding might be the first sighting of Kogia sima in Bali. We do have Kogia sima in other parts of Indonesia (eastern parts, notably), but not in Bali. These animals are very elusive; most information we know were from stranding events.

Kogia sima it is. I rest my case.


Anonymous said...

The best clue here is the false gill. I had seen a lot of Kogias and this is a very striking feature when you see it, as are the strange fang-like teeth.

A clear false gill can be seen in the upper photo. So this is a Kogia

But... What Kogia?

Not so easy to answer this... Because could be also a Kogia breviceps.

Pablo Vald├ęs

Icha said...

Sorry for the late reply, Pablo. I still couldn't see the false gill in the upper photo. But yes, it's possible that it's Kogia breviceps. I've never seen a Kogia with my own eyes, but I should be able to identify it if I see it myself. Particularly after this mistake :-D