Tetrapod Zoology

Caperea alive!

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ResearchBlogging.org

By now you might be relatively familiar with the bizarre soft tissue and bony anatomy of the peculiar, poorly known Pygmy right whale Caperea marginata [a juvenile Caperea that stranded on New Zealand is shown above; original image by New Zealand Department of Conservation, from Te Papa's Blog]. If you missed the relevant articles you might want to check them out here (on the giant, asymmetrical laryngeal pouch), here (on the vertebrae and ribs) and here (on the skull, ribs and tail). These articles (which were very much thrown together without any planning: they were spin-offs of the [unfinished] pouches, pockets and sacs series) were devoted entirely to the animal’s anatomy, and didn’t touch on what we know about this weird little whale’s ecology and behaviour.

But what do we know about Caperea‘s ecology and behaviour? “Not much” is the usual answer. That’s true but, as we’ll see, we do know more than most people think we know.

For a start, we do at least have some idea of what it eats: the stomach contents of stranded specimens, and of specimens captured by whaling vessels, included calanoid copepods and euphausiids (krill). The capture of such small, planktonic prey is in agreement with the fine baleen of this species (Sekiguchi et al. 1992). Prey of this sort is particularly abundant in the Subtropical Convergence (at the northern edge of the subantarctic zone), and it might be that Pygmy right whales are, correspondingly, most abundant in this part of the ocean. It would explain why they strand most often on places like Tasmania and Stewart Island. Many Caperea strandings are of individuals 3-3.5 m long: this is probably the size at which young animals are newly weaned, and they might be prone to stranding at this age because they’re inexperienced (Kemper & Leppard 1999) [image below shows Caperea to scale with a person; image by Chris huh, from wikipedia].

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Having referred to the capture of Caperea by whaling ships, it’s worth saying that – while I’m not entirely sure how often Caperea gets captured – it seems to be a rare event. Two specimens captured in the South Atlantic by a Russian ship were reported by Ivashin et al. (1972), while another one was captured in deep offshore waters near Tristan da Cunha in 1970, again by a Soviet vessel (Budylenko et al. 1973).

These interactions with whalers raise the interesting question of how Caperea copes when confronted with attack or predation, though note that I’m not necessarily saying that a whale’s response to a whaling ship is going to be the same as that elucidated by killer whales (though anecdotal evidence suggests that it might be). This aspect of behaviour was studied in mysticetes by Ford & Reeves (2008). They showed that right whales, humpbacks and grey whales used fight (they stay put and actually try to battle off killer whales), while rorquals used flight (swimming rapidly away, and continuing to try and flee even when under direct attack). Alas, we don’t know what Caperea does, and I’m not sure it’s possible to make an educated guess given that Caperea is a weird composite of unique, rorqual-like, and balaenid-like features.

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Having mentioned Caperea and ships, there’s a 1990 account where an individual encountered in Cockburn Sound, Australia, swam rapidly toward a boat while “nodding its head noticeably” before scraping its back against the hull. It then swam at the boat even faster, then “lift[ing] the boat out of the water and almost caus[ing] the occupants to to thrown out!” (Kemper et al. 1997, p. 81) [adjacent photo, by J. Dutton, from Kemper et al. (1997), shows a Caperea encountered in Spalding Cove, South Australia. The arrows points to the paired blowholes and indistinct white bar at the back of the head, one of several pale, variable markings present in the species (others include white patches on the sides of the throat and chevrons on the back)].

Lunger or skimmer?

One question that’s often been asked about Caperea is how it feeds. Mysticetes are (mostly*) either lunge-feeders – like rorquals – or skim-feeders – like right whales (I haven’t yet covered right whales at all, but for some discussion of lunge-feeding in rorquals, see From cigar to elongated, bloated tadpole: rorquals part II and the other articles linked to below). Caperea is (almost) certainly more closely related to right whales proper (the balaenids) than it is to other mysticetes [UPDATE: maybe not.. see comments!], so balaenid-like skim-feeding might seem more likely. In fact, I’ve always said (I mean, at conferences and in discussions with colleagues) that this is correct as I have a recollection of reading about the observation of skim-feeding in one individual [image below taken in 1967 in Plattenberg Bay, South Africa. Until recently it was the only photo showing a live Pygmy right whale].

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* Yes, I know it’s more complicated than this, given that grey whales filter sediment and scrape food from kelp, and that some species combine different feeding styles.

It turns out that Arnold (1987) observed a Pygmy right whale feeding near the surface on copepods and euphausiid larvae in Portland Habour, Victoria; a few other reports of pygmy right whales seen in offshore waters around Australia also seem to have been feeding (Kemper et al. 1997, Kemper 2002). Exact details of the feeding styles observed are scant, but the lack of rapid lunging and wide mouth-gaping implies that these whales were skim-feeding.

Skim-feeding behaviour in Caperea is also supported by the discovery of feathers and a plastic bag (ahh, how I love plastic pollution) in the stomach contents of a South African specimen (Sekiguchi et al. 1992). The ingestion of these objects is indeed consistent with surface skim-feeding, but I suppose you could argue that such objects might still be encountered at depth.

All Caperea sightings are of lone animals – - right?

One of the few things that ‘everybody’ knows about the Pygmy right whale – I’ve unwittingly perpetuated this view myself – is that it’s only ever been seen live on a handful of occasions, and that it’s only ever encountered as a singleton. If this is what you think, you’re in for a shock. Actually, groups of two to five have been seen on quite a few occasions, and large and even enormous groups have been recorded on several occasions.

Matsuoka et al. (1996) reported a November 1992 observation of about 80 Pygmy right whales, seen south of Western Australia. Another group – this time of ‘only’ 14 whales – was seen in the south-west Pacific in January 2001 (Matsuoka et al. 2005). In both sightings, the whales were swimming slowly near the surface; the whales seen in 1992 were suggested to be waiting for their copepod prey to migrate vertically to the surface.

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By far the most remarkable group was observed in June 2007 during an aerial search for Pygmy blue whales Balaenoptera musculus brevicauda (another really interesting mysticete that I’ll have to cover some time). At a location about 40 km south-west of Portland, Victoria, a group of 100 or more Caperea were observed (Gill et al. 2008) [photo of the aggregation shown above provided by Peter C. Gill of Blue Whale Study; used with permission]. Some of the whales were submerged at the limits of visibility, suggesting that even more individuals may have been present but not at the surface. Many of these whales were subadults between 3.5 and 5.5 m long; adults of up to 6.5 m were also present but animals smaller than 3.5 m were absent. Body size and shape, head shape and pigmentation all allowed the whales to be identified as Caperea. Their behaviour was co-ordinated: they were seen swimming slowly in an anticlockwise movement, and later observed moving in the same direction while stretched out in a serpentine line (Gill et al. 2008).

As usual, we don’t know as much about this bizarre little whale as we’d like to, and it can still be said that it’s poorly known. Nevertheless, it isn’t known only from the anatomy of stranded specimens, nor is it known only from fleeting one-off observations as you might think; we know what it eats, we have some data that has a bearing on its feeding behaviour, ecology and habitat preference; and we know that it forms large and even enormous aggregations at times. For a 6-m-long mammal known to science since 1846, this might be good, or it might be really bad.

Many thanks to Pete Gill, C. J. Hazevoet and Dartian for their help with this article. Be sure to check out the Blue Whale Study site.

For previous articles on Caperea and other baleen whales, see…

Refs – -

Arnold, A. 1987. Portland’s chance encounter with a pygmy right whale. Australian Natural History 22, 266-270.

Budylenko, G. A., Panfilov, B. G., Pakhomova, A. A. & Sazhinov, E. G. 1973. New data on pygmy right whales Neobalaena marginata (Gray, 1848). Trudy Atlanticheskii Nauchno-Issledovatel’skii Institut Rybnogo Khozyaistva I Okeanografii 51, 122-132.

FORD, J., & REEVES, R. (2008). Fight or flight: antipredator strategies of baleen whales Mammal Review, 38 (1), 50-86 DOI: 10.1111/j.1365-2907.2008.00118.x

Gill, P. C., Kemper, C. M., Talbot, M. & Lydon, S. A. 2008. Large group of pygmy right whales seen in a shelf upwelling region off Victoria, Australia. Marine Mammal Science 24, 962-968.

Ivashin, M. V., Shevchenko, V. I. & Yuchov, V. L. 1972. The pygmy right whale Capeara marginata (Cetacea). Zoologicheskii Zhurnal 51, 1715-1723.

Kemper, C. M. 2002. Distribution of the pygmy right whale, Caperea marginata, in the Australasian region. Marine Mammal Science 18, 99-111.

- ., Dutton, J., Foster, B. & McGuire, R. 1997. Sightings and strandings of the pygmy right whale Caperea marginata near Port Lincoln, South Australia and a review of other Australasian sightings. Transactions of the Royal Society of South Australia 121, 79-82.

- . & Leppard, P. 1999. Estimating body length of pygmy right whales (Caperea marginata) from measurements of the skeleton and baleen. Marine Mammal Science 15, 683-700.

Matsuoka, K., Yoshihiro, F. & Pastene, L. A. 1996. A sighting of a large school of the pygmy right whale, Caperea marginata, in the southeast Indian Occean. Marine Mammal Science 12, 594-597.

- ., Pitman, R. L. & Marquez, F. F. C. 2005. A note on a pygmy right whale (Caperea marginata) sighting in the southwestern Pacific Ocean. Journal of Cetacean Research and Management 7, 71-73.

Sekiguchi, K., Best, P. B. & Kaczmaruk, B. Z. 1992. New information on the feeding habits and baleen morphology of the pygmy right whale Caperea marginata. Marine Mammal Science 8, 288-293.

Comments

  1. #1 Boesse
    November 8, 2010

    As Morgan will be be able to explain in better detail soon, Caperea ends up being more closely related to “Balaenopteroidea” (Balaenopteridae + Eschrichtiidae) fairly consistently in molecular phylogenies, and a recent morphological analysis by Felix Marx has supported a Caperea + Balaenopteroidea clade.

    Given the morphology of the rostrum and dentary, skim feeding is the obvious feeding mode to predict, I imagine. With regards to surface debris showing up in the digestive tracts of these guys – some rorquals lunge feed at the surface (Megaptera does, and photos exist of multiple species of Balaenoptera doing so as well). So its possible for some of that stuff to get accidentally ingested by lunge feeders as well. I recently read about (I can’t remember where I read it) dozens of birds turning up in the digestive tract of a balaenopterid, which isn’t surprising either, but it is totally awesome.

    Marx, F. 2010. A large cladistic analysis of mysticetes, and comments on the transition from teeth to baleen. Journal of Mammalian Evolution (Online Early):1-24.

  2. #2 Domestigoth
    November 9, 2010

    These posts are fascinating — I’m constantly amazed at how little we (as humans) know about so many of the species on our planet, and more so when those species are large mammals or otherwise very obvious critters. I wish I knew enough to ask intelligent questions and have real discussions about these sorts of things (my biology knowledge really tends more towards reptiles and creepy-crawlies; mammals have never captured me quite as much), but even without that, I’m really enjoying reading these posts of yours and learning more about animals that I had never even heard of before.

  3. #3 Dartian
    November 9, 2010

    Trintan da Cunha

    Tristan da Cunha, surely?

    image below taken in 1967 in Plattenberg Bay, South Africa. Until recently it was the only photo showing a live Pygmy right whale

    In this case, ‘until recently’ means ‘until 1986′; you mention in the article the juvenile pygmy right whale individual that unexpectedly showed up off Portland, Victoria, in the eighties. It stayed in and near the harbour from November 1986 to February 1987 and was – obviously – photographed many times.

  4. #4 Darren Naish
    November 9, 2010

    Thanks much for comments. I knew that some studies do indeed find Caperea closer to Balaenopteridae than to Balaenidae (e.g., Sasaki et al. 2005) – I mentioned it in one of the previous articles – but I suppose I hadn’t realised that it was becoming a ‘consensus’ view. I should also have mentioned that the skull anatomy of Caperea looks most suited for skim-feeding. And, yeah, pretty obvious that lunge-feeding can occur at the surface (look at photos here): finding surface-floating objects in a mysticete’s stomach can therefore be argued to tell you nothing about feeding style.

    Thanks for other comments and corrections.

    Ref – -

    Sasaki, T., Nikaido, M., Hamilton, H., Goto, M., Kato, H., Kanda, N., Pastene, L. A., Cao, Y., Fordyce, R. E., Hasegawa, M. & Okada, N. 2005. Mitochondrial phylogenetics and evolution of mysticete whales. Systematic Biology 54, 77-90.

  5. #5 Krimeg
    November 9, 2010

    Great post, I didn’t know before such aggregations could occur and remain unnoticed until 1992.

  6. #6 William Miller
    November 9, 2010

    Cool.

    It really is fairly ‘pygmy’ for a baleen whale.

  7. #7 Dave Hubble
    November 9, 2010

    Darn – I keep getting drawn here from my usual invertebrate interests…

    I’ve read that groups of Right Whales may feed in a V-formation – has this been observed in C. marginata?

  8. #8 Gray Stanback
    November 9, 2010

    Out of interest, what happened to the one in the picture? Was it released back out at sea, or do I not want to know?

  9. #9 Darren Naish
    November 9, 2010

    Dave – nope, no v formations reported in Caperea, at least not so far. Gray – the live-stranded animal shown at the very top was refloated and lived to tell the tale.

  10. #10 Raaf
    November 9, 2010

    Not about our favourite little whales

    …but something completely different
    ..a shrubbery ?

    I always ask myself why not join forces ?

    Today (I’m a computer-neanderthal) I ‘surfed’ to a site from someone called Brian Switek

    Wickedd stuff
    Fantastic things about Marsupial Lions, rafting lemurs, ancient gigantic shell crushing sharks and Elk-Moose.

    Why not join forces ?
    Our goal is the same

    Life is a shallow Tethys sea
    Toothed ‘gulls’ and all

  11. #11 Boesse
    November 9, 2010

    Darren,
    I’m not sure it’s quite a consensus view yet, but I’d say there’s definitely enough support for it for me to be able to envision it as a consensus view within a few more years of research on the subject. IIRC, the topology in Felix Marx’ paper would indicate that the “balaenid morphology” of the skull has evolved twice, which is totally freaking weird. But then again, so is Caperea in general.

  12. #12 Mark Evans
    November 10, 2010

    In the photo of the stranded juvenile at the top it looks as if it’s got “flipper pockets” similar to those of beaked whales which would agree with the streamiling of the body discussed on earlier posts.

  13. #13 DDeden
    November 10, 2010

    Surface skimming for plankton etc. matches with ancestral laryngeal air sacs…frog tadpoles are generally submerged filter feeders but (speculating) can’t eat floating-at-surface materials (due to water surface tension) and breathe at the same time, so a leap-frog manuever and air sacs developed (better energy efficiency) …similarly ape ancestors rake-foraged at surface of wetland ponds for hydrocharis etc. with similar result.

  14. #14 David Marjanović
    November 11, 2010

    Surface skimming for plankton etc. matches with ancestral laryngeal air sacs…

    Even in Caperea the air sacs are far too small to provide any noticeable buoyancy.

    frog tadpoles are generally submerged filter feeders but (speculating) can’t eat floating-at-surface materials (due to water surface tension) and breathe at the same time

    …You did know that tadpoles have gills, didn’t you?

    …similarly ape ancestors rake-foraged at surface of wetland ponds for hydrocharis etc. with similar result.

    Evidence?

    We all know you’re able to come up with a scenario. But this here is science. You need to show us how we can find out whether your scenario actually happened.

  15. #15 Maravilloso
    November 23, 2010

    For more studies (molecular with a ton of data) that definitively place Caperea with balaenopterids see the following:

    Deméré, T., McGowen, M., Berta, A., Gatesy, J. (2008). Morphological and Molecular Evidence for a Stepwise Evolutionary Transition from Teeth to Baleen in Mysticete Whales. Systematic Biology, 57(1), 15-37.

    McGowen, M. R., M. Spaulding, and J. Gatesy. 2009. Divergence date estimation and a comprehensive molecular tree of extant cetaceans. Molecular Phylogenetics and Evolution 53: 891-906.

    Steeman ME, Hebsgaard MB, Fordyce RE, Ho SYW, Rabosky DL, Nielsen R, Rahbek C, Glenner H, Sørenson MV, Willerslev E: Radiation of extant cetaceans driven by restructuring of the oceans. Syst Biol 2009, 58:573-585.

    R. W. Meredith, J. Gatesy, J. Cheng, M. S. Springer (2010).
    Pseudogenization of the tooth gene enamelysin (MMP20) in the common ancestor of extant baleen whales. Proc. R. Soc. B online early doi:10.1098/rspb.2010.1280.

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