Caperea alive!

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].

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.

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].

* 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.

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...

• A 6 ton model, and a baby that puts on 90 kg a day: rorquals part I
• From cigar to elongated, bloated tadpole: rorquals part II
• Lunging is expensive, jaws can be noisy, and what's with the asymmetry? Rorquals part III
• The newest whales
• Inside Nature's Giants part II: whale guts and hindlimbs ahoy
• When GREY WHALES - you know, from the PACIFIC OCEAN - crossed the Atlantic
• Pouches, pockets and sacs in the heads, necks and chests of mammals, part III: baleen whales
• Did I mention that Caperea is really, really weird?
• Once more on little Caperea

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.