February 1, 2012 | 65
Neat observations are published on animals all the time. Many are relatively mundane, or are additional records of things we already know about. But some are really fantastic and have the potential to open a whole new chapter in our understanding of behaviour, ecology and evolution. As we’ll see, even if they’re not brand new, we all benefit once these observations are brought to wider attention. Within recent weeks a really neat new paper has appeared. It’s gotten a reasonable bit of attention online already (in the blogosphere, my homeboy Ed Yong already covered it over at NERS), but I find it so fascinating that I just have to cover it myself.
Sunfish are weird, and you don’t have to be a fish-fan to find them bizarre and wonderful. No tails, no swimbladders, no ribs, no
pectoral or pelvic girdles, a really short vertebral column, and so on. I’ve always been amazed by the sizes they reach (over 3 m and maybe a few tons) and also by their incredible morphology – if you want a nice review of the group, see this article at Lord Geekington. Sunfish are so-named as they’re most often seen lounging at the surface, supposedly ‘sunning’ themselves after foraging in cool or cold water. You might argue that they’re convergent with an equally bizarre and fascinating group of tetrapods, the leatherback turtles.
It’s a neat new paper in the current issue of Marine Biology that’s caught my attention. It reports observations made during June 2010 when Takuzo Abe and colleagues were aboard the Hokkaido University research vessel the Oshoro Maru in the waters of the western North Pacific. Their observations are sunfish-based, but they also involve those fantastic oceanic birds, the albatrosses.
A school of 57 Ocean sunfish Mola mola, all aligned and heading in the same direction, were observed at the water surface, the tips of their fins breaking the water. It was noted that most sunfish in the school carried the parasitic copepod crustacean Pennella – it buries its head in the tissues of its host, and mature individuals trail a long egg string out the host’s side (Abe et al. 2012). Pennella is the biggest copepod.
It was then observed that a Laysan albatross Phoebastria immutabilis was in close association with the school. The fish seemed to follow the bird, as if they were soliciting its attention. Remarkably, the albatross was then seen to pull one of those parasitic copepods from the body of one of the sunfish. Other albatrosses were seemingly attracted by the activity, and were seen to remove parasites from other sunfish in the school. Some were Black-footed albatrosses P. nigripes. The sunfish seem to be trying hard to attract the attention of the birds: some “appeared to present themselves by swimming sideways next to birds” (p. 2), and the authors hypothesise that this is why the sunfishes were at the surface in the first place (Abe et al. 2012). One author on the paper, Keiko Sekiguchi, observed and photographed six Black-footed albatrosses pecking at an Ocean sunfish in 2005, so it seems that the same symbiotic behaviour was going on here as well. Furthermore, Abe et al. (2012) draw attention to the fact that Pennella has previously been reported as a consistent prey item of Hawaiian Black-footed albatrosses (Harrison et al. 1983) – an observation that provides additional support for this plausibly being a routine bit of behaviour.
Not unreasonably, then, Abe et al. (2012) propose that a symbiotic relationship exists between sunfishes and albatrosses. Abe et al. (2012) are the first authors to photo-document this remarkable behaviour and bring it to wide attention. However, while they’ve definitely written more about this issue than anyone else ever has, they aren’t the first to document it: seabird biologists have been saying for years that albatrosses and sunfishes have some sort of symbiotic ‘cleaning’ relationship. Dayton Alverson (2008) specifically referred to it in his autobiography on life as a marine biologist. Even better, Loye Miller (1940) wrote how “A sunfish was actually seen to swim toward a pair of resting [Black-footed] albatrosses and turn on its side. However, the birds were disturbed before I could see any actual delousing take place. It does seem likely that they might act as ‘tick birds’ for the great inert molas” (p. 236) [having mentioned ‘tick birds’, I can’t, of course, move on without reminding you that oxpeckers - the ‘tick birds’ of popular lore - are not necessarily benign, helpful little buddies than clean host mammals of their parasites. They may be vampiric quasi-parasites themselves].
Anyway, there’s a world of difference between saying “I saw this thing happening once” (cf. Miller 1940) and documenting that thing with good photos, so I don’t want to imply that I’m downplaying the significance of Abe et al.’s (2012) paper.
There’s a lot we don’t know about seabird behaviour, and these observations raise some interesting questions. If this ‘sunfish cleaning’ behaviour is a regular thing for albatrosses, do albatrosses rely on sunfishes as a regular resource, or is it an opportunistic relationship that arises by chance? If albatrosses do rely on sunfish as a resource, do albatrosses suffer when good numbers of sunfish aren’t around, and do sunfish need albatrosses to maintain good physical condition? Is the behaviour restricted to Phoebastria, or is it more widespread in albatrosses, or in tubenoses as a whole? Are any of the morphological peculiarities seen in albatrosses (like bill-tip shape) linked to specialisation for this habit? And – given that albatrosses and sunfishes have been around for more than 30 million years – how long has this relationship been at work? Do other oceanic birds behave in the same way when confronted with parasite-laden sunfish? And are sunfish ‘partner-specific’, or are they keen to get anyone to peck at their parasites?
Changing winds have been beneficial to Wandering albatrosses
While I’m here, there’s one other bit of albatross news that’s very much worth reporting. Most aspects of the global climate crisis create new problems for animal species. Increasingly, birds aren’t able to synchronise their migrations with the availability of the resources they rely on, or to maintain good plumage condition in the face of declining resources and degrading habitats. Rainforests are dying due to drought, polar and tundra habitats are disappearing, and avian diseases (botulism, West Nile virus, avian cholera and so on) seem to be on the rise as temperatures at higher elevations and latitudes become more equable. And so on. Sticking with albatrosses, most data indicates massive decline due to mortality caused both by plastic pollution and by the longline fishing industry. The Commission for the Conservation of Antarctic Marine Living Resources estimated that 10,000-20,000 albatrosses are killed each year in the southern Indian Ocean alone as a result of the Patagonian toothfish industry.
However, another recent paper shows that some changing climatic conditions can be of benefit to some species. Weimerskirch et al. (2012) used decades worth of data on the foraging ranges of Wandering albatross Diomedea exulans to show that the birds have been able to exploit the increasingly strong, more poleward, westerly winds that have developed as a result of global climate change. Now, the albatrosses fly faster and move further than they did a few decades ago. The consequences are that they don’t have to spend as much time foraging to get the food they need, their breeding success has improved, and the birds themselves have increased in weight by more than 1 kg (Weimerskirch et al. 2012).
In this time of doom and gloom, it’s so nice to hear a positive story. But, alas, it seems to be a short-term thing, since “these positive effects may not last in the future” (Weimerskirch et al. 2012, p. 213). Projections are that the westerlies will continue to move poleward, with wind conditions in the region currently favourable for Wandering albatrosses degrading substantially beyond 2080.
We’ll be coming back to tubenoses, and other kinds of seabirds, at some point in the near future. For previous Tet Zoo articles on seabirds, see…
Refs – -
Abe, T., Sekiguchi, K., Onishi, H., Muramatsu, K. & Kamito, T. 2012. Observations on a school of ocean sunfish and evidence for a symbiotic cleaning association with albatrosses. Marine Biology http://dx.doi.org/10.1007/s00227-011-1873-6 [free pdf]
Alverson, D. L. 2008. Race to the Sea: The Autobiography of a Marine Biologist. iUniverse (Bloomington, Indianapolis).
Harrison, C. S., Hida, T. S. & Seki, M. P. 1983. Hawaiian seabird feeding ecology. Wildlife Monographs 85, 3-71.
Miller, L. 1940. Observations on the Black-footed albatross. The Condor 42, 229-238
Weimerskirch, H., Louzao, M., de Grissac, S., & Delord, K. (2012). Changes in Wind Pattern Alter Albatross Distribution and Life-History Traits Science, 335 (6065), 211-214 DOI: 10.1126/science.1210270