tetrapodzoology

Tetrapod Zoology has moved

tetrapodzoology — Tue, 08 Nov 2011 09:53:00 +0000

Tetrapod Zoology has moved

You are currently at the old, defunct version of Tet Zoo. To see new stuff (from July 2011 to present), click here. See you there.

tetrapodzoology Tue, 11/08/2011 - 04:53

Goodbye Tet Zoo ver 2. This really is the end.

tetrapodzoology — Tue, 05 Jul 2011 06:16:00 +0000

Goodbye Tet Zoo ver 2. This really is the end.

On January 23rd 2007, Tet Zoo ver 2 - the ScienceBlogs version of Tetrapod Zoology - graced the intertoobz for the first time. There was rapturous applause, swooning, the delight of millions. Looking back at it now, that very first ver 2 post is rather odd. It's on the blood-feeding behaviour of oxpeckers (Buphagus) and it only really mentions the move to ScienceBlogs in passing, as if it wasn't a big deal.

In reality, being invited in to join the ScienceBlogs collective was a big deal, and were I to go back in time and re-live the writing of that particular article I'd do much more of a "Hello, welcome to Tetrapod Zoology, this is me and this is what I do". Oh well, never mind. Incidentally, I never did finish writing everything that I wanted to on the evolution of blood-feeding in tetrapods...

Over the four-and-a-bit years that followed that January 2007 article, the Tetrapod Zoology blog went from strength to strength. Readership increased exponentially [mostly: see hilarious counter fail below], as did its reputation as a (mostly) reliable online source regarding all things tetrapod. Today, a significant percentage of interested people (including amateurs, media-types and professional researchers) are at least aware of Tetrapod Zoology, and some of them read it or even leave comments on it.

Within the ScienceBlogs franchise, Tet Zoo has been - I blushingly and humbly admit - one of the most popular blogs for a while, frequently if not typically being in the top 10 most visited, and with a consistent and notable presence in the 'reader's pick' selection. It's consistently been in the top 5 at Nature Blog Network. I can't compete with the ScienceBlog bloggers who write about religion, politics and global warming denialism, but that not a fair comparison, as I wouldn't try and compete with anyone who writes about 'X Factor' or which females celebrities have been photographed in bikinis lately either.

Tet Zoo ver 2: edited highlights

It's been a long, strange trip. Things I've chosen to blog about have fed back into my academic research and popular writing, and vice versa. Many subjects have been visited repeatedly to the extent that they've become blogosphere memes. Terrestrial stalking azhdarchids, big-brained dinosauroids, shoebills, matamatas, babirusas, the toads of the world, sea monsters, 'mystery' carcasses. Let's use this as an opportunity to look back at just some of the more notable topics that I've blogged about at Tet Zoo ver 2...

One of the earliest of Tet Zoo ver 2's articles - that on the science of Godzilla - proved a big draw. I've done a few more articles on Godzilla since then, and even did a radio interview on the subject for Sceptically Speaking.
The Australian megacat article of March 2007 was also astonishingly popular. More work needs to done before we have a better handle on the situation with these enormous Australian feral cats. I'm convinced that they're a genuine phenomenon (I'm due to review the Williams and Lang Australian Big Cats book at some stage, so will be revisiting this issue in time).

In April 2007, Aetogate kicked off: a case wherein a team of palaeontologists in New Mexico were accused of plagiarising and knowingly pre-empting the work of others (the work concerned the Triassic archosaurs called aetosaurs). It even got brief coverage in Nature (Dalton 2008). It remains arguable whether the eventual outcome of this whole case was favourable or not.
In December 2007, I did my bit to raise awareness of the global amphibian crisis. I'd tried in previous months to review all the main anuran groups of the world, but failed. I succeeded on salamanders and caecilians though. Anyway, the global amphibian crisis is something I would visit several times later on.
Ankylosaur week (February 2008) was an enjoyable and memorable event
In March 2008 the speculative (and entirely hypothetical) big-brained theropod Avisapiens hit the big time: i.e., the mainstream published literature. It provided a good opportunity to review Tet Zoo's contribution to the whole 'smart dinosaur' meme. Most of my thoughts made it into the printed literature (Naish 2008).
The May 2008 article on stiletto snakes is a personal favourite, not only because it covers a fascinating group of snakes that deserve more coverage, but also because it inspired responses from people who had had personal experience with these snakes, and those who had done some of the research I was writing about (in particular Alexandra Deufel).
In May 2008, Mark Witton and I published our paper on terrestrial stalking in azhdarchid pterosaurs (Witton & Naish 2008). The media loved the story, and the publication of the paper in the 100% open-access PLoS ONE might mean that it has become one of the most-read technical papers on pterosaurs of all time.
Sea monster week (July 2008) was hugely popular and great fun.
The series on weird odontocete skulls - published here in the July and August of 2008 - provides a nice overview of odontocete diversity and covers a lot of material not much discussed in the popular literature.
My coverage in August 2008 of the decomposing raccoon nicknamed the 'Montauk monster' was far and away the most visited blog article I've written so far. It led to numerous mentions in the media and appearances on TV and so on.
The 'sauropod neck posture' event of May 2009 sparked a lot of discussion. It was timed to coincide with the publication of an open-access paper I co-authored with Mike P. Taylor and Mathew Wedel (Taylor et al. 2009).
Many people enjoyed the coverage of George Olshevsky's 'birds come first' model, reviewed here in June 2009.
The July 2009 coverage of series I of Inside Nature's Giants should be a useful resource to anyone who wants to know about much of the technical stuff covered in that most excellent series.
The series on mesonychians - and on taxa often regarded as mesonychians even though they may very well not be - was pretty cool, if I say so myself. It appeared here in August 2009.

In June 2010 I wrote about the paper that Don Henderson and I had just published on the possible swimming and floating behaviour of giraffes (Henderson & Naish 2010).
The completion in April 2011 of the vesper bat series was important, not only because it marked a significant personal achievement (that is, completion of an entire lengthy series) but also because the series may well represent the only comprehensive, plain-language review of this enormous and important bat group.
Tet Zoo has - fairly consistently - featured ground-breaking, revelatory review articles that just happened to published on April 1st. More notable April 1st articles includes the ones on rhinogradentians (part II here) (2007), amphisbaenians as mammal ancestors (2008), winged cat history (2010), and the discovery of Mokele-mbembe (2011).

I tried my hardest to cover such issues as amphibian diversity and conservation, those all-too-neglected Palaeozoic tetrapods, and tetrapod-relevant issues relating to environmental degradation and conservation. But, even after those several years and 860 separate blog entries, these subject areas and many others remain woefully under-represented.

One problem is that sexy, attention-grabbing topics like new dinosaurs, giraffe biology, cryptozoology and recently discovered mega-mammals have frequently diverted my attention and caused me to waste time [adjacent image shows a prasinoid monitor lizard - they're sexy, why didn't I ever write about them?]. I shouldn't have been writing about Montauk monsters or Mesozoic dinosaurs: small brown birds, rodents, tropical frogs and colubroid snakes - that's where the action is. My coverage of my own research output, publications and TV appearances also caused me to fail to make time for more important things that need better internet coverage. But then, I don't think you can blame me for this sort of thing. And Tet Zoo is 'only' a blog, existing in entirety to serve me and not anyone else anyway (no matter what they think).

I really tried so very hard to finish so many of the series I started: temnospondyls, toads, gekkotans, pouches and pockets in the heads and chests of mammals. But, dammit, I failed on all of those. If you think this is bad... well, what about the series where I wrote loads, yet never even got to post the first part? Yes, there is tons of un-published text sitting here on my hard-drive, and concerning such topics as the squirrels of the world, fossil proboscideans, Paleogene mammals, petrels and other seabirds, and so much more. Often, there just is literally not the time to fit blog-writing into life, not when you have a family, a modest social life, a need to work to pay the bills, and choose to prioritise academic output.

Why I love Tet Zoo

I've said a few times over the years that I write Tet Zoo for me. Evidently, I benefit very much from a large readership and from the informed and wonderful community of colleagues and commenters that now contribute to the site, but the most important reader is me. Even if my readership consisted of a lonely handful of friendly sympathisers, I'd still be doing it. So, the topics I've covered have had to be things that I've really wanted to cover; it's for this reason that Tet Zoo has veered around from one subject to another, often in whimsical and undirected fashion. The benefit of being interested in all tetrapods is that I can appeal to people interested in such diverse animals as Jurassic dinosaurs, modern birds, obscure tropical lizards and the anatomy of marine mammals. Stick around, and something you like will appear, I suppose. [Adjacent montage of model azhdarchid, shoebill and hypothetical big-brained theropod Nemoramjetia mostly irrelevant.]

It's by happy coincidence that many of those topics I've wanted to write about have been the ones that haven't had much of an internet presence already. Such animals as dibamids, didymoconids, borhyaenoids, amphiumas and giraffe-necked giant tortoises haven't been much covered outside of the specialised, technical literature. So you could, if you want to, think that Tet Zoo serves an important role in helping to disseminate information and awareness regarding such animals to a wider audience. I'm hardly the only one doing this, of course: lots of other excellent bloggers are also doing their bit to bring all kinds of animals, living and fossils, to better attention. But I hope people think that I've done more than my fair share.

I've worked hard to make Tet Zoo attractive in visual terms, taking time to find (and sometimes generate) relevant pictures [adjacent pic shows me as once depicted on a Christmas card, honest]. I've sometimes gotten* into trouble as a result, but mostly this has worked out. The significance that I place upon pictures relates mostly to my own immaturity. I'm bored to tears by large chunks of text and often can't bring myself to read articles by other people (especially online articles) if they aren't accompanied by images of some sort.

* Ha.

I have the impression that Tet Zoo ver 2 has become more picture-led over the years but I'm not entirely sure that's true: even those early articles of January 2007, for example, are quite well illustrated. I wish I'd been in the habit of posting pictures at larger sizes though. On that note, one annoying constraint of the ScienceBlogs platform is that images can only be posted at maximum column width - a mere c. 500 pixels. No doubt this has often annoyed readers who've wanted to see diagrams at larger size - well, sorry, I did the best I could.

I forget the point I wanted to make here. But, whatever, I hope that visiting Tet Zoo ver 2 has not only been informative and perhaps even important in terms of outreach and education, but also fun and easy on the eye.

Quit the rambling and get to the point - - why are we here, right now?

So, what's the point of all this navel-gazing? I normally do this sort of thing on Tet Zoo's birthday. Well, the reason we're here is that now, my friends, Tet Zoo ver 2 must come to an end. I'm not kidding - this really is it. The end. Yes, those four years of Tet Zoo ver 2 have been great fun. I wish to thank everyone who's visited, or - even better - has accompanied me on my academic journey across the tetrapod cladogram. I hope you've learnt from the site, and I hope you've enjoyed visiting. But it's time to say goodbye.

Goodbye Tet Zoo ver 2, you served us well.

Goodbye.

Buuuuut.... I mean, of course, that this is 'only' the end of Tet Zoo ver 2, not of Tet Zoo altogether. So, ladies and gentlemen, it's time to usher in the age of Tet Zoo ver 3. Take a deep breath, wipe the tears from your eyes, and click here.

Refs - -

Dalton, R. 2008. Fossil reptiles mired in controversy. Nature 451, 510

Henderson, D. M. & Naish, D. 2010. Predicting the buoyancy, equilibrium and potential swimming ability of giraffes by computational analysis. Journal of Theoretical Biology

Naish, D. 2008. Intelligent dinosaurs. Fortean Times 239, 52-53.

Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.

Witton, M. P. & Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3(5): e2271. doi:10.1371/journal.pone.0002271

tetrapodzoology Tue, 07/05/2011 - 02:16

Inside Nature's Giants: polar bear special

tetrapodzoology — Thu, 30 Jun 2011 07:20:24 +0000

Inside Nature's Giants: polar bear special

So sorry for the very short notice. The following airs here in the UK tonight (Thursday 30th June 2011), Channel 4. I look forward to it.

For the Tet Zoo articles on ING and related issues, see...

tetrapodzoology Thu, 06/30/2011 - 03:20

Geckos love Tet Zoo

tetrapodzoology — Wed, 29 Jun 2011 09:37:10 +0000

Geckos love Tet Zoo

If you didn't know, I've been away. The last four articles that have appeared here were all scheduled to publish in my absence. I've been in Romania and Hungary where I had a great time - saw lots of neat animals (fossil and living) and hung out with some neat people. I'll talk about some of this stuff in due course. For now, here's a really nice picture, kindly provided by artist-animator Ethan Kocak.

Ethan keeps and breeds geckos and, as you can see from this photo of one of Ethan's New Caledonian giant geckos Rhacodactylus leachianus henkeli, it seems that these lizards are big fans of at least one of my books (the hugely successful Tetrapod Zoology Book One). Thanks, Ethan, for the photo. If you're wondering why individuals of Rhacodactylus are so keen on Tet Zoo, it must be because they've read the extremely impressive and near-complete series of Tet Zoo gekkotan articles...

tetrapodzoology Wed, 06/29/2011 - 05:37

Hoopoes and woodhoopoes

tetrapodzoology — Mon, 27 Jun 2011 06:00:00 +0000

Hoopoes and woodhoopoes

Yet more from that book project (see the owl article for the back-story, and the hornbill article for another of the book's sections).

Hornbills, hoopoes and woodhoopoes are all similar in appearance and have been classified together in a group termed Bucerotes. Vague similarities with other long-billed, forest-dwelling birds (like woodpeckers, long-billed cuckoos and such passerines as tree-creepers) meant that early ornithologists were often confused about the affinities of these birds. By the late 1800s, however, most had realised that all three were close relatives, and that they were most likely close kin of kingfishers, bee-eaters and rollers. The group that includes kingfishers, bee-eaters, rollers, hornbills and hoopoes has been termed Coraciiformes; some recent phylogenies have found Coraciiformes of tradition to be paraphyletic to Piciformes (woodpeckers and kin) (e.g., Mayr et al. 2003, Cracraft et al. 2004, Ericson et al. 2006, Hackett et al. 2008). The resulting 'coraciiform' + piciform clade appears robust and has recently been named Picocoraciae (Mayr 2010).

Within Picocoraciae, a close link between hornbills, hoopoes and woodhoopoes is firmly established on the basis of anatomical and genetic evidence. All three groups share a list of features not seen in other birds, and have similar skulls, chest bones and leg bones.

Hoopoes and woodhoopoes are similar, slender-billed birds of Old World woodlands, forests and grasslands [adjacent image shows Green woodhoopoe Phoeniculus purpureus (also called the Purple or Red-billed woodhoopoe): photo by Axel BÃ¼hrmann, from wikipedia]. The Hoopoe Upupa epops [shown at top; photo by J. M. Garg, from wikipedia] is widespread, occurring across Europe, Africa including Madagascar, and Asia. These populations differ somewhat in size and colour and about ten subspecies have been named: some experts think that a second species (U. africana) should be recognised for African hoopoe populations. A large, flightless species (U. antaios) previously inhabited St Helena in the South Atlantic (Olson 1975).

Hoopoes are unmistakeable, combing a long, decurved bill with an erectile crest, pinkish or buff-coloured head and body plumage, and black-and-white striping on the wings and tail. They probe into bark, soil and leaf litter with the long bill, and feed mostly on insects and their larvae. Much of their foraging is done on the ground. Hoopoes are more flexible in terms of nesting behaviour than hornbills and woodhoopoes, and will use burrows, nest boxes and buildings as nest sites. The nest site soon becomes fouled with droppings and food fragments.

Woodhoopoes - some species of which are sometimes called scimitarbills - are restricted to Africa, though they also inhabited Europe during the Miocene (Ballman 1969). Between eight and ten species are known (ideas differ on which populations should be regarded as species: see Simmons et al. (2005) and Cunningham & Cherry (2005)). Most forage in the trees of woodland and grassland environments, but two are restricted to rainforests. Woodhoopoes are hoopoe-shaped, but differ from them in being crestless and in possessing dark, metallic plumage. Some have straight bills, while in others the bill is strongly curved. Several species have white patches on their wings and tails, and the White-headed woodhoopoe Phoeniculus bollei [shown here, painting by J. G. Keulemans] is particularly distinctive.

Woodhoopoes are more agile than hoopoes, and are experts at climbing up tree trunks and clambering about among branches. They even hang upside down on occasion, and often use their tail feathers as props in similar fashion to woodpeckers. When on the ground, woodhoopoes hop, whereas hoopoes walk.

One interesting detail of woodhoopoe biology is that the sexes often differ in bill length, with males having substantially longer, more curved bills (a male's bill can be more than one-third longer than a female's) [adjacent photo - showing bill dimorphism in Green woodhoopoe - from Andrew Radford's site]. Females forage on branches for small insects, while males probe into crevices for larger prey (Jamieson & Spencer 1996, Radford & du Plessis 2003). Sexual dimorphism in bill length and shape is fairly widespread in birds, and it means that the sexes avoid competing with one another by acting as separate 'ecological species' (see the article Sexual dimorphism in bird bills: commoner than we'd thought).

Like hornbills and hoopoes, woodhoopoes are cavity nesters. However, Green woodhoopoes at least cannot use cavities that are open to the elements and require cavities partially covered by bark or vegetation. These partially covered cavities are rare commodities, and are often taken over by bees, rodents and other animals. It also seems that woodhoopoes are sensitive to cool night-time temperatures and ordinarily cluster together under cover to stay warm at night. All of this means that they're constrained in terms of where they can live and breed (du Plessis 1992). [Image below shows Common scimitarbill Rhinopomastus cyanomelas by Steve Garvie, from wikipedia.]

Because woodhoopoes often choose roost or nest sites in weak, partially rotten wood, they are poorly protected from mammalian predators. Genets and cats take a heavy toll on woodhoopoe populations, and woodhoopoe mortality seems to be about twice as high as that of other small birds from the same habitats. Woodhoopoes are not completely defenceless though: female hoopoes and woodhoopoes can both produce a dark, foul-smelling oil when threatened on the nest, and can even spray it from their oil gland (located beneath the tail).

Woodhoopoe family life

Some woodhoopoe species are highly social birds that live in groups with a well-established dominance hierarchy. The Green woodhoopoe is a co-operative breeder, and as many as ten birds will work together with a mated pair to help raise their chicks (du Plessis 1991, du Plessis et al. 2007). As is typical among co-operative breeders, these helpers are often close relatives of the pair, typically being offspring from previous clutches. However, unrelated birds of the same sex may also form social groups, with the non-breeders being subordinate to the breeding, territory-holding birds. It seems that this behaviour is reciprocal, and that the roles are exchanged when the helpers become territory-holders themselves. The breeding behaviour of other woodhoopoe species is poorly known, so it is possible that co-operative breeding occurs in some of them as well.

All individuals of the social group help defend the breeding territory, but the subordinate birds actually seem to contribute more to territory defence than the breeding pair. Groups use 'vocal rallying' (or choruses) to advertise their occupation of a territory, and call for longer when they perceive that a neighbouring group consists of many individuals (Radford 2003). Males undergo a change in voice at sexual dimorphism (Radford 2004) and, because the composition of a group means that it has a distinct rallying sound compared to others, groups can identify other groups with ease. A group answers faster to an unfamiliar group, or to a trespassing familiar group, than to a familiar group in its expected location (Radford 2005).

And, just to remind you what this all would have looked like had the book worked out, here's the layout we planned...

For previous articles on members of Picocoraciae, see...

Refs - -

Ballman, P. 1969. Die VÃ¶gel aus der altburdigalen SpaltenfÃ¼llung von Wintershof (West) bei EichstÃ¤tt in Bayern. Zitteliana 1, 5-60.

Cracraft, J., Barker, F. K., Braun, M., Harshman, J., Dyke, G. J., Feinstein, J., Stanley, S., Cibois, A., Schikler, P., Beresford, P., GarcÃa-Moreno, J., Sorenson, M. D., Yuri, T. & Mindell, D. P. 2004. Phylogenetic relationships among modern birds (Neornithes): towards an avian tree of life. In Cracraft, J. and Donoghue, M. (eds), Assembling the Tree of Life. Oxford University Press (Oxford), pp. 468-489.

Cunningham, M. & Cherry, M. I. 2005. Seeing the woodhoope for the trees: a response to Simmons et al. (2005). Ibis 147, 225-227.

du Plessis, M. A. (1991). The role of helpers in feeding chicks in cooperatively breeding green (red-billed) woodhoopoes Behavioral Ecology and Sociobiology, 28 (4) DOI: 10.1007/BF00175102

- . 1992. Obligate cavity-roosting as a constraint on dispersal of Green (Red-billed) woodhoopoes: consequences for philopatry and the likelihood of inbreeding. Oecologia 90, 205-211.

- ., , Robert E Simmons, R. E. & Radford, A. N. 2007. Behavioural ecology of the Namibian violet woodhoopoe Phoeniculus damarensis. Ostrich 78, 1-5.

Ericson, P. G. P., Anderson, C. L., Britton, T., Elzanowski, A., Johansson, U. S., KÃ¤llersjÃ¶, M., Ohlson, J. I., Parsons, T. J., Zuccon, D. & Mayr, G. 2006. Diversification of Neoaves: integration of molecular sequence data and fossils. Biology Letters 2, 543-547.

Hackett, S. J., Kimball, R. T., Reddy, S., Bowie, R. C. K., Braun, E. L., Braun, M. J., Cjojnowski, J. L., Cox, W. A., Han, K.-L., Harshman, J., Huddleston, C. J., Marks, B., Miglia, K. J., Moore, W. S., Sheldon, F. H., Steadman, D. W., Witt, C. C. & Yuri, T. 2008. A phylogenomic study of birds reveals their evolutionary history. Science 320, 1763-1768.

Jamieson, I. G. & Spencer, H. G. 1996. The bill and foraging behaviour of the Huia (Heteralocha acutirostris): were they unique? Notornis 43, 14-18.

Mayr, G. 2010. Metaves, Mirandornithes, Strisores and other novelties - a critical review of the higher-level phylogeny of neornithine birds. Journal of Zoological and Systematic Evolutionary Research 49, 58-76.

- ., Manegold, A. & Johansson, U. S. 2003. Monophyletic groups within 'higher land birds' - comparison of morphological and molecular data. Journal of Zoological and Systematic Evolutionary Research 41, 233-248.

Olson, S. L. 1975. Paleornithology of St. Helena Island, South Atlantic Ocean. Smithsonian Contributions to Paleobiology 23, 1-48.

Radford, A. N. 2003. Territorial vocal rallying in the Green woodhoopoe: influence of rival group size and composition. Animal Behaviour 66, 1035-1044.

- . 2004. Voice breaking in males results in sexual dimorphism of Green woodhoopoe calls. Behaviour 141, 555-569.

- . 2005. Neighbour-stranger discrimination in the group-living green woodhoopoe. Animal Behaviour 70, 1227-1234.

- . & du Plessis, M. A. 2003. Bill dimorphism and foraging niche partitioning in the green woodhoopoe. Journal of Animal Ecology 72, 258-269.

Simmons, R. E., Du Plessis, M. A. & Hedderson, T. A. J. 2005. Seeing the woodhoopoe for the trees: should we abandon Namibia's Violet woodhoope Phoeniculus damarensis as a species? Ibis 147, 222-224.

tetrapodzoology Mon, 06/27/2011 - 02:00

Categories

Life Sciences

What does it feel like to get bitten by a ground hornbill, I hear you ask?

tetrapodzoology — Fri, 24 Jun 2011 06:10:00 +0000

What does it feel like to get bitten by a ground hornbill, I hear you ask?

Suppose you're interested in the anatomy and biology of ground hornbills. Now suppose that you get the chance to make physical contact with one of these awesome birds. Here, at last, is the opportunity to get bitten!! Surely you've always wanted to know what it feels like when a ground hornbill bites you. No? Ok, maybe it's just me. Anyway, the opportunity to get bitten by a ground hornbill presented itself to me a few weeks ago, so who was I to miss out?

As I can now confirm from personal experience, it turns out that ground hornbills don't bite hard enough to hurt. My impression is that the bird just wasn't able to exert enough force to, say, crush a large beetle or snail shell, let alone break the bones of a vertebrate prey animal. But, then, that isn't what these birds do anyway: they grab things with their bill tips, squeeze them, and shake them and/or beat them against objects or surfaces before they go limp enough to be thrown to the throat and swallowed (Burton 1984, Baussart & Bels 2010).

I find this interesting because a criticism that's been levelled (informally) at the 'terrestrial stalker' models as goes azhdarchid pterosaurs (Witton & Naish 2008) is that they lack evidence for a strong bite (and that strong bite, so it's been inferred, is required, so it's been suggested, for the terrestrial stalking hypothesis to work). Well, so far as I can tell, ground hornbills - the best extant analogues for azhdarchids, according to Witton & Naish (2008) - don't really have a strong bite either. Incidentally, one more thought on that Witton & Naish (2008) while I'm here. The metrics associated with the paper show that it's been viewed more than 16600 times, and the pdf itself has been downloaded more than 1700 times [graph below, generated by PLoS ONE metrics, shows steady and apparently continuous increase in viewings of our article. Interesting]. The following occurred to me recently: does this mean that it can perhaps be regarded as the most-read pterosaur article of all time? I don't know, but it's certainly possible. Anyway...

This is, of course, all just a bit of fun (and it all started out as an excuse to use the photos you see here): it doesn't really tell us anything about the bite strength of ground hornbills, or about the strengths and limitations of hornbill jaws or skulls in general. After all, we don't know that the bird was biting especially hard (it might, for all we know, have been being gentle with me), and we don't know how much pressure needs to be exerted on my fingers before that amount of pressure is actually "a lot" (whatever that is). And maybe human fingers (or my fingers in particular) are poor at gauging pressure - I certainly seem to be poor at gauging everything else. So, maybe the bite of that hornbill was, actually, really strong.

Want to compare my idiosyncratic and potentially grossly inaccurate whimsical musings with some hard science? Well, tough. So far as I can tell, there's no empirical published work of any sort on hornbill bite strength. Indeed, there's little on birds in general: a couple of studies have been published on finches (van der Meij 2004, van der Meij & Bout 2004, 2006) and Degrange et al. (2010) recently reported data from seriemas and eagles, and published an estimate for the large phorusrhacid Andalgalornis [one of their figures is shown here: see their paper for the full story]. Robust-billed finches like the Hawfinch Coccothraustes coccothraustes bite at somewhere between 310 and 700 N (this was previously discussed in the article Coccothraustes: most bizarre of finches), seriemas and eagles bite at about 50 N, and the suggested bite force for Andalgalornis is 133 N. This is low for a predator of its size (c. 40 kg): mammals with that sort of bite force include otters, jaguarundis and grey foxes. But, then, I wouldn't much like to be bitten hard by an otter or jaguarundi. British wildlife TV presenter Terry Nutkins lost two of his fingers to a pet otter he once kept.

I've now been bitten (sometimes by design, sometimes not) by a reasonable variety of birds, the majority of which are of course too small and too weak-jawed to hurt the human they're biting. Owl bites don't hurt (as discussed recently, their power is in their feet), but I'm not sure about falcons, hawks or eagles (please do say if you have direct experience). But even really big birds - waterfowl and ratites, for example - have weak bites for their size: ratites in particular have flimsy skulls and small jaw muscles, and power-biting just isn't something that you need to do when you make a living from picking at shoots and seeds and grabbing insects. Swans and geese (I've now been bitten by many) can't really hurt by biting alone, but some of them have a nasty habit of 'chattering' their jaws on your fingers. I don't know why. A Chinese swan-goose Anser cygnoides did this to me and broke through the skin, causing tiny, pin-prick like marks in my skin thanks to the serrated edges on its rhamphothecae [the adjacent photos show Mute swan Cygnus olor, Greater rhea Rhea americana, Greylag Anser anser, and my hand].

It's a different ballgame when we start thinking about parrots, and let's just say that I don't much want to get bitten by one. A cockatoo did once bite right through my jacket purely for its own entertainment, and a Kea Nestor notabilis bit through my camera strap because I was stupid enough to let it. Then again, having a scar caused by parrot bite might be pretty cool. A lot of people who do hands-on work with animals have neat wounds: I always like that scene in Jaws where Hooper and Quint are comparing their healed shark injuries. Well, that's just like real life.

For previous articles on bird feeding behaviour, biting and such, see...

Coccothraustes: most bizarre of finches
Terrestrial stalking azhdarchids, the paper
At the 56th SVPCA - hello Dublin! (discusses feeding behaviour in waterbirds)
B. rex!
When tapirs don't attack, and when Meller's duck does
Condors and vultures: their postures, their 'bald heads' and their sheer ecological importance

Refs - -

Baussart, S. & Bels, V. 2010. Tropical hornbills (Aceros cassidix, Aceros undulatus, and Buceros hydrocorax) use ballistic transport to feed with their large beaks. Journal of Experimental Zoology Part A: Ecological Genetics and Physiology 313A, 72-83.

Burton, P. J. K. 1984. Anatomy and evolution of the feeding apparatus in the avian orders Coraciiformes and Piciformes. Bulletin of the British Museum of Natural History (Zoology) 47, 331-443.

Degrange, F. J., Tambussi, C. P., Moreno, K., Witmer, L. M. & Wroe, S. 2010. Mechanical analysis of feeding behavior in the extinct "terror bird" Andalgalornis steulleti (Gruiformes: Phorusrhacidae). PLoS ONE 5 (8): e11856. doi:10.1371/journal.pone.0011856

van der Meij, M. A. 2004. A tough nut to crack: adaptations to seed cracking in finches. Unpublished thesis, Leiden University.

van der Meij, M., & Bout, R. G. (2004). Scaling of jaw muscle size and maximal bite force in finches Journal of Experimental Biology, 207 (16), 2745-2753 DOI: 10.1242/jeb.01091

- . & Bout, R. G. 2006. Seed husking time and maximal bite forces in finches. The Journal of Experimental Biology 209, 3329-3335.

Witton, M. P. & Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3 (5): e2271. doi:10.1371/journal.pone.0002271

tetrapodzoology Fri, 06/24/2011 - 02:10

An introduction to hornbills

tetrapodzoology — Wed, 22 Jun 2011 06:10:00 +0000

An introduction to hornbills

More from the bird book. For the back-story, see the previous owls article.

Hornbills are among the most distinctive and spectacular of Old World tropical birds. Often flaunting bright colours and sometimes reaching huge sizes (the largest species have wingspans of 1.8 m), they're well known for their enormous, curved bills and large bony crests. [Image above shows Great Indian hornbill skeleton Buceros bicornis (l) and male Wreathed hornbill Rhyticeros undulatus (r) (by Blijdorp, from wikipedia). Hornbills like the Great Indian hornbill are forest-dwelling omnivores that eat fruit as well as small animals. In the Great Indian hornbill, the casque has a flattened upper surface and is sometimes used in head-butting. This is a long-lived bird, reaching its sixth decade in cases. Image below shows two Rhinoceros hornbills B. rhinoceros - by JP Bennett, from wikipedia - at top, and Knobbed hornbill or Sulawesi wreathed hornbill R. cassidix - by Tobias, from wikipedia - below. The Rhinoceros hornbill is a giant, forest-dwelling species of south-eastern Asia. Its horn-like casque is larger and more prominent in males. The red colour on the casque is derived from the oil gland under the tail.]

Life in tropical forests

Spectacular colours, gigantic bills and head crests, and remarkable pieces of behaviour make hornbills among the most obvious birds of the African and Asian tropics. People have long revered these birds and, in some cultures, their images are incorporated into art, heraldry and architecture. What appear to be the most archaic of hornbills - the ground hornbills and the grassland-dwelling Tockus hornbills - are African. Early in their evolution (apparently during the Eocene*), hornbills invaded Asia, and it is here that many kinds of tropical, forest-dwelling hornbill evolved (Viseshakul et al. 2011). One Asian lineage then appears to have re-invaded Africa (Kemp 1995, Kinnaird & O'Brien 2007). [Helmeted hornbill Rhinoplax vigil shown below; by Doug Janson, from wikipedia.]

* Molecular clocks and fossil data from related bird groups show that hornbills had certainly appeared, and apparently undergone much of their initial diversification, during the Eocene. Yet their fossil record hardly reflects this. The alleged Eocene hornbill Geiseloceros robustus is not a hornbill at all, and undoubted hornbills are rare fossils in Miocene and post-Miocene strata.

The bill is straight in some species, but is more typically curved along its length. Its superficial resemblance to a cow's horn explains the group's name. This massive bill is a versatile tool, allowing different species to exploit tropical forest canopies, dry woodlands and even grasslands and semi-deserts. The majority of species use it to pick fruit and to grab small animals while foraging in trees, but some use it as a hammer to excavate bark or soil when searching for insects. Ground hornbills are able to subdue such large prey as snakes and rabbits. Their size, large appetites and ability to range far and wide in search of fruit make hornbills important seed dispersers.

In many species, the tips of the upper and lower jaws are the only parts of the jaws that are in full contact. The birds use these to perform precise grasping actions, and they also manipulate objects before swallowing. Hornbills have a particularly short tongue that doesn't play a role in the manipulation of food items: once an object is positioned as desired at the jaw tips, it is thrown backwards into the throat. This technique has been referred to as 'ballistic transport' (Baussart & Bels 2010) (the same feeding technique has been convergently evolved in toucans: this is all rather different from the 'catch and throw' technique practised by ratites and some other birds) [figure below, from Baussart & Bels (2010), shows food transport as used by three different hornbill species. The object follows a ballistic curve as it's thrown from the jaw tips to the throat]. It seems logical to assume that hornbills can see their own bill tip, and studies of their visual fields show that sophisticated binocular vision allows this (Martin & Coetzee 2004). This is unusual among birds, as the bill tip is normally outside the bird's field of vision. The hornbill palate is roofed with bone and is hence reinforced and strong compared to that of most other birds (Burton 1984). After grabbing a prey animal, a hornbill will often beat it to death against a perch. The long, thick eyelashes of some species help shield the eyes from sunlight.

Like most forest-dwelling birds, hornbills have broad, rounded wings. They are very noisy in flight, and the whooshing sound of their wing feathers means that they are sometimes heard before they are seen.

Hornbill breeding biology is remarkable. Most species are monogamous and defend territories, but co-operative breeding is present in others. When the time comes to nest, the pair selects a cavity in a tree or rock face. Using mud and droppings, the female walls herself into the chamber. A slit remains the only point of contact with the outside world, and the female and chicks then rely on the male to collect and deliver food. In some species, the female remains in the chamber for as long as five months.

Hard heads and hollow crests

Running along the top of the hornbill beak and often extending on to the skull roof is a hollow bony ridge or crest, sheathed in protective keratin. This is properly termed the casque. In the most primitive hornbills, the casque is merely a low ridge, and it is thought that its initial development was related to the addition of strength to the bill. More advanced hornbills have enlarged the casque and possess a mass of supporting bony struts inside it.

One of the primary roles of the casque is as a social signaller. It only develops once the bird reaches sexual maturity, and is typically larger in males. In the Black-casqued hornbill Ceratogymna atrata the casque works as a resonating chamber (Alexander et al. 1994). Perhaps the most remarkable casque is the one possessed by the Helmeted hornbill. Composed of a solid block of bone, it accounts for about 11% of the bird's weight [world-famous photo of sectioned R. vigil casque shown here by Matt Wedel]. Perhaps, by adding weight to the bill, it helps the bird use its bill as a hammer. More remarkable is the fact that Helmeted hornbills use their crests in aerial jousting: males engage in prolonged, noisy head-butting matches while in flight (Kinnaird et al. 2003).

The ground hornbills

By far the least typical of hornbills are the two ground hornbills of southern and eastern Africa. These large, predominantly black hornbills have bright red or blue skin on their faces and necks. They can reach 4 kg and may have a wingspan of about 2 m. One species - the Southern ground hornbill Bucorvus leadbeateri virtually lacks a casque while the other - the Northern or Abyssinian ground hornbill B. abyssinicus - has a tall, short casque. Today, ground hornbills are restricted to sub-Saharan Africa, but fossils show that they once inhabited northern Africa and eastern Europe (Boev & Kovachev 2007). They appear to be the sister-group to all the other hornbills, and are so distinct from all the others that some experts regard them as belonging to their own group termed Bucorvidae.

Hornbills typically have short legs and toes, and when moving on the ground they hop. Ground hornbills are terrestrial predators, and their anatomy is somewhat different. Their legs are long, their short-toed feet are heavily padded on their undersides, and they walk with a striding gait. It's said that they can run at speeds approaching 30 km/h. They are also capable fliers, however, and fly up into trees to roost.

Ground hornbills also differ from other hornbills in that the female does not become walled into the nest chamber. Between one and three eggs are laid, but it seems that they never succeed in raising more than a single chick.

The great classic modern source on hornbills is Alan Kemp's excellent 1995 book The Hornbills, part of the 'Bird Families of the World' series published by Oxford University Press. As is true of so many of those big, monographic books (and echoing statements I've made before), it's essentially out of reach to a huge sector of the community because of its price: it normally sells for about Â£150 (about $US243 or EUR170) these days. Surely by now someone has thought to turn these books into pdfs? Ahem.

If you're a regular reader you'll know that this is hardly the first time hornbills have been featured on Tet Zoo. Please also see...

You're not a proto-phorusrhacid, but you're still a cariamaen, and that's alright with me (ode to the Ameghinornithidae) (discusses alleged fossil hornbill Geiseloceros robustus)
The other ground hornbill
Ground hornbills: savannah-dwelling, avian pseudo-hominids

Refs - -

Alexander, G. D., Houston, D. C. & Campbell, M. 1994. A possible acoustic function for the casque structure in hornbills (Bucerotidae). Journal of Zoology 233, 57-67.

Boev, Z. & Kovachev, D. 2007. Euroceros bulgaricus gen. nov., sp. nov. from Hadzhidimovo (SW Bulgaria) (Late Miocene) - the first European record of hornbills (Aves: Coraciiformes). Geobios 40, 39-49.

Burton, P. J. K. 1984. Anatomy and evolution of the feeding apparatus in the avian orders Coraciiformes and Piciformes. Bulletin of the British Museum of Natural History (Zoology) 47, 331-443.

Kemp, A. C. 1995. The Hornbills. Oxford University Press, Oxford.

Kinnaird, M. F., Hadiprakarsa, Y.-Y. & Thiensongrusamee, P. 2003. Aerial jousting by Helmeted hornbills Rhinoplax vigil: observations from Indonesia and Thailand. Ibis 145, 506-508.

- . & O'Brien, T. G. 2007. The Ecology and Conservation of Asian Hornbills: Farmers of the Forest. University of Chicago Press, Chicago.

Martin, G. R. & Coetzee, H. C. 2004. Visual fields in hornbills: precision-grasping and sunshades. Ibis 146, 18-26.

Viseshakul N, Charoennitikul W, Kitamura S, Kemp A, Thong-Aree S, Surapunpitak Y, Poonswad P, & Ponglikitmongkol M (2011). A phylogeny of frugivorous hornbills linked to the evolution of Indian plants within Asian rainforests. Journal of evolutionary biology, 24 (7), 1533-1545 PMID: 21545425

tetrapodzoology Wed, 06/22/2011 - 02:10

Categories

Life Sciences

When books die. And owls. I don't mean "when owls die"... I just mean: owls. As in: this article is mostly about owls.

tetrapodzoology — Mon, 20 Jun 2011 06:35:00 +0000

When books die. And owls. I don't mean "when owls die"... I just mean: owls. As in: this article is mostly about owls.

There's something they don't tell you about freelance writing. It's about all the fails: the many, many projects that get pitched, worked on and made into proper presentations that then get sent to book fairs, interested companies and so on, but ultimately explode on the launch pad, or die a slow, lingering death. I don't know if it's that I'm especially unlucky, or if it's that I've pitched an unusually high number of books, or if it's that I've genuinely worked on a high number of projects that were never destined to succeed but, whatever, I've now worked on loads of failed book projects. It's not all bad, by the way - you still get paid for the time and work you've put in.

Anyway, the reason we're here is that one of those (so far) unsuccessful book projects is a big one on the evolutionary history and diversity of birds. To give you some idea how far down the line this project went, check out the various screen captures. I can't mention company names or whatever, but things on this one have definitely failed and I'm still interested in seeing the project through to publication (and, no, I am not putting the book out there and then trying to sell it - I have learnt from bitter, bitter, bitter experience that this idea just doesn't work out, at least not without starving and losing your home through total loss of income). If you can help, or are interested, you know where to find me.

Long-time readers will know that, thanks to various other failed book projects, I have tons of un-used text sitting around on all manner of zoological subjects. When time and inclination allows, I sometimes update and recycle bits of said text for Tet Zoo. As you read this, I'm away from my desk and out in the field, and as I didn't have time to generate much novel Tet Zoo content, I decided on a whim to recycle stuff from the bird book. Given that I wrote briefly about owls the other day, I decided to use the owl text (updated a little, and with references). Enjoy.

Introducing owls

Few groups of birds are as strongly associated with mythology, legend and superstition as the mostly nocturnal, predatory owls, properly called the strigiforms. Owls are well known for their exceptional eyesight and hearing, and for being equipped with a unique plumage that allows near-silent flight. Although owls as a group exhibit relatively little variation in shape or behaviour, the approximately 225 living species have adapted to virtually every conceivable habitat, from temperate woodlands and tropical forests to tundras, deserts, grasslands, and marshes. There are some excellent books on owl diversity: my three favourites are Wink et al.'s prohibitively expensive Owls of the World (second edition), John Burton's 1973, err, Owls of the World and Michael Everett's 1977 A Natural History of Owls.

A number of specializations seen throughout the body make owls among the most distinctive of birds. They combine a peculiar skull and facial anatomy with extraordinary eyes and ears, unusual feathers, and highly modified legs and feet. Their sensory abilities are phenomenal. Their enormous eyes are directed forward and a substantial part of their field of vision - corresponding to 50-70Â° - overlaps, enabling excellent depth perception. The exceptional ability to rotate the head is well known and improves an owl's ability to locate and pinpoint prey.

Owl eyeballs are tubular rather than spherical, and the ring of bones embedded within the eyeball - the sclerotic ring - is shaped like a turret and is immovably fixed to the edges of the eye socket. This tubular shape means that both the cornea and lens can be as big as possible relative to the retina, the light-sensitive region at the back of the eye. The owl retina is proportionally large and covered with a particularly high number of light-sensitive cells (as many as 56,000 per square mm in the Tawny owl Strix aluco).

Owls have a large number of feathers for their size (10,000 in the Long-eared owl Asio otus), and their feathers are also soft and downy compared to those of other birds. Soft fringes that run along the rear edges of the wing feathers enable near-silent flight: these should be visible in the photos below [the bottom one is by Kersti and is from wikipedia].

A disk of stiff feathers - known as the facial disk - is thought to help channel sounds towards the enormous, slit-shaped ear openings, in much the same way as the ear flaps of mammals help to 'collect' sound.

Asymmetrical ears

Owl ears are comparatively huge (though hidden by feathering) and unique in often being asymmetrically positioned: one is higher up on the side of the head than the other. In some owls, such as eagle owls and the Strix wood owls, it's the positions of the fleshy, external parts of the ears that are asymmetrical. In others, such as some Asio and Pseudoscops species, the external parts of the ears are asymmetrical in shape, though not in position, while in others, such as the Tawny owl, it's the skin folds around the external ears that are asymmetrical (Norberg 1977). In yet others, including the Great grey owl Strix nebulosa and Tengmalm's owl Aegolius funereus, the bony surroundings of the ears themselves are asymmetrical [see Tengmalm's owl skull shown below, from Norberg (2002)]. Some owls lack ear asymmetry and have normal, symmetrical ears (Norberg 1977). [Adjacent diagrams, from Norberg (2002), show how peculiar owl ears look when you move the feathers and both the preaural and postaural flaps. Yes, owls have fleshy flaps around their ear openings.]

Because the asymmetrical owls differ so much in their anatomy, and because they're not all close relatives, it appears that ear asymmetry has evolved on as many as seven separate occasions within owls (Norberg 2002). This is extraordinary given that asymmetrical ears are not present in any other group of birds so far as we know (though they were apparently present in troodontids).

It seems that asymmetrical ears allow an improved ability to pinpoint the sources of sounds. Some owls have become such masters at locating the distance to and elevation of any sound that they can even capture prey in total darkness.

Ear tufts - nothing to do with the real ears - have evolved repeatedly among owls. Their function is uncertain. While they might help break up the owl's outline and hence contribute to camouflage, they also seem to function in communication, and an owl's moods and intentions can often be predicted by the disposition of its tufts (for previous discussion of this topic, see the article Why do some owls have ear tufts?).

Two kinds of owl

Living owls can be divided into two groups: barn owls (Tytonidae) and the typical owls, also known as the true or strigid owls (Strigidae). Various efforts to resolve owl phylogeny have been published, mostly using molecular techniques (Wink & Heidrich 1999, Wink et al. 2004, 2008) (a phylogenetic study of owls based on morphological characters - a 1967 PhD project produced by N. L. Ford - has often been mentioned in the literature but remains unpublished).

Barn owls have longer, narrower skulls and longer legs than strigid owls; the claw on their third toe is comblike and functions in grooming and their facial disk is heart-shaped. There are approximately 15 barn owl species, though several others from the Caribbean and Mediterranean (some of which were much larger than the living kinds) became extinct in recent centuries. The best-known barn owl - the Common barn owl Tyto alba [shown here, image by Luc Viatour, from wikipedia] - is the most widespread owl species and one of the most widely distributed of all birds: it inhabits Europe, Africa, tropical Asia, Australasia, and the Americas.

Strigids have mostly rounded facial disks (nicely shown here in a captive Great grey owl) and broader skulls than barn owls. This is the most diverse owl clade: it includes the Australasian boobooks, hawk-owls, and laughing owls, the little owls, pygmy owls and their relatives, the small, cryptic scops and screech owls, the tropical and temperate spectacled owls, eared owls and wood owls, and the large eagle owls and their relatives.

The smallest strigids (there are several contenders for this title, with the best known being the Elf owl Micrathene whitneyi of the United States and Mexico) weigh less than 50 g and are about 12 cm long. In contrast, the largest (the Eurasian eagle owl Bubo bubo) reaches 70 cm in length, 4 kg in mass, and has a wingspan of 1.5 m.

Death by owl

Unlike hawks and falcons, owls do not kill with their hooked bills but typically rely on their very powerful, large-clawed feet. Owl toes are shorter and more robust than those of most other predatory birds, and their talons are all similar in length (Shufeldt 1900, Fowler et al. 2009) [adjacent image, from Shufeldt (1900), shows pedes of Tyto (l) and Bubo (r)]. The fourth toe can be directed backward so that both digits I and IV can oppose II and III: this type of foot is known as facultatively zygodactyl or semizygodactyl. Owls also have a relatively short, stout tarsometatarsus, and special bones called sesamoids help improve their ability to exert force through their toes and to resist stresses in the bones and muscles. These features mean that owls have a greater grip strength compared to other birds. After grabbing a prey animal, they squeeze it to death (Fowler et al. 2009). The prey animal is then usually swallowed whole, and the less digestible parts - such as fur, feathers, wing cases and bones - are later ejected from the mouth as sausage-shaped pellets. One or two pellets are usually produced within each 24-hour period.

The majority of owls prey on small mammals, but small birds, large insects, frogs, and earthworms are also common prey. Large species (like some of the eagle owls) may kill hares, hawks, falcons, and other owls, and eagle owls may even have a significant impact on populations of other predatory birds. Some owl species prey on bats, frogs, crabs, and fish. Owls are not limited to nocturnal hunting. Many species hunt either during the day or night, while others - a good example is the Hawk owl Surnia ulula of the Northern Hemisphere - mostly hunt in daylight.

Diverse lifestyles

In keeping with their favored woodland or forest habitat, owls frequently have barred or spotted plumage and most are patterned in various shades of brown. Nocturnal owls usually spend the daytime roosting out of sight, hidden close to tree trunks and in shade. They need to be cryptically coloured to avoid predators, but also to hide from small birds; on finding roosting owls, these will mob them and thereby reveal the predator's location to other animals. Some owl species have eyelike markings on the backs of their heads: these may help intimidate would-be attackers or mobbers.

Owls are not all woodland birds. Members of several lineages have adapted to life in open habitats. Deserts are inhabited by some eagle owls and by Elf owls. The widespread Short-eared owl Asio flammeus - found across Eurasia and the Americas - is a well known denizen of treeless moors and grasslands. The Burrowing owl Athene cunicularia of North, Central, and South America is a strongly terrestrial species that frequents grasslands and both roosts and nests in holes in the ground. One of the most distinctive open-habitat owls is the striking Snowy owl Bubo scandiacus [shown here] of the Northern Hemisphere. Genetic studies have shown that this large predator of lemmings and other mammals is a specialized member of the eagle owl lineage. Not only has it evolved a distinctive white plumage (flecked with black spots in the female), it has also strongly reduced the size of its ear tufts.

Owls are, quite rightly, generally assumed to be predators of terrestrial prey. However, owls belonging to two lineages have become specialized aquatic feeders. As suggested by their name, these fishing owls - the Asian Ketupa species and African Scotopelia species - either gaff prey from the water surface while in flight or wade into shallow water to seize their prey.

Unlike other strigid owls, fishing owls have unfeathered feet. Sharp spicules on the undersides of their toes help them to hold fish. Their facial disks are poorly developed. The need to have silent flight is no longer a concern, so their feathers lack the special fringes that provide other owls with such quiet wings. Unlike most other owls, fishing owls will sometimes feed on carrion.

All fishing owls are closely related to eagle owls (the Bubo species), and debate continues as to whether they should be included within Bubo (Wink & Heidrich 1999, Wink et al. 2004, 2008) or kept separate (at his bird taxonomy site, John Boyd suggests that it might prove most useful to recognise four clades within the eagle owl-fishing owl clade: Bubo sensu stricto, Nyctaetus, Scotopelia and Ketupa) [Adjacent image shows Greyish eagle owl B. cinerascens]. The Asian fishing owls look very Bubo-like while Scotopelia has a characteristic shaggy plumage, lacks ear tufts, and hence looks rather different. These differences imply that the similarities present between the two fishing owl evolved independently.

The fossil record

Owls have a good fossil record: as shown by the graph below - from Kurochkin & Dyke (2011) - the rate of discovery of new taxa increased markedly during the 1970s and 80s but slowed down round about 2000. This unusually good fossil record is partly due to the fact that owls often use caves as roost sites, but it's also explained by the fact that owl bones are particularly distinctive when compared with those of other birds. The oldest fossil owls are from the Paleocene, and a large number of archaic owls are known from the Eocene and Oligocene of the Northern Hemisphere (Mayr 2009). Some of these fossil owls are superficially similar to barn owls and have sometimes been regarded as ancient members of this group. However, it's possible that the features resulting in these suggestions are merely primitive characteristics that were widespread across all early owls but became lost or modified by strigids.

Modern owl lineages were definitely in existence by the Miocene. A number of fossil owls were particularly remarkable. During the Pleistocene, the Caribbean was home to several very large owls that had relatively stout legs. The largest of these - Ornimegalonyx - apparently had a standing height of more than a metre and may have had reduced flight abilities [sadly, there weren't 6-foot-tall Cretaceous super-owls, like the one shown here. See Myth of the six-foot super-owl]. Until recently, Hawaii was inhabited by the peculiar Grallistrix species, sometimes called the stilt-owls. These had particularly long legs and seem to have been dedicated predators of small birds.

For previous articles on owls, please see...

Refs - -

Fowler, D. W., Freedman, E. A. & Scannella, J. B. 2009. Predatory functional morphology in raptors: interdigital variation in talon size is related to prey restraint and immobilisation technique. PLoS ONE 4(11): e7999. doi:10.1371/journal.pone.0007999

Kurochkin, E. N. & Dyke, G. J. 2011. The first fossil owls (Aves: Strigiformes) from the Paleogene of Asia and a review of the fossil record of Strigiformes. Paleontological Journal 45, 445-458.

Mayr, G. 2009. Paleogene Fossil Birds. Berlin: Springer.

Norberg, R. (1977). Occurrence and Independent Evolution of Bilateral Ear Asymmetry in Owls and Implications on Owl Taxonomy Philosophical Transactions of the Royal Society B: Biological Sciences, 280 (973), 375-408 DOI: 10.1098/rstb.1977.0116

- . 2002. Independent evolution of outer ear asymmetry among give owl lineages; morphology, function and selection. In Newton, I., Kavanagh, R., Olsen, J. & Taylor, I (eds.) Ecology and Conservation of Owls: Proceedings of the Owls 2000 Conference. CSIRO Publishing (Collingwood, Victoria, Aus.), pp. 329-342.

Shufeldt, R. W. 1900. On the osteology of the Striges. Proceedings of the American Philosophical Society 39, 665-722.

Wink, M. & Heidrich, P. 1999. Molecular evolution and systematics of the owls (Strigiformes). In KÃ¶nig, C. Weick, F. & & Becking, J.-H. (eds) Owls, a Guide to Owls of the World. Pica Press, Mountfield (E. Sussex, UK), pp. 39-57.

- ., Heidrich, P., Sauer-GÃ¼rth, H., Elsayed, A.-A. & Gonzalez, J. 2008. Molecular phylogeny and systematics of owls (Strigiformes). In KÃ¶nig, C. & Weick, F. (eds) Owls of the World (second edition). Christopher Helm (London), pp 42-63.

- ., Sauer-GÃ¼rth, H. & Fuchs, M. 2004. Phylogenetic relationships in owls based on nucleotide sequences of mitochondrial and nuclear marker genes. In Chancellor, R. D. & Meyburg, B.-U. (eds) Raptors Worldwide. WWGB/MME, pp. 517-526.

tetrapodzoology Mon, 06/20/2011 - 02:35

Categories

Life Sciences

The bearded pigs

tetrapodzoology — Sun, 19 Jun 2011 04:55:39 +0000

The bearded pigs

One of the most remarkable pigs has to be the Bornean bearded pig Sus barbatus, one of two currently recognised bearded pig species. The other is the much smaller, shorter-faced Palawan bearded pig S. ahoenobarbus of the Philippines: genetic work suggests that S. ahoenobarbus is not a close relative of S. barbatus, but actually closer to the Celebes warty pig S. celebensis and other Philippines pigs (Lucchini et al. 2005). S. barbatus occurs on Sumatra, Bangka, the Riau archipelago and the Malay Peninsula as well as Borneo. There are two subspecies: S. b. barbatus has long cheek beards while S. b. oi has more wiry-looking snout hair. Molecular work confuses the distinction between these two forms, since Sumatran populations supposed to belong to S. b. oi are actually closer to the nominate Bornean population that to Malaysian populations of S. b. oi (Lucchini et al. 2005, p. 33).

One hypothesis for the evolution of Sus proposes that the bearded pigs and the Java warty pig S. verrucosus are the sister-group to a clade that includes the Wild boar S. scrofa and Celebes warty pig S. celebensis. Supposedly, members of the bearded pig lineage can be distinguished from members of the wild boar lineage by their especially elongate snout and 'saw-edged' fronto-nasal suture (Groves 1983, 1997). Conspicuous differences in size between the bearded pig populations of Sumatra, Borneo and elsewhere meant that particularly big individuals collected on Borneo were initially thought to represent an additional species; S. gargantua Miller, 1906.

Comparatively little is known about the ecology and behaviour of bearded pigs. They're reportedly migratory across part of their range, moving back and forth between areas during the year, and sometimes gathering in huge herds of hundreds of animals (Groves 1981). I'd like to know more about what they do with all that crazy snout hair, but this subject doesn't seem to have been much explored in the literature. It seems to be sexually dimorphic, with males having hairier snouts and cheeks.

These photos were taken at Berlin Zoo by Markus BÃ¼hler. Berlin Zoo includes quite a few neat bits of signage and artwork: the sign below does a nice job of illustrating some of the diversity present in the wild pigs of south-east Asia. As you can see, this diversity is pretty impressive. The taxonomy of these pigs has been much discussed and debated and how many of the various forms are regarded as 'subspecies' or 'species' remains the topic of disagreement (see Groves 1997, 2001). It's an important issue, since many of these pigs are threatened and of great conservation interest.

For previous Tet Zoo articles on pigs, see...

Ref - -

Groves, C. P. 1981. Ancestors for the Pigs: Taxonomy and Phylogeny of the Genus Sus. Technical Bulletin 3, Department of Prehistory, Research School of Pacific Studies, Australian National University, pp. 96.

- . 1997. Taxonomy of wild pigs (Sus) of the Philippines. Zoological Journal of the Linnean Society 120, 163-191.

- . 2001. Taxonomy of wild pigs of southeast Asia. Asian Wild Pigs News 1 (1), 3-4.

Lucchini, V., Meijaard, E., Diong, C. H., Groves, C. P., & Randi, E. 2005.Journal of Zoology, 266, 25-35

Lucchini, V., Meijaard, E., Diong, C. H., Groves, C. P. & Randi, E. 2005. New phylogenetic perspectives among species of South-east Asian wild pig (Sus sp.) based on mtDNA sequences and morphometric data. Journal of Zoology 266, 25-35. [Have added the same ref twice as cannot get research blogging to behave itself.]

tetrapodzoology Sun, 06/19/2011 - 00:55

Giant owls vs solenodons

tetrapodzoology — Wed, 15 Jun 2011 06:36:00 +0000

Giant owls vs solenodons

Here's something you don't see very often...

This illustration (by Peter Trusler) shows the large Pleistocene Cuban owl Ornimegalonyx oteroi battling with a solenodon. Ornimegalonyx has been mentioned here a few times before (use the search bar), but nothing substantive, sorry. Most sources mention O. oteroi as if it's the only named species of Ornimegalonyx. Actually, Arredondo (1982) named three additional ones: O. minor, O. gigas and O. acevedoi. And, by the way, the Ornimegalonyx owls weren't the only big owls on Pleistocene Cuba - there was also a particularly big eagle owl (Bubo osvaldoi Arredondo & Olson, 1994) and the two large barn owls Tyto noeli Arredondo, 1972 and T. riveroi Arredondo, 1972 (Arredondo & Olson 1994). There were a diversity of smaller owls too.

Typical factoids usually given about O. oteroi are that its remains were initially misidentified as those of a phorusrhacid (see Brodkorb (1961)), that it was over a metre tall, that it had notably robust hindlimbs, and that it was probably flightless and cursorial.

"Over a metre" might be too much, but might not: it comes from the 1.1 m height estimated by Arredondo (1976). The adjacent illustration, found online (~~sorry, I can't find the artist's name~~ owl - but not human soldier - by Satoshi Kawasaki), shows how insanely big such an owl would really have been. What.. really? Wow. Like many people, my first encounter with this animal was actually with a very inaccurate and rather strange reconstruction published on a Cuban stamp in 1982 (see below). Anyway, the claim of flightlessness might not be correct: Mike Habib, some-time frequenter of Tet Zoo, has mentioned in-progress work on the flight abilities of this and other giant owls, and Storrs Olson - often quoted as saying that these owls had a reduced flight ability - is also on record as saying "I rather imagine that these birds could fly or glide to some extent" (Olson 1978, p. 106). Olson even noted the possibility that "it may have taken very little flying ability to capture juvenile ground sloths, which this great owl was fully large enough to do" (p. 106). The idea of giant, ground-hunting running owls is undeniably incredible and I wish there were substantive studies that backed it up (I don't think there are, alas).

I'm disappearing for a little while soon. Have inadvertently been the focus of all too much media attention over the last few days: somehow the news on the Ashdown maniraptoran seeped into the mainstream and everyone wanted a piece.

For previous articles on owls, please see...

Titan-hawks and other super-raptors (discusses giant Gargano barn owls)
Why do some owls have ear tufts?
From Morocco, with larks, babblers, gazelles, owls and GIANT DINOSAUR BONES
Fish owls in reverse
Chock-full of rodent bones
Myth of the six-foot super-owl
Why can't my readers be dumber? Or: replica owls

Refs - -

Arredondo, O. (1976). The great predatory birds of the Pleistocene of Cuba Smithsonian Contributions to Paleobiology, 27, 169-187

- . 1982. Los Strigiformes fÃ³siles del pleistoceno cubano. BoletÃn de la Sociedad Venezolana de Ciencias Naturales 140, 33-55.

- . & Olson, S. L. 1994. A new species of the genus Bubo from the Pleistocene of Cuba (Aves: Strigiformes). Proceedings of the Biological Society of Washington 107, 436-444.

Brodkorb, P. 1961. Recently described birds and mammals from Cuban caves. Journal of Paleontology 35, 633-635.

Olson, S. L. 1978. A paleontological perspective of West Indian birds and mammals. Academy of Natural Sciences of Philadelphia, Special Publication 13, 99-117.

tetrapodzoology Wed, 06/15/2011 - 02:36

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