Tetrapod Zoology

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As some of you now know, finally I have something that might be considered close to a dream job: I’m now a researcher for Impossible Pictures, the company that did Walking With Dinosaurs, Primeval and a host of other things (website here). This job isn’t going to be forever, but it’s a start, and it doesn’t make me feel any less bitter about being unable to get a job in academia. It means lots of expensive commuting (I don’t live in London, where the company’s based), and it also explains the recent lack of blog posts. But I’m not complaining. So, after turtle genitals and ostrich dinosaurs, I’ve decided to come back with a bang, and blog about… sheep.

Sheep are caprine bovids closely related to goats, and the two groups must have shared an ancestor highly similar to the Barbary sheep, Aoudad or Arrui Ammotragus lervia (Cassinello 1998). While caprines may have originated during the Late Miocene in the Mediterranean region (Ropiquet & Hassanin 2004), sheep might be ancestrally Asian given that the oldest sheep (Ovis shantungensis) is from the Pliocene of China. Unlike goats, sheep possess preorbital, interdigital and inguinal glands, they lack a beard, possess a short tail, and usually exhibit spiralling, supracervical horns. The true sheep belong to the genus Ovis: the bharals or blue sheep Pseudois aren’t true sheep, nor is the Barbary sheep. It’s been suggested at times that takin Budorcas and the recently extinct Balearic cave goat Myotragus balearicus are the closest relatives of true sheep.

Given that, in archaeological or palaeontological samples, it is difficult to distinguish the incomplete postcranial remains of sheep from those of goats, indeterminate sheep or goat remains are often dubbed ‘ovicaprin’. As Derek Yalden wrote in The History of British Mammals, this is a pretty daft name given that there is no such animal as Ovicapra. Indisputable sheep are usually divided into three genetic groups: the Asian argaliforms, the mouflon-like moufloniforms, and the mostly American pachyceriforms.

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Argaliforms are relatively gracile sheep, suited for life in open, rolling habitats, and they have often been regarded as being represented by two Asian species: the Urial O. vignei and Argali O. ammon. It now seems, however, that these two are not close relatives, and that the Urial is a moufloniform (Bunch et al. 2006). Known from Iran in the west to Pakistan and India in the east, Urials are normally light brown, with a long, light-coloured neck ruff and – for a sheep – a rather long, thin tail. Like several of the sheep species, the species is polytypic, and experts remain undecided on which of the many named subspecies really are valid taxa. For the record, the most widely accepted forms are the Ladakh urial O. v. vignei, Transcaspian urial O. v. arkal [shown in adjacent image], Bukhara urial O. v. bocharensis, Afghan urial O. v. cycloceros and Punjab or Salt Range urial O. v. punjabensis. Most urial populations are declining and in danger of extinction, and none of the subspecies listed here have estimated populations exceeding 12,000. It used to be widely thoughts that urials were conspecific with mouflons (which explains why the urial is named O. orientalis in some sources), but this has been largely rejected on the basis of chromosome counts and other differences.

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The largest and arguably most magnificent of wild sheep is the Argali, a wide-ranging species (occurring from Afghanistan to southern Siberia) that possesses prominently ribbed, enormous spiralling horns. Some forms, such as the Tibetan argali, possess a neck ruff. The large body size and hypertrophied display organs of argali have led some to regard them as hypermorphic compared to other sheep. A confusing array of argali subspecies (15 in total) have been named, and it has proved difficult to determine which represent valid taxa, which are hybrids, which are simply the result of phenotypic plasticity*, and even which are correctly assigned to the right species (Geist 1991). The Severtzov’s or Kyzylkum sheep O. a. severtzovi, for example, was conventionally classified as a form of urial** until chromosome counts showed that it was actually an argali (Bunch et al. 1998). Arkal sheep from Iran, Turkmenistan, Uzbekistan and Kazakhstan, conventionally regarded as the urial subspecies O. v. arkal, have recently been found to be genetically close to Kara Tau argali O. a. nigrimontana and are thus probably members of the argali species as well (Hiendleder et al. 2002).

* That is, members of some populations may reach larger body sizes and grow big horns because they have a particularly good diet, or inhabit a particularly favourable environment, compared to other populations.

** Though, actually, it was first named (in 1914) as a distinct species.

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The seven most widely accepted argali subspecies are the Altai argali O. a. ammon, Kara Tau argali O. a. nigrimontana, Nyan or Tibetan argali O. a. hodgsonii [shown in image above], Pamir argali or Marco Polo argali O. a. polii, Tien Shan argali O. a. karelini, Gobi argali O. a. darwini and the probably extinct Northern Chinese or Shansi argali O. a. jubata. Of these, recent studies have supported the validity of at least Altai argali, Kara Tau argali, Tibetan argali, Marco Polo argali and Gobi argali and, among the additional subspecies, the Gansu argali O. a. dalailamae, Kuruktag argali O. a. adametzi, Sair argali O. a. sairensis, Severtzov’s or Kyzylkum sheep O. a. severtzovi, Kazakhstan argali O. a. collium and Littledale argali O. a. littledalei have also been regarded as valid taxa (Hiendleder et al. 2002, Wu et al. 2003) [adjacent picture shows Littledale argali. Unfortunately, many of the subspecies are rarely photographed except as hunter's trophies, so I'm sorry that photos of dead animals are the only ones we have available. While hunting of these animals does, arguably, add to the local economy, it is debatable whether sustained hunting is wise given the low numbers of some populations].

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Perhaps the best known of these animals (viz, the one usually mentioned and/or illustrated in books) is the remarkable Marco Polo argali from the Pamir Mountains of Afghanistan, Kyrgyzstan, Tajikistan, Pakistan and China. It possesses the longest horns of any argali, with individual horns recorded as reaching nearly 2 m (measured along the spirals) in some individuals. Despite frequent comments that it is the largest argali and thus the largest sheep, it is apparently exceeded in size by record-holding Altai and Gobi argalis. The size and fantastic appearance of these sheep makes them attractive targets for trophy hunters and, as an example, in Tadjikistan in 1995, hunters were able to kill argali for a fee of US$10,000-20,000.

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North America is home to two species of wild sheep. The Bighorn O. canadensis occurs from northern Mexico to SW Canada, occurring in mountainous environments as well as deserts. Bighorns are not, apparently, named for their big horns. Rather, they are named for the Big Horn Mountains of Wyoming and Montana, though unfortunately I forget where I read this. Whatever, the horns are indeed big in the mountain-dwelling bighorns, and can have a combined weight of almost 20 kg, which is about equal to the weight of the rest of the skeleton. Fights between males [see adjacent pic] have been recorded as lasting over 25 hours, though this is not constant fighting of course and involves lots of resting and posturing. Bighorn do have accidents while climbing and fall to their deaths, but data indicates that such incidences are rare, with, for example, five deaths out of an annual count of 42 being due to falling (Kamler et al. 2003).

For whatever reason, bighorns in some populations seem to have, err, flexible sexual preferences and it has even been claimed that some bighorn populations are ‘homosexual societies’ where same-sex courtship and mating is routine among males (Bagemihl 1999). Courting males use the same routine of stylized gestures and postures as do male-female pairs, including a low-stretch, a head twist, a foreleg flick, and mutual grooming, head-rubbing and genital licking, and culminating in penetration. Apparently, some female bighorns morphologically mimic males and thereby solicit extra attention. Freemartins have been recorded among bighorns (Kenny et al. 1992) [freemartinism describes the condition where the female twin of a male develops intersexual characters: she may be born with both male and female genitalia, and display male appearance and behaviour].

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You’ve probably heard that research on ‘gay’ sheep has been plagued by controversy (Steve Bodio covered this subject here), and I find it a difficult area to discuss as I just don’t know how far we should go in comparing this behaviour with that of our own species. It is, however, always worth reminding people (especially homophobes and right-wingers) that, despite what they say, homosexuality is not ‘unnatural’ given that it is pervasive and universal in the animal kingdom.

And on that note, I leave. More on sheep at another time.

Refs – -

Bagemihl, B. 1999. Biological Exuberance. Animal Homosexuality and Natural Diversity. St. Martin’s Press, New York.

Bunch, T. D., Vorontsov, N. N., Lyapunova, E. A. & Hoffmann, R. S. 1998. Chromosome number of Severtzov’s sheep (Ovis ammon severtzovi): G-banded karyotype comparisons within Ovis. The Journal of Heredity 89, 266-269.

- ., Wu, C., Zhang, Y.-P. & Wang, S. 2006. Phylogenetic analysis of Snow sheep (Ovis nivicola) and closely related taxa. Journal of Heredity 97, 21-30.

Cassinello, J. 1998. Ammotragus lervia: a review on systematics, biology, ecology and distribution. Annales Zoologici Fennici 35, 149-162.

Geist, V. 1991. On the taxonomy of giant sheep (Ovis ammon Linnaeus, 1766). Canadian Journal of Zoology 69, 706-723.

Hiendleder, S., Kaupe, B., Wassmuth, R. & Janke, A. 2002. Molecular analysis of wild and domestic sheep questions current nomenclature and provides evidence for domestication from two different subspecies. Proceedings of the Royal Society of London B 269, 893-904.

Kamler, J. F., Lee. R. M., DeVos, J. C., Ballard, W. B. & Whitlaw, H. A. 2003. Mortalities from climbing accidents of translocated bighorn sheep in Arizona. The Southwestern Naturalist 48, 145-147.

Kenny, D. E., Cambre, R. C., Frahm, M. W. & Bunch, T. D. 1992. Freemartinism in a captive herd of Rocky Mountain bighorn sheep (Ovis canadensis). Journal of Wildlife Diseases 28, 494-498.

Wu, C. H., Zhang, Y. P., Bunch, T. D., Wang, S. & Wang, W. 2003. Mitochondrial control region sequence variation within the argali wild sheep (Ovis ammon): evolution and conservation relevance. Mammalia 67, 109-118.

Comments

  1. #1 Allen Hazen
    May 5, 2007

    Congratulations on paid employment! (Academic jobs are awfully hard to get in my field– philosophy– too: I had a fairly depressing conversation with one of our graduate students yesterday. All I can say is, try to get some more publications, go to conferences and be visible: an academic position MAY come up eventually. … University jobs typically involve teaching: think how you can spin your blogging and work for the movie producers on your C.V. as evidence that you’s be able to pack undergraduates into a lecture theatre.)

    And… THANKS for another mammal post! I gather Caprines are fairly far from Bovines: the split must have been early in the history of the Bovids. I think I saw somewhere a suggestion that monophyly of the Bovidae has been doubted: that it’s not certain that the l.c.a. of Bovines and Caprines wasn’t also an ancestor of giraffes or pronghorns or something. Has this been talked about in your hearing?

  2. #2 Tristram Brelstaff
    May 5, 2007

    Congratulations on the job! I hope it goes well for you.

    Long distance commuting can have its advantages, if you can do it by train. It can give you time to read, think, sleep, and, if you take a laptop, even blog. Or else you can just gaze out of the window conducting an informal survey of the larger tetrapods of southern England (I quite often see deer on my journey to work).

  3. #3 Darren Naish
    May 5, 2007

    Thanks for your comments. Tristram, you’re right about creature-watching and trains: I’ve seen tons of stuff this way, including plenty of sika and roe deer. As for using the laptop on the train, I have a power-hungry machine that only works for about 20 mins before the battery runs out (and none of the trains I use have plug sockets).

    Allen: glad you like the mammal posts. No, I haven’t heard of the hypothesis of bovid non-monophyly, and all the recent work on this group finds bovid monophyly to be about as secure as it could possibly be (e.g., Hassanin & Douzery 1999a, b, Gatesy & Arctander 2000, Liu et al. 2001, Ropiquet & Hassanin 2004, Price et al. 2005). As I covered briefly in the mystery bovid article, most studies find Bovidae to consist of a Bovinae that includes cattle, boselaphines and tragelaphines, and an Antilopinae that includes gazelles, caprines (sheep, goats and goat antelopes), wildebeest and hartebeest, oryxes and sable antelope, and others. Caprines are definitely close to alcelaphines (wildebeest and hartebeest) and hippotragines (oryxes and sable antelope) and perhaps to antilopines (gazelles), but studies differ in exactly how these clades are related. There’s coverage of all this at ultimateungulate.

    Refs – -

    Gatesy, J. & Arctander, P. 2000. Hidden morphological support for the phylogenetic placement of Pseudoryx nghetinhensis with bovine bovids: a combined analysis of gross anatomical evidence and DNA sequences from five genes. Systematic Biology 49, 515-538.

    Hassanin, A. & Douzery, J. P. 1999a. Evolutionary affinities of the enigmatic saola (Pseudoryx nghetinhensis) in the context of the molecular phylogeny of Bovidae. Proceedings of the Royal Society of London B 266, 893-900.

    - . & Douzery, J. P. 1999b. The tribal radiation of the family Bovidae (Artiodactyla) and the evolution of the mitochondrial cytochrome b gene. Molecular Phylogenetics and Evolution 13, 227-243.

    Liu, F.-G. R., Miyamoto, M. M., Freire, N. P., Ong, P. Q., Tennant, M. R., Young, T. S. & Gugel, K. F. 2001. Molecular and morphological supertrees for eutherian (placental) mammals. Science 291, 1786-1789.

    Price, S. A., Bininda-Emonds, O. R. P. & Gittleman, J. L. 2005. A complete phylogeny of the whales, dolphins and even-toed hoofed mammals (Cetartiodactyla). Biological Reviews 80, 445-473.

    Ropiquet, A. & Hassanin, A. 2004. Molecular phylogeny of caprines (Bovidae, Antilopinae): the question of their origin and diversification during the Miocene. Journal of Zoological Systematics & Evolutionary Research 43, 49-60.

  4. #4 Neil
    May 5, 2007

    Congrats on the job. Also good news for the people that watch Primeval. Some of the inaccuracies were painful (An ‘arthropluera’ that is blantenly a blown up modern day giant centipede and twice the length of any recorded Arthropleura, anybody!?). Also cool post, never thought those white fluffy things were so interesting!

  5. #5 Hai~Ren
    May 5, 2007

    *tries counting all the subspecies of sheep mentioned so far.*

    *falls asleep*

  6. #6 Anthony Docimo
    May 5, 2007

    Congratulations on the impending job. You’ll get it, I’m sure & certain.
    Maybe one day (soon!) we’ll see on the credits for an episode of Primeval “Written By Darren Naish”.
    looking forwards to that.

    have nice days & be well.

  7. #7 Raymond
    May 5, 2007

    Congratulations.(Raises glass in a toast)

  8. #8 Steve Bodio
    May 6, 2007

    Congratulations! I expect they will have no gaffes as mentioned by Neil when Darren is on the job!

  9. #9 Katie Brakora
    May 7, 2007

    IIRC, the bovid non-monophyly issue stems from morphological analyses, rather than the recent spate of molecular analyses, which have pretty satisfyingly sealed the deal for Bovidae being monophyletic. Morphological, extant bovids are united by the presence of true horns, and maybe one or two other very minor features – and that’s it. The question arises – if you found a bovid in the fossil record and it didn’t have horns, would you know it was a bovid? Nope. So although horns are very significant structures (and you could probably break them down into multiple smaller or histological characters), given the head-structure-evolvability of ruminants, it seemed a bit tenuous, I think.

    In any case, it’s full steam ahead now.

    Still working on that mystery bovid. Swamped though.

    Great post. Argali totally rock, as do ibex and others. But my heart belongs to the bongo :o)~

  10. #10 John H
    May 7, 2007

    Well done, Darren! Sounds like a fab gig!

  11. #11 Will Baird
    May 7, 2007

    Congratz on the job!

    However, I sense a disturbing trend here. First the gobsmacking sized bits of turtles and now sheep. Darren. Is there something you’d like to get off your chest? ;)

  12. #12 Laelaps
    May 7, 2007

    Congratulations on the new job! It may not be what you were looking for, but I’m sure the projects you’re doing research for will benefit greatly from your expertise.

  13. #13 johannes
    May 7, 2007

    Congratulations on the new job!

    Interisting post on sheep, by the way, I think Daimler-Chrysler will just love those details from the sexual life of their trademark Dodge Bighorn ram!

  14. #14 Sarda Sahney
    May 7, 2007

    Congratulations, I look forward to seeing your attention to detail compliment future prehistoric programming!!

  15. #15 neil
    May 7, 2007

    Congrats on the TV gig! Judging from the popularity of your TZ, there is a big market for more-sophisticated and scientifically up-to-date zoology/paleontology programming. I only hope the stuff you work on gets to the States promptly!

    Regarding the name “bighorn sheep”, there’s an oral history from the Crow (Apsaalooke) nation that tells how the Bighorn River was named by a band of seven magical sheep, lead by one “Big Metal”:

    “We seven rule these Bighorn Mountains. That
    river down there in the bottom is the Bighorn
    River. Whatever you do, don’t change its name.
    It shall be know as the Bighorn River. If you ever
    change the name of the river, there will be no
    more Absaroka (Crow). The Absaroka will be no
    more.” (from the National Park Service guide to the Bighorn Recreation Area)

    Of course, the mention of metal in the legend reveals that this version postdates European contact. Still, I’m inclined to believe that the river, basin and mountains are named for the sheep and not vice versa (at least until you find that reference).

    Lewis and Clark named a number of rivers and peaks “Argali” or “Ibex” either because they saw bighorns there, or perhaps in as translations of existing native names.

  16. #16 luca
    May 9, 2007

    Woah! Congratulations, Darren! Sorry for being so late to the party, I had a couple of heavy weeks too. More to come soon.

  17. #17 TheBrummell
    May 9, 2007

    …the horns are indeed big in the mountain-dwelling bighorns, and can have a combined weight of almost 20 kg, which is about equal to the weight of the rest of the skeleton.

    OK, that’s crazy. I’ve done work on sexual selection, and as a metric of how far down the impress-the-females-at-any-cost path a species has gone, comparing the mass of the character with the mass of some other organsimal feature of obvious importance seems useful, in a qualitative kind of way. Highly appropriate for a scientific presentation at a meeting, for example.

    I’ve been fortunate enough to see Bighorns in the wild on several occassions, including once a fight between males. The sound of the impacts carries an incredible distance, such that I heard the fight before I saw the animals, from about two kilometers away.

    Congratulations on the new job. Not as nice as a big sack full of cash lying about in the countyside, I suppose, but I’m happy to hear you’ll be able to apply your expertise to a couple of good projects. Please keep up the good work, both here and in your scientific career (i.e. peer-reviewed publications).

  18. #18 yuyuqun
    October 2, 2007

    Hi Darren,

    Could you tell me where is the photo of Ovis ammon hodgsoni from (location)? I have a argali photo from Himalaya mountains, can we share them?

    yuqun yu

  19. #19 Darren Naish
    October 18, 2007

    Dear Yuqun Yu – I’m having trouble finding out where I got the image from. I will post the answer here as soon as I find it – please come back here and check again. Thanks for your interest.

  20. #20 JIA ZHIYUN
    December 22, 2007

    Dear Friend,

    Who can tell me how to contact Yuyu Qun? We lost contact for years. Thanks a lot.

    Zhiyun JIA, PhD
    Standing Associate Editor
    Acta Zool Sinica

  21. #21 Sibylle
    May 11, 2009

    thanks for all that really useful info on argali – I’m doing a lot of research on snow leopards and of course argalis are one of the snow leopard’s main prey species. You mention that argali hunting may help the local economy, its a vexed question. While it may help the local economy in some areas it certainly doesn’t help the local snow leopards who due to decreases in natural prey species then hunt domestic animals, for which they are of course killed in retribution. Slowly some places are changing the way local people and snow leopards interact, hopefully it will be fast enough to save the species in the wild. Keep up the great blog.
    Sibylle
    http://www.snowleopardblog.com

  22. #22 Lavaa Boya
    February 6, 2011

    Hello mr. Darren Naish
    Greetings from Mnogolia
    My name is L.Boya. I’m 38 years old and work as national hunting guide for argali and ibex for last 17 years. Congratulations for studing of ram and useful info on argali. Please keep up the good work and keep study argali. Iwould like share my knowledge with you and others ho had great love and interest for this magnicifent geature.
    With regards
    l.Boya