I really must get this series on pouches, sacs and pockets finished. Last time, we looked at baleen whales (and then I got distracted by Caperea): in these animals, a large, inflatable laryngeal sac is used in producing loud, resonating noises (though roles in gas storage or the mechanics of exhalation have also been suggested).
Another ventrally located laryngeal sac is present in the Reindeer Rangifer tarandus [photo above, by Karen Laubenstein, from wikipedia, shows an Alaskan reindeer with wonderfully elaborate antlers]. The sac originates from the trachea close to the epiglottis, is present in both sexes (though is much larger in males, reaching 4000 cubic cm when inflated), and can extend asymmetrically either along the left or right side of the neck (Frey et al. 2007).
During the rut, males adopt a characteristic posture where the head and neck are kept low and the throat is extended [shown here, from Frey et al. (2007)]. Because the air sac is seen to inflate and deflate as the deer calls, an acoustic role for the sac is obvious (the noises made by calling reindeer are difficult to describe: they make hoarse, repetitive guttural noises).
Exactly what effect the throat sac has on the sounds generated in the larynx is unclear. One suggestion is that the sac augments the acoustic output of the vocal tract, such that the resulting noise combines output from the mouth and nose with output from the sac, emitted via the soft tissues of the neck. In other words, the sac 'filters' the sounds produced in the vocal tract (in acoustics, a filter is "a resonator that absorbs energy at certain resonance frequencies" (Frey et al. 2007, p. 151)). Because displaying males approach females broad-side in what's been called a 'broadside acoustic display', it appears likely that the sounds generated by these deer mostly emanate sideways.
Other acts of acoustic weirdness in Cervidae
The evolution of this remarkable laryngeal structure is made all the more, err, remarkable by the fact that it's (so far as we know) completely novel within Cervidae, this despite the fact that other deer lineages have evolved profound modifications to enhance their calls [calling male Red deer shown below, image by Bill Ebbesen, from wikipedia. That lump in the throat corresponds to a highly mobile larynx that descends way down in the neck during vocalisation. Read on].
As we've seen before, Red deer Cervus elaphus and Fallow deer Dama dama use laryngeal retractors and an elastic thyrohyoid linkage to pull the larynx down toward the chest and thereby decrease the formant frequencies of their calls (Fitch & Reby 2001, McElligott et al. 2006) (and formant frequencies are known to correlate with female preference and mating success in both Red and Fallow deer: see Charlton et al. (2007), Vannoni & McElligott (2008) and Reby et al. (2010). Incidentally, it's probably true to say - as some have - that the vocal behaviour of Red deer has been more studied than that of any other mammal outside of Primates). Wapiti C. canadensis retract the larynx markedly as well (and I follow Geist (1999) and Groves (2005) in regarding the Wapiti as a separate species from Red deer*). Phylogenies show that Red deer and Wapiti belong to a disparate lineage relative to Fallow deer (e.g., Pitra et al. 2004): even if Cervus and Dama are sister-taxa, there are still numerous taxa in the Cervus clade that lack the laryngeal structures seen in the C. elaphus + C. canadensis clade, and seen in D. dama. Their similar laryngeal anatomies must therefore have evolved convergently.
* Some other deer traditionally included in C. elephus also deserve to be recognised as separate species: I will avoid discussing this mess for now and point the interested reader to Pitra et al. (2004) and Groves (2005).
Similar elastic structures are absent in reindeer: there's no indication that they can move the larynx in the same way.
Peculiar noises are also made by some other large deer, but in this case I'm not talking about vocal noises; White-lipped deer Przewalskium albirostre, Père David's deer Elaphurus davidianus, Red deer, Wapiti and Reindeer all produce clicking or cracking noises in their joints as they walk (McCullough 1969, Thomas & Toweill 1982, Geist 1999). Red deer only seem to produce the cracking noise in the forelimbs, while Reindeer at least produce cracking in both fore- and hindlimbs.
We looked some time ago at joint-clicking in eland: remarkably, the noises made by the joints of these antelopes form part of their dominance displays (Bro-Jørgsen & Dabelsteen 2008). Could the same be true of the joint-clicking deer? A popular idea is that the clicking noises provide information on the whereabouts of other herd members, and also on the approach of possible danger. I don't know if anyone has studied this (though humans who hunt deer have certainly been very interested in it) - let me know.
One more interesting thing to note on deer and acoustics: it has been suggested that the enormous palmate antlers of Moose Alces alces may work as parabolic reflectors that help collect sound (Bubenik & Bubenik 2008) [spectacular Alaskan moose shown below; photo by Donna Dewhurst, from wikipedia. Note the profound asymmetry in the antlers... fluctuating asymmetry, another subject I must cover some time].
Moose ears are large and sensitive, but these authors showed that a moose can increase the acoustic pressure in its ears by about 19% if it points the ears towards the antlers rather than toward the sound source. I would assume that this effect is incidental given that the antlers are still shed annually, mostly play a role in sexual combat and display, and are absent in females (one would assume that they would be retained year-round, and be present in females, if an acoustic role provided a selective advantage). However, moose that inhabit Alaskan tundra environments have the biggest antlers, and this is a habitat where sound travels furthest. Then again, visual signals would also travel furthest, so - as usual - things are not clear-cut.
Reindeer are 'grotesque giants'
Having shown that Reindeer are unexpectedly weird by virtue of their laryngeal sacs, it's only right to say that they're really interesting for lots of other reasons: with their elaborate antlers (proportionally, the biggest of any deer), cursorial specialisations, large body size (second largest New World deer), long neck manes, large fat stores and highly peculiar, complex pigmentation (they have capes, rump patches, lateral stripes, forehead patches, eye rings and 'socks'*), they're flamboyant animals that can be regarded as 'extreme' members of their group (incidentally, the neck mane might be a visual signal linked to the neck sac) [Rangifer and Alces are shown in the diagram below as extreme members of the mostly New World deer clade that includes brockets, roe deer, reindeer and moose (from Geist (1999))].
Geist (1999) referred to animals of this sort as 'grotesque giants' and noted that they tend to have evolved in cold, harsh Ice Age environments. Gould used the term 'asynchronous hypermorphs' for the same set of species. Other examples - according to Geist - include moose, wapiti, muskox, woolly rhinos, short-faced bears and humans.
* Pigmentation patterns are highly variable in reindeer, with some forms being far more elaborately patterned than others. Eurasian tundra reindeer are the most elaborate.
More laryngeal bullae than you can shake a stick at
So far in this series of articles, we've looked at primates, baleen whales and reindeer. But these are far from the only mammals with laryngeal diverticula located on the midline of the throat: small sac-like structures located on the ventral surface are also present in opossums (Didelphis), quolls (Dasyurus), some phalangers (Trichosurus and Phalanger), swamp wallabies (Wallabia), hedgehogs (Erinaceus), squirrels (Sciurus), marmots (Marmota), water voles (Arvicola), tapirs (Tapirus), horses (Equus), boar (Sus), eland (Tragelaphus), saiga (Saiga), takin (Budorcas), some bears (Ursus), wolves (Canis lupus), southern sea lions (Otaria) and various others (see Frey et al. (2007) for a complete list: their table, with adjacent diagrams showing laryngeal diverticula position, is shown here).
In some taxa, these structures are associated with enlarged hyoid bullae (like those looked at previously in apes and howler monkeys), but in others they are not. And in some of these mammals, these diverticula are paired; in others they are single. In the marsupials with a laryngeal diverticulum, and also in eland, saiga and takin, the structures are housed inside an inflated bulla formed from the thyroid cartilage (and are thus contained within the larynx). As yet, the role that these many diverticula might play in vocalising and other aspects of behaviour has been little investigated for most of the species concerned. Roland Frey and his colleagues have, however, been publishing some great studies on the laryngeal anatomy and vocalisation in such species as muskox, takin and weird gazelles. More soon!
For the previous articles on pouches, pockets and sacs in mammal heads, necks and chests, see...
- Pouches, pockets and sacs in the heads, necks and chests of mammals, part I: primates
- Pouches, pockets and sacs in the heads, necks and chests of mammals, part II: elephants have a pouch in the throat... or do they?
- Pouches, pockets and sacs in the heads, necks and chests of mammals, part III: baleen whales
And for previous Tet Zoo articles on deer, see...
- Deer oh deer, this joke gets worse every time I use it
- Britain: wildlife theme-park
- At the 56th SVPCA - hello Dublin! (includes some discussion of Megaloceros)
- The plasticity of deer
Refs - -
Bubenik, G. A. & Bubenik, P. G. 2008. Palmated antlers of moose may serve as a parabolic reflector of sounds. European Journal of Wildlife Research 54, 533-535.
Charlton, B., Reby, D. & McComb, K. 2007. Female red deer prefer the roars of larger males. Biology Letters 3, 382-385.
Fitch, W. T. & Reby, D. 2001. The descended larynx is not uniquely human. Proceedings of the Royal Society of London B 268, 1669-1675.
Frey, R., Gebler, A., Fritsch, G., Nygrén, K., & Weissengruber, G. E. (2007). Nordic rattle - the hoarse phonation and the inflatable laryngeal air sac of reindeer (Rangifer tarandus) Journal of Anatomy, 210, 131-159
Geist, V. 1999. Deer of the World. Swan Hill Press, Shrewsbury.
Groves, C. 2005. The genus Cervus in eastern Eurasia. European Journal of Wildlife Research 52, 14-22.
McCullough, D. R. 1969. The Tule Elk. Its History, Behavior and Ecology. University of California Press, Berkeley.
McElligott, A. G., Birrer, M. & Vannoni, E. 2006. Retraction of the mobile descended larynx during groaning enables fallow bucks (Dama dama) to lower their formant frequencies. Journal of Zoology 270, 340-345.
Pitra, C., Fickel, J., Meijaard, E. & Groves, C. 2004. Evolution and phylogeny of old world deer. Molecular Phylogenetics and Evolution 33, 880-895.
Reby, D., Charlton, B., Locatelli, Y. & McComb K. 2010. Oestrous red deer hinds prefer male roars with higher fundamental frequencies. Proceedings of the Royal Society of London B 277, 2747-2753.
Thomas, D. C. & Toweill, D. E. 1982. The Elk of North America; Ecology and Management. Stackpole Books, Harrisburg, PA.
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P. albirostre.
E. davidianus... I hope. :-)
Hmm. You're right: it should be albirostre, but the incorrect spelling albirostris has been widely used (and _is_ in the several texts I checked while writing). Similarly, davidianus is correct, but davidanus has been widely used and is the spelling I have in front of me now (in Geist's book). One 'authority' demonstrating correct spelling...
Leslie, D. M. 2010. Przewalskium albirostre (Artiodactyla: Cervidae). Mammalian Species 42, 7â18.
Not all bull moose have palmated antlers, though. Especially in northern Europe a large percentage of the bulls have antlers of the 'cervine' type. In this part of the world, moose have been intensively hunted (or 'managed', if you prefer that euphemism) for many decades; thus, as an explanation for this phenomenon it has been suggested that hunters have disproportionately targeted bulls with palmate antlers (which are considered more spectacular trophies).
Grotesque they may be, and size is of course something relative, but still I don't know if I would like to call Rangifer a 'giant'; domestic reindeer, in particular, are medium-sized at best (at least by artiodactyl standards). Especially when compared in size with their natural enemy, Santa Claus.
...and 'New World deer' refers here specifically to the clade Odocoileinae, I presume?
Last time I checked, human evolution was considered to have mostly taken place in tropical Africa rather than in 'cold, harsh Ice Age environments'.
The 'parabolic reflector' hypothesis obviously only applies to moose with palmate antlers: for this reason, I didn't think the selection for 'cervine' antlers warranted mention. In Prussia, cervine-antlered bulls became selected after deliberate killing of palmate-antlered moose, but the trend was reversed after palmate bulls became protected and cervine-antlered bulls were deliberately culled.
Re: reindeer as 'grotesque giants', gigantism is always relative; by this standard, Rangifer is indeed 'giant' (Arctic caribou average 80 kg for males and 60 kg for females: huge compared to other New World deer). As for whether 'New World deer' corresponds to Odocoileinae, I didn't use this name because its content is controversial (the right name would be Capreolinae if roe are indeed part of this clade).
As for human evolution occurring mostly in Africa... yes, I hear you. That's mostly why I included that "according to Geist" bit.
Even leaving the cold harsh environment bit aside, I'm not sure humans really qualify as 'giant' compared to our close relatives in Hominidae -- bigger than chimps, yes, but roughly comparable to orangutans and definitely smaller than gorillas (though direct comparison is a bit skewed because all of those are more sexually dimorphic in size than humans are) -- especially if you consider that a true human average would be smaller than the average modern Westerner (since modern medicine and nutrition have allowed us to get much closer to our maximal size, a benefit that chimps and orangutans don't get)
Yeah... I don't know if Geist ever elaborated on his ideas about human evolution anywhere (he did publish a book on human evolution in 1978*, so this is one possible venue): if he was comparing modern humans (and, presumably, neanderthals) with other hominids, maybe he had australopithecines and such things as Homo habilis in mind.
* Life Strategies, Human Evolution, Environmental Design. Springer, New York.
Could we have some comment on the presence or absence of similar structures in the Piranhamoose?
[from Darren: sorry, delayed by spam filter]
An interesting (or nerdy)note about the calls of wapitis:
Did you know that the screams of the Nazguls at "The lord of the rings" are nearly un-modified wapiti-calls?
When I was some months ago at a game reserve at the Schönbuch forest, I watched the deers of course, especially one particular male, which was roaring. The roaring of a red deer (which is, for all who don´t know this) quite different from wapiti calls, is really a quite spectacular acustic experience.
To add something about reindeers, some of them are truly gigantic. Of course there are also pygmy species like those of Spitzbergen. But there are also giant forms, rivaling mooses in size. When I was at the Museum of Natural History at Vienna, I saw a huge caribou which was as large as a horse.
Interestingly, a specimen of an ice-age rendeer I saw at the zoological museum at Copenhagen, had absolutely gigantic antlers:
http://bestiarium.kryptozoologie.net/artikel/bizarre-hirsche-teil-2-exz…
It is really bizarre that those animals grow within a few months such a huge amount of bone-mass, just to shed it some months later.
In some cases the antlers of moose are extremely large, but in contrast some are nearly horn-like, like this specimen I photographed at the museum of hunting and forestry at Hørsholm , Denmark:
http://bestiarium.kryptozoologie.net/artikel/bizarre-hirsche-erster-tei…
Darren:
Yes, but... by that same standard you could also say (for example) that wildebeest are 'giants' among the extant alcelaphines. (Besides, the largest white-tailed and mule deer are actually not that much smaller than reindeer or caribou; a large northern white-tail buck may weigh 125-130 kg.)
Actually, what I was getting at there was to point out that the wapiti, which is the second-largest New World cervid, is not a 'New World deer' in the phylogenetic sense.
There is doubt about whether roe deer belong to the 'New World deer' clade? That I didn't know; do you have a reference?
"moose, wapiti, muskox, woolly rhinos, short-faced bears and humans."
We call it Bergmann's rule :]
I am shocked that David MarjanoviÄ missed the rather prominent misspelling of Cervus elaphus.
The human lineage reached its current size, more or less, with Homo ergaster from the early Pleistocene, well before the "Ice Age".
William Miller wrote:
Zoo animals do. (At least, in some zoos.) Are they often bigger than their wild relatives?
Fascinating post, Darren, although you seem to have left out some of the most remarkable things about reindeer: namely, their volant abilities and the occasional occurrence of individuals with luminescent nasal regions.
Wouldn't moose living in dense forests depend on hearing much more than those living on the tundra? Although all of them move into the forests in winter...
But the ones with least palmate antlers are Manchurian moose (A. a. cameloides, if I remember correctly), that live in very dense forests.
BTW, the transition between Alaska and Eurasia-type moose is very abrupt in Eastern Siberia, and I wouldn't be surprised if they get split sooner or later. Canadensis is larger, more aquatic in summer, feeds on willows rather than aspens, etc. Someone even told me that their chromosome numbers are different - I don't know if it's true.
I don't think Arctic megafauna is any more weird than tropical one... it's just that there's so little left of it, we are not used to this kind of animals. They certainly don't look weird in their natural habitat.
Darren:
On that general subject, there is also this paper:
Cap, H., Delaporte, P., Joachim, J. & Reby, D. 2008. Male vocal behavior and phylogeny in deer. Cladistics 24, 917-931.
Sordes:
As large as a horse? What kind of horse do you mean? A Przewalski's horse weighs up to about 300 kg, but domestic horses may be considerably bigger. Even the largest breeds of ponies weigh more than 350 kg, and typical riding horses weigh in the thereabouts of 400-600 kg. And draft horses are, of course, much heavier still. On the other hand, the largest North American caribous that I've heard of have weighed only slightly more than 300 kg (and that was considered exceptional). Are there any actual size/weight measurement data - as opposed to estimates - on that Vienna caribou specimen?
Vladimir:
Hundertmark & Bowyer (2004) reviewed the data on moose phylogeography relatively recently; in their opinion, there are no genetic grounds for splitting Alces alces.
It is true - although the difference isn't completely clear-cut. North American moose have a karyotype of 2N = 70, while most Eurasian moose have 2N = 68 (some moose from eastern Siberia also have 2N = 70). And the above-cited Hundertmark & Bowyer didn't think that the karyological data was sufficient reason for species-level splitting.
Me:
Should be: Deleporte.
Reference:
Hundertmark, K.J. & Bowyer, R.T. 2004. Genetics, evolution, and phylogeography of moose. Alces 40, 103-122.
Many thanks for great comments. Some responses...
Firstly, you all know that I put those little spelling mistakes in there for fun, right? I'm glad so many of you enjoy pointing them out :)
Re: the 'grotesque giant' hypothesis (comment 9), I don't want to spend too much time defending someone else's pet hypothesis, but my understanding is that Geist's 'grotesque giants' aren't just giants, they also have an abundance of what Geist called 'luxury organs' (big fat stores, elaborate manes and pigmentation etc.). So, wildebeest and white-tailed deer may indeed be relatively 'giant' within their respective clades, but I'm not sure that they qualify as 'grotesque giants'. I do like the 'grotesque giant' hypothesis: cool temperatures, open habitats, seasonally rich resources and large body size all seem correlated, resulting in the evolution of flamboyant, elaborately decorated big mammals with antlers, horns, tusks, big fat deposits and big brains. "The evolution of bizarre Ice Age mammals is a reflection of the seasonal riches of temperate, cold, and periglacial habitats and of the freedom from biological constraints that are so prevalent in the tropics. The hallmarks of the ice ages are the "luxury species", the "grotesque giants", of which Homo sapiens is a splendid example. The sharply increased fertility of the Ice Age landscapes liberated deer evolution and ultimately that of humans" (Geist 1999, p. 2). As some have noted, there _are_ problems with the idea, and whether it applies to humans or not is problematical.
Is the 'grotesque giant' hypothesis the same thing as Bergmann's rule (comment 10)? Not really, because Bergmann's rule only predicts size, not ornamentation. And seeing as I keep mentioning Valerius Geist so much, have you seen...
Geist, V. 1987. Bergmann's rule in invalid. Canadian Journal of Zoology 65, 1035-1038.
- . 1990. Bergmann's rule is invalid: a reply to J. D. Paterson. Canadian Journal of Zoology 68, 1613-1615.
It has been argued (primarily by Geist) that Bergmann's rule is invalid because many mammals (wolf, Arctic fox, brown bear, muskox, Dall's sheep, reindeer, moose, white-tailed deer) _decrease_ in size as you go further north; they do not increase after 60-65 deg N. As is often the case, the 'rule' can perhaps be best considered a 'tendency' or 'generalisation' (Ashton 2002, Meiri & Dayan 2003).
Oh, and, yes, by 'New World deer' I was referring to the clade that includes moose, reindeer, brockets, white-tails etc. not 'deer currently living in the New World' (which, as you note, includes Wapiti). Might there be an 'Odocoileinae' that is not the same in content as 'Capreolinae'? (comment 9): well, Randi et al. (1998) recovered a trichotomy of (1) an Odocoileus, Mazama and Rangifer clade, (2) an Alces, Capreolus and Hydropotes clade, and (3) a Muntiacinae + Cervinae clade. Under this topology, roe are not part of Odocoileinae. Since then, Pitra et al. (2004) recovered monophyly of Odocoileinae/Capreolinae.
Finally... oh, I was going to comment on moose phylogeography, but I see Dartian has addressed this.
Refs - -
Ashton, K. G. 2002. Patterns of within-species body size variation of birds: strong evidence for Bergmann's rule. Global Ecology & Biogeography 11, 505-523.
Meiri, S. & Dayan, T. 2003. On the validity of Bergmann's rule. Journal of Biogeography 30, 331â351.
Pitra, C., Fickel, J., Meijaard, E. & Groves, C. 2004. Evolution and phylogeny of old world deer. Molecular Phylogenetics and Evolution 33, 880-895.
Randi, E., Mucci, N., Pierpaoli, M. & Douzery, E. 1998. New phylogenetic perspectives on the Cervidae (Artiodactyla) are provided by the mitochondrial cytochrome b gene. Proceedings of the Royal Society of London B 265, 793-801.
...So moose with different chromosome numbers can interbreed? That would be exciting.
That is... severely counterintuitive.
David:
So the authors imply, although they do caution that this still needs to be properly demonstrated. But chromosomal polymorphism isn't unheard of in wild artiodactyls (it's been recorded in many wild boar Sus scrofa populations, for example).
Modern North American hunters have learned from Native Americans to mimic elk and deer vocalizations. A few hunting companies even specialize in making elk "bugle" and deer "grunt" calls. These calls are especially effective during the elk and deer rut mating seasons. I have called in and taken many white-tailed deer using a grunt call. Here is a sample I found on youtube.
http://www.youtube.com/watch?v=oERzlVKl2JM
Re the different chromosomes numbers of North American and Eurasian moose - is there any connection here with the recently extinct stag moose Cervalces scotti? I thought the North American moose were recent immigrants from Eurasia - is there any sign in the fossil record of them interbreeding with Cervalces, resulting in the replacement of the original phenotype with the modern form but leaving a genetic marker. There is a slightly similar situation with white-tailed deer and related species - the fertile hybrids back-cross with the parent species, resulting in animals with the 'wrong' mitochondrial DNA for their appearance.
Re grotesque giants: I wasn't challenging the idea as a whole, it seems to make sense, only its application to humans.
Re validity of Bergmann's rule: hmm. Many of those same mammals (wolf, white-tailed deer, brown bear) I've seen used as *examples* of the rule - record whitetails tending to come from the northern Great Plains states & southern Canada being larger than those in the southern US, and the Florida Key deer being both the southernmost and the smallest whitetails; Alaskan and Siberian wolves being larger than Montana wolves, and those being larger than Indian and (currently extirpated) southern US/Mexican wolves; Alaskan browns (U. a. middendorffi) being larger than grizzlies, and Alaskan grizzlies being bigger than lower-48 individuals. Perhaps the "above 60-65 degrees" thing is a distinct and competing tendency (due to less food supply or something?) rather than an invalidation of the original rule?
Re chromosomal polymorphism in moose and wild boar: wow, that is cool, didn't know about that.
@Deerhunter
Calling a deer has been known for millennia in Europe. There are even hunters' deer-calling competitions. This is one thing I could never watch, for danger of exploding from laughter.
Best story was about whistles for railway engines in n America, which allegedly made elk in rut to go on railroads and try to fight with approaching train. Until the railway changed whistles.
Dartian: thanks for Hundertmark & Bowyer info. Unfortunately, they don't differentiate between Magadan Province proper (which is on the Sea of Okhotsk, close to A. a. cameloides range) and Chukotka (which is on the Bering Straight and was formally a part of Magadan Province up to, I think, 2003). These two areas are on different sides of the abovementioned alces/canadensis divide. The same applies to Yakutia (they treat it as a single location, although in reality it's huge and has 3 moose subspecies). These errors make much of the data in the paper impossible to interpret.
>(Besides, the largest white-tailed and mule deer are actually not that much smaller than reindeer or caribou; a large northern white-tail buck may weigh 125-130 kg.)
I thought that that weight must be wrong, but the wiki agrees... I have seen caribou in person and I saw whitetails probably once a week growing up in Montana, and I say that caribou simply look "big" in a way whitetails don't. I am surprised that the top weights are so similar.
Alan:
That's correct. Molecular data (mtDNA in particular) suggest that all modern-day North American moose share a last common ancestor (to the exclusion of all thus far sampled Eurasian moose) that may have lived as recently as 15,000-14,000 years ago; Alces alces probably spread to North America somewhere around that time.
As far as I can tell, there are no such signs.
William:
Nitpick: Key deer are not the southernmost white-tailed deer; Odocoileus virginianus is distributed throughout Central America and has spread well into the northern parts of South America.
IIRC, wild boar chromosome number polymorphism was first discovered in the 1960ies in the US, among introduced animals. It has since been discovered in several native Eurasian populations. Arroyo Nombela et al. (1990), for example, found in their southern Spanish study population boars with three different kinds of chromosome number: 2N = 36, 2N = 37, and 2N = 38, respectively (and there were no obvious phenotypical differences between the animals).
Vladimir:
Well, it is a review paper. Did you look up the original references, especially G. G. Boeskorov's 1996 and 1997 papers? (I couldn't get access to those two, and they are in Russian, which I can read only with considerable difficulty.)
Kelly:
I agree, but looks are often deceptive. And visual size estimation of animals, in particular, can be surprisingly tricky; many of us have - unconsciously - preconceived notions about how big, or how small, certain animals 'should' be.
Reference:
Arroyo Nombela, J.J., Rodriguez Murcia C., Abaigar, T. & Vericad, J.R. 1990. Cytogenetic analysis (GTG, CBG and NOR bands) of a wild boar population (Sus scrofa scrofa) with chromosomal polymorphism in the south-east of Spain. Genetics, Selection, Evolution 22, 1-9.
On chromosomal polymorphism in wild boar, it should be pointed out that the polymorphism seems to be taxonomically or phylogenetically 'specific': it is not random within populations as perhaps implied above. So, the range of chromosomal variation present in Spanish boars (2n = 36, 37 or 38) - also seen in, for example, boars in the Piedmont region of Italy - probably reflects the fact that the region has been artificially stocked with animals brought in from diverse, far-flung populations (Macchi et al. 1995). West European boar seem to be 2n = 36, eastern European ones are 2n = 38, and central Asian and far east Asian ones includes both 2n = 36 and 38 populations. Domestic pigs are 2n = 38.
I was originally hoping that this variation might partition neatly among boar subspecies, but it doesn't: Sus scrofa scrofa alone, for example, has populations with 36, 37 and 38 chromosome pairs; S. s. lybicus of south-eastern Europe, Turkey and the Nile Delta has 38 pairs across most of its range but 37 in Azerbaijan; and S. s. nigripes of the Tienshan region has 36 or 37 pairs (Groves 1981).
Refs - -
Groves, C. 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.
Macchi, E., Tarantola, M., Perrone, A., Paradiso, M. C. & Ponzio, G. 1995. Cytogenetic variability in the wild boar (Sus scrofa scrofa) in Piedmont (Italy): preliminary data. Ibex J.M.E. 3, 17-18.
>>Key deer are not the southernmost white-tailed deer; Odocoileus virginianus is distributed throughout Central America and has spread well into the northern parts of South America.
Oops, yes, that's true.
I wonder if the tropical ones are similarly small?
White-tails "increase in size both north and south of Middle America" (Geist 1999, p. 268), so the Florida Key deer is indeed one of the smallest (mature males = c. 36 kg). The Coiba Island White-tailed deer Odocoileus virginianus rothschildi might be smaller. About 16 subspecies have been named for the white-tails that range from Texas to Venezuela and most are similar in size to the white-tails of the northern USA; South America does, however, include particularly large forms, like O. v. gymnotis from the Venezuelan and Guianan highlands (c. 70 kg), as well as particularly small ones, like those in coastal Peru (25-30 kg). The amount of variation within white-tailed deer is pretty staggering... as it is in so many widespread big mammals :)
BTW...
That's spelled cm³. Yes, officially. I even have ² and ³ on my (German) keyboard (AltGr 2, AltGr 3).
That's awesome, and has major implications for human evolution.
BTW, I hope it's libycus rather than lybicus, but I'm pretty sure whatever the original spelling is has to be preserved in this case.
Darren:
Wait, what? I saw that Macchi et al. do indeed make that claim in their paper, but they don't provide any actual support for it!
Rejduch et al (2003) reported a case from southwestern Poland where all three different chromosome numbers were present in the same five-piglet litter. (One piglet had 2N = 36, three had 2N = 37, and one had 2N = 38.)
Reference:
Rejduch, B., SÅota, E., Różycki, M. & KoÅcielny, M. 2003. Chromosome number polymorphism in a litter of European wild boar (Sus scrofa scrofa L.). Animal Science Papers and Reports 21, 57-62.
Sure, it's a hypothesis (I said that it "probably reflects the fact that the region has been artificially stocked with animals brought in from diverse, far-flung populations") - I had assumed that it was reasonably well established, given the known history of boar introduction in the Piedmont region. Wasn't aware of the Rejduch et al. study - this neatly screws with everything I said above, sigh...
Interesting exception to Bergman's Rule: Troodon formosus becomes larger the farther north it's found. The Colville River specimens are twice the size of Montana's. The Wapiti Troodons are somewhere in the middle of the two sizes. Interestingly, most of Alaska's other dinosaurs are smaller than their southern counterparts.
Dartian: I now remember meeting with Beskorov in 1996, when he presented his data at some conference. At the time I was working on Mammals of Russia field guide and was very interested in all possible taxonomic changes. I am pretty sure he looked only at chromosomal numbers and not at anything else, and had a tiny sample size from just two areas, European Russia and eastern Yakutia.
Open habitats? Hmmm... The Forest Reindeer is generally larger than the domestic one, but I'm not sure about the wild tundra reindeer.
Vladimir:
The non-palmate antler type is also common in Europe and apparently is increasing in frequency (although it varies with age, as well).
Sordes:
Interesting, they're not too dissimilar to these antlers if you imagine away the forward pointing branch.
Dartian:
"all modern-day North American moose share a last common ancestor (to the exclusion of all thus far sampled Eurasian moose) that may have lived as recently as 15,000-14,000 years ago; Alces alces probably spread to North America somewhere around that time."
So, anything large survived Pleistocene in N America?
@Jerzy
"So, anything large survived Pleistocene in N America?"
Bison and Muskox are both bigger than 'Moose' and predate the last Ice Age, I believe.
Beyond that, what do you mean by 'large'? And I assume you're talking about terrestrial mammals...
I believe muskoxen are actually quite a bit smaller than moose; according to the URL in my name (to avoid spam filter), the average is 250kg for females, 320kg for males.
Bison have been in North America through the Pleistocene, yes; but not always the same species -- and Bison latifrons and Bison antiquus were larger than modern Bison bison. So even bison aren't as big as they once were...
Jerzy:
South of the Laurentide Ice Sheet, yes.
William:
They are indeed. For me personally, the muskox is a perfect example of an animal that 'looked much bigger on TV'. I still remember when, at about the age of ten, I saw a (stuffed) muskox for the first time up close. I was surprised (and slightly disappointed) at how relatively modestly-sized it was; I had expected something similar in size to a bison.
Back to mammalian within-population chromosomal polymorphism; as I suggested earlier, it is apparently not particularly uncommon, and it has been recorded in mammals as diverse as shrews and okapis (for an incomplete list, see Rubes et al., 2008). It has been recorded in some cervids too, for example in the Chinese tufted deer Elaphodus cephalophus. (For a while, it was thought that this animal was sexually dimorphic in this regard, in that females would have 2N = 46-47, and males 47-48, respectively (Shi et al. (1991). A later study, however, found females with 2N = 48 (Cao et al. (2005).)
What this strongly suggests is that chromosome number is not necessarily a good indicator of species (or subspecies) affiliation, and that this is perhaps especially often the case in artiodactyls. Thus, taxonomic division of Alces alces on karyotypic grounds seems unjustified or at least premature.
References:
Cao, X., Jiang, H. & Zhang, X. 2005. Polymorphic karyotypes and sex chromosomes in the tufted deer (Elaphodus cephalophus): cytogenetic studies and analyses of sex chromosome-linked genes. Cytogenetic and Genome Research 109, 512-518.
Rubes, J., Musilova, P. & Mastromonaco, G.F. 2008. Cytogenetics of wild and captive bred non-domestic animals. Cytogenetic and Genome Research 120, 61-68.
Shi, L., Yang, F. & Kumamoto, A.T. 1991. The chromosomes of tufted deer (Elaphodus cephalophus). Cytogenetics and Cell Genetics 56, 189-192.
Briefly... wow :) Within these polymorphic species, do individuals breed willy-nilly with others, regardless of chromosomal number, or is there any kind of assortative mating?
Darren:
Short answer: We don't really know. It's a reasonable guess that there should be at least some cost to reproduction between individuals that differ in chromosome number (increased likelihood of miscarriage, etc.) - but what that cost is has not been sufficiently studied.
My comment got eaten... by Godzilla presumably. :(
Thank you for posting this. Whenever I saw a deer or a moose, I wondered why they had that bulge in their neck. Now I know that it for their calls. When I was reading this, I wondered, is the sac just for calls or for regular communication?