Monday, March 28, 2011

Groomed By A Vulture

Taken and modified from Wikipedia Commons.

American Black Vultures (Coragyps atratus) are remarkable opportunists. With meathook-like beaks adapted for hooking and slicing, they have the functional morphology of obligate scavengers (Hertel 1995)†, but they'll also take eggs, plant material, garbage, and live prey (Kauffman 2001). Groups have been observed preying on skunks and opossums (McIlhenny 1939) and even juvenile sheep and cattle (Humphrey et al. 2004). The frequency of livestock depredation isn't clear‡, as Avery and Cummings (2004) note that many supposed depredation events are inferred from vultures feeding on already-dead animals; vultures will aggressively pursue afterbirth (Humphrey et al. 2004), which raises the possibility that some 'attacks' are misinterpreted. I'm not attempting to acquit Black Vultures here, but their interaction with livestock clearly requires more study.

† Hertel (1995) doesn't show where C. atratus fits among the scavenger guild, but its extinct relative C. occidentalis tends to be towards the far end of variability. 
This doesn't stop some thousands of Black Vultures from being shot every year - along with hundreds of Turkey Vultures (Cathartes aura) which are not part of this problem (Lebbin et al. 2010). How are these daggers working by the way? I've heard the asterisks were hard to see. I'm also a bit worried when one paragraph will inevitably require three footnotes.

Based on Fig. 1 from Sazima and Sazima (2010).

Similar to the reported events involving livestock, ARKive has video of Black Vultures eating Capybara afterbirth and attacking juveniles, but the relationship between the species is not simple antagonism. Sazima (2007) reviewed video evidence from São Paulo which showed vultures pecking at resting Capybaras, visibly removing ticks and probable organic debris, and the giant rodents changing their posture to allow for a more thorough cleaning. The vultures were also observed to peck at sores (Sazima 2007), but it doesn't seem clear if this was a beneficial removal of necrotic tissue (as the author seemed to imply), or the vultures testing what they could get away with. As for how the association between Black Vultures and Capybaras was formed, Sazima (2007) suggested that the vultures would be familiarized with Capybaras from pecking at the sores and ectoparasites of dead or dying individuals, trying their luck with resting and healthy individuals, being denied when their behavior becomes harmful, learning to seek out resting Capybaras as a food source, Capybaras having advantageous health as a result of grooming, Capybaras adopting soliciting postures, and then cultural transmission in Capybara populations. Sazima and Sazima (2010) mentioned an interesting incident where a vulture picking off organic particles and ticks from a resting Capybara and later flew to a site 100 meters away to feed on a roadkill Capybara, supporting the proposed link between feeding on carrion and grooming (it would have been perfect if the order was reversed...).

Sazima (2010) recorded a remarkable incident involving Black Vultures in São Paulo preening an Irish Setter, the only known instance of cleaner birds interacting with a terrestrial carnivore. Sazima (2010) suggested that the Black Vulture-Dog association could roughly parallel the Capybara situation - the vultures locate the dog resting, spot organic debris in the dog's fur (possibly from rolling on carcasses), approach the dog and begin to feed on organic debris in its hair, and have the dog tolerate their activity until it felt disturbed or was hurt. The dog receptive towards grooming was also recorded to playfully interact with a group of vultures (Sazima 2010), making me wonder if the dog felt preening was play as well. It is unknown if this interaction is localized and/or rare, or if it has been overlooked due to its unpredictable nature and/or lack of attention (Sazima 2010).

Zamuro quitándole parásitos a un Caricare encrestado from Flickr user barloventomagico.

Intraspecific allopreening has been widely observed in birds (including vultures), however interspecific allopreening is a rarity, and has mostly been observed in cowbirds (Palmeira 2008 - citing various). Palmeira (2008) observed Black Vulture/Southern Caracara (Caracara plancus) grooming/preening in Mato Grosso do Sul, Brazil; the Caracara solicited with a head-down display, and subsequently the birds began to simultaneously groom one another. Similar events have been reported from Minas Gerais, Brazil (Souto et al. 2009) and Texas (Ng and Jasperson 1984). The above photo appears to show similar behavior in Venezuela. It would then seem probable that this behavior occurs wherever Black Vultures co-exists with Caracara plancus and C. cheriway, which would be everything from Tierra del Fuego to the southern US.

So why does this behavior occur? Ng and Jasperson (1984) suggest a parallel with cowbirds, which also use a head-down display, in that it could allow Caracaras to join a Black Vulture flock for feeding and roosting. Souto et al. (2009) further suggest that mixed flocks could have the benefits of increased surveillance, the ability of Caracaras to vocalize alarm calls would benefit Black Vultures, and the ability of Black Vultures to locate carrion would benefit Caracaras. I'm curious as to why Caracaras demonstrate this apparent social association-building behavior with Black Vultures and not Turkey Vultures, as the latter has also been observed to intraspecifically allopreen (Souto et al. 2009 - citing Harrison 1965) and is apparently better at finding carcasses (probably by olfaction), even buried ones (Smith et al. 2002). It's worth noting that Sazima (2007) suggested that the long and slender bill of Black Vultures, capable of tearing flesh from small carcasses and catching live insects, makes them excellent pickers and thus potential cleaners. I suspect, for whatever reason, Black Vultures have a propensity towards grooming and aren't particularly fussy about their clientele.

As for why Black Vultures don't go around grooming everything - say (to tie up loose ends) livestock - maybe only a few population in Brazil have learned that preening large mammals results in food. Alternately, Black Vultures could be preening everything that doesn't put up much of a fuss, but such incidents have yet to be recorded in the proper literature.


Avery, M. L. and Cummings, J. L. (2004). Livestock Depredations by Black Vultures and Golden Eagles. Sheep & Goat Research Journal 19, 58-63. Available.

Fisher, H. I. (1944). The Skulls of the Cathartid Vultures. The Condor 46(6), 272-296. Available.

Hertel, F. (1995). Ecomorphological indicators of feeding behavior in recent and fossil raptors. The Auk 112(4), 890-903. Available.

Humphrey, J. S., Tillman, E. A., and Avery, M. L. (2004). Vulture-Cattle Interactions at a Central Florida Ranch. Proceedings - Vertebrate Pest Conference 21, 122-125. Available.

Kauffman, K. (2001). Lives of North American Birds. Houghton Mifflin Harcourt.

Lebbin, D. J., Parr, M. J., Fenwick, G. H. (2010). The American Bird Conservancy Guide to Bird Conservation. University of Chicago Press.

McIlhenny, E. A. (1939). Feeding habits of black vultures. Auk 56, 472474.

Ng, D., and Jasperson, B. D. (1984). Interspecific Allopreening Between Crested Caracara and Black Vulture. The Condor 86, 214-215. Available.

Palmeira, F. B. L. (2008). Allopreening behavior between Black Vulture (Coragyps atratus) and Southern Caracara (Caracara plancus) in the Brazilian Pantanal. Revista Brasileira de Ornitologia 16(2), 172-174. Available.

Sazima, I., and Sazima, C. (2010). Cleaner birds: an overview for the Neotropics. Biota Neotropica 10(4), 183-194. Available.

Sazima, I. (2010). Black Vultures (Coragyps atratus) pick organic debris from the hair of a domestic dog in southeastern Brazil. Revista Brasileira de Ornitologia 18(1), 45-48. Available.

Sazima, I. (2007). Unexpected cleaners: Black Vultures (Coragyps atratus) remove debris, ticks, and peck at sores of capybaras (Hydrochoerus hydrochaeris), with an overview of tick-removing birds in Brazil. Revista Brasileira de Ornitologia 15(3), 417-42. Available.

Smith, H. R., DeGraff, R. M., and Miller, R. S. (2002). Exhumation of Food by Turkey Vultures. Journal of Raptor Research 36(2), 144-145. Available.

Souto, H. N., Franchin, A. G., and Júnior, O. M. (2009). New Records of Allopreening Between Black Vultures (Coragyps atratus) (Ciconiiformes: Cathartididae) and Crested Caracara (Caracara plancus) (Falconiformes: Falconidae). Sociobiology 53(1), 125-129. Available.

Saturday, March 12, 2011

Book Review: True Giants

All these books just sitting there, un-reviewed...

I was thrilled to learn that Mark A. Hall and Loren Coleman wrote a new book on True Giants. My copy of Mark A. Hall's self-published The Yeti, Bigfoot & True Giants (1997) was read and re-read to the point of near-disintegration, so I'm anxious to both have a more structurally sound tome on 'True Giants' and to see how the hypothesis has evolved. The concept of 'True Giants' goes Beyond The Impossible, postulating that there's a primate bigger than Bigfoot present on multiple continents, whose interactions with humans in the past caused the ubiquitous legends of giants, including those of the anthropophagus variety. The concept of a giant hairy entity following, competing with, and even culturally mimicking Homo sapiens is fascinating - and scary, I've had at least one nightmare about it - and probably a potential goldmine for speculative fiction. However, I am not convinced that 'True Giants' are a valid category of cryptid with the evidence presented.

Major Issues:

Folklore and Cryptozoology

Mezzotint etching of The Giant/The Colossus, by Goya (?).  From Wikipedia Commons.

The pursuit of locally known but officially undescribed species resulted in some of van Roosmalen's amazing discoveries, so I'd say the 'ethnoknown' aspect of folklore is very promising for (crypto)zoology.True Giants includes legends, fables, and traditions such as Grendel, the toll-demanding giant which gave Antwerp its name, and the anthropophagus Ai Kanaka from Hawai'i which I have no more reason to believe than Kings in Mountains, El Dorado, or the Flying Dutchman. Unless the folklore in question is recent (preferably within the lifespan of an eyewitness) and shows an in-depth and realistic understanding of a cryptid, I don't think it should be treated as anything more than a curiosity. As for why giants are ubiquitous in human culture, they can have symbolic purposes (the above etching possibly comments on the Peninsular War), heroic figures can become inflated in size* (Tolkien was probably aware of this trope when he made Elendil nearly 8 feet tall), A Book of Giants suggests they are often used in fables regarding wits over brawn, and of course I suspect there's a universal fascination with things that are big, powerful, and anthropomorphic.

* Went by the name of Homer. Seven feet tall he was, with arms like tree trunks. His eyes were like steel, cold, hard. Had a shock of hair, red like the fires of Hell.

Thorkild hos Udgaardsloke by Louis Moe. From Wikipedia Commons.

For the most part, True Giants treats folklore extremely literally. The foolishness of giants in fables is taken to indicate that 'True Giants' were stupider in the past and only recently learned to avoid humans. The ubiquity of legendary giants caused the authors to propose the presence of 'True Giants' on every permanently inhabited continent, as well as island groups such as Hawai'i and the Solomon Islands. 'True Giants', despite their alleged stupidity, are also postulated to have been capable of rafting (as implied by their presence on the aforementioned islands), speaking human languages as well as their own, herding animals, and the use of advanced technology such as smithing, thanks to legends. To me, this just screams that legendary 'True Giants' are Homo sapiens inflated in scale due to storytelling.

Legendary 'True Giants' up to 20 feet (~ 6) tall are taken literally, although one Chinese tale of a 50 foot (15.25 m) giant is conceded to be a probable exaggeration (thankfully). Many folk tales are full of bizarre traits such as "double eyebrow", "bludging red eyeballs", "eyes as big as saucers"*, "[head] drawn in somewhat like a terrapin", "only one leg or eye", backwards feet, and so forth which are not commented on. One legendary giant wearing a "little hat" is interpreted to have been a reference to a sagittal crest, despite giants wearing clothes (even belts) in other tales. It just seems really strange to me that the authors would cherry-pick some very strange straits, and ignore or explain away others.

* Probably physically impossible for a terrestrial creature.

Overall, True Giants has far too much emphasis on legends. I think folk-giants can be very interesting, so long as they are not taken to indicate flesh-and-blood creatures and analyzed in Folkloristics rather than cryptozoology.

Estimating Giants

Consider Leonid Stadnyk, who claims to be 2.54 m (8' 4") tall - and was once given the title of the world's tallest living man by Guinness - yet appears to be of surprisingly modest height* when a person verified to be that size is shown standing next to an already tall person. The point is - Stadnyk almost got away with considerably exaggerating his height despite being photographed extensively, which suggests to me that the average person is terrible at estimating heights a few standard deviations outside of the norm. This creates huge problems for the concept of 'True Giants' which, aside from their alleged unusual foot morphology, are distinguished from other cryptid hominids by being at least 10 feet (~ 3 m) tall. Am I to seriously believe that a 9 foot 'Neo-Giant' and 12 foot 'True Giant' can be readily distinguished by a height estimated by eyewitnesses who got a cursory glance and (usually) no frame of reference? I only managed to find 2 references to feet with four toes being connected with a height - one 22 inch foot supposedly belonged to an 8 foot creature and a 20 inch foot was supposedly from a 12 foot creature. Assuming the tracks and sightings have any basis in reality, it would suggest that eyewitnesses are capable of grossly inaccurate estimates.

* The man he is standing next to is former Ukrainian president Viktor Yushchenko, who is about the same height as George W. Bush, and thus probably around 6' or 1.83 m.

Taking measurements from cryptid sightings literally is a potential minefield. I see no reason to classify a creature as a 'True Giant' based on alleged height alone, which means most of the observations have no business being classified so specifically. Oh yeah, and there's also the problem of an undiscovered species attaining a height of 20 feet (6.1 m) - which is of course taller than the record giraffe.

Four-Toed Tracks

I was hoping this was a reference to True Giants in mainstream TV-land. Alas, it's yet another inexplicable and ultimately unimportant mystery.

By far the most interesting evidence presented for 'True Giants' are tracks with only 4 visible toes. I counted 14 reported cases in True Giants, with most being reported from western North America (Washington, Oregon, Idaho, British Columbia, Alberta, Manitoba), but also eastern North America (Pennsylvania, Mississippi), Central Asia (Tajikistan), and Southeast Asia (Indonesia, Malaysia). They range in length from 14 to 31 inches (n = 14, median = 20", mode = 20", average = 21", stdev = 5") and in width from 6 to 17 inches (n = 8, median = 9", mode = 6", average = 10", stdev = 4"). Unfortunately, only 3 of the tracks have been depicted (2 of which are in Mark A. Hall's prior book): the 30" x 13" track from Johor has very round toes in a slightly sloping line and tapers into a pronounced heel; the 19.25" long Tajikistan track seems to have  a more rounded heel and pronounced sloping toe-line; the 15" x 6" Mississippi track seems to have a very strait toe-line and round heel (as well as a possible projection from the side, where an opposing ape-like hallux could be). As for how the length and width compare, it isn't a particularly great trend.

I would have preferred it if the authors documented all of the known 4-toed tracks. Are there casts? Is there similar overall morphology? If there evidence of dermal ridges or differing depths within the track which would be difficult to fake? The tracks are potentially very interesting, but ultimately left very mysterious by the book.

It's noteworthy that 10 other footprints were mentioned where the number of toes is not mentioned; these appear to have been connected to 'True Giants' due to their size and location - even though you'd think 4 toes would be one of the first things mentioned. One report from Ballachulish, Scotland specifically mentions toes, but not the number. I found two instances where legends stated that the toes of the giants were "normal" and none mentioned an odd number, demonstrating the tenuous connection between legendary giants and 'True Giants'.


Gigantopithecus blacki mandible, from Wikipedia Commons.

The book suggests that True Giants are surviving Gigantopithecus, although offer contradicting opinions on how closely related they are to humans. Compare the contents of page 8:
[T]he fossils that have been found for this particular giant primate have been attributed not to a giant man but, erroneously, to a giant ape. There is no basis in the fossils themselves to support this determination. Rather, it has been merely a popular prejudice among the fossil specialists to make this categorization.
With those of page 101:
Gigantopithecus is a distant relative to humans in the scheme of primate evolution. Nevertheless, True Giants appear to have discovered and learned the characteristics familiar to other successful primates known as hominids. This convergence accounts for these apemen being seen by so many cultures around the world as "Big Men."

The authors appear to be under the impression that Gigantopithecus was preferred over Gigantanthropus since it is now universally viewed as an ape. Even if a taxa is re-interpreted phylogenetically the name stays the same - consider Basilosaurus. Junior synonyms cannot be re-used, so even if a giant man-like ape is discovered (that isn't Gigantopithecus) it can't be called Gigantanthropus - consider Livyatan melvillei and the pre-occupation of Leviathan.

I have never seen Gigantopithecus classified as anything other than a relative of orangutans in recent years, see Harrison (2010) for a recent phylogenetic tree of apes.

Big Bones

'True Giant' bones have a suspicious tendency to crumble away into nothingness, and those that found their way to scientists 'mysteriously' shrink to normal human proportions - see NABR #11 (page 5) for an article on how the decaying tendons and cartilage of normal skeletons made them appear 8 or 9 feet tall, and NABR # 13 (page 3) on how normal human femurs and mandibles have been confused for those of giants, not to mention when bones from large mammals (like mammoths) are confused for those of a human. Therefore, there is absolutely no reason to trust reports of 'giant' bones.

Minor Issues:


To segue into 'True Giants', the introduction (pg. 5-6) brings up a mysterious clade of humans distinct from Homo sapiens and H. neanderthalensis yet sharing genes with both, and suggests they are linked to cryptid Siberian wild-people much in the manner that H. floresiensis is 'linked' to the legendary Ebu Gogo. I feel obliged to comment that the 'hobbit'/Ebu Gogo connection could be a coincidence (legendary 'little people' are found far outside Flores), and connecting a clade described only from molecular data with cryptids known from anecdotally-reported morphology is very premature. In the mad mad mad world* of human origins, it's hard to predict what picture will emerge for the Denisovans (or what else will emerge...), so in the meantime, check out John Hawks Weblog for the story so far.

* The closer to Homo sapiens phylogenetically, the crazier things get.


The authors refer to Dryopithecus as a relative of Gigantopithecus - which is technically true of course - but there is some controversy as to where Dryopithecus places phylogenetically, and it could be a stem hominid (outside the African ape + orangutan clade) (Harrison 2010). True Giants claims that Dryopithecus is behind 'Yeti' sightings, yet Dryopithecus is exclusively European (Begun 2005). Since it would have made a lot more sense just to say Sivapithecus instead of Dryopithecus, I suspect True Giants was relying on older literature that combined them into a polyphyletic Dryopithecus (see Begun 2005 for a review). I'd recommend Grehan and Schwartz (2009) as a review on fossil apes... if you overlook the proposed phylogeny.

Shrink-wrapped skull

True Giants claims that a skull-mask from the Mongolian plateau represents a 'True Giant' head. They claim that it has an overall oval-shape, deep-set eyes, and "a peak that is an indicator of the large muscles necessary to operate the massive jaw of this ape-man" (which they connect to the "little hat" giants of Alaska). Note that the skull doesn't have a sagittal crest (which provides an attachment point for jaw muscles), it has a rounded top. How one determines that a representation of a skull has "deep-set" eyes is beyond me, and the interpretation of traits (seen a few times in 'True Giants') comes across as rather forced. A shrink-wrap reconstruction of the skull-mask serves as a logo of sorts for the start of each chapter.


I have no idea what this paragraph is about (page 99):
The mean height of True Giants is likely to be in the range of 12-14 feet. This was determined by Lambert Adolphe Jacques Quetelet (1796-1874). This Belgian statistician and astronomer made his judgement based upon the proposed existence of a 20-foot giant [1].
The reference links to Firestone's The Coasts of Illusions. How could this average be determined from one (proposed!) skeleton? Why is this more reputable than averaging the sightings listed?

Such a statement seems especially designed to bait me into going through the book again and documenting all the described heights. So I did. For sightings with given heights (n = 19), the range was from 8-18 feet with a median and mode of 12 feet, and an average of 11.96 feet (stdev = 2.64 feet). When only sightings with toes are considered, the 'n' plummets to 2 - one of an 8 foot creature and one of a 12 foot creature (with the former having larger feet...). For what I consider 'legends' (n = 14), the range was from 9-50 feet with a median of 19 feet, mode of 20 feet, and an average of 20.23 feet (stdev = 11.16 feet). No 'legend' mentioned four toes.

Honeycombed Bones
From Wikipedia Commons.

The authors suggest that since humans can't grow over 9 feet tall, 'True Giants' must have a radically different skeletal structure to allow them to accomplish such towering heights. They raise the possibility of bones with a "honeycomb structure" which could be used to reduce mass, as well as account for why there are so few remains. I'm not sure what is meant by "honeycomb". Cancellous bone is weak, so increased extents of it would make for a rickety giant. Pneumaticity (i.e. the presence of air) is a way of reducing weight and retaining strength which is found in across tetrapods - notably the hyoid of howler monkeys (Alouatta) (Wedel 2005); however, only pterosaurs, theropods (including birds), and sauropods have pneumaticity beyond the cranium (Wedel 2006). I'm going to say that 'True Giants' having a skeletal structure (and presumably respiratory system) convergent upon archosaurs is really, really improbable.

Executive Summary:

While a tantalizing concept, there's no evidence to support 'True Giants' as a valid cryptid. Folklore could have made for a few interesting footnotes or background to some sightings, but it was given far too much emphasis and taken too literally. Most encounters appear to have been classified as 'True Giants' based on the size reported by eyewitnesses; it is extremely unlikely an eyewitness can accurately gauge how tall a cryptid far beyond normal human size is - and since when does another proposed cryptid ('Neo-Giants') have a known size limit? The large four-toed tracks are by far the most interesting part of True Giants, but remain cryptic even in this hyper-specific volume. Future volumes desperately need to document the footprints to the greatest extent possible - preferably gathering casts and analyzing the possibility it came from a living creature. I should add that I would bet against the possibility of 'True Giants', 'Bigfoot', et al. existing, but that doesn't mean I think they deserve to be ignored, and I'd be willing to change my mind if sufficient evidence turns up.

True Giants: Is Gigantopithecus Still Alive? is available at Amazon, Barnes & Noble, and Books-A-Million. I'm mentioned on page 157 (in a discussion on Meganthropus) and Markus Bühler is on page 71 (he took a photograph of an unusual orangutan-like sculpture).


Begun, D. R. (2005). Sivapithecus is east and Dryopithecus is west, and never the twain shall meet. Anthropological Science 113 (1), 53-64. Available.

Grehan, J. R., and Schwartz, J. H. (2009). Evolution of the second orangutan: phylogeny and biogeography of hominid origins. Journal of Biogeography 36 (10), 1823-1844. DOI: 10.1111/j.1365-2699.2009.02141.x. Available

Harrison, T. (2010). Apes among the Tangled Branches of Human Origins. Science 327 (5965). DOI: 10.1126/science.1184703. Available

Wedel, M. J. (2006). Origin of postcranial skeletal pneumaticity in dinosaurs. Integrative Zoology 1(2), 80-85. DOI: 10.1111/j.1749-4877.2006.00019.x. Available

Wedel, M. J. (2005). Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates; pp. 201-228 in Wilson, J.A., and Curry-Rogers, K. (eds.), The Sauropods: Evolution and Paleobiology. Berkley: University of California Press. Available.