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Crocodiles of Africa, crocodiles of the Mediterranean, crocodiles of the Atlantic (crocodiles part VI)

The views expressed are those of the author and are not necessarily those of Scientific American.


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Bust of Sobek, the crocodile-headed god, photographed in Oxford by Graeme Churchard. Image licensed under Creative Commons Attribution 2.0 Generic license.

The Tet Zoo crocodile series is not yet finished, and here we embark on part VI in the series (see below for links to previous parts). This time, we come to the Nile crocodile lineage, and I refer here to a ‘lineage’ rather than to a species since there’s now good evidence that C. niloticus of tradition is not a single taxon [adjacent image by Graeme Churchard]. Actually, however, it now seems that the crocodiles we’re talking about here aren’t even members of the same single lineage, so even that term is probably incorrect. If you’ve read the previous articles you’ll know that Crocodylus crocodiles are found in some phylogenetic studies to consist of three main lineages: an Indopacific assemblage, a New World assemblage, and an African Nile crocodile lineage. Most studies find the Nile crocodile to be closer to the New World assemblage than to the Indopacific one.

Because numerous African Cenozoic fossils have been identified as archaic members of Crocodylus, it has generally been assumed that the members of the Nile crocodile lineage evolved in situ, and hence that early members of the New World assemblage crossed the Atlantic from east to west after originating from an African ancestor.

Skulls of C. niloticus (above) and C. anthropophagus (below), by Chris Brochu. C. anthropophagus is one of those 'horned' crocodiles.

However, those ‘archaic Crocodylus’ crocodiles now turn out to be no such thing. They are, in fact, mostly or entirely members of the Osteolaemus group. As Brochu et al. (2010) hinted in their description of the Plio-Pleistocene C. anthropophagus from Olduvai Gorge (and see Brochu 2000), the possibility now exists that the members of the Nile crocodile lineage are relative newcomers to Africa that moved in from elsewhere. Further study is required to test this idea. Incidentally, C. anthropophagus is not a member of the Nile crocodile lineage – it was found instead to be in a polytomy with a Nile crocodile + New World assemblage clade, the Indopacific assemblage, and the fossil species C. palaeindicus (Brochu et al. 2010).

Crocodylus niloticus’ is not monophyletic

Bipedal croc! This image - taken in Bazoule, Burkina Faso - is labelled 'sacred crocodile', so might depict C. suchus. Image by Marco Schmidt, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

The substantial variation seen within C. niloticus across its enormous range has resulted in the naming of seven subspecies (C. n. niloticus Laurenti, 1768, C. n. africanus Laurenti, 1768, C. n. chamses Bory de Saint-Vincent, 1824, C. n. cowiei Smith in Hewitt, 1937, C. n. madagascariensis Grandidier, 1872, C. n. pauciscutatus Deraniyagala, 1948 and C. n. suchus Geoffroy Saint-Hilaire, 1807). Furthermore, the subspecies originally named for populations in Egypt, Sudan, Nigeria, Madagascar, South Africa and elsewhere were originally described as distinct species [adjacent image by Marco Schmidt].

While the phylogenetic reality of some of these taxa has yet to be confirmed, molecular results published since 2003 have shown that crocodiles typically classified together in C. niloticus are genetically diverse, with initial studies showing that ‘west African’ crocodiles (occurring as far east as Chad) are notably distinct from east African ones (Schmitz et al. 2003). Given that the name C. niloticus has been specifically associated with crocodiles from Egypt, it’s the west African ones that need a ‘new’ name, and C. suchus Geoffroy, 1807 was resurrected for this purpose by Schmitz et al. (2003, 2004). As discussed in part V of this series, one especially problematic researcher has recently suggested that this species deserves its own ‘genus’, Oxycrocodylus. This is an unfounded suggestion that we should ignore.

Schmitz et al. (2003, 2004) found that west African crocodiles from Mauritania grouped together with Chadian animals, and they also regarded the ‘Nile crocodiles’ of Gambia and Senegal as part of the same taxon (C. suchus) as well. A ‘tidy’ picture of C. suchus in the mostly arid west and north, and C. niloticus in the east and south therefore emerged. However, complication # 1 is that crocodile fossils, archaeological specimens and rock art featuring crocodiles are present right across the whole northern half of Africa. Complication # 2 is that things ain’t so tidy after all, with C. suchus being far more widespread than thought in 2003 or 2004. Read on.

‘Sacred crocodiles’ of the Sahara, Sahel and Nile

Image labelled as C. suchus from carnivora forum. A specimen of C. suchus is apparently on display at the St. Augustine Alligator Farm Zoological Park. The individual shown here is in captivity and hence might be that specific animal. Anybody know?

These west African, C. suchus-type crocodiles were first mentioned by French explorer Henri Duveyrier in 1858 following his discovery of crocodile tracks in the Sahara, and live specimens were reportedly captured in 1910 and 1924 (Guggisberg 1972, de Smet 1999). Various explorers, naturalists and biologists reported small, Saharan or Sahelian crocodiles from the Hoggar Mountains of Algeria, Matmata in Tunisia, Tibesti Mountains of Chad, the Tagant and Ennedi plateaus of Mauritania and other west and north African localities during the following decades, so a general pattern of crocodile presence across this region gradually emerged (Guggisberg 1972, de Smet 1999).

It’s generally thought that these C. suchus populations are, or were, relicts, hanging on in small habitat pockets while the previously green environment around them degraded and disappeared. This fits, of course, with the whole ‘Green Sahara’ model supported by palynological, sedimentological and archaeological data: the Sahara was big and arid during the Last Glacial Maximum of the Pleistocene, but it was a green, wooded, well-watered place about 7000 years ago. The Sahel then developed about 5500 years ago, creating an arid belt that cut northern African off from the greener south. The arid belt expanded and moved over the next few thousand years.

Mauritanian crocodile photographed at guelta Legleyta (actually, in a cave 8 m below ground). Image from Brito et al. (2011), use licensed under CC.

These Saharan and Sahelian animals are small (always less than 2.3 m long* in total). A few morphological differences might allow them to be distinguished from C. niloticus, including robust snout proportions and a low number of belly scales.

* This apparent maximum length is based on a specimen collected by Paul Spatz from Lake Galula (“a desert pool at the foot at an impressive cliff”), Mauritania (Guggisberg 1972).

Their restriction to small habitat pockets makes them vulnerable to extinction and, sadly, they are often killed by people. de Smet (1999) drew attention to the fact that they had seemingly been extirpated from many areas where they had persisted until recently. They seem to have disappeared from Morocco by the 1960s, Tunisian crocodiles apparently persisted to as recently as the 1970s, those from the Tagant Hills in Mauritania had apparently gone extinct by 1996, and attempts to find them in some of their last strongholds in the Ennedi plateau of Chad were unsuccessful during the 1970s and 80s. de Smet (1999) concluded that “on balance one may conclude that the population of Saharan Nile crocodile are virtually extinct” (p. 84).

A Mauritanian crocodile killed by people at Dar Salam village, from Brito et al. (2011). Image use licensed under CC.

However, these western and northern crocodiles are secretive, poorly known, and typically occur in remote places rarely visited by people. Accordingly, it’s possible that they still inhabit places that haven’t been that well studied. This is exactly what Brito et al. (2011) found. In Mauritania alone, they reported crocodiles in 78 localities, increasing the number of known crocodile localities by 35%. However, while we can say that crocodiles persist in Mauritania, Chad and also Egypt, the numbers concerned are small: at most places only one or two animals are ever recorded. Tracks and dead crocodiles found away from water indicate that the animals can disperse between at least some of their strongholds, perhaps suggesting that these many small groups can be considered part of the same breeding population (Brito et al. 2011). Observations show that these animals are secretive and hide as soon as they see humans. Nevertheless, continuing human persecution occurs across much of this range. People deliberately kill the animals on sight, pulling them from the water and beating them to death.

Crocodile distribution across north Africa, as illustrated by Brito et al. (2011). Image use licensed under CC.

Here’s a good question: are all of these crocodiles all members of C. suchus? Brito et al. (2011) didn’t even mention this name and referred to all of their crocodiles as C. niloticus. Furthermore, if crocodiles were formerly ubiquitous and continuously distributed across north-western, northern, and north-eastern Africa, where did the ranges of C. suchus and C. niloticus end and begin? Did these species occur in sympatry? Has C. suchus always been restricted to the north and west, or was it once more widespread? Did C. niloticus previously occur in the north and west as well, and are all recent and modern northern and western crocodiles definitely C. suchus and not C. niloticus?

CT scan of a crocodile mummy (actually, more than one crocodile is present: look at the animal's back) provided by the Phoebe A. Hearst Museum of Anthropology, UC Berkeley. CT data acquired by Dr. Rebecca Fahrig, Department of Radiology, Stanford University, using Siemens SOMATOM Definition, Siemens Healthcare. Image rendered by High Definition Volume Rendering® engine (Fovia, Inc). Image from wikipedia, released for unrestricted use.

At this stage we can’t answer all of these questions. However, Hekkala et al. (2011) looked at the DNA of mummified crocodiles from Egypt with these issues in mind and showed that individuals of C. niloticus and C. suchus were both present in the sample. They concluded that both species occurred sympatrically in the Nile, and noted Geoffroy Saint-Hilaire’s opinion of 1807 that the distribution of C. suchus “likely extended into the western Sahara” (Hekkala et al. 2011, p. 12). It seems that the ancient Egyptians knew of these two distinct kinds of crocodiles. C. suchus – referred to as the ‘Sacred crocodile’ by Geoffroy Saint-Hilaire – was regarded as a smaller, more docile animal, and nowhere near as formidable as C. niloticus.

In and around the Mediterranean, and the Tarasque as a French crocodile

Our questions about the species-level identification of north African crocs also affects the animals that inhabited the Mediterranean. Waitaminute… crocodiles in the Mediterranean? Believe it or don’t, historical records refer to the presence of crocodiles on Sicily (Anderson 1898, de Smet 1999) and also in Syria, Jordan and Israel (Anderson 1898, Guggisberg 1972, de Smet 1999). In fact, they were still present in the Kebara swamps in Israel until the early part of the 20th century.

If all of these records are real (it mostly depends on whether you trust Anderson as a source or not), they could show that crocodiles lived around the southern and eastern coasts of the Mediterranean until surprisingly recent times.

Tarasque carnival float. Spiky carapace, human-like face, flowing mane... yup, definitely based on a crocodile (sarcasm). Image from wikipedia and in public domain.

de Smet (1999) went even further with this and wondered whether crocodiles might have been present in the river deltas and swamps of France, Spain and the Balearic islands until the “the first centuries of our era” (p. 84). A particularly weird mythological entity – the Tarasque – has been suggested on occasion to be based on garbled, distorted accounts of crocodiles encountered in the French wilderness (Lavauden 1926). That might seem hard to accept if you know what the Tarasque is meant to look like, since it’s described as having a giant spiked carapace, six limbs, a golden flowing mane, and a long, snake-shaped tail, but the problem with the Tarasque is that it’s so weird that it’s hard (if not impossible) to match it with any known creature. I’m certainly not convinced that it’s based on sightings of crocodiles, but it’s an interesting idea.

If these alleged Mediterranean crocodiles really were living in coastal places and making sea crossings, it might seem more likely that they were C. niloticus rather than C. suchus. However, Hekkala et al. (2011) showed that C. suchus most likely underwent at least some marine dispersal during its history, since they found good evidence linking Sahelian populations to coastal populations of Senegal and Gambia as well as to those of the Upper Guinea Forest Basin countries (Nigeria, Ghana and so on… more on this view of a super-widespread C. suchus in a moment).

As for whether crocodiles were really present in France, Spain, Sicily and elsewhere in and around the Mediterranean but a few hundred years ago, bring on the discoveries of bones and such required to support this view. Old eyewitness accounts are suggestive, but not good enough to be convincing.

Crossing oceans and how it gets more complicated

Crocodylus niloticus... you knew this from the dorsal scute pattern, right? Image by MathKnight and Zachi Evenor, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

Until very recently it was assumed that C. niloticus (in the strictest, most restrictive sense) and C. suchus are sister-taxa, in which case their recognition as distinct ‘species’ is subjective and depends on how your ‘species-o-meter’ is calibrated [Adjacent C. niloticus image credited to MathKnight and Zachi Evenor].

Hekkala et al. (2011) found crocodiles from across western Africa (Republic of Congo, Uganda, Gambia, Senegal, Mauritania, Burkina Faso, Ivory Coast, Ghana, Democratic Republic of Congo and Nigeria) to group together in a so-called ‘western clade’. Given that this clade includes crocodiles from Mauritania and is stated several times in their study to include the relict populations of the Sahara, this clade is either synonymous with, or includes, C. suchus.

The presence of these sorts of crocodiles in the Kidepo Valley of Uganda means that thinking of them as Saharan relicts, or as western specialities, is perhaps erroneous. Even more surprising is that Hekkala et al. (2011) referred to the possible presence of ‘western clade’ crocodiles in Ethiopia, potentially meaning that “the western clade is still distributed in this region though it may be restricted to marginal habitats” (p. 4212).

Simplified cladogram of Crocodylus crocodiles showing one possible topology for the clade. Photos (top to bottom) by Mo Hassan, Davric, from carnivora forum, Herbert Ponting, Dave Hone, Naish, Wilfried Berns. Image of New Guinea crocodile (icon for 'reduced' Indopacific assemblage) licensed under Creative Commons Attribution-Share Alike 2.0 Germany license.

The biggest surprise of Hekkala et al. (2011), however, is their finding that this ‘western clade’ does not group together with C. niloticus. Instead, the ‘western clade’ was recovered as the sister-group to the clade that includes both the New World Crocodylus assemblage and C. niloticus. The same pattern of relationships had previously been recovered by Meredith et al. (2011); Oaks (2011) also published evidence in support of it. This means that the New World assemblage is bracketed on both sides by African taxa: a topology which means that an African ancestry for the New World assemblage is arguably better supported than it was before (the idea that a trans-Atlantic crossing occurred in crocodile evolution is pretty well established). However, things are now more interesting.

As mentioned above, Hekkala et al. (2011) found most west African Crocodylus populations – not just the Saharan and Sahelian relicts – to belong to the ‘western clade’, with the mostly eastern populations of Egypt, Uganda, Kenya, South Africa, Malawi, Zimbabwe, Tanzania and Madagascar forming a different clade. I say “mostly eastern” because populations from Gabon were also included in the ‘eastern’ clade. Note also that Uganda seemingly included both members of the ‘western’ and ‘eastern’ clades (Hekkala et al. 2011). If you recall that the New World assemblage forms the sister-group to the ‘eastern’ clade, one possibility is that the African crocodiles that crossed the Atlantic to give rise to the New World assemblage actually left Africa from the east (= Indian Ocean) side, not from the ‘logical’ west (= Atlantic) side. And there’s no indication that the ‘eastern’ crocodiles in the west (like those of Gabon) have a special relationship with the New World assemblage.

Wow, aren't crocs just awesome? A high-walking C. niloticus (with weirdly prominent dorsal scutes). Image by Vicky Baldwin, licensed under Creative Commons Attribution-Share Alike 2.0 Generic license.

An idea put forward in interviews and news articles featuring Ekon Hekkala (like this one from September 2011 at Ed Yong’s NERS) is that east African crocodiles used one of the currents that flows through the Mozambique Channel and around South Africa in a south-westerly direction. From here, they got into the Atlantic and obviously dispersed east to west. Incidentally, all of this is thought to have happened within the last 6 million years: it would mean that the New World assemblage is geologically young and would be in keeping with other work which shows that modern crocodiles are recently evolved animals (Oaks 2011), not old ones.

Another Mauritanian C. suchus, photographed at a spring in Chegg el Maleh, and surrounded by hundreds of Hoplobatrachus frogs. From Brito et al. (2011), licensed under CC.

With C. suchus (and/or all ‘western clade’ crocodiles) being ancestrally African and ‘eastern’ C. niloticus being African too, the idea that the New World assemblage came from Africa is unavoidably obvious and parsimonious. However, parsimony isn’t always the same thing as reality when it comes to phylogeny. It’s (err, arguably) at least worth considering the possibility that things happened the other way round: that is, with C. niloticus being the descendant of an immigrant lineage that comes from the Americas. The fact that C. niloticus now seems to be mostly restricted to the eastern side of Africa counts against this idea. The presence of other modern crocodile groups in Asia and Australasia also suggests that crocodiles might have spread across the eastern side of Africa before moving across the western side.

The problem, though, is that we’re basing all of this on modern populations. That C. niloticus population in Gabon (Hekkala et al. 2011) hints at the possible former presence of C. niloticus throughout coastal western Africa. If that’s true we might need to reconsider the idea that the New World assemblage represents dispersal from a population that originated on the Indian Ocean coast of Africa.

An increasingly complex picture of crocodile evolution, history and dispersal is emerging the more we learn, and it’s really exciting stuff.

For the previous parts in this series, see…

And for other Tet Zoo articles on crocodyliforms (and/or crocodylomorphs), see…

Refs – -

Anderson, J. 1898. Zoology of Egypt, Volume 1, Reptilia and Batrachia. Bernard Quaritch, London.

Brito, J. C., Martínez-Freiría, F., Sierra, P., Sillero, N. & Tarroso, P. 2011. Crocodiles in the Sahara Desert: an update of distribution, habitats and population status for conservation planning in Mauritania. PLoS ONE 6(2): e14734. doi:10.1371/journal.pone.0014734

Brochu, C. A. 2000. Congruence between physiology, phylogenetics and the fossil record on crocodylian historical biogeography. In Grigg, G. C., Seebacher, F. & Franklin, C. E. (eds) Crocodilian Biology and Evolution. Surry Beatty & Sons (Chipping Norton, Aus.), pp. 9-28.

- ., Njau, J., Blumenschine, R. J., & Densmore, L. D. 2010. A new horned crocodile from the Plio-Pleistocene hominid sites at Olduvai Gorge, Tanzania. PLoS ONE 5(2): e9333. doi:10.1371/journal.pone.0009333

de Smet, K. 1999. Status of the Nile crocodile in the Sahara desert. Hydrobiologia 391, 81-86.

Guggisberg, C. A. W. 1972. Crocodiles: Their Natural History, Folklore and Conservation. David & Charles, Newton Abbot.

Hekkala, E., Shirley, M. H., Amato, G., Austin, J. D., Charter, S., Thorbjarnason, J., Vliet, K. A., Houck, M. L., Desalle, R. & Blum, M. J. 2011. An ancient icon reveals new mysteries: Mummy DNA resurrects a cryptic species within the Nile crocodile. Molecular Ecology 20, 4199-4215.

Lavauden, L. 1926. Les Vertébrés du Sahara. Albert Guénard, Tunis.

Meredith, R. W., Hekkala, E., Amato, G. & Gatesy, J. 2011. A phylogenetic hypothesis for Crocodylus (Crocodylia) based on mitochondrial DNA: evidence for a trans-Atlantic voyage from Africa to the New World. Molecular Phylogenetics and Evolution 60, 183-191.

Oaks, J. R. 2011. A time-calibrated species tree of Crocodylia reveals a recent radiation of the true crocodiles. Evolution 65, 3285-3297.

Schmitz, A., Mansfeld [sic], P., Hekkala, E., Shine, T., Nickel, H., Amato, G. & Böhme, W. 2003. Molecular evidence for species level divergence in African Nile crocodiles Crocodylus niloticus (Laurenti, 1786). C. R. Palevol 2, 703-712.

- ., Mausfeld, P., Hekkala, E., Shine, T., Nickel, H., Amato, G. & Böhme, W. 2004. Erratum to the article Molecular evidence for species level divergence in African Nile crocodiles Crocodylus niloticus (Laurenti, 1786). C. R. Palevol 3, 177.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com!

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The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Cameron McCormick 9:35 pm 03/12/2013

    I’m certainly not convinced that it’s based on sightings of crocodiles

    I think it’s safe to say a legend where the monster is beaten by the power of prayer is probably useless as a source of zoological information. Coincidentally, some YECs have suggested the Tarasque is a Triceratops! My spin of the Phylogenetic Roulette wheel comes up Wayward Macrochelys :P

    Link to this
  2. 2. vdinets 9:54 pm 03/12/2013

    The sacred croc at Saint Augustine is certainly not the only one in captivity. There is one in Gatorama, also in Florida, and I’ve been told that a few more exist in the US.
    Recently there were rumors that juveniles of the two species can be told apart by stripe pattern; sacred crocs are supposed to have two prominent longitudinal stripes above each shoulder. I don’t think it’s been published.

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  3. 3. BilBy 10:19 pm 03/12/2013

    @vdinets – there’s a sacred croc at Gatorama?! That’s more or less down the road from me! Get in!
    What’s the story with Madagascar crocs? I heard tell of giving them specific status but not sure where.

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  4. 4. imhennessy 12:40 am 03/13/2013

    I’m pretty sure that, if Nile crocs evolved in Africa and American crocs are evolved from a population which crossed from Africa to the Americas, they would have crossed the Atlantic from East to West.

    If, after rereading both the second paragraph and my comment several times, I’m completely failing to make sense, I apologise and plead insomnia.

    Ivan

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  5. 5. Dartian 4:34 am 03/13/2013

    Darren:
    bring on the discoveries of bones and such required to support this view

    An old preserved skin of a crocodile from Sicily is supposed to exist in a private collection, according to Masseti (2009:18). Of course, how one could definitely tell that such a skin really did come originally from Sicily is another matter. (Masseti briefly discusses other historical records of Sicilian crocodiles on pp. 16-18 in his paper.)

    Reference:
    Masseti, M. 2009. In the gardens of Norman Palermo, Sicily (twelfth century A.D.). Anthropozoologica 44, 7-34.

    Link to this
  6. 6. naishd 5:17 am 03/13/2013

    Thanks for comments. Cameron (comment # 1): I honestly wouldn’t have thought the Tarasque worthy of comment here were it not for the fact that de Smet (1999) – in an excellent and authoritative review of north Africa/Mediterranean crocodiles – takes the ‘Tarasque = crocodile’ suggestion quite seriously. Besides the idea from wayward cryptozoologists and creationists that it described a ceratopsian, the idea that it referred to glyptodonts – that’s right, spiky-shelled glyptodonts from Europe – has also been mooted.

    vdinets (comment # 2): wow, didn’t know any of that, thanks. Incidentally, sorry for delay in emails. I cannot keep up but will respond asap.

    Bilby (comment # 3): there’s a population of modern crocodiles on Madagascar that have been DNA sequenced and clearly group close to east African populations of C. niloticus. They presumably represent a dispersal event across the Mozambique Channel: likewise for the Nile crocs occasionally reported from the Comores and elsewhere in the Indian Ocean. However, note that some Indian Ocean crocs (the recently extinct population from the Seychelles, for example) have turned out to be Saltwater crocs – see the relevant part of this series of articles. Back to Madagascar: a fossil population of animals labelled as C. robustus was previously thought conspecific with the living C. niloticus population there but is now known to be a distantly related member of the osteolaemine radiation; it’s now called Voay robustus.

    More to come…

    Darren

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  7. 7. naishd 5:22 am 03/13/2013

    imhennessy (comment # 4): I screwed up and have now corrected the error, thanks for pointing this out.

    Dartian (comment # 5): hey, good work :) Obviously I was unaware of Masseti (2009) until now. As regards working out whether that skin represents an animals that really lived on Sicily or not, it’s sometimes possible to use the isotopic signature of elements preserved within tissues to work out where the animal did its feeding and growing. The results are hard to get, hard to interpret, and often inconclusive though! Myself and colleagues have a manuscript in press where we did exactly this (with a cat, not a crocodile).

    Darren

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  8. 8. BilBy 5:50 am 03/13/2013

    @naishd – when I was lucky enough to be in Madagascar I was in love with the geckos and snakes and lemurs and ignored the crocs, thinking they were the same as the ones back across the Mozambique Channel. I’d be kicking myself if they were something special after all.

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  9. 9. Dartian 6:41 am 03/13/2013

    Darren:
    Obviously I was unaware of Masseti (2009) until now.

    Not so obviously, actually; I cited that paper and mentioned the alleged Sicilian crocodiles in a Tet Zoo ver 2 comments thread (the one about the Rekhmire tomb elephant) – and you even replied to that comment. But I suppose that even you can’t keep track of everything that’s been said on this blog. ;)

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  10. 10. naishd 6:56 am 03/13/2013

    Dartian – dammit, my crappy memory lets me down again! Yes, I must work harder to memorise all c. 6 million Tet Zoo comments :) Good call.

    ps – there aren’t really 6 million comments, but there are quite a few.

    Darren

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  11. 11. Jerzy v. 3.0. 7:35 am 03/13/2013

    There is one known captive C. suchus in Europe, off-show at Zoo Cologne. It has quite an interesting history, being exhibited in several European zoos as a Philippine Crocodile.

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  12. 12. Chabier G. 7:40 am 03/13/2013

    If only relictic Saharan crocs were a different species, it will be easy to understand. But, how did both lineages diverge so much, in sympatry, across Africa?. They are so similar, morphologically, that only genetics have proved there are two different species. Perhaps C. suchus is more specialised in a strict fish-based diet?, or each species is found in different microhabitats? e.g. Ponds vs streams, or different chemical composed waters.
    Among other zoological groups, e.g. bats, cryptovariation has been related with slightly different ways of hunting, roosting or feeding.

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  13. 13. Jerzy v. 3.0. 7:45 am 03/13/2013

    Off-topic of the day in reference to pterosaur crests :)
    http://www.bbc.co.uk/nature/21747494

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  14. 14. naishd 8:00 am 03/13/2013

    Beetle horns (re: comment 13)… yes, very off-topic, but very relevant to pterosaur cranial crests. You might recall statements made here at Tet Zoo (and in published work I’ve been involved in) where it’s said that pterosaur crests seemingly do not have/cannot have a significant aerodynamic effect. Neat stuff. Also explains flying reindeer.

    Darren

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  15. 15. ChasCPeterson 9:54 am 03/13/2013

    Hell yeah, crocs are awesome, and so’s this fascinating post. Sicilian crocodiles? That would be so cool.

    One question: in the following passage, is “allopatrically” correct?

    individuals of C. niloticus and C. suchus were both present in the sample. They concluded that both species occurred allopatrically in the Nile

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  16. 16. naishd 10:21 am 03/13/2013

    I’ve noticed that I keep getting allopatry and sympatry confused at the moment so, sorry, this is another dumb mistake that I’ll now go correct.

    Darren

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  17. 17. vdinets 10:24 am 03/13/2013

    BilBy: well, nobody has done any genetic testing on Gatorama croc, but back in 2011 they told me it was from somewhere in West Africa. Assuming, of course, that they still have the same one – I haven’t been there recently.

    ChabierG: we don’t even know how the two species avoid hybridization in areas of sympatry. AFAIK, there is no difference in mating season, vocalizations, etc.

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  18. 18. Heteromeles 10:48 am 03/13/2013

    I thought flying reindeer were about Amanita muscaria, but never mind. Different type of, ahem, aerodynamics. Neat non sequitur.

    As for the Tarasque and crocodiles, I’d suggest reading a bit more about St. Martha, who was supposedly the sister of Mary Magdalene (along with their brother, the 3d century St. Maximus), and who, after Jesus’ ascension, migrated to Avignon, where they became the ancestors of kings and ultimately the source of the holy grail in The Da Vinci Code. Churches dedicated to St. Martha have been in that area for over 1000 years, but do remember that most of the Holy Grail legend came out of the Medieval equivalent of a novel, and I strongly suspect the Tarasque had a similar origin.

    Seriously, if there were crocodiles in the marshes of Southern France in the 1st Century AD, the best explanation is that they were escapees from the local gladiatorial games. You can even guess the story–some entrepreneur brought them across from Africa, the local games sponsors didn’t want them, so Mr. Entrepreneur dumped them (as still happens) so he didn’t have to feed them.

    Link to this
  19. 19. naishd 10:54 am 03/13/2013

    Heteromeles: you’re recommending that people should read The Da Vinci Code? Really? :)

    Darren

    Link to this
  20. 20. Tayo Bethel 11:02 am 03/13/2013

    I might be jumping ahead a bit … but I’ve seen it mentioned that Cuban crocodiles once inhabited the Bahamas. Your’s truly is a curious Bahamian and would be very interested to know whether this is fact or fiction.

    Link to this
  21. 21. Heteromeles 11:16 am 03/13/2013

    @Darren:well, I’d say the evidence for the Tarasque being a Roman crocodile is at about the same level of research as Dan Brown’s magnum opus. The only serious point is to get the time right. While I can forgive medieval storytellers for getting their dates wrong and forgetting about the extent of the Roman empire, modern cryptozoologists really should pay attention to little things like dates, history, geography, that sort of thing. It’s not like Avignon hasn’t been settled for quite a long time, after all.

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  22. 22. vdinets 2:07 pm 03/13/2013

    Tayo Bethel: not just the Bahamas, but probably also Florida. Someone supposedly found Cuban croc haplotypes in American crocs from florida. I think David Rodrigues published something on this, but I can’t find that paper now for some reason.

    Link to this
  23. 23. Jerzy v. 3.0. 3:18 pm 03/13/2013

    I thought C. niloticus and suchus actually interbreed?

    [/silly mode]BTW, stories of free-living crocodiles are regular silly season stories in Poland. A crocodile would be brought illegally by pet trader or traveling circus from Russia and escaped. There were several summer stories in the recent years. Of course, lynxes, wolves and brown bears live in Poland, so the excitement value of a story of a large mammalian predator is rather low. [/silly mode]

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  24. 24. naishd 3:56 pm 03/13/2013

    On Cuban crocs and hybridisation… if you can wait until the next article in this series, all will be revealed! Yes, lots of confusing goings-on regarding hybrids and wayward populations…

    Jerzy (comment # 23): we have fairly regular stories about escapee crocodiles/alligators in the UK as well (do a google search for ‘Sandwell valley gator’ for proof). It might have become a fairly established bit of folklore, just like American sewer alligators. Some of the stories go back to the 1800s.

    Darren

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  25. 25. David Marjanović 4:00 pm 03/13/2013

    Given that the name C. niloticus has been specifically associated with crocodiles from Egypt

    Does it have a type specimen now? It used not to.

    part V of this series

    I just added a comment there: there is a non-crackpot who publishes without peer review.

    Matmata in Tunisia

    Tunisia!?!?! Awesome!!! …oh. Extinct. :-( :-( :-(

    the recently extinct population from the Seychelles

    :-( Oh well, they’ll come back…

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  26. 26. David Marjanović 4:03 pm 03/13/2013

    BTW, stories of free-living crocodiles are regular silly season stories in Poland.

    There was one in Austria, I think 2 summers ago.

    Link to this
  27. 27. Chabier G. 5:25 pm 03/13/2013

    In spain there are several real records, in Andalucia and the Canary Islands, I remember the case of a Nile croc run over by a car in a forest road not far from Sevilla, some years ago, it was a less than 2 m long individual.

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  28. 28. Mythusmage 6:39 pm 03/13/2013

    What about Mesopotamia?

    As to the Tarasque; in some stories the original was a sex maddened bull that was tamed by the faith of a local priest.

    Link to this
  29. 29. Metridia 2:33 am 03/14/2013

    Random musing: It’s interesting that the Sahara was green and wooded during the peak of the current interglacial, when temperatures were at a level we are only just arriving at today. Why might it not return to that state instead of the droughts and more droughts that everyone is afraid of for the vulnerable Sahel with climate change?

    Link to this
  30. 30. David Marjanović 8:49 am 03/14/2013

    Why might it not return to that state instead of the droughts and more droughts that everyone is afraid of for the vulnerable Sahel with climate change?

    It might. But that requires the West African rainforest to be above a certain size, so that there’s enough evaporation to provide for rain in the Sahara. We’re probably already below that threshhold.

    Also, evacuating Bangladesh and settling 140 million people (well, more by then!) in the Sahara sounds easier than it is…!

    Link to this
  31. 31. Heteromeles 10:08 am 03/14/2013

    I agree with David. If there’s enough rain forest, the Sahel gets wetter. The real problem is that the northern edge of the great deserts will get drier, and the northern edge is the Mediterranean.

    The one small ray of hope is that various Amazonian tribes have proved that it’s possible to plant a lot of rain forest trees, so if we can get people planting trees, the Sahel will bloom and they won’t have a massive humanitarian crisis on their hands. Since they reportedly are experiencing some economic growth despite all the wars, it’s possible.

    Link to this
  32. 32. Jerzy v. 3.0. 10:23 am 03/14/2013

    @29
    Actually, the easiest thing for Sahel people to do is to develop their economy a little, so they are not so dependent on small scale farming and pastoralism. Overgrazing contributed much to desertification of Sahara.

    Otherwise they might emigrate to Greenland, to work with Inuit on mining all the mineral riches emerging from under the permafrost. ;)

    Link to this
  33. 33. Jerzy v. 3.0. 10:25 am 03/14/2013

    More serious: Do Nile Crocodiles aestivate, or what they do in caves in Sahara during dry season? And how long they really can fast?

    Link to this
  34. 34. Heteromeles 11:23 am 03/14/2013

    @30: Actually, it appears that Africa is doing better overall:

    http://www.economist.com/blogs/dailychart/2011/01/daily_chart

    When looking at industrial growth, it’s always worth looking at places like South Korea, which was largely rural until the late 1960s. Growth can happen pretty quickly, for good or ill.

    Link to this
  35. 35. naishd 11:31 am 03/14/2013

    Within the context of that last comment (# 34), an interesting thing that some people have mentioned is that urbanisation/development can sometimes, indirectly be good for wildlife and the environment since people both end up staying in urban areas and cease heavy exploitation of the wild, and develop legal frameworks that encourage the protection of wild spaces. The history of the eastern US is a case in point: it was heavily deforested when people were rural, but 60% of original forest area had recovered by the 1970s.

    Darren

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  36. 36. BrianL 12:46 pm 03/14/2013

    What Darren mentions is indeed the perhaps paradoxical notion that massive urbanisation can benefit nature in the long run.

    Apart from the implementation of protective legislation and decreased hunting pressure, there’s also the fact that the rural flight in especially developing nations but also in developed nations means that huge cultivated areas are left alone and revert to a wild or wilder state. Rapidly expanding cities certainly consume land area, but they do concentrate large populations on a smaller surface area. What’s more, those populations also tend to be less mobile as they can fulfill their needs in a far smaller area and thus they will, in general, be less inclined to directly disturb nature in a large area (indirect disturbance such as through pollution is a different matter).
    The take home point is that rural areas tend to be very supressive for the vast majority of wild species so rural flight tends to lessen the pressures on the local environment. This means that in a world of rapid urbanisation, there may be some surprises to come in terms of wild species increasing their numbers and range in the (near) absence of humans.

    I’d personally also be greatly in favour of greening the world’s cities via green walls, green buildings and urban forestry on a large scale. I’d say it would work wonders for human health as well as for urban organisms.

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  37. 37. Heteromeles 2:33 pm 03/14/2013

    Um, major derail in progress. It’s good that crocs can adapt to urban waterways.

    That said, ummmm. About cities. Yes, they are good in that right now, people living in cities (presumably in the US) live on less resources per person than do people in the country, where they have to drive more and stuff.

    That’s both true and false. It’s true that shipping food in bulk to a city uses less gas than shipping people to farms to pick their own. Conversely, it’s false in the sense that almost everything has to be shipped to cities. They distort their surrounding landscapes tremendously, in that every resource gets turned to feeding, watering, and cleaning up the city. While it’s good that the watersheds feeding cities get protected, there are also incidents like Los Angeles dewatering the Owens Valley, with the resulting problems on the Owens Lake (I was there for a week, and I still have flashbacks. It’s not a pleasant place).

    Similarly, California’s Imperial Valley (a desert) imports water from the Colorado River (which mostly drains desert land) to grow vegetables that feed much of the east coast during winter (which is not a desert). California exporting water to New York sounds abundantly stupid, but that happens every time a vegetable travels east. On a broader scale, farms moved out of the eastern US, but that was only because farms in the Midwest were massively more productive. Forests regrew, while prairies were almost totally eradicated, as was their soil. One could argue whether this is good or bad on a number of bases, but one should *never* argue that eastern reforestation was impact neutral. The food is merely being grown elsewhere.

    Equally pernicious is the brain-drain from farmlands. With fewer people in rural areas, that means land is being managed with less intelligence. Granted, people can destroy their small farms as easily as they can destroy their big ones, but I defy anyone to say that a land manager dealing with 100 square miles can manage with as much care as 20 land managers handling five square miles each, or 100 people each managing their own square mile. This is what happens when you take people off the land, and if you’ve turned them into service workers in a nearby city, it’s unclear whether you’ve made the world a better place by doing so.

    Ultimately, I agree that on the fantasy earth of Lovin and Hawkins’ Natural Capitalism, it’s amazingly stupid that water doesn’t leave cities cleaner than it entered it. Cities ideally should be something like coral reefs, efficiently using every resource they have. The problem is that cities are human places, and humans aren’t coral polyps. Even if 99.99% of people are conscientious about what they flush into the sewer or throw in the trash, it only takes one scofflaw to dump a load of car batteries or industrial metals to make all the sewage useless for fertilizer, and that’s what happens every day to every waste stream. We’re stuck with cities harboring idiots and evil people, just as much as they harbor honest citizens, and all our recycling facilities are exquisitely vulnerable to idiocy and vandalism. In fact, most of their sophistication goes to dealing with the idiocy, and sorting the toxins out of the waste so that stuff can be recycled (NB, I have a relative who works in Los Angeles County sanitation, so I get an earful of the issues every month or so. This relative’s next-door neighbor refuses to separate her trash, and puts expired pharmaceuticals and other trash in with the recycling and greenwaste, primarily because she refuses to care).

    Anyway, end of rant. I’m hoping that, if the Sahel greens up, more of these oases can be rewatered, and (hopefully) a bit of homegrown environmentalism can make life better for crocs. Or, at worst, the crocs can start living in the sewers of Timbuktu.

    Link to this
  38. 38. Metridia 3:33 pm 03/14/2013

    >that requires the West African rainforest to be above a certain size,

    I’m pretty sure most of the water vapor in the atmosphere derives from the oceans. Locally yes the rainforest contributes a lot to the water cycle and can self-perpetuate that but overall, the rainforest itself is dependent on the size and extent of the intertropical convergence zone dynamics, which is determined by the atmosphere as a system. So more water vapor overall results from more evaporation near the equator, which is mostly controlled by the oceans. Do you have a reference that says otherwise, that rainforest determines the extent of the ITCZ (and thereby the Sahel greenbelt) and not the other way around?

    If the Mediterranean desertifies, I suppose that would be bad for Italy and Spain but perhaps slightly more landmass becomes arable?

    Link to this
  39. 39. vdinets 4:10 pm 03/14/2013

    Well, in Russia at least, urbanization is extremely beneficial for the environment. Since the 1850-s, agriculture in the forest zone of European Russia was being gradually abandoned, except in the close vicinity of cities, due mostly to competition with more fertile former grasslands, and with other countries. There are thousands of abandoned or nearly-abandoned villages, fields are turning into forests on a massive scale, and wildlife populations outside the 100-km vicinity of large cities are booming. As for the grasslands, they’ve been almost 100% ploughed by 1960, so there is nothing to lose.

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  40. 40. naishd 4:16 pm 03/14/2013

    Ah, thread drift :)

    When writing comment # 35, I had tropical Asia in mind, since urbanization is bringing with it a somewhat better legal framework for wild space protection. I don’t mean to imply that there aren’t other problems, some crippling.

    Seeing as this article is about crocodiles, that reminds me.. anyone any good anecdotes about the survival of crocodylians in urban settings? I’m inspired by the case of the Australian saltie that was missing much of its lower jaw and managed to survive by scavenging from a rubbish dump.

    Darren

    Link to this
  41. 41. Heteromeles 4:53 pm 03/14/2013

    Does Reggie the alligator count?

    Link to this
  42. 42. vdinets 7:25 pm 03/14/2013

    Urban, no; industrial, yes. It’s a well-known fact that the core survival area for the Florida population of American crocs was in the cooling canals of a nuclear power plant.

    Link to this
  43. 43. naishd 4:54 am 03/15/2013

    Yup, familiar with that.

    Darren

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  44. 44. Jerzy v. 3.0. 8:48 am 03/15/2013

    @35
    Certainly, development can help conservation. Not just urbanization, but productive agriculture (less land needed for feeding people) larger income (wild animals are not source of food) and rule of law (conservation is enforced).

    That is why Europe, paradoxically, has bigger population of large mammals than 50 or 100 years ago. Also, wasn’t American alligator hunted to near extinction at one point?

    Link to this
  45. 45. Jerzy v. 3.0. 9:03 am 03/15/2013

    @39
    Yes, in the countries where historically almost all the land was converted to human use, the best scenario is to keep highly productive agriculture and allow the less productive land to return to natural state.

    Link to this
  46. 46. Halbred 3:36 pm 03/15/2013

    That high-walking croc looks absolutely prehistoric, thanks in part to those striking dorsal scutes. Looks like Scutosaurus from the shoulders back.

    So if modern crocodilians evolved very recently, where did Deinosuchus and Sarcosuchus fit into the croc family tree? I recognize that Sarcosuchus is quite different, but I’d always heard that Deinosuchus was basically a giant, more-or-less modern crocodilian.

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  47. 47. SRPlant 7:19 pm 03/15/2013

    Off topic I’m afraid, but I wonder if Darren was a consultant on a mesmerising short film that I’ve just watched on the ARTE television channel (If he wasn’t he should have been!). It’s called “5m80” and is directed by Nicholas Deveaux. Here’s a link that may or may not work;
    http://www.itsartmag.com/features/5m80/#.UUOo0nB8vzI

    Link to this
  48. 48. naishd 6:52 am 03/16/2013

    Halbred (comment # 46): remember that the article here is only about Crocodylus crocodiles, not about crocodylians in general – some lineages of which were present in the Late Cretaceous. Deinosuchus is apparently a stem-alligatoroid, outside the clade that includes extant alligatoroids. Sarcosuchus is not a crocodylian: it’s affinities like elsewhere in Crocodyliformes and as such it isn’t closely related to extant lineages. See previous Tet Zoo articles on crocodyliforms – they should help. See also…

    Naish, D. 2001. Fossils explained 34: Crocodilians. Geology Today 17 (2), 71-77.

    Darren

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  49. 49. naishd 7:00 am 03/16/2013

    SRPlant: no, I wasn’t a consultant for the movie. Very nice :)

    Darren

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  50. 50. Heteromeles 10:52 am 03/16/2013

    @SRPlant: Yes, the link works. Hilarious!

    Link to this
  51. 51. David Marjanović 9:46 am 03/18/2013

    Oh good, I’m allowed to log in again.

    The one small ray of hope is that various Amazonian tribes have proved that it’s possible to plant a lot of rain forest trees, so if we can get people planting trees, the Sahel will bloom and they won’t have a massive humanitarian crisis on their hands. Since they reportedly are experiencing some economic growth despite all the wars, it’s possible.

    …if we can get people way south of the Sahel planting trees, the Sahel will bloom, yes. That would be a huge international project.

    Los Angeles dewatering the Owens Valley

    Southern California and Nevada are incredibly wasteful.

    Forests regrew, while prairies were almost totally eradicated, as was their soil.

    Aren’t the prairies slowly coming back now?

    This relative’s next-door neighbor refuses to separate her trash, and puts expired pharmaceuticals and other trash in with the recycling and greenwaste, primarily because she refuses to care

    Christ, what an asshole.

    Or, at worst, the crocs can start living in the sewers of Timbuktu.

    Day saved.

    I’m pretty sure most of the water vapor in the atmosphere derives from the oceans.

    Uh, yeah. The climate modeling has been done: when the heat goes up, the Sahara only contracts (as it did last time) if there’s enough rainforest south of it. Alas, I only saw that on TV long ago and so don’t have a reference.

    That high-walking croc looks absolutely prehistoric, thanks in part to those striking dorsal scutes. Looks like Scutosaurus from the shoulders back.

    The other way around: Charles Knight and everyone studied “large reptiles” extensively and had them in mind when they reconstructed “even large reptiles”. The result are dinosaurs that look a lot like crocs or, even more often, iguanas.

    Link to this
  52. 52. David Marjanović 9:47 am 03/18/2013

    Oops. I found a stray r lying around. It’s feeling lonely. :-(

    Link to this
  53. 53. naishd 9:52 am 03/18/2013

    Stray r? Where?

    ps – should ‘Scutosaurus’ be Scutellosaurus above?

    Darren

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  54. 54. vdinets 10:29 am 03/18/2013

    David (#51): Prairies (we are talking about tallgrass prairies, which are somewhat similar to meadow steppe-woodland ecotone and blackzem/feathergrass steppes of Eurasia) are not really coming back. There are numerous small restoration projects, but they aim to restore less than 1% of the former area. On the other hand, in the last 10 years virtually all unused agricaltural lands in the US have been brought back into cultivation due to rising food prices. In addition, there is a tendency of tallgrass prairies left unused to become overgrown with trees (it appears that they used to be maintained artificially by Native Americans, and prior to that probably by large herbivores). In parts of Texas, tallgrass prarires are being replaced by shortgrass prairies (technically a type of desert) due to the climate change, locally called “recent drought”.

    Link to this
  55. 55. David Marjanović 12:10 pm 03/19/2013

    Stray r? Where?

    It’s missing from my previous comment, I forgot where.

    in the last 10 years virtually all unused agricaltural lands in the US have been brought back into cultivation due to rising food prices

    Ah. I didn’t know that.

    the climate change, locally called “recent drought”

    Heh. B-)

    Link to this
  56. 56. RaptorX 3:31 pm 03/25/2013

    Sorry if this question might be coming a bit late, and it is also slightly off topic, but perhaps someone can help me out with this. How long does crocodilian parental care last? I know that T. schlegelii shows near-absence of parental care, and I know the exact length of time spent protecting young varies from species to species, but I’ve found conflicting information stating it ranges from just a few weeks in to up to three years in A. mississippiensis and C. niloticus alone. I currently think the later numbers are unlikely, but even then I’m not sure. Some clarification and perhaps reading material on crocodilian reproduction would be much appreciated.

    Thank you.

    Link to this

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