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Homeland news & views

Discussion in 'Aldabra tortoises' started by AldabraNerd, Sep 6, 2012.

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  1. Pokeymeg

    Pokeymeg Well-Known Member 5 Year Member

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    Amazing! I'm so jealous! Please keep the photos comin!!!
  2. Robyn@TRR

    [email protected] Active Member 5 Year Member

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    Wow, this is awesome to see. Sounds like a great gig.

    What about the human side of things? What kind of facilities/housing do you have there? Buildings? A hammock strung between giant tortoises?
  3. AldabraNerd

    AldabraNerd New Member 5 Year Member

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    Lowest night temperature was around 16-18 degrees celcius (low 60's f). I will be able to tell you more exactly later; we have temperature loggers mounted on 31 tortoises around the atoll.

    Sex is, as far as we know, purely determined by incubation temperature. Exactly how it works is more uncertain, though, since no nests have been followed that closely in the wild. Hopefully we'll get there in the next few years. It would be great to find some way to take a blood sample from a hatchling, and look at the epigenetics -- basically analysing which genes are being expressed at any one given time by the body, which could tell us if it's a male or a female, even is there's no chromosomal sex determination (like the XX=female XY=male system in humans - which, by the way, is the other way round in birds!). But I digress :)

    Alas, we haven't got much good info yet about fertility in the different areas around the atoll. There are some old studies by Ian Swingland & others from the late 1970s that contain lots of interesting info! (This one in particular, perhaps: Swingland, I.R. & Coe, M.J. (1979) The natural regulation of giant tortoise populations on Aldabra Atoll: recruitment. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 286, 177-188 --should be attached here below, if I figured out how it all works...).

    So much to study, so little time... :tort::tort:




    [hr]
    Aldabra is a hard/expensive/difficult place to get to... Usually only graduate (PhD) level students or more senior researchers can go there, and only in very low numbers. Much fewer tourist vessels anchor off the research station these days, due to threat of pirates, so that route is also harder now. But it is worth every darn penny/hour of your life to get there! (only took me some 12-13 years of thinking/working on it from the first time I heard of the place & wanted to go/work there! :D).
    [hr]
    There's a permanently manned research station on Picard Island, which normally houses between 12-20 staff/managers/researchers. We live in simple wooden huts/bungalows. More details can be found here:
    http://www.sif.sc/index.php?langue=eng&rub=4

    For a bird's eye view, try this:
    http://maps.google.com/maps?q=Aldab...abra+at&hq=Aldabra+Atoll,+Seychelles&t=h&z=18

    Alas, haven't trained the torts to carry me around in a hammock yet. Good idea, though!:D[hr]
    Next photo chapter -- more about eating. On Aldabra, tortoises eat from sunrise to about 11 am, or whenever it gets too hot. Then they seek shade, and rest until around 3-4pm, again, depending on temperature. Which is pretty nice for a photographer looking for low/interesting light.

    I am fascinated by the way the giants of Aldabra seemingly function like a scaled-down version of elephants in continental ecosystems. Aldabra's low shrub-forests definitely add to this feel! Here's an example, from Picard Island:
    [​IMG]

    And another one - like a giant elephant next to a huge savanna tree:
    [​IMG]

    But eat they do; here's a small shrub being devoured by a large male (the shrub is actually a native caper species, with large fruits whose seeds are dispersed by the tortoises). I have a nice sequence of photos of this guy, slowly reducing the shrub in size during 10 minutes of browsing. One of these days I'll try to make a gif of it :) But you get a sense from how far the tortoise stretches its neck to eat some of the last twigs of the shrub; when he began eating, the shrub was right in front of his face!
    [​IMG]

    The torts stretch like mad to get to favoured plants - also often creating striking browse lines in the vegetation (and yes, this is much higher on Picard (large torts) than on eastern Grand Terre (smaller torts)). Here's a huge male on Picard:
    [​IMG]

    And the same guy a bit later, reaching for a liana they love, but which is usually juuust out of reach:
    [​IMG]

    However, seemingly innocent stretching can lead to fatal accidents. We came across this large male, who had probably stretched himself too far up on a rock, and then slipped... ...only to have his head caught between two small trees.
    [​IMG]

    A sad way to die for such a noble creature. But nothing is wasted on Aldabra; as you can see, coconut crabs are busy eating the inside bits and the skin. Even other tortoises will chomp down with gusto on (more or less) freshly deceased fellow tortoises.

    I hope you enjoyed these photos -- I'm happy to try and post specific ones if people have any suggestions?
  4. Robyn@TRR

    [email protected] Active Member 5 Year Member

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    Terrific pic updates, thanks. A stretched neck seems like a tough way to go, poor guy.
  5. Q'sTortie

    Q'sTortie Member 5 Year Member

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    RE: Homeland news & views

    Seeing these pictures makes me realize this must be what the explorers saw when they first landed on the galapagos islands.

    Thank you for sharing Aldabranerd :D I would like to know if you have come across any babies or juveniles in the wild? If so can you post any pictures that you have?
  6. wellington

    wellington Well-Known Member Moderator 5 Year Member Tortoise Club

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    Ditto on the hatchlings and juvies. Those pics look like they were taken back in the dino days. So cool to see, except the poor guy dieing like he did, so sad:( Thank you so much for taking the time to share with us. I hope you understand how much we all appreciate it. Other then th occasional dead tortoise that they may feed on, have you ever seen them eat anything else other then vegetation? Thanks again:)
  7. DAV46

    DAV46 Member 5 Year Member

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    These pics are outstanding! Very prehistoric and i couldn't imagine how it felt to actually be there and see these wonderful animals. I'm going to go home and hug squirt right after work!!!
  8. ALDABRAMAN

    ALDABRAMAN KEEPER AT HEART 5 Year Member

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    Thank you so much for your updates and continued post, fantastic information and pictures!
  9. Laurie

    Laurie Active Member 5 Year Member

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    RE: Homeland news & views

    Awesome, thanks for sharing!
  10. DesertGrandma

    DesertGrandma Well-Known Member 5 Year Member

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    Thank you so much for this fantastic information. My question is about water. Did you see them drinking and what are their water sources like? I am also interested in the hatchlings and if you ever saw any out in the open?
  11. DAV46

    DAV46 Member 5 Year Member

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    Question- you mention you have seen the temps go down to 60F, is that the coldest it gets there throughout the year? in captivity they seem to be quite cold tolerant and sturdy even when submitted to temps in the 50's. I know of one keeper that stated his would leave the heated shed in 30+ degree weather to sit in sun and had no ill effects. Just curious what are the lowest temps a wild aldabra would see.
  12. srkarpen

    srkarpen Member 5 Year Member

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    RE: Homeland news & views

    What is their social structure like? Obviously there are gigantor herds and tortoises interact with each other but is there any sort of social hierarchy? Do they exhibit any strange social behaviors as far as individual interactions between two tortoises, say for example, high fiving when they find some liana that's low enough to eat? :p obviously they don't high five (maybe you can teach them) but I think you get what I mean.
  13. AldabraNerd

    AldabraNerd New Member 5 Year Member

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    RE: Homeland news & views

    Curiously, there seem to be very few juveniles (10-30 cm) around, and almost no babies. From around 20-25 cm length, you start seeing the occasional older juvenile grazing together with the larger ones. There are (at least) two explanations: 1) natal/juvenile mortality is very high, and most die within a few months of hatching. Population can still stay stable, because once a juvenile becomes adult, mortality drops to very low levels. 2) small juveniles are more numerous than we think, but live in 'hidden' microhabitats (Aldabra abounds in those) - and only come out to feed with the adults when they are large enough not to be easily crushed by mistake (this would seem a real danger to me at least).

    Just before I left Aldabra, in late May early June, egg-laying season started. The wee ones will hatch anywhere between Oct-Dec/Jan-ish. I hope to go back in January - and will certainly look out for babies!

    One of the things we hope to start studying soon, together with colleagues working on the other giants in Galapagos, are the so-called 'lost years' of these giant tortoises (ages 0-10), where we know next to nothing. If any of you know of rich people who'd like to fund a PhD-study on this, let me know :D

    I'll go digging and see what juvenile tortoise photos I can find!
    [hr]
    Good question. Answer: I don't know. There are tortoises that seem more 'social' than others, but whether this is an individual trait or not, we don't know yet. Hopefully, in some years, our almost-completely marked population on Picard Island will help answer this. Ideally, we'd also have more tortoises individually marked in the high density areas in the east of the atoll, but logistics are difficult in that part.

    I will post some photos and stories/anecdotes on behaviours later. Busy time here right now, with semester starting and all! (and plentiful wee nerdlings flooding the gates, yay!). Hopefully also start a thread on an upcoming project that a student of mine will be doing with leopard tortoises in the Kalahari :):tort:

    [hr]
    Water & drinking - post with photos will follow soon-ish!

    Temperature - as I think I said earlier somewhere, I will be able to answer this in much greater detail once we get more data downloaded from the temperature loggers (ibuttons) we have mounted on some of the tortoises :)
  14. ALDABRAMAN

    ALDABRAMAN KEEPER AT HEART 5 Year Member

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    RE: Homeland news & views

    * Do you contribute this to predation? or ?

    * Once again, thank for sharing and posting such great information and first hand experiences.
  15. Yellow Turtle

    Yellow Turtle Well-Known Member 5 Year Member

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    Please answer, you mention that juvenile lives in hidden micro habitat. Have you seen the habitat that they live? What is it? Any research on its humidity, temperature and what they feed there?

    Thank you one more time for giving valuable information.
  16. AldabraNerd

    AldabraNerd New Member 5 Year Member

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    Sorry, my mistake, I should have elaborated: "There are two POTENTIAL explanations...". As I said, for now we know next to nothing about hatchlings/juveniles in the field.

    But no, Aldabraman, we don't contribute to the predation/mortality! :D:D
    (we'd be shipped off the atoll before we could count the toes on a tortoise's hind leg!). Natural predators probably include herons, land crabs, rails (not those with trains! -but a flightless bird), and crows. Introduced cats and rats may take some, too, but are not having an apparent impact on the system as far as we know. And the general harshness of the ecosystem may play a role, too.
  17. Yellow Turtle

    Yellow Turtle Well-Known Member 5 Year Member

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    Thank you for clarify.

    For the environment itself, can you tell us what is the humidity range in the island during daylight and night time? And as you mention they eat from morning till 11 am or until temperature is too hot for them. Can you share what is the peak temperature when they start to seek for shelter?

    Thanks again.
  18. StudentoftheReptile

    StudentoftheReptile Active Member 5 Year Member

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    I "think" he meant to say attribute, not contribute.
  19. AldabraNerd

    AldabraNerd New Member 5 Year Member

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    :D yes, you're right - and I should read up on my reading skills, erh... :rolleyes:
  20. DesertGrandma

    DesertGrandma Well-Known Member 5 Year Member

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    I love all this first hand knowledge and am reading it with much enthusiasm. Would be SOOOOO interested in information on your students study on leopard tortoises in the Kalahari.
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