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Okay, now this question is a bit random.

But, I'm planning for a possible book project about a 2019 expedition to an undiscovered island. The island is near the northern tip of the Ninetyeast Ridge in the Indian Ocean. I think the book will be in a similar format to James Gurney's Dinotopia, existing as both a story and a "scientific journal" of the protagonist.

The only thing is, the fauna on this island includes descendants of tigers and various south Asian small cats, rhinoceroses and other fauna typical of Indonesia, Malaysia and nearby regions. However, other animals on the island hail from African ancestors - notably the last surviving members of the Protelinae or "dog-like hyena" subfamily* (Excluding the aardwolf**.), as well as other bone-crushing hyena species.

The last biogeographical obstacle is the presence of earless seals on the island. The only seal that favours tropical climates are the monk seals - With one extinct species*** in the Caribbean, one in Hawaii, and one in the Mediterranean. To me, the Hawaiian monk seal looks like the best candidate for a migrator, but there's still a massive distance between Hawaii and Ninety East. However, anyone who's heard of a Baikal seal will know that seals are very good at overcoming geographical obstacles.

So, this sounds like a lot of zoology, and a lot of paleontology too. But really, I don't need a zoology or a paleontology expert to answer. The main thing I need in a respondant is someone who is versed in geography and knows how an island the size of Ireland**** (The country, not the whole island) could end up on the Ninety East Ridge with East African fauna dating from 800,000 BC as well as more recent South Asian animals. My basic theory is that the island could have split off from East Africa, and the Asian wildlife could have colonised it somehow, but I'm no geographer. I doubt that it would be possible for it to join up with Sundaland (I believe it was a thing fairly recently, again, not a geographer.) Also, if anybody knows how earless seals could get from Hawaii, past Indonesia and to my island, then I'd love to hear from you.

Note: I know that this question may raise the hackles of some people who don't like science/what-if questions, but really this is the only SE site that relates to this. It's a mixture of geography and biology and involves heavy speculation. So, if it's voted to be closed, then there's nothing I can do about that, but please understand that this is the best site, as far as I know, to ask this question.

*The large members of this subfamily didn't go extinct like their mainland counterparts due to the absence of large canids on the island - when dholes and other small canids arrived at the island, the Protelinaeans were dominant and could not be out-competed.

** If the whole 800,000 BC thing doesn't fit into a plausible timescale, I could potentially have more recent aardwolves evolve into large running hyenas.

*** Just because it's extinct now doesn't mean it could have colonised the island before it went extinct, but as said, I think that the Hawaiian seals are a more plausible option anyway.

**** I can change the size if it's necessary.

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  • $\begingroup$ Northern Ireland is only about 15% of the landmass of the island of Ireland, if the distinction is significant for the purposes of the question I'd give the size of your island to be approx 72,000 square kilometers $\endgroup$ – Binary Worrier Apr 5 '18 at 11:16
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    $\begingroup$ Your question currently is very long and includes a lot of debating if this is a good question or not and you being modest in general and in a way feeling sorry for even asking. Either check out the sandbox in the meta if you are unsure if this is the right place and way to ask or clean up your question. Currently I personally find it very bothersome to read your question and trying to extract what you want to know and what you already know. Usually people asking here show no sign of awareness or self-reflection, you went a bit too much into the other direction $\endgroup$ – Raditz_35 Apr 5 '18 at 11:19
  • $\begingroup$ If we can find penguins all the way North to the Galapagos islands, your fauna of african ascendancy can be found on your island. $\endgroup$ – Renan Apr 5 '18 at 13:00
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    $\begingroup$ @Renan Yes, animals can emigrate very far, but there's always a reason why, and I'd like to include that reason in the project. $\endgroup$ – SealBoi Apr 5 '18 at 16:32
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It seems impossible to find an island that have split off from Africa and moved that far in the east of Indian Ocean. You're far beyond the limits of somali plate.

So it would be more plausible to explain the presence of african species by an ancient migration.

Your island seems to be very close to Andaman islands. Indigenous people from Adaman, like the Jarawas, look more like African than Asian people.

Jarawa kids

The Adamans appears to be a milestone in the great coastal migration of Humans along the shores of Indian Ocean.

Black tribes came from Africa via the Arabian peninsula, and then they migrate toward India, South-East Asia and Oceania.

enter image description here

So we can imagine that other african species may have followed the same road, and reached your island when the sea was lower, during the ice age. Even if your island was never directly linked to the continent, it may have been close enough to allow terrestrial animals to end up there.

After the sea rises they would have been definitively trapped on the island, but they found a way to survive.

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  • $\begingroup$ Thanks, I wasn't sure about the whole "splitting off from Africa" thing and if it would work. This actually seems really likely, since there are a good few Africa-originating animals in Asia. EDIT: I looked it up and this did actually happen. African animals such as elephants spread through Africa then emigrated to Southern Asia, according to Wikipedia. Thanks for the great answer! $\endgroup$ – SealBoi Apr 5 '18 at 12:48
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Biogeographically, you shouldn't have a problem. It can be an island with really odd fauna due to rafting events. Just make sure your African animals had a Eurasian distribution at least once. Your island is pretty far for them to survive the voyage.

https://en.wikipedia.org/wiki/Oceanic_dispersal

As a geographer, you might want to consider how to explain the geological origin of your island. If you want to go with a chunk of Gondwana breaking off, then I'd suggest this site

http://www.hhmi.org/biointeractive/earthviewer

to get a better understanding of how India, Africa, Australia, and Antarctica fit together and subsequently broke apart. It's not unheard of for remnants of Gondwana to become "sunken continents" (hello, New Zealand and Kerguelen) but right now all the former parts of Gondwana are accounted for. So you might want to think about what part of Gondwana you want to cut your island out of.

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  • $\begingroup$ Well, I was thinking that the African fauna would have been there before the island split off from Africa, but rafting works too if the time frame is implausible. Also, thanks for the resources! $\endgroup$ – SealBoi Apr 5 '18 at 12:35
  • $\begingroup$ Yeah, the time frame is the problem. Gondwana started breaking up at the end of the dinosaur era, so it'd be difficult for Ice Age mammals to get there. $\endgroup$ – KernelOfChaos Apr 6 '18 at 0:12
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Based on the location of the island, I'd say it is somewhat plausible. Maybe the way the island formed is that the tectonic plates did something different in an alternate timeline. Some animals may have migrated there, that is possible. Species that are extinct elsewhere can survive there as it has happened in reality.

But there are some animals, like the tigers and rhinoceros, I don't agree could be there naturally. But maybe the island was connected to Africa and other places before lots of it sank somehow, like a lost continent. Or an ancient, now lost, civilization brought them there for hunting or living there purposes. It's really up to you. I hope I answered your question well!

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  • $\begingroup$ Well, another respondent has highlighted the fact that rafting could be possible with large animals. Perhaps that would work out. $\endgroup$ – SealBoi Apr 5 '18 at 12:37
  • $\begingroup$ I would agree. It's just that I find that having a tiger travel a gazillion miles across the ocean and surviving on a super large stick highly implausible. Or do you mean rafted on a raft by humans? That would make sense. $\endgroup$ – Rewan Demontay Apr 5 '18 at 20:58
  • $\begingroup$ “Rafting” often refers to a rather large chunk of floating tangled debris. Consider a seasonal Lake in a forested area that floods out to the ocean — a few dozen uprooted trees tangled together can plausibly carry a breeding population of larger mammals. $\endgroup$ – arp Apr 6 '18 at 3:14
  • $\begingroup$ Another respondent suggested the possibility of African animals migrating from Africa, through Arabia and into southern Asia, which gives them a far shorter distance to raft, and probably actually happened, since there are many animals of African origins in southern Asia. $\endgroup$ – SealBoi Apr 6 '18 at 8:12

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