I have to give partial credit or blame to fellow POD member Robert Alley for this one. He pointed out that island ecological systems are very vulnerable to disruption from humans and our domestic or hitchhiking animals. He said that the end result of the Island California scenario might be that some interesting flowers would survive and we’d have fossils of the really big or interesting animals, but that would be all. I started to respond to that, and the response grew into this essay.

Yes, island ecosystems do tend to be fragile, and I think that in general the smaller the island the more vulnerable those systems are to human interference. I suspect that other factors in that equation are how far advanced the first human settlers were, and how effective the local predators were.

In any case, Madagascar had (and still does have) some reasonably effective small and medium predators, which undoubtedly helped them adapt to human predators. The fossa, and a probably extinct giant cousin of the fossa (a couple hundred pounds and probably as powerful as a lion), kept the smaller lemurs and all but the largest of the other animals on their toes. That didn’t save all of Madagascar’s unique animals, but it undoubtedly helped. It’s a lot easier for an animal to adapt existing anti-predator instincts to a new predator than it is to develop anti-predator instincts from scratch.

Also, in the absence of predators, animals adapt in ways that make them vulnerable when predators are reintroduced. For example, in some of the Mediterranean Islands, deer developed relatively short, thick legs that were very efficient for walking, but not for running away from predators. In an area of Italy which was an island at the time, a small ape developed an upright bipedal mode of walking that was ideal in the absence of predators, but since the toes spread out like a birds, it couldn’t run very fast, and was very vulnerable. It became extinct when the island rejoined the mainland and predators reappeared.

Another factor in how much of an island’s ecology survives human contact is how much of human culture the island has to deal with and how suddenly. Man the hunter-gatherer is disruptive enough, but man the farmer and herder is much worse, especially if farmers and herders are the first to colonize an island. Adapting to human predators is difficult. Adapting to human predators plus dogs and rats, and pigs, and maybe cattle, plus humans clearing the forest for farms and ranges is extremely difficult.

I’ve always thought that long-isolated islands are almost honorary alternate biologies. It’s too bad so little of their diversity has survived. Look at the what-ifs they could have answered:

What if a large island somehow lost all of its native mammals and was recolonized from the sky and the seas? See New Zealand. The answer, or at least one answer, was that flightless birds would take over most of the ecological niches normally held by mammals. That’s what the Moas, and a variety of other birds, including, if I’m recalling correctly, a flightless eagle, did. A couple of species of weak-flying bats who were almost as good as normal mammals at scampering around in trees and on the ground developed in New Zealand, and some large insects do some of the sorts of things that rats and mice normally do.

I’m not sure how you could preserve the larger and more spectacular stuff to the present day. What if the ancestors of the Maori missed the island somehow, or arrived later? I wonder what the first Europeans would have done with an island inhabited only by giant birds. There would be 100-150 years before much ecological consciousness developed. Maybe a few species of moas would have survived.

What if man had reached New Zealand during the hunter-gatherer stage-maybe not long after the aborigines reached Australia? That doesn’t sound likely, but for the sake of argument, assume it happens. Actually, the results could get interesting. The largest Moas would still be toast, but the smaller, faster ones might survive and adapt to human predators. Let’s say that the first landing is an accident, and nobody follows or at least nobody survives to contribute genes to the New Zealand population for the next however many years-maybe as many as 40,000.

The Maoris find the island on schedule, but find them somewhat more difficult to colonize due to the aborigines. There are still surviving New Zealand aborigines when the first Europeans arrive, and the Europeans get a look at what happens to a human population given a small founding population and 40,000 years of isolation in a very odd environment. I wonder if that would be long enough for genetic drift to reduce fertility between the islanders and the rest of humanity. I doubt if that would be long enough for a major impact, but I’d love to be able to find out.

What if Lemurs instead of Monkeys and Apes took over the ecological slots for large primates active in the daytime? See Madagascar, where extinct lemurs looked and acted sort of like a wide range of primates and non-primates-baboons, apes, and giant koalas to name a few. At the same time, fossas took over the large cat niches, and tenrecs took over most of the insect-eating niches.

Could more of the large Madagascar mammals have made it? Again we could go a couple of ways. Madagascar was one of the last large inhabitable places on earth to be colonized. The first colonists probably arrived while the Roman empire was still flourishing-not too many years either way from the birth of Christ. Delay those colonists by three or four hundred years and some of the giant birds and lemurs would have probably survived long enough to be brought back to Europe. They’d still have to survive another couple of hundred years before there is much likelihood of Europeans taking a hand in events enough to let them survive.

Let’s try the other way. Madagascar is fairly near the coast of Africa. What if it got colonized much earlier? Now here unfortunately the most interesting scenarios are the most unlikely.

What if Madagascar was colonized by an Australopithecus species? They would probably find hunting on Madagascar much easier than on the mainland. They might develop a specialized hunting culture based on very primitive technology, or even lose what little technology they had and become predators based solely on their physical strength and speed. If they were left alone for a few million years they could develop into diverging lines, with some specializing as predators while others competed with some of the larger lemurs for fruit. Fun idea, but unlikely.

H. erectus is a somewhat more viable candidate to make it to Madagascar, and still primitive enough in technology that more of the local animals would have probably survived. Even modern humans could be fun if they arrived early enough. Give them 60,000 years of isolation, with primitive and possibly declining technology levels, and they could end up very strange. That would be long enough for a significant subset of the large Madagascar animals to adapt to human predators. The presence of rival humans might also slow down the colonization by the people who actually colonized Madagascar in our time-line (close relatives of the Polynesians, surprisingly) enough that that colonization would not be complete when Europeans arrived.

I could go on for pages about the various islands and the what-ifs that they could have shed light on. Rats and mice take over the world? See Timor before the first settlers. Mix a few Australian Marsupials and a handful of Asian animals and see how they divide up the ecology? See Sulawesi.(What used to be called Celebes) Repeatedly isolate, then bring back together parts of a species of monkeys to see if they form separate species and to see if they diverge into different ecological niches? See Sulawesi again.

There are a few things that as far as I know have not been tried out on an island somewhere that might have been sort of fun:

Marsupial Monkeys: If New Guinea had gotten larger sooner it might have provided a test of whether or not Marsupials could develop monkey-like species, given a large area of tropical rainforest to play in. New Guinea was actually a rather small island until fairly late in the Pliocene. There are some primarily leaf-eating Marsupials in the area-like the Cuscus, the Tree Kangaroos and some of the Ringtail Possums-that are superficially somewhat monkey-like, but there are no omnivorous or primarily fruit-eating marsupials in the area. I suppose something like that could have developed and then been killed off by early man. New Guinea did lose some species when our ancestors moved in.

The whole concept of parallels to monkeys interests me. Our ancestors killed off some fascinating lemurs on Madagascar that could have given us some insights into how else this primate ecological niche thing can be approached. The Indians apparently did an even more thorough job of wiping out the very odd monkeys on the various West Indies islands (see the brainstorming session on a ‘Greater West Indies” for more on that.)

About the closest non-primate parallel to monkeys that actually still exists is the Kinkajou, a distant relative of raccoons. It looks and acts a lot like a monkey, except that it is nocturnal. The Owl Monkeys of South America (the only nocturnal monkeys in the world) apparently consider it competition. They answer Kinkajou territorial calls the same way they do those of other Owl Monkeys.

I don’t have any evidence of this, but I suspect that before the land bridge between North and South America became complete there was a group of species similar to the Kinkajou in the tropical part of Central America. They would have occupied the ecological territories that monkeys normally do until South American monkeys moved north and pushed them out. Kinkajous would be one survivor of that competition. Coatis would be another. Coatis appear to be monkey wannabes to some extent. Real monkeys like the capuchins are much too agile for them, and typically chase groups of coatis out of the trees when the two species meet. I’m guessing that there were at one point either day-living kinkajous or more arboreal coatis, or maybe both, but they didn’t survive the competition.

Monotreme Island: I wonder how the Monotremes (ancestors of the platypus and spiny anteater would have done if they had good-sized island to develop in. Let’s say a Madagascar-sized block of Antarctic breaks off at the appropriate time and heads north into the South Pacific. For whatever reason, the Monotremes get an early jump on the competition and spend the next several tens of millions of years developing into all or most of the ecological niches that mammals normally take over. Would they develop the same types of body forms that ‘regular’ mammals did on the various continents?

They have a somewhat different basic body form, and a different reproductive system. Would that push them to come up with different solutions to filling the various ecological niches? There are always different options to filling an ecological niche. For example, large grazing or browsing animals on continents or large islands are going to have to cope with predators. Do they do it by running away like a deer? By hopping away like a kangaroo? By running to a burrow like a wombat? By staying and fighting like Ground Sloths probably did? By squatting down underneath a shell or a thicket of spines like a turtle or armadillo?

At least some authors claim that Monotremes don’t dream, and that not dreaming forces them to make less sophisticated use of their brains’ storage capacity. Spiny anteaters do have relatively large brains for their body size and ecological niche, but those brains may not be comparable to those of ‘normal’ mammals if they work differently.

Island of the mammal-like Crocodiles: This takes a little explanation. It seems that in Africa around 80 million years ago, some relatives of the Crocodile developed some very mammal-like small forms. Paleontologists kept finding teeth that they figured belonged to some otherwise unknown kind of mammal. Then they found more complete remains, and the mystery teeth belonged in the jaw of these small crocodiles, some of which were apparently plant-eaters. So, you put these things on a Madagascar-style island, let simmer for 80 million years or so, then see what you get. Does it parallel what you’d get with mammals, or does the different ancestry lead to a different set of solutions?

Island of the Chameleons: True Chameleons look like something out of the age of dinosaurs, but they have remarkably sophisticated solutions to some of nature’s thorny problems. For example, eyes set in the front of the head give overlapping fields of vision, which gives better depth perception. Eyes set in the side of the head give less overlap, but makes it easier to see something sneaking up behind you.

Chameleons finesse the issue by having their eyes on turrets where they can be rotated forward to give good depth perception, or to the side or even the back to keep an eye out for predators. Then of course, there is the color-changing ability, which is apparently mostly for expressing emotions, but could probably be developed into something more systematically useful for camouflage. I find it hard to visualize an ecological system dominated by those things, but if you want something really exotic for an island in one of your alternate geology scenarios, this would be it.

I believe (and I may be wrong on this) that Chameleons are currently extremely common on Madagascar, with a large number of species. There are a few species on Mainland Africa. I’m not sure whether they developed in Madagascar and a few species spread out of the island, or if they developed in Africa, then found the relative vacuum of Madagascar an easy place to diversify.

 

If you enjoyed this essay, or if you are disappointed with it, please let me know. I always read and enjoy any feedback I can get.  

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