African savannas

While reading a book on sauropods recently (which I really need to finish ASAP) I came across a section on predator/prey relationships.  It made the good point (this is not original to this book, but I can't remember where I saw it previously) as it described them.  The east African savanna is sometimes put forward as a mature, modern ecosystem, but there are a lot of reasons to believe that it is actually predator impoverished.  Namely:

• The climate is particularly arid (I mean, not desert arid, but not super productive) and the large herbivores tend to migrate out during the dry season, providing a particularly lean maximum for predator numbers.
• It's never been known without the specter of human interference, as Massai and other human tribes have been cattlemen in the area, hunting predators both as a demonstration of masculinity and as rivals for their food.
• In the relatively recent past, it had actually several other large predators that are now extinct (Dinofelis and a species of Megantereon and Homotherium, among others).

Although the predator/prey ratio in the savanna is today less than 1%, it probably should be "stable"; i.e., in an ecosystem fully recovered after a mass extinction event, at 3-5% or so.

As an aside, it should be noted that the herbivore diversity isn't as high in Africa today as it was in the Pleistocene either.  There are only two proboscideans, when there were 4-5 in the past, for instance, at the top of the large herbivore guild.  This included not only the African elephant, but the "Asian" elephant, in the form of Elephas recki, which actually originated in Africa, mammoths in the form of the earliest known mammoths (so they're also originally an African only animal; like Elephas, Mammuthus is best known after it left Africa and was gradually replaced by Loxodonta), Stegodon and Deinotherium—many of which are contenders for the largest non-baluchatherium terrestrial mammal.  There are reports of remains referable to the mastodon (Mammut) genus from Africa from the Pliocene and early Pleistocene as well.

So for this week's (belated) extinct animal of the week, I offer up one of the aforementioned predators: the jaguar-sized Dinofelis.  It is famous for some fossils that are found in a predator trap with some baboons, where it was obviously eating them, as well as bipedal savanna apes like Australopithecus and Paranthropus.  It's also been suggested that they may have been (along with other saber-, knife-, dirk- and scimitar-toothed cats) have been capable and in fact specifically co-evolved to hunt proboscideans like the elephants, mammoths, mastodons and the like—at least young and old examples of them.  (Homotherium was particularly a hunter of them, it seems, based on bone isotope studies as well as the Friesenhahn cave finds in Texas.  Smilodon, on the other hand, seems not to have been—prefering bison and camels in California and peccaries and llamas in Florida, and toxodonts and litopterns in South America.  Given this, the evidence for Dinofelis having such a diet seems less strong than one would like for those who are making the claim.)

Still, although he's a little lost in the shuffle of bigger and more local saber-tooths, you gotta hand it to Dinofelis who is supposed to have eaten early hominids, assuming that the Out of Africa theory remains credible.

As an aside; this is an interesting point: some specialists have pointed out that the relatively "full" complement of megafauna in Africa is evidence precisely of the fact that it was the last colonized continent by humans; who hunted the megafaunas of every other continent to impoverishment.  Even the Out of Africa folks are now forced to admit that prehistoric DNA evidence suggests a reflux Out to the Middle East and then Back Into Africa as the more derived version of their model.  If you're interested in pursuing other alternatives to the Out of Africa model, there's an intriguing Out of America model, in three versions of progressively more radical bent, that I think is really fascinating.

While I admit to being an iconoclast, I don't want to accept iconoclast ideas simply because they buck the accepted notions, however.  They actually have to be better models than the status quo.  Out of America may yet end up qualifying, if more work is done into promoting and describing it.