Sabercats and Other Carnivores Kept the Ice Age World Green

A Smilodon angles to get a better bite on a sloth at the La Brea Tar Pits and Museum. Photo by Brian Switek.
A Smilodon angles to get a better bite on a sloth at the La Brea Tar Pits and Museum. Photo by Brian Switek.

The huge herbivores of the Ice Age were ecosystem engineers. Wherever they went, mastodons, sloths, bison, and their ilk changed the landscape by eating, defecating, trampling, and otherwise going about their plant-mashing business. But they were not isolated agents. Following out the engineer analogy, the megaherbivores of times past had managers. These were the sabercats, hyenas, wolves, and other predators past.

Many Pleistocene carnivores certainly look menacing enough. The long fangs of Smilodon have made it a staple of museum halls as well as schlock horror, and the thought of staring down a giant hyena is enough to send a shiver down my spine. So given that some prehistoric predators had such impressive weapons it’s not surprising that we’ve often imagined them setting into mammoths and other Ice Age giants. Bigger prey requires bigger cutlery, right?

Well, not quite. Many of the most iconic Ice Age herbivores were simply too big to kill. It’s the same reason why lions don’t chase after adult elephants. Clawing into a pachyderm is a high-risk scenario, even considering the fleshy reward, and fossil evidence has suggested the same pattern held in the Pleistocene. Smilodon didn’t take on adult mammoths and Megatherium, for example, but often targeted camels and bison instead. Large size was a refuge was most Pleistocene giants. But their offspring were a different story.

In a new study surveying the effects of large carnivores stalking the Ice Age landscape, University of California, Los Angeles paleontologist Blaire Van Valkenburgh and colleagues found that the young of many large Pleistocene herbivores would have been right in the sweet spot for hungry carnivores.

Part of the analysis involved sizing up the predators themselves. For starters, Van Valkenburgh and coauthors point out, not only were many extinct Pleistocene carnivores significantly larger than the predators that survived them, but each “carnivore guild” in the sample included a greater number of species in the past than comparable ecosystems today.

Even just looking at the felids, the researchers write, “nearly all Pleistocene predator guilds found outside of Australia included at least one and often two species of large sabertooth cat.” This pattern is directly related to the number of big herbivores there were to eat. Even in modern ecosystems, Van Valkenburgh and colleagues point out, the likelihood that three or more large carnivores might be present steadily increases. In addition to the herbivores creating more open habitat that give predators the opportunity to hide along the forested margins, there’s simply more meat to carve up.

Much of that flesh came in the form of juvenile giants. Even though we tend to think of adult specimens embodying any given fossil species, all prehistoric animals had to grow up. And just as with modern species – like the 74 juvenile elephants taken by lions over a four year period in Botswana – the little ones are vulnerable. Juveniles would have been even more at risk in the Ice Age, when apex predators were larger and there were far more of them.

Baby mastodon - like this one at the La Brea Tar Pits and Museum - would have been vulnerable until they reached about six years of age. Photo by Brian Switek.
Baby mastodon – like this one at the La Brea Tar Pits and Museum – would have been vulnerable until they reached about six years of age. Photo by Brian Switek.

Drawing from data on prey selection by modern carnivores, Van Valkenburgh and colleagues applied the same ecological arithmetic to the fossil record. While a solitary extant lion probably can’t capture even a two-year-old baby elephant, the paleontologists found, a lone Smilodon, Homotherium, cave lion, or other large cat would have been capable of hunting a baby mammoth or mastodon in the two-to-four-year-old range. (A sabercat den full of baby mastodon bones in Texas supports this contention.)  The chances of the Pleistocene predators only got better if they formed a pride, and social strategy was a boon to packs of wolves and clans of hyenas, too.

So while none of the Ice Age carnivores could have taken on an adult mammoth or mastodon, all of them – especially if they were social predators – were capable of tearing into the young. The big proboscideans would have been vulnerable until they were about six years old, which is a long time to have to be looking out for hungry eyes peering through the brush.

This is how the landscape was shaped by the subtle paw of the carnivores. Many paleontologists previously thought that Ice Age herbivores were too big to fail. That they existed at “saturation levels” because their size made them immune. But now Van Valkenburgh and coauthors have made a solid case that carnivores greatly influenced herbivore populations by preying on the young. This was violent, and even sad, but all a part of the constant ecological shuffle. Unchecked by carnivores, large herbivores can proliferate to destructive levels until they start eating themselves out of house and home. Smilodon, dire wolves, and other beasts of prey actually defended the plants – vegetation has no greater friend than a predator. That’s how large carnivores have been keeping the world green for millions of years , and I hope that our species can yield them the space to keep doing so.

Reference:

Van Valkenburgh, B., Hayward, M., Ripple, W., Meloro, C., V. Roth. 2015. The impact of large terrestrial carnivores on Pleistocene ecosystems. PNAS. doi: 10.1073/pnas.1502554112

 

8 thoughts on “Sabercats and Other Carnivores Kept the Ice Age World Green

  1. I’m reminded of Leopold’s statement in “Sand County Almanac.” He stated that ‘the mountain fears her deer.’ His was a poetic way of stating that deer, if left unchecked, will denude the mountain of its foliage. Predation is necessary for the dynamic unbalance that is nature.

    One question I’ve never been unable to answer for myself is why some populations swing wildly in numbers, on a routine basis, without becoming extinct. I know there are issues of differential predation. If cottontail populations decline to nearly invisible numbers, predators shift their emphasis to other species. Somehow, based on my mathematical weaknesses, I have difficulty understanding why this actually works. I have a number of scaled and bobwhite quail on my ranch in Texas which I watch quite closely. If rains come at the right time for a couple of years, quail populations explode, apparently due to successful nesting efforts and chick survival. Yet, should there be drought for a couple of years, quail will almost completely disappear from the landscape…maybe 5% of high population numbers. So far, so good but frequently our droughts go on for 4 or 5 years. A mature quail, even during ‘normal’ conditions, lives only 2-4 years. Yet, despite the fact that we have only minute numbers of quail after only two years of drought–and the fact the quail disappear from the country with a 4 year drought–when the rains come back after 4-5 years of drought, quail populations explode with a bird under almost every bush. I know this is true but mathematically it seems that these birds should go into local extinction during a 4-5 year drought..but they don’t.

    1. Ron, I lived in North Texas for about seven years. My last year there (2004) was one of heavy rains. Fire Ants practically took over the area. However, even though they weren’t that noticeable before then, they were still all over the place. You mention cottontails and quail, two species of animals that have gotten pretty good at hiding. I might suggest that though the numbers have decreased, they were probably not as low as you think. It may be that the number of animals are smaller, but that also means more available cover for those that are alive. When the population booms, there is obviously less cover per animal and so it seems like there are even more than there really are. Not that there isn’t a lot, I still remember the crickets which were covering the ground in Garland when I first pulled moved there! Hope this makes sense, I’m in need of just one more cup of coffee. 🙂

  2. It has probably occurred to others but it seems to me that Smilodon having a rather heavy set of fangs and lacking a respectable tail could have been only an ambush predator possibly only from an elevated position above the prey. The possibility of Smilodon racing after a baby mammoth or whatever, trying to rapidly maneuver a relatively heavy body without a counter balancing tail whilst positioning it’s head far enough back for it’s long fangs to meaningfully penetrate and keeping it’s eyes completely focused on the prey does not seem very strong.

    1. It did not occur to me, but it seems that the scenario you described as an ambush predator is the image I always draw in my mind. Not from my imagination, but from pictures as a child. Nice to know there is a place on the web where intelligent people can go. I’ll try and keep up.

    2. Tom: Don’t think it’s controversial to suggest that sabers ambushed — most cats do if they can, sprinting for 1 to 10 seconds. But I don’t agree that they would need a gravity assist at pointblank range. I’d expect that Smilodon and the like could do a very creditable 20-40m sprint, and tail-less or not, be agile enough to bring down the prey mentioned — bison, camels, juvenile sloths and proboscidians.

      My model is my female Manx, short-bodied, barrel-chested with powerful shoulders, minimal tail — pretty much a .03 scale smilodon. She’s not agile in the air [so thankfully unable to capture birds], but a cannonball on a straight run.

  3. Enjoying y’alls conversation! Can anybody explain to me how they actually killed prey? A bite to the back of the neck with a paralyzing spinal injury? A bite to the throat slashing through veins & arteries? I know that set of teeth must have been extremely successful but I have a hard time knowing how!

  4. I think the saber toothed cats were indeed, ambush predators, they would leap up onto the side of their prey & pull it down with those heavily muscled forelimbs, while on it’s back, they would sink those big, long fangs into it’s throat & tear out it’s jugulars, carotid arteries & perhaps it’s trachea. Even if the animal broke free, it wouldn’t get far as it would bleed out very quickly.

    The teeth would be too brittle to sever the spinal cord, the gape is not wide enough to eviscerate the prey either, only a bite to it’s throat would be effective with such long, fragile, saber teeth.

    Modern big cats with their short fangs go in to a. smother the prey by covering the preys mouth & nose with it’s own mouth or b. close off it’s windpipe by bitting it in it’s throat.

  5. Another reason to bring back the sabretooths.

    IMO, sabretooths were even more specialized for the ambush than pantherines. At least pantherines can sprint.,

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