Fearful scimitars

Sabertooth by Mauricio Anton (2013) Bloomington. Indiana University Press. 243 pp.

This is the natural history of an ecological niche: an ambush predator that captures prey by a throw and pin, with powerful forelimbs and a long, strong back, followed by a bite to the neck, using greatly elongated canine teeth, made possible by jaw adaptations that permit a huge gape and a long, strong neck. The bite results in bleed out and death of the victim. It is argued that this leads to quicker and safer kills than the suffocation method employed by modern big cats on large prey. The author does a remarkable job of tracing the paleontology of successive groups of species that have occupied this role since the Permian, although there seem to have been no dinosaurs that did so.

The illustrations of fossils, reconstructed animals and landscapes are beautifully done, in loving detail. The painstaking anatomical analyses to show how these killing machines worked are clear and persuasive, at least to a non-expert. There are interesting accounts of the constantly changing nomenclature of the fossils.

It would be useful to see similar accounts of modern large cats, hyaenids and other carnivores to get a sense of how the sabertooths fit into the big picture of carnivore evolution and why it is they went extinct instead of the others.

The extinction happened several times, as the successive groups of sabretooths disappeared, and they were not quickly replaced. Sometimes millions of years seem to have elapsed before a new lineage appeared to fill the niche. Indeed, sometimes there were no large felids of any kind for extended periods, if we can trust the fossil record. At other times, a new group may have out-competed the current occupants of the sabertooth niche. One might say that there is room at the top of the food web, but it is a precarious position that isn’t always filled.

Perhaps the most recent occupants of the niche went extinct with the megafauna of the old and new worlds, but could they have been done in by more efficient pantherids? Was their technique only suitable for very specific types of prey that got replaced by more wary and evasive herbivores or did vegetation change doom their hunting methods? Did their very specialized anatomy and techniques simply run out of room for improvement against ever more challenging prey? Anton thinks that their very specialized niche may have left them relatively more vulnerable to shifts in prey abundance. This would be a major factor in the late Pleistocene, along with competition from lions and humans, among others. As the least flexible group, they may have been the first to go.

Does it mean there’s an unoccupied niche now, or are those habitats and resources simply gone?

What other convergences in form and behavior has natural selection produced across time and biogeographic realms? We all know at least a few ecological equivalents, like pangolins and armadillos, or moles, marsupial moles and mole crickets. There’s an interesting one involving modern beetles’ and early rodents’ mandibles, but it isn’t clear what the functional significance is (John Acorn in American Entomologist, Summer 2014, p 128). Thanks to Mauricio Anton for presenting this story so beautifully.

Image: Smilodon fatalis – National Park Service

Ecosystem lost and found?

Looking for Longleaf. The Fall and Rise of an American Forest by Lawrence S. Earley (2004) Chapel Hill. University of North Carolina Press. 322pp.

When I was a teenager, my grandfather recalled for me how the longleaf pine forests in eastern North Carolina looked when he was young, some seventy to eighty years before. It was like being in a cathedral, he said, with the trunks of the trees like columns and the forest floor clear as far as you could see. This book gives an introduction to the character and extent of the longleaf pine ecosystem, once dominant over a vast region of the Atlantic and Gulf Coastal Plain, introducing the plant, Pinus palustris, the diversity of associated plants (sometimes hundreds of species in a square kilometer and as many as 40-60 in a square meter) and several of the more distinctive animals, like gopher tortoise and red-cockaded woodpecker.

Earley explains the critical role of fire and soil in establishing the diversity of types within the overall longleaf ecosystem.

The middle part of the book is a historical account of the European encounter with the forest, its exploitation by the naval stores industry and its eventual destruction by that industry and the railroad based loggers. Some of these descriptions fit closely with what I heard from my grandfather and from a friend in North Carolina (whom Earley interviewed for the section on turpentining). He talks about rafting logs down the coastal rivers (as my grandfather, born in 1869, did as a boy) and shipping naval stores (my grandfather also described how the cooper made the barrels for turpentine). He explains that what preserved so much of the forest were the limitation of cutting timber to areas close to usable streams, that is until the railroads came. My father (born 1913) recalled how the railroad was brought in to log some of the most remore and inaccessible places when he was growing up. Some time around 1970, before the railroad was finally abandoned, I saw carloads of longleaf pine stumps waiting to be hauled off to extract the valuable resins or to make fatwood kindling, sold by L.L. Bean, among others. Earley also mentions the continued interest in salvaging sunken logs and getting lumber from old buildings.

The final chapters are on the development of forest management ideas, from failed attempts at replanting to replacement by loblolly and slash pine and the gradual development of methods to regenerate longleaf, first as even aged stands but now moving towards uneven age management and overall ecosystem restoration. Red-cockaded woodpecker played a key role in several changes in policy, driven by court decisions under the Endangered Species Act. Many of the agencies involved, like the US forest Service have serious problems dealing with the steady increase in scientific and ecological understanding of the forests. Institutional change is difficult, especially when institutional memory is impaired by frequent reassignment of key people and political pressures. The US Forest Service has had an especially hard time admitting it has been wrong about fire suppression and even-aged management.

He talks about the role of national and state forests and of large and small private landholders (currently there is increasing longleaf acgeage on federal and maybe state land and on large private conservation holdings, but continued losses on timber company lands and small private holdings) and what the trends may mean for the future of the ecosystem and many of its species. New incentives under the Conservation Reserve Program may be changing the minds of some private owners. It is possible to derive a pretty steady income from restored longleaf, partly through sale of raked needles in the 10th to 15th years after replanting. Poles are much in demand, using middle aged trees. The author seems most impressed by adaptive management approaches using small group-selection cuts and frequent growing season fire. Several interesting examples are described in the next to last chapter on restoration. Some of these areas sound like they would be worth seeing, and there are some groups that can help with restoration, a topic that is on my mind lately, as I and my brothers and sisters still hold a small remnant of thousands of acres of longleaf land owned by my great-great grandfather in the early 1800s. We will soon be clearing the stand of loblolly pine, planted decades ago, to make way for longleaf again.