"Long before it's in the papers"
October 26, 2015


Think lions are scary today? You haven’t seen the Pleistocene epoch

Oct. 26, 2015
Courtesy of University of California - Los Angeles
and World Science staff

Packs of im­mense li­ons and oth­er preda­tors long ago helped keep pop­u­la­t­ions of huge plant-eat­ers such as mam­moths from over­run­ning eco­sys­tems, ac­cord­ing to new re­search.

Sci­en­tists have long won­dered how eco­sys­tems dur­ing the long Pleis­to­cene ep­och, which ended around 12,000 years ago, sur­vived de­spite the pres­ence of many huge, hun­gry her­bi­vores, such as mam­moths, mastodons and gi­ant ground sloths. 

Artist's conception of violent attacks by Pleistocene carnivores. (Credit: Mauricio Anton)

Ob­serva­t­ions of mod­ern ele­phants sug­gest that large groups of those an­i­mals could have ba­sic­ally de­stroyed the en­vi­ron­ment, but they did­n’t.

The find­ings, re­ported this week in the jour­nal Pro­ceed­ings of the Na­t­ional Acad­e­my of Sci­ences, sug­gest that in­tense, vi­o­lent at­tacks by packs of some of the world’s larg­est car­ni­vores—in­clud­ing li­ons much big­ger than those of to­day and saber­tooth cats—did more than make their vic­tims’ lives mis­er­a­ble. They al­so went a long way to­ward shap­ing ecosys­tems.

The re­search could have im­plica­t­ions for con­serva­t­ion ef­forts to­day, the re­search­ers ar­gue. They note that many of to­day’s en­dan­gered spe­cies evolved dur­ing or be­fore the Pleis­to­cene, and un­der very dif­fer­ent con­di­tions from to­day’s. “Recre­at­ing these [Pleis­to­cene] com­mun­i­ties is not pos­si­ble, but their rec­ord of suc­cess com­pels us to main­tain the di­vers­ity we have and re­build it where fea­si­ble,” the re­search­ers write.

Led by Blaire Van Valken­burgh, an ev­o­lu­tion­ary bi­ol­o­gist at the Un­ivers­ity of Cal­i­for­nia Los An­ge­les, they found that thanks to their larg­er size, the an­cient car­ni­vores were more than able to kill young mam­moths, mastodons and oth­er spe­cies. 

The larg­est of the “hyper-car­ni­vores” such as li­ons, saber­tooth cats and hye­nas died out dur­ing the late Pleis­to­cene, they added, probably be­cause of the dis­ap­pear­ance of their pre­ferred prey, in­clud­ing young “mega-her­bi­vores”—mam­moths, mastodons and gi­ant ground sloths.

“Based on ob­serva­t­ions of liv­ing mega-her­bi­vores, such as ele­phants, rhi­nos, gi­raffes and hip­pos, sci­en­tists have gen­er­ally thought that these spe­cies were largely im­mune to preda­t­ion,” be­cause they’re big and ably prot­ect their young, said Van Valken­burgh.

But “data on mod­ern li­on kills of ele­phants in­di­cates that larg­er prides are more suc­cessful,” she went on. “We ar­gue that Pleis­to­cene car­ni­vore spe­cies probably formed larg­er prides and packs than are typ­ic­ally ob­served to­day—making it eas­i­er for them to at­tack and kill fairly large ju­ve­niles and young adult mega-her­bi­vores.”

The sci­en­tists used sev­er­al dif­fer­ent meth­ods to es­ti­mate in­forma­t­ion about the Pleis­to­cene an­i­mals.

One meth­od was to ex­am­ine tooth fos­sils and apply the ra­tio of tooth size to body mass of to­day’s an­i­mals. This led the re­search­ers to es­ti­mate that the ex­tinct spe­cies were be­tween 50 and 100 per­cent larg­er than to­day’s tigers, Af­ri­can li­ons and spot­ted hye­nas. Anoth­er meth­od was to an­a­lyze da­ta on 50,000 in­stances of kills in the wild to es­ti­mate the typ­ical and max­i­mum sizes of the Pleis­to­cene prey.

To­day’s large preda­tors ben­e­fit their eco­sys­tems in part by pro­vid­ing car­casses that feed an ar­ray of smaller spe­cies. The same was true dur­ing the Pleis­to­cene, the re­search­ers ar­gue: keep­ing mega-herb­ivores in check left more vegeta­t­ion for smaller mam­mals and birds to eat. Riv­er areas might al­so have ben­e­fited, since more plants would pro­tect riv­er banks from ero­sion.

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Packs of immense lions and other predators long ago helped keep populations of huge plant-eaters such as mammoths from overrunning whole ecosystems, according to new research. Scientists have long wondered how ecosystems during the long Pleistocene epoch, which ended around 12,000 years ago, survived despite the presence of many huge, hungry herbivores, such as mammoths, mastodons and giant ground sloths. Observations of modern elephants suggest that large groups of those animals could have essentially destroyed the environment, but they didn’t. Predators prevented it, the new research said. The findings, reported this week in the journal Proceedings of the National Academy of Sciences, show that intense, violent attacks by packs of some of the world’s largest carnivores—including lions much bigger than those of today and sabertooth cats—did more than make their victims’ lives miserable. They also went a long way toward shaping ecosystems. The research could have implications for conservation efforts today, the researchers argue. They note that many of today’s endangered species evolved during or before the Pleistocene, and under very different conditions from today’s. “Recreating these [Pleistocene] communities is not possible, but their record of success compels us to maintain the diversity we have and rebuild it where feasible,” the researchers write. Led by Blaire Van Valkenburgh, an evolutionary biologist at the University of California Los Angeles, they found that thanks to their larger size, the ancient carnivores were more than able to kill young mammoths, mastodons and other species. The largest of the “hyper-carnivores” such as lions, sabertooth cats and hyenas died out during the late Pleistocene, they added, probably because of the disappearance of their preferred prey, including young “mega-herbivores”—mammoths, mastodons and giant ground sloths. “Based on observations of living mega-herbivores, such as elephants, rhinos, giraffes and hippos, scientists have generally thought that these species were largely immune to predation, mainly because of their large size as adults and strong maternal protection of very young offspring,” said Van Valkenburgh, who holds an appointment in the UCLA College’s department of ecology and evolutionary biology. “Data on modern lion kills of elephants indicates that larger prides are more successful and we argue that Pleistocene carnivore species probably formed larger prides and packs than are typically observed today—making it easier for them to attack and kill fairly large juveniles and young adult mega-herbivores.” The scientists used several different methods to estimate information about the Pleistocene animals. One method was to examine tooth fossils and apply the ratio of tooth size to body mass of today’s animals. This led the researchers to estimate that the extinct species were between 50 and 100 percent larger than today’s tigers, African lions and spotted hyenas. Another method was to analyzing data on 50,000 instances of kills in the wild to estimate the typical and maximum sizes of the Pleistocene prey. Today’s large predators benefit their ecosystems in part by providing carcasses that feed an array of smaller species. The same was true during the Pleistocene, the researchers argue: keeping mega-herbivore populations in check meant that there was more vegetation for smaller mammals and birds. River ecosystems might also have benefited, since more plants would protect river banks from erosion.