Smilodon

Smilodon

Overview
Smilodon often called a saber-toothed cat or saber-toothed tiger, is an extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of machairodonts
Machairodontinae
Machairodontinae is an extinct carnivoran mammal subfamily of Felidae endemic to Asia, Africa, North America, South America, and Europe from the Miocene to Pleistocene living from c. 23 Ma until c...

. This saber-toothed cat
Saber-toothed cat
Saber-toothed cat or Sabre-toothed cat refers to the extinct subfamilies of Machairodontinae , Barbourofelidae , and Nimravidae as well as two families related to marsupials that were found worldwide from the Eocene Epoch to the end of the Pleistocene Epoch ,...

 was endemic to North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, living from near the beginning
Early Pleistocene
Calabrian is a subdivision of the Pleistocene Epoch of the Geologic time scale. ~1.8 Ma.—781,000 years ago ± 5,000 years, a period of ~.The end of the stage is defined by the last magnetic pole reversal and plunge in to an ice age and global drying possibly colder and drier than the late Miocene ...

 through the very end
Lujanian
The Lujanian age is a period of geologic time within the Pleistocene and Holocene epochs of the Neogene used more specifically with South American Land Mammal Ages...

 of the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 epoch (2.5 mya—10,000 years ago).

The nickname "saber-tooth" refers to the extreme length of their maxillary canine
Maxillary canine
The maxillary canine is the tooth located laterally from both maxillary lateral incisors of the mouth but mesial from both maxillary first premolars...

s. Despite the colloquial name "saber-toothed tiger", Smilodon is not a tiger
Tiger
The tiger is the largest cat species, reaching a total body length of up to and weighing up to . Their most recognizable feature is a pattern of dark vertical stripes on reddish-orange fur with lighter underparts...

; the latter belongs to subfamily Pantherinae
Pantherinae
Pantherinae is the subfamily of the family Felidae, which includes the genera Panthera, Uncia and Neofelis.The divergence of Pantherinae from Felinae has been ranked between six and ten million years ago. DNA analysis suggests that the snow leopard Uncia uncia is basal to the entire Pantherinae and...

, whereas Smilodon belongs to subfamily Machairodontinae
Machairodontinae
Machairodontinae is an extinct carnivoran mammal subfamily of Felidae endemic to Asia, Africa, North America, South America, and Europe from the Miocene to Pleistocene living from c. 23 Ma until c...

.
Discussion
Ask a question about 'Smilodon'
Start a new discussion about 'Smilodon'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Recent Discussions
Encyclopedia
Smilodon often called a saber-toothed cat or saber-toothed tiger, is an extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of machairodonts
Machairodontinae
Machairodontinae is an extinct carnivoran mammal subfamily of Felidae endemic to Asia, Africa, North America, South America, and Europe from the Miocene to Pleistocene living from c. 23 Ma until c...

. This saber-toothed cat
Saber-toothed cat
Saber-toothed cat or Sabre-toothed cat refers to the extinct subfamilies of Machairodontinae , Barbourofelidae , and Nimravidae as well as two families related to marsupials that were found worldwide from the Eocene Epoch to the end of the Pleistocene Epoch ,...

 was endemic to North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, living from near the beginning
Early Pleistocene
Calabrian is a subdivision of the Pleistocene Epoch of the Geologic time scale. ~1.8 Ma.—781,000 years ago ± 5,000 years, a period of ~.The end of the stage is defined by the last magnetic pole reversal and plunge in to an ice age and global drying possibly colder and drier than the late Miocene ...

 through the very end
Lujanian
The Lujanian age is a period of geologic time within the Pleistocene and Holocene epochs of the Neogene used more specifically with South American Land Mammal Ages...

 of the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 epoch (2.5 mya—10,000 years ago).

Etymology


The nickname "saber-tooth" refers to the extreme length of their maxillary canine
Maxillary canine
The maxillary canine is the tooth located laterally from both maxillary lateral incisors of the mouth but mesial from both maxillary first premolars...

s. Despite the colloquial name "saber-toothed tiger", Smilodon is not a tiger
Tiger
The tiger is the largest cat species, reaching a total body length of up to and weighing up to . Their most recognizable feature is a pattern of dark vertical stripes on reddish-orange fur with lighter underparts...

; the latter belongs to subfamily Pantherinae
Pantherinae
Pantherinae is the subfamily of the family Felidae, which includes the genera Panthera, Uncia and Neofelis.The divergence of Pantherinae from Felinae has been ranked between six and ten million years ago. DNA analysis suggests that the snow leopard Uncia uncia is basal to the entire Pantherinae and...

, whereas Smilodon belongs to subfamily Machairodontinae
Machairodontinae
Machairodontinae is an extinct carnivoran mammal subfamily of Felidae endemic to Asia, Africa, North America, South America, and Europe from the Miocene to Pleistocene living from c. 23 Ma until c...

. The name Smilodon comes from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

: , smilē, "chisel
Chisel
A chisel is a tool with a characteristically shaped cutting edge of blade on its end, for carving or cutting a hard material such as wood, stone, or metal. The handle and blade of some types of chisel are made of metal or wood with a sharp edge in it.In use, the chisel is forced into the material...

" together with (hodoús), "tooth", or in the genitive: , odóntos.

Classification and species



The genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Smilodon was described by the Danish
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 naturalist
Natural history
Natural history is the scientific research of plants or animals, leaning more towards observational rather than experimental methods of study, and encompasses more research published in magazines than in academic journals. Grouped among the natural sciences, natural history is the systematic study...

 and palaeontologist Peter Wilhelm Lund
Peter Wilhelm Lund
Peter Wilhelm Lund was a Danish paleontologist, zoologist, archeologist and who spent most of his life working and living in Brazil...

 in 1841. He found the fossils of Smilodon populator in caves near the small town of Lagoa Santa
Lagoa Santa
For Lagoa Santa, a municipality in Goiás see Lagoa Santa, GoiásLagoa Santa is a municipality and region in the state of Minas Gerais, Brazil...

, in the state of Minas Gerais
Minas Gerais
Minas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...

, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

.

A number of Smilodon species have been described, but today usually only three are recognized.
  • Smilodon gracilis, 2.5 million-500,000 years ago; the smallest and earliest species (estimated to have been only 55 to 100 kg (121.3 to 220.5 lb)) was the successor of Megantereon
    Megantereon
    Megantereon was an ancient machairodontine saber-toothed cat that lived in North America, Eurasia, and Africa. It may be the ancestor of Smilodon.- Fossil range :...

    in North America, from which it probably evolved. The other Smilodon species probably derived from this species.
  • Smilodon fatalis, 1.6 million-10,000 years ago, replaced Smilodon gracilis in North America and invaded western South America as part of the Great American Interchange
    Great American Interchange
    The Great American Interchange was an important paleozoogeographic event in which land and freshwater fauna migrated from North America via Central America to South America and vice versa, as the volcanic Isthmus of Panama rose up from the sea floor and bridged the formerly separated continents...

    . In size it was between Smilodon gracilis and Smilodon populator, and about the same as the largest surviving cat, the Siberian Tiger. This species was about 1 m high at the shoulder and is estimated to have ranged from 160 to 280 kg (352.7 to 617.3 lb). Sometimes two additional species are recognized, Smilodon californicus and Smilodon floridanus, but usually they are considered to be subspecies of Smilodon fatalis.

  • Smilodon populator ("Smilodon the Devastator"), 1 million-10,000 years ago; occurred in the eastern parts of South America and was the largest species of all machairodonts. It was much larger than its cousins, S. fatalis and S. gracilis, possessing a massive chest and front legs, and is the largest known variety of saber-toothed cat. It was more than 1.22 m (48 in) high at the shoulder, 2.6 m (102.4 in) long on average and had a 30 cm (11.8 in) tail. With an estimated weight of 360 to 470 kg (793.7 to 1,036.2 lb), it was among the heaviest known felids. Its upper canines reached 30 cm (11.8 in) and protruded up to 17 cm (6.7 in) out of the upper jaw. Genetic evidence suggests that Smilodon populator and other members of the genus diverged from the main lineage of modern cats (subfamily Felinae
    Felinae
    Felinae is a subfamily of the family Felidae which includes the genera and species listed below. Most are small to medium-sized cats, although the group does include some larger animals, such as the Cougar and Cheetah....

    ) around 14-18 million years ago.


Smilodon populator is also known from the famous cave site of Ultima Esperanza, with well-preserved remains retaining endogenous DNA.

Anatomy



The species of Smilodon were among the largest felids ever to live; the heaviest specimens of the massively built carnivore S. populator may have exceeded 500 kg (1,102.3 lb).

A fully-grown Smilodon weighed approximately 55 to 470 kg (121.3 to 1,036.2 lb), depending on species. It had a short tail, powerful legs, muscular neck and long canines. Smilodon was more robustly built than any modern cat, comparable to a bear
Bear
Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...

. The lumbar region of the back was proportionally short, and the lower limbs were shortened relative to the upper limbs in comparison with modern pantherine
Panthera
Panthera is a genus of the family Felidae , which contains four well-known living species: the tiger, the lion, the jaguar, and the leopard. The genus comprises about half of the Pantherinae subfamily, the big cats...

 cats, suggesting that Smilodon was not built for speed.

The largest species, the South American S. populator, had higher shoulders than hips and a back that sloped downwards, superficially recalling the shape of a hyena
Hyena
Hyenas or Hyaenas are the animals of the family Hyaenidae of suborder feliforms of the Carnivora. It is the fourth smallest biological family in the Carnivora , and one of the smallest in the mammalia...

, in contrast to the level-backed appearance of S. fatalis, which was more like that of modern cats. However, while its front limbs were relatively long, their proportions were extremely robust and the forearm was shorter relative to the upper arm bone than in modern big cats, and proportionally even shorter than in S. fatalis. This indicates that these front limbs were designed for power rather than fast running, and S. populator would have had immense strength in its forequarters.

Limbs



Smilodon had relatively shorter and more massive limbs than other felines. It had well developed flexors and extensors in its forepaws, which enabled it to pull down large prey. The back limbs had powerfully built adductor muscles which might have helped the cat's stability when wrestling with prey. Like most cats, its claws were retractable.

Teeth and jaws



Smilodon is most famous for its relatively long canines
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...

, which are the longest found in the saber-toothed cats, at about 28 cm (11 in) long in the largest species Smilodon populator.

These canine teeth were fragile and could not have bitten into bone; thus, these cats did not use their long teeth while taking down prey, due to the risk of breaking them. Only when their prey was totally subdued did they use their teeth to simultaneously sever the blood supply and strangle the windpipe, instantly killing the prey.

Despite being more powerfully built than other large cats, Smilodon actually had a weaker bite. Modern big cats have more pronounced zygomatic arch
Zygomatic arch
The zygomatic arch or cheek bone is formed by the zygomatic process of temporal bone and the temporal process of the zygomatic bone , the two being united by an oblique suture; the tendon of the Temporalis passes medial to the arch to gain insertion into the coronoid process...

es, while Smilodon had smaller zygomatic arches which restricted the thickness and therefore power of the temporalis muscle
Temporalis muscle
The temporal muscle is one of the muscles of mastication.-Structure:It arises from the temporal fossa and the deep part of temporal fascia...

s, and thus reduced Smilodon’s bite force. Analysis of its narrow jaws indicates that it could produce a bite only a third as strong as that of a lion. There seems to a be a general rule that the saber-toothed cats with the largest canines had proportionally weaker bites. However, analyses of canine bending strength (the ability of the canine teeth to resist bending forces without breaking) and bite forces indicate that saber-toothed cats' teeth were stronger relative to the bite force than those of modern "big cats". In addition, Smilodon could open its jaws 120 degree
Degree (angle)
A degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...

s, whereas the lion's gape is limited to 60 degrees.

It has been suggested that Smilodons smaller temporalis muscles (controlling much of the bite force) were not used in the killing of prey; rather, Smilodon stretched its jaws around the throat and pressed its canines into the prey with the use of its immense neck and forelimb muscles. The penetration was the result of the neck flexors instead of the jaw muscles, according to this hypothesis.

Diet and hunting


Smilodon probably preyed on a wide variety of large game including bison
Bison
Members of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...

, tapirs
California tapirs
The California tapir is a term that is applied to either of two species of tapirs that concurrently inhabited the North American continent during the Pleistocene era – Tapirus californicus and Tapirus merriami. Both species went extinct approximately 13,000 to 11,000 B.C...

, deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...

, American camel
Camel
A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...

s, horses and ground sloth
Ground sloth
Ground sloths are a diverse group of extinct sloths, in the mammalian superorder Xenarthra. Their most recent survivors lived in the Antilles, where it has been proposed they may have survived until 1550 CE; however, the youngest AMS radiocarbon date reported is 4190 BP, calibrated to c. 4700 BP...

s. As it is known for the saber-toothed cat
Homotherium
Homotherium
Homotherium is an extinct genus of machairodontine saber-toothed cats, often termed scimitar cats, endemic to North America, South America, Europe, Asia, and Africa during the Pliocene and Pleistocene epochs , existing for approximately .It first became extinct in Africa some 1.5 million years ago...

, Smilodon might have also killed juvenile mastodon
American mastodon
The American mastodon is an extinct North American proboscidean that lived from about 3.7 million years ago until about 10,000 BC. It was the last surviving member of the mastodon family. Fossil finds range from present-day Alaska and New England in the north, to Florida, southern...

s and mammoth
Mammoth
A mammoth is any species of the extinct genus Mammuthus. These proboscideans are members of Elephantidae, the family of elephants and mammoths, and close relatives of modern elephants. They were often equipped with long curved tusks and, in northern species, a covering of long hair...

s.
Smilodon may also have attacked prehistoric humans, although this is not known for certain. The La Brea tar pits
La Brea Tar Pits
The La Brea Tar Pits are a cluster of tar pits around which Hancock Park was formed, in the urban heart of Los Angeles. Asphaltum or tar has seeped up from the ground in this area for tens of thousands of years. The tar is often covered with water...

 in California trapped hundreds of
Smilodon in the tar, possibly as they tried to feed on mammoths already trapped. The Natural History Museum of Los Angeles County
Natural History Museum of Los Angeles County
The Natural History Museum of Los Angeles County opened in Exposition Park, Los Angeles, California, USA in 1913 as the Museum of History, Science, and Art. The moving force behind it was a museum association founded in 1910. Its distinctive main building, with fitted marble walls and domed and...

 has many of their complete skeletons.

Modern big cats kill mainly by crushing the windpipe of their victims, which may take a few minutes.
Smilodon’s jaw muscles were probably too weak for this and its long canines and fragile skull would have been vulnerable to snapping in a prolonged struggle or when biting a running prey. Research in 2007 concluded that Smilodon most likely used its great upper-body strength to wrestle prey to the ground, where its long canines could deliver a deep stabbing bite to the throat which would generally cut through the jugular vein and/or the trachea
Vertebrate trachea
In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...

 and thus kill the prey very quickly. The leaders of this study also commented to scientific journalists that this technique may have made
Smilodon a more efficient killer of large prey than modern lions or tigers, but also made it more dependent on the supply of large animals. This highly specialized hunting style may have contributed to its extinction, as Smilodon’s cumbersome build and over-sized canines would have made it less efficient at killing smaller, faster prey if the ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

 changed for any reason. A later study concurred, finding that the forelimbs of
Smilodon, more than those of any modern felid, were capable of minimizing the struggles of prey and positioning them for a quick kill with the predator's canines without them fracturing.

Research upon which African carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

s respond to playback of animals in distress has been used to analyse the finds of animal species and their numbers at the La Brea tar pits. Such playbacks find animal distress calls such as would come from an animal trapped in the tar pit
Tar pit
A tar pit, or more accurately known as an asphalt pit or asphalt lake, is a geological occurrence where subterranean bitumen leaks to the surface, creating a large area of natural asphalt.-Known tar pits:...

 would attract pack hunters such as lion
Lion
The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...

s and spotted hyena
Spotted Hyena
The spotted hyena also known as laughing hyena, is a carnivorous mammal of the family Hyaenidae, of which it is the largest extant member. Though the species' prehistoric range included Eurasia extending from Atlantic Europe to China, it now only occurs in all of Africa south of the Sahara save...

s, not lone hunters. Given the carnivores found at tar pits were predominately Smilodon and the social dire wolf
Dire Wolf
The Dire Wolf, Canis dirus, is an extinct carnivorous mammal of the genus Canis, and was most common in North America and South America from the Irvingtonian stage to the Rancholabrean stage of the Pleistocene epoch living 1.80 Ma – 10,000 years ago, existing for approximately .- Relationships...

, this suggests that the former like the latter was also a social animal. One expert, who found the study convincing, further speculated that if that was the case, then
Smilodons exaggerated canine teeth might have been used more for social or sexual signaling
Signalling theory
Within evolutionary biology, signalling theory is a body of theoretical work examining communication between individuals. The central question is when organisms with conflicting interests should be expected to communicate "honestly"...

 than hunting. However, the lack of sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

 in the canine teeth makes this unlikely.

The social hypothesis


It had long been assumed that machairodonts were solitary, but the idea had no foundation or factual basis, though without any suggestion otherwise, it was widely regarded as true for over 150 years. But when odd occurrences began to be discovered, those suggestions arose and paleontologists reconsidered the old idea of a lone saber-toothed cat.

In the process of creating inferences in behavior in animals long extinct, a large majority the case is made with reference with modern species. Hard facts are hard to come by, and most of the suggestions for a certain behavioral quality, such as sociability, come from situations that modern, observable species undergo that can be placed on the extinct species. The first concept that jarred the idea of a solitary machairodont began with California's Smilodon bonebeds and almost the entire case is rooted in observations in extant ecosystems and species.

One of the first places the social hypothesis found a home with was in comparing the number of specimens La Brea Tar Pits, ecology, behavior of carnivores to result in the concept that Smilodon, and possibly other machairodonts, were social animals hunting in groups.

Forming the La Brea tar pits ecological argument


One of the most abundant sources of machairodont fossils in one locality is the La Brea tar pits
La Brea Tar Pits
The La Brea Tar Pits are a cluster of tar pits around which Hancock Park was formed, in the urban heart of Los Angeles. Asphaltum or tar has seeped up from the ground in this area for tens of thousands of years. The tar is often covered with water...

 in Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...

. This rich fossil bed was at one time a pool of thick tar
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...

, or asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

, covered by water to form a small lake. When animals took a drink, they occasionally wandered into the lake, as seen in modern species to soothe skin or sometimes to relieve themselves of parasites, but their feet were caught in the tar, and with each step to try and free themselves, with one foot pulled up out of the tar, the other three sunk deeper. The pits did not kill an animal immediately. They could remain there for days before they died of starvation
Starvation
Starvation is a severe deficiency in caloric energy, nutrient and vitamin intake. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, death...

 or shock
Acute stress reaction
Acute stress reaction is a psychological condition arising in response to a terrifying or traumatic event...

. In the meantime, vocalizations and struggling attracted predators to the pits, which got themselves stuck as well. The La Brea tar pits are known as a predator trap for this reason. One stuck bison
Bison
Members of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...

 could attract a multitude of predators before expiring. In the pits, predators outnumber prey nine to one.

The machairodont Smilodon, with 13,000 specimens from some 2,000 individuals recovered, is one the most abundant fossils in the La Brea tar pits, second to the dire wolf
Dire Wolf
The Dire Wolf, Canis dirus, is an extinct carnivorous mammal of the genus Canis, and was most common in North America and South America from the Irvingtonian stage to the Rancholabrean stage of the Pleistocene epoch living 1.80 Ma – 10,000 years ago, existing for approximately .- Relationships...

 which is represented by 200,000 fossils representing 4,000 individuals. Smilodon was always regarded as a solitary species. The depictions of animals were like vultures to recent carcasses, with lone animals congregating on a kill and fighting over the remains with a gaping show of teeth. The idea that Smilodon lived a solitary life and found a dying animal caught in a tar pit and congregated, one by one, would suggest a very high number of predators in relation to prey.

Ecology and numbers


Robert Bakker, author of the Dinosaur Heresies, was one of the first to use the ecological laws of sizes of trophic level
Trophic level
The trophic level of an organism is the position it occupies in a food chain. The word trophic derives from the Greek τροφή referring to food or feeding. A food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves. The number of steps an organism...

s in an ecosystem to support a hypothesis. If his argument that dinosaurs were warm-blooded
Warm-blooded
The term warm-blooded is a colloquial term to describe animal species which have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes...

 like their avian relatives, he explains that "warm bloodedness is wasteful--so much energy is spent keeping the body warm. A one hundred pound guard dog (plus puppies) demands one thousand pounds of wet dog food per year for an active outdoor existence. But cold bloodedness is far cheaper. A one hundred pound guard lizard (plus hatchlings) is happy with only one hundred pounds of wet lizard chow per year". So, theoretically, for one thousand pounds of food, you can have one family of warm-blooded predators, or ten families of cold-blooded predators, and by measuring the ratio of dinosaurian predators to prey, it suggest warm-blooded ratios. This sort of ration, whether for high or low metabolisms, is what inhibits there being more numbers in a higher trophic level (predators) than a lower one (prey). In an accurate sample of an ecosystem, nine predators to every prey animal (view La Brea Tar Pits above) is not a possibility. Something must account for the artificial numbers of nine to one.
Then, of course, there is the sound factor. An animal who is panicked and dying, such as those trapped in the tar pits, will begin to emit calls, whether calling for members of its own species to aid it or out of frustration without a real purpose. These vocalizations can be heard over a large distance and any neighboring predators will hear the calls of animals in distress and be attracted to the potential easy meal.

A curious factor with this explanation is that species who are attracted to noise tend to be social. In east Africa, the sounds of the African painted dog, Lycaon pictus, usually indicate excitement, and often this excitement is over a kill. Lions, Panthera leo, are not the daring hunters most people imagine them to be but instead opportunists who steal at least as many kills from hyenas as they hunt for themselves, and hearing these calls that might mean food, they move towards the sounds to investigate the source of excitement. The solitary Panthera pardus, the leopard, is never seen approaching these sources of sound. Other solitary species, including cats such as the serval
Serval
The serval , Leptailurus serval or Caracal serval, known in Afrikaans as Tierboskat, "tiger-forest-cat", is a medium-sized African wild cat. DNA studies have shown that the serval is closely related to the African golden cat and the caracal...

 and cheetah
Cheetah
The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...

, do not approach these sounds either. The canids in the region, namely jackals, are semi-social with breeding pairs, but they stay away until only the bare scraps are left.

Research on carnivore responses to sound


A study concerning the attraction to sound displayed by social predators in Africa suggests that the abundance of Smilodon in the La Brea tar pits was due to their sociability. The animals attracted to the playbacks of dying herbivores combined with the sounds of lion
Lion
The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...

s and hyena
Hyena
Hyenas or Hyaenas are the animals of the family Hyaenidae of suborder feliforms of the Carnivora. It is the fourth smallest biological family in the Carnivora , and one of the smallest in the mammalia...

s were recorded. Carnivore species in the area were grouped into four main groups based on size and social status: large (greater than or equal to 21 kilograms) and social, large and solitary, small (less than 21 kilograms) and social, or small and solitary. Ages of the individuals investigating the sounds were compared with those of the Smilodon individuals located in the pits (assessed by presence of deciduous teeth in juveniles). Their mean results for Kruger National Park in South Africa and the Serengeti National Park and surrounding reserves in Tanzania, were as follows in table columns A and B:
Group A
Individual abundance
in African ecosystem

B
Individuals attending
African playbacks

C
North American individuals
in tar pits assuming
Smilodon solitary
D
North American individuals
in tar pits assuming
Smilodon social

Large and social

2 %

84 %

53 %

87 %

Large and solitary

1 %

1 %

36 %

2 %

Small and social

8 %

15 %

8 %

8 %

Small and solitary

89 %

0 %

3 %

3 %


The rationale for this attraction is that a species in distress can be heard by all the predators in the area. If every predator that heard the sounds were to come to the source, there would be intense competition between the species. Jackal
Jackal
Although the word jackal has been historically used to refer to many small- to medium-sized species of the wolf genus of mammals, Canis, today it most properly and commonly refers to three species: the black-backed jackal and the side-striped jackal of sub-Saharan Africa, and the golden jackal of...

s (small and social) and leopard
Leopard
The leopard , Panthera pardus, is a member of the Felidae family and the smallest of the four "big cats" in the genus Panthera, the other three being the tiger, lion, and jaguar. The leopard was once distributed across eastern and southern Asia and Africa, from Siberia to South Africa, but its...

s (large and solitary) would be killed but might come around to investigate, being careful and keeping a distance. Jackals are known to hang around, pushing their luck but inching closer as larger predators eat, waiting to grab a bite from under the larger animals' noses or until they leave to gnaw on the remains. The small, solitary group including badger
Badger
Badgers are short-legged omnivores in the weasel family, Mustelidae. There are nine species of badger, in three subfamilies : Melinae , Mellivorinae , and Taxideinae...

s, serval
Serval
The serval , Leptailurus serval or Caracal serval, known in Afrikaans as Tierboskat, "tiger-forest-cat", is a medium-sized African wild cat. DNA studies have shown that the serval is closely related to the African golden cat and the caracal...

s, civet
Civet
The family Viverridae is made up of around 30 species of medium-sized mammal, including all of the genets, the binturong, most of the civets, and the two African linsangs....

s, African palm civet
African Palm Civet
The African palm civet , also known as the two-spotted palm civet, is a small mammal, with short legs, small ears, a body resembling a cat, and a long lithe tail as long as its body. Adults usually weigh . It is native to the forests of eastern Africa, where it usually inhabits trees...

s, aardwolves
Aardwolf
The aardwolf is a small, insectivorous mammal, native to Eastern and Southern Africa. The name means "earth wolf" in Afrikaans/Dutch. It is also called "maanhaar jackal". It is related to hyenas, but unlike its relatives, it does not hunt large prey. This unusual animal preys on insects...

, genet
Genet
-Aircraft:*Armstrong Siddeley Genet, aircraft engine*Armstrong Siddeley Genet Major, aircraft engine-Animals and Plants:*Genet , a colony of plants, fungi or bacteria that come from a single genetic source....

s, and caracal
Caracal
The caracal is a fiercely territorial medium-sized cat ranging over Western Asia, South Asia and Africa.The word caracal comes from the Turkish word "karakulak", meaning "black ear". In North India and Pakistan, the caracal is locally known as syahgosh or shyahgosh, which is a Persian term...

s would not only be killed, they’d become part of the menu and so they, as suggested by the numbers, no not ignore the calls but use them as a warning to leave the area immediately because larger, dangerous predators are coming in large numbers. Lions (large and social), aided by numbers and strength, would be the most powerful in the congregation and other predators who would come would be killed or injured. The only other predator that might match the lions’ strength and numbers would be the hyenid Crocuta, the spotted hyena. Hyenas challenge lions on a regular basis at kills and are often attracted to the same calls of distressed animals. The two social species shoulder their way around with lions usually on top, and all other predators who know they don’t have a shot abandon the area to avoid getting caught up in the struggle.

To further the explanation, the remains from the La Brea tar pits were sorted into same categories as for the African ecosystems. The individuals in the La Brea tar pits are not a good sample of the ecosystem, but are equivalent to the playback tests, so the numbers in each situation were compared (carnivore numbers in the pits, African carnivore numbers attending playbacks). Assuming that Smilodon was solitary gives the results in column C above. Assuming Smilodon was social alters the results to those of column D above. These last two columns, when compared to column B displaying African carnivore ratios, help to support the social hypothesis: the percentages of the North American ecosystem (small social, small solitary, large social, large solitary) is much closer to the same relative percentages in the African ecosystems when assuming that Smilodon was social, not solitary.

Living in groups might also allow more effective competition with social lion
American lion
The American lion — also known as the North American lion, Naegele’s giant jaguar or American cave lion — is an extinct lion of the family Felidae, endemic to North America during the Pleistocene epoch , existing for approximately...

s and wolves
Dire Wolf
The Dire Wolf, Canis dirus, is an extinct carnivorous mammal of the genus Canis, and was most common in North America and South America from the Irvingtonian stage to the Rancholabrean stage of the Pleistocene epoch living 1.80 Ma – 10,000 years ago, existing for approximately .- Relationships...

. Though many social species are sexually dimorphic, Smilodon was not. The canines of males and females were the same length and there seemed to be no size differences, which suggests a social structure more like that of the modern grey wolf than the modern lion. This is also a slight hint at a form of monogamy
Monogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...

, as seen in modern jackals, as opposed to the polygamy
Polygamy
Polygamy is a marriage which includes more than two partners...

 seen in lions.

Damaged bones and paleopathology



Evidence of sociability can be seen even in the fossils themselves. When an animal stressed its body beyond its abilities to cope, damage is sure to ensue. Smilodon bones often show fractures and deformities. Muscles tearing from bones are not particularly uncommon in this predator. Hunting large prey can stress an animal to this point. What is curious about these wounds is that they heal. A muscle torn from a bone heals and tears again and heals and tears again, leaving the body to struggle to stop the cycle by laying down thick deposits of calcium, warping the bone into having large lumps of bone jutting from the norm and broken bones heal badly, but refuse and the animal lives on. In solitary animals, such as the modern cheetah
Cheetah
The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...

, Acinonyx, a simple sprain is enough to inhibit the predator’s hunting to the point that it will starve to death. Hunting with an able body is hard enough. A broken bone would never heal because the animal would die before the body could repair the damage. Smilodon seemed to have suffered great injuries and survived the healing stage to recover and hunt again. The large genus Machairodus
Machairodus
Machairodus was a genus of large machairodontine saber-toothed cats that lived in Europe, Asia, Africa and North America during the Miocene through Pleistocene living from 11.6mya—126,000 years ago, existing for approximately .-Species:...

often displays broken canines that are worn due to extensive usage after the break, along with Smilodon.

One specific case of fossil deformity is the observed large pelvic fractures that healed in a subadult Smilodon fossils with extensive myositis ossificans tramatica, immobilizing the juvenile completely until healed months later, and even when healed it would have been crippled terribly. The muscle damage was severe and blood would have pooled beneath the skin in the injury. During this extended period of several months, it could not run and walking would have been very tiring and painful. It would have had food brought directly to it, carried from a kill site to where the injured animal lay. This behavior has been observed in lionesses (Schaller, 1972) for up to nine months.

A modern study of bones has used paleopathology to evaluate the lives of the living animals using 5,000 deformed fossils. Paleopathology is the study of diseased and injured animals in the fossil record and is studied through bones distorted from breaks, strains, chips, swelling, calcium buildup, marks from bites, etc. These bones suggest injuries that would debilitate an individual through the presence of broken and worn canines, chipped incisors and premolars, arthritis
Arthritis
Arthritis is a form of joint disorder that involves inflammation of one or more joints....

, infection with a fungus that causes Valley Fever, a severely infected hip, and a half-broken neck. Muscles that are repeatedly damaged leave knobby growths on the bone when the body struggles to heal and strengthen the bone. By noticing specifically where the repeated injuries occur, it is possible to tell what muscle were being strained the most and lead to hunting theories (Main article: Hunting Strategies: Injuried Muscles, Machairodontinae
Machairodontinae
Machairodontinae is an extinct carnivoran mammal subfamily of Felidae endemic to Asia, Africa, North America, South America, and Europe from the Miocene to Pleistocene living from c. 23 Ma until c...

).

Extinction


Smilodon became extinct at the end of the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 around 10,000 BC, a time which saw the extinction of many other large herbivorous and carnivorous mammals.

Prehistoric humans, who reached North America at the same time and are known to have hunted many of the species that disappeared, are often viewed as responsible for this extinction wave. Others have suggested that the end of the ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

 caused the extinction. As the ice sheets retreated there would have been changing vegetation patterns. Grasslands expanded. The summers became more extreme and parts of North America began to dry out. However, this hypothesis does not explain why Smilodon and its ancestors as well as other megafaunal species successfully survived many previous interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...

s, and then fairly suddenly died out over the entire contiguous land area of North and South America.

External links