Dire Wolf, Canis dirus
July 2009

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*How Do We Know This? Like living animals, fossil remains of once-living animals are
classified and grouped according to their relationships to each other and to their ancestors.

(ITIS 2010) (Anyonge & Roman 2006) (Lindblad-Toh et al 2005) (McKenna & Bell 1997) (Tedford et al 2009) (Wilson & Reeder 2005) (Wang et al 2004)

Describer (Date): Leidy 1858 for Canis dirus. Linnaeus 1758 for genus Canis

Kingdom: Animalia
    Phylum: Chordata
        Class: Mammalia
             Order: Carnivora
                   Suborder: Caniformia (dog-like carnivores; includes many extinct families)
                          Family: Canidae (dogs, coyotes, foxes, jackals, wolves; many extinct genera)
                               Genus: Canis (6 living species)
                                  Species: Canis dirus EXTINCT
                                      Subspecies: Canis dirus guildayi   EXTINCT
                                      Subspecies: Canis dirus dirus    EXTINCT                  
                   Suborder: Feliformia (cat-like carnivores; many extinct families)

Taxonomic History and Nomenclature

Phylogeny (Wang et al 2004) (Tedford et al 2009) (Lindblad-Toh et al 2005)

*How Do We Know This? Scientists make sense of fossil
distribution patterns using knowledge of the earth's rocks, global plate
tectonic movements, plus genetic and phylogenetic studies.
Ancient habitats are revealed by studies of modern environments where sediments
are deposited, taking into account the chemical processes of fossilization.

(Anyonge & Baker 2006) (Coltrain et al 2004) (Dundas 1999) (Hodnett et al 2009) (Hunt 1996) (Prevosti & Rincon 2007) (Stock & Harris 1992)

Prehistoric Distribution Habitat

*How Do We Know This? Careful study of fossil bone or tooth anatomy yields
much exact information about placement and strength of muscles, tendons,
ligaments, nerves, and blood vessels. In rare cases, scales, skin, nails or hairs leave impressions
in sediments. Even more rarely, actual skin, nails, or hair is preserved. Body weight is more difficult
to gauge because fat leaves no impression on the skeleton.

(Turner & Anton 1997) (Anyonge et al 2003) (Anyonge & Baker 2006) (Anyonge & Roman 2006)

Estimated Body Weight: 34-67kg (75-148 lb) (Anyonge & Roman 2006)
Head/Body Length: 125 cm (4.1 ft) (Anton & Turner 1997)
Height at Shoulder: 80 cm (2.6 ft)
Tail Length: 63 cm (2 ft)

General Description
Teeth Pelage Sexual Dimorphism Other Physical Characteristics

*How Do We Know This? Since direct observation of a fossil animal's behavior
isn't possible, paleontologists use comparison and contrast with living animals for
guidance. Tracks can sometimes reveal further clues. Associated animals and
plants found at a fossil site can suggest predator/prey dynamics and dietary options.

(Binder et al 2002) (Hodnett et al 2009) (Van Valkenburgh et al 1990) (Van Valkenburgh & Hertel 1993) (Van Valkenburgh & Sacco 2002)

Social Life (Van Valkenburgh & Sacco 2002)
  • Large numbers of dire wolves preserved at La Brea suggest they lived in large groups.
    • Probably the deposits didn't represent solitary individuals feeding successively
    • More than 3,000 individuals represented in several tar pits.
  • Probably monogamous, living in packs like modern gray wolves
    • Male and females' teeth and skeletons are similar (little dimorphism)
    • In modern animals, amount of sexual dimorphism correlates with the animal's breeding system
      • When males' canine teeth much larger, males compete strongly for females and breeding system may be polygamous
      • When both sexes have similar canine teeth, typically have low level of male-male competition and pair-bonded breeding system as in African wild dogs, dholes, gray wolves.        
Interspecies Interaction
  • Many other species of dog-like carnivores found in fossil sites with dire wolves. (Hodnett et al 2009)
    • Coyotes, timber wolves, Asiatic wild dogs at San Jacinto Cave (Nuevo Leon, Mexico)
    • Coyotes, domestic dogs, gray foxes, and timber wolves at La Brea asphalt deposits
  • Lack of tooth wear scratches on Smilodon suggests they many have left large portions of their kills (Van Valkenburgh et al 1990)
    • A co-evolutionary relationship with dire wolves (who could finish eating the kills) proposed by researchers.
  • Between 15,000 and 12,000 years ago dire wolves may have undergone changes in feeding habits (Van Valkenburgh & Hertel 1003) (Binder et al 2002)
    • Earlier fossils show more tooth breakage, perhaps signifying more bone-chewing of kills
    • Later fossils (at 12,000) years ago show less bone consumption and less breakage.
    • Less bone consumption most likely reflects less competition with other predators for kills as numbers of all these large animals declined.

*How Do We Know This? Clues to fossil mammals' diets come from not only teeth,
but also skull shape, from fossil dung and gut contents, from microscopic viewing of
wear on teeth, from lab analysis of oxygen, carbon, and nitrogen isotopes in bone and teeth, and by looking
at diets of similar modern animals.

(Anyonge & Roman 2006) (Coltrain et al 2004) (Ewer 1973) (Fox-Dobbs et al 2003) (Fox-Dobbs et al 2007) (Harris et al 2004) (Hodnett et al 2009) (Therrien 2005) (Van Valkenburgh & Ruff 1987) (Van Valkenburgh 1998) (Van Valkenburgh & Sacco 2002)
  • Calculated bite force: (Therrien 2005)
    • 129% of modern gray wolves
    • 64% of the extinct American lion
  • Often took large prey, as inferred from:
    • Large body size
    • Carnivorous, meat-eating dentition
  • Some researchers suggest that, like many canids, probably hunted in packs, normally subdued prey with many shallow, debilitating bites (Ewer 1973) (Therrien 2005)
  • Other researchers note that teeth and jaws may also have held struggling prey (Van Valkenburgh & Ruff 1987)
    • Dire wolves had great degree of roundness and greater bending strength in canine teeth, when compared with modern wolves (prey must have not been subdued immediately).
    • Smilodon, by contrast had more delicate teeth that probably didn't come in contact with the prey's bones (used powerful front limbs to subdue prey)
  • Studies of twisting and stress forces generated at different points of carnivore jaws reveal: (Therrien 2005)
    • Like other canids, dire wolves' lower jaws fortified behind the slicing carnassial molars (for bone-crushing),
    • Dire wolves could crush bones, but not as well as modern wolves
    • When dire wolves compared to large cats, bite force not as strong in the front of the jaw (where cats use the canine for a killing bite)
  • Were not specialized predators, fed on whatever megafauna were most abundant. (Fox-Dobbs et al 2007)
    • Horses were important prey; sloth, mastodon, bison and camel were less common prey.
  • Fed on medium to large hoofed animals. (Hodnett et al 2009)
    • Ate both ruminants and non-ruminants (Coltrain et al 2004)
    • Maximum prey size would have been 300-599 kg (Anyonge & Roman 2006) (Van Valkenburgh & Hertel 1998)
    • A pack of dire wolves could even have preyed on adult bison. (Anyonge & Roman 2006)
  • May have also supplemented diet with smaller prey species (Fox-Dobbs et al 2003)
  • Extinct dire wolves, saber-tooth cats, and American lions all competed for similar prey. (Coltrain et al 2004)
    • According to nitrogen isotope values of bone
    • Large numbers of broken teeth suggest high levels of competition for carcasses. (Van Valkenburgh 1998)
  • May also have scavenged large portions of prey that Smilodon didn't finish.

*How do We Know This? Abnormalities in fossils bones may show evidence
of arthritis, cancer, nutritional stress, fractures and more.

(Duckler & Van Valkenburgh 1998) (Binder et al 2002)

  • In a study of the general health of several Pleistocene animals (as revealed by x-rays of their bones), dire wolves' health appeared no different than that of modern healthy populations of carnivores.
    • Bone x-rays can show lines where normal growth is halted and later resumed (called Harris lines)
    • Frequency of Harris lines very low, similar to health wolves on Isle Royale,
  • Dental enamel of fossil dire wolves from La Brea tar seeps show almost no defects; a healthy population is indicated even shortly before their extinction.
  • Tooth breakage commonly seen in fossils from La Brea (Binder et al 2007)
    • Broken teeth a feature of living carnivores that often crack large bones.
    • Tooth breakage data in fossils must be combined with accurate estimates of an animal's age (so that estimates of breakage are independent of an animal's age)
  • Dire wolf fossils from La Brea at 15,000 years ago show more tooth breakage than ones from 12,000 years ago. (Binder et al 2002)
    • Perhaps this reflects more complete consumption of carcasses at 15,000 years ago and more competition with other predators than at 12,000 years ago when predator densities may have been lower.

Important Web Resources (and where to view fossils in museums):
  • Natural History Museum of Los Angeles County's George C. Page Museum has a web site introducing many of the region's Late Pleistocene animals, including Dire Wolves. The Page Museum at Rancho la Brea displays most of the iconic large mammal fossils and a large number of rarely seen bird fossils from Late Pleistocene times. Visitors can view technicians working in a large fossil preparation lab.
  • San Diego Natural History Museum Has a skeletal mount of a Dire Wolf and murals with Dire Wolves by artist William Stout. The museum's displays include many Late Pleistocene fossils plus original oil murals of the flora and fauna in southern California about 20,000 years ago. Museum's web site's Fossil Field Guide has descriptions of many extinct animals from southern California, including dire wolves.
  • New Mexico Museum of Natural History Two skeletal mounts of dire wolves in front of a Pleistocene mural showing dire wolves in a natural habitat.
  • The Paleobiology Database: This site is a scientific organization run by paleontological researchers from around the world. It features taxonomic and distribution information for the entire fossil record.
  • National Museum of Natural History (Smithsonian): Good fossil skeleton of Dire Wolf in Ice Age Hall.

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