Extinct Short-faced Bear (Actodus spp.) Fact Sheet: Diet & Feeding

Clues to fossil mammals' diets come from teeth,skull shape, from fossil dung and gut contents, from lab analysis of isotopes in bone and teeth, and by looking at diets of similar modern animals.

Diverse diet

• Ate large animal carcasses, plants, and small animal prey
• Plant-eating (and tree climbing) habits are also suggested by the short-faced bear's somewhat opposable thumb (helps in grasping, pulling and holding plants) and tall molar teeth (which indicate high biting forces typical of herbivorous species)
• Coarse plants consumed non-discriminately; not a selective browser because of wide muzzle. (Sorkin 2006)
• Tooth wear patterns are similar to that of the spectacled bear (Tremarctos ornatus), its closest living relative (Donohue et al. 2013)

Ecological role

• Didn't have the skull or skeletal adaptations for ambush or pursuit of large mammals. (Sorkin 2006)
• May have occupied the same ecological role, feeding habits, and body shape as the modern striped and brown hyaenas. (Sorkin 2006)

Differing interpretations of Arctodus feeding habits

• A top predator due to its large size and dentition which appears like that of a carnivore. (Kurtén 1988)
• A hypercarnivore, feeding on a wide variety of herbivores according to stable isotopes in bone of carbon and nitrogen (Matheus 1995, Matheus et al 2002, Bocherens et al 2006)
  • But Sorkin (2006) notes brown bear fossils from the Pleistocene have a similar isotope reading and they are not strictly carnivores - are instead omnivores.
• A scavenger (Matheus et al 2000)
  • Articulation of bones do not allow flexibility required of a successful predator
  • Pacing gait suggests endurance, not speed that a predator would need
  • Limbs are somewhat slender, not massive for great strength
  • Powerful jaws capable of crushing bone
  • But such a large animal wouldn't have evolved into being primarily a scavenger in an environment with vultures (Ruxton & Houston 2004)
    • Aerial scavengers held too big an advantage in rapidly locating carrion; large earth-bound scavengers need alternate food supplies.
• Most likely feeding style: an adaptable omnivore (scavenging and hunting hunting animals and consuming plants too) based on new studies of skull shapes of living bears with known food habits (Figueirido et al 2009, 2010)

Barnes et al (2002)
Bocherens et al (2006)
Donohue et al. (2013)
Figueirido et al (2009)
Kurtén (1988)
Matheus (1995)
Matheus et al (2002)
Richards et al (2008)
Ruxton & Houston (2004)
Sorkin (2006)