Name: Aenocyon
dirus
.
Phonetic: Kay-niss dih-rus.
Named By: Joseph Leidy - 1858.
Synonyms: Aenocyon ayersi, Canis ayersi,
Canis indianensis, Canis mississippiensis.
Classification: Chordata, Mammalia, Carnivora,
Canidae, Canis.
Species: A. dirus (type). Sub
species Aenocyon dirus dirus, Aenocyon dirus
guildayi.
Type: Roughly comparable to the gray wolf at around
85 centimetres high at the shoulder, but significantly more robust in
general build. Some fossils suggest very large individuals approached
about 95 centimetres high at the shoulder.
Known locations: Throughout the USA. Parts of
Latin and South America including, Bolivia, Mexico, Peru and
Venezuela.
Time period: Calabrian through to the Tarantian of
the Pleistocene.
Fossil representation: Thousands of individuals.
Dire
wolves are extremely well known and are the single most common species
of animal found at the world famous Rancho La brea Tar Pits. For
a time of about one-hundred thousand years, the ranges of the dire
wolf
and gray wolf (Canis lupus) overlapped, and the
two coexisted together. The dire
wolf however was larger and more powerfully built than the gray, and
it’s thought that the two wolves focused upon different prey groups,
thus avoiding direct competition with one another. Because
the gray wolf was smaller and more lightly built, it probably went
for swifter and lighter prey items such as elk. Dire wolves however
had a much more robust skeleton which indicates the presence of much
more powerful and
larger muscles. The skull is also proportionately wider indicating
stronger bite muscles. These adaptations in a predator are the
tell-tale signs of a hunter that primarily concerned itself with larger
and more powerful prey.
Further
insights into dire wolf prey specialisation can be obtained through
isotope analysis. This process involves sampling a fossil, a
destructive process that involves the sample being crushed, and then
measured with a mass spectrometer to reveal the isotropic signature.
These signatures can be found in plants, the herbivores that ate
them, and the carnivores that in turn ate the herbivores. They can
also be
combined to recreate an environment revealing who ate what and who ate
whom. The analysis for dire wolves indicates that their primary diet
was made up of a combination of horses and bison. Only a small
fraction was made up by other creatures, and this may have been
through scavenging carcasses as opposed to hunting different animal
species.
Dire
wolves are generally considered to have been pack hunters like the gray
wolves that were also active at the time. Exactly how dire wolves
behaved with one another is not one hundred per cent clear, but clues
can be gleaned from the large amounts of available fossil evidence. The
huge amount of fossils recovered from Rancho La Brea have been
interpreted by some that the dire wolf formed very large packs, that
may in fact have featured more pack members than the packs formed by
gray wolves that are active today and average four to seven wolves a
pack, although the number of individuals can be much higher. Larger
packs and larger individuals would need increased amounts of
sustenance, again pointing to a large prey specialisation, such as
bison.
Many
dire wolf fossils show signs of horrific injuries including completely
broken fore legs and partially crushed skulls. Remarkably however,
many of these injuries actually healed with some of the fossils
displaying evidence that the wolves in question lived for months and
even years after the injury happening. Furthermore, many of these
specimens were recovered from Rancho La Brea, leading to the fact
that the dire wolves in question died as a result of being stuck in the
tar and not of the injury.
These
types of injuries would almost certainly be the death of a solitary
predator as they would be enough to prevent any animal from actively
hunting. As a pack member, an injured dire wolf may have been able
to drag itself to a kill, although it may have had to wait for the
others to finish. Some have even speculated that the healthier wolves
may have helped the injured by bringing them food while they
recovered. In comparison, this behaviour is not known in the gray
wolf, but is seen in Lions. A strong pack helps ensure the survival
of all members, and if the above ever proves correct, it would be
another example of the same behaviour being exhibited across two
separate animal species. Many
dire wolf skulls also show teeth marks in the bone from where another
dire wolf has caught it in its jaws. This is suggestive of dominance
behaviour in a group, as face and head biting is commonly seen in
many pack living carnivores, including the gray wolf.
The
severe lack of dire wolf pups in the fossil record is taken as a sign
that the young were kept away from actively participating in hunts.
This is also seen in today’s wolves in what is usually referred to as
a 'rendezvous point'. While the pack hunts, the pups stay at
the rendezvous point awaiting the pack to return with food. Only when
they are older do they begin travelling with the other pack members and
participating with the hunts.
The
dire wolf disappears from the fossil record at around ten-thousand
years ago, the same time that much of the American Pleistocene
megafauna such as Smilodon
also disappeared. There are many theories
as to what caused the extinction of the megafauna, from an
environment that changed too much too fast, to a comet exploding in
space above North America. One occurrence that does correspond with
the disappearance is the arrival of the first humans in North America
by crossing the Bering land bridge that at the time connected North
America to Asia. Theories associated with this arrival include being
out competed by humans for available food sources, to humans bringing
new strains of bacteria and disease with them, that the existing
North American animals had no natural resistance against.
Whatever
the exact cause or causes may be, the only relatively safe thing
that can be said about the disappearance of dire wolves is that if was
almost certainly connected with the reduction and loss of their
favoured prey species. Without these, the dire wolf would have had
to hunt smaller prey that was probably faster, and provided less
sustenance than the heavily built dire wolf required. But since the
gray wolf was already suited to these types of prey, it survived into
the modern era.
A
2021 study (Perri et al) tested DNA samples
from dire
wolves. The result of these tests was that at a DNA level, Dire
wolves were actually different to those of the Canis lineage. This
led to the establishment of the Aenocyon genus for Dire wolves.
Further reading
- Temporal variation in tooth fracture among Rancho La Brea dire
wolves. - Journal of Vertebrate Paleontology 22 (2): 423. - W. J.
Binder, E. N. Thompson & B. Van Valkenburgh - 2002.
- Sexual dimorphism, social behavior, and intrasexual competition in
large Pleistocene carnivorans. - Journal of Vertebrate Paleontology 22:
164 - B. Van Valkenburgh & T. Sacco - 2002.
- Bite club: Comparative bite force in big biting mammals and the
prediction of predatory behaviour in fossil taxa. - Proceedings of the
Royal Society B: Biological Sciences 272 (1563): 619–25. - S. Wroe, C.
McHenry & J. Thomason - 2005.
- New body mass estimates for Canis dirus, the
extinct Pleistocene dire
wolf. Journal of Vertebrate Paleontology 26: 209. - W. Anyonge&
C. Roman - 2006.
- Craniofacial morphology and feeding behavior in Canis dirus,
the
extinct Pleistocene dire wolf. - Journal of Zoology 269 (3): 309–316. -
W. Anyonge & A. Baker - 2006.
- Carnivore-specific stable isotope variables and variation in the
foraging ecology of modern and ancient wolf populations: case studies
from Isle Royale, Minnesota, and La Brea - Canadian Journal of Zoology
85: 458-471 - K. Fox-Dobbs, J. K. Bump, R. O. Peterson, D. L. Fox
& P. L. Koch - 2007.
- Megafaunal Extinctions and the Disappearance of a Specialized Wolf
Ecomorph - vol 17 issue 13, p1146-1150. - Jennifer A. Leonard, Carles
Vila, Kena Fox-Dobbs, Paul L. Koch, Robert K. Wayne & Blair Van
Valkenburgh - 2007.
- Quaternary records of the dire wolf, Canis dirus,
in North and South
America. - Boreas 28 (3): 375–385. - R. G. Dunda - 2008.
- Dire Wolf, Canis dirus (mammalia; Carnivora;
Canidae), from the Late
Pleistocene (Rancholabrean) of East-Central Sonora, Mexico. - The
Southwest Naturalist 54 (1): 74–81. - John-Paul Hodnett, Jim I. Mead
& A. baez - 2009.
- Dire Wolf, Canis dirus (Mammalia; Carnivora;
Canidae), from the Late
Pleistocene (Rancholabrean) of East-Central Sonora, Mexico - The
Southwestern Naturalist 54.1: 74–81. - John-Paul M. Hodnett, Jim I.
Mead, A. Baez - 2009.
- A comparison of tooth wear and breakage in Rancho La Brea sabertooth
cats and dire wolves across time. - Journal of Vertebrate Paleontology
30 (1): 255–261. - Wendy J. Binder & Blaire Van Valkenburgh -
2010.
- The carnivoran fauna of Rancho La Brea: Average or aberrant?. -
Palaeogeography, Palaeoclimatology, Palaeoecology. 329-330: 118–123. -
Brianna K. McHorse, John D. Orcutt & Edward B. Davis - 2012.
-
Cranial morphometrics of the dire wolf, Canis dirus, at Rancho La Brea:
temporal variability and its links to nutrient stress and climate. -
Palaeontologia Electronica. 17 (1): 1–24. - F.Robin O'Keefe, Wendy J.
Binder, Stephen R. Frost, Rudyard W.Sadlier & Blaire Van
Valkenburgh - 2014.
- Dire wolves were the last of an ancient New World canid lineage. -
Nature. 591 (7848): 87–91. - Perri et al - 2021.