Dire Wolf, Canis dirus

The dire wolf (Canis dirus) is an extinct wolf that was most common to North and South America. This carnivorous mammal lived for approximately 1.79 million years, existing throughout the Irvingtonian stage to the Rancholabrean stage of the Pleistocene era. It is related to the grey wolf, although it was larger and has no direct line to any living species.

In 1854, the type specimen of the dire wolf was found in Evansville, Indiana. Joseph Granville Norwood acquired the specimen, a jawbone, from Evansville collector Francis A. Linck. Norwood, the first state geologist at that time, sent the jawbone to the Academy of Natural Sciences in Philadelphia in 1854, where Joseph Leidy concluded that it belonged to an extinct genus of wolf, which he called Canis dirus in an 1858 publication. Letters between Norwood and Linck, as well as the specimen, can be found at the Academy of Natural Sciences, although one letter states that the jawbone was to be given to Linck’s family after his passing in 1854.

The dire wolf has three synonyms, all found to be the dire wolf. Canis dirus was recombined as Aenocyon dirus by Merriamin 1918, Hibbard in 1949, and Hibbard and Taylor in 1960. Sellards named Canis ayersi in 1916, and this was also recombined in 1918 by Merriam, as Aenocyon ayersi, which was later synonymized by Lundelius in 1972, Martin in 1974, Nowak in 1979, Kurten and Anderson in 1980, and Kurten in 1984. In 1869, Leidy named the dire wolf Canis indianensis and Troxell synonymized this in 1915. In 1876, the dire wolf was named Canis mississippiensis which was synonymized with C. dirus by Nowak in 1979, Kurten and Anderson in 1980, and once more by Kurten in 1984.

The dire wolf is commonly known from its many discoveries at the La Brea tar pits in California, numbering over 3600. There have been more dire wolf specimens found than any other species of mammal. From these discoveries, it can be surmised that dire wolves probably hunted in packs and shows the pressures these wolves may have gone through towards the end of their existence.

The dire wolf measured an average of five feet in length and could have weighed between one hundred and ten pounds to one hundred and seventy-four pounds. Although the grey wolf and the dire wolf are not directly related, there are no significant differences between the two species. The brain casing of the dire wolf is smaller than that of the grey wolf, even a grey wolf similar in size. The legs of the dire wolf have also been found to be shorter and stouter than those of the grey wolf.  The teeth of the dire wolf are slightly larger than grey wolf teeth.

The diet of the dire wolf consisted mainly of meat, as studies of the teeth have found. It was most likely hypercarnivorous, eating at least seventy percent meat, or mesocarnivorous, eating at least fifty to seventy percent meat. It is thought that the dire wolf may have crushed bone, due to the amount of wear on the crowns of its fossilized teeth. The upper carnassials in the dire wolf were much sharper than those of the grey wolf. These sharp upper teeth were very good at slicing through bones. It is thought that the dire wolf could use greater force when chomping down than the grey wolf, due to the longer temporal fossa and wider cheekbones.

Some scientists have disputed the claims that the dire wolf could crush bone, saying that the amount of force the wolves could use was no different than coyotes or African wild dogs. This may indicate that the dire wolf had a similar diet to those smaller canids. It is also thought by some that the teeth of the dire wolves did not have the proper adaptations to crush bone, like hyenas. Through evidence found in the outer parts of the jawbone it has been surmised that the dire wolf probably hunted in packs, using a less forceful means of killing its prey.

It is though that the dire wolf may have branched off from genus of the smaller foxlike creature called Leptocyon nine to ten million years ago in the late Miocene epoch. Two other genera called Urocyon and Vulpes were thought to have branched out with the dire wolf.  During the Middle Pleistocene, North American wolves developed a large diversification. From this, C. armbrusteri was created, and it is thought that the dire wolf evolved from it. Evidence shows that the two lived in the same open plains areas of the United States, and that the dire wolf pushed C. armbrusteri out of that territory, leaving it with a range in the southeastern United States. During this period, the dire wolf expanded its range into Central and South America.

The dire wolf is included in the Pleistocene megafauna, an abundant group of mammals that lived during that time. Approximately 300,000 years ago, the grey wolf came to North America using the Bering Strait land bridge. The dire wolf and grey wolf vied for food and territory.  When the majority of large mammals began to die out (about sixteen thousand years ago), the slower dire wolf had to learn to scavenge while the more agile grey wolf could hunt smaller creatures. It is thought that (along with human caused changes),through this competition against mainly red wolves and grey wolves, the dire wolf was not able to survive and was extinct by ten thousand years ago.

Image Caption: Skeleton of a dire wolf, Canis dirus, in the George C. Page Museum at the La Brea Tar Pits, Los Angeles, California. Credit: WolfmanSF/Wikipedia(CC BY-SA 3.0)