Feral Hog Tusk Characteristics

Feral Hogs May 16, 2012 Print Friendly and PDF

The tusks of feral hogs (also called wild hogs; Sus scrofa) have long been a physical feature of these animals that has garnered significant interest from both the sport-hunting and general publics.  These teeth, technically called canine teeth (as they are in all mammals that have them), have both deciduous (i.e., temporary, “baby” or “milk”) and permanent sets.  The permanent tusks, especially in boars, represent a major element of the trophy quality of a feral hog.  It is also the single element of the feral hog’s physique that makes these animals so dangerous to both humans and animals alike.  These tusks have an anecdotal aura about them that is composed of both fact and fiction.  The following is a summary of the known information associated with these specialized teeth. 

In vernacular or slang jargon, these teeth are also called tushes.  Similarly, the lower tusks, especially in boars, are locally called cutters, because these teeth tend to be very sharp at the tips, and as such, are used by the animal for cutting a rival, prey, or predator.  The upper tusks are referred to as whetters (taken from the term “whetstone,” which is a sharpening stone used for knives and other cutting tools), because these teeth primarily function to sharpen the lower tusks.  This latter term is often misspelled as wetters.

Feral hogs of both sexes are born with their deciduous canine teeth.  These consist of two upper and two lower teeth, which are small, needle-sharp conical structures.  These are lost (shed) when the permanent tusks erupt at about 7 to 13 months of age.  Although the upper teeth can appear first (by a few days), the two sets of permanent tusks in most animals appear at approximately the same time.  The permanent tusks in both sexes project out of the sockets in the form of curved teeth as they grow with age.  The lower tusks of both sexes extend in a forward and somewhat lateral direction out of the socket, curving upward, and in some older males, backward and toward the lower jaw.  In boars, the upper canines extend in a forward and lateral direction out of the socket, then curve upward and occasionally back toward the snout.  The upper canines of sows extend in a downward and lateral direction out of the socket, continuing in a lateral but never in an upward direction as in the boars.  In both sexes, the upper tusks are normally shorter than the lower counterparts (Fig. 1). 

Figure 1. Difference in appearance of upper and lower tusks in adult male and female feral hogs.

The permanent tusks of boars are significantly larger than those in sows.  In addition, the shapes of these teeth differ markedly between the two sexes.  Researchers attribute this difference to the male-male competition for breeding opportunities with females that is observed in this species.  These differences are so characteristic that these teeth can be used to accurately determine the sex of feral hogs that are over 14 months of age. 

Both boars and sows use their tusks for defense.  However, because of the size and structural differences, boars tend tend to slash and stab, while sows tend to bite, in their use of these teeth as weapons.  The sharpening of the lower tusks in both sexes is accomplished by the wearing or abrasion of these teeth against the upper tusks.  Some people believe that boars sharpen their tusks when they "tusk" or cut up trees.  In actuality, this tusking behavior is a form of scent marking by these animals using their tusk glands (Feral Hog Behavior) and has nothing to do with keeping a fine edge or point on the lower tusks.

The lower tusks in boars are generally semicircular in shape and triangular in cross section (Fig. 1).  That triangular cross-sectional shape is consistent from the base of the wear surface to the root tip.  The root tip stays open and the tooth remains evergrowing except in very old boars.  The overall length of the tooth (around the outside of the curve; Fig. 2) averages approximately 7 inches and typically varies in adults from 5 inches up to slightly more than 18 inches.  Anecdotal accounts exist of some tusks exceeding 20 inches.  These teeth grow at a rate of about 1/4 inch per month; however, most of this growth is lost through grinding wear against the upper tusk.  Similar to rodent incisors, the lack of sufficient grinding wear between the upper and lower tusks in feral boars can result in the lower teeth growing back into the animal’s mouth, and even into the mandible (Fig. 3).  This condition, however, is more common in domestic boars and wild barrows (i.e., castrated boars) than in uncastrated wild males.  Approximately 2/3 of the total lengths of the boar’s lower tusks are contained within the tooth’s socket in the lower jaw (Fig. 1).  The teeth are on average one inch by 1/2 inch in cross-section at the gumline in adult boars.  Enamel covers the forward-facing sides of the tooth, while the rear-facing surface is covered by cementum. 

Figure 2. Illustration of the measurement of the overall or total length of the lower tusk of an adult boar.

Figure 3. Examples of tusks in boars that exhibit increased growth due to lack of sufficient grinding wear between the upper and lower teeth.

The sow’s lowers tusks are also semicircular in shape and are roughly triangular in cross section, with the edges being more rounded than in the boars (Fig. 1).  Unlike the situation in boars, enamel only covers the crown of the lower tusks in sows, forming a distinct enamocementum junction line (similar to most mammalian teeth).  The sow’s lower tusk tapers from that junction line to the tips of both the crown and the root.  The root canal closes in sows at about 3-4 years of age, whereupon the tooth ceases any further linear growth.  The mean overall length of the lower tusks in sows is 2 7/8 inches and varies from 2 to 4 inches.  As in the boars, the roots comprise about 2/3 of the tooth’s length.  The cross-section of a sow’s lower tusk averages 1/2 by 1/3 inches. 

The upper tusks in boars approach a semicircular shape along the outer curve and are roughly trapezoidal in cross-section (Fig. 1).  As in the lower teeth, the root tip remains open and the tooth evergrowing, except in very old animals.  The cross-sectional shape tapers from the gumline to the tips of the crown and the root.  Enamel only occurs on the underside and in two narrow ridges along the lateral surfaces of the tooth.  Where it occurs, the enamel extends along the entire length of the tooth.  The overall length of the upper canine in boars averages 3 2/3 inches (range – 2 1/4 to 7 1/2 inches), and the cross-sectional dimensions at the gumline are about 1 inch by 1/2 inch.  Similar to the lower component, misalignment can cause longer lengths in the upper canines (Fig. 3). 

In sows, the upper tusks are barely semicircular in the lateral view and are somewhat triangular in cross section with rounded edges.  The tooth tapers from the enamocementum junction line to both the crown and root tips.  As in the lower counterpart, the enamel only covers the crown.  The root canals in these upper teeth also close, ceasing any further growth, at about 3-4 years of age.  These female upper tusks average 2 inches long (range – 1 3/8 to 2 3/4 inches) and are about 3/4 by 1/3 inches in cross section at the gumline.  

 

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.