Gophers and Moles: Two Mammals DIfferently Adapted for Life Underground

Gophers and Moles

By Renn Tumlison, tumlison@hsu.edu

Gophers and moles both are fossorial animals - meaning that their lives are spent mostly tunneling through the softer soils of the earth. However, these are very different mammals. The mole belongs to the order Insectivora because it eats invertebrates, but the gopher actually is a kind of rodent with the typical gnawing front teeth called incisors. Its foods include roots, tubers, and other parts of plants.

Gophers Dig for Plants

The species of gopher found throughout most of Arkansas is the Baird’s pocket gopher (Geomys breviceps). The term Geomys means “earth mouse.” Most of their lives are spent underground so gophers are seldom seen, but their presence is obvious when the excavated dirt from a burrow is deposited in a mound at the surface. After moving soil from their tunnels to the surface, gophers like to isolate their tunnel systems with plugs of dirt.

Gopher holes
Gopher Feet

Gophers have several special adaptations that help them work in a subterranean environment. The legs are short to allow movement in a tunnel, and the front feet have three especially large claws used for digging. Not all of the digging is done by use of the feet, however.

The gnawing incisors often are used to break up the more compact dirt in front of them.  That process could place a lot of dirt in the mouth, but another specialization solves that problem.  The incisor teeth grow through the lips so that the mouth actually closes behind these teeth instead of in front of them.  That way, the teeth can be used to dig without dirt getting into the mouth.

Gopher Mouth
Gopher Head

Dirt doesn’t get into the ears because they are short and have valves that close to exclude loose soil. Also, the eyes are small so not likely to be bothered by dirt. The tail has short hairs but is very sensitive to help guide the gopher when it moves in a dark tunnel. 

Burrows are dug usually about 15-25 cm (6-10 inches) underground and may be several hundred meters long. Side branches from the main tunnel may lead to the surface, to feeding sites, to defecation sites (their version of a separate “restroom”), and to food storage chambers. Gophers gather food when it is available and store it for later consumption. Built-in “grocery bags” are used to carry the food gathered during foraging. Those bags are fur-lined cheek pouches located on each side of the head. The pockets are the reason for the common name “pocket gopher.” A cheek pouch is seen as a dark slit on the side of the head in the photo.

Gopher  Pockets

Moles

Mole Run

Moles get little respect from people who try to maintain a perfectly landscaped yard because they create surface runs that are seen as ridges of earth lifted along the path dug by the mammal. (A portion of a mole run is shown in the photo at left.) Although many people fear that the mole will eat their garden plants, the primary foods are invertebrates such as earthworms and insects that are sought while digging the surface tunnels. Gardening enthusiasts may not like moles in their yards, but actually their work opens and mixes soil in the natural environment.

In the preferred moist and pliable soil, a mole can dig a surface tunnel at rates up to 6 m (about 20 feet) per hour. The ability to dig requires several adaptations. The front legs are short and powerful, and the front feet are shovel-like with claws that are long and broad. The palm faces out, so the motion of a digging mole looks something like a swimming stroke. 

Mole Forelimb
Mole Head Side

Mole Head Side 

Sometimes obstructions are too large to dig around, so the mole must back up in its burrow. The hairs that cover its body are adapted for the occasion. Hairs on most mammals are shafts that point backward – so forward motion causes no problems – but the hairs stand against any obstruction to backward motion. The hair of moles, in contrast, is built with several bends, or strictures, that make the hair act like a spring. Only the top of the shaft, called the shield, is wide. If a mole moves forward the shield points backward, but if the mole has to back up the spring-like nature of the hair lets the fur compress for a moment as the shield reverses direction (microscopic view, photo).

This makes it easier for the mole to back up while in a tunnel. It also helps keep dirt from falling between the hairs. The resulting texture of the fur is velvety, and so soft that a kind of bandage for delicate wounds is called “mole skin.”

Mole Hair
 
 
 
 
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