Columbian Ground Squirrel

Associated Smithsonian Expert: Darrin P. Lunde, M.A.

Darrin Lunde on an expedition to the Bandalla Hills of South Sudan in the summer of 2013

Courtesy of Oliver Bench

Darrin Lunde is Collections Manager in the Division of Mammals at the Smithsonian National Museum of Natural History. The Mammal Collection is the largest collection of its kind in the world. Darrin started his career by building his own natural history museum when he was just ten years old, and by the time he went to college, he had mastered specimen preservation. After graduating from Cornell University, Darrin was hired by the American Museum of Natural History in New York City, where he stayed for twenty years joining field expeditions to the remote corners of South America, Africa, and Southeast Asia. He has discovered dozens of new species and shed light on hundreds of other lesser known mammals. Darrin earned a Master of Arts from the City University of New York and much of his interest in museums stems from having grown up in "nature deprived" New York City. To Darrin, museum collections are an important link to nature, and he is driven by the thought that in another century museums may be our only connection to the wild animals we take for granted today. At the Smithsonian, Darrin continues a program of active field work with his goal being to illuminate the rich diversity of mammals with which we still share the world.

Meet our associated expert

This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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This golden-mantled ground squirrel (Spermophilus lateralis) is in a typical rodent position, gnawing on some food
Courtesy of Franco Folini, Wikimedia Commons, CC-BY-SA


About Rodents (Order Rodentia): Feeding

Rodents are famous for their teeth. The large, paired cutting teeth (incisors) in the front of their mouth give them a buck-toothed appearance. The incisors are self-sharpening, thanks to the way they grind together during gnawing. While a strong enamel coating prevents wear on the front, the back of each incisor is soft and wears down. The outcome is a chisel-like shape that can cut into wood, food, or predators. The incisors grow continuously, creating tooth material for sharpening throughout the life of a rodent. A rodent skull is shaped to support the muscles used in gnawing, such as an enlarged region (the pterygoid) that anchors the lower jaw muscles. A skull modification allows the lower jaw to move not only up and down, but back and forth for better grinding action. Rodents are the largest group of mammals on Earth, and their ability to gnaw is part of the reason they have been so successful.

This mountain Noctule (Nyctalus plancyi) has specialized, sharp teeth for grasping prey
Courtesy of The Darwin Initiative Centre for Bat Research, via EOL China Regional Center, CC-BY-NC-SA


About Mammals (Class Mammalia): Feeding

Mammals have a unique arrangement of a lower jaw directly hinged to the skull. The upper jaw is fixed, while the lower jaw is movable. A powerful bite results which, coupled with specialized teeth, allows mammals to eat a diversity of foods. Straight-edged incisor teeth at the front of the jaw are for cutting and gnawing. Pointed, canine teeth on the sides can grab and tear meat. Flat, broad molars are used to grind or crush plants or shelled animals. Mammals tend to have more than one type of tooth (heterodont dentition), with the mix depending on diet. Meat-eaters have sharp incisors and canines plus slicing molars; mammals who eat tough plants have duller incisors and canines, but large, ridged molars. All types of mammal teeth are replaced once or never during a mammal's lifetime. A coating of enamel, the hardest material found in a mammal's body, makes teeth built to last.