Catalog Number:
67330 -SKIN
Object/Specimen Description:

Skin

Specimen Count:
1
Locality:
US Mid Atlantic (PA, NJ, MD, DE, DC, VA, WV)
Sex:
Female
Collecting Locality:
North America, United States, District of Columbia
Cabinet:
17
Drawer/Shelf:
01
Upper Level Taxonomy:
Animalia, Chordata, Vertebrata, Tetrapoda, Mammalia, Eutheria, Rodentia, Myomorpha, Muridae, Murinae

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.

Thanks to their ability to produce milk, female mammals are able to feed their offspring for weeks, months, or even years after they are born. This sets the stage for the extended childhoods of many mammal offspring. With food and shelter taken care of (by the mother in most species), a remarkable amount of learning occurs for mammal offspring before they become independent. Elephants tend to their young for as long as 10 years, and humans for longer still. Young mammals may learn about food, shelter, migration routes, social structures, or other keys to survival from their parents. While extended childhoods support learning, they are costly, especially for the female. Lactating females must consume enough calories to feed their offspring and maintain themselves. Offspring that stay around after weaning from their mother's milk may still require protection and food. Human offspring are the most extreme case of investment, with parents usually providing intensive support until age 18 and continuing support beyond.