Research Training Program

Smithsonian Institution
National Museum of Natural History

PROJECT SUMMARY
1996

Jorge Uribe-Juarez
Universidad Nacional Autonoma de Mexico
Mexico City, Mexico
Alfred Gardner, Ph. D
Supervising Scientist
Department of Vertebrate Zoology
Division of Mammals


"The Research Training Program at the National Museum of Natural History gave me the opportunity to work with one of the best and amazing collections I have ever seen under the advice of a scientist I only knew by publications and who guided me in the study and research of a particular group of mammals: the rodents."

Growth dynamics in rodent incisors

ABSTRACT
Upper and lower incisors of more than 300 different genera of rodents represented in the Division of Mammals Collection were examined to determine the presence or absence of striae as an incisor growth rate indicator. Measurements revealed big differences in growth rate between taxa. Castor canadensis has the highest growth rate (168 mm/year) both in upper and lower incisor, while the lowest rate found was 24.3 mm/year for Steatomys pratensis (upper incisor), and 17.03 mm/year in the lower incisor of Chinchilla lanigera. Eight genera did not show evidence of striae. Incisors were examined and measured in two different species, Peromyscus maniculatus and Marmota caligata, and factors controlling the rate of growth were examined. The results showed differences in growth rate for both, probably influenced by seasonal factors like length of day in different periods of the year, and the fact that Marmota caligata is a hibernator. A conclusion from this investigation shows that rodents exhibit a variety of growth according to taxon, and several factors like latitude, elevation, day length and hibernation, seem to influence the incisors growth. To explain the growth rate of the incisors of rodents, further studies are needed. A detailed examination of all these factors, associated with habits and ecological data, will provide more information trying to explain this interesting topic.

This research was supported by a grant from the Smithsonian Women's Committee.

Letter of Gratitude