Seasonal variation of metabolism and thyroid activity in the Mexican ground squirrel Citellus mexicanus
Barnes, Martha Lee
Hudson, Jack W.
Master of Arts
Metabolic measurements in thermal neutrality for the Mexican ground squirrel, Citellus mexicanus, in-dicated a mean summer metabolism of 1.10± .08 cc 02/gm/hr and a mean winter metabolism of .56±.08 cc 02/gm/hr. Animals were observed to be torpid during the winter with their body temperatures approaching that of the ambient. Thyroid activity as determined by release of radioiodine from the gland did not show the thyroid of Citellus mexicanus to be activated by cold during the summer or winter. Histological studies did not detect cold activation of the gland.