Hj. Harlow, FASTING BIOCHEMISTRY OF REPRESENTATIVE SPONTANEOUS AND FACULTATIVE HIBERNATORS - THE WHITE-TAILED PRAIRIE DOG AND THE BLACK-TAILED PRAIRIE DOG, Physiological zoology, 68(5), 1995, pp. 915-934
The white-tailed prairie dog is a spontaneous hibernator that enters a
rt anorexic state followed by torpor in early fall. The black-tailed p
rairie dog is a facultative hibernator that enters torpor only when de
prived of food and water in the winter. The physiological state of hib
ernation is similar to a Phase II euthermic fast characterized by elev
ated fat catabolism, increased blood ketone bodies, and conservation o
f protein tissues. It was hypothesized that these spontaneous and facu
ltative hibernators use fat and protein differently during a fast prio
r to the hibernation season. Weekly blood and urine samples were taken
from both species during a 5-wk period of food and water deprivation.
The black-tailed prairie dog lost mass at a greater rate and had a la
rger daily urine volume and urea, ammonia, and potassium excretion, as
well as a higher plasma urea/creatinine ratio, all of which define a
greater rare of protein catabolism for this species than for the white
-tailed prairie dog. The black-tailed prairie dog, therefore, does not
conserve protein to the same extent as the white-tailed prairie dog d
uring a Phase II fast typical of hibernation starvation. Ketone bodies
do not appear to regulate protein catabolism directly. But the greate
r protein catabolism by the black-tailed prairie dog may be related to
pH and water balance requirements that are circumvented in the white-
tailed prairie dog by engaging in spontaneous torpor. Both species evo
lved from populations of ancestral prairie clogs that have retained th
e ability to hibernate spontaneously. It is hypothesized that the blac
k-tailed prairie dogs may not have maintained the capacity for a deep
Phase II, protein-conserving state typical of hibernation starvation b
ut keep an active profile throughout winter, relying to a greater exte
nt on protein catabolism in response to selective pressures of greater
predation, higher food abundance, and perhaps a need to preserve fat
stores for reproduction.