Al. Chungmaccoubrey et al., EFFECTS OF TANNINS ON DIGESTION AND DETOXIFICATION ACTIVITY IN GRAY SQUIRRELS (SCIURUS-CAROLINENSIS), Physiological zoology, 70(3), 1997, pp. 270-277
Acorn tannins may affect food preferences and foraging strategies of s
quirrels through effects on acorn palatability and digestibility and s
quirrel physiology. Captive eastern gray squirrels (Sciurus carolinens
is) were fed 100% red oak (Quercus rubra) or white oak (Quercus alba)
acorn diets to determine effects on Intake, digestion, and detoxificat
ion activity. Red oak acorns had higher phenol and tannin levels, whic
h may explain the lower dry matter intakes and apparent protein digest
ibilities and the higher glucuronidation activities observed in squirr
els. Although the white oak acorn diet had lower apparent protein dige
stibilities than the reference diet, it did not suppress dry matter in
take for a prolonged period or stimulate glucaronidation. Negative phy
siological effects of a 100% red oak acorn diet suggest gray squirrels
may require other foods to dilute tannin intake and provide additiona
l nutrients. To distinguish the roles of different tannin types in the
observed effects of acorn diets on squirrels, squirrels were fed rat
chow containing no tannins, 4% or 8% tannic acid (hydrolyzable tannin)
, or 3% or 6% quebracho (condensed tannin). Apparent protein digestibi
lities were reduced by tannic acid and quebracho diets, Only the 8% ta
nnic acid diet tended to Increase glucuronidation. Specific effects of
tannins may largely depend on tannin type, composition, and source an
d on other nutritional and physiological factors.