Composition and Squirrel Use of Acorns of Black and White Oak Groups

Abstract

Of 11 species of oak (Quercus sp.) acorns tested, those of the white oak group were higher in nitrogen-free extract, cell wall contents, and hemicellulose than those of the black oak group, which had higher levels of dry matter and crude fat. Acorns of all 11 oak species were low in protein and phospho- rus. In feeding tests with adult fox squirrels (Sciurus niger), negative nitrogen balances were recorded for about two-thirds of the trials. Acorns of the white oak group were consumed at higher rates and thus appeared to be the more palatable of the two groups. Acorns apparently supply squirrels with ade- quate energy but do not satisfy their metabolic requirements for nitrogen or probably phosphorus. J. WILDL. MANAGE. 40(3):479-483 Oak mast is an important source of food for many wildlife species (Martin et al. 1951). Tree squirrels (Sciurus sp.) are es- pecially dependent on the presence of qual- ity acorns in their habitat, and squirrel num- bers have been reported to vary directly with acorn availability (Sharp 1960). Al- though the maintenance of huntable popu- lations of squirrels and the well-being of several other wildlife species necessitate the establishment and management of oaks in forest ecosystems, few studies have deter- mined the metabolic usefulness of acorns to squirrels. Fox squirrels have been reported to use white (Quercus alba) and black (Q. velutina) oak acorns more efficiently than those of red oak (Q. borealis maxima) and to digest lipids and nitrogen free extract more readily than crude protein and crude fiber (Baumgras 1944). Acorns with high lipid contents reportedly serve as high en- ergy rations for squirrels (Smith and Foll- mer 1972). The present paper reports both the composition of acorns of 11 species of oaks and the use of these acorns by fox squirrels. MATERIALS AND METHODS Acorns from the black and white oak groups were collected in autumn 1971 for feeding trials. Black oak group acorns were black and northern red oaks (Q. rubra), both collected in the Sylamore Experi- mental Forest in Arkansas, and water oak (Q. nigra), willow oak (Q. phellos), blue- jack oak (Q. incana), and southern red oak (Q. falcata), all collected in Nacogdoches County, Texas. White oak group acorns in- cluded white oak, swamp chestnut oak (Q. prinus), live oak (Q. virginiana), and post oak (Q. stellata), all collected in Nacogdo- ches County. Acorns from the sawtooth oak (Q. acutissima), also a member of the white oak group, were donated by the Interna- tional Paper Company, Camden, Arkansas. Acorns were selected for soundness and stored at -12 C until fed to squirrels. At the beginning of each feeding trial an ali- quot of whole acorns was dried in a forced- air oven at 40 C to determine the oven-dry weight of consumed acorns. The oven-dried acorns were ground in a Wiley mill and stored in capped glass bottles. The dried material was used for the determination of crude protein, crude fat, crude fiber, ash, Ca, and P, according to standard AOAC procedures (Horwitz 1965); cell wall con- tents (CWC), acid detergent fiber (ADF), acid detergent lignin (ADL), and silica were determined according to the proce-