Habitat Requirements:
Seasonal Use of Forage Classes
Seasonal use of the major forage classes varied greatly (Figure 3). Forbs made up the bulk of the diet during the spring and summer, 66% and 81% respectively, while making up only 16% of the fall diets and 15% of the winter diets. The trend suggests a strong preference for forbs when they are available and actively growing.

Browse also made up a substantial portion of the deer diets in most seasons. Browse use was greatest in the fall, making up 69% of the diet (1/3 of which consisted of acorns). Browse made up 46% and 34% of the winter and spring diets, respectively, and dropped to 18% of the summer diet. Apparently deer used browse most during the fall transition period when forbs were becoming scarce or unpalatable, acorns were relatively abundant and available, and cool season grasses had not yet reached their peak winter availability. Browse use was lowest during the summer, which was the season of maximum forb availability.

Acorns were seasonally important, comprising 23% of the average fall diet and 8% of the winter diet. This was not surprising; acorns have been cited for their importance as deer foods throughout the scientific and popular literature. Acorns are rich in fat and high in carbohydrates, which allow deer to build the needed fat reserves for late fall and winter months. Some studies have indicated that acorns comprise close to 80% of a deer’s diet during times of acorn abundance. The relatively low dietary percentages for deer on the NFWU (23% and 8% versus 80%) are probably due to reduced acorn abundance, rather than a preference for alternative forages. Neither of the 2 study years were "good acorn years" on the NFWU.

Grasses and grasslikes received very little use (no more than 1%) by deer during spring and summer. This forage class became increasingly important in the fall and winter diets, presumably as forb availability decreased and annual cool season grasses such as bromes, wheat, and rye emerged and perennial cool season grasses like tall fescue and dichantheliums remained in a green vegetative state. This category made up 11% of the average fall diet and a major portion, 39%, of the winter diet.

Except during fall, the "others" category was an insignificant contributor to deer diets (no more than 1%). During fall, mushrooms comprised slightly over 4% of the diet.

A generalized summary of forage class use by deer in the Cross Timbers is as follows. Deer seemed to select forbs when they were available, abundant, and actively growing, which is usually spring and summer. Browse was a very important dietary component throughout the year, and comprised the majority of the diet in fall. Acorns comprised a large portion of browse consumed in fall and winter, and their use seemed to be limited primarily by their availability. Grasses became increasingly important in the fall as forbs became scarce, and were even more important in winter when they comprised over 1/3 of the average diet. Most of the grass consumption was attributed to a relatively few cool season species. Mushrooms, while not appearing significant in the overall scheme of things, did make up a significant portion of the fall diets. Their importance might be magnified during years of low acorn availability.