White-tailed deer are often considered browsers because they consume woody vegetation. In reality, deer prefer forbs (weeds) more than browse but are compelled to consume woody species when herbaceous (non-woody) forage is unavailable or declines in quality. Although forbs are preferred, deer also will eat a broad variety of browse and grass species. Because of this adaptability, it is difficult to single out one habitat type that is greatly superior to others. Good deer habitat contains a diversity of woody plants (brush), forbs and grasses. A variety of food plants allow deer to select high quality forages throughout the year. The greatest forage supply for deer occurs in the early to intermediate stages of succession before the trees out-complete herbaceous plants for sunlight, water and minerals. This is the reason that brush management (appropriately conducted) tends to increase the availability of deer forage. Fire, herbicides, roller chopping, shredding, etc. temporarily “set back” succession and allow herbaceous forage plants to grow.
Cover is also a vital component of deer habitat. In South Texas, brush provides excellent cover for escape and for protection against weather extremes. An important aspect of this cover is its structure (height, density and canopy). Brush species with a moderate to dense canopy are important in South Texas as a source of shade. Escape or screening cover does not need to be extremely dense but should be at least 4 feet in height. Probably more important than the extent of the cover is the degree to which it is interspersed with feeding areas scattered throughout would be far more valuable to deer than habitat with a single large feeding area adjacent to a large tract of brush. This is rather simple but important principle should be considered by managers implementing brush management practices with wildlife as a priority.
The reason the interspersion of food and cover is so important to deer can be explained by the “edge effect”. Edge is the area where two or more vegetation types meet and integrate. The significance of edge is that this region often provides a greater diversity of food plants and cover types (escape, shade, etc.) to meet deer habitat requirements. Therefore, the most beneficial brush management patterns are those that create the most edge among treated and untreated areas. Brush management patterns that leave small blocks of brush in a checkerboard design (Fig.1) have been used effectively in several deer management programs. However, a strip pattern (Fig.2) of brush treatment is more common because long, thin strips provide more edge than block patterns, which follow contours of the land and certain vegetation or soil types, provide the greatest amount of edge and appear to be the most beneficial to deer. However, these treatments are more expensive and difficult to plan and accomplish.
Deer rarely travel across broad expanses of open area without access to cover. Therefore, a treated area should be no more than twice the distance a deer will move from cover. Research in South Texas has shown that deer will seldom venture more than 200 to 250 yards from cover, so treated strip widths should be no greater than 1/4 mile. It was observed that deer used treated strips more often during daylight hours when strips were only 200 to 250 yards wide.
Brush strips left for cover should be at least wide enough to allow a deer to disappear from visibility when an observer is standing at the edge of the cover strip. Brush density and height are unique to each ranch, but this threshold visibility distance ranges between 30 to 50 yards over much of South Texas. Note that this is the minimum amount of brush that should remain untreated to satisfy the screening requirement of the cover strip. It may be necessary to leave more untreated brush in order to maintain the diversity that is so essential to good deer habitat. This is particularly important with chronic impact treatments such as root-plowing or chaining that physically remove the treated brush plants.
The quantity of brush that can be removed will vary among ranches, depending upon brush characteristics. However, most successful deer management programs maintain 40 to 60 percent of the ranch brush. Remember that once brush is treated, its composition, structure and density are altered for a long period of time. Clearly define the objectives and consider all options before implementing a brush management program.