United States

Department of

Agriculture

Forest Service

Southern Forest

Experiment Station

New Orleans,

Louisiana

Research Paper

SO-289

September 1995

Effects of Prescribed Burning and Cattle

Grazing on Deer Diets in Louisiana

Ronald E. Thill, Alton Martin, Jr., Hershel F. Morris, Jr.,

and Austin T. Harrel
S-Y

A study was conducted on the dietary and nutritional effects of

cattle grazing and rotational prescribed burning on the diets of

three to five captive white-tailed deer (Odocoileus virginianus)

on longleaf pine (Pinuspalustris Mill.)_bluestem (Andropogon spp.

and Schizachyrium spp.) sites in central Louisiana from October

1980 through February 1987. Deer diets were evaluated under

ungrazed, moderate year-long, heavy seasonal, and heavy yearlong cattle grazing treatments. Deer diets were composed mostly

of browse and forbs under all grazing treatments, but were less

diverse under heavy grazing when compared with moderate and

no grazing treatments. Foraging efficiency (computed as the ratio of forage intake per 30-minute trial to the distance traveled)

was comparable among treatments during spring and fall but was

lower under the heavy grazing treatment during summer and

winter. Diets selected under ungrazed conditions contained the

highest percentage of uncommon and ephemeral plant taxa during all seasons except fall. Dietary crude protein (CP), phosphorus (P), and calcium-to-phosphorus ratios varied significantly

under various grazing treatments for certain seasons. Prescribed

burning did not significantly affect diet diversity; however, diets

from areas of first-year burns were higher in CP and P than from

areas of older burns during spring and summer, but these differences disappeared by the first fall after burning. From a nutritional

standpoint, burning and seasonal influences generally had more

impact than grazing treatments on deer diets. No evidence was found

that seasonal or yearlong cattle grazing at moderate levels (40- to

50-percent herbage removal) adversely affected deer nutrition.

ACKNOWLEDGMENTS

Thanks are extended to W.R. Thacker and R.D. Her-rick for many

hours of dedicated field assistance and to J.G. Kie, H.S. Crawford,

and H.A. Pearson for reviewing earlier drafts of the manuscript.
Effects of Prescribed Burning and Cattle Grazing

on Deer Diets in Louisiana

Ronald E. Thill, Alton Martin, Jr., Hershel F. Morris, Jr., and Austin T. Harrel

INTRODUCTION

This study was initiated to evaluate the effects of

cattle grazing and associated prescribed burning on

white-tailed deer (Odocoileus virginianus) diets and

nutrition within the longleaf pine (Pinus palustris

Mill.)-bluestem (Andropogon spp. and Schizachyrium

spp.) range type of the Southeastern United States.

Bluestem grasses dominate the herbaceous understory

on about 2 million ha in southern Louisiana, Mississippi, and Alabama and northwestern Florida. Cattle

grazing has been a controversial issue throughout this

region for many years (Thill 1985).

Although often abundant, southern deer forage on

these sites is typically low in nutritional value. Deer

diets are phosphorous (P) deficient all year (Blair and

others 1977) and adequate in crude protein (CP) for

optimum growth only during spring (Short 1969). Consequently, southern upland deer herds are considered

to be limited more by forage quality than by quantity

(Lay 1957).

Prescribed burning is used extensively throughout

southern Coastal Plain forests for preparation of pine

seedbeds, fuel reduction, wildlife habitat enhancement, forage quality improvement, and rotating livestock distribution. Winter burning on a 3-year rotation

is generally advocated for livestock forage management (Duvall and Whitaker 1964) and fuel reduction

(Sackett 1975). Burned sites attract deer and cattle,

and diets derived from recently burned sites are temporarily higher in quality than on older burned or

unburned sites (Lay 1967, Stransky and Harlow 1981,

Thill and others 1987). Nevertheless, the availability of

deer forage may be sufficiently reduced by concentrated

cattle use of recently burned sites, and this may affect

the botanical and nutritional composition of deer diets.

The objective of this study was to evaluate the effects of prescribed burning and several grazing treatments on deer diets relative to botanical and nutritional

composition, foraging efficiency, and diet selectivity.

STUDY AREAS AND METHODS

The study was conducted from October 1980 through

February 1987 on adjacent east and west pastures of

what was known historically as the headquarters pasture of the Palustris Experimental Forest in central

Louisiana. Both the east and west pastures were divided by firelines into three subunits for burning purposes (each about 18 ha) that served as separate

sampling areas. One subunit per pasture per year was

burned in late February on a 3-year rotation. Prior to

this study, both pastures had been burned at about 3-

to &year intervals since 1959.

The study was conducted in two phases of 3 years

each. In phase 1, deer and cattle diets were studied in

the east pasture under moderate yearlong grazing

(MY); only deer diets were studied in the adjacent

ungrazed (UG) west pasture (table 1) (Thilll982, Thill

and Martin 1986). Phase 1 nutritional aspects have

already been reported by Thill and others (1987). In

phase 2, cattle stocking on the MY pasture was doubled

to obtain heavy yearlong grazing (HY), and the UG

pasture was subjected to heavy seasonal grazing (HS)

from mid-April through October. Deer and cattle dietary overlap for phase 2 was summarized by Thill

and Martin (1989). In this report, the effects of burning and heavy yearlong and heavy seasonal cattle grazing on deer nutrition and foraging behavior are

summarized and compared with the results of phase 1

data.

The 30-year-old pine overstory of both pastures had

been thinned in 1976, and in 1984 averaged 15.2 m2/ha

of longleaf pine and 1.1 m2/ha of hardwood basal area.

Current-year browse production averaged >400 kg/ha

on both pastures during phase 1 (Thill and Martin

1989) and was estimated at or slightly above this level

during phase 2. Herbage production and use varied

with years since last burn (table 1). For additional

study area and treatment details, see Thill(l982) and

Thill and Martin (1986, 1989).

Ronald E. Thill is a supervisory research wildlife biologist, U.S. Department of Agriculture, Forest Service, Southern Forest Experiment

Station, Nacogdoches, TX 75962; Alton Martin, Jr., is a range technician, U.S. Department ofAgriculture, Forest Service, Southern Forest

Experiment Station, Pineville, LA 71360; Hershel F. Morris, Jr. and Austin T. Harrel are department head and associate professor, respectively, Feed and Fertilizer Laboratory, Louisiana State University, Baton Rouge, LA 70803-2003.

1
Table l.- Overstory basal area, cattle stocking, and herbage standing crop and use by study phase, grazing treatment, and year after

burning for central Louisiana study areas

Study phase* Pasture

1 East

Treatment+

MY

Basal area* Herbageq

Cattle Year after

Pines Hardwoods stocking* burning Standing crop Use

_ _ _ _ _ _ _ _ m2/ha ________ AU/ma. kg/ha Percent

13.4 1.3 1.8 1st 1,098 46

2nd 567 29

3rd 847 26

West UG 13.5 1.0 0.0 1st 1,036 **

2nd 1,084

3rd 965

2 East HY 14.6 1.4 3.8 1st 1,135 67

2nd 770 52

3rd 884 50

West HS 15.8 0.8 3.4 1st 1,260 77

2nd 1,025 58

3rd 983 61

*Inclusive sampling dates: phase 1 = Oct. 1980 to Aug. 1983; phase 2 = Apr. 1984 to Feb. 1987.

+UG = ungrazed, MY = moderate yearlong grazing, HS = heavy seasonal (15 Apr. to 1 Nov.) grazing, and HY = heavy yearlong grazing.

*Mean overstory basal area of pines and hardwoods across subunits in 1981 (phase 1) and 1984 (phase 2).

OMean cattle stocking (animal units [AU] per month) over the entire grazing season (i.e., yearlong for all but the heavy seasonal grazing

treatment).

YMeasured in October following the procedures of Thill(1982).

**Herbage use was not measured because cattle were excluded from this pasture.

Data on deer food habits were obtained by direct

observation of leashed, tame deer during four sampling periods: spring (21 March to 10 June), summer

(23 June to 13 September), fall (22 September to 25

November), and winter (5 January to 4 March). Methods employed during both phases of the study were

identical except for minor differences in starting and

ending dates of seasonal trials. Four to five feeding

trials (each involving three to five deer) were conducted

on each subunit at about equal time intervals throughout each season. Trials were begun at random starting points and were conducted between 0730 and 1500

hours. Distances walked by each animal during the

30- to 45minute trials were estimated to the nearest

0.1 km on a pedometer worn by the observer. As most

trials were conducted for 30 minutes, all distances

traveled for shorter or longer trials were adjusted to a

30-minute basis as follows:

Estimated travel distance per 30 minutes =

(actual distance traveled) (30) /actual trial duration.

Two deer (a doe and a castrate) used throughout

the 6-year study were 3.5 years old at study initiation

(October 1980). A 2.5-year-old doe was also used

throughout phase 1. Two additional does (8 months

old) were added during 1981 winter trials; one of these

was used throughout the remainder of the study and

the other was used only during the remainder of phase

1. Thus, three to five deer were used during most of

phase 1, and three deer were used throughout phase

2. Deer were maintained between trials on commercial horse and mule feed (13 percent CP, 0.44 percent

P, and 0.48 percent calcium [Cal) and a variety of native plants. Feed was removed the evening before each

trial to assure sufficient foraging.

As each deer foraged, simulated diet samples were

handplucked that mimicked the deer’s foraging in species composition, plant parts, phenology, and forage

weight. Simulated diet samples were dried to a constant weight at 50X!, weighed, and ground through a

l-mm screen. Weights were used as estimates of forage intake. The ratio of forage intake to the distance

traveled per 30 minutes was used as an index of for2
aging efficiency. A composite forage sample was prepared for each subunit and date by mixing 15 g of the

diet sample for each deer observed. Composite samples

were analyzed for CP, Ca, and P (Association of Offrcial Analytical Chemists 1984) and for cell wall constituents (CWC), acid detergent fiber (ADF), and acid

detergent lignin (ADL) (Goering and Van Soest 1970).

Forage intake per 30 minutes was multiplied by CP

and P percentages to derive estimates of CP and P

intake. Nutritional analyses were conducted by the

Louisiana State University Feed and Fertilizer Laboratory, and results were expressed on a dry matter

basis.

Diets were quantified using bite-count procedures

(Thill 1984). Bite-count data from all animals were

cornposited across dates for each subunit to derive diet

composition values for each season. Data presented

on diet diversity are based on these cornposited data,

not on the individual diets from each foraging trial.

We evaluated the effects of burning and grazing on

diet selectivity by calculating the percentage of the

diet composed of uncommon and/or ephemeral species

(Hobbs and others 1983). Uncommon species were defined as those having a frequency of occurrence in the

fall averaging <l percent over 162 permanent 0.89-

m2 quadrats per subunit. As a measure of the contribution of ephemeral or uncommon foods to the diet,

high values suggest greater selectivity.

Nutritional data were analyzed in a three-factor

(four seasons, four grazing treatments, and three burn

ages) complete block analysis of variance (ANOVA)

with blocking over years (3 years per phase for all

parameters except selectivity with 2 years) using

BMDP statistical software (Dixon and others 1985).

The following two-way interactions were considered:

grazing by season, grazing by year, burn by season,

and grazing by burn. Within-pasture (phase 1 versus

phase 2) differences in forage-class use were tested

with a similar ANOVA. Differences among means were

tested using Tukey’s multiple range test (Steel and

Torrie 1960). All tests were at the 0.05 alpha level.

Because treatments were not replicated, inferential

statistics were used only to interpret the data; it is

acknowledged that treatment and site effects were

confounded (Hurlbert 1984). However, because both

of these adjacent pastures have historically received

similar burning and forest management treatments

and have predominantly similar soils (primarily

Ruston fine sandy loam and Smithdale sandy loam),

the authors feel that observed differences are due to

treatment effects rather than site differences.

Findings for phases 1 and 2 are based on 706 and

497 hours of deer observations and a total of 303,773

and 130,225 bite-counts, respectively. Observation

time was distributed equally among subunits within

each season. For our purposes, ferns were grouped

with forbs, and browse included leaves and tender

twigs of trees, shrubs, and vines. Graminoids refer

collectively to grasses and grasslike plants.

RESULTS

Forage-Class Use

Deer diets were dominated by browse and forbs

throughout both phases of this study (tables 2 through

4) (Thill and Martin 1986, 1989). Browse comprised

250 percent of the yearlong diet except for the most

recent burns during spring under UG and MY grazing. Within-pasture (phase 1 versus phase 2) comparisons of forage-class use indicated that grazing

treatments did not significantly affect browse use on

either pasture (tables 2 and 3), except for year 3 when

browse use increased under HY grazing compared with

MY grazing (table 3). Fruit use was significantly

greater under UG and MY treatments than under the

HS and HY grazing of phase 2 (tables 2 and 3).

Graminoid use declined significantly on the MY-HY

pasture from phase 1 to phase 2 (table 3), but declined

only during year 1 on the UG-HS pasture (table 2).

Forb use was comparable under UG and HS grazing

(table 2); however, HY grazing was accompanied by

significantly greater second-year forb use, but lower

third-year forb use relative to MY grazing (table 3).

Burning did not significantly affect graminoid or

fungi use by deer in either pasture or browse use in

the UG-HS pasture (table 4). Browse and forb use on

the MY-HY pasture varied with the year of the study

as well as years since burning, but forb use was generally highest the first year after burning in both pastures. Fruit availability and use were reduced

throughout the first year after burning relative to the

second and third year after burning (table 4).

Diet Diversity

Prescribed burning did not affect diet diversity (i.e.,

the number of plant taxa eaten by deer) in either the

UG-HS (P = 0.603) or MY-HY ((P = 0.372) pasture.

Diet diversity was affected by grazing intensity

(P <O.OOOl) and season (P <O.OOOl) in both pastures

and by the study year (P = 0.0005) in the UG-HS pasture; none of the interaction terms were significant (P

>0.357). Within pastures, diet diversity decreased significantly with increased cattle use during phase 2

(fig. 1). Diet diversity followed consistent seasonal

trends for all four grazing treatments, declining from

highest levels during spring to lowest levels during

winter (fig. 1). Deer selected less diverse diets at the

end than at the beginning of this study (fig. 2); furthermore, diet diversity declined even during phase 1

on the UG pasture, suggesting that deer use alone may

have affected the availability of preferred, uncommon

plant species on these relatively small sampling areas.

3
Table 2.- White-tailed deer forage class use under ungrazed conditions (198M3) and heavy seasonal grazing (198447) of a pinedluestem range in central Louisiana*

Forage Year of

class study

Ungrazed Heavy seasonal

Z SE f SE Pt

Browse 64.3 a 2.4 69.4 a 2.1 0.191

Fruits 6.9 a 1.4 3.5 b 0.7 0.018

Graminoids 1st 5.3 a 1.3 2.1 b 0.5 0.027

2nd 2.3 a 0.5 3.2 a 1.0

3rd 3.6 a 1.2 1.5 a 0.9

Forbs 23.8 a 2.5 21.7 a 2.0 0.433

Fungi 1.2 a 0.2 3.2 b 0.9 0.014

*Values are grazing main-effect means (n = 34 to 36) and grazing-by-year interaction means

(n = 11 to 12). Means within rows followed by unlike letters are significantly (P ~0.05) different.

?F-value probabilities for grazing main effects. The probability listed for graminoids is for the

grazing-by-year interaction term.

Table 3.- White-tailed deer forage class use under moderate yearlong (1980-83) and heauyyearlong (1984-87) cattle grazing of a pinedluestem range in central Louisiana*

Forage

class

Year of

study

Moderate yearlong

x SE

Heavy yearlong

x SE

Browse

Fruits

Graminoids

Forbs

Fungi

1st

2nd

3rd

1st

2nd

3rd

63.3 a

60.2 a

52.4 a

5.3 a

7.5 a

22.5 a

26.1 a

32.7 a

1.5 a

3.1 64.6 a 3.5 0.003

2.9 54.8 a 4.1

5.0 68.4 b 3.0

0.9 2.3 b 0.4 <O.OOl

1.4 2.3 b 0.4 -Co.001

3.4 25.4 a 4.0 <O.OOl

4.5 38.0 b 4.2

4.1 25.3 b 3.2

0.3 3.2 b 0.9 0.011

*Values are grazing main-effect means (n = 34 to 36) and grazing-by-year interaction means

(n = 11 to 12). Means within rows followed by unlike letters are significantly (P~0.05) different.

tF-value probabilities for grazing main effects. The values listed for browse and forbs are for

the grazing-by-year interaction term.

Grazing Effects by Season

Grazing effects varied by season for all nutritional

and foraging variables evaluated (P 50.006); the most

apparent differences were for CP, P, and Ca:P ratios

(figs. 3 through 5). Except for forage selectivity, ADL,

ADF, and CWC (figs. 4 and 51, nutritional and foraging variables were not significantly affected by grazing treatments during spring, nor were CP, CP intake,

P, P intake, ADL, or CWC affected during summer.

Although forage selected during fall and winter was

generally significantly higher in CP and P under the

heavier grazing of phase 2, reduced forage intake due

to grazing-induced reductions in forage availability

largely negated this grazing benefit (fig. 3).

Forage Ca levels were generally lowest during

spring and highest during summer (fig. 3). During the

entire year, Ca:P ratios exceeded the 2:l to 1:2 ratios

often recommended for domestic ruminants (Maynard

and Loosli 1969).

Except for spring UG-HS pasture data, heavier

cattle grazing reduced deer forage intake, but differences were significant only during winter (both pastures) and on the UG-HS pasture during summer (fig.

4). Intake under each grazing treatment was generally highest during spring and consistently lowest

during winter. Deer traveled comparable distances per

30 minutes under all grazing treatments during spring

and fall, but traveled significantly farther during summer and winter under HY than under MY grazing (fig.

4
Table 4.- Prescribed burning effects on within-pasture forage class use by white-tailed deer on a pine-bluestem range in central Louisiana*

Year af;eer burn

1st year 2nd year 3rd year

Forage Year of

Pasture+ class study x SE z SE x SE P*

West

(UG-HS) Browse 66.5 a 2.9 65.2 a 2.8 70.0 a 2.5 0.386

Fruits 2.2 a 0.7 8.0 b 1.7 5.3 b 1.0 <O.OOl

Graminoids 3.0 a 0.8 2.7 a 0.5 3.3 a 0.9 0.331

Forbs 25.7 a 3.0 22.1 ab 2.5 19.3 b 2.2 0.014

Fungi 2.7 a 0.8 1.9 a 0.9 2.1 a 0.9 0.755

East

(MY-HY) Browse 1st 61.1 a 5.3 67.7 a 3.9 63.1 a 2.6 0.002

2nd 50.3 a 4.3 57.1 ab 4.4 65.1 b 3.1

3rd 62.6 a 4.5 47.6 b 6.2 71.0 a 2.8

Fruits 1.4 a 0.5 5.3 b 1.1 4.6 b 0.9 <O.OOl

Graminoids 3.5 a 1.0 5.9 a 1.9 5.3 a 1.0 0.369

Forbs 1st 31.5 a 6.0 18.3 b 2.8 22.1 b 2.8 <O.OOl

2nd 42.7 a 6.0 31.2 b 4.9 22.3 b 3.5

3rd 29.8 a 3.7 37.7 a 5.3 19.5 b 2.2

Fungi 2.5 a 0.7 2.5 a 0.8 2.4 a 1.0 0.923

*Values are burning main-effect means (n = 18 to 26) and burning-by-year interaction means (n. = 8). Means within rows followed by

unlike letters are significantly (P ~0.05) different.

TUG = ungrazed, HS = heavy seasonal grazing, MY = moderate yearlong grazing, HY = heavy yearlong grazing.

*F-value probabilities for burning main effects. Values listed for east pasture browse and forbs are for the year-after-burning by yearof-study interaction terms.

4). Foraging efficiency was similar among grazing

treatments during spring and fall, but was significantly lower during summer and winter for both pastures under heavier phase 2 grazing (fig. 4).

The contribution of uncommon and/or ephemeral

plant species (“selectivity”) was highest under

ungrazed conditions (fig. 4). Heavier phase 2 grazing

significantly reduced forage selectivity on both pastures during spring and on the UG-HS pastures during winter.

Grazing Effects by Years After Burning

For a number of variables, grazing effects varied by

number of years after burning (P 50.038) (fig. 6). Acid

detergent fiber was significantly greater on third-year

than on first-year burns under UG conditions.

Calcium-to-phosphorus ratios were significantly lower

on second- and third-year burns than on first-year

burns under UG conditions. Deer traveled significantly

farther on first-year than on second- or third-year burns

under UG and HS grazing. Foraging efficiency tended

to be greater on second- and third-year burns than on

first-year burns, and these differences were significant

for UG conditions and for first- versus second-year burns

under MY grazing. Deer tended to forage more selectively on first- and second-year burns, but patterns were

inconsistent among grazing treatments.

Burning Effects by Season

For a number of response variables, the effects of

burning varied by season (P 50.003) (fig. 7). Within

seasons, differences were most apparent on first-year

burns; none of the differences (except for P intake

GRAZING TREATMENT

UG HHS q MY q HY

SPRING SUMMER FALL WINTER

Figure l.-Number of plant taxa eaten by white-tailed deer on a

pine-bluestem range, in central Lousiana, under

ungrazed (UG), heavy seasonal (HS), moderate yearlong (MY). and heavy yearlong (HIT) grazing by season.

Values are means for composited diets of three to five

deer over four to five sampling dates per season averaged across 3 years and three burned subunits. Means

within seasons labeled with unlike letters are significantly (P ~0.05) different.

5
during summer> between second- and third-year burns

were significant. Compared with second- and thirdyear burns, first-year burns yielded diets significantly

higher in CP and P during spring and summer, and

these differences tended to be reflected in CP and P

intake. Nevertheless, the effects of burning were short

lived, as fall and winter CP and P intake tended to be

higher on older (second- and third-year) burns. Calcium, Ca:P ratios, and CWC were also influenced significantly by burn ages (fig. 7).

Only forage intake and ADL had nonsignificant

burning-by-season interaction terms. Values for both

variables were significantly lower for first-year burns

(n = 237) than for second- (n = 232) or third-year burns

(n = 195), but values for second- and third-year burns

were alike (Z f SE: intake-l.34 + 0.03, 1.54 + 0.03,

1.49 f 0.04; ADL-9.67 + 0.15, 11.09 f 0.17, 10.89 +

0.16 [values are for the first, second, and third years

after burning, respectively]).

DISCUSSION

Available information indicates that forage preferences are similar for wild and tame deer (Neff 1974,

Olson-Rutzand Urness 1987, Wallmo and Neff 1970)

and that use of tame deer with extensive familiarity

with the study area should minimize potential biases

(Bartmann and Carpenter 1982). All of the deer used

in this study received extensive familiarization with

study areas prior to their use, and the two older deer

had 3.5 years of experience on grazed and ungrazed

forested range prior to this study.

Supplemental feeding apparently has little effect on

forage preferences (Regelin and others 19761, but its

effects on nutritional selectivity are unknown. Whether

wild deer on a lower nutritional plane would (or could)

select higher quality diets is unknown, but it appeared

that the deer in this study were attempting to maximize diet quality through selective foraging of phenologically young material from preferred species.

Findings by Thill and others (1987) and Hobbs and

others (1983) have shown that selection for uncommon and/or ephemeral species is positively correlated

with diet quality. Thus, although nutritional levels

presented here should be viewed only as estimates for

wild deer, the approach used in this study should be

valid for making relative comparisons when the same

animals and techniques are employed across treatments.

High dietary overlap is insufficient evidence of competition in the absence of concomitant data on reproduction, fawn survival (as it relates to nutrition and

hiding cover), or behavioral responses of deer to cattle

grazing practices. The findings from this study demonstrate that grazing and burning can affect deer by

altering forage composition and availability, which in

6

‘*Or (a)

---- SPRING

SUMMER

s 4 0 UG-HS PASTURE ‘\-1

2

\

2

2 0

0 I 2 3 4 5 6

& 120

(b)

4 0

t

‘.

MY -HY PASTURE - -

*ok

0 2 3 4 5 6

YEAR OF STUDY

Figure Z.-Yearly changes in the number of plant taxa eaten by

white-tailed deer on a pine-bluestem range in central

Louisiana. Each mean is based on composited data for

three to five deer over four to five dates per season for

three sampling areas (burned subunits) for (a) ungrazed

(UG) I heavy seasonally (HS) grazed pasture and (b)

moderate yearlong (My) I heavy yearlong (Hy) grazed

pasture.

turn affect foraging selectivity, foraging efficiency, diet

diversity, and diet quality. These interactions are often inconsistent and difficult to interpret (Mackie

1978). Some nutritional factors improved following

heavy grazing whereas others worsened. For example,

fall diets contained more P on both pastures after

heavy grazing, but estimated P intake declined during winter due to grazing-induced reductions in forage intake.

By late October, herbage removal across subunits

averaged 34,56, and 65 percent for MY, l!IY, and HS

treatments, respectively (table 1); herbage removal on

recently burned subunits averaged 46,77, and 67 percent for MY, HY, and HS treatments. If herbage use

had been measured on MY and HY pastures just prior
IO

GRAZING TREATMENT

16

14

12

IO

8

6

4

2

0

0.2 5

i=

5

2

0.20

4

L 0.15

2

8 0.10

z

:

2 0.05

Q

0.00

SPRING SUMMER FALL WINTER SPRING SUMMER FALL WINTER

SPRING SUMMER FALL WINTER

00

SPRING SUMMER FALL WINTER

n

SPRING SUMMER FALL WINTER

IS,

SPRING SUMMER FALL WINTER

-I

Figure 3.-Grazing-by-season effects on white-tailed deer diet quality on a pine-bluestem range in central Louisiana, 198047, for crude

protein, crude protein intake, phosphorus, phosphorus intake, calcium, and calcium-to-phosphorus ratio. UG = ungrated, HS =

heavy seasonal grazing, MY = moderate yearlonggrazing, HY = heavy yearlong grazing. Values are grazing-by-season interaction means fn = 36 to 45). Significant differences within seasons are denoted by unlike letters.

to spring greenup, use would have been considerably grazing treatments adversely affected CP, CP intake,

higher than in late October because grazing contin- P, or (with the exception of HY grazing during winter)

ued yearlong. Consequently, deer were exposed to rela- P intake. Although cattle grazing was associated with

tively high grazing pressure under all three grazing some increase in dietary fiber levels (fig. 5 1, the small

treatments, and especially so on the recently burned differences observed from spring through fall are likely

areas. Nevertheless, from a nutritional standpoint, of little biological significance. Thus, these data sugdeer were generally more affected by burning and sea- gest that any negative effect that cattle grazing may

sonal influences than by cattle grazing. None of the have on wild deer using comparable sites would likely

7
be more related to reductions in cover, availability of

preferred forage, and/or forage diversity than to reduction in forage quality per se.

Heavy seasonal and heavy yearlong grazing both

resulted in reduced floral diversity and availability of

preferred forages, and these reductions were accompanied by greater deer movement, reduced forage intake, and diets of lower diversity. At some threshold

following increasingly heavier cattle stocking, reductions in such factors as availability of preferred forage, forage diversity, and hiding cover presumably

would limit deer use of these areas despite possibilities for obtaining higher quality diets. Loft and others (1991) found that female mule deer (0. hemionus)

were not displaced from established home ranges by

moderate or heavy cattle grazing of their summer

range. However, in response to grazing, deer made

greater use of less preferred habitats that were avoided

by cattle, and deer home range sizes increased accordingly. Other accounts of spatial displacement of deer

by cattle are largely anecdotal; however, displacement

2

SPRING SUMMER FALL WINTER

0

SPRING SUMMER FALL WINTER

may be as or more important in deer/cattle interactions than forage competition. Despite close association with cattle for most of their lives, the deer in this

study always seemed skittish whenever cattle were

within sight or sound. Michael (1967) reports that

cattle and deer that grazed in close proximity usually

displayed mutual indifference. Others report displacement, movement of deer from heavier stocked to

lighter stocked pastures, or movement to areas with

greater grazing deferment (Cohen and others 1989,

Ellisor 1969, Hood and Inglis 1974, Kramer 1973,

Reardon and others 1978, Suring and Vohs 1979).

From a nutritional standpoint, late February burning resulted in significantly higher (relative to burns

from previous years) levels of forage CP and P during

spring and summer and P intake during spring in the

year immediately following burning (fig. 7). Deer also

consumed more uncommon and ephemeral species on

recent than on older burns of UG and MY treatments

(fig. 6), presumably due to increased physical availability following litter removal. The fact that deer were

“Ol

0.0

SPRING SUMMER FALL WINTER

1

i

1

SPRING SUMMER FALL WINTER

Figure 4.-Grazing-by-season effects on white-tailed deer foraging activity on a pine-bluestem range in central Louisiana, 1980-87, for

forage intake, distance traveled, foraging efficiency, and selectivity. Foraging efficiency ratio is the ratio of forage intake to

distance traveled per 30 minutes. UG = ungrazed, HS = heavy seasonal grazing, MY = moderate yearlonggrazing, HY = heavy

yearlonggrazing. Values are grazing-by-season interaction means (II = 36 to 45 except for selectivity where n = 24 to 30). Significant differences within seasons are denoted by unlike letters.

8
16 r I 5 0

GRAZING TREATMENT

s ‘4

% I2

UG atiS q MY •j HY

:

h;= IO

$5

24 $2

6

6

8 4

9

2

SPRING SUMMER FALL WINTER SPRING SUMMER FALL WINTER

SPRING SUMMER FALL WINTER

Figure 5.-Grazing-by-season effects on white-tailed deer diet quality on a pine-blue&em range in central Louisiana, 1980-87, for acid

detergent lignin, acid detergent fiber, and cell wall content. UG = ungrazed, HS = heavy seasonal grazing, MY = moderate

yearlong grazing, HY = heavy yearlong grazing. Values are grazing-by-season interaction means (n = 36 to 45). Significant

differences within seasons are denoted by unlike letters.

less selective on first-year burns of HS and HY treatments (fig. 6) likely resulted from reduced floral diversity due to much heavier cattle grazing. On the

negative side, burning reduced soft mast availability

and use (Thill and Martin 1986) and forage intake on

recent burns. Deer also generally traveled farther on

recent burns, which tended to lower foraging efficiency

(fig. 6).

Like others (Long and others 1986, Wood 1988), this

study shows that nutritional benefits of burning for

deer are short lived, but indicates that burning-induced differences in P intake and Ca:P ratios are substantial and likely of biological significance, especially

if P deficiency is the most limiting factor for southern

deer. Without periodic burning of southern pine ranges,

deer-carrying capacity would rapidly diminish as browse

grew beyond their reach and pine needle accumulations

reduced forage production and availability. Furthermore, burning will be required for restoration and

maintenance of longleaf pine stands, which now occupy only about 1.6 million ha of an estimated 24 million ha prior to European settlement (Boyer 1990).

MANAGEMENT IMPLICATIONS

The earlier findings for longleaf pine-bluestem sites

(Thill and Martin 1989) revealed substantial dietary

overlap between deer and cattle from late fall through

early spring, but largely complementary diets the remainder of the year, with deer using mostly browse

and forbs and cattle using mostly grasses. From late

fall through early spring, deer and cattle both sought

diets high in evergreen and tardily deciduous browse

and herbaceous winter rosettes. Because these items

are generally in limited supply, seasonal grazing from

late spring through early fall appeared less detrimental to deer (from a dietary overlap standpoint) than

yearlong grazing. However, data reported here reveal

no evidence to suggest that MY grazing by cattle would

be nutritionally detrimental to deer using similar sites.

Forage selectivity was significantly reduced under My

grazing (relative to UG conditions), but diet quality

under My grazing was comparable or better than under UG conditions. There would be less hiding cover

9
Y t YEAR AFTER BURN

UG HS M Y H Y

0.0

UG HS M Y H Y

U G H S M Y H Y

GRAZING TREATMENT

U G H S M Y H Y

0

U G H S MY H Y

GRAZING TREATMENT

Figure 6.-Grazing and burning effects on white-tailed deer diet quality and foraging activities on a pine-bluestem range in central Louisiana, 1980-87. Foraging efficiency ratio is the ratio of forage intake to distance traveled per 30 minutes. Values are

grazing-by-burning interaction means (n = 28 to 71, X = 52.8). UG = ungrated, HS = heavy seasonal grazing, MY = moderate

yearlong grazing, and HY = heavy yearlong grazing. Significant differences within grazing treatments are denoted by unlike

letters.

10
?

s

s

b 0 0

SPRING SUMMER FALL WINTER SPRING SUMMER FALL WINTER

0.3

0.0

SPRING SUMMER FALL WINTER

6

0

SPRING SUMMER FALL WINTER

I6 ,

I 6

2 2

?i %

I4

2 I.0 2 I2

s @ 020 I O

?l :s 6

G 0.5 ?i 6

94 2 4

g”

c, 2

0.0 0

SPRING SUMMER FALL WINTER SPRING SUMMER FALL WINTER

5 0

0

SPRING SUMMER FALL WINTER

Figure T.-Effects of season and burning on quality of diets selected by white-tailed deer on a pine-bluestem range in central Louisiana,

1980-87. Values are season-by-burn interaction means (n = 36 to 45). Significant differences within seasons are denoted by

unlike letters.

11
on recently burned, moderately grazed range than on

UG range, but with rotational burning on a 3-year

cycle, hiding cover should be adequate on roughly

two-thirds of each grazing allotment. Furthermore,

burning was largely beneficial to deer and is required

for maintenance of healthy longleaf pine communities.

Because cattle tend to prefer graminoids (Thill

1985), which are used little by deer, grazing policies

should be flexible enough that cattle release and removal dates can be adjusted to graminoid abundance.

Where low rainfall, early fall freezes, or a late spring

reduce graminoid supplies, stocking levels of cattle and

timing of grazing should be adjusted accordingly.

LITERATURE CITED

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Seasonal nutrient yield and digestibility of deer forage from a young pine plantation. Journal of Wildlife Management. 41(4): 667-676.

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Loft, Eric R.; Menke, John W.; Kie, John G. 1991. Habitat shifts by mule deer: the influence of cattle grazing.

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518-521.

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12
Reardon, P.O.; Merrill, L.B.; Taylor, C.A., Jr. 1978.

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in southern upland forests. In: Halls, Lowell K., ed.

White-tailed deer in the southern forest habitat:

symposium proceedings; 1969 March 25-26; Nacogdoches, TX. New Orleans, LA: U.S. Department of

Agriculture, Forest Service, Southern Forest Experiment Station: 14-18. In cooperation with: Forest Game

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and procedures of statistics. New York: McGraw-Hill

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use by Columbian white-tailed deer. Journal of Wildlife Management. 43(3): 610-619.

Thill, Ronald E. 1982. Deer and cattle diets on longleaf

pine-bluestem range. In: Sweeney, John R.;

Sweeney, James M., eds. Proceedings of the 36th

annual conference of the Southeastern Association

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410-419.

Thill, Ronald E. 1984. Deer and cattle diets on Louisiana pine-hardwood sites. Journal of Wildlife Management. 48(3): 788-798.

Thill, Ronald E. 1985. Deer and cattle compatibility

on southern forest range. In: Baker, Frank H.; Jones,

R. Katherine, eds. Proceedings of a conference on

multispecies grazing; 1985 June 25-28; Morrilton,

AR. Morrilton, AR: Winrock International Institute

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Thill, Ronald E.; Martin, Alton, Jr. 1986. Deer and

cattle diet overlap on Louisiana pine-bluestem

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707-7 13.

Thill, Ronald E.; Martin, Alton, Jr. 1989. Deer and

cattle diets on heavily grazed pine-bluestem range.

Journal of Wildlife Management. 53(3): 540-548.

Thill, Ronald E.; Martin, Alton, Jr.; Morris, Hershel

F., Jr.; McCune, E. Donice. 1987. Grazing and burning impacts on deer diets on Louisiana pine-bluestem range. Journal of Wildlife Management. 51(4):

873-880.

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H.; Parker, Kenneth W., eds. Range and wildlife

habitat evaluation-a research symposium; 1968

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180-186.

13
Thill, Ronald E.; Martin, Alton, Jr.; Morris, Hershel F., Jr.; Harrel, Austin

T. 1995. Effects of prescribed burning and cattle grazing on deer diets

in Louisiana. Res. Pap. SO-289. New Orleans, LA: U.S. Department of

Agriculture, Forest Service, Southern Forest Experiment Station. 13 p.

The effects of cattle grazing and rotational prescribed burning on diets

of white-tailed deer were studied on longleaf pine-bluestem sites in

central Lousiana.

Keywords: Diet diversity, intake, nutrition, Odocoileus virginianus
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