Transcript Slide 1

Non-native Warm Season
Grasses: How do they
Impact White-tailed
Deer?
Timothy E. Fulbright
Synopsis
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Non-native grasses continue to spread via
invasion and intentional propagation
No scientific documentation of effects on
deer productivity
We only have hypotheses
 Potential exists for negative impacts
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Research needed
Outline
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What are non-native grasses?
Spread of non-native grasses
Rate of spread
 Reasons for spread
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Potential impacts on deer habitat
Forage
 Fawn cover
 Change in fire regimes
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What Are Non-native Grasses?
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Grasses that did not evolve in North
America
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Buffelgrass
Bermudagrass
Old world bluestems (Kleberg, KR, Silky, Angleton)
Lehmann lovegrass
Blue panicum
Johnsongrass
Kleingrass
Lovegrasses (Lehmann, Wilman, Weeping)
Rhodesgrass
Spread of Non-native Grasses
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We don’t know how fast they are spreading
or how many new acres planted each year
Buffelgrass predicted to cover 12% of
Mexico
Why are Non-native Grasses
Increasing
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Intentional planting
CRP
 Rangeland seeding
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Disturbance
Climate change?
Why are Non-native Grasses
Increasing

Intentional planting
CRP
 Rangeland seeding
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Disturbance
Climate change?
Buffelgrass canopy cover
P = 0.02
%
30
20
10
0
Pre
1
2
3
4
Years post-treatment
Control
Disced in 1990
5
Does fire facilitate exotic grass
invasion?
Disturbance
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Lehmann lovegrass increases following fire
and drought
Re-establishes more successfully than
natives because of
Abundant seed
 Germination strategies
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Angell and McClaran. 2001. J. Arid Environ. 49:507-520.
Why are Non-native Grasses
Increasing
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Intentional planting
CRP
 Rangeland seeding
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Disturbance
Climate change?
Freezing temps
 Summer rainfall
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Guineagrass
Killed by temperatures
< 20 C
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May
July
3.5
3
2.5
Median 2
rainfall
(inches) 1.5
1
0.5
0
1937-46 1947-56 1957-66 1967-76 1977-86 1987-96 1997-06
May
July
3.5
3
2.5
Median 2
rainfall
(inches) 1.5
1
0.5
0
1937-46 1947-56 1957-66 1967-76 1977-86 1987-96 1997-06
Non-native Grasses & Deer
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Forage?
Fawn cover?
Fire regimes?
Seed Company in South Texas
Actual wording from website
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“Buffel grass is an excellent source of feed
for white tail deer and other wildlife”
“Buffel grass also provides great cover for
the does to hide their fawns”
“The fact that deer will graze on Buffel grass
allows game managers to control the habitat
conditions for the deer”
M. W. Meyer, R. D. Brown and M. W. Graham. Protein
and Energy Content of White-Tailed Deer Diets in the
Texas Coastal Bend. Journal of Wildlife Management
48:527-534.
Forage
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Deer prefer forbs
Negative relationship between canopy cover
of exotic grasses and forbs
100
Guineagrass
cover vs. forb
cover
Forb canopy cover (%)
r = - 0.50
80
60
40
20
0
0
20
40
60
80
100
Guineagrass canopy cover (%)
Forb cover negatively
related to Lehmann
Lovegrass cover in
Arizona
Williams and Baruch. 2000. Biological Invasions 2:123-140.
Fawn Cover
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Why do you have more fawns when you have
more grass? Hypotheses - 
Hiding cover?
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Nutrition?
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But does with fawns on Welder selected brushdominated areas and avoided grasslands
Reduced grazing = more forbs
More grass = more buffer species?
Fawn Cover
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Guthery, F. S., T. E. Anderson, and V. W.
Lehmann. 1979. Range rehabilitation
enhances cotton rats in south Texas. J.
Range Manage. 32:354-356.
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Cotton rat densities 4 times greater in rangeland
dominated by buffelgrass & KR bluestem than
in native rangeland
Fire Regimes
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Reduced regeneration of browse plants?
Conclusions
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Increase in non-native grasses may reduce forbs
& woody cover
Deer are highly adaptable and are very plastic in
food habits
invasion of non-native grasses may have little impact
 impact may be difficult to detect, particularly in the
short term
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The Future
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Global warming & shift to summer rainfall may
favor subtropical grasses such as buffelgrass,
Natal grass, Guineagrass, Lehmann lovegrass
Research Needs
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Habitat use – do deer avoid areas dominated by
non-native grasses?
GPS collars – habitat selection/avoidance
 Foraging studies with tame deer – do they avoid
patches of non-native grasses?
 Telemetry work with fawns – selection of non-native
vs. native patches; survival of fawns bedding in nonnatives versus exotics
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Carrying capacity studies with confined deer