Transcript Elk Herds - Nevada Department of Wildlife

• Not every animal, either adult or juvenile, lives for
ever; hard concept for many people to appreciate
• Carrying Capacity – ability of the habitat and
distribution of resources to support a certain
population level
• Harvest/Removal management strategies –
– What is the population goal? Social and/or ecological
carrying capacity
– Where is the population in relation to the goal or
population objective?
– What rate of removal will meet the goal?
– Monitor the population response to removal
– Compensatory vs. Additive Mortality
– Density Dependent Reproduction
– Make annual adjustments to removal rates
• Run through real examples of current elk,
pronghorn, and bighorn herds
Elk Herds
40%
800
700
30%
600
20%
500
10%
400
300
0%
200
-10%
100
-20%
0
1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010
Rate of Increase
%Cow Harvest of Total Cow Elk
Population Estimate
Population Estimate
Percent Population Change & Cow Elk Harvest
Elk Herd Parameters for Unit Group 161 - 164
Elk Herd Parameters for Unit Group 111-115, 221, 222
6000
15%
5000
10%
4000
5%
3000
0%
2000
-5%
1000
-10%
-15%
0
1990
1992
1994
Rate of Increase
1996
1998
2000
2002
2004
%Cow Harvest of Total Cow Elk
2006
2008
2010
Population Estimate
Population Estimate
Percent Population Change & Cow Elk Harvest
20%
30%
1800
25%
1600
20%
1400
15%
1200
10%
1000
5%
800
0%
600
-5%
-10%
400
-15%
200
-20%
0
1993
1995
1997
Rate of Increase
1999
2001
2003
2005
%Cow Harvest of Total Cow Elk
2007
2009
2011
Population Estimate
Population Estimate
Percent Population Change & Cow Elk Harvest
Elk Herd Parameters for Unit Group 072, 074
Pronghorn Herds
3500
15%
3000
2500
10%
2000
5%
1500
0%
1000
-5%
500
-10%
0
1996
1998
2000
Rate of Increase
2002
2004
2006
2008
Population Estimate
2010
Herd Population Estimate
Percent Population Change & Doe Harvest
20%
4000
10%
3500
3000
5%
2500
0%
2000
-5%
1500
-10%
1000
-15%
500
-20%
0
1996
1998
2000
2002
Rate of Increase
2004
2006
2008
Population Estimate
2010
Herd Population Estimate
Percent Population Change & Doe Harvest
15%
20%
3500
15%
3000
2500
10%
2000
5%
1500
0%
1000
-5%
500
-10%
0
1996
1998
Rate of Increase
2000
2002
2004
2006
%Doe Harvest of Total Doe Pronghorn
2008
2010
Population Estimate
Herd Population Estimate
Percent Population Change & Doe Harvest
Pronghorn Herd Parameters for Unit Group 032,034,035 with Doe Harvest
25%
1800
1600
15%
1400
5%
1200
1000
-5%
800
-15%
600
400
-25%
200
-35%
1997
1999
Rate of Increase
2001
2003
2005
2007
%Doe Harvest of Total Doe Pronghorn
2009
2011
0
Population Estimate
Herd Population Estimate
Percent Population Change & Doe Harvest
Pronghorn Herd Parameters for Unit Group 067, 068 with Doe Harvest
20%
1800
1600
15%
1400
10%
1200
1000
5%
800
0%
600
400
-5%
200
-10%
0
2006
Rate of Increase
2007
2008
2009
2010
%Doe Harvest of Total Doe Pronghorn
2011
Population Estimate
Herd Population Estimate
Percent Population Change & Doe Harvest
Pronghorn Herd Parameters for Unit Group 031 with Doe Harvest
20%
2000
15%
1800
1600
10%
1400
5%
1200
0%
1000
-5%
800
600
-10%
400
-15%
200
-20%
0
1998
2000
Rate of Increase
2002
2004
2006
2008
%Doe Harvest of Total Doe Pronghorn
2010
Population Estimate
Herd Population Estimate
Percent Population Change & Doe Harvest
Pronghorn Herd Parameters for Unit Group 111-114 with Doe Harvest
35%
1000
900
25%
800
15%
700
600
5%
500
-5%
400
300
-15%
200
-25%
-35%
100
1997
1999
2001
2003
Rate of Increase
2005
2007
Population Estimate
2009
2011
0
Herd Population Estimate
Percent Population Change & Doe Harvest
Pronghorn Herd Parameters for Unit Group 101-104,108,109,144
Bighorn Herds
• River Mountains - Desert Bighorn Sheep
– 1986 – 240 population estimate
– From 1986 – 2010 removed 436 bighorn
– 2011 – 250 population estimate
• Mt Jefferson – Desert Bighorn Sheep
– 2003 – 290 population estimate
– From 2003 – 2008 removed 116 bighorn
– 2010 – 280 population estimate
Compensatory Mortality –
• improved survival of remaining animals not
harvested or they are “compensating” for the
loss of animals to harvest
Additive Mortality –
• no improvement in survival of animals that
were not harvested, therefore loss of
harvested animals is in “addition” to animals
that die to nonharvest mortality factors
Comparison of Doe Pronghorn Survival Rates
0.98
0.96
Annual Survival Rate
0.94
0.92
0.9
0.88
0.86
0.84
0.82
0.8
0.78
YEAR
067, 068
041, 042
Comparison of Doe Pronghorn Survival Rates
1
Annual Survival Rate
0.95
0.9
0.85
0.8
0.75
0.7
0.65
0.6
YEAR
032, 034, 035
012 - 014
Female Pronghorn Age Classes
One+
1
2
3
4
5
6
7
8
9
10
does
129
86
95
60
95
51
67
72
52
28
734
Aug 2005
-5
-3
-4
-2
-4
-2
-3
-3
-2
-1
-29
Harvest
-2
-1
-1
-1
-1
-1
-1
-1
-1
0
-9
Wounding Loss
-21
Nonhunting
Mortality
675
survived to
Feb 2006
-4
119
-2
79
-3
87
-2
55
-3
87
-1
47
-2
61
-2
66
-1
48
-1
25
-4
-4
-2
-3
-2
-3
-1
-2
-2
-1
-23
Nonhunting
Mortality
133
115
76
84
53
84
46
60
64
47
762
Aug 2006
Same Unit 067, 068 Pronghorn Herd without Harvest
Female Pronghorn Age Classes
One+
1
2
3
4
5
6
7
8
9
10
does
129
86
95
60
95
51
67
72
52
28
734
-6
-4
-5
-3
-5
-3
-3
-4
-3
-1
-37
Aug 2005
Nonhunting
Mortality
123
81
90
57
90
49
64
68
50
26
697
Survived to Feb
-7
-6
-4
-4
-3
-4
-2
-3
-3
-2
-34
Nonhunting
Mortality
135
117
77
85
54
85
46
60
65
47
772
Aug 2006
Age Class #s with Harvest and Compensatory Mortality
133
115
76
84
53
84
46
60
64
47
762
Aug 2006
• Statewide Pronghorn estimate for 2011 was 27,000.
• Several pronghorn herds statewide are at or
approaching their current carrying capacity.
• Other herds are one catastrophic fire away from losing
a significant proportion of their habitat.
• Almost 1,300 doe (horns shorter than ears) tag
applicants in 2011; 5 to 1 draw odds; tremendous
demand from hunters.
• By applying a 3-5% harvest rate to the doe segment of
these herds, we can better manage herds to their
habitat, reduce major declines when catastrophic
events occur and provide substantial hunting
opportunities where expressed demand exists.