Download POPULATION-LEVEL EFFECTS OF PREDATION

POPULATION-LEVEL
EFFECTS OF
PREDATION
I. THE ROLE OF PREY DENSITY
Coccoons O pened
A. Functional Response of Predators
D e e r M ic e a n d P in e S a w flie s
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S o u rc e : C a u g h le y a n d S in c la ir (1 9 9 4 , W ild life e c o lo g y a n d m a n a g e m e n t)
I. THE ROLE OF PREY DENSITY
Predator density
B. Numerical Response of Predators
Num erical Response Curve
Prey Density
I. THE ROLE OF PREY DENSITY
C. Total Response of Predators
Vital Rate (%)
A
Mortality (+)
Recruitment
Mortality (-)
Prey Density
B
K
II. DO MAMMALIAN PREDATORS
REGULATE PREY POPULATIONS?
A. Predators of Waterfowl
II. DO MAMMALIAN PREDATORS
REGULATE PREY POPULATIONS?
A. Predators of Waterfowl
II. DO MAMMALIAN PREDATORS
REGULATE PREY POPULATIONS?
II. DO MAMMALIAN PREDATORS
REGULATE PREY POPULATIONS?
B. Wolves and
Ungulates
–
–
Declining
caribou, moose,
Dall sheep
populations in
Yukon
Experimental
reduction of
wolves over 5
years
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II. DO MAMMALIAN PREDATORS
REGULATE PREY POPULATIONS?
B. Wolves and Ungulates
–
–
–
Declining caribou, moose, Dall sheep
populations in Yukon
Experimental reduction of wolves over 5 yrs
Wolf predation was
»
»
reducing recruitment of caribou & moose calves
reducing adult survival of moose
II. DO MAMMALIAN PREDATORS
REGULATE PREY POPULATIONS?
C. Weasels
–
and voles in western USA
–
and voles in Russian crop ricks
II. DO MAMMALIAN PREDATORS
REGULATE PREY POPULATIONS?
D. Overview
III. INTERACTION OF PREDATION
AND COMPETITION
A. Lynx and Hares
–
During peak hare year:
III. INTERACTION OF PREDATION
AND COMPETITION
B. Wildebeest and Lions-Hyenas
1. Predation-sensitive food hypothesis
(PSFH)
2. Predator regulation hypothesis
(PRH)
3. Surplus prey hypothesis (SPH)
III. INTERACTION OF PREDATION
AND COMPETITION
Vital Rate (%)
PRH
Mortality
Recruitment
PSFH
SPH
Prey Density
K
IV. INDIRECT EFFECTS OF
PREDATORS ON PREY
 Indirect
effect:
– Effect of one species on another is
mediated through a third
IV. INDIRECT EFFECTS OF
PREDATORS ON PREY



Example: Iberian lynx
Egyptian mongoose
European rabbit
Rabbits preyed upon: 5-10 fold increase in
absence of lynx
Rabbit density: 2-4 fold lower in areas
without lynx
V. THE CONCEPT OF
COMPENSATORY EFFECTS
Compensatory
–
Mortality
Substitution of mortality agents
V. THE CONCEPT OF
COMPENSATORY EFFECTS
Compensatory
Mortality
Substitution of mortality agents
– Example: deer in predator-removal area
–
V. THE CONCEPT OF
COMPENSATORY EFFECTS
 Compensatory
–
–
Mortality
Substitution of mortality agents
Example: woodchucks in Pennsylvania
V. THE CONCEPT OF
COMPENSATORY EFFECTS
Other
–
Types of Compensation
Example: woodchucks on a hunted site
» increased survival of juveniles
» reduced emigration of juveniles
» increased fertility of yearling females