…as more individuals are produced than
can possibly survive, there must be a
struggle for existence.
C. Darwin
Wildlife Mortality
• Why is understanding wildlife mortality
important?
• What are the types of mortality?
• How do different types of mortality interact?
• What affects wildlife mortality?
• What is differential vulnerability?
Wildlife Mortality
• What is the difference between additive and
compensatory forms of mortality?
• Why do we consider harvest as a special type
of mortality?
• Why do we harvest wildlife?
• How do harvested and unharvested wildlife
populations differ? Why?
Wildlife Mortality
• What is a harvestable surplus?
• How and why do we regulate the harvest?
• Why is hunter and trapper education so
important?
• What about anti-hunters?
• Who cares?
Wildlife Mortality
• 1 - survival
• Patterns of survival
– Slope of line
• Importance
– Populations
– Emotions
Survivorship
Type I
← K-selected
Type II
Type III
Age
← r-selected
Wildlife Mortality
• Normal v. abnormal
– Management implications
(U.S Fish & Wildlife Service)
Wildlife Mortality
• Types
– Starvation & Malnutrition
– Disease & Parasites
– Accidents
– Predation
– Exposure
– Harvest
Natural
Natural can still be abnormal!
Wildlife Mortality
Death
Predation
Exposure
Disease & Parasites
Harvest
Accidents
Starvation & Malnutrition
Wildlife Mortality
• Proximate v. ultimate factors
– Implications
Wildlife Mortality
• Mortality Rates
– %/time, #/time, or ind/ind*time (d)
• Daily
• Seasonal
• Annual
– Sex/age class
Wildlife Mortality
• Density-dependence
Mortality Rate
– Types
C
A
B
Population Density
…starvation outside the breeding season
is the most important density dependent
factor in wild birds….
D. Lack
Wildlife Mortality
Starvation & Malnutrition
• What’s the difference?
• What types of wildlife starve to
death? Die of malnutrition?
• How common are these forms
of mortality?
(U.S Fish & Wildlife Service)
• Welfare or Decimating Factors?
• Proximate or ultimate factor?
(U.S Fish & Wildlife Service)
Wildlife Mortality
Starvation & Malnutrition
• Artificial feeding v. habitat improvement
• Management implications
– We failed as managers?
– Good intentions with bad results
(U.S Fish & Wildlife Service)
(U.S Fish & Wildlife Service)
Wildlife Mortality
Starvation & Malnutrition
• Artificial feeding v. habitat improvement
– Baiting & ethics
• Management implications
– We failed as managers?
Disease in a wildlife population is rarely a
simple, one-cause, one-effect situation.
Usually it is the product of profound
changes in the environment.
L. Karstad
Wildlife Mortality
Disease & Parasites
• Pathology
• Etiology
• Parasitology
• Epizootiology
– Enzootic
– Epizootic
• Welfare or Decimating Factors?
Wildlife Mortality
Disease & Parasites
• Causes of disease
– Intrinsic flaws
• Hereditary or congenital diseases
– Deficiency diseases*
– Exogenous poisons
– Trauma
– Tumors
– Living organisms*
Wildlife Mortality
Disease & Parasites
• Types of disease
– Toxicoses (poisons)
•
•
•
•
•
Organophosphate & carbamate pesticides
Organochlorine pesticides & PCB compounds
Aflatoxicosis
Lead poisoning
Oil toxicosis
Wildlife Mortality
Disease & Parasites
• Types of disease (living organisms)
– Avian Cholera
– Tularemia
– Brucellosis
– Sylvatic Plague
– Duck Virus Enteritis
– Aspergillosis
– Botulism
– Leptospirosis
– Anthrax
– West Nile Virus
– Lyme Disease
– Rabies
– Distemper
– Avian Pox
– Salmonella
– Tuberculosis
– Hemorrhagic Disease
– Chronic Wasting Disease
Wildlife Mortality
Disease & Parasites
• Types of parasites (living organisms)
– Gizzard worms
– Nasal leeches
– Gastrointestinal nematodes
– Lungworms
– Liver flukes
– Boophilus
– Psoroptes spp.
– Tapeworms
– Meningeal worms
– Nasal bots
– Ascarid roundworms
– Giardia spp.
– Trichomoniasis
– Mange
Wildlife Mortality
Disease & Parasites
• How common are these forms of mortality?
• Habitat affects
• Density-dependence
• Population regulation
Wildlife Mortality
Disease & Parasites
• Control & management
– Direct
– Indirect
• Use as biological control agents
– European rabbits in Australia
– Red imported fire ants
Wildlife Mortality
Disease & Parasites
• Wildlife diseases & people
– Rabies
– Lyme disease
– West Nile virus
– Avian influenza
– Chronic wasting disease (CWD)
Wildlife Mortality
Disease & Parasites
• Management implications
Accidental mortality is of greater concern
if the affected wildlife population is small,
so that a few accidentally killed animals
constitutes a fairly large proportion of the
population.
J.A. Bailey
Wildlife Mortality
Accidents
• Types
–
–
–
–
–
–
Collisions with objects
Drowning
Choking
Falls
Entanglement and entrapment
Research
• IACUC
• Welfare or Decimating Factor?
• Normal? Natural?
Wildlife Mortality
Accidents
• Prevalence
– >3,500,000 birds/yr killed by striking windows
(Banks 1979)
– Wildlife-vehicle collisions
(Schaefer et al. 2003)
Wildlife Mortality
Accidents
• Management implications
– National Safety Council (2000): 520,000
animal-related accidents resulting in 100
deaths and 4,000 injuries.
• Deer/auto collision cost about $2,000-8,000 per
claim for repairs and injuries.
– Romin and Bissonette (1996): >78,689
deer/auto collisions/yr with $124,092,553/yr in
damage
– Wildlife populations?
All living things are destined to die and be
recycled as a part of the flow of energy
through the life community. Which is to
say, a creature must feed, and sooner or
later it will be fed upon.
D.L. Allen
Wildlife Mortality
Predation
• Types of predation (Leopold 1933)
– Chance
– Habit*
– Sucker list*
– Starvation
– Sanitary
• Depredation?
• Jaguar case study
(U.S Fish & Wildlife Service)
Wildlife Mortality
Predation
• Carnivory
– Cannibalism
• Welfare or Decimating Factor?
Wildlife Mortality
Predation
• Protective refugia
– Density-dependence
– Threshold of Security
X
X
Wildlife Mortality
Predation
• Predator behavior
Predator Density
– Numerical response
Prey Density
Wildlife Mortality
Predation
• Predator behavior
# Prey Eaten/Predator
– Functional response
Prey Density
Wildlife Mortality
Predation
• Importance of predators
– Communities
• Stability & diversity
– Prey
• Buffer species
• Cycles & regulation
– “Thinking like a mountain”
Wildlife Mortality
Predation
• “Abnormal” predation
– Cats
• 1 cat: 60 birds & 1600 small mammals in
18 months (Schafer 1991)
• >19,000,000 songbirds & 140,000 game birds
killed/yr in Wisconsin
Kenneth M. Gale, www.forestryimages.org
• Feral & pet cats in the U.S. each year (USFWS study)
– <20.7 billion mammals
– <3.7 billion birds
Wildlife Mortality
Predation
• Predators & humans
– Livestock, pets, game species, etc.
– Opinions split or indifference
• Fear, economics, pets, & lack of understanding of value
Wildlife Mortality
Predation
• Predator control
– Methods
• Cost
• Effectiveness
Extremely Acceptable
Nonlethal Methods
Lethal Methods
Guard dogs
Repellent chemicals
Birth control
– Attitudes
• Coyotes
Shooting from the ground
Fast-acting poisons
(USFWS 1978)
Pay ranchers for losses
Aerial gunning
Denning
Pay ranchers not to raise livestock
Steel leghold traps
Slow-acting poisons
Not Acceptable at All
Wildlife Mortality
Predation
• Predator control
– Does it work?
• Coyotes
• Wolves
• Bears
• Quail, mallard ducklings, moose, sea turtles ….
– Effects on communities
• Thinking like a mountain!
Wildlife Mortality
Predation
• Management implications
– Normal
– Abnormal
– Predator control
Wildlife Mortality
Predation
• The case of quail
– Have we failed as mangers if we must control
predators to have quail to hunt?
–
–
–
–
–
–
–
Literature review
Weak or lack of data
Habitat management = predator management
IPM
Sympatric, parapatric, & allopatric
Proximate v. ultimate factors
Irruptions
Reasonably healthy bobwhites may
perish through imprisonment by drifting
snow.... Exposure to cold, high winds and
snow may kill reasonably healthy
bobwhites…. Although drifting and undue
cold is an infrequent occurrence, it
appears worthy of the game manager’s
attention, especially in the provision and
strengthening of cover.
T.G. Scott
Wildlife Mortality
Exposure
• Extreme cold or heat, blowing snow, or
intense rain or hail
– Direct & indirect effects of weather
• DD v. DI factor
• Periphery of range
• Food, cover, & water
– Proximate v. ultimate
• Welfare or Decimating Factor?
Wildlife Mortality
Exposure
• Density-dependent?
– Protective Refugia
• Management implications
X
X
Wildlife Mortality
• Effects vary
– Sex
– Age
– Season
– Behavior
– Region
– Northern Bobwhite example
Northern Bobwhite Survival
• Annual survival: 5-30%
– Higher in the South
– Males > females
– Lower in first year birds
• Seasonal differences
– Spring-Summer (breeding season): 13-51%
• South: fall-winter > spring-summer
• North: spring-summer > fall-winter
Northern Bobwhite Production
• Nest success
• Losses
– 32-44%
– Predation
• Mammals & snakes*
• Ants
– Weather
• 5-10% of adults killed
Northern Bobwhite Production
• Broods
– 14 days for thermoregulation & flight
• 30-40% survival
– Predation
– Weather
– 15-30% survival through
30 days
Quail Predation
• Primary cause of death
– Adults
• Avian predators: 40-65% of mortality
– During nesting & migration
• Cooper’s & sharp-shinned hawks in the SE
Quail Predation
• Mammalian predators
– Nesting & winter (north)
• Snakes
– Nesting
• Fire ants
– Chicks