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…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
Age
Sur
vivo
rshi
p
Type II
Type I
Type III
← K-selected
← 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
Harvest
Death
Disease & Parasites Starvation & Malnutrition
AccidentsExposure
Predation
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– Types
Population Density
Mor
talit
y R
ate
B
C
A
…starvation outside the breeding season is the most important density dependent factor in wild birds….
D. Lack
Wildlife MortalityStarvation & Malnutrition
• What’s the difference?
• What types of wildlife starve to death? Die of malnutrition?
• How common are these forms of mortality?
• Welfare or Decimating Factors?
• Proximate or ultimate factor?(U.S Fish & Wildlife Service)
(U.S Fish & Wildlife Service)
Wildlife MortalityStarvation & 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 MortalityStarvation & 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 MortalityDisease & Parasites
• Pathology
• Etiology
• Parasitology
• Epizootiology– Enzootic– Epizootic
• Welfare or Decimating Factors?
Wildlife MortalityDisease & Parasites
• Causes of disease– Intrinsic flaws
• Hereditary or congenital diseases
– Deficiency diseases*– Exogenous poisons– Trauma– Tumors– Living organisms*
Wildlife MortalityDisease & Parasites
• Types of disease– Toxicoses (poisons)
• Organophosphate & carbamate pesticides• Organochlorine pesticides & PCB compounds• Aflatoxicosis• Lead poisoning• Oil toxicosis
Wildlife MortalityDisease & 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 MortalityDisease & 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 MortalityDisease & Parasites
• How common are these forms of mortality?
• Habitat affects
• Density-dependence
• Population regulation
Wildlife MortalityDisease & Parasites
• Control & management– Direct– Indirect
• Use as biological control agents– European rabbits in Australia– Red imported fire ants
Wildlife MortalityDisease & Parasites
• Wildlife diseases & people– Rabies– Lyme disease– West Nile virus– Avian influenza– Chronic wasting disease (CWD)
Wildlife MortalityDisease & 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 MortalityAccidents
• Types– Collisions with objects– Drowning– Choking– Falls– Entanglement and entrapment– Research
• IACUC
• Welfare or Decimating Factor?• Normal? Natural?
Wildlife MortalityAccidents
• Prevalence– >3,500,000 birds/yr killed by striking windows
(Banks 1979)
– Wildlife-vehicle collisions(Schaefer et al. 2003)
Wildlife MortalityAccidents
• 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 MortalityPredation
• Types of predation (Leopold 1933)
– Chance– Habit*– Sucker list*– Starvation– Sanitary
• Depredation?
• Jaguar case study
(U.S Fish & Wildlife Service)
Wildlife MortalityPredation
• Carnivory– Cannibalism
• Welfare or Decimating Factor?
Wildlife MortalityPredation
• Protective refugia– Density-dependence– Threshold of Security
XX
Wildlife MortalityPredation
• Predator behavior– Numerical response
Prey Density
Pre
dato
r D
ensi
ty
Wildlife MortalityPredation
• Predator behavior– Functional response
Prey Density
# P
rey
Eat
en/P
reda
tor
Wildlife MortalityPredation
• Importance of predators– Communities
• Stability & diversity
– Prey• Buffer species• Cycles & regulation
– “Thinking like a mountain”
Wildlife MortalityPredation
• “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
• Feral & pet cats in the U.S. each year (USFWS study)
– <20.7 billion mammals– <3.7 billion birds
Kenneth M. Gale, www.forestryimages.org
Wildlife MortalityPredation
• Predators & humans– Livestock, pets, game species, etc.
– Opinions split or indifference• Fear, economics, pets, & lack of understanding of value
Wildlife MortalityPredation
• Predator control– Methods
• Cost• Effectiveness
– Attitudes• Coyotes (USFWS 1978)
Extremely Acceptable
Not Acceptable at All
Slow-acting poisonsSteel leghold traps
DenningAerial gunning
Shooting from the groundFast-acting poisons
Pay ranchers not to raise livestock
Pay ranchers for losses
Birth control
Repellent chemicalsGuard dogs
Nonlethal Methods Lethal Methods
Wildlife MortalityPredation
• Predator control– Does it work?
• Coyotes• Wolves• Bears
• Quail, mallard ducklings, moose, sea turtles ….
– Effects on communities• Thinking like a mountain!
Wildlife MortalityPredation
• Management implications– Normal– Abnormal
– Predator control
Wildlife MortalityPredation
• 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 MortalityExposure
• 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 MortalityExposure
• Density-dependent?– Protective Refugia
• Management implications
XX
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
– 32-44%
• 5-10% of adults killed
• Losses– Predation
• Mammals & snakes*• Ants
– Weather
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