Transcript Breeding and Non-breeding Survival of Lesser Prairie

HARVEST MANAGEMENT
John W. Connelly1, James H. Gammonley2 and Thomas W. Keegan3
1Idaho
Department of Fish and Game, 1345 Barton Road, Pocatello, ID 83221
2Colorado Division of Wildlife, 317 W. Prospect Road Fort Collins, CO 80526
3Idaho Department of Fish and Game, 99Highway 93 N, Salmon, ID 83467
INTRODUCTION
►
Interest in managing harvests has been widespread throughout
history
 Elements can be dated to the eighth century when Charlemagne instituted a
detailed set of game laws
►
►
Harvest management in North America dates to colonial times
Enactment of Federal Aid to Wildlife Restoration Act in 1937
provided states with a stable funding source to further support
harvest management programs
► For many biologists working for state and provincial wildlife agencies, harvest management
is where the “rubber meets the road”
►
Our purpose is to discuss the rationale and biology underlying
harvest management in NA and provide examples of successful
programs
 We also provide a synopsis of literature and attempt to identify and discuss
principles
RATIONALE FOR HARVEST
► In
North America, states and provinces are
responsible for harvest regulations pertaining to
“resident” wildlife, while federal authorities set
regulations for migratory game birds
►A
general underpinning of a harvest management
is that a biological surplus exists, which can be
harvested with little impact on subsequent
breeding populations
Approaches to Harvest Management
► The
3 approaches to harvest management include:
 (1) harvesting at a low rate to ensure population increase
 (2) harvesting to maintain a population
 (3) harvesting to reduce a population
Basic Components of Harvest
Management
► Harvest
management includes 3 basic
components:
 (1) inventory of populations
 (2) identification of population and harvest goals
 (3) development of regulations allowing goals to be
met
Requirements for Successful
Management
► Four
basic requirements for successful, informed
management of harvests
 1. Develop and agree upon explicit goals and objectives
 2. Implement actions designed to achieve objectives
 3. Have some idea of the likely effects of alternative
management actions
 4. Measure the outcome of actions in relation to
management objectives
Principles—Past and Present
► Additive
Mortality
 Each animal killed by hunters is an additional death that adds to
natural mortality, resulting in total mortality being greater than if
hunting did not occur
 Mackie et al. (1998) reported that hunting was additive to
overwinter mortality for white-tailed and mule deer; Bergerud
(1988) suggested this applied to many grouse species
► Compensatory Mortality
 Occurs when animals have relatively stable annual mortality,
regardless of which decimating factors may be acting on the
population
 Recent work suggests upland game hunting mortality is often not
compensatory
Additional Principles—Past and
Present
► Diminishing Returns
 Indicates that, past a certain point, hunting is largely
unrewarded, resulting in relatively few hunters in the field,
suggesting hunting is largely self-regulating
 The idea of diminishing returns appears to have little value for
present-day harvest management
► Doomed
Surplus
 Number of animals produced that exceed the capacity of the
habitat to support and keep secure from predation
 A number of wildlife species actually have high overwinter
survival and this concept seems to have limited usefulness
Additional Principles
► Harvestable
Surplus
 Indicates most animals produce more young than necessary to
maintain the population; this excess can be removed by
hunting without affecting the population.
 McCullough (1979) challenged this concept by arguing that it
fails to include “the dynamic and compensatory nature of
population responses.”
► Inversity
 An inverse relationship has been proposed to exist between
productivity and abundance
 Roseberry (1979) concluded that the system’s ability to
compensate for hunting losses progressively deteriorates as
harvest increases
More Principles
► Opening
Day Phenomenon
 Suggests most mortality for a given species occurs on opening day
of the season because that is when most hunters are afield
 Appear to be few published data available documenting hunting
pressure and harvest throughout the season
► Threshold of
Security
 Population size above which some animals are not secure from
predation
 Romesburg (1981) indicated this concept passed into the wildlife
profession without being critically evaluated or tested
Sources of Uncertainty
► Sources
of uncertainty about the relationship
between hunting regulations and game populations
 Partial Observability
 Partial Management Control
 Structural Uncertainty
 Environmental Variation
Management of Upland
Game Harvests
► Development of
Harvest Strategies
 Early Years (1900–1944)
►Largely
characterized by reduction in bag limits and season
length for many species of upland game
 Changing Strategies (1945–1980)
►Harvest
strategies tended to stabilize and became somewhat
more liberal in the 1960s and 1970s
►There was a strong tendency to believe reproductive
characteristics and effects of exploitation were the same for all
species of upland game
Development of Harvest Strategies
for Upland Game
 Current Knowledge (1981–2009): A New Paradigm
►New
information suggesting earlier views of harvest
management were not always correct
►During
1980s and 1990s, evidence began to suggest that,
under some circumstances, harvesting may have an additive
effect
►Recent
information suggests hunting mortality should be
viewed as occurring along a continuum and not as categorical
(i.e., either compensatory or additive)
Inventory of Upland Game
► Inventory
 A general approach would base harvest on
abundance of the species, but this is rarely done for
upland game
►Instead,
most harvest strategies seem to have been
developed through trial and error
Harvest Surveys of Upland Game
► Harvest
Surveys
 Most states have reduced emphasis on population
monitoring because of emphasized collection of
harvest data
 Many estimates of harvest have wide confidence
intervals, making comparisons among areas or years
difficult
►Lack
of population data makes it virtually impossible to
assess proportion of the population taken by hunters
Developing Regulations for Upland
Game
► Developing Regulations
 Varies among wildlife agencies
 Initial steps include:
►
Soliciting comments from agency personnel and public
► Regions or other administrative units then formulate
recommendations for the chief administrator of the agency’s
wildlife program
►Recommendations are discussed with the agency director
►Recommendations are passed on to the Wildlife Commission
for approval
Population Responses of Upland
Game to Hunting
► Population Responses
to Hunting
 Until the late 1970s, most studies suggested there were
few adverse effects of exploitation on upland game
 Within the last 25 years, numerous studies have
documented adverse effects of hunting on upland game
species
 Kokko (2001) warned that ignoring information on
species and population characteristics will “easily cause
hunting to be harmful to an unnecessary extent.”
Future Directions in Upland Game
Management
 Stocking
►Seen
as a legitimate and often necessary function of
harvest management
►Stocking is
likely reinforced among the hunting public
because stocking is a common activity of fisheries
management
►2
different harvest management programs involving game
bird stocking
 Release of birds before the gun
 Establish or augment existing game bird populations
Upland Game Shooting Preserves
 Shooting Preserves
►Hunting
preserves offer additional hunting opportunity
and a chance for individuals to train dogs prior to a general
season
 Appear to fill a need for more hunting areas at which hunters have
a better than average chance at being successful
Development of Harvest Strategies for
Migratory Game-birds
►
Approaches have been shaped primarily by recognition these animals
routinely cross local, state, provincial, and international borders
►
Effective monitoring of populations and harvests, and development of
regulations depends on cooperation across multiple levels of
government
►
Until reliable population and harvest surveys were developed,
regulations in the United States were set subjectively
►
As information was incorporated into the regulatory process, regional
or flyway-specific differences were recognized, and regulations
became more spatially complex
Models for Setting Regulations for
Migratory Game-birds
 Models were developed for use in setting regulations,
incorporating information from large-scale operational
monitoring programs
 Early models assumed hunting mortality was
completely additive and density-independent
 Anderson and Burnham (1976) produced new analyses
indicating compensatory mortality and introduced the
concept of structural uncertainty
Subsequent Model Analyses
 Subsequent analyses provided mixed evidence on effects of
hunting on annual survival in ducks, but hunting mortality
appears to be primarily additive for geese
 Recognition of alternative hypotheses about effects of hunting on
population dynamics led to a greater focus on addressing partial
management control and structural uncertainty
 After a period of stabilized regulations, federal authorities in the
United States adopted risk aversive conservatism toward setting
hunting regulations
►Relatively restrictive regulations would be adopted for
populations at low levels
Inventory of Migratory Game-birds
 Federal mandates to consider status of migratory game birds when setting regulations
motivated development of extensive monitoring programs in North America
 Monitoring programs support annual regulatory process and consist of annual collection of
data on abundance, production, distribution, harvest, other population parameters, and
habitat
 Population monitoring programs for waterfowl have a longer history and are more
extensive than surveys developed for most other migratory game birds
 Since 1955, the U.S. Fish and Wildlife Service and the Canadian Wildlife Service have
conducted annual aerial transect surveys, coupled with ground counts during May
 Winter (Jan) surveys of waterfowl have been conducted since the 1930s
 This survey is still the primary population index for ducks that occur outside of the May
survey area, and provides population indices for many goose populations in North America
 During May and July aerial waterfowl surveys observers record the number of ponds
containing water along transects in southern Canada and the north-central US
► The Canadian Wildlife Service monitors wetland habitat conditions on a sample of
survey transects each year in southern Canada
Annual Harvest Estimates for
Migratory Game-birds
 Annual harvest estimates are obtained using surveys
consisting of 2 components
►Hunter
Questionnaire Survey: is used to obtain
information on hunter activity and number of ducks and geese
harvested each year
►Parts
Collection Survey: involves mailing envelopes to a
sample of hunters who are asked to mail in wings of ducks and
tail feathers of geese they shoot
Harvest Information Program for
Migratory Game-birds
 In 1991, a new Harvest Information Program was initiated to
provide a reliable, nationwide sampling frame of all migratory bird
hunters
 Under HIP, each state collects the name, address, and birth date of
each person hunting migratory game birds, asks each hunter a
series of questions about their hunting success the previous year
and provides this information to the USFWS
►The
traditional sampling procedure was replaced with the HIP
sampling frame beginning with the 2002–2003 hunting season
Role of Banding for Migratory Gamebird Management
 Mark–recovery methods enable managers to obtain
important information about populations. To use these
methods, individually numbered leg bands are placed on
migratory game birds
 Information helps identify distribution of harvest and
harvest areas, estimate harvest rates and relative
vulnerabilities to harvest of gender and age cohorts, and
estimate age- and gender-specific survival rates
Governmental Roles in Regulating Hunting
of Migratory Game-birds
►Primary
federal authority and responsibility for migratory birds
was established after the signing of the Convention for the
Protection of Migratory Birds by representatives from the United
States and Great Britain in 1916
►Migratory Bird Treaty Act of 1918 implemented the convention in
the US
 This Act was later amended to incorporate similar treaties with Mexico,
Japan, and Russia
 Under the Migratory Bird Treaty Act, the Secretary of the Interior authorizes
hunting and adops regulations for this purpose
►Regulations must
be based on status and distribution of migratory
game birds and updated annually
►This responsibility has been delegated to the U.S. Fish and Wildlife
Service
Flyway Councils
 In 1947 the United States was divided into 4
administrative Flyway Councils for establishing
annual hunting regulations
 Through these Councils, representatives from state
and federal agencies in the United States, Canada,
and Mexico have coordinate management activities
and develop annual hunting regulations
The Regulations Process
Regulations process
Month
Monitoring
January
February
March
•Midwinter waterfowl and crane surveys
•Parts Collection Survey wing bees
•Hunter Questionnaire Surveys; banding
analysis for duck harvest and survival
rates
April–May
Breeding waterfowl and habitat, dove
call-count, and woodcock singing-ground
surveys
SRC meets to recommend “early” season
regulations Harvest survey results available
June
Harvest survey results available
Flyway Councils develop recommendations
July
Waterfowl production surveys
SRC recommend “late” season regulations
August
Preseason duck banding
“Early hunting” seasons begin
September
Autumn surveys for sandhill cranes,
greater white-fronted geese
“Late” hunting seasons begin
October
U.S. Fish and Wildlife Service regulations
Committee (SRC) meets to identify issues
Flyway Councils develop recommendations
Management of Migratory Game-bird
Harvests
►
Features of adaptive harvest management for mallard populations




►
Set of alternative models
Measure of reliability for each model
Limited set of regulatory alternatives
Objective function or mathematical description of the objective(s)
The setting of annual hunting regulations involves a 4-step
process:
 Each year the optimal regulatory alternative is identified
 Once the regulatory decision is made, model-specific predictions for
subsequent breeding population size are calculated
 When monitoring data are available, model weights are updated
 New model weights used to start a new iteration of the process
Harvest Management of Overabundant
Species
 Primary goal for migratory game birds continues to be
prevention of overharvests
 However, hunting has often been used to reduce or
control the density of birds on local scales
 Several continental populations of geese have grown
rapidly
►In
1999, U.S. Fish and Wildlife Service authorized new
methods of take for light geese and established a
conservation order permitting take outside dates established
by Migratory Bird Treaty Act
Management of Big Game Harvests
► In
contrast to harvest management of upland
game and waterfowl, management of big game
harvest is often more complex and contentious
because:
 Ability of hunters to differentiate among gender and
age classes
 Variety of weapons used for harvest
MANAGEMENT OF BIG GAME
Populations
► Management of
large mammal populations is a
4-step, linear process
 (1) inventory (identify current or potential population
status)
 (2) define goals and objectives (identify desired
population status)
 (3) develop strategies to achieve objectives,
 (4) evaluate how well strategies met objectives
Inventory of Big Game
 Typically involves estimating current population
status
 Biological capacity to produce and sustain a given
species
►Should
be based on geographical areas containing
relatively discrete populations
 Inventories may be designed to estimate population
abundance or provide an index to population status
►Determine
age and gender ratios
Harvest Surveys for Big Game
► Harvest
Surveys
 Surveys conducted by wildlife agencies estimate
harvest across multiple species, seasons, weapon
types, and management units
►Data
collected include number of animals harvested by
gender and age class, hunter effort, location, date of
harvest, weapon used
► Variety
of methods to estimate harvest:
►Check
stations, mandatory checks, report cards, random
mail or telephone surveys, toll-free telephone service,
Internet- based reporting
Harvest Strategies for Big Game
► Development of
Harvest Strategies
 Harvest theory for most big game species is
generally based on concepts of biological carrying
capacity (K) and density-dependent population
growth
►Determination of
K for wild populations is very difficult;
K often changes through time
 Practical management of big game populations is
more likely to be based on social carrying capacity
Developing Regulations for Big
Game
 Wide variety of harvest regulations and season structures are applied across
jurisdictions and species
► Local tradition and history often play important roles in determining harvest
systems
 Regulations should be easily understood by hunters and enforceable
► Concept of fair chase is integral to developing regulations, but definition of fair
chase varies
 To provide a framework for evaluation, managers should implement regulations
that are consistent and stable over long enough periods to encompass normal
variability
► Changing season length and timing annually will virtually eliminate the
possibility of estimating effects of different season structures
 Evaluation is an often neglected aspect of the regulation process
Population Responses of Whitetailed Deer to Hunting
►Challenge
for managers is finding ways to
increase harvest, particularly for females
►Principles
of sustained yield management based
on density dependence can be applied with more
certainty than in more variable systems
Population Responses of Mule Deer
to Hunting
► Minimum
APRs are generally effective at reducing buck mortality and
increasing total buck:doe ratios, but have almost invariably failed to increase
mature buck:doe ratios or absolute number of mature bucks
► Effects of
altering season length are equivocal and typically confounded by
concurrent change in season timing
 In general, reducing the number of days available to hunt has a negligible
effect on total harvest
► Altering harvest management
to increase buck ratios for the explicit purpose of
increasing productivity is unwarranted
► Effects of
female harvest depend on adult female natural mortality rates and
fawn recruitment
 Determine appropriate harvest rates based on population-specific
demographic data and population monitoring
Population Responses of Elk to
Hunting
►Several
regulatory approaches have proven
successful in increasing bull:cow ratios
►Moving centerfire-weapon seasons out of rut
typically reduces bull harvest rates
►Maximum APRs (i.e., spike-only) may increase
bull ratios
►A somewhat complex season system designed to
attract hunters to seasons where they would be
less successful may increase bull ratios
Population Responses of Bear to
Hunting
 As harvest rates increase, average age of males
declines and proportion of females in harvest
increases
►If
females comprise ≤35% of harvest and
average age of males is ≥4, population is likely
stable
►Refuge areas may serve as repopulation sources
for more heavily hunted areas
Sustained Yield Management
 Maximum sustained yield (MSY) is achieved when
populations are at approximately K/2
 Management for MSY has received criticism and
been blamed for overharvest of some species
 In systems characterized by large variability in
weather and habitat, density-dependent population
responses may be overshadowed by stochastic
processes, thus reducing appropriate yield levels
Principles of Sustained Yield
Management
►
Any exploitation of a population
reduces its abundance
►
Below a certain exploitation level,
populations may be resilient and
increase survival and/or production and
growth rates to compensate for
individuals removed
►
►
When populations are regulated
through density dependent processes,
exploitation rates will tend to increase
productivity and reduce natural
mortality of remaining individuals
Exploitation rates above maximum
sustained yield will reach a point at
which extinction will occur if
exploitation is continued
►
Age composition and number of animals
remaining after exploitation are key factors
in the dynamics of exploited populations
►
If a population is stable, it must be reduced
below that density to generate a
harvestable surplus
►
For each density to which a population is
reduced, there is an appropriate sustained
yield
►
For each sustained yield, there are 2
density levels at which it can be harvested
►
Maximum sustained yield may be
harvested at only one density, about 1-half
resource based carrying capacity
SUMMARY
► As
interest of nonhunters in management increases,
importance of biologically defensible harvests also will
increase
► Changing landscapes will alter at least some wildlife
populations
 Approaches to harvest management for some populations
will likely have to change
► Management decisions backed by sound science and
rigorous data collection will alleviate some difficulties