Plan for Reducing Mottled duck X
Mallard Hybridization
Attachment
A of a
Report to Commissioners, May 15, 2002,
Reducing Mallard Releases
I.
Background Information
A.
Conservation Plan –
The Conservation Plan for the Florida Mottled Duck (Florida Fish and
Wildlife Conservation Commission 1999) sets forth a population
management objective as follows:
“Maintain the most recent five-year average estimate of mottled duck
breeding population density at or above 0.7 birds/km2 within
the currently surveyed area, or at or above the current level as
determined by a revised survey.”
One of the specified strategies for achieving this objective is to
minimize interbreeding and hybridization between mottled ducks and
mallards by (1) identifying and implementing mechanisms to reduce
hybridization including distributing public information materials
describing the problem, why it is occurring, and how it can be reduced,
(2) evaluating or developing techniques to identify hybrids, and (3)
periodically assessing the proportion and distribution of hybrids in the
population.
This plan functions as a sub-plan of The Conservation Plan for the
Florida Mottled Duck and provides more detailed strategies and tasks for
reducing hybridization.
B.
Need for Action –
Feral mallards pose a major threat to the conservation of Florida’s
endemic mottled duck (Anas
fulvigula fulvigula)
because the two closely related species interbreed, resulting in
fertile, hybrid offspring. Florida’s
mottled duck is nonmigratory, is genetically distinct from mottled ducks
occurring elsewhere in the country, and occurs only in peninsular
counties of the state.
Their existence is threatened by interbreeding with feral mallards and
by rapid changes in Florida’s
landscape, mostly resulting from agricultural and urban development.
The mottled
duck is
a defining member of the unique suite of wildlife species characteristic
of the prairie ecosystem of southern Florida.
An estimated 5% of Florida's mottled duck population exhibits
hybrid characteristics, based on wing plumage.
This is a minimum estimate of the proportion of the population that
is hybridized because many mallard genes are not expressed
visibly.
Worldwide, mallard-type species repeatedly have been partially or,
perhaps
in one case,
completely hybridized out of existence by introduced mallards. As illustrated by the decline and loss of these other
similar species, mallard x mottled duck hybridization can be a
devastating problem, and a comprehensive strategy is needed to address
it. Unless the release of mallards in Florida is stopped, mallard
genetic introgression into the mottled duck population will continue to
increase, possibly to the demise of Florida’s
mottled duck.
II.
Plan
A.
Objective:
Develop techniques to identify hybrids
1.
Strategy:
Develop technique to distinguish hybrids by genotype
a)
Task – Collect additional tissue
samples from mallards and hybrids
b)
Task –
Contract with genetics lab to develop technique
2.
Strategy: Develop technique to
distinguish hybrids by phenotypic characteristics
a)
Task – Use genetic technique to
identify known hybrids and identify plumage characteristics that
distinguish hybrids from either species
b)
Task – Develop key or field guide
to identifying hybrids by phenotypic characteristics for use during
banding and at hunter check stations
B.
Objective:
Assess proportion and distribution of hybrids in population
1.
Strategy:
Obtain current estimate of proportion of population that are
hybrids
2.
Strategy:
Identify geographic problem areas
3.
Strategy:
Implement periodic sampling of population to measure temporal change in
hybridization rate
a)
Task– Obtain tissue from museum
specimens and compare to current genetic makeup of mottled duck
population to measure any previous temporal change toward more
mallard-type genes
b)
Task – Design sampling scheme
c)
Task – Periodically sample
population
C.
Objective:
Identify and implement mechanisms to reduce hybridization
1.
Strategy:
Learn about the sources of mallards being released
a)
Task – Conduct survey of
farm-and-feed-type of stores and pet stores
b)
Task – Conduct informal survey of
commercial mallard breeders
c)
Task – Investigate possible data
bases and other sources of information concerning the number of mallards
brought into the state, means of transport, and disposition
2.
Strategy:
Develop
and implement communications plan (i.e., marketing and public
relations strategy)
a)
Tasks – (See Attachment C,
Integrated Communications Plan)
3.
Strategy:
Recommend rule changes to curb mallard releases
a)
Task – Prohibit release of
mallards on private hunting preserves
b)
Task – Review other
potential
regulatory mechanisms for addressing the problem
4.
Strategy: Investigate animals to be purchased for pets
and for ornamental purpose as alternatives
a) Task - investigate feasibility of
producing sterile mallards
b) Task
b)
Task – Investigate
feasibility of developing a supply of
captive-reared mottled ducks
5.
Strategy:
Facilitate direct control of mallard populations where feasible
a)
Task – Obtain from U.S. Fish and
Wildlife Service a permit to allow for lethal control
b)
Task – Develop strategy for
implementing permit
c)
Task – Implement permit
6.
Strategy:
Provide for the release of captive-reared mottled ducks on private
hunting preserves
a)
Task – Recommend rule
change to establish guidelines for release of mottled ducks from private
hunting preserves
b)
Task – Support industry
efforts to have federal regulations changed that restrict release of
captive-reared mottled ducks on private hunting preserves
c)
Task – Assess requirements for
establishing a captive program
d)
Task – Permit the capture and
keeping of wild mottled ducks or their eggs
e)
Task – Assist as necessary and
feasible with taking wild mottled ducks or eggs to establish captive
flock and, if necessary, obtain pertinent federal permit
f)
Task – Ensure genetic purity of
brood stock through regulation and inspection
g)
Task – Ensure to the extent
possible through regulation and enforcement that released birds are
disease-free
h)
Task– Assess impact of
captive-reared and released mottled ducks on wild mottled duck
population and monitoring programs
(1)
Require that preserves provide daily records of bird numbers
released and harvested
(2)
Estimate annual and seasonal (post-season until annual mottled duck
population monitoring) survival rates of released birds
(3)
Periodically estimate band reporting rates for wild mottled ducks
to assess potential of mottled duck releases to bias band recovery
data.
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