These modeling results must be linked to field research to resolve what
human activities cause the kinds and frequencies of disturbance that we
considered. Generally, if the primary management goal is maintaining wolf
numbers, then management actions should focus on protecting the integrity
of territories for sustainable use by breeding pairs rather than protecting
individual animals from human harassment. This quantitative analysis did
not address alternative and largely implicit goals of protecting wolves from
any behavioral changes caused by human disturbance or displacement
within a natural ecosystem (e.g., Forbes and Theberge 1996).
2.3.5 Vasectomy for Wolf Control
In the late 1990s, recovering wolf populations in Minnesota, Wisconsin, and
Michigan prompted state management agencies to consider strategies to
control wolf population growth. Population control may be necessary where
wolves colonize areas close to human settlement and conflict with other
valued land uses. Because killing wolves to control population size is not
acceptable to many people, vasectomy was proposed as a nonlethal control
strategy that might have wider public acceptance.
Vasectomy involves sterilizing a male wolf in the field with chemical
sclerosing agents to harden and block the sperm tract without affecting
hormones. The primary reason that vasectomy might be practical for controlling wolves is that single pairs of adult wolves occupy large territories
(150 to 180 km
2 in the western Great Lakes region) and thus control the
number of offspring over a large area for 5 years or more. Pairs that fail to
produce young because of vasectomies or natural reasons may continue to
hold territories for years (Hayes 1995; Mech et al. 1996). Thus, by sterilizing the breeding male in a territory, theoretically a manager could restrict
the number of wolves in that large area for years.
To evaluate and compare wolf control strategies, Haight and Mech (1997)
used the wolf population model to predict the effects of both vasectomy
and removal on the trends of a small, disjunct population. The hypothetical population occupied a landscape composed of a maximum of 16 wolf
territories equally divided between core (20% annual mortality rate) and
peripheral (35% annual mortality rate) ranges. The wolf management
strategies included periodic sterilization of all breeding males, sterilization
of fertile males caught in a random-trapping design, and various wolf
removal designs. Of particular interest was the effect of immigration from
neighboring unmanaged populations on the performance of the strategies
in the managed population.
Simulations suggested that the effects of wolf vasectomy in a small,
disjunct population are strongly related to the level of annual immigration.
With low immigration, periodic sterilization reduced pup production and
resulted in lower rates of territory recolonization. Consequently, average
pack size, number of packs, and population size were significantly less than
36
Jean Fitts Cochrane et al.
human activities cause the kinds and frequencies of disturbance that we
considered. Generally, if the primary management goal is maintaining wolf
numbers, then management actions should focus on protecting the integrity
of territories for sustainable use by breeding pairs rather than protecting
individual animals from human harassment. This quantitative analysis did
not address alternative and largely implicit goals of protecting wolves from
any behavioral changes caused by human disturbance or displacement
within a natural ecosystem (e.g., Forbes and Theberge 1996).
2.3.5 Vasectomy for Wolf Control
In the late 1990s, recovering wolf populations in Minnesota, Wisconsin, and
Michigan prompted state management agencies to consider strategies to
control wolf population growth. Population control may be necessary where
wolves colonize areas close to human settlement and conflict with other
valued land uses. Because killing wolves to control population size is not
acceptable to many people, vasectomy was proposed as a nonlethal control
strategy that might have wider public acceptance.
Vasectomy involves sterilizing a male wolf in the field with chemical
sclerosing agents to harden and block the sperm tract without affecting
hormones. The primary reason that vasectomy might be practical for controlling wolves is that single pairs of adult wolves occupy large territories
(150 to 180 km
2 in the western Great Lakes region) and thus control the
number of offspring over a large area for 5 years or more. Pairs that fail to
produce young because of vasectomies or natural reasons may continue to
hold territories for years (Hayes 1995; Mech et al. 1996). Thus, by sterilizing the breeding male in a territory, theoretically a manager could restrict
the number of wolves in that large area for years.
To evaluate and compare wolf control strategies, Haight and Mech (1997)
used the wolf population model to predict the effects of both vasectomy
and removal on the trends of a small, disjunct population. The hypothetical population occupied a landscape composed of a maximum of 16 wolf
territories equally divided between core (20% annual mortality rate) and
peripheral (35% annual mortality rate) ranges. The wolf management
strategies included periodic sterilization of all breeding males, sterilization
of fertile males caught in a random-trapping design, and various wolf
removal designs. Of particular interest was the effect of immigration from
neighboring unmanaged populations on the performance of the strategies
in the managed population.
Simulations suggested that the effects of wolf vasectomy in a small,
disjunct population are strongly related to the level of annual immigration.
With low immigration, periodic sterilization reduced pup production and
resulted in lower rates of territory recolonization. Consequently, average
pack size, number of packs, and population size were significantly less than
36
Jean Fitts Cochrane et al.