(U.S. Department of the Interior 1996), custom models have been built to
predict population trends and to help establish recovery targets.
Demographic models have also been developed to address specific
questions about the management of an endangered species that arise
during the implementation of the recovery plan. These questions usually
relate to potential threats, such as habitat destruction or any other natural
or man-made factor that might affect the continued existence of the species.
For example, Lamberson et al. (1994) analyzed the impacts of habitat patch
size and spacing on population viability and thereby helped direct the
design of forest reserves for the endangered Northern spotted owl (Strix
occidentalis caurina).
The modeling projects in this chapter address specific management questions that were raised during the recovery of the gray wolf. The questions
involved predicting the impacts of human-caused mortality, changing
regional environmental conditions, and disturbance on the persistence of
small wolf populations. In addition, the questions involved predicting the
relative performance of different strategies for controlling wolf populations. Our approach involved constructing a relatively simple population
model that was consistent with the current level of understanding of wolf
dynamics and was customized to address specific management questions.
Our model included the basic processes of wolf demography (birth,
survival, and dispersal) and the social structure of a wolf population. We
used the model to simulate population impacts of changes in demographic
parameters, and we used model predictions to infer how changes in management activities and environmental processes might affect wolf populations. While we used the same basic population model for all the projects,
we modified the model and developed distinct simulation experiments to
address each question separately. Our approach differs from other gray wolf
modeling projects, such as long-term PVA using commercial software [e.g.,
Rolley et al. (1999); Kelly et al. (1999); Ewins et al. (2000)] and analytical
wolf-prey models [e.g., Walters et al. (1981); Boyce (1992b)], which do not
address the population effects of wolf social structure.
2.2 Wolf Biology and Recovery Status
Wolves live in packs and defend exclusive territories (Mech 1970).
Generally, packs are family groups consisting of one dominant breeding
pair and their offspring (Mech 1970). In the western Great Lakes region,
midwinter pack size averages 4 to 8 wolves, about half of which are pups
(Fuller 1989). Because of territoriality, regional population density and
reproductive rate depend on the number and size of territories. Wolves are
not habitat specific, instead they can live wherever they find enough to eat
(primarily ungulates), provided killing by humans or disease is not excessive (Fuller 1995; Mech 1995). Population turnover rates are naturally high,
24
Jean Fitts Cochrane et al.
predict population trends and to help establish recovery targets.
Demographic models have also been developed to address specific
questions about the management of an endangered species that arise
during the implementation of the recovery plan. These questions usually
relate to potential threats, such as habitat destruction or any other natural
or man-made factor that might affect the continued existence of the species.
For example, Lamberson et al. (1994) analyzed the impacts of habitat patch
size and spacing on population viability and thereby helped direct the
design of forest reserves for the endangered Northern spotted owl (Strix
occidentalis caurina).
The modeling projects in this chapter address specific management questions that were raised during the recovery of the gray wolf. The questions
involved predicting the impacts of human-caused mortality, changing
regional environmental conditions, and disturbance on the persistence of
small wolf populations. In addition, the questions involved predicting the
relative performance of different strategies for controlling wolf populations. Our approach involved constructing a relatively simple population
model that was consistent with the current level of understanding of wolf
dynamics and was customized to address specific management questions.
Our model included the basic processes of wolf demography (birth,
survival, and dispersal) and the social structure of a wolf population. We
used the model to simulate population impacts of changes in demographic
parameters, and we used model predictions to infer how changes in management activities and environmental processes might affect wolf populations. While we used the same basic population model for all the projects,
we modified the model and developed distinct simulation experiments to
address each question separately. Our approach differs from other gray wolf
modeling projects, such as long-term PVA using commercial software [e.g.,
Rolley et al. (1999); Kelly et al. (1999); Ewins et al. (2000)] and analytical
wolf-prey models [e.g., Walters et al. (1981); Boyce (1992b)], which do not
address the population effects of wolf social structure.
2.2 Wolf Biology and Recovery Status
Wolves live in packs and defend exclusive territories (Mech 1970).
Generally, packs are family groups consisting of one dominant breeding
pair and their offspring (Mech 1970). In the western Great Lakes region,
midwinter pack size averages 4 to 8 wolves, about half of which are pups
(Fuller 1989). Because of territoriality, regional population density and
reproductive rate depend on the number and size of territories. Wolves are
not habitat specific, instead they can live wherever they find enough to eat
(primarily ungulates), provided killing by humans or disease is not excessive (Fuller 1995; Mech 1995). Population turnover rates are naturally high,
24
Jean Fitts Cochrane et al.