The management of free-roaming, feral horse (Equus caballus) populations in the western United St... more The management of free-roaming, feral horse (Equus caballus) populations in the western United States is a contentious and challenging issue. Between 2008 and 2014, 1,873 individual horses from a closed population in the northern Great Basin, USA were captured, uniquely marked, and were either removed for private adoption or had permanent fertility control treatments (i.e., vasectomy or ovariectomy) applied prior to release. We derived the annual population size, growth rate, and the number of horses by sex and age by using the horse's estimated age at first capture to infer its age during each year it was part of the population. Estimates of population size from 2 aerial survey techniques averaged within 5.3%–9.6% of derived population estimates. The overall survival (i.e., recapture) rate for individual horses was 88% for individuals released back into the population between 2009 and 2012. Treated horses maintained group associations and there were no differences between survival rates for released females or males that received fertility control treatment, compared to animals released without treatment. The application of combined fertility control efforts resulted in a decline in the population-level annual foaling rate from >20% to <4% within 4 years. Maintaining a proportion of a population as permanently non-reproducing has the potential to safely maintain free-roaming horse herds at desired management levels.
Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians, 2015
Free-roaming horse ( Equus caballus ) management is a complex issue incorporating social, economi... more Free-roaming horse ( Equus caballus ) management is a complex issue incorporating social, economic, emotional, political, and environmental factors. Currently, few proven field techniques exist for managing free-roaming horse population growth, which can reach 20-25% annually. Although there are several strategies available for sterilizing mares when managing free-roaming horse populations, surgical vasectomy is the only method used in the field for stallions. Some managers believe that surgically vasectomizing dominant stallions would have significant effects on reducing horse populations. However, sterilizing only dominant harem stallions results in a relatively modest reduction in population growth as substantial reproduction may occur even when 100% of the dominant harem stallions are sterilized if other males perform as little as 10% of the breeding. The overall goal of the current project was to evaluate the efficacy of a novel nonsurgical method for sterilizing free-roaming h...
American black bear (Ursus americanus) feeding damage to conifer stands can result in substantial... more American black bear (Ursus americanus) feeding damage to conifer stands can result in substantial economic losses in the Pacific Northwest. However, little is known about which sex and age classes of bears cause the most damage and the effectiveness of current control methods. We examined the frequency, intensity, and total conifer damage by radio-monitoring 13 male and 9 female black bears from 1998 to 1999 to determine which sex and age classes caused the most damage. We also examined which sex and age classes were affected by control measures (hunting) to determine the efficacy of management actions. Females were associated with greater frequency (P = 0.078), intensity (P = 0.037), and total conifer damage (P = 0.015) than males. Adult females damaged more trees than other sex and age classes combined (P = 0.092). Adult males comprised the majority of bears removed by hunting (66%) but caused only 11% of total damage. Current damage control measures do not seem to be as effective...
Brown bear (Ursus arctos) population size correlates with density of high-quality food resources.... more Brown bear (Ursus arctos) population size correlates with density of high-quality food resources. We report on a ten-year study (1993 - 2003) of brown bear nutritional ecology in southwestern Alaska during which changes in resource availability and density occurred. The diets of 21 female bears captured multiple years were characterized by stable isotope analysis (delta13C, delta15N, and delta34S) of guard hairs and putative diet items, followed by application of a Bayesian mixing model to derive assimilated diet estimates. Diet estimates were subsequently used to characterize individual-level resource specialization. Over the entire study period, salmon accounted for the highest proportion of bear diets (42.1%), followed by berries (24.5%), mammals (13.5%), freshwater fish (11.2%), and other plant matter (8.7%). The average salmon contribution to bear diets declined significantly from 48% to 34% following a precipitous reduction in salmon escapement mid-way through the study, after...
Brown bear (Ursus arctos) population density was estimated for a 21,178 km 2 study area in southw... more Brown bear (Ursus arctos) population density was estimated for a 21,178 km 2 study area in southwest Alaska. Estimates were obtained using an aerial line transect method that allows for peak detection to be both off the transect line and< 100%. Data collection required five small aircraft with two-person crews. Surveys were flown in 10-day windows to capture the period after den emergence but prior to full green-up. Surveys were flown in two consecutive years in order to detect sufficient bear groups to support the ...
The management of free-roaming, feral horse (Equus caballus) populations in the western United St... more The management of free-roaming, feral horse (Equus caballus) populations in the western United States is a contentious and challenging issue. Between 2008 and 2014, 1,873 individual horses from a closed population in the northern Great Basin, USA were captured, uniquely marked, and were either removed for private adoption or had permanent fertility control treatments (i.e., vasectomy or ovariectomy) applied prior to release. We derived the annual population size, growth rate, and the number of horses by sex and age by using the horse's estimated age at first capture to infer its age during each year it was part of the population. Estimates of population size from 2 aerial survey techniques averaged within 5.3%–9.6% of derived population estimates. The overall survival (i.e., recapture) rate for individual horses was 88% for individuals released back into the population between 2009 and 2012. Treated horses maintained group associations and there were no differences between survival rates for released females or males that received fertility control treatment, compared to animals released without treatment. The application of combined fertility control efforts resulted in a decline in the population-level annual foaling rate from >20% to <4% within 4 years. Maintaining a proportion of a population as permanently non-reproducing has the potential to safely maintain free-roaming horse herds at desired management levels.
Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians, 2015
Free-roaming horse ( Equus caballus ) management is a complex issue incorporating social, economi... more Free-roaming horse ( Equus caballus ) management is a complex issue incorporating social, economic, emotional, political, and environmental factors. Currently, few proven field techniques exist for managing free-roaming horse population growth, which can reach 20-25% annually. Although there are several strategies available for sterilizing mares when managing free-roaming horse populations, surgical vasectomy is the only method used in the field for stallions. Some managers believe that surgically vasectomizing dominant stallions would have significant effects on reducing horse populations. However, sterilizing only dominant harem stallions results in a relatively modest reduction in population growth as substantial reproduction may occur even when 100% of the dominant harem stallions are sterilized if other males perform as little as 10% of the breeding. The overall goal of the current project was to evaluate the efficacy of a novel nonsurgical method for sterilizing free-roaming h...
American black bear (Ursus americanus) feeding damage to conifer stands can result in substantial... more American black bear (Ursus americanus) feeding damage to conifer stands can result in substantial economic losses in the Pacific Northwest. However, little is known about which sex and age classes of bears cause the most damage and the effectiveness of current control methods. We examined the frequency, intensity, and total conifer damage by radio-monitoring 13 male and 9 female black bears from 1998 to 1999 to determine which sex and age classes caused the most damage. We also examined which sex and age classes were affected by control measures (hunting) to determine the efficacy of management actions. Females were associated with greater frequency (P = 0.078), intensity (P = 0.037), and total conifer damage (P = 0.015) than males. Adult females damaged more trees than other sex and age classes combined (P = 0.092). Adult males comprised the majority of bears removed by hunting (66%) but caused only 11% of total damage. Current damage control measures do not seem to be as effective...
Brown bear (Ursus arctos) population size correlates with density of high-quality food resources.... more Brown bear (Ursus arctos) population size correlates with density of high-quality food resources. We report on a ten-year study (1993 - 2003) of brown bear nutritional ecology in southwestern Alaska during which changes in resource availability and density occurred. The diets of 21 female bears captured multiple years were characterized by stable isotope analysis (delta13C, delta15N, and delta34S) of guard hairs and putative diet items, followed by application of a Bayesian mixing model to derive assimilated diet estimates. Diet estimates were subsequently used to characterize individual-level resource specialization. Over the entire study period, salmon accounted for the highest proportion of bear diets (42.1%), followed by berries (24.5%), mammals (13.5%), freshwater fish (11.2%), and other plant matter (8.7%). The average salmon contribution to bear diets declined significantly from 48% to 34% following a precipitous reduction in salmon escapement mid-way through the study, after...
Brown bear (Ursus arctos) population density was estimated for a 21,178 km 2 study area in southw... more Brown bear (Ursus arctos) population density was estimated for a 21,178 km 2 study area in southwest Alaska. Estimates were obtained using an aerial line transect method that allows for peak detection to be both off the transect line and< 100%. Data collection required five small aircraft with two-person crews. Surveys were flown in 10-day windows to capture the period after den emergence but prior to full green-up. Surveys were flown in two consecutive years in order to detect sufficient bear groups to support the ...
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Papers by Gail H Collins