Block & Bridle Annual 1959-1960

President Roger Wehrbein Vice President Ted Klug Secretary George B. O'Neal Treasurer Ralph Hazen Marshal Bud Reece Historian Tom Kraeger Co-Historian John Zauha Ag. Executive Representative Larry Williams Faculty Advisor Dr. E. B. Peo, Jr. George Ahlschwede Richard Hahn Henry Beel Ralph Hazen Gary Briggs Gary Heineman Leslie Cook Max Hauser Richard Eberspacher Buce Jameson Russ Edeal Leon Janovy William Ehresman Alan Jorgensen Rolland Eubanks John Joyner Mickey Evertson Marshall Jurgens Jesse Felker Ron Kahle Mylon Filkins Donald Kavan Richard Frahm Max Keasling Roger French Ronald Kennedy Angus Garey Ted Klug Ed Gates Herb Kraeger Gerald Gogan Tom Kraeger Gerald Goold Fernando Lagos Jay Graf Gerald Lamberson Lloyd Langemeier Ralph Langemeier Gerald Loseke Donald Meiergerd Lowell Minert John Oeltjen George B. O'Neal Don Ormesher Larry Ott Bud Reece Ron Sabatka Keith Smith Ronald Smith Donn Simonson Daryl Starr Galen Stevens Eugene Turdy Ernest Thayer Charles Thompson Jerry Thompson Eli Thomssen William Watkins Allen Trumble Robert Weber Lawrence Turner Dan Wehrbein Reginald Turner Roger Wehrbein Vance Uden Dick White Max Waldo Billy Williams Blair Williams Larry Williams D. Patrick Wright John Zauha

Killer Whales and Marine Mammal Trends in The North Pacific—A Re-Examination of Evidence for Sequential Megafauna Collapse and the Prey-Switching Hypothesis

Springer et al. (2003) contend that sequential declines occurred in North Pacific populations of harbor and fur seals, Steller sea lions, and sea otters. They hypothesize that these were due to increased predation by killer whales, when industrial whaling’s removal of large whales as a supposed primary food source precipitated a prey switch. Using a regional approach, we reexamined whale catch data, killer whale predation observations, and the current biomass and trends of potential prey, and found little support for the prey-switching hypothesis. Large whale biomass in the Bering Sea did not decline as much as suggested by Springer et al., and much of the reduction occurred 50–100 yr ago, well before the declines of pinnipeds and sea otters began; thus, the need to switch prey starting in the 1970s is doubtful. With the sole exception that the sea otter decline followed the decline of pinnipeds, the reported declines were not in fact sequential. Given this, it is unlikely that a sequential megafaunal collapse from whales to sea otters occurred. The spatial and temporal patterns of pinniped and sea otter population trends are more complex than Springer et al. suggest, and are often inconsistent with their hypothesis. Populations remained stable or increased in many areas, despite extensive historical whaling and high killer whale abundance. Furthermore, observed killer whale predation has largely involved pinnipeds and small cetaceans; there is little evidence that large whales were ever a major prey item in high latitudes. Small cetaceans (ignored by Springer et al.) were likely abundant throughout the period. Overall, we suggest that the Springer et al. hypothesis represents a misleading and simplistic view of events and trophic relationships within this complex marine ecosystem.

Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions

Over the past three decades, the decline and altered spatial distribution of the western stock of Steller sea lions (Eumetopias jubatus) in Alaska have been attributed to changes in the distribution or abundance of their prey due to the cumulative effects of fisheries and environmental perturbations. During this period, dietary prey occurrence and diet diversity were related to population decline within metapopulation regions of the western stock of Steller sea lions, suggesting that environmental conditions may be variable among regions. The objective of this study, therefore, was to examine regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions within the context of recent measures of diet diversity and population trajectories. Habitat use was assessed by deploying satellite-depth recorders and satellite relay data loggers on juvenile Steller sea lions (n = 45) over a five-year period (2000–2004) within four regions of the western stock, including the western, central, and eastern Aleutian Islands, and central Gulf of Alaska. Areas used by sea lions during summer months (June, July, and August) were demarcated using satellite telemetry data and characterized by environmental variables (sea surface temperature [SST] and chlorophyll a [chl a]), which possibly serve as proxies for environmental processes or prey. Spatial patterns of SST diversity and Steller sea lion population trends among regions were fairly consistent with trends reported for diet studies, possibly indicating a link between environmental diversity, prey diversity, and distribution or abundance of Steller sea lions. Overall, maximum spatial heterogeneity coupled with minimal temporal variability of SST appeared to be beneficial for Steller sea lions. In contrast, these patterns were not consistent for chl a, and there appeared to be an ecological threshold. Understanding how Steller sea lions respond to measures of environmental heterogeneity will ultimately be useful for implementing ecosystem management approaches and developing additional conservation strategies.

Comparison of Endocrine Response to Stress Between Captive-Raised and Wild-Caught Bighorn Sheep

Stress hormones in Rocky Mountain bighorn sheep (Ovis canadensis canadensis), produced in response to environmental changes, road development, or high population density, may impact their immune systems to a threshold level that predisposes them to periodic, large-scale mortality. We compared the stress response to a novel environmental situation and repeated handling between bighorn sheep born and raised in captivity (CR) and bighorn sheep born in the wild (WC) and brought into captivity. We measured plasma epinephrine, norepinephrine, cortisol, and fecal glucocorticoid metabolites (FGM). Three weeks after each group’s arrival we used a one-time drop-net event to elicit an acute stress response, and we collected blood samples from each sheep over 35 minutes, as well as one fecal sample. We collected blood and fecal samples from both groups on 7 other occasions over the subsequent 6 months. We also collected fecal samples from the pen at approximately 24-hour intervals for 3 days following every handling event to monitor the stress response to handling. We found that CR sheep had a stronger autonomic nervous system response than WC sheep, as measured by epinephrine and norepinephrine levels, but we found a very similar hypothalamic–pituitary–adrenal axis (HPA) response, measured by cortisol levels, to the acute stress event of a drop-net restraint. We also found that once the WC sheep had acclimated, as indicated by the return to the initial baseline FGM levels within 12 weeks, the CR and WC groups’ HPA responses to sampling events were not significantly different from one another. Fecal samples can provide a noninvasive mechanism for managers to monitor baseline FGM for a given herd. Using long-term monitoring of FGM rather than values from a single point in time may allow managers to correlate these levels to outside influences on the herd and better understand the impacts of management changes, population density, or increased human developments on the health of the sheep population.

Review of issues concerning the use of reproductive inhibitors, with particular emphasis on resolving human-wildlife conflicts in North America

This manuscript provides an overview of past wildlife contraception efforts and discusses the current state of research. Two fertility control agents, an avian reproductive inhibitor containing the active ingredient nicarbazin and an immunocontraceptive vaccine, have received regulatory approval with the Environmental Protection Agency and are commercially available in the USA. OvoControl G Contraceptive Bait for Canada Geese and Ovo Control for pigeons are delivered as oral baits. An injectable immunocontraceptive vaccine (GonaCon Immunocontraceptive Vaccine) was registered with the Environmental Protection Agency for use in female white-tailed deer in September 2009. An injectable product (GonaCon Immunocontraceptive Vaccine) is registered for use in female white-tailed deer. Both products are labeled for use in urban/suburban areas where these species are overabundant. Several other compounds are currently being tested for use in wildlife in the USA, Europe, Australia and New Zealand that could have promise in the future. The development and use of reproductive inhibitors for resolving human–wildlife conflicts will depend on a number of factors, including meeting the requirements of regulatory agencies for use in the environment and on the biological and economical feasibility of their use. Use will also be dependent on health and safety issues and on public acceptance of the techniques.

Development of Nicarbazin as a Reproductive Inhibitor for Resident Canada Geese

Expanding populations of resident Canada geese that remain in suburban and urban areas year-round often result in increased conflicts with humans. Non-lethal and humane means are needed for managing the size of Canada goose flocks residing near or on airports, golf courses, industrial parks, government sites, and city parks. A side effect of nicarbazin, a veterinary drug used to control coccidiosis in chickens, is decreased egg production and hatching. Exploiting this side effect, studies of nicarbazin for reducing the hatchability of eggs from Canada geese were conducted. An initial study in Coturnix quail verified reduction in hatchability in a species other than chickens. Because plasma nicarbazin was not routinely measured, a study in chickens was conducted to determine the relationship between plasma and egg nicarbazin. A comparative study in chickens, mallards, and Canada geese showed that nicarbazin absorption was lowest in geese. Studies in both penned and wild Canada geese showed that reduction in hatchability was possible but neither study used bait suitable for general field application. Bait development led to the OvoControl-G® (Innolytics LLC) bait, which resulted in reduction in hatchability of 51% at treated sites compared to control sites in the field. Previous studies showed that nicarbazin is practically non-toxic and is environmentally friendly; timing and management of baiting will minimize non-target hazards. OvoControl-G® 2500 ppm nicarbazin bait is recommended for incorporation into a comprehensive management plan as a reproductive inhibitor for use in controlling resident Canada goose flock sizes.