The 0.005% diphacinone rodenticide pellets used in this study have been proposed for use in field applications to control introduced rodents on conservation lands in the state of Hawaii. Introduced rodents (especially Rattus spp.) cause a wide array of conservation problems in the Hawaiian Islands and on other islands. We assessed the acceptability and toxicity (should the pellets be consumed) of two rodenticide baits to Canada geese, a surrogate species for the endangered Hawaiian goose. Based on these trials with captive, wild Canada geese, it appears that neither the whole nor the chopped (to simulate broken or weathered baits) pellets pose a significant risk to the Hawaiian goose, a species considerably smaller than the Canada goose. The pellets (whole or chopped) were not accepted by the Canada geese during this study despite their having only a small amount of green grass sod as an alternative food. There were no mortalities of geese during the feeding trials and all geese remained healthy, based on body weights and packed blood cell volumes. The endangered status of the Hawaiian goose precluded using it as the target study species.

Pocket gophers cause substantial damage in a number of western states. A better knowledge of their forage preferences and the nutritional attributes of those preferences could result in better management of populations and reduction of damage. We live-trapped northern pocket gophers in northern Idaho and brought them into captivity at Washington State University, Pullman, WA. We tested their preferences for several species of forbs, grasses, and woody species. Preferences varied in all plant groups. Forbs were highly preferred in early summer but dropped off in late summer, perhaps due to senescence. However, preference for woody species increased in late summer and winter. There were few consistent correlations between forage preferences and nutri-tional levels of those forages. However, in one late summer trial, gophers did seem to prefer forage species high in crude protein and apparent digestible protein. This suggests the importance of protein levels in foods of gophers as has been found with other wildlife species and situations.

The deer mouse is the most widely distributed and abundant small mammal in North America. They use a wide array of habitats, are very adaptable, and have a high reproductive potential. They play a number of roles in ecosystems, but can cause damage to orchards, forests, agriculture crops, and rangelands primarily through seed and newly-emerged seedling consumption. They also cause damage similar to house mice when they occupy buildings or other structures. Deer mice are important components in disease transmission especially of hantaviruses and Lyme disease. Damage reduction methods generally involve lethal control to reduce numbers using rodenticides and traps. Improvements in control methods are needed, especially in some agricultural crop types.

The house mouse is probably the most widespread invasive mammalian species, being ubiquitous worldwide. In commensal situations, they are known mainly for property damage, for consumption and contamination of stored foods, as a noise/sanitation/odor nuisance, and as a vector of some diseases. In some field settings, they also cause considerable damage to field crops and to natural resources, such as when introduced to islands. We rely heavily upon sanitation, rodent-proofing, capture devices, and rodenticides to control populations and reduce damage. However, a number of situations exist whereby these traditional methods are not adequate or appropriate: crop damage during “mouse plagues” in Australia, livestock feed consumption and contamination and disease hazards in poultry and animal facilities in the U.S., and natural resource damage on small islands. In this review, challenges and some potential solutions to house mouse management are presented, including genetic resistance to anticoagulants, the effectiveness of baits given abundant food resources, the re-invasion problem and need for perimeter strategies, efforts with fertility control, and the need for effective multi-capture trap devices. In difficult situations, an IPM strategy that incorporates a combination of methods closely integrated with land uses and management practices is necessary.

Burrowing rodents, such as pocket gophers (Geomyidae) and voles (Microtus spp.), often cause extensive damage in agricultural, urban/residential, and natural resource areas. Effective management of burrowing rodents typically follows an integrated pest management (IPM) approach that involves a number of tools including rodenticide baiting. However, some of the more commonly used rodenticides have limitations including the development of resistance (e.g., first-generation anticoagulants and strychnine), secondary-toxicity concerns (e.g., anticoagulants), and limited availability (e.g., strychnine). Initial research with combination cholecalciferol plus anticoagulant rodenticides has indicated potential promise at overcoming some of these limitations. As such, we tested the efficacy of several different cholecalciferol plus anticoagulant combinations to determine if they were efficacious in managing Botta’s pocket gophers and California voles in both cage and field trials. Two-choice cage trials for California voles indicated that both pelletized (0.03% cholecalciferol plus 0.005% diphacinone, efficacy = 80%) and bract baits (0.012% cholecalciferol plus 0.002% diphacinone, efficacy = 70%) containing cholecalciferol plus diphacinone (C+D) were efficacious. Further field testing indicated that C+D-coated bract baits (0.014% cholecalciferol plus 0.003% diphacinone) were highly efficacious for vole control (efficacy = 85%), while pelletized baits were less promising (efficacy = 60%). Cage trials indicated that both C+D (0.03% cholecalciferol plus 0.005% diphacinone, efficacy = 80%) and two concentrations of cholecalciferol plus brodifacoum (C+B1 = 0.015% cholecalciferol plus 0.0025% brodifacoum, efficacy = 100%; C+B2 = 0.03% cholecalciferol plus 0.0025% brodifacoum, efficacy = 100%) pelleted baits showed promise as pocket gopher rodenticides. Further field testing of C+D and C+B2 resulted in efficacy significantly >70% (efficacy = 83% and 75%, respectively), although strychnine (0.5%) applications were the most efficacious (efficacy = 100%). Collectively, these results suggest that cholecalciferol plus anticoagulant rodenticides are effective options for managing burrowing rodent populations; they deserve further consideration for registration against these potentially damaging species.

Monitoring populations of problem species is an essential component for integrated damage reduction programs. Tracking population size through time and space helps define the potential magnitude and geographical extent of damage. Population size at an early stage of a crop cycle can serve as a predictor of damage levels later on, indicating whether control is necessary or what forms would be economically optimal. The ability to monitor for population change also permits assessment of the efficacy of the control methods for reducing numbers of a pest species. Methods for quantifying population levels can be as diverse as the number of subject species, the objectives of an IPM program, and whether direct estimates or indices of population parameters are required. Often, indirect methods involving counts of tracks, burrows, droppings, or food removal are used. We review methods used for a variety of wildlife species, examine the desirable characteristics for useful monitoring methods, and describe some of our current research on indexing methods.

The 2½-day Colorado Front Range Prairie Dog Technical Workshop was held in Fort Collins, Colorado, February 27-March 1, 2001. The workshop attracted about 250 attendees, mostly government personnel. Black-tailed prairie dogs (Cynomys ludovicianus) present numerous challenges to landowners and resource managers because they are considered a rare and important ecosystem component, but at the same time they can cause various kinds of damage and pose a disease hazard to humans and their domestic animals. Invited speakers updated the participants on the topics of prairie dog biology and ecology, legal status and distribution, socio-economic issues, management techniques and strategies, and current research. Special topics such as plague management and black-footed ferret re-introductions were also addressed. Several panel discussions on management challenges and options were held. Various perspectives were presented and there was considerable interaction on these volatile issues. There was a field trip to local prairie dog colonies to view and discuss conflicts and management options. In this paper, we summarize some of the key topics and perspectives brought up at the Workshop, in order to provide a broad synopsis of this highly contentious arena of human-wildlife conflict.

The Azores are Portuguese islands in the North Atlantic Ocean. The culture is very agrarian with a large cattle industry. Unfortunately, there is a chronic leptospirosis problem within the people, livestock, companion animals, and wildlife of the Azores. Introduced rodents play a significant role as maintenance hosts of this disease. We review the situation and make recommendations for reducing the occurrence and hazard of leptospirosis in the Azores. Areas addressed include the need for a better understanding of the epidemiology of the disease and the role of rodents, development of an effective rodent control program, improvements in farm practices and animal husbandry, and improvements in the Azores infrastructure to effectively reduce the leptospirosis hazard.

Invasive vertebrates have had significant effects on native species, ecosystem processes, human health and economies around the world for more than 200 years. However, in the last 30 years, the breadth and impact of invasive species has accelerated with the growth and integration of high speed transportation networks. The effects of many non-native species are often difficult to predict prior to establishment. Current efforts to manage invasive species can be broken into the areas of prevention of introduction and detection of incipient populations, documentation of impacts, and development and implementation of management tools. We address various aspects of these areas under the broad headings of 1) invasiveness and pathways, and 2) impacts, managements, and challenges. One of the biggest challenges of invasive species management is the lack of interest and resources to manage species before they are established. Hence, few tools exist to manage populations once a population is established. As such, much of the focus of current research is dedicated to identifying the impact of species and the development of management tools. Further, these new tools must not only be effective but also adaptable to the ever changing dynamics of the economic, social, and ecological aspects of the locality invaded. The symposia at this conference on various invasive vertebrates highlight both successful and unsuccessful management efforts, investigations to determine the full impact of invasive species, and the development of novel control techniques.

In many cases, the control or eradication of invasive house mice has been problematic using rodenticide products that are currently registered. Our investigations using 12 commercial formulations confirmed that premise. In contrast, 11 of 12 of those commercial formulations were effective against Norway rats. Hence, we investigated 7 new rodenticide formulations to identify more effective alternative rodenticides (different formulation and/or different active ingredients). Several of the new formulations of rodenticides and new active ingredients were found to be relatively efficacious (³70% mortality) and may warrant further investigation as potential control methods for invasive house mice. Additionally, a 2-active ingredient rodenticide, none of which are currently registered in the U.S., showed promise as a new house mouse control tool, and these may have some advantages over currently registered invasive house mouse rodenticides. Field trials with some of these new formulations are recommended as a next step in the research and pesticide registration process.