The interest in possessing ferrets as pets has given rise to controversy between the "rights" of the individual to own the pet of their choice and the concerns for protection of wildlife in California. An overview of the legislative history in California illustrates the state's attempts at protecting native wildlife species from exotic wild birds and animals. Concerns as to the potential threats associated with the legalization of ferrets in California are warranted in light of the wildlife damage resulting from the deliberate introduction of ferrets in New Zealand and the non-native red fox in California. A framework to assess risks involved with introducing non-native species that may impact native wildlife is needed.
Context In peri-urban environments, high availability of anthropogenic resources may result in relatively high abundances of some species, with potentially negative implications for other native biota. Effective management of such impacts requires understanding of the spatial ecology of problem species. However, home range and habitat use have not been described for the little raven (Corvus mellori), a superabundant native predator that occurs in urban and natural habitats, including those where threatened shorebirds breed. Aims The aim of this study was to provide basic information on little raven home range, habitat use and movements in a coastal peri-urban landscape. Methods Between October 2011 and January 2012 we radio-tracked 20 little ravens captured in a coastal wetland (near Melbourne, Australia). Key results Little ravens were highly mobile, moving up to 9.9 km in an hour (median = 2 km), and had large ranges: Minimum Convex Polygons were 1664–9989 ha (median = 3362 ha). Although most birds used both anthropogenic and natural habitats, some birds strongly selected for coastal wetland habitat. Birds used multiple roosts during the study period, most of which occurred in grassland (58.7%) or urban (22.3%) areas. Movement of up to 8.3 km (median = 2.2 km) between roosts during the night was also detected. Conclusions Ravens were highly mobile and used large home ranges and a variety of habitats, with habitat preferences varying between birds. Implications Considering the large home ranges and inter-individual variation in habitat preferences of little raven populations, localised management to reduce their impacts on breeding shorebirds is unlikely to be successful.
Accurate density estimates of rodents are frequently difficult or cost-prohibitive to determine. Thus, a number of techniques (track plates, monitoring blocks, chew cards/sticks, apple slice index, trapping) are often used to index rodent populations. Theoretically, the sensitivity of these indexing techniques could be improved if they applied continuous measurements rather than simple binary measurements (presence/absence). Development of a relative abundance technique that is simple to apply and sensitive to changes in population density is critical for the operational management of rodent pests. In addition to providing a quantitative measure of abundance with statistical parameters, an indexing technique that does not require handling of animals is important in consideration of potential disease issues (for example, hantavirus, arenavirus, etc.). We investigated track plates, chew cards and monitoring blocks and associated continuous measurement methods for calculating indices of rodent abundance. In laboratory and field settings, we tested their effectiveness in detecting different population densities of California meadow voles (Microtus californicus). Chew cards were poorly accepted by meadow voles in pen and field tests. However, track plates and monitoring blocks may provide useful tools for indexing meadow vole populations, and have application for other rodent species.
This paper provides historical background on the Office of Spill Prevention and Response (OSPR) and describes the functions and capabilities of the Hazing Group within OSPR with regard to protecting wildlife during oil spills. In response to the oil spill disasters of the tankers Exxon Valdez in Alaska and the American Trader in California, legislators in 1990 created OSPR within the California Department of Fish and Game and gave OSPR substantial authority to oversee spill clean-up, natural resource damage assessment activities, and wildlife protection activities. In view of the potential for high bird mortality during a spill event and the high costs for rehabilitation, OSPR established the Hazing Group with the goal of preventing birds from becoming exposed in the event of a spill. The primary responsibilities of the Hazing Group are to: 1) improve and maintain preparedness and hazing response capabilities for spill events, 2) obtain or provide training and training materials on hazing techniques and strategies, spill response procedures, and other related subjects both for wildlife hazing unit members and other appropriate OSPR responders, and 3) conduct and review research on wildlife hazing techniques and strategies appropriate for spill events. With regard to response capabilities, the Hazing Group is on call 24 hr/day, acquired and maintains an inventory of pyrotechnics and other hazing equipment, has a cargo trailer on stand-by loaded with equipment and supplies sufficient for several days, and assembled a collection of California coastline maps useful for response planning. Training required for Hazing Group personnel includes HAZWOPER certification with an annual refresher course. Other training includes an annual Incident Command System class and participation in drills and exercises. A hazing manual is under development as training material for Hazing Group and other OSPR personnel. The Hazing Group conducted a literature review of research on bird hazing techniques and produced an annotated bibliography on bird hazing techniques applicable to oil spills. As oil spills are relatively short-lived events, techniques with only short-term effectiveness may still be sufficient for hazing birds.
Abstract Context At some sites in southern Victoria, browsing pressure caused by high-density koala populations can result in defoliation of preferred browse trees. In extreme cases, this over-browsing can lead to widespread tree death and starvation of koalas. To reduce the potential for mortality of trees and koalas, a management strategy that includes fertility control of females and translocation of healthy individuals (male and female) has been adopted. AimsTo compare the short- to medium-term survival and body condition of koalas translocated from over-browsed habitat and released into unoccupied (or nearly so) habitat with that of koalas left in situ in compromised habitat. Methods We monitored survival and body condition of 36 translocated koalas for 4–5 months after translocation relative to that of a control group (24 animals) left in situ. Koalas were recaptured and body condition measured (as a scaled body-mass index) ~40 and 137 days after translocation. Additionally, GPS loggers were used to investigate patterns of koala movement. Key resultsSurvival rates of translocated koalas were not different from those of controls and females in both groups showed slightly higher survival rates than did males. After 137 days, control animals had lower scaled body mass, whereas translocated animals, after an initial reduction, had mostly regained, or increased their scaled body mass. Translocated females regained their original scaled body mass faster than did translocated males. Male koalas in both control and translocated groups had higher rates of movement than did females, and translocated koalas had slightly higher rates of movement than did control koalas. Translocated koalas moved farther from their release location than control koalas. ConclusionsOn the basis of the scaled body-mass index, translocated koalas fared better than those left in situ in compromised habitat, even though the density of koalas in the over-browsed habitat had been reduced by a wider salvage translocation program. The process used to identify potential release sites, including a spatial koala-habitat index, accurately predicted suitable koala habitat. ImplicationsThe current management strategy of translocating koalas out of over-browsed habitat is supported and could be more widely applied.
Abstract.Diphacinone and chlorophacinone, first-generation anticoagulant rodenticides, are frequently used for control of California ground squirrels (Spermophilus beecheyi) in agricultural and rangeland areas in California, USA. Owing to growing concerns over the risks to non-target species associated with the use of these rodenticides, the USA Environmental Protection Agency (EPA) proposed that the concentration of baits for above-ground use should be reduced from 0.01% to 0.005% active ingredient. We conducted field trials to compare the efficacy of 0.005% and 0.01% chlorophacinone and diphacinone baits in broadcast and spot applications for control of California ground squirrels on rangeland. We found no significant difference in efficacy owing to bait type, concentration or application method. Repeat testing is needed in other habitat types (e.g. crop areas) where alternative foods might reduce the effectiveness of a 0.005% bait application.
Context Loss of eggs to predators is a major cause of reproductive failure among birds. It is especially pronounced among ground-nesting birds because their eggs are accessible to a wide range of predators. Few studies document the main causes of clutch fate of ground-nesting birds. Aims The main objective of the present study was to identify the major egg predator of red-capped plovers (Charadrius ruficapillus). We also investigated the effectiveness of the following two primary strategies available to the plovers to avoid egg predation: (1) the placement of clutches under vegetative cover and (2) avoiding predators by nesting outside the peak season of predator occurrence. Methods Remote-sensing cameras were deployed on plover nests to identify egg predators and nests were monitored over four breeding seasons to document reproductive success and fate. An experiment using false clutches with model eggs investigated the influence of nest cover on the risk of egg predation throughout the year. Line-transect surveys were conducted to estimate the abundance of egg predators in and around the wetlands. Key results The little raven (Corvus mellori) was the major egg predator identified in 78.6% of red-capped plover clutches and in 92.4% of false clutches that were camera-monitored. The hatching success of plover eggs was not influenced by nest cover (P = 0.36), but model egg survival in false clutches improved significantly with the presence of nest cover (P = 0.02). The abundance of little ravens increased during the plover breeding season and was highly negatively correlated with false clutch survival (rpearson = –0.768, P = 0.005). Conclusions Little ravens were the major predator of red-capped plover eggs and their abundance increased significantly during the plover breeding season. Any influence of nest cover on hatching success of eggs may have been masked by the extremely high rate of egg loss associated with the increased little raven abundance during the plover breeding season. Implications The high rate of egg predation is likely to have negative consequences on the local red-capped plover population, suggesting management is warranted. Little raven populations have expanded and, thus, their impact as egg predators needs to be investigated especially on threatened species.
Habitat destruction and fragmentation, interactions with introduced species or the relocation of animals to form new populations for conservation purposes may result in a multiplication of population bottlenecks. Examples are the translocations of koalas to French Island and its derivative Kangaroo Island population, with both populations established as insurance policies against koala extinction. In terms of population size, these conservation programs were success stories. However, the genetic story could be different. We conducted a genetic investigation of French and Kangaroo Island koalas by using 15 microsatellite markers, 11 of which are described here for the first time. The results confirm very low genetic diversity. French Island koalas have 3.8 alleles per locus and Kangaroo Island koalas 2.4. The present study found a 19% incidence of testicular abnormality in Kangaroo Island animals. Internal relatedness, an individual inbreeding coefficient, was not significantly different in koalas with testicular abnormalities from that in other males, suggesting the condition is not related to recent inbreeding. It could instead result from an unfortunate selection of founder individuals carrying alleles for testicular abnormalities, followed by a subsequent increase in these alleles' frequencies through genetic drift and small population-related inefficiency of selection. Given the low diversity and possible high prevalence of deleterious alleles, the genetic viability of the population remains uncertain, despite its exponential growth so far. This stands as a warning to other introductions for conservation reasons.
Habitat destruction and fragmentation, interactions with introduced species or the relocation of animals to form new populations for conservation purposes may result in a multiplication of population bottlenecks. Examples are the translocations of koalas to French Island and its derivative Kangaroo Island population, with both populations established as insurance policies against koala extinction. In terms of population size, these conservation programs were success stories. However, the genetic story could be different. We conducted a genetic investigation of French and Kangaroo Island koalas by using 15 microsatellite markers, 11 of which are described here for the first time. The results confirm very low genetic diversity. French Island koalas have 3.8 alleles per locus and Kangaroo Island koalas 2.4. The present study found a 19% incidence of testicular abnormality in Kangaroo Island animals. Internal relatedness, an individual inbreeding coefficient, was not significantly different in koalas with testicular abnormalities from that in other males, suggesting the condition is not related to recent inbreeding. It could instead result from an unfortunate selection of founder individuals carrying alleles for testicular abnormalities, followed by a subsequent increase in these alleles' frequencies through genetic drift and small population-related inefficiency of selection. Given the low diversity and possible high prevalence of deleterious alleles, the genetic viability of the population remains uncertain, despite its exponential growth so far. This stands as a warning to other introductions for conservation reasons.
