Measuring the Demographic and Genetic Effects of Pest Control in a Highly Persecuted Feral Pig Population

Substantial efforts have been made to identify the most effective practices for the control and management of invasive vertebrate pest species, such as the feral pig (Sus scrofa). We investigated the demographics, abundance, and molecular ecology of a persecuted feral pig population that was subjected to control. We then applied methodologies to determine if we could retrospectively quantify any changes in the population structure or dynamics of these pigs. Feral pig demographic and abundance parameters indicated that in this population of feral pigs, there were very few detectable changes between the two aerial culling years. We observed this despite environmental conditions being optimal for control. Genetic results indicated that pigs culled in the latter 2004 cull were genetically identical to those pigs that inhabited the area a year earlier. The genetic population was geographically larger than the sample area. These findings indicate that the recovery in feral pig density witnessed in the controlled area was not a result of reinvasion from a separate, genetically distinct population, but rather, it was the result of reinvasion from feral pigs outside the study area but within the same genetic population. Importantly, we were unable to detect any recent genetic bottlenecks. This approach has considerable potential for auditing the effectiveness of control programs of pest species and assessing the feasibility of impacting upon or locally eradicating many other free-ranging pest species

Quantitative analysis of animal-welfare outcomes in helicopter shooting: a case study with feral dromedary camels (Camelus dromedarius)

Context Helicopter shooting is a common and effective tool for reducing overabundant wildlife populations. However, there is little quantitative information on the humaneness of the method, leading to uncertainty in wildlife-management policy. There is, subsequently, a need for an improved understanding of the welfare implications of helicopter shooting. Aim A study was undertaken to infer the humaneness of helicopter shooting for a case study species, the feral dromedary camel (Camelus dromedarius). Methods Seven post-mortem studies (n≤715) and one ante-mortem study (n≤192) were undertaken during routine helicopter shooting programs of free-ranging camels. In these studies, we measured four animal-welfare parameters to allow inference on the humaneness of the technique. These parameters were time to death, instantaneous death rate (proportion of animals for which time to death≤0), wounding rate and location of bullet-wound tract. We also modelled these welfare variables against hypothesised explanatory variables to assist improvement of future programs. Key results The mean wounding rate was 0.4%, and the killing efficacy of the technique was 99.6%. Mean time to death was 4s, and mean instantaneous death rate was 83%. Each animal displayed a mean 2.4 bullet-wound tracts, with 75%, 63% and 35% of animals shot at least once in the thorax, cranium and cervical spine, respectively. Regression analysis revealed that the identity of the shooter and the nature of the local vegetation were the most important factors associated with an animal experiencing an inferred instantaneous death or not. Conclusions Helicopter shooting of feral camels produces a very low wounding rate and rapid time to death. Shooter identity is the most important consideration for determining animal-welfare outcomes. Improvements to the humaneness of programs can be made by increasing the rigour of shooter selection and training. Implications Wildlife killing methods must be demonstrated to be humane to receive public support; however, few shooting methods are objectively examined. Helicopter shooting can be independently examined and operators assessed. Adoption of this examination template may allow continual improvement by industry as well as increasing societal acceptance of helicopter shooting

Improving animal welfare in wildlife shooting: The importance of projectile energy

In wildlife shooting programs, the energy profile of the projectile or bullet (i.e., kinetic energy transferred to the animal), as distinct from caliber (projectile diameter), is an important factor for animal welfare. We examined the role of projectile energy in determining animal welfare outcomes for a typical European rabbit (Oryctolagus cuniculus) sharpshooting program. We compared 2 projectiles of different energy profiles: low-energy 40-grain .22 long rifle rimfire (. 22LR; 198 J) bullets and high-energy 40-grain.222 Remington (R) centerfire (. 222R; 1,433 J) bullets, fired under similar conditions on 3 nights in September 2014, on a livestock grazing property near Broken Hill, New South Wales, southeastern Australia. We used a thermal-imaging camera to collect antemortem data from 500 rabbits that were shot at varying distance. We collected postmortem data via visual inspection from 482 rabbits that were killed. We used these data to compare 3 animal welfare parameters: wounding rate, duration of suffering, and ballistic injuries. We then used regression modeling to measure the effect of projectile type on these welfare parameters while accounting for shooting distance. All animal welfare parameters indicated that .222R projectiles were more humane than .22LR projectiles. When controlling for distance, for rabbits shot with a .22LR compared with a .222R, the odds of nonlethal wounding increased by a factor of 8 and noninstantaneous death increased by a factor of 9. All animal welfare parameters declined with increasing distance for both projectiles. Our results show that projectile energy and shooting distance were critical determinants of animal welfare outcomes in wildlife shooting programs

Assessment of animal welfare for helicopter shooting of feral horses

Context: Helicopter shooting is an effective tool for reducing feral horse (Equus caballus) populations that are considered overabundant. However, this tool has been less commonly used in recent years because of concerns about animal-welfare outcomes, which have not previously been quantified. Aims: The aims of the present study were to assess the helicopter shooting of feral horses to determine (1) the duration of stress, (2) the frequency of adverse animal-welfare events and (3) the influence of explanatory variables in determining welfare outcomes. Methods: We quantified the welfare outcomes of three helicopter shooting programs in central Australia during 2013 and 2015. We conducted ante-mortem observations of 937 horses and post-mortem observations of 630 horses. We measured the following three parameters to estimate the duration of stress from pursuit and the mode of death: chase time (CT), time to death (TTD) and total time (TT; CT+TTD). We quantified the frequency of adverse animal-welfare events, namely instantaneous death rate (IDR; percentage of animals for which TTD was zero), the apparent frequency of non-fatal wounding, and the frequency of bullet-wound tracts in different anatomical locations. We investigated the role of explanatory variables in determining whether or not a horse had an inferred instantaneous death. Key results: For all horses, the median CT was 42 s, the median TTD was 0 s (median TTD for horses not killed instantaneously was 15 s), and median TT was 52 s. At least 1% of horses were non-fatally wounded, IDR was 63% (60–66%), and 3% (2–5%) of horses were not shot in the cranium, neck or thorax. Shooter skill was the most important determinant of whether or not a horse had an instantaneous death. Conclusions: The animal-welfare outcomes of helicopter shooting appear to be similar for feral horses and feral camels (Camelus dromedarius), the only other species that has been studied using these methods, and could be refined by improving shooter skill. Implications: Quantifying animal-welfare outcomes is particularly important for contentious wildlife management techniques. Wildlife managers should integrate the results of welfare studies into decision-making processes rather than excluding contentious techniques from consideration on the basis of perception