Expanding the use of portable XRF to monitor lead exposure in an Australian duck species two decades after a ban on lead shot.

There is growing worldwide recognition of the threat posed by toxic lead for wildlife and humans. Lead toxicity from ammunition has been shown to be a threat to waterbirds across the globe. Lead shot was banned for all waterfowl hunting in Victoria, Australia, in 2002. However, no assessments of lead exposure in Australian waterfowl have been published since the 1990s. Our aim was to estimate contemporary lead exposure via measuring bone lead concentrations in a harvested dabbling duck, the Pacific black duck (Anas superciliosa). We collected wings from 77 Pacific black ducks, spanning 2018 (n = 30) and 2021 (n = 47), from nine sites with long-term histories of regular waterfowl hunting. We sought to validate portable X-ray fluorescence (XRF) for this purpose by taking a piece of humerus bone from each bird, and measuring lead concentration (mg/kg), first via non-destructive XRF and then via destructive inductively coupled plasma mass spectrometry (ICP-MS) and validated the relationship via regression analysis. Portable XRF bone lead measurement demonstrated a strong correlation with ICP-MS results using root-transformed regression (R2 = 0.85). Greater than 92 % of ducks had only background lead exposure (<10 mg/kg). When compared to historical studies in the same species at similar field sites from the 1990s, lead exposure levels were considerably lower, with mean lead concentrations ∼2-fold lower (3.7 c.f. 7.7 mg/kg), and the frequency of birds with severe lead exposure (>20 mg/kg) ∼3-fold lower (2.6 c.f. 7.5 %). Our results confirm that portable XRF is a useful option for measurement of bone lead in Australasian waterbird species. Our findings also demonstrate that a ban on the use of lead shot around 20 years ago has been associated with a substantial reduction in lead exposure in at least one species of waterfowl.

Estimating deer density and abundance using spatial mark-resight models with camera trap data.

Globally, many wild deer populations are actively studied or managed for conservation, hunting, or damage mitigation purposes. These studies require reliable estimates of population state parameters, such as density or abundance, with a level of precision that is fit for purpose. Such estimates can be difficult to attain for many populations that occur in situations that are poorly suited to common survey methods. We evaluated the utility of combining camera trap survey data, in which a small proportion of the sample is individually recognizable using natural markings, with spatial mark-resight (SMR) models to estimate deer density in a variety of situations. We surveyed 13 deer populations comprising four deer species (Cervus unicolor, C. timorensis, C. elaphus, Dama dama) at nine widely separated sites, and used Bayesian SMR models to estimate population densities and abundances. Twelve surveys provided sufficient data for analysis and seven produced density estimates with coefficients of variation (CVs) ≤ 0.25. Estimated densities ranged from 0.3 to 24.6 deer km-2. Camera trap surveys and SMR models provided a powerful and flexible approach for estimating deer densities in populations in which many detections were not individually identifiable, and they should provide useful density estimates under a wide range of conditions that are not amenable to more widely used methods. In the absence of specific local information on deer detectability and movement patterns, we recommend that at least 30 cameras be spaced at 500-1,000 m and set for 90 days. This approach could also be applied to large mammals other than deer.

Portable X-ray fluorescence for bone lead measurements of Australian eagles.

Lead (Pb) toxicity from ammunition has been shown to be a threat to scavenging birds across the globe. Toxic levels of lead have recently been found in Australia's largest bird of prey, the wedge-tailed eagle (Aquila audax), through inductively coupled plasma mass spectrometry (ICP-MS) analysis of liver and bone samples. However, ICP-MS is consumptive (causing damage to archived specimens), time-consuming, and expensive. For these reasons, portable X-ray fluorescence (XRF) devices have been optimized to measure bone lead in North American avian species, humans, and other environmental samples. In this study, we assessed portable XRF for bone lead measurement in Australian raptors in two parts. First, we validated the method using tissues from wedge-tailed eagles from Tasmania (A. a. fleayi), analysing bone samples taken from sites on the femur immediately adjacent to sites for which we had ICP-MS data (n = 89). Second, we measured lead via portable XRF in the skulls of wedge-tailed eagles from south-eastern mainland Australia (A. a. audax) collected during a criminal prosecution (n = 92). Portable XRF bone lead measurement demonstrated an excellent correlation with ICP-MS results using root-transformed regression (R2 = 0.88). Calculated equivalent ICP-MS values revealed that greater than 50% of the eagles from mainland Australia had elevated lead levels (>10 mg/kg) and 13% had severe lead exposure (>20 mg/kg). Our results support previous studies of North American avian species and suggest that portable XRF could be a useful and inexpensive option for measurement of bone lead in Australian scavenger species.

A comparison of fragmenting lead-based and lead-free bullets for aerial shooting of wild pigs.

In response to the health threats posed by toxic lead to humans, scavenging wildlife and the environment, there is currently a focus on transitioning from lead-based to lead-free bullets for shooting of wild animals. We compared efficiency metrics and terminal ballistic performance for lead-based and lead-free (non-lead) bullets for aerial shooting of wild pigs (Sus scrofa) in eastern Australia. Ballistic testing revealed that lead-based and lead-free bullets achieved similar performance in precision and muzzle kinetic energy (E0) levels (3337.2 J and 3345.7 J, respectively). An aerial shooting trial was conducted with wild pigs shot with one type of lead-based and one type of lead-free bullets under identical conditions. Observations were made from 859 shooting events (n = 430 and 429 respectively), with a sub-set of pigs examined via gross post-mortem (n = 100 and 108 respectively), and a further sub-set examined via radiography (n = 94 and 101 respectively). The mean number of bullets fired per pig killed did not differ greatly between lead-based and lead-free bullets respectively (4.09 vs 3.91), nor did the mean number of bullet wound tracts in each animal via post-mortem inspection (3.29 vs 2.98). However, radiography revealed a higher average number of fragments per animal (median >300 vs median = 55) and a broader distribution of fragments with lead-based bullets. Our results suggest that lead-based and lead-free bullets are similarly effective for aerial shooting of wild pigs, but that the bullet types behave differently, with lead-based bullets displaying a higher degree of fragmentation. These results suggest that aerial shooting may be a particularly important contributor to scavenging wildlife being exposed to lead and that investigation of lead-free bullets for this use should continue.

Assessing the impact of different persuasive messages on the intentions and behaviour of cat owners: A randomised control trial.

Owners of free-ranging domestic cats (Felis catus) are under increasing pressure to keep their pet contained within their house or yard, in an effort to reduce adverse impacts on cat welfare, ecosystem biodiversity and neighbourhoods. We conducted a randomised online experiment to assess the effectiveness of two persuasive messages to encourage cat owners to contain their pets. A total of 512 Australian cat owners, who currently do not contain their cats, were randomly assigned to view one of three short video messages: one framed to highlight the negative impact of cats' on wildlife and biodiversity ('wildlife protection' frame), one framed to highlight the health and safety benefits of keeping cats contained ('cat benefit' frame), and a control message focused on general information about cats ('neutral' frame). We assessed the impact of these video messages on two post-treatment outcome variables: (1) the intention of owners to contain their cat; and (2) the adoption of containment practices, based on a 4-week follow-up survey. Mediation analysis revealed both the 'wildlife protection' and 'cat benefit' messages increased owners' motivation to contain their cat and their beliefs that they could effectively contain their cat to achieve the desired outcomes (response efficacy). In turn, higher levels of motivation and response efficacy predicted increased cat containment intentions and increased adoption of cat containment. In addition, the response efficacy effects of the 'cat benefit' message were strengthened by the cat owner's bond to their pet, suggesting audience segmentation may improve the effectiveness of interventions. Implications for future intervention development are discussed.

Born to roam? Surveying cat owners in Tasmania, Australia, to identify the drivers and barriers to cat containment.

Free-roaming domestic cats, Felis catus, are a major public nuisance in neighbourhoods across the world, and have been linked to biodiversity loss and a host of community health problems. Owners who let their cats roam, also place their cats at risk of serious injury. One management strategy that is gaining considerable support involves encouraging cat owners to contain their pets within their property. Contemporary behaviour change models highlight the importance of identifying drivers and barriers that encourage and discourage target behaviours such as cat containment. Results from a random dial phone survey of 356 cat owners in northern Tasmania identified four distinct cat containment profiles: owners who contained their cat all the time, owners who only contained their cat at night, owners who sporadically contained their cat with no set routine, and owners who made no attempt to contain their pet. Our results indicated that cat-owners' decisions to contain or not contain their cats were guided by a range of factors including owners' beliefs about their ability to implement an effective containment strategy and their views about the physical and psychological needs of their cats. The results are discussed in terms of improving the behavioural effectiveness of cat containment interventions by selecting appropriate behavioural change tools for the identified drivers and barriers, and developing targeted engagement strategies and messaging.