Widespread exposure of powerful owls to second-generation anticoagulant rodenticides in Australia spans an urban to agricultural and forest landscape

Network analysis to reveal the most commonly detected compounds in predator-prey pairs in freshwater and marine mammals and fish in Europe

Marine and freshwater mammalian predators and fish samples, retrieved from environmental specimen banks (ESBs), natural history museum (NHMs) and other scientific collections, were analysed by LIFE APEX partners for a wide range of legacy and emerging contaminants (2545 in total). Network analysis was used to visualize the chemical occurrence data and reveal the predominant chemical mixtures for the freshwater and marine environments. For this purpose, a web tool was created to explore these chemical mixtures in predator-prey pairs. Predominant chemicals, defined as the most prevalent substances detected in prey-predator pairs were identified through this innovative approach. The analysis established the most frequently co-occurring substances in chemical mixtures from AP&P in the marine and freshwater environments. Freshwater and marine environments shared 23 chemicals among their top 25 predominant chemicals. Legacy chemical, including perfluorooctanesulfonic acid (PFOS), brominated diphenyl ethers (BDEs), polychlorinated biphenyls (PCBs), hexachlorobenzene and mercury were dominant chemicals in both environments. Furthermore, N-acetylaminoantipyrine was a predominant pharmaceutical in both environments. The LIFE APEX chemical mixture application (https://norman-data.eu/LIFE_APEX_Mixtures) was proven to be useful to establish most prevalent compounds in terms of number of detected counts in prey-predator pairs. Nonetheless, further research is needed to establish food chain associations of the predominant chemicals.

The missing toxic link: Exposure of non-target native marsupials to second-generation anticoagulant rodenticides (SGARs) suggest a potential route of transfer into apex predators

Anticoagulant rodenticides (ARs) are used globally to control rodent pests. Second-generation anticoagulant rodenticides (SGARs) persist in the liver and pose a significant risk of bioaccumulation and secondary poisoning in predators, including species that do not generally consume rodents. As such, there is a clear need to understand the consumption of ARs, particularly SGARs, by non-target consumers to determine the movement of these anticoagulants through ecosystems. We collected and analysed the livers from deceased common brushtail possums (Trichosurus vulpecula) and common ringtail possums (Pseudocheirus peregrinus), native Australian marsupials that constitute the main diet of the powerful owl (Ninox strenua), an Australian apex predator significantly exposed to SGAR poisoning. ARs were detected in 91 % of brushtail possums and 40 % of ringtail possums. Most of the detections were attributed to SGARs, while first-generation anticoagulant rodenticides (FGARs) were rarely detected. SGAR concentrations were likely lethal or toxic in 42 % of brushtail possums and 4 % of ringtail possums with no effect of age, sex, or weight detected in either species. There was also no effect of the landscape type possums were from, suggesting SGAR exposure is ubiquitous across landscapes. The rate of exposure detected in these possums provides insight into the pathway through which ARs are transferred to one of their key predators, the powerful owl. With SGARs entering food-webs through non-target species, the potential for bioaccumulation and broader secondary poisoning of predators is significantly greater and highlights an urgent need for routine rodenticide testing in non-target consumers that present as ill or found deceased. To limit their impact on ecosystem stability the use of SGARs should be significantly regulated by governing agencies.

Rapid visual dual-mode detection of Zr(IV) based on L-histidine functionalized gold nanoparticles

Heavy metal pollution has always been a great threat to human health and safety. Compared with other heavy metals, although zirconium ion (Zr(IV)) is equally harmful, due to the lack of research on Zr(IV) in the biological systems and environment, its detection does not seem to have received the attention it deserves. Herein, a rapid visual dual-mode detection (colorimetric and chrominance method) of Zr(IV) based on L-histidine functionalized gold nanoparticles (HIS-AuNPs) has been reported. AuNPs and HIS-AuNPs before and after adding Zr(IV) were characterized by UV-Vis, TEM, DLS, Zeta potential, EDS and FT-IR, etc. These results showed that L-histidine was successfully modified on the surface of AuNPs by forming a stable Au-N bond, and its modification had little effect on the dispersion degree of AuNPs. After the addition of Zr(IV), interaction of this metal ion with the imidazolyl group on L-histidine can obviously cause the aggregation of HIS-AuNPs within 12 min, and the dispersion state and particle size of HIS-AuNPs can be significantly changed. These two detection modes were established by means of absorbance and color change of solution, and being used in addition and recovery experiments of Zr(IV) in natural water. Under the optimal conditions, these two modes exhibited good linearity within 15-70 and 20-100 μmol L-1, and limit of detection of 2.62 and 6.25 μmol L-1. The proposed method was highly sensitive and selective, which provided a new convenient way to realize the detection of Zr(IV).

Construction of a three-mode sensor based on gold nanoparticles and carbon quantum dots as probes for the detection of thiosemicarbazone

In this study, ginkgo leaves were used as a carbon source to synthesize carbon quantum dots (CQDs) with uniform particle size, high fluorescence (FL) intensity and strong stability, using a hydrothermal method. FL could be quenched by the FL resonance energy transfer effect between CQDs and gold nanoparticles (AuNPs), an important FL quenching agent. The electrostatic attraction between thiosemicarbazone (TSC) and citrate on the surface of AuNPs and the formation of a stable Au-S bond between TSC and AuNPs led to the aggregation of AuNPs and thus weakened the quenching effect on CQDs and partly recovered the FL. A sensor in FL mode for the detection of TSC was constructed based on the above-mentioned FL "off" and "on" phenomena. The results showed a good linear correlation in the concentration range 0-1.75 μM, and the limit of detection was as low as 0.05 μM. In addition, the aggregation of AuNPs caused by TSC also led to a change in the absorbance curve and color of the solution; colorimetric and chrominance detection modes were also constructed using these two types of changes, with sensitive responses ranging 0-2.25 μM and 0-1.60 μM and the limits of detection of 0.03 μM and 0.08 μM, respectively. More importantly, these three detection modes obtained satisfactory recovery rates in the detection of the TSC content in river water, liquor and wheat samples, and the detection results were mutually verified (95.18% to 104.96%).

Active monitoring of long-eared owl (Asio otus) nestlings reveals widespread exposure to anticoagulant rodenticides across different agricultural landscapes

The widespread use of anticoagulant rodenticides (ARs) poses a worldwide threat to farmland wildlife. These compounds accumulate in tissues of both target and non-target species, potentially endangering both direct consumers and their predators. However, investigations on ARs in blood of free-ranging predatory birds are rare. Here, the long-eared owl (Asio otus) has been used as a model predator to assess AR exposure in different agricultural landscapes from a Mediterranean semiarid region. A total of 69 owlets from 38 nests were blood-sampled over 2021 and 2022, aiming to detect AR residues and explore factors that determine their exposure, such as land uses. In addition, prothrombin time (PT) test was conducted to assess potential effects of AR contamination. Overall, nearly all the samples (98.6 %) tested positive for at least one compound and multiple ARs were found in most of the individuals (82.6 %). Among the ARs detected, flocoumafen was the most common compound (88.4 % of the samples). AR total concentration (ΣARs) in blood ranged from 0.06 to 34.18 ng mL-1, detecting the highest levels in the most intensively cultivated area. The analysis of owl pellets from 19 breeding territories showed relevant among-site differences in the contribution of rodents and birds into the diet of long-eared owls, supporting its high dietary plasticity and indicating AR presence at multiple trophic levels. Moreover, a positive and significant correlation was found between ΣARs and PT (Rho = 0.547, p < 0.001), which demonstrates the direct effect of ARs on free-living nestlings. Our results provide a preliminary overview of AR exposure in a little-studied owl species inhabiting agricultural and rural landscapes. Despite the low detected levels, these findings indicate widespread exposure -often to multiple compounds- from early life stages, which raises concern and draws attention to an ongoing and unresolved contamination issue.

Anticoagulant Rodenticide Toxicity in Terrestrial Raptors: Tools to Estimate the Impact on Populations in North America and Globally

Anticoagulant rodenticides (ARs) have caused widespread contamination and poisoning of predators and scavengers. The diagnosis of toxicity proceeds from evidence of hemorrhage, and subsequent detection of residues in liver. Many factors confound the assessment of AR poisoning, particularly exposure dose, timing and frequency of exposure, and individual and taxon-specific variables. There is a need, therefore, for better AR toxicity criteria. To respond, we compiled a database of second-generation anticoagulant rodenticide (SGAR) residues in liver and postmortem evaluations of 951 terrestrial raptor carcasses from Canada and the United States, 1989 to 2021. We developed mixed-effects logistic regression models to produce specific probability curves of the toxicity of ∑SGARs at the taxonomic level of the family, and separately for three SGARs registered in North America, brodifacoum, bromadiolone, and difethialone. The ∑SGAR threshold concentrations for diagnosis of coagulopathy at 0.20 probability of risk were highest for strigid owls (15 ng g-1 ) lower and relatively similar for accipitrid hawks and eagles (8.2 ng g-1 ) and falcons (7.9 ng g-1 ), and much lower for tytonid barn owls (0.32 ng g-1 ). These values are lower than those we found previously, due to compilation and use of a larger database with a mix of species and source locations, and also to refinements in the statistical methods. Our presentation of results on the family taxonomic level should aid in the global applicability of the numbers. We also collated a subset of 440 single-compound exposure events and determined the probability of SGAR-poisoning symptoms as a function of SGAR concentration, which we then used to estimate relative SGAR toxicity and toxic equivalence factors: difethialone, 1, brodifacoum, 0.8, and bromadiolone, 0.5. Environ Toxicol Chem 2024;00:1-11. © 2024 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Silent killers? The widespread exposure of predatory nocturnal birds to anticoagulant rodenticides

Anticoagulant rodenticides (ARs) influence predator populations and threaten the stability of ecosystems. Understanding the prevalence and impact of rodenticides in predators is crucial to inform conservation planning and policy. We collected dead birds of four nocturnal predatory species across differing landscapes: forests, agricultural, urban. Liver samples were analysed for eight ARs: three First Generation ARs (FGARs) and five SGARs (Second Generation ARs). We investigated interspecific differences in liver concentrations and whether landscape composition influenced this. FGARs were rarely detected, except pindone at low concentrations in powerful owls Ninox strenua. SGARs, however, were detected in every species and 92 % of birds analysed. Concentrations of SGARs were at levels where potential toxicological or lethal impacts would have occurred in 33 % of powerful owls, 68 % of tawny frogmouths Podargus strigoides, 42 % of southern boobooks N. bookbook and 80 % of barn owls Tyto javanica. When multiple SGARs were detected, the likelihood of potentially lethal concentrations of rodenticides increased. There was no association between landscape composition and SGAR exposure, or the presence of multiple SGARs, suggesting rodenticide poisoning is ubiquitous across all landscapes sampled. This widespread human-driven contamination in wildlife is a major threat to wildlife health. Given the high prevalence and concentrations of SGARs in these birds across all landscape types, we support the formal consideration of SGARs as a threatening process. Furthermore, given species that do not primarily eat rodents (tawny frogmouths, powerful owls) have comparable liver rodenticide concentrations to rodent predators (southern boobook, eastern barn owl), it appears there is broader contamination of the food-web than anticipated. We provide evidence that SGARs have the potential to pose a threat to the survival of avian predator populations. Given the functional importance of predators in ecosystems, combined with the animal welfare impacts of these chemicals, we propose governments should regulate the use of SGARs.

Successful rehabilitation and release of a powerful owl chick with suspected rodenticide poisoning

The successful rehabilitation and release of raptor chicks can be challenging, especially when the chicks are still in the post-fledging dependency period. Here, we report on a recently fledged powerful owl chick that was held in care for 33 days before being successfully reunited with its parents. We document the steps undertaken during the entire process from collection from the wild to post-release monitoring and recommend clinical procedures for treatment of raptors entering veterinary facilities. Success of this rehabilitation was facilitated by early care and treatment for potential rodenticide poisoning, as well as the integration of citizen scientists monitoring the family unit in the field while the chick was in care and during the post-release period. Given the emerging evidence of widespread rodenticide poisoning in raptors both in Australia and globally, it is critical to suspect all raptors may have been exposed to anticoagulant rodenticides and commence treatment with vitamin K immediately. Routine treatment for rodenticides early increases the probability of successful recovery post-trauma as well as reducing the time in treatment as much as possible.

Developmental toxicity induced by brodifacoum in zebrafish (Danio rerio) early life stages

OBJECTIVES

The present study mainly focused on the assessment of developmental toxicity induced by exposure to brodifacoum (BDF) in zebrafish at early life stages.

MATERIAL AND METHODS

Zebrafish embryos were exposed to 0.2, 0.4, and 0.8 mg/L of BDF from 6 to 96 hr post-fertilization (hpf), and the toxic effects of BDF on early embryonic development were investigated in terms of morphological changes, oxidative stress, and alterations in heart development-related genes.

RESULTS

The experimental results showed that BDF significantly decreased the heart rate, survival rate, body length, and spontaneous movements of zebrafish embryos at 0.8 mg/L, and the morphological developmental abnormalities were also observed at 96 hpf. In addition, exposure to BDF significantly increased oxidative stress levels in zebrafish embryos by increasing the enzymatic activities of catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA) levels, and decreased glutathione (GSH) levels. Furthermore, BDF treatment-induced alterations in the expression levels of the heart development-related genes (gata4, sox9b, tbx2b, and nppa).

CONCLUSION

Results from this study indicated that exposure to BDF could lead to marked growth inhibition and significantly alter the activities of antioxidant enzymes in zebrafish embryos. Moreover, BDF exposure exhibited severe cardiotoxicity and significantly disrupted heart development-related genes. The results indicated that BDF could induce developmental and cardiac toxicity in zebrafish embryos.

Second-generation anticoagulant rodenticides in the blood of obligate and facultative European avian scavengers

The widespread use of second-generation anticoagulant rodenticides (SGARs) and their high persistence in animal tissues has led to these compounds becoming ubiquitous in rodent-predator-scavenger food webs. Exposure to SGARs has usually been investigated in wildlife species found dead, and despite growing evidence of the potential risk of secondary poisoning of predators and scavengers, the current worldwide exposure of free-living scavenging birds to SGARs remains scarcely investigated. We present the first active monitoring of blood SGAR concentrations and prevalence in the four European obligate (i.e., vultures) and facultative (red and black kites) avian scavengers in NE Spain. We analysed 261 free-living birds and detected SGARs in 39.1% (n = 102) of individuals. Both SGAR prevalence and concentrations (ΣSGARs) were related to the age and foraging behaviour of the species studied. Black kites showed the highest prevalence (100%), followed by red kites (66.7%), Egyptian (64.2%), bearded (20.9%), griffon (16.9%) and cinereous (6.3%) vultures. Overall, both the prevalence and average ΣSGARs were higher in non-nestlings than nestlings, and in species such as kites and Egyptian vultures foraging in anthropic landscapes (e.g., landfill sites and livestock farms) and exploiting small/medium-sized carrions. Brodifacoum was most prevalent (28.8%), followed by difenacoum (16.1%), flocoumafen (12.3%) and bromadiolone (7.3%). In SGAR-positive birds, the ΣSGAR (mean ± SE) was 7.52 ± 0.95 ng mL^-1; the highest level detected being 53.50 ng mL^-1. The most abundant diastereomer forms were trans-bromadiolone and flocoumafen, and cis-brodifacoum and difenacoum, showing that lower impact formulations could reduce secondary exposures of non-target species. Our findings suggest that SGARs can bioaccumulate in scavenging birds, showing the potential risk to avian scavenging guilds in Europe and elsewhere. We highlight the need for further studies on the potential adverse effects associated with concentrations of SGARSs in the blood to better interpret active monitoring studies of free-living birds.

Pesticide impacts on avian species with special reference to farmland birds: a review

For decades, we have observed a major biodiversity crisis impacting all taxa. Avian species have been particularly well monitored over the long term, documenting their declines. In particular, farmland birds are decreasing worldwide, but the contribution of pesticides to their decline remains controversial. Most studies addressing the effects of agrochemicals are limited to their assessment under controlled laboratory conditions, the determination of lethal dose 50 (LD₅₀) values and testing in a few species, most belonging to Galliformes. They often ignore the high interspecies variability in sensitivity, delayed sublethal effects on the physiology, behaviour and life-history traits of individuals and their consequences at the population and community levels. Most importantly, they have entirely neglected to test for the multiple exposure pathways to which individuals are subjected in the field (cocktail effects). The present review aims to provide a comprehensive overview for ecologists, evolutionary ecologists and conservationists. We aimed to compile the literature on the effects of pesticides on bird physiology, behaviour and life-history traits, collecting evidence from model and wild species and from field and lab experiments to highlight the gaps that remain to be filled. We show how subtle nonlethal exposure might be pernicious, with major consequences for bird populations and communities. We finally propose several prospective guidelines for future studies that may be considered to meet urgent needs.