Thelazia callipaeda as a potential new threat to european wildcats: insights from an eco-epidemiological study.

Global warming and displacement of vectors and wild and domestic hosts by humans greatly change host-parasite interactions and parasite transmission rates. Thelazia callipaeda Railliet and Henry, 1910 (Spirurida: Thelaziidae) is a zoonotic parasite rapidly colonizing Europe from its Asian native range. This nematode is vectored by Phortica flies and may cause ocular disorders, such as keratitis and corneal ulcers, in wild mammals, dogs, cats and humans. With the aim of detecting possible threats for the European wildcat (Felis silvestris) in one of its last Mediterranean strongholds, we initiated in 2017 a long-term monitoring program in Sierra Arana (southeastern Spain), which includes exploring its epidemiological and spatial relationships with domestic cats (Felis catus). During routine medical check-ups, we detected ocular nematodes in 3 of 17 (17.6%) wildcats and 1 of 23 (4.3%) domestic cats tested, confirmed to be T. callipaeda by microscopic and molecular analyses. This nematode species was first detected in the study area in 2021. To our knowledge, this is the first case of infection in wildcats in Spain. Through telemetry, we detected little spatial overlap between the home ranges of wildcats and domestic cats, which seems to be sufficient to facilitate the inter-specific transmission of T. callipaeda. Our findings suggest that this pathogen could be a new threat to the wildcat, a locally endangered wild felid. Further eco-epidemiological monitoring and sanitary control of domestic cats will be strongly needed, especially given the ongoing global warming scenario.

Predation impact on threatened spur-thighed tortoises by golden eagles when main prey is scarce.

A reduction in adult survival in long-living species may compromise population growth rates. The spur-thighed tortoise (Testudo graeca) is a long-lived reptile that is threatened by habitat loss and fragmentation. Golden eagles (Aquila chrysaetos), whose breeding habitats overlap that of tortoises, may predate them by dropping them onto rocks and breaking their carapaces. In SE Spain, the number of golden eagles has increased in the last decades and the abundance of their main prey (i.e., rabbits Oryctolagus cuniculus) has decreased. Our aims were to 1) describe the role of tortoises in golden eagles' diet, and 2) estimate the predation impact of golden eagles on tortoises in eagles' territories and in the regional tortoise population. We collected regurgitated pellets and prey remains under eagle nests and roosts, and obtained information on tortoise abundance and population structure and rabbit abundance. We found that tortoises were an alternative prey to rabbits, so that eagles shifted to the former where the latter were scarce. The average predation rate on tortoises was very low at the two studied scales. However, eagles showed a marked selection for adult female tortoises, which led the tortoise sex ratio to be biased towards males in those eagle territories with higher tortoise predation. Whether this may compromise the spur-thighed tortoise long-term population viability locally deserves further attention.

The value of transhumance for biodiversity conservation: Vulture foraging in relation to livestock movements.

In recent decades, intensive techniques of livestock raising have flourished, which has largely replaced traditional farming practices such as transhumance. These changes may have affected scavengers' behaviour and ecology, as extensive livestock is a key source of carrion. This study evaluates the spatial responses of avian scavengers to the seasonal movements of transhumant herds in south-eastern Spain. We surveyed the abundance of avian scavengers and ungulates, and analysed the factors affecting the space use by 30 GPS-tracked griffon vultures (Gyps fulvus). Griffons' foraging activity increased in the pasturelands occupied by transhumant herds, which implied greater vulture abundance at the landscape level during the livestock season. In contrast, facultative scavengers were more abundant without transhumant livestock herds, and the abundance of wild ungulates did not change in relation to livestock presence. We conclude that fostering transhumance and other traditional farming systems, to the detriment of farming intensification, could favour vulture conservation.

Biases in the Detection of Intentionally Poisoned Animals: Public Health and Conservation Implications from a Field Experiment.

Intentional poisoning is a global wildlife problem and an overlooked risk factor for public health. Managing poisoning requires unbiased and high-quality data through wildlife monitoring protocols, which are largely lacking. We herein evaluated the biases associated with current monitoring programmes of wildlife poisoning in Spain. We compared the national poisoning database for the 1990-2015 period with information obtained from a field experiment during which we used camera-traps to detect the species that consumed non-poisoned baits. Our findings suggest that the detection rate of poisoned animals is species-dependent: Several animal groups (e.g., domestic mammalian carnivores and vultures) tended to be over-represented in the poisoning national database, while others (e.g., corvids and small mammals) were underrepresented. As revealed by the GLMM analyses, the probability of a given species being overrepresented was higher for heaviest, aerial, and cryptic species. In conclusion, we found that monitoring poisoned fauna based on heterogeneous sources may produce important biases in detection rates; thus, such information should be used with caution by managers and policy-makers. Our findings may guide to future search efforts aimed to reach a more comprehensive understanding of the intentional wildlife poisoning problem.

From sport hunting to breeding success: Patterns of lead ammunition ingestion and its effects on an endangered raptor.

Lead is highly toxic for wildlife, with pernicious consequences especially in long-lived predators. The causes of lead ammunition ingestion in Bonelli's eagle (Aquila fasciata) and its effects on breeding success were studied in one of the most important populations of this endangered species in Europe. Regurgitated pellets belonging to different pairs from 2004 to 2014 were analyzed, both in the breeding (1363 pellets from 12 territories) and non-breeding (172 pellets from 9 territories) seasons. From these territories, 57 molted feathers to study lead contamination were analyzed, and breeding success was monitored for 41 breeding attempts. The occurrence of lead shots in pellets was detected using X-ray photographs. Pellets were also used to describe eagle diet. Lead shots in pellets were present in 83.3% of the territories. The frequency of occurrence of lead shots in pellets (2.81% in spring and 1.31% in autumn) was primarily related to the consumption of red-legged partridge in the breeding season (when partridges are hunted from blinds using calling lures), and secondarily to rabbit consumption in the non-breeding season (coinciding with the main hunting season). Thus, our results indicate that injured small-game were the main source of lead contamination in the Bonelli's eagle. For the first time for a raptor species, a positive relationship between the frequency of occurrence of lead shots in pellets and lead concentration in eagles' feathers has been documented. Lead concentration in feathers (mean±SD: 816±426µgkg-1, with no sex-related differences) was high for a species that rarely eats carrion or aquatic birds (the main prey-related lead source for raptors). This had negative effects on breeding success, which could jeopardize Bonelli's eagles in other European populations that are sustained by juvenile dispersal from the study population. Our work shows that some game modalities pose a potential threat to endangered raptors.

Changes in intrapopulation resource use patterns of an endangered raptor in response to a disease-mediated crash in prey abundance.

1. A long-standing question in ecology is how natural populations respond to a changing environment. Emergent optimal foraging theory-based models for individual variation go beyond the population level and predict how its individuals would respond to disturbances that produce changes in resource availability. 2. Evaluating variations in resource use patterns at the intrapopulation level in wild populations under changing environmental conditions would allow to further advance in the research on foraging ecology and evolution by gaining a better idea of the underlying mechanisms explaining trophic diversity. 3. In this study, we use a large spatio-temporal scale data set (western continental Europe, 1968-2006) on the diet of Bonelli's Eagle Aquila fasciata breeding pairs to analyse the predator trophic responses at the intrapopulation level to a prey population crash. In particular, we borrow metrics from studies on network structure and intrapopulation variation to understand how an emerging infectious disease [the rabbit haemorrhagic disease (RHD)] that caused the density of the eagle's primary prey (rabbit Oryctolagus cuniculus) to dramatically drop across Europe impacted on resource use patterns of this endangered raptor. 4. Following the major RHD outbreak, substantial changes in Bonelli's Eagle's diet diversity and organisation patterns at the intrapopulation level took place. Dietary variation among breeding pairs was larger after than before the outbreak. Before RHD, there were no clusters of pairs with similar diets, but significant clustering emerged after RHD. Moreover, diets at the pair level presented a nested pattern before RHD, but not after. 5. Here, we reveal how intrapopulation patterns of resource use can quantitatively and qualitatively vary, given drastic changes in resource availability. 6. For the first time, we show that a pathogen of a prey species can indirectly impact the intrapopulation patterns of resource use of an endangered predator.

Predator-prey relationships in a Mediterranean vertebrate system: Bonelli's eagles, rabbits and partridges.

How predators impact on prey population dynamics is still an unsolved issue for most wild predator-prey communities. When considering vertebrates, important concerns constrain a comprehensive understanding of the functioning of predator-prey relationships worldwide; e.g. studies simultaneously quantifying 'functional' and 'numerical responses' (i.e., the 'total response') are rare. The functional, the numerical, and the resulting total response (i.e., how the predator per capita intake, the population of predators and the total of prey eaten by the total predators vary with prey densities) are fundamental as they reveal the predator's ability to regulate prey population dynamics. Here, we used a multi-spatio-temporal scale approach to simultaneously explore the functional and numerical responses of a territorial predator (Bonelli's eagle Hieraaetus fasciatus) to its two main prey species (the rabbit Oryctolagus cuniculus and the red-legged partridge Alectoris rufa) during the breeding period in a Mediterranean system of south Spain. Bonelli's eagle responded functionally, but not numerically, to rabbit/partridge density changes. Type II, non-regulatory, functional responses (typical of specialist predators) offered the best fitting models for both prey. In the absence of a numerical response, Bonelli's eagle role as a regulating factor of rabbit and partridge populations seems to be weak in our study area. Simple (prey density-dependent) functional response models may well describe the short-term variation in a territorial predator's consumption rate in complex ecosystems.

Laying the foundations for a human-predator conflict solution: assessing the impact of Bonelli's eagle on rabbits and partridges.

BACKGROUND: Predation may potentially lead to negative effects on both prey (directly via predators) and predators (indirectly via human persecution). Predation pressure studies are, therefore, of major interest in the fields of theoretical knowledge and conservation of prey or predator species, with wide ramifications and profound implications in human-wildlife conflicts. However, detailed works on this issue in highly valuable--in conservation terms--Mediterranean ecosystems are virtually absent. This paper explores the predator-hunting conflict by examining a paradigmatic, Mediterranean-wide (endangered) predator-two prey (small game) system. METHODOLOGY/PRINCIPAL FINDINGS: We estimated the predation impact ('kill rate' and 'predation rate', i.e., number of prey and proportion of the prey population eaten, respectively) of Bonelli's eagle Aquila fasciata on rabbit Oryctolagus cuniculus and red-legged partridge Alectoris rufa populations in two seasons (the eagle's breeding and non-breeding periods, 100 days each) in SE Spain. The mean estimated kill rate by the seven eagle reproductive units in the study area was c. 304 rabbits and c. 262 partridges in the breeding season, and c. 237 rabbits and c. 121 partridges in the non-breeding period. This resulted in very low predation rates (range: 0.3-2.5%) for both prey and seasons. CONCLUSIONS/SIGNIFICANCE: The potential role of Bonelli's eagles as a limiting factor for rabbits and partridges at the population scale was very poor. The conflict between game profitability and conservation interest of either prey or predators is apparently very localised, and eagles, quarry species and game interests seem compatible in most of the study area. Currently, both the persecution and negative perception of Bonelli's eagle (the 'partridge-eating eagle' in Spanish) have a null theoretical basis in most of this area.