Low signs of territorial behavior in the Eurasian otter during low-water conditions in a Mediterranean river.

The Eurasian otter Lutra lutra is a territorial semi-aquatic carnivore usually found at low densities in rivers, coastal areas, and wetlands. Its diet is based on prey associated with aquatic environments. Mediterranean rivers are highly seasonal, and suffer reduced flow during the summer, resulting in isolated river sections (pools) that sometimes can be left with a minimal amount of water, leading to concentrations of food for otters. To our knowledge, this process, which was known to field naturalists, has not been accurately described, nor have otter densities been estimated under these conditions. In this study, we describe the population size and movements of an aggregation of otters in an isolated pool in the Guadiana River in the Tablas de Daimiel National Park (central Spain), which progressively dried out during the spring-summer of 2022, in a context of low connectivity due to the absence of circulating water in the Guadiana and Gigüela rivers. Using non-invasive genetic sampling of 120 spraints collected along 79.4 km of sampling transects and spatial capture-recapture methods, we estimated the otter density at 1.71 individuals/km of river channel length (4.21 individuals/km2) in a progressively drying river pool, up to five times higher than previously described in the Iberian Peninsula. The movement patterns obtained with the spatial capture-recapture model are not quite different from those described in low density, which seems to indicate a wide home range overlap, with low signs of territoriality.

Mycobacterium bovis in Egyptian mongoose, Spain.

Tuberculosis caused by Mycobacterium bovis and other related mycobacteria has been reported in a wide range of mammals worldwide. In the case of the Herpestidae family, Mycobacterium mungi and M. bovis, both belonging to the Mycobacterium tuberculosis Complex, have been reported in banded mongooses (Mungos mungo) in Africa and in Egyptian mongooses (Herpestes ichneumon) in Portugal, respectively. Thus, we hypothesized that Tuberculosis may occur in Egyptian mongooses from Spain. Twenty-five found dead Egyptian mongooses were necropsied in order to detect macroscopic TB-compatible lesions and mandibular lymph nodes and lungs were cultured onto mycobacteria-specific growth media. We isolated M. bovis in 3/25 Egyptian mongooses (12.00%, IC95: 4.17-29.96%) and identified spoligotypes SB0121 (2/3) and SB0134 (1). No macroscopic TB-compatible lesions were observed. To the best of our knowledge, this is the first report of M. bovis in Egyptian mongoose in Spain, as well as the only study that includes spolygotyping in this species. Although the absence of visible lesions suggests a minor role of the Egyptian mongoose in Tuberculosis epidemiology, further research thereon is encouraged.

Occupancy data improves parameter precision in spatial capture-recapture models.

Population size is one of the basic demographic parameters for species management and conservation. Among different estimation methods, spatially explicit capture-recapture (SCR) models allow the estimation of population density in a framework that has been greatly developed in recent years. The use of automated detection devices, such as camera traps, has impressively extended SCR studies for individually identifiable species. However, its application to unmarked/partially marked species remains challenging, and no specific method has been widely used. We fitted an SCR-integrated model (SCR-IM) to stone marten Martes foina data, a species for which only some individuals are individually recognizable by natural marks, and estimate population size based on integration of three submodels: (1) individual capture histories from live capture and transponder tagging; (2) detection/nondetection or "occupancy" data using camera traps in a bigger area to extend the geographic scope of capture-recapture data; and (3) telemetry data from a set of tagged individuals. We estimated a stone marten density of 0.352 (SD: 0.081) individuals/km2. We simulated four dilution scenarios of occupancy data to study the variation in the coefficient of variation in population size estimates. We also used simulations with similar characteristics as the stone marten case study, comparing the accuracy and precision obtained from SCR-IM and SCR, to understand how submodels' integration affects the posterior distributions of estimated parameters. Based on our simulations, we found that population size estimates using SCR-IM are more accurate and precise. In our stone marten case study, the SCR-IM density estimation increased the precision by 37% when compared to the standard SCR model as regards to the coefficient of variation. This model has high potential to be used for species in which individual recognition by natural markings is not possible, therefore limiting the need to rely on invasive sampling procedures.

The effectiveness of conditioned aversion in wolves: Insights from experimental tests.

It has been suggested that conditioned food aversion (CFA) could be a potential non-lethal intervention by which to deter attacks on livestock by large carnivores. CFA occurs when an animal associates the characteristics of a food with an illness, thus rejecting that food in subsequent encounters. CFA can be associated with an artificial odour during conditioning. Despite the debate surrounding the use of this intervention, more studies evaluating the effectiveness of CFA are necessary. We experimentally evaluated the potential of microgranulated levamisole + a vanilla odour cue to induce CFA in captive Iberian wolves (Canis lupus signatus). Four out of the five wolves treated showed an aversion to the meat for a minimum of one month after conditioning. The microgranulated presentation masked the flavour and smell of the levamisole but increased its volume, which may have facilitated its detection by the wolves. We also observed that the strength of the odour played an important role in the aversion extinction. The use of microgranulated levamisole + an odour cue has the potential to be used as an intervention by which to induce aversive conditioning in wolves in the wild, although rigorous field tests are required. We discuss the potential of CFA to deter attacks on livestock by large carnivores.

Protein metabolism and physical fitness are physiological determinants of body condition in Southern European carnivores.

The physiological significance of biometric body condition indices (bBCI) is poorly understood. We hypothesized that bBCI are composite metrics of nutritional physiology, physical fitness and health. To test this hypothesis, we first compared the performance of eight bBCI, using 434 Southern European carnivores from six species as a model system; and then identified, by non-destructive methods, the hematology and serum biochemistry correlates of three selected bBCI. Fulton's K Index, Major Axis Regression Residuals and Scaled Mass Index were the only bBCI insensitive to the effect of sex and age. The most informative physiological parameters in explaining the variation of these bBCI were the albumin (Effect Size (ES) = - 1.66 to - 1.76), urea (ES = 1.61 to 1.85) and total bilirubin (ES = - 1.62 to - 1.79). Hemoglobin and globulins (positive) and cholesterol (negative) were moderately informative (0.9 <|ES|< 1.5). This study shows that most bBCI do not control for the effect of age and sex in Southern European carnivores. Our results support that bBCI are composite measures of physiologic processes, reflecting a positive gradient from protein-poor to protein-rich diets, accompanied by increased physical fitness. Biometric body condition indices allow the integration of ecologically relevant physiological aspects in an easily obtained metric.

Ecological traits and the spatial structure of competitive coexistence among carnivores.

Competition is a widespread interaction among carnivores, ultimately manifested through one or more dimensions of the species' ecological niche. One of the most explicit manifestations of competitive interactions regards spatial displacement. Its interpretation under a theoretical context provides an important tool to deepen our understanding of biological systems and communities, but also for wildlife management and conservation. We used Bayesian multispecies occupancy models on camera-trapping data from multiple sites in Southwestern Europe (SWE) to investigate competitive interactions within a carnivore guild, and to evaluate how species' ecological traits are shaping coexistence patterns. Seventeen out of 26 pairwise interactions departed from a hypothesis of independent occurrence, with spatial association being twice as frequent as avoidance. Association behaviors were only detected among mesocarnivores, while avoidance mainly involved mesocarnivores avoiding the apex predator (n = 4) and mesocarnivore-only interactions (n = 2). Body mass ratios, defined as the dominant over the subordinate species body mass, revealed an important negative effect ( ß^=-0.38;CI95=-0.81to-0.06 ) on co-occurrence probability, and support that spatially explicit competitive interactions are mostly expressed by larger species able to dominate over smaller ones, with a threshold in body mass ratios of ~4, above which local-scale intraguild coexistence is unlikely. We found a weak relationship between pairwise trophic niche overlap and the probability of coexistence ( ß^=-0.19;CI95=-0.58to0.21 ), suggesting that competition for feeding resources may not be a key driver of competition, at least at the scale of our analysis. Despite local-scale avoidance, regional-scale coexistence appears to be maintained by the spatial structuring of the competitive environment. We provide evidence that SWE ecosystems consist of spatially structured competitive environments, and propose that coexistence among near-sized species is likely achieved through the interplay of "facultative" and "behavioral" character displacements. Factors influencing carnivore coexistence likely include context-dependent density and trait-mediated effects, which should be carefully considered for a sound understanding of the mechanisms regulating these communities.

Conditioned food aversion in domestic dogs induced by thiram.

BACKGROUND: The conflict between predators and humans for resources such as game species or livestock is an ancient issue, and it is especially sharp in the case of medium-large wild canids. In order to manage this conflict, lethal control methods are often used, which can sometimes be illegal, such as poisoning. As an alternative, conditioned food aversion (CFA) is a non-lethal method to reduce predation in which animals learn to avoid a given food due to the adverse effects caused by the ingestion of an undetectable chemical compound added to this food. The present study aimed to test thiram as a CFA agent in penned dogs as a first approach to use this substance for reducing the predation conflict associated with wild canids. RESULTS: Thiram, with or without an additional odor cue, produced CFA in penned dogs for more than 2 months. Moreover, thiram seemed to be undetectable and safe after the third ingestion of a 40-60 mg kg-1 dose. Desirable adverse effects, such as vomits, appeared around 1 h after exposure. These characteristics make thiram optimal for its use in predation reduction through CFA. However, individual variability could prevent CFA acquisition by some animals. CONCLUSIONS: Thiram has the potential to be used as a CFA agent in wildlife management and conservation to reduce predation by wild canids. Since thiram produced CFA without the problems of detectability and toxicity caused by other substances, it may be an alternative to lethal control methods used to reduce predation on game, livestock and endangered species. © 2019 Society of Chemical Industry.

Selection of new chemicals to be used in conditioned aversion for non-lethal predation control.

Globally, native predators and scavengers are threatened through the incidence of illegal poisoning due to increasing human-wildlife conflicts. The use of conditioned taste aversion (CTA) may mitigate such conflicts. CTA is a robust learning paradigm that occurs when animals associate a food with a discomfort induced by a chemical, thereby avoiding that food in subsequent encounters. We reviewed the potential of 167 chemical compounds to be used in CTA, considering effects, margin of safety, accessibility, and detectability. After the review, 15 compounds fulfilled the required characteristics, but only five (thiabendazole, thiram, levamisole, fluconazole and fluralaner) were finally selected to be tested in CTA assays with dogs. Of the tested compounds, thiabendazole, thiram and levamisole caused target food rejection by dogs and reduced the time spent eating during post-conditioning. However, despite being microencapsulated, levamisole appeared to be detectable by dogs, whereas thiram and thiabendazole were not. Fluconazole and fluralaner did not produce any CTA effect. Thiabendazole, thiram and levamisole can therefore induce CTA, and thus are potential candidates as aversive compounds for wildlife management. Thiram is an undetectable, relatively safe and accessible compound that can induce CTA in canids, and opens new possibilities to develop methods of non-lethal predation control.

Generalized spatial mark-resight models with incomplete identification: An application to red fox density estimates.

The estimation of abundance of wildlife populations is an essential part of ecological research and monitoring. Spatially explicit capture-recapture (SCR) models are widely used for abundance and density estimation, frequently through individual identification of target species using camera-trap sampling.Generalized spatial mark-resight (Gen-SMR) is a recently developed SCR extension that allows for abundance estimation when only a subset of the population is recognizable by artificial or natural marks. However, in many cases, it is not possible to read the marks in camera-trap pictures, even though individuals can be recognized as marked. We present a new extension of Gen-SMR that allows for this type of incomplete identification.We used simulation to assess how the number of marked individuals and the individual identification rate influenced bias and precision. We demonstrate the model's performance in estimating red fox (Vulpes vulpes) density with two empirical datasets characterized by contrasting densities and rates of identification of marked individuals. According to the simulations, accuracy increases with the number of marked individuals (m), but is less sensitive to changes in individual identification rate (δ). In our case studies of red fox density estimation, we obtained a posterior mean of 1.60 (standard deviation SD: 0.32) and 0.28 (SD: 0.06) individuals/km2, in high and low density, with an identification rate of 0.21 and 0.91, respectively.This extension of Gen-SMR is broadly applicable as it addresses the common problem of incomplete identification of marked individuals during resighting surveys.

Females know better: Sex-biased habitat selection by the European wildcat.

The interactions between animals and their environment vary across species, regions, but also with gender. Sex-specific relations between individuals and the ecosystem may entail different behavioral choices and be expressed through different patterns of habitat use. Regardless, only rarely sex-specific traits are addressed in ecological modeling approaches. The European wildcat (Felis silvestris silvestris) is a species of conservation concern in Europe, with a highly fragmented and declining distribution across most of its range. We assessed sex-specific habitat selection patterns for the European wildcat, at the landscape and home range levels, across its Iberian biogeographic distribution using a multipopulation approach. We developed resource selection functions in a use-availability framework using radio-telemetry data from five wildcat populations. At the landscape level, we observed that, while both genders preferentially established home ranges in areas close to broadleaf forests and far from humanized areas, females selected mid-range elevation areas with some topographic complexity, whereas males used lowland areas. At the home range level, both females and males selected areas dominated by scrublands or broadleaf forests, but habitat features were less important at this level. The strength of association to habitat features was higher for females at both spatial levels, suggesting a tendency to select habitats with higher quality that can grant them enhanced access to shelter and feeding resources. Based on our results, we hypothesize that sex-biased behavioral patterns may contribute to the resilience of wildcats' genetic integrity through influencing the directionality of hybridization with domestic cats. Our study provides information about European wildcats' habitat use in an Iberian context, relevant for the implementation of conservation plans, and highlights the ecological relevance of considering sex-related differences in environmental preferences.

Revisiting food-based models of territoriality in solitary predators.

Food availability is considered a major factor determining spacing behaviour in territorial species, especially for females. Theoretically, spatial overlap (considered the opposite of territoriality) and food availability are related in a nonlinear manner (hypothesized inverted-U function), with high overlap levels at the extremes of a food availability gradient and low overlap at intermediate levels of this gradient. Similar patterns are expected for encounter frequencies owing to its expected correlation with spatial overlap. However, these predictions have rarely been tested in highly structured social systems on a broad gradient of food availability, which implicitly requires experimental manipulation. We test these predictions in a solitary, territorial and trophic specialist, the Iberian lynx Lynx pardinus, taking advantage of a three-decade data set of spatial behaviour in different scenarios of food availability (i.e. rabbit density). In contrast with expectations, home range overlap among resident females was low (median overlap index = 0.08, range 0-0.57) and core area overlap was nearly nil (median overlap index = 0, range 0-0.22) throughout the entire gradient of prey availability. Furthermore, spatial associations between pairs of females were negligible regardless marked variation in prey availability. Therefore, we did not find support for a model of flexible lynx territoriality driven by food availability. Our results suggest that the exclusive use of space in the Iberian lynx was not related to food. Lack of influence of prey availability on lynx territoriality may be adaptive to cope with the consequences of frequent drought-induced periods of prey scarcity or other disturbance typically affecting wild rabbit populations in Mediterranean environments. Thus, lynx would adopt an obstinate strategy of territoriality that consists in defending exclusive areas across a broad range of resource availability ensuring an exclusive access to the minimum amount of prey necessary for survival and eventually reproduction even during periods of prey scarcity. However, we found signs that territoriality was influenced by lynx density in a nonlinear fashion. Our results suggest the occurrence of population regulation through territoriality in this species.

Field experimental vaccination campaigns against myxomatosis and their effectiveness in the wild.

We conducted a field experiment in SW Spain to test the efficacy of a myxomatosis vaccine, a viral disease strongly affecting wild rabbit populations, by assessing individual survival and antibody seroprevalence of monthly live-trapped, vaccinated (N=466) and unvaccinated (N=558) juvenile wild rabbits, between April and October 2007. Eight percent of all juveniles caught from April to June showed maternal antibodies against myxomatosis, whereas all animals were seropositive to the disease after the outbreak. Juveniles vaccinated before the outbreak showed 17% higher survival (31% vs. 14%) and an increased mortality probability of 8% after the outbreak. Results suggest that only a costly and systematic vaccination performed before the annual myxomatosis outbreak, would improve the survival of juvenile rabbits, a premise not always accomplished that compromises its efficacy in the field.

The impact of native competitors on an alien invasive: temporal niche shifts to avoid interspecific aggression?

The American mink, Neovison vison, is an established, alien invasive species in the United Kingdom that originally colonized the country at a time when two native mustelids (otters, Lutra lutra, and polecats, Mustela putorius) were largely absent. Both of these species are now recovering their populations nationally. We compared the relative abundance and the behavior of mink in the 1990s and in the 2000s in an area of southern England where both otters and polecats were absent in the 1990s but reappeared in the intervening years. We found that mink were still abundant in the 2000s in the presence of otters and polecats, but that they appeared to have altered some aspects of their behavior. In accordance with previous studies, we found that mink consumed fewer fish in the presence of otters. We also found that mink were predominantly nocturnal in the 1990s (in the absence of competitors) but were predominantly diurnal in the 2000s (in the presence of competitors). We hypothesize that this temporal shift may be an avoidance mechanism allowing the coexistence of mink with the otter and the polecat, although we are unable to attribute the shift to one or the other species. We also found that mink in the presence of competitors weighed less but remained the same size, suggesting the possibility of a competitor-mediated decline in overall body condition. This is one of very few field studies demonstrating a complete temporal shift in apparent response to competitors. The implications of this study are that recovering otter populations may not lead to significant and long-term reductions in the number of invasive mink in the United Kingdom as has been suggested in the media, although we cannot exclude the possibility of a decline in mink in the longer-term.

Key role of European rabbits in the conservation of the Western Mediterranean basin hotspot.

The Mediterranean Basin is a global hotspot of biodiversity. Hotspots are said to be experiencing a major loss of habitat, but an added risk could be the decline of some species having a special role in ecological relationships of the system. We reviewed the role of European rabbits (Oryctolagus cuniculus) as a keystone species in the Iberian Peninsula portion of the Mediterranean hotspot. Rabbits conspicuously alter plant species composition and vegetation structure through grazing and seed dispersal, which creates open areas and preserves plant species diversity. Moreover, rabbit latrines have a demonstrable effect on soil fertility and plant growth and provide new feeding resources for many invertebrate species. Rabbit burrows provide nest sites and shelter for vertebrates and invertebrates. In addition, rabbits serve as prey for a number of predators, including the critically endangered Iberian lynx (Lynx pardinus) and Spanish Imperial Eagle (Aquila adalberti). Thus, the Mediterranean ecosystem of the Iberian Peninsula should be termed "the rabbit's ecosystem." To our knowledge, this is the first empirical support for existence of a multifunctional keystone species in a global hotspot of biodiversity. Rabbit populations have declined drastically on the Iberian Peninsula, with potential cascading effects and serious ecological and economic consequences. From this perspective, rabbit recovery is one of the biggest challenges for conservation of the Mediterranean Basin hotspot.

Exposure to disease agents in the endangered Iberian lynx (Lynx pardinus).

The Iberian lynx (Lynx pardinus) is the most endangered felid species in the world. Lynx populations have decreased dramatically in size and distribution in the last four decades, thus becoming increasingly vulnerable to catastrophic events such as epizooties. From 1989 to 2000, serum samples were obtained from 48 free-ranging lynx captured in the Doñana National Park (DNP, n = 31) and mountains of Sierra Morena (SM, n = 17) in southern Spain. Samples were tested for antibodies against Toxoplasma gondii, feline herpesvirus 1 (FHV-1), feline calicivirus (FCV), feline/canine parvovirus (FPV/CPV), feline coronavirus, feline immunodeficiency virus (FIV), feline leukaemia virus and canine distemper virus (CDV) and for FeLV p27 antigen, to document baseline exposure levels. Antibodies against T. gondii were detected in 44% of lynx, with a significantly greater prevalence in DNP (61%) than in SM (12%). In DNP, prevalence was significantly higher in adult (81%) than in juvenile and sub-adult (41%) lynx, but no such difference was observed in SM. Low prevalences (≤11%) of minimally positive titres were found for FHV-1, FCV and FPV/CPV. This, combined with the lack of evidence for exposure to CDV, FIV and FeLV, suggests that these lynx populations are naïve and might be vulnerable to a disease outbreak in the future. Because of the reduced size of lynx populations, the documented low level of genetic variation (particularly in the DNP population) coupled with the recently documented state of immune depletion in a majority of necropsied lynx, it is important to better understand the threat and potential impact that disease agents might pose for the conservation of this endangered species. Future surveillance programs must include possible disease reservoir hosts such as domestic cats and dogs and other wild carnivores.

Effects of matrix heterogeneity on animal dispersal: from individual behavior to metapopulation-level parameters.

Mounting theoretical and empirical evidence shows that matrix heterogeneity may have contrasting effects on metapopulation dynamics by contributing to patch isolation in nontrivial ways. We analyze the movement properties during interpatch dispersal in a metapopulation of Iberian lynx (Lynx pardinus). On a daily temporal scale, lynx habitat selection defines two types of matrix habitats where individuals may move: open and dispersal habitats (avoided and used as available, respectively). There was a strong and complex impact of matrix heterogeneity on movement properties at several temporal scales (hourly and daily radiolocations and the entire dispersal event). We use the movement properties on the hourly temporal scale to build a simulation model to reconstruct individual dispersal events. The two most important parameters affecting model predictions at both the individual (daily) and metapopulation scales were related to the movement capacity (number of movement steps per day and autocorrelation in dispersal habitat) followed by the parameters representing the habitat selection in the matrix. The model adequately reproduced field estimates of population-level parameters (e.g., interpatch connectivity, maximum and final dispersal distances), and its performance was clearly improved when including the effect of matrix heterogeneity on movement properties. To assume there is a homogeneous matrix results in large errors in the estimate of interpatch connectivity, especially for close patches separated by open habitat or corridors of dispersal habitat, showing how important it is to consider matrix heterogeneity when it is present. Movement properties affect the interaction of dispersing individuals with the landscape and can be used as a mechanistic representation of dispersal at the metapopulation level. This is so when the effect of matrix heterogeneity on movement properties is evaluated under biologically meaningful spatial and temporal scales.