Aonyx Capensis Research Articles

Method development: Assigning sex to African clawless otter spraints and assessing stability of faecal androgen and progestagen metabolites post-defaecation

Monitoring reproductive physiology in wildlife can be a useful tool for assessing population dynamics for conservation and management purposes. Utilizing non-invasive approaches for this, such as quantifying reproductive hormone metabolites from faeces, can be challenging when defaecation events are not observed, or when cryptic species like African clawless otters (Aonyx capensis) are involved. Additionally, test systems for quantifying hormone metabolites in a species for the first time must first be reliably validated prior to use. Our results indicate that Epiandrosterone and Progesterone EIAs are most suitable for determining fAM and fPM concentrations in African clawless otter spraints. The fAM:fPM ratio and respective thresholds are more reliable in sex identification compared to the separate use of individual hormone classes. Sex-related hormone metabolite concentrations remained comparable for up to 12hrs post-defaecation in both sexes.•We screened two androgen and two progestagen enzyme-immunoassays (EIAs) for suitability and reliable quantification of faecal androgen metabolites (fAM) and faecal progestagen metabolites (fPM) in African clawless otters.•We assessed whether the ratio of fAM:fPM concentrations can be used to assign sex to faecal samples from unknown individuals.•We tested the stability of fAM and fPM concentrations post-defaecation to determine the effects of environmental exposure and bacterial metabolism.

Latrine site selection by African clawless otters, Aonyx capensis, and their behavior during latrine visitations.

Latrine sites are used as areas for the deposition of scent-containing excretions and play important roles in intraspecific olfactory communication, territoriality, sexual attraction, and defense behaviors of many mammals. African clawless otters (Aonyx capensis) likely use latrine sites as primary areas for scent marking and scent communication but no studies to date have investigated their potential role or site selection. We assessed latrine site selection at 2 spatial scales (micro- and macroscale) and recorded behaviors via camera trap recordings. Thirty-eight latrine sites were identified and assessed at 2 locations in Mtunzini on the north coast of KwaZulu-Natal, South Africa (uMlalazi Nature Reserve and Zini Fish Farm) during the months of August to November 2021. Latrine sites were identified through several intensive surveys, while we characterized nonselected sites through a systematic sampling approach. Latrine and control sites were inventoried along a 52-m buffer around all water bodies in both study areas. At each site we measured a series of potential environmental predictors, including horizontal and vertical vegetation cover, surface slope, and averaged wind speeds for days classified as relatively wind-still and relatively windy. To assess the relative role of various environmental predictors, we used a binomial generalized linear model resource selection function to model both spatial scales of latrine site selection. The majority of latrine sites were located at the ecotone between 2 vegetation units or between a vegetation unit and a water source. At a macroscale, latrine sites were associated with areas containing little vegetative substrate cover and minimal canopy cover. The top-ranked models at the microscale also indicated that latrine sites were characterized as occurring in open areas with less canopy and horizontal cover and on flatter areas that are relatively protected against wind. The most common behaviors recorded at 3 latrine sites were the "jiggle dance" (42%) and sniffing (29%). We hypothesize that otters evaluate numerous environmental parameters to enhance the functionality of latrine sites. For example, sites with little vegetative cover may increase the conspicuousness of latrines to conspecifics, while areas exposed to less wind likely aid in the retention of scent. Ongoing research is characterizing the behaviors of otters around latrines and chemical signatures of latrine sites in an effort to facilitate interpretation of their social function to African clawless otters.

Stakeholder perceptions of human–predator conflict in the South African fly‐fishing industry

AbstractHuman–wildlife conflict in African aquaculture and fisheries is poorly understood. We investigated this conflict through a questionnaire aimed at owners and managers of fly‐fishing properties in South Africa. While perceptions of losses varied, all respondents reported losses to predators. Resulting mitigation measures, including lethal control, were employed mostly against cormorants (Phalacrocorax spp.) and otters (Aonyx capensis and Hydrictis maculicollis). Given that fly‐fishing properties potentially provide valuable habitat for protected species such as otters, our results highlight a need for improved mitigation measures and exploring alternative options of potentially generating income from tourism associated with the presence of charismatic predators.

The extirpation of medium and large mammal species from the Ehotilé Islands National Park, south-eastern Côte d’Ivoire

Abstract In West Africa, high deforestation rates and poaching have induced dramatic declines of mammal’s populations and local extinctions. Due to their isolation, island species are more vulnerable than mainland species. The premises of that scenario are perceptible in the Ehotilé Islands National Park, south-eastern Côte d’Ivoire, but have not been documented. This study aimed to update the diversity and conservation status of medium and large mammals in that protected area. Several surveys were conducted between 2019 and 2021, using ethno-zoological interviews and individual surveys with local populations, as well as reconnaissance walks and camera trapping to collect data on the presence or absence of mammals. From interviews with local populations and literature review, a list of 27 species of mammals that were potentially present in the park in the past was established. Most “lost” species are large mammals, especially primates that are globally threatened. A total of 11 species were pictorially identified, including two Near threatened species (Aonyx capensis and Hydrictis maculicollis) and one Vulnerable species (Cercopithecus lowei). The study confirms a trend of population decline and the erosion of mammal diversity in the park, hence highlighting the need for urgent conservation actions.

Phylogenomics of the world’s otters

Comparative whole-genome analyses hold great power to illuminate commonalities and differences in the evolution of related species that share similar ecologies. The mustelid subfamily Lutrinae includes 13 currently recognized extant species of otters,1-5 a semiaquatic group whose evolutionary history is incompletely understood. We assembled a dataset comprising 24 genomes from all living otter species, 14 of which were newly sequenced. We used this dataset to infer phylogenetic relationships and divergence times, to characterize patterns of genome-wide genealogical discordance, and to investigate demographic history and current genomic diversity. We found that genera Lutra, Aonyx, Amblonyx, and Lutrogale form a coherent clade that should be synonymized under Lutra, simplifying the taxonomic structure of the subfamily. The poorly known tropical African Aonyx congicus and the more widespread Aonyx capensis were found to be reciprocally monophyletic (having diverged 440,000 years ago), supporting the validity of the former as a distinct species. We observed variable changes in effective population sizes over time among otters within and among continents, although several species showed similar trends of expansions and declines during the last 100,000 years. This has led to different levels of genomic diversity assessed by overall heterozygosity, genome-wide SNV density, and run of homozygosity burden. Interestingly, there were cases in which diversity metrics were consistent with the current threat status (mostly based on census size), highlighting the potential of genomic data for conservation assessment. Overall, our results shed light on otter evolutionary history and provide a framework for further in-depth comparative genomic studies targeting this group.

The Determinants of Mesocarnivore Activity Patterns in Highveld Grassland and Riparian Habitats

Despite the diversity of mesocarnivores and the broad geographic ranges of these species, our understanding of their behaviour and ecology at multi-species and community levels is limited. Our study was conducted between April and mid-July 2015 and used data collected over 105 days from 39 camera traps to quantify activity patterns of sympatric mesocarnivores in riparian and grassland habitats of Telperion Nature Reserve, South Africa. A total of 13 mesocarnivore species were detected within this relatively small (∼7350 ha) reserve. Sufficient records (≥10 records) were obtained for rusty-spotted genet (Genetta maculata), black-backed jackal (Canis mesomelas), otter species (African clawless otter, Aonyx capensis, and spotted-necked otter, Hydrictis maculicollis), serval (Leptailurus serval ), slender mongoose (Galerella sanguinea), yellow mongoose (Cynictis penicillata) and marsh mongoose (Atilax paludinosus). Generalized linear models were used to investigate whether species ID, temperature, vegetation characteristics or moon phase best predicted temporal activity. To assess which species had the highest potential for competitive interaction, we also quantified the coefficient of activity overlap. Our results show that species ID and temperature were the best predictors of mesocarnivore activity. Slender and yellow mongooses displayed the highest coefficient of activity overlap (0.90), followed by marsh mongoose and rusty-spotted genet (0.80), and serval and rusty-spotted genet (0.79). These species are likely to have the highest potential for competitive interactions, but preferences for different vegetation characteristics and variations in the estimated relative abundance may point to coexistence through spatial and fine-scale temporal partitioning. The other species exhibited lower coefficients of activity overlap with each other, suggesting they may coexist through temporal partitioning of resources.

The diving behavior of African clawless and spotted-necked otters in freshwater environments

Abstract Understanding the diving behavior of semiaquatic mammals, particularly in relation to estimated aerobic dive limits and diet, is important to understand their adaptability and potential vulnerability to changes in prey type and distribution. The diving behavior of African clawless otters, Aonyx capensis, and spotted-necked otters, Hydrictis maculicollis, is poorly known, and no estimates of their dive performance in relation to targeted prey and calculated dive limits have been reported previously for freshwater environments. We investigated the diving behavior of both these otter species in freshwater environments within South Africa through video recordings of direct observations and subsequent video analyses where dive and recovery durations and dive function were recorded. African clawless otters were found to perform longer dives (mean ± SD = 26.9 ± 12.2 s), compared to spotted-necked otters (8.5 ± 7.6 s). African clawless otters showed substantial variation in dive durations, with the shortest dives sometimes lasting < 5 s, and the longest recorded dive being 70 s. The majority of spotted-necked otter dives lasted < 10 s, with the shortest recorded dive lasting 0.66 s and the longest recorded dive lasting 50.9 s. Spotted-necked otters performed different dive types that were evidently dependent on prey targeted, with dives targeting crabs (16.10 ± 1.91 s) being longer than dives targeting rainbow trout, Oncorhynchus mykiss (5.58 ± 0.17 s). The theoretical dive durations of African clawless otters were exceeded during play dives, while spotted-necked otters sometimes exceeded their theoretical dive durations when performing successful foraging dives. The results of this study suggest that spotted-necked otters can vary behavior in relation to prey and exceed theoretical dive duration during successful foraging dives to maximize the net rate of energy gain. Furthermore, when considering known individual-level dietary specialization and plasticity in these species, it may be predicted that dive behaviors are likely to vary substantially among individuals, and in relation to prey availability and localized habitat conditions.

Stakeholders’ perceptions of mammal occurrence and abundance on agricultural properties bordering the Boland Mountain Complex, South Africa

The encroachment of agricultural landscapes on natural ecosystems poses a significant threat to native wildlife persistence. In the Boland Mountain Complex (BMC), the presence of mammals was well documented in the 20th century, but an updated account is lacking. This study relied on Local Ecological Knowledge (LEK) to elucidate perceived medium- to large-sized (>300 g) mammal occurrences, distribution ranges, and relative abundance on private agricultural properties adjacent to protected areas in the BMC. In total, 30 mammal species were reported to be present, and inverse distance weighted (IDW) interpolations were created for species that had more than five independent citations (n = 24), to display reported relative abundance-distributions beyond the scope of the sampled locations. Species with severely isolated relative abundance-distribution profiles (e.g. leopard, Panthera pardus, Cape clawless otter, Aonyx capensis and honey badger, Mellivora capensis), species with low overall incidence (e.g. aardwolf, Proteles cristata and Smith’s red rock rabbit, Pronolagus rupestris), and non-native species with high incidences (e.g. feral dog, Canis familiaris and feral pig, Sus scrofa) were identified, and can now be prioritised further for future research and conservation efforts within the BMC region.

Increased population density and behavioural flexibility of African clawless otters (Aonyx capensis) in specific anthropogenic environments

Land transformation for anthropogenic use is the leading cause of species decline globally. However, few species are able to succeed in anthropogenically disturbed environments. African clawless otters (Aonyx capensis) occur in a wide variety of habitats, and thus are good model species to investigate animal adaptation to anthropogenic environments. Therefore, we aimed to estimate and compare population densities, group size, and activity time of African clawless otters occurring in a transformed area, Millstream Farm, and two natural areas, Verloren Vallei Nature Reserve and Cobham Nature Reserve. Camera trap arrays, consisting of between 18, 27 and 24 cameras, were placed on all three sites, recording otter presence for a total of 2439 camera days. Using random encounter models, we estimated that the transformed area had the highest density of African clawless otters (8.2 ± 2.3 km−2), compared to otter densities at Verloren Vallei and Cobham Nature Reserve, South Africa, (natural areas) with estimated densities of 0.7 ± 0.2 km−2 and 2.1 ± 0.6 km−2 respectively. We found a significant difference (p = 0.007) between group sizes in the transformed area (detections = 112; group size range = 1–5) and natural areas (detections = 29; group size range = 1–3). Furthermore, there was a significant difference in otter activity time (p = 0.033, activity overlap = 66.5 ± 8.33%) between Verloren Vallei Nature Reserve and the transformed area at Millstream Farm. This study illustrates how African Clawless otters exhibit behavioural plasticity in order to exploit a resource-rich anthropogenic environment.

Monitoring the effects of land transformation on African clawless otters (Aonyx capensis) using fecal glucocorticoid metabolite concentrations as a measure of stress.

In a time of increasing environmental change caused by anthropogenic disturbance, there is a greater need to understand animal adaptations to manmade environments. In this regard, the measurement of stress-related endocrine markers provides a useful tool to examine the impact of environmental challenges and the physiological consequences for wildlife occupying such space. The aims of the present study were to validate fecal glucocorticoid metabolite (fGCM) concentrations as a measure of stress using samples from a male African clawless otter (Aonyx capensis; n = 1) and to compare fGCM concentrations of otters occurring in a transformed and in 2 natural areas in South Africa. From the 5 different enzyme-immunoassays (EIA) tested, a cortisol and oxoetiocholanolone (measuring 11,17 dioxoandrostanes) EIA revealed the highest response (74% and 48% increase, respectively) 30 and 24 hours after a stress event (translocation of a captive individual as part of its rehabilitation prior to release), respectively. For both EIAs, fGCM concentrations were comparable for samples collected up to 3 h post-defecation. Using the cortisol EIA for subsequent analyses, fGCM concentrations of animals from the transformed area (n = 20; mean [± SD]: 0.468 [± 0.539] µg/g dry weight [DW]) were significantly higher (P = 0.013) than those from otters in the natural areas (n = 17; 0.242 [± 0.226] µg/g DW). These preliminary results suggest that African clawless otters may have increased adrenocortical activity that could be due to conditions linked to living in a transformed environment.

The diet of spotted-necked otters foraging in trout-stocked waters in Mpumalanga, South Africa

Human-wildlife conflict is likely to increase as urbanisation increases. African clawless otters, Aonyx capensis, and spotted-necked otters, Hydrictis maculicollis, are illegally persecuted for their perceived role in reducing trout in artificially stocked habitats in South Africa. The diet of African clawless otters has been investigated, but little is known about the diet of spotted-necked otters in these habitats. Using stable isotope techniques, we investigated the diet of spotted-necked otters occupying habitats artificially stocked with trout. Stable isotope analyses revealed that the diet of spotted-necked otters included equal proportions of crab and trout followed by frog. Diet was found to vary between, as well as within, individuals suggesting individual dietary plasticity. Temporal variation in foraging areas was evident for some otters. These results suggest that individual animals specialise on trout when available. However, this was not consistent between individuals. The resulting conflict with freshwater fisheries may, therefore, be primarily due to individual animals adapting to diets consisting largely of farmed trout. The extent of spotted-necked otter influence on stocked trout, however, needs further investigation.

Investigation of ancient DNA to enhance natural history museum collections: misidentification of smooth-coated otter (Lutrogale perspicillata) specimens across multiple museums

Historical and modern natural museum collections are storehouses of extraordinary value for scientific research in a wide range of fields. Recent advances in molecular biotechnology (e.g., next generation genomics) have increased the range of collection material employable for DNA-based analyses to unprecedented levels. Nevertheless, the value of museum specimens strictly depends on reliability of data associated with them. We report on investigations of ancient DNA from specimens of smooth-coated otter (Lutrogale perspicillata, Mustelidae), the largest otter species living in Asia, in US and European mammal collections. Mitochondrial DNA Cytochrome-b gene sequencing proved that the studied specimens were not the expected taxon. Indeed, they actually belonged to three different species, namely the Asian small-clawed (Aonyx cinereus), Eurasian (Lutra lutra) and African clawless (Aonyx capensis) otters. This represents the first record of mustelid misidentification from museum collections. Detection of errors can be extremely difficult when based only on collectors’ notes and data. Hence, we warn scientists involved in otter research about potential challenges when dealing with museum specimens. We recommend curators pursue a multidisciplinary approach, including DNA analyses, to accurately catalogue the resources under their management and uphold the value of biodiversity information.

Genetic diversity of African clawless otters (Aonyx capensis) occurring in urbanised areas of Gauteng, South Africa

Genetic diversity is the basis of the evolutionary potential of species to respond to environmental changes. However, restricting the movement of species can result in populations becoming less connected which can reduce gene flow and can subsequently result in a loss of genetic diversity. Urban expansion can lead to the fragmentation of habitats which affects the ability of species to move freely between areas. In this study, the genetic diversity of the African clawless otter (Aonyx capensis) in Gauteng (South Africa) was assessed using non-invasive sampling techniques. DNA was extracted from spraint (faecal) samples collected along nine rivers and genotyped using 10 microsatellites to assess population structure and genetic diversity. Samples were grouped based on locality and by catchment to determine whether isolated subpopulations exist. Genetic diversity of A. capensis in Gauteng was found to be low (mean observed heterozygosity (Ho)=0.309). Analysis of genetic structure provides support for the otter populations being panmictic with high gene flow between populations from different rivers. Results from the study indicate that the movement of A. capensis is not affected by physical barriers in urbanised areas. However, because the genetic diversity of the species in the study area is low, these animals may not be able to cope with future environmental changes.
 Significance:
 
 Genetic structure analysis of the sampled Gauteng otter population indicates the population is panmictic; however, a low level of genetic diversity in this population has also been identified and may affect how the population copes with future environmental changes.
 Physical restrictions in urbanised areas do not appear to be affecting movement of the species.

Plasticity and specialisation in the isotopic niche of African clawless otters foraging in marine and freshwater habitats

Individual-level behavioural plasticity resulting from differences in environmental conditions is prevalent in many organisms and may result in phenomena such as dietary- or habitat specialisation. The isotopic niche of African clawless otters, Aonyx capensis, occupying different habitats was investigated with the use of stable isotope techniques. Stable isotope analyses revealed that African clawless otter isotopic niche varied between, as well as within, individuals and varied when compared to conspecifics occupying different habitats. Some otters varied their isotopic niche and foraging areas temporally, whilst others did not. The isotopic niche of African clawless otters in a coastal habitat overlapped substantially with previous reports on otter diet, but illustrated that otters eat more shark and molluscs than previously estimated. In freshwater habitats, not all otters had trout in their isotopic niche, although this prey item was abundantly available in the study area. Our results suggest that the African clawless otters can exhibit substantial behavioural plasticity. Such evident adaptability is likely to benefit otters and allow for extended use of non-pristine environments affected by human disturbance when sufficient quantities of prey remain available.

Limited Animal-Facilitated Nutrient Transfer across an Aquatic–Terrestrial Interface in a Southern African Savanna

Animal-mediated nutrient transfer facilitates nutrient cycling in marine, freshwater and terrestrial ecosystems via the deposition of aquatically-derived nutrients such as nitrogen (N) and carbon (C). This mode of nutrient transfer has not been studied in southern African river systems. We investigated nutrient deposition associated with defecation, urination, and scent-marking at latrine sites of a semi-aquatic predator species (African clawless otters Aonyx capensis) in a riparian zone of a Bankenveld savanna ecosystem. We provide a comparison of stable nitrogen isotopes (δ15N) measured in soil, vegetation and faecal material, between latrine and paired control sites. Latrine sites displayed higher δ15N values than the paired non-latrine sites, but only at the area of direct deposition (soil surfaces). This effect dissipated as the distance from direct contact increased, while no significant difference in δ15N values was detected for sub-surface soil samples. Plants displayed varying trends of enriched δ15N values between the latrine and paired control sites. These results suggest that several factors and processes such as leaching, mineralization, ammonia volatilization, and nitrogen acquisition influence the nutrient availability within latrine-soil-vegetation systems in riparian zones of African savanna ecosystems.

Widespread anticoagulant poison exposure in predators in a rapidly growing South African city

Anticoagulant rodenticides (ARs) are used worldwide to control rodent populations. ARs bioaccumulate across trophic levels and threaten non-target wildlife. We investigated the prevalence of AR exposure in seven predator species in the rapidly developing Greater Cape Town region of South Africa – a mosaic of natural, urban, and agricultural areas within a global biodiversity hotspot. We focused sampling on caracals (Caracal caracal, n = 28) as part of a larger caracal ecology study, but also opportunistically sampled Cape Clawless otters (Aonyx capensis, n = 9), large-spotted genets (Genetta tigrina, n = 4), honey badger (Mellivora capensis, n = 1), water mongoose (Atilax paludinosus, n = 1), small gray mongoose (Galerella pulverulenta, n = 1), and Cape Eagle owl (Bubo capensis, n = 1). We tested livers from all species, and blood from ten caracals, for eight AR compounds to assess prevalence and amount of exposure for each compound. We used generalized linear models to test spatial, demographic, and seasonal risk factors for ten measures of AR exposure in caracals. We detected at least one of the four most toxic AR compounds in six species. Exposure was high for caracals (92%) and all species combined (81%). For caracals, proximity to vineyards was the most important AR exposure risk factor. Vineyards in Cape Town do not use ARs to protect their vines but do host commercial hospitality structures where ARs are used. Vineyards may thus link caracals that forage within vineyards to the rat poisons used in and around their commercial structures. Residue levels were unexpected in large-spotted genets and Cape Clawless otters, suggesting invertebrate vectors. ARs may present a cryptic threat to populations already vulnerable to increasing habitat loss, vehicle collisions, poachers and fire. Targeted mitigation should include a mix of environmentally responsible policies that reduce AR use, particularly in areas near wildlife habitat.

Can opportunistic citizen sightings assist in the monitoring of an elusive, crepuscular mammal in an urban environment?

Central to appropriate wildlife management is an effective monitoring program. Monitoring wildlife in urban environments offers unique challenges in the form of barriers, prohibited access and crime. It also, however, provides a unique opportunity to enlist residential communities in collecting data on distribution of a number of species. Opportunistic sightings data has its flaws, including the lack of data on species absences, and unequal sampling effort. Yet these data may still provide reliable information on the distribution of species and complement localized, hypothesis driven research. Where possible opportunistic sightings data should be validated against traditional methods to determine their value for long term monitoring programmes. We use Maxent to model citizen-reported sightings to determine whether sightings of Cape clawless otters (Aonyx capensis) can complement standardized river occupancy surveys to monitor an elusive, widely distributed species living within a fragmented urban/natural matrix. The drivers of otter presence and the predicted distribution of otters modelled from citizen sightings mirrored that provided by previously published results based on occupancy models in the same system, and highlighted further areas of suitable otter habitat and routes for dispersal. Involving citizens in the monitoring of the urban otter population complemented standardized occupancy surveys and provided additional benefits. In addition to alleviating the pressure on local authorities to allocate resources to routine monitoring, citizen involvement provides an opportunity to gather supplementary data on behaviour and/or threats to the species; shed light on the potential dispersal routes, and promote awareness and encourage coexistence with urban adapted wildlife.

Complete mitochondrial genomes of the African clawless (Aonyx capensis) and spotted necked (Hydrictis maculicollis) otter: structure, annotation, and interspecies variation

Otters are flagship species for pristine habitats and their southernmost distribution in Africa includes two species; Aonyx capensis and Hydrictis maculicollis. Here, we present novel full mitochondrial genomes of these otter species. The comparable mitogenomes consist of 36 genes including 13 protein-coding genes, 2 ribosomal RNAs, and 22 tRNAs including a hypervariable region. Only 19 out of the 36 genes showed some level of variation between species with the smallest being trnV (68 bp difference) and the biggest being nad5 (1830 bp difference). Such variations may provide guidance in selecting gene regions during marker development for phylogenetic assessments.

A mass mortality of fishes caused by receding water levels in the vegetated littoral zone of the West Kleinemonde Estuary, South Africa

On 15 November 2017 the mouth of the West Kleinemonde Estuary breached following heavy catchment rains and increased river flow. The water level in the estuary following mouth opening decreased by 1.65 m within 24 h, resulting in an almost complete draining of the littoral zone where large beds of the aquatic macrophyte Ruppia cirrhosa and mats of the associated filamentous algae were present. As the water depth within the plant beds decreased, the macrophytes, together with the algal filaments, created an increasingly dense mat, trapping fish that were resident, foraging or passing through the littoral zone. By 16 November 2017 large numbers of fishes belonging to at least 20 species were trapped in pools and depressions within the littoral, as well as within the R. cirrhosa beds and filamentous algal mats in the lower reaches of this system. Other affected taxa included crustaceans, especially isopods, and large numbers of small bivalves attached to macrophyte vegetation. Beneficiaries of the fish kill, in terms of unexpected food availability, included a variety of piscivorous bird species and the Cape clawless otter Aonyx capensis. This is the first documented account of a diverse species fish kill associated with estuary mouth breaching.

More than range exposure: Global otter vulnerability to climate change

Climate change impact on species is commonly assessed by predicting species' range change, a measure of a species' extrinsic exposure. However, this is only one dimension of species' vulnerability to climate change. Spatial arrangement of suitable habitats (e.g., fragmentation), their degree of protection or human disturbance, as well as species' intrinsic sensitivity, such as climatic tolerances, are often neglected. Here, we consider components of species' intrinsic sensitivity to climate change (climatic niche specialization and marginality) together with components of extrinsic exposure (changes in range extent, fragmentation, coverage of protected areas, and human footprint) to develop an integrated vulnerability index to climate change for world's freshwater otters. As top freshwater predators, otters are among the most vulnerable mammals, with most species being threatened by habitat loss and degradation. All dimensions of climate change exposure were based on present and future predictions of species distributions. Annual mean temperature, mean diurnal temperature range, mean temperature of the wettest quarter, precipitation during the wettest quarter, and precipitation seasonality prove the most important variables for otters. All species are vulnerable to climate change, with global vulnerability index ranging from −0.19 for Lontra longicaudis to −36,9 for Aonyx congicus. However, we found that, for a given species, climate change can have both positive and negative effects on different components of extrinsic exposure, and that measures of species' sensitivity are not necessarily congruent with measures of exposure. For instance, the range of all African species would be negatively affected by climate change, but their different sensitivity offers a more (Hydrictis maculicollis, Aonyx capensis) or less (Aonyx congicus) pessimistic perspective on their ability to cope with climate change. Also, highly sensitive species like the South-American Pteronura brasiliensis, Lontra provocax, and Lutra perspicillata might face no exposure to climate change. For the Asian Lutra sumatrana, climate change would instead lead to an increased, less fragmented, and more protected range extent, but the range extent would also be shifted into areas with higher human disturbances. Our study represents a balanced example of how to develop an index aimed at comparatively evaluating vulnerability to climate change of different species by combining different aspects of sensitivity and exposure, providing additional information on which to base more efficient conservation strategies.