Prey Scarcity Research Articles

Consequences of repeated sarcoptic mange outbreaks in an endangered mammal population

Diseases and parasites are important drivers of population dynamics in wild mammal populations. Small and endangered populations that overlap with larger, reservoir populations are particularly vulnerable to diseases and parasites, especially in ecosystems highly influenced by climate change. Sarcoptic mange, caused by a parasitic mite Sarcoptes scabiei, constitutes a severe threat to many wildlife populations and is today considered a panzootic. The Scandinavian arctic fox Vulpes lagopus is endangered with a fragmented distribution and is threatened by e.g. red fox Vulpes vulpes expansion, prey scarcity and inbreeding depression. Moreover, one of the subpopulations in Scandinavia has suffered from repeated outbreaks of sarcoptic mange during the past decade, most likely spread by red foxes. This was first documented in 2013 and then again 2014, 2017, 2019, 2020 and 2021. We used field inventories and wildlife cameras to follow the development of sarcoptic mange outbreaks in this arctic fox subpopulation with specific focus on disease transmission and consequences for reproductive output. In 2013–2014, we documented visual symptoms of sarcoptic mange in about 30% of the total population. Despite medical treatment, we demonstrate demographic consequences where the number of arctic fox litters plateaued and litter size was reduced after the introduction of S. scabiei. Furthermore, we found indications that mange likely was transmitted by a few arctic foxes travelling between several dens, i.e. ‘super‐spreaders'. This study highlights sarcoptic mange as a severe threat to small populations and can put the persistence of the entire Scandinavian arctic fox population at risk.

Residual toxicity of pesticide active substance commonly used in tomato crop on the predator Nesidiocoris tenuis (Heteroptera: Miridae)

AbstractNesidiocoris tenuis (Reuter) (Heteroptera Miridae) is a key biological control agent of the tomato leaf miner Tuta absoluta (Meyrick). However, in cases of prey scarcity, this predator switches into a phytophagous pest causing ring injuries in stems of tomato plants. The aim of this study was to assess the side effects of dry residues and explore the presence of target site resistance mutations of 10 insecticides, two bioinsecticides, an acaricide and a fungicide widely applied in IPM, on adults of N. tenuis collected from two different regions of Crete; the Western and the Eastern side of the island during two successive years. Lethal toxicity trials were performed on sprayed tomato stems and toxicity of adults of N. tenuis was recorded 2 h, 7 and 14 days after exposure. At both populations, chlorpyrifos, acetamiprid and thiamethoxam were moderately harmful at the application day and slightly harmful 7 days after the application. Only chlorpyrifos maintained its toxicity for more than 7 days. All the rest tested pesticides (emamectin benzoate, abamectin, chlorantraniliprole+abamectin, chlorantraniliprole, deltamethrin, tebufenpyrad, spinosad, Bacillus thuringiensis var kurstaki, metaflumizone and myclobutanil) were classified as harmless. Additionally, analysis of insecticide target site sequences indicated the absence of resistance mutations in both populations. Overall, our findings illustrate the impact of 15 pesticides and their residual toxicity on the mortality rates of N. tenuis adults.

Habitat associations of marine predators in the northern California Current during the low productivity downwelling season

IntroductionEastern Boundary Upwelling Systems are some of the most productive marine ecosystems in the world. Little is known about habitat associations and spatial distributions of marine predators during seasonal periods of low productivity because there are few at-sea surveys during this period. During low productivity or prey scarcity, predators consuming similar prey in the same time and space may compete for limited resources, or they may avoid competition by exploiting different habitats or occupying separate spaces (i.e. niche partitioning). In this study, we examined habitat associations and niche partitioning of marine predators during the low-productivity winter downwelling season of the northern California Current Ecosystem (CCE). MethodsSeabird and marine mammal counts were continuously collected during systematic at-sea surveys during February–March/April in the northern California Current across four years (2006, 2008, 2009, and 2012). We examined seabird and marine mammal distributions in relation to seven habitat characteristics [i.e., sea surface temperature (°C), salinity, depth (m), seafloor slope (%), distance from shore (km), and distance from the 100 m and 200 m isobaths (km)]. We used a non-parametric multivariate analysis [i.e. canonical correspondence analysis (CCA)] to quantify species’ habitat associations and directional distribution ellipses to explore overlap in species core winter habitat.ResultsResults show 49 seabird and ten marine mammal species inhabit the CCE during this low productivity period, including endangered southern resident killer whales (Orcinus orca). Seabirds and marine mammals exhibited significant but low overlap in habitat associations (i.e. weak niche partitioning) and similar habitat associations to summer studies. DiscussionWe also found that some species with similar foraging strategies showed asymmetrical spatial range overlap (i.e. common murre (Uria aalge) and parakeet auklet (Aethia psittacula)), which may mean that expected increased competition due to climate change can negatively affect some species more than others. Given that climate change is leading to increased frequencies, intensities, and durations of marine heat waves during winter months, addressing the winter ecology knowledge gap will be important to understanding how climate change is going to affect species that reside in or migrate through the northern California Current during the low productivity downwelling season.

Pollen provisioning attenuates pesticide side-effects on a phytoseiid predator.

Biological control with predatory mites is applied against pests in greenhouse crops. Chemical control with the use of selective, reduced-risk pesticides, is an important component of Integrated Pest Management (IPM) programs, that often needs to be combined with biological control. Here, we evaluated the effect of plant pollen when used as supplementary food on the survival, reproduction and predation of the predatory mite Amblydromalus limonicus (Acari: Phytoseiidae) after exposing young larvae and adults to flonicamid, an insecticide of moderate toxicity to phytoseiids. Pollen is an important alternative food for generalist phytoseiids ensuring survival and supporting populations build-up during periods of prey scarcity. Two regimes of cattail (Typha angustifolia L.) pollen differing in application frequency were used. In the first, the total amount of pollen was supplied once, within 30 min after insecticide application, whereas in the second regime, the same amount of pollen was supplied gradually, i.e., every 48 h. Regardless of the frequency of application, pollen provisioning results in a reduction in prey (thrips) consumption relative to the control (no pollen provisioning). Nevertheless, when adult mites were directly exposed to flonicamid residues, pollen provisioning attenuated the reduction in prey consumption as compared to the control. In addition, the gradual (every 48 h) provisioning of pollen to adult predators exposed to flonicamid residues impacted positively the intrinsic rate of population increase (rm) of A. limonicus as compared to when feeding on prey. Our results reveal an unexpected role of pollen provisioning in alleviating pesticides side-effects on phytoseiids. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Feast to famine: Sympatric predators respond differently to seasonal prey scarcity on the low Arctic tundra.

Resource fluctuation is a major driver of animal movement, influencing strategic choices such as residency vs nomadism, or social dynamics. The Arctic tundra is characterized by strong seasonality: Resources are abundant during the short summers but scarce in winters. Therefore, expansion of boreal-forest species onto the tundra raises questions on how they cope with winter-resource scarcity. We examined a recent incursion by red foxes (Vulpes vulpes) onto the coastal tundra of northern Manitoba, an area historically occupied by Arctic foxes (Vulpes lagopus) that lacks access to anthropogenic foods, and compared seasonal shifts in space use of the two species. We used 4 years of telemetry data following 8 red foxes and 11 Arctic foxes to test the hypothesis that the movement tactics of both species are primarily driven by temporal variability of resources. We also predicted that the harsh tundra conditions in winter would drive red foxes to disperse more often and maintain larger home ranges year-round than Arctic foxes, which are adapted to this environment. Dispersal was the most frequent winter movement tactic in both fox species, despite its association with high mortality (winter mortality was 9.4 times higher in dispersers than residents). Red foxes consistently dispersed toward the boreal forest, whereas Arctic foxes primarily used sea ice to disperse. Home range size of red and Arctic foxes did not differ in summer, but resident red foxes substantially increased their home range size in winter, whereas home range size of resident Arctic foxes did not change seasonally. As climate changes, abiotic constraints on some species may relax, but associated declines in prey communities may lead to local extirpation of many predators, notably by favoring dispersal during resource scarcity.

Intraguild predation of inferior larval instars of two ladybirds Menochilus sexmaculatus (Fabricius) and Propylea dissecta (Mulsant) (Coleoptera:Coccinellidae)

Ladybird beetles are predatory insects, which consumes everal insect pests and have immense biocontrol potential, particularly against aphids. In prey scarcity, they resort to intraguild predation (IGP) by consuming immature stages of other heterospecific ladybirds. A laboratory experiment was performed to quantify the incidence of IGP of first and second larval instars by older instars and adults of two co-occurring ladybird species, Propylea dissecta and Menochilus sexmaculatus. IGP of first and second larval instars increased significantly with increase in the larval stages followed by adult males and females. Predatory stages of M. sexmaculatus were more potential intraguild predators than those of P. dissecta. Among adults, the female consumed a greater number ofearly and weaker heterospecific instars. The presence of dorsal spines and hair on the larva of M. sexmaculatusprovided aposematism that helps in defense against superior heterospecific larvae thereby enabling its successful establishment and distribution. M. sexmaculatus could act as an intraguild predator in the fields and may contribute in declining the population density of P. dissecta during aphid-prey scarcity.

Notable predominant morphology of the smallest most abundant protozoa of the open ocean revealed by electron microscopy.

In the microbe-driven ecosystems of the open ocean, the small heterotrophic flagellates (sHF) are the chief microbial predators and recyclers of essential nutrients to phototrophic microbes. Even with intensive molecular phylogenetic studies of the sHF, the origins of their feeding success remain obscure because of limited understanding of their morphological adaptations to feeding. Here, we examined the sHF morphologies in the largest, most oligotrophic South Pacific and Atlantic (sub)tropical gyres and adjacent mesotrophic waters. On four research cruises, the sHF cells were flow cytometrically sorted from bacterioplankton and phytoplankton for electron microscopy. The sorted sHF comprised chiefly heterokont (HK) biflagellates and unikont choanoflagellates numerically at around 10-to-1 ratio. Of the four differentiated morphological types of HK omnipresent in the open ocean, the short-tinsel heterokont (stHK), whose tinsel flagellum is too short to propagate a complete wave, is predominant and a likely candidate to be the most abundant predator on Earth. Modeling shows that the described stHK propulsion is effective in feeding on bacterioplankton cells at low concentrations; however, owing to general prey scarcity in the oligotrophic ocean, selective feeding is unsustainable and omnivory is equally obligatory for the seven examined sHF types irrespective of their mode of propulsion.

Scat piling and strong frugivory of the Balearic lizard, Podarcis lilfordi (Günther, 1874)

BackgroundIn lacertid lizards from Mediterranean islands, frugivory is common, particularly under prey scarcity, a characteristic of small islands. In several populations, the diet of the Balearic lizard, Podarcis lilfordi, is extremely variable and includes fleshy fruits. However, frugivory is sporadic and there are very few examples of dominant fruit consumption.ResultsWe describe the existence of an extraordinary fruit consumption of a single plant species, the juniper, Juniperus phoenicea, by the Balearic lizard, P. lilfordi. In addition, for the first time in Lacertidae, we describe the existence of scat piling in the population of these lizards inhabiting Cabrera Island (Balearic Islands, Spain). Scat piling was detected in an isolated location with hundreds of scats deposited by several individuals at a particular place.ConclusionsThe high population density of lizards at the island of Cabrera and the great versatility of foraging behavior of this species allows us to hypothesize that scat piles could act as an attractor for numerous individuals, that is, as inadvertent social information. If that hypothesis is correct, it would result in the concentration of several individuals foraging on a single or a few ripening plants. We cannot, however, rule out that individuals concentrated due to the scarcity of ripening plants in other areas, without any influence of the presence of several lizards, as attractors to the site. Our findings modify previous descriptions of the diet of the Balearic lizard in Cabrera made with smaller samples. In some places and periods of the year, frugivory on a single plant species can be extremely intense and only large sample sizes of scats allow to find these particular trends in the foraging ecology of insular lizards.

Does prey scarcity increase the risk of wolf attacks on domestic dogs?

Gray wolf Canis lupus predation on domestic dogs Canis familiaris is a considerable wolf–human conflict issue in several regions of Europe and North America but it has not been well documented in the scientific literature. Livestock depredations by wolves may be related to the abundance of wild prey. Regardless of the presumed motivations of wolves for attacking dogs (likely due to interference competition and predation), the abundance of wild prey populations may also influence the risk of wolf attacks on dogs. We examined whether the annual number of fatal attacks by wolves on dogs was related to the abundance of primary prey, including wild boar Sus scrofa and roe deer Capreolus capreolus in Estonia, as well as the abundance of moose Alces alces in Finland. Statistical models resulted in significant negative relationships, thus providing evidence that the risk of attacks in both house yards (Estonia) and hunting situations (Finland) was highest when the density of wild prey was low. Wild ungulates cause damage to agriculture and forestry, but they seem to mitigate conflicts between wolves and humans; therefore, it is necessary to develop a holistic, multispecies management approach in which the importance of wild ungulates for large carnivore conservation is addressed.

Cannibalism and intraguild predation between endemic and introduced coccidophagous lady beetles (Coleoptera: Coccinellidae)

AbstractThe Chilocorini lady beetles Tenuisvalvae notata (Mulsant) and Cryptolaemus montrouzieri Mulsant are important biological control agents being able to share their habitat and compete for their preferred prey, mealybugs. Whereas T. notata is native to South America, C. montrouzieri is an Australian species introduced in Brazil in a biological control program of mealybugs. This work investigated the cannibalism and intraguild predation between these species in the absence of prey. To test for intraguild predation, one individual larva (instars 1–4) from each species was confined for 24 h with another larva of the same instar or the next instar, in a total of 10 combinations. In addition, we measured predation of T. notata adults upon eggs, larvae, pre‐pupae and pupa of C. montrouzieri, and vice versa. Cannibalism within the species was also tested across adults, larvae and eggs. Results showed asymmetric interactions in favour of C. montrouzieri, which acted as intraguild predator more than 80% of the time when paired with larvae of T. notata either of the same or different instar. In addition, C. montrouzieri adults preyed more upon larvae and eggs of T. notata than the contrary. There was no intraguild predation upon pre‐pupae and pupae. Cannibalism was high upon eggs and first instar larvae of T. notata (89.5% and 65%) and C. montrouzieri (100% and 55%), respectively. Therefore, the exotic C. montrouzieri outcompeted the native T. notata and could become a threat to this endemic species in areas of simultaneous occurrence and under prey scarcity. Thus, the interactions between these lady beetles could affect the success of biological control of mealybugs.

Diet of Snow Leopard Panthera uncia in Kanchanjunga Conservation Area

The population of Snow Leopard is declining due to anthropogenic activities and prey scarcity. Snow Leopard’s preferred prey species are Tibetan Argali, Blue Sheep, Himalayan Tahr, Himalayan Marmot, Royle’s Pika, rodents, and livestock such as Yak, Horse, Lulu Cow, Goat and Sheep. Due to livestock depredation by Snow Leopards and other carnivores, local people have a negative attitude towards carnivores’ conservation leading to retaliatory killing. This study identified whether Snow Leopards prey on wildlife or livestock based on micro-histological study of Snow Leopard’s scats. Micro-histological analysis of 39 scat samples of Snow Leopard confirmed that Blue Sheep is the major prey species in Kanchanjunga Conservation Area (KCA). The scat analysis also showed that Snow Leopards prey on livestock mainly to Chauri in KCA, however the number and incidences were few. The herders also confirmed the occasional hunting of their livestock depredation by Snow Leopard in KCA. People have positive attitudes towards Snow Leopard conservation because they are less suffering from Snow Leopard in KCA. If wild prey species are abundant in the wild, livestock depredation might be low.

Coexistence of large carnivore species in relation to their major prey in Thailand

Spatial and temporal partitioning often facilitates species coexistence. We used camera traps to study habitat use and spatio-temporal interactions among three large carnivores—tiger, leopard, and dhole—in two national parks in Thailand where key prey species (sambar, gaur) were scarce from overhunting. The availability of remnant sambar was the strongest determinant of tiger occupancy. Leopard occupancy was positively related to the presence of wild pig. Dhole occupancy was negatively associated with sambar, opposite to tiger. Results of two-species occupancy modeling did not support our hypothesis that leopard would be excluded from tiger-occupied zones, but leopard detectability was seven times lower in the presence of tigers, indicative of fine-scale avoidance. Dhole avoidance of sambar might have been a tactic by which dhole avoided tigers. All three carnivores were mainly diurnal and thus had high temporal overlap (> 80%). Tiger density may have been too low (0.36/100 km2) to compel temporal avoidance by leopard and dhole where they overlapped. Our results suggest that low density populations of tigers and leopards can overlap in habitat use and temporal activity, despite the potential for intensified competition due to prey scarcity. Dholes were widespread despite scarcity of large ungulates, and seem more resilient to the loss of large-bodied prey than tigers. MWKL has an important role in conserving dholes, which are declining globally.

Tiger density, movements, and immigration outside of a tiger source site in Thailand

AbstractLandscape‐scale strategies for conserving wild tigers emphasize the role of core breeding populations (source sites) to replenish surrounding areas which have lost tigers. In Southeast Asia, a few potential source sites remain, particularly Huai Kha Khaeng Wildlife Sanctuary, Thailand (HKK). We investigated tiger density in two reserves (Mae Wong, Khlong Lan: MWKL) adjacent to HKK where tigers and their prey were scarce due to historic poaching but current management offered effective protection. Camera trapping revealed 10 adult tigers (four males, six females), at least two of which had immigrated from HKK. Spatially explicit tiger density was 0.359 tigers/100 km2, 5.6 times lower than HKK. The population was breeding, with six cubs observed. Tiger movements (measured by σ, the spatial scale parameter) were twice as extensive in MWKL as in HKK, indicative of prey scarcity in MWKL. The disparity in density between MWKL and HKK reveals that tiger recovery is a slow process when prey are scarce, even when recovery areas are apparently well‐managed and connected to a source site. We review source‐recovery dynamics of tigers in other sites in Asia and find that low prey impedes landscape‐scale recoveries elsewhere as well.

Tropical deforestation induces thresholds of reproductive viability and habitat suitability in Earth\u2019s largest eagles

Apex predators are threatened globally, and their local extinctions are often driven by failures in sustaining prey acquisition under contexts of severe prey scarcity. The harpy eagle Harpia harpyja is Earth’s largest eagle and the apex aerial predator of Amazonian forests, but no previous study has examined the impact of forest loss on their feeding ecology. We monitored 16 active harpy eagle nests embedded within landscapes that had experienced 0 to 85% of forest loss, and identified 306 captured prey items. Harpy eagles could not switch to open-habitat prey in deforested habitats, and retained a diet based on canopy vertebrates even in deforested landscapes. Feeding rates decreased with forest loss, with three fledged individuals dying of starvation in landscapes that succumbed to 50–70% deforestation. Because landscapes deforested by > 70% supported no nests, and eaglets could not be provisioned to independence within landscapes > 50% forest loss, we established a 50% forest cover threshold for the reproductive viability of harpy eagle pairs. Our scaling-up estimate indicates that 35% of the entire 428,800-km2 Amazonian ‘Arc of Deforestation’ study region cannot support breeding harpy eagle populations. Our results suggest that restoring harpy eagle population viability within highly fragmented forest landscapes critically depends on decisive forest conservation action.

Epimeletic behaviour in a Southern Resident Killer Whale (<i>Orcinus orca</i>)

Southern Resident Killer Whale (SRKW, Orcinus orca) may be found year round in the Salish Sea. These orcas comprise three matrilineal pods (J, K, and L) and were listed as Endangered under the Canadian Species at Risk Act in 2003 and under the United States Endangered Species Act in 2005 because of prey scarcity, vessel noise and disturbance, small population size, and exposure to toxins. Since 1993, the Whale Museum has been operating Soundwatch, a boater education program for vessels. Soundwatch personnel are on the water in the central Salish Sea throughout the summer educating boaters on how to maneuver near marine mammals legally and documenting vessel regulation violations and marine mammal presence and behaviour. Starting on 24 July 2018, Soundwatch documented an adult female SRKW of J pod (J35) carrying a dead neonate calf. J35 continued to carry her dead calf for 17 consecutive days covering ~1600 km. Her story riveted the attention of the people of the Salish Sea as well as people around the world, evoking empathy for J35 and her loss as well as the plight of the Endangered SRKW population. Here, we tell her story and evaluate whether the behaviour J35 displayed toward her dead calf was an example of epimeletic behaviour, animal grief.

Interactions Among Native and Non-Native Predatory Coccinellidae Influence Biological Control and Biodiversity.

Over the past 30 yr, multiple species of predatory Coccinellidae, prominently Coccinella septempunctata L. and Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) have spread to new continents, influencing biodiversity and biological control. Here we review the mechanisms underlying these ecological interactions, focusing on multi-year field studies of native and non-native coccinellids and those using molecular and quantitative ecological methods. Field data from Asia show that H. axyridis, C. septempunctata, and Propylea japonica (Thunberg) (Coleoptera: Coccinellidae) are regularly among the most abundant predatory species but their rank varies by habitat. Studies of these species in their native Asian range, primarily related to their range in mainland China, document different patterns of seasonal abundance, species specific associations with prey, and habitat separation. Intraguild predation is well documented both in Asia and in newly invaded areas, and H. axyridis benefits most from this interaction. Harmonia axyridis also seems to rely more on cannibalism in times of prey scarcity than other species, and relatively sparse data indicate a lower predation pressure on it from natural enemies of coccinellids. Declines in the abundance of native coccinellids following the spread and increase of non-native species, documented in several multi-year studies on several continents, is a major concern for native biodiversity and the persistence of native coccinellid species. We suggest that future studies focus more attention on the community ecology of these invasive species in their native habitats.

Benefits of a balanced diet? Mixing prey with pollen is advantageous for the phytoseiid predator Amblydromalus limonicus

Plant pollen is an important alternative food for generalist phytoseiid mites ensuring survival and supporting population build-up during periods of prey scarcity. However, in the short term predator efficacy can be negatively affected by pollen provisioning as a consequence of predator satiation or when pollen is preferred over prey. This is counteracted by the fact that, combining pollen with prey in a balanced mixed diet, may benefit the numerical response of the predator and thus, improve the effectiveness of long-term biological control. Here, we assessed the effects of pollen (Typha angustifolia, Zea mays, Pinus brutia) provisioning in a mixed diet with prey (thrips) on the performance and predation efficiency of Amblydromalus limonicus, a predatory mite used against thrips and whiteflies in greenhouse crops. We found that provisioning pollen in mixed diets with high-quality prey resulted in significant decrease in prey consumption. This effect was shown to be stronger for T. angustifolia and weaker for P. brutia when both were combined with thrips larvae. When pollen was provided alongside thrips, this resulted in a significant decrease in juvenile dispersal and oviposition was always higher. The highest value of intrinsic rate of population increase (rm) was recorded for the mix of cattail pollen and thrips, and the strongest increase in rm when thrips were combined with pine pollen followed by corn and cattail pollen. Overall, mixing prey with pollen resulted in higher rm values thus enhancing the medium- to long-term thrips-control potential of A. limonicus.

Unbalanced population structure and reliance on intraspecific predation by largemouth bass in an agricultural pond with no available prey fish

The carnivorous largemouth bass Micropterus salmoides has been introduced to many regions and poses a threat to native aquatic organisms due to predation, resulting in a significant decrease in biodiversity. Under conditions of prey scarcity, the largemouth bass is thought to consume smaller conspecifics. However, little is known about this species’ dietary reliance on intraspecific predation and its impact on the population structure. We investigated the length–frequency distribution of largemouth bass and estimated their reliance on intraspecific predation using stable carbon and nitrogen isotopes in an agricultural pond with no available prey fish. Almost all individual largemouth bass were collected via the pond drainage system. Within the largemouth bass population, the dominant length class was composed of fish measuring 100–160 mm standard length (SL), whereas few individuals measuring < 100 mm SL (first-year juveniles) were collected. The results from a Stable Isotope Analysis in R mixing model indicated that all four length classes (105–146, 165–180, 216–246, and 300–337 mm SL) of largemouth bass fed mainly on juvenile conspecifics and on red swamp crayfish (Procambarus clarkii). First-year juveniles could have been predated by other individuals of various sizes. The dominant 100–160 mm SL length class may have experienced a weak predation pressure when they were in the first-year juvenile class. Consequently, the largemouth bass population was unbalanced, with few first-year juveniles (< 100 mm SL) and dominance of a 100–160 mm SL length class.

Learning strategies and long-term memory in Asian short-clawed otters (Aonyx cinereus).

Social learning, where information is acquired from others, is taxonomically widespread. There is growing evidence that animals selectively employ ‘social learning strategies', which determine e.g. when to copy others instead of learning asocially and whom to copy. Furthermore, once animals have acquired new information, e.g. regarding profitable resources, it is beneficial for them to commit it to long-term memory (LTM), especially if it allows access to profitable resources in the future. Research into social learning strategies and LTM has covered a wide range of taxa. However, otters (subfamily Lutrinae), popular in zoos due to their social nature and playfulness, remained neglected until a recent study provided evidence of social learning in captive smooth-coated otters (Lutrogale perspicillata), but not in Asian short-clawed otters (Aonyx cinereus). We investigated Asian short-clawed otters' learning strategies and LTM performance in a foraging context. We presented novel extractive foraging tasks twice to captive family groups and used network-based diffusion analysis to provide evidence of a capacity for social learning and LTM in this species. A major cause of wild Asian short-clawed otter declines is prey scarcity. Furthering our understanding of how they learn about and remember novel food sources could inform key conservation strategies.

The effect of short-term fasting on the oxidative status of larvae of crested newt species and their hybrids

In nature, animals often face periods without food caused by seasonal fluctuations and/or prey scarcity. An organism's physiological response to imposed energetic limitations is followed by changes in mitochondrial functioning (adjustment of energy metabolism) and a reduction of non-essential processes. However, this energy-saving strategy can have its costs. In this study, we examined oxidative stress as one of the possible physiological costs of short-term, two-week-long food deprivation on developing amphibian larvae of the crested newts Triturus macedonicus and Triturus ivanbureschi and their hybrids. We investigated whether this exogenous factor additionally affected the oxidative status (fitness-related trait) of hybrid individuals. The fasting treatment led to lower growth and a lower body mass and body condition index of individuals. The results revealed that the antioxidant system (AOS) of food-deprived larvae could not cope in a proper manner with reactive oxygen species production under limited energy availability, leading to higher lipid oxidative damage. The lowest AOS response was observed for H2O2 scavenging parameters (catalase, glutathione peroxidase, and total glutathione), which together with the elevated activity of superoxide dismutase suggested increased H2O2 concentrations. Comparison between parental species and their hybrids showed that hybrid individuals suffered greater oxidative damage (as demonstrated by higher concentrations of lipid peroxides), indicating that they were more susceptible to fasting-induced oxidative stress. Overall, this study illustrates that: (i) an oxidative event is one of the costs amphibian larvae face during short-term periods of fasting, (ii) hybrids are less capable of dealing with this stressful condition, which can lower their chances of survival in a changing environment.