Main Prey Research Articles

Response of cetaceans to fluctuations of pelagic fish stocks and environmental conditions within the Celtic Sea ecosystem

Inshore waters off the south coast of Ireland are an important foraging area for a range of cetacean species. Some of the main prey species of these cetaceans are herring and sprat, two economically valuable fish species in the region. The Celtic Sea herring stock suffered a marked decline in 2013. The present study aimed to investigate potential changes in the ecosystem associated to the herring decline and to determine the potential impacts on predators. Here we analyzed sightings information of common dolphins, fin, minke, humpback and unidentified whale species, acoustic data of herring and sprat, and a range of environmental variables mainly derived from satellites. Firstly, we characterized spatio-temporal patterns in the relative abundance of predator and prey species, and environmental variables, and compared periods before and since the herring decline. Since the 2013 herring decline, (i) the herring stock has mainly concentrated in south-eastern coastal waters and southern offshore Irish waters, (ii) sprat density has increased, (iii) chlorophyll concentration has decreased, (iv) sea surface temperature has risen, and (v) the euphotic layer has extended deeper. Secondly, we modelled the effects of prey density and environmental conditions on the relative abundance and distribution of cetaceans, as well as the effects of environmental conditions on prey density, between 2005-2018 by applying Hurdle Generalized Additive Models. The models for herring and sprat support the idea that these species have different environmental relationships, for example herring tended to be found in shallower waters than was the case for sprat. The presence and relative abundance of common dolphins were significantly affected by both environmental conditions and herring density, whereas whale species presence and relative abundance were found to be correlated with sea surface temperature and prey density. The model results suggest differences in prey choice among whale species. Understanding the dynamic relationships between predators, prey and the environment is important to inform an ecosystem-based approach to fisheries management.

When bat eats bat: diet and roosts of the greater broad-nosed bat (Scoteanax rueppellii) across different regions and habitats

Roost selection and diet are fundamentally important to bats and can vary geographically and with habitat. The greater broad-nosed bat (Scoteanax rueppellii) is infrequently captured and poorly known, meaning appropriate conservation actions are difficult to determine. To assess variation across different habitats, we collected faecal samples for dietary analysis and radio-tracked individuals to identify roost trees at four different sites across New South Wales, Australia. Analysis of droppings verified beetles as the main prey in each study area except one dominated by mangroves, and confirmed for the first time carnivory in wild-caught individuals from the presence of hair from other bat species in its droppings. Very large, hollow trees were used as maternity roosts, being typically larger than neighbouring trees. Roosting habitat varied from wet sclerophyll forest in gullies to old-growth mangroves, and tree species used as roosts also varied. Colony size at maternity roosts was often 50–100 bats and fidelity to the maternity roost varied, with some being switched almost daily and others occupied for at least several days. One maternity roost was re-used 2 years later. Both the importance of beetles in the diet and roosts located in more productive landscapes suggest coastal plains and foothills may represent key habitat.

Hunting introduced species in Indonesia New Guinea

Abstract. Pattiselanno F, Tokede MJ, Arobaya AYS, Mardiatmoko G, Pattiselanno AE. 2023. Hunting introduced species in Indonesia New Guinea. Biodiversitas 24: 3045-3050. Hunting in tropical forests is mostly performed to obtain animal protein sources, generate income, and enact cultural activities. However, it is acknowledged that hunting was conducted indiscriminately, killing both native and introduced species. This study aimed to describe hunting activities along the lowland coastal forests in Tambrauw Districts. Fieldwork was carried out between June 2011 and December 2012 in eleven villages across the Abun and Amberbaken sub districts of Tambrauw Districts, Papua Barat Province of Indonesia. Information about hunting was gathered through interviews with 220 hunters (focus respondents; 20 hunters in each village). Therefore, to gain an overall picture of hunting in the sampled villages, we distributed 100 questionnaires, not including those focal respondents, and 800 were returned from 11 villages. This study revealed hunting for trading (49%) compared to consumption (44%) and the rest (7%) hunting for others (festive, pest, and trophy). The hunting is classified as very frequent (2-3 days per week) by 10%, frequent (weekly and fortnightly) by 41%, and rarely (monthly) by 49% of hunters. Active techniques used were bows and arrows, spears and blades were primarily used by 38%, and hunting with dogs was 29% by inhabitants in the studied villages. On the other hand, passive hunting using snares and guns were used by 28% and 5% of hunters, respectively. Hunters reported nine main prey species had been hunted, and the prey consisted of six mammal and three bird species. Two of the nine species were introduced species, i.e., rusa deer and wild pig; they provided the largest amount of meat and fat and were economically profitable. Other native species were also hunted, although not much as introduced ones. The average catch per hunting trip was 2 individuals (2.42 ± SD 1.93). In this study, hunting introduced species is important because it is more profitable while protecting the native species or those of conservation concern.

Impact of disturbance on common scoter carrying capacity based on an energetic model

Shallow coastal zones are intensely used by humans but simultaneously are biodiversity hotspots, with a crucial role in the life cycle of many marine species. The competition for food or space between humans and protected wildlife intensifies under pressure of an increased need for marine resources for human consumption. For successful management it is important to establish the key components driving such conflicts of interest. Here we focus on the protected common scoter (Melanitta nigra), a sea duck wintering in coastal habitats that are rich in food, but also among the most disturbed marine systems worldwide. Due to the scoters' shyness disturbance impacts the birds’ ability to forage and poses a conflict for balancing bird conservation and economics, including a fishery on its main bivalve prey Spisula subtruncata. In this study, we use an energy budget model to quantify the consequences of depth, currents and disturbance on scoter energetics and carrying capacity. Energetics were described using physical parameters and field data on food availability and disturbance. Results reveal non-linear relationships and a threshold value for when a scoter can no longer maintain its energy balance. This is caused by limited foraging time, rather than food availability. From a conservation perspective, this implies that a precautionary principle should be used, because there will be no warning when an area becomes unsuitable. In addition, the model was applied to study the effects of disturbance from different kinds of shipping in a coastal area of the North Sea, north of The Netherlands. Cargo shipping has the largest impact on the carrying capacity, where there is spatial overlap of prey and an intensively used shipping lane. In other prey distribution situations shrimp vessels may cause most disturbance. Spisula-Ensis fisheries did not limit the potential carrying capacity due to the limited catches and number of fishing trips. Scoter protection should be aimed at flexible spatial management and on only those vessel types above a Spisula bed with a large number of trips, and above all should work from a precautionary principle given the critical thresholds for scoter presence.

Prey availability influences the effect of boldness on reproductive success in a mammalian predator

Boldness is an important trait in wild populations, and among-individual differences can link to individual fitness. The strength and direction of relationships between behavioral and life-history traits may however vary according to environmental conditions, where fluctuating selection acting on behavioral traits contributes to the maintenance of personality differences. We explored sources of variation in Arctic fox (Vulpes lagopus) boldness and investigated how temporal variation in the abundance of a main prey (lemmings) influences the relationship between fox boldness and reproductive success. We measured the behavioral reaction of individuals when escaping after handling, as an indicator of their boldness. We obtained 70 measurements from 42 individuals during two years of low lemming abundance and 2 years of high lemming abundance and assessed fox litter size as an indicator of reproductive success. First, individual characteristics (age, sex, mass) did not affect Arctic fox boldness, while individual identity generated variation in boldness. Next, we found that during years of low lemming density, individuals behaving boldly had more pups than those behaving less boldly, suggesting boldness may provide an advantage when lemmings are scarce by increasing hunting success or allowing access to alternative resources. However, all individuals tended to show high levels of boldness when lemming density was high, and all produced large litters. Temporal variation in the abundance of a main prey might therefore influence the relation between boldness and reproductive success of a predator, and if individuals consistently differ in their level of boldness, fluctuating selection could contribute to the maintenance of personality.Significance statementEffects of boldness on Arctic fox reproductive success: lemming abundance matters! When lemmings are scarce, foxes showing bold behavior have more pups than foxes showing less bold behavior. This highlights that under low prey availability, boldness may bring short-term benefits to predators, potentially because it allows to acquire more food. When lemmings are abundant, however, all foxes produce as many pups. This shows that environmental conditions such as prey abundance can influence the relation between behavior and reproductive success in a predator. Studying the context-dependency of relationships between behavior and reproductive success is critical to better understand ecological and evolutionary consequences of environmental change.

Density and genetic diversity of grizzly bears at the northern edge of their distribution

AbstractSpecies at the periphery of their range are typically limited in density by poor habitat quality. As a result, the central–marginal hypothesis (CMH) predicts a decline in genetic diversity of populations toward the periphery of a species' range. Grizzly bears (Ursus arctos) once ranged throughout most of North America but have been extirpated from nearly half of their former range, mainly in the south. They are considered a species at risk even in Canada's remote North, where they occupy the northernmost edge of the species' continental distribution in a low‐productivity tundra environment. With climate change, one of their main prey species in the tundra (caribou), which has always shown yearly fluctuations, is declining, but simultaneously, grizzlies appear to be expanding their range northward in the same tundra environment. Yet, a lack of population density estimates across the North is hindering effective conservation action. The CMH has implications for the viability of peripheral populations, and the links between population fluctuations, potential bottlenecks, and genetic diversity need to be determined to contribute to species' conservation. Using noninvasive genetic sampling from 2012 to 2014 and autosomal DNA genotyping (via microsatellites), we estimated bear density using a spatial capture–recapture framework and analyzed genetic diversity using observed heterozygosity (Ho), allelic richness (AR), and expected heterozygosity (He). We compared our findings to other studies that used comparable methodologies on grizzly bears and a related species (black bears; Ursus americanus). We found densities of grizzly bears that were low for the species but characteristic for the region (5.9 ± 0.4 bears/1000 km2), but with high Ho (0.81 ± 0.05), AR (7 ± 0.78), and He (0.71 ± 0.03), despite a signal of recent bottlenecks. In both species, peripherality was not correlated with Ho but was negatively correlated with density. We suggest that the apparent growth of this expanding population of grizzlies offsets the negative impacts of recent bottlenecks on Ho. Indigenous knowledge provides historical context (on the order of centuries, e.g., arctic large mammal fluctuations, grizzly bear bottlenecks) for the current bear population dynamics (on the order of decades, e.g., climate change, northern grizzly bear expansion).

Experimental feeding validates nanofluidic array technology for DNA detection of ungulate prey in wolf scats

AbstractThe study of carnivores' diet is a key component to enhance knowledge on the ecology of predators and their effect on prey populations. Although molecular approaches to detect prey DNA in carnivore scats are improving, the validation of their accuracy, a prerequisite for reliable applications within ecological frameworks, is still lagging behind the methodological advances. Indeed, variation in detection probability among prey species can occur, representing a potentially insidious source of bias in food‐habit studies of carnivores. Calibration of DNA‐based methods involves the optimization of specificity and sensitivity and, whereas priority is usually given to the former to avoid false positives, sensitivity is rarely investigated so that false negatives may be largely overlooked. We conducted feeding trials with captive wolves (Canis lupus) to validate a nanofluidic array technology recently developed for the detection of multiple prey species in scats. Using 371 scat samples from 12 wolves fed with a single‐prey diet, the sensitivity of our nanofluidic array method varied between 0.45 and 0.95 for the six main ungulate prey species. The method sensitivity was enhanced by using multiple markers per species and by a relatively low threshold of number of amplifying markers required to confirm a detection. Yet, at least two markers should be used to avoid false positives. By acknowledging sources of bias in sensitivity to reliably interpret the results of DNA‐based dietary methods, our study highlights the relevance of feeding experiments to optimally calibrate the relative thresholds to define a positive detection and investigate the occurrence and extent of biases in sensitivity.

Supplementation of seasonal natural resources with year‐round anthropogenic resources by coyotes in natural fragments within a high‐density urban area

Coyotes Canis latrans in urban landscapes provide important food web functions and ecological services but can also trigger human‐wildlife conflict when their diet includes anthropogenic resources or domestic pets. As adaptable omnivores, coyotes adjust their diet to their environment, routinely switching among food items to accommodate spatial and seasonal differences in availability. To evaluate the coyote's potential impacts within the food web of urban Long Beach, California where human‐wildlife conflict involving coyotes may occur, we analyzed 115 scat samples collected once every two weeks from four open space fragments inside the urban matrix. We hypothesized that differences in scat composition would correlate with seasonal and site differences, with greater use of anthropogenic resources during the dry season supplementing lower prey availability, and with greater consumption of wild mammal prey during the wet season when fruiting plants are less abundant. We found coyote diet was predominately composed of natural prey and vegetation year‐round, with seasonal variation. Mammals made up more of coyote diet in the wet season than the dry, while invertebrates and vegetation were more prevalent in dry season scats. Coyotes relied on rabbits as their main prey year‐round across all sites. Domestic cats Felis catus were the third most common individual prey species found in coyote scats, occurring in 14% of scat samples in both seasons. Coyotes also supplemented seasonally available natural food sources with anthropogenic resources, which occurred in 13% of coyote scats overall with no significant seasonal variation. While rabbits appeared in scat from all sites, the occurrence of invertebrates, small mammals, and vegetation in scats varied between sites. While there is a potential for human‐wildlife conflict in coyote's consumption of feral or domestic cats, coyotes may also be providing an ecological service by reducing cats in natural habitat fragments.

Habitat preference of leopard cat (Prionailurus bengalensis Kerr. 1792) in the Cisokan Hydropower Development Area, West Java, Indonesia

Abstract. Shanida SS, Megantara EN, Husodo T, Mutaqin AZ, Kendarto DR, Wulandari I. 2023.Habitat preference of leopard cat (Prionailurus bengalensis Kerr. 1792) in the Cisokan Hydropower Development Area, West Java, Indonesia. Biodiversitas 24: 2284-2293. Leopard cat (Prionailurus bengalensisKerr. 1792) can occupy various habitats, including degraded and human-modified landscapes such as agricultural lands, plantations, and settlements. Nonetheless, there is little information about their responses to infrastructure development impacts the habitat preference of leopard cats. This study aims to reveal the habitat preferences of leopard cats in the Upper Cisokan Pumped Storage (UCPS) hydropower development area, Cianjur Regency and West Bandung Regency, West Java. Direct observation was conducted to collect habitat preference in terms of biotic, abiotic and anthropogenic parameters and analyzed using Vanderploeg and Scavia's Resource Selection Index (VSI). The results showed that in term of biotic factors, leopard cats preferred natural forests, shrubs, and rice fields; tree canopy area of ??51%-75%, tree DBH >20 cm, tree height 0-5 m and 11-15 m, and tree density of 0-20 trees. Leopard cats preferred 76%-100% shrubs canopy; ground-plant cover of 26%-75% with withered grass cover of 76%-100%. According to their abiotic factors, leopard cats preferred habitats with north and south, gentle, and lower slopes. The leopard cats also preferred habitat with wet soil. In term of anthropogenic factors, leopard cats preferred habitat close to water sources (<500 m). Leopard cats chose habitats with moderate distances (500 m-1000 m) from anthropogenic disturbances with weak intensity. Agricultural activities could affect its habitat preference directly. Leopard cats were found at various levels of disturbance in human-modified lands, such as rice fields and shrublands. Since the main prey is cosmopolitan animals, as long as there is human-modified land, prey availability will remain guaranteed. Although the leopard cat can tolerate anthropogenic disturbances, there is little information on the direct impact of construction activities on this population, so further research is needed to observe their population and habitat in the construction area.

Feeding Ecology of Red Seabream, Pagrus major (Sparidae) in the Korea Strait

The feeding ecology of red seabream, Pagrus major was studied using 1046 specimens collected by danish seine and bottom trawl from January to December 2018 in the Korea Strait. The size of the individuals ranged from 18.4 to 70.4 cm in fork length. Red seabream was a carnivore that consumed mainly anthozoans, brachyurans, and cephalopods. Its diets included also small quantities of amphipods, anomurans, ophiurids, gastropods, polychaetas, etc. We calculated the trophic level as 3.57 for red seabream. As red seabream grows, the proportion of relatively small prey items such as anomurans and ophiuroids decreases, while that of large prey items such as anthozoans, brachyurans, and cephalopods increases. In the largest size class (≥45 cm FL), cephalopods and pisces are its main prey. Alsoe, the body size of red seabream increased the mean weight of prey per stomach tended to increase significantly (One-way ANOVA: p 0.05). The diet composition of red seabream showed seasonal changes. The cephalopods were the dominant prey items for all seasons. The weight proportion of brachyurans was higher in summer and autumn, whereas anthozoans feeding rate was the highest in winter. PERMANOVA analysis showed significant variations among size classes and seasons. The feeding intensity by size class and season observed no significant difference (One-way ANOVA: p 0.05). As a result of the feeding strategy analysis, red seabream was a generalized feeder, with a wide niche width.

Food supplementation increases reproductive performance of ospreys in the lower Chesapeake Bay

The Atlantic States Marine Fisheries Commission (ASMFC), the governing body responsible for managing fisheries on the U.S. East Coast, formally adopted the use of Ecological Reference Points (ERPs) for Atlantic menhaden, Brevoortia tyrannus. Scientists and stakeholders have long recognized the importance of menhaden and predators such as ospreys, Pandion haliaetus, that support the valuable ecotourism industry and hold cultural significance. Landings in the reduction fishery are at their lowest levels and menhaden is facing potential localized depletion. Mobjack Bay, located within the lower Chesapeake Bay, has been a focus of osprey research since 1970 and represents a barometer for the relationship between osprey breeding performance and the availability of their main prey, menhaden. Since local levels of menhaden abundance were not available, we conducted a supplemental menhaden feeding experiment on osprey pairs during the 2021 breeding season. Our main objective was to determine if the delivery rate of menhaden had an influence on nest success and productivity. Nest success (χ2 = 5.5, df = 1, P = 0.02) and productivity (β = 0.88, SE = 0.45, CI = 0.049, 1.825, P = 0.048) were significantly higher within the treatment group. Reproductive rates within the control group were low and unsustainable suggesting that current menhaden availability is too low to support a demographically stable osprey population. Menhaden populations should be maintained at levels that will sustain a stable osprey population in which they are able to produce 1.15 young/active nest to offset mortality.

Animal behavior informed by history: Was the Asiatic cheetah an obligate gazelle hunter?

Understanding key ecological adaptations, such as foraging, when a predator is almost extinct is complex. Nonetheless, that information is vital for the recovery of the persisting individuals. Therefore, reviewing historical, ethnobiological and recent records can assist in exploring the species behavioral ecology. We applied this approach to Asiatic cheetahs (Acinonyx jubatus venaticus), which once roamed most west and central Asian countries but now is confined to a few dozens in Iran, at historical (pre-1970) and recent (post-1970) scales. We addressed a widely popular perception that Asiatic cheetahs were subjected to prey shifts from gazelles (Gazella spp.) in open plains areas to urial (Ovis vignei) in mountains because of gazelle populations declines due to anthropogenic influences. We also quantified recent prey choice of Asiatic cheetahs and their behavioral plasticity in foraging different prey species types. Although ethnobiological and historical records suggested that gazelle species were the main prey for cheetahs across their Asian range. However, urial were also commonly reported to be hunted by cheetahs across their historical Asian range, showing that the predation on mountain ungulates is not an emerging hunting behavior in Asiatic cheetahs. We found spatiotemporal plasticity in recent hunting behavior of cheetahs with selective predation on adult urial males. There was temporal overlap in hunting times for plains dwelling versus mountain ungulates, albeit with some minor differences with morning mostly for gazelles while the predation on mountain ungulates was predominantly post-midday. We provided three management implications for the recovery and restoration of cheetahs in Asia. Our work highlighted the importance of historical studies in informing the behavioral ecology of rare species.

Volatile organic compounds influence prey composition in Sarracenia carnivorous plants.

Sarracenia pitcher plants display interspecific differences in prey, so far only explained by pitcher morphology. We hypothesized that pitcher odours play a role in prey composition. We first compared odour and prey compositions among Sarracenia taxa grown together, forming a kinship gradient from S. purpurea known to capture primarily ants towards S. leucophylla known to capture many flying insects: S. purpurea, S. X mitchelliana, and S. X Juthatip soper & S. X leucophylla horticultural hybrids. We then measured several pitcher traits to disentangle the contributions of morphology and odour to prey variation. The pitcher odours were as diverse as those of generalist-pollinated flowers but with notable differences among taxa, reflecting their relatedness. VOC similarity analyses revealed taxon specificities, that mirrored those revealed by prey similarity analyses. S. X leucophylla stood out by being more specialised in flying insects like bees and moths and by releasing more monoterpenes known to attract flower visitors. S. X Juthatip soper trapped as many bees but fewer moths, sesquiterpenes contributing less to its scent. Ants and Diptera were the main prey of the other two with fatty-acid-derivative-dominated scents. Quantities of the different prey groups can be inferred 98% from quantities of the odour classes and pitcher dimensions. Two syndromes were revealed: ants associated with fatty-acid-derivatives and short pitchers; flying insects associated with monoterpenes, benzenoids and tall pitchers. In S. X leucophylla, emission rate of fatty-acid-derivatives and pitcher length explained most variation in ant captures; monoterpenes and pitcher length explained most variation in bee and moth captures; monoterpenes alone explained most variation in Diptera and wasp captures. Our results suggest that odours are key factors of the diet composition of pitcher plants. They support the hypothesis of perceptual exploitation of insect biases in carnivorous plants and provide new insights into the olfactory preferences of insect groups.

Warming increases survival and asexual fitness in a facultatively sexual freshwater cnidarian with winter diapause.

Temperature is a key abiotic factor controlling population dynamics. In facultatively sexual animals inhabiting the temperate zone, temperature can regulate the switch between asexual and sexual modes of reproduction, initiates growth or dormancy, and acts together with photoperiod to mediate seasonal physiological transitions. Increasing temperature due to recent global warming is likely to disrupt population dynamics of facultatively sexual animals because of the strong temperature dependence of multiple fitness components. However, the fitness consequences of warming in these animals are still poorly understood. This is unfortunate since facultatively sexual animals-through their ability for asexual reproduction resulting in quick population growth and sexual reproduction enabling long-term persistence-are key components of freshwater ecosystems. Here, I studied the fitness effects of warming in Hydra oligactis, a freshwater cnidarian that reproduces asexually throughout most of the year but switches to sexual reproduction under decreasing temperatures. I exposed hydra polyps to a simulated short summer heatwave or long-term elevated winter temperature. Since sexual development in this species is dependent on low temperature, I predicted reduced sexual investment (gonad production) and elevated asexual fitness (budding) in polyps exposed to higher temperatures. The results show a complex effect of warming on sexual fitness: While gonad number decreased in response to warming, both male and female polyps exposed to high winter temperature were capable of multiple rounds of gamete production. Asexual reproduction and survival rate, on the contrary, clearly increased in response to higher temperature, especially in males. These results predict increased population growth of H. oligactis in temperate freshwater habitats, which will likely affect the population dynamics of its main prey (freshwater zooplankton), and through that, the whole aquatic ecosystem.

Free-ranging livestock affected the spatiotemporal behavior of the endangered snow leopard (Panthera uncia).

Long recognized as a threat to wildlife, particularly for large carnivores, livestock grazing in protected areas can potentially undermine conservation objectives. The interspecific interactions among livestock, snow leopards (Panthera uncia), and their wild prey in fragile Asian highland ecosystems have been a subject of debate. We strategically deployed 164 camera traps in the Wolong National Nature Reserve to systematically investigate the activities of snow leopards, their primary wild ungulate prey species, and free-ranging livestock. We found that snow leopard habitat use was influenced by both wild prey and livestock. Blue sheep served as the main wild prey that spatially attracted snow leopards and coexisted with yaks while free-ranging yaks significantly restricted snow leopard habitat use both temporally and spatially. This study challenges the conventional understanding that livestock indirectly impacts large carnivores by competing with and displacing wild prey. Our findings highlight that free-ranging yaks within the alpine canyon terrain could directly limit snow leopard habitat use, suggesting a potential risk of grazing in reducing apex predator distribution and jeopardizing their populations. Consequently, managing their coexistence in shared habitats requires a more nuanced approach. Furthermore, our research underscores the importance of further research efforts aimed at enhancing our comprehension of the complex interplay within animal communities and ecosystems. This knowledge will contribute to the development of informed, evidence-based conservation strategies and policies.

Contrasting environmental conditions precluded lower availability of Antarctic krill affecting breeding chinstrap penguins in the Antarctic Peninsula

Dramatic decreases of chinstrap penguin populations across the Antarctic Peninsula (AP) are thought to be influenced by climate-driven changes affecting its main prey, the Antarctic krill, however, empirical evidence supporting such hypotheses are scarce. By coupling data on breeding chinstrap penguins, environmental remote sensing and estimates of krill acoustic density, we were able to demonstrate that penguins substantially increased their foraging effort in a year of low krill availability, with consequent reduction in breeding success. A winter of low sea ice cover followed by a summer/spring with stronger wind and lower marine productivity explained the lower and deeper krill availability. Our results highlight the importance of environmental variability on penguin populations, as variability is expected to increase under climate change, affecting foraging behaviour responses.

Post-fledging survival of Tengmalm’s owl offspring in boreal forests: Interactive effects of varying dynamics of main prey and habitat composition

The knowledge about the mortality rate of offspring is crucial for estimating bird population dynamics and conserving species with declining populations. Parents of predatory birds provide food for their offspring during the post-fledging dependency period, which is frequently described as essential due to inexpert flying skills. Using radio telemetry, we studied fledglings’ probability of dying by starvation and predation in Tengmalms’ owls (Aegolius funereus). Nestlings (21 and 39) from 10 and 14 broods in 2019 and 2021, respectively, were equipped with leg-mounted tags and monitored throughout the post-fledging dependency period in west-central Finland. In total, 28 out of 60 fledglings did not survive the post-fledging dependency period (12 died due to starvation, and 16 were predated). The fledglings’ probability of dying by starvation and predation was 3.7 and 2.4 times higher, respectively, in the decreasing (2019) than during the increasing (2021) abundance of main foods (voles), showing that prey availability is essential for survival during the post-fledging dependency period. The probability of starvation increased with augmenting agricultural lands in the home range and increasing precipitation after fledging, which indicated that parent owls avoided hunting in open areas and during rainy nights. The predation rate during the post-fledging dependency period increased with augmenting cover of old-growth forests in the home range. This result suggested that coverage of old-growth forests is nowadays so small in the study area that they act as ecological traps for newly-fledged owlets. The reason is that the main avian enemies of Tengmalm’s owls’ (goshawks and Ural owls) also prefer old-growth forests for breeding and hunting.

Resource Use among Six Commercial Fish Species from the South-Eastern Gill Net Fisheries, Korea

Dietary habits and inter-specific differences in resource use among six commercial fish species, Chelidonichthys spinosus, Cleisthenes pinetorum, Glyptocephalus stelleri, Hexagrammos otakii, Lophius litulon, and Sebastes schlegelii, collected from the southern coast of the East Sea, Korea, were analyzed using stomach content and stable isotope analyses. Teleosts were the main prey items for C. pinetorum and L. litulon, while both crabs and teleosts contributed to the diets of C. spinosus and S. schlegelii. Glyptocephalus stelleri mainly consumed polycheates and carid shrimps, and H. otakii mostly ingested crabs. The composition of prey items was significantly different in the diets of the six fish species. Further, carbon (δ13C) and nitrogen (δ15N) stable isotope values were significantly different among the six species, indicating different trophic positions. L. litulon, C. pinetorum, and S. schlegelii had narrow niches, whereas C. spinosus, G. stelleri, and H. otakii had relatively wider niches. This study demonstrated differences in patterns of food resource use among the six fish species that were categorized into two patterns of resource use according to their main prey items: diet diversity, trophic niche width, and trophic position. These results could contribute to the understanding of trophic relationships among fish species inhabiting the East Sea, Korea.

Multi-trophic occupancy modeling connects temporal dynamics of woodpeckers and beetle sign following fire.

In conifer forests of western North America, wildlife populations can change rapidly in the decade following wildfire as trees die and animals respond to concomitant resource pulses that occur across multiple trophic levels. In particular, black-backed woodpeckers (Picoides arcticus) show predictable temporal increases then declines following fire; this trajectory is widely believed to be a response to the woodpeckers' main prey, woodboring beetle larvae of the families Buprestidae and Cerambycidae, but we lack understanding of how abundances of these predators and prey may be associated in time or space. Here, we pair woodpecker surveys over 10 years with surveys of woodboring beetle sign and activity, collected at 128 survey plots across 22 recent fires, to ask whether accumulated beetle sign indicates current or past black-backed woodpecker occurrence, and whether that relationship is mediated by the number of years since fire. We test this relationship using an integrative multi-trophic occupancy model. Our results demonstrate that woodboring beetle sign is a positive indicator of woodpecker presence 1-3 years following fire, an uninformative indicator from 4-6 years after fire, and a negative indicator beginning 7 years following fire. Woodboring beetle activity, itself, is temporally variable and dependent on tree species composition, with beetle sign generally accumulating over time, particularly in stands with diverse tree communities, but decreasing over time in Pinus-dominated stands where faster bark decay rates lead to brief pulses of beetle activity followed by rapid degradation of tree substrate and accumulated beetle sign. Altogether, the strong connections of woodpecker occurrence to beetle activity support prior hypotheses of how multi-trophic interactions govern rapid temporal dynamics of primary and secondary consumers in burned forests. While our results indicate that beetle sign is, at best, a rapidly shifting and potentially misleading measure of woodpecker occurrence, the better we understand the interacting mechanisms underlying temporally dynamic systems, the more successfully we will be able to predict the outcomes of management actions.

Integrated approach considering seasonal variability and habitat uncertainty to map habitat for the prey of South China tiger

Improving connectivity is the most commonly used approach employed in biodiversity conservation to mitigate habitat fragmentation. Graph-based networks relying on species-oriented definitions of nodes and edges are powerful tools for evaluating landscape connectivity. However, few studies have examined the effects of seasonal variation and uncertainty in parameterization of habitat suitability on the identification of priority sites. Here, a combination of the habitat suitability index, morphological spatial pattern analysis (MSPA), and graph-network analysis were combined to assess the influence of habitat variability on the identification of priority sites for reintroduction of South China tiger (Panthera tigris amoyensis). The combined approach was applied to the Hupingshan and Houhe National Nature Reserve and neighbourhood that are considered the most suitable places to harbour small populations of South China tigers. Six spatial or temporally static assessment scenarios for habitat suitability were used to account for uncertainties in the habitat requirement parameterizations of wild boars as the main prey for South China tigers. For each assessment scenario, three classification schemes (i.e., the P50, P70, and P90 schemes) were adopted to explain uncertainties in priority sites evaluation. In the static scenario, the minimum area of priority sites in the P50, P70, and P90 schemes was 321, 354, and 2,371 km2, respectively, while the areas encompassed by priority sites in the P50, P70, and P90 schemes considering the seasonal variability and habitat uncertainty were 0.2, 1.6, and 229.5 km2, respectively. These results suggest that priority areas with high conservation value differed among the six assessment scenarios. Conservation planning of landscapes consequently should consider the impacts of changes in landscape structures caused by seasonal variation and uncertainty in the parameterization of habitat suitability for the assessment of landscape priority sites rather than relying on purely spatial or temporally static connectivity analyses.