Abundant Food Resources Research Articles

Coexistence within an endangered predator–prey community in California vernal pools

Abstract Globally endangered ecosystems, such as ephemeral wetlands, are often critical habitat for multiple interacting imperilled species. To conserve this biodiversity, managers must consider both species‐specific resource requirements and mechanisms for endangered species coexistence under variable habitat conditions. We examined communities native to California playa pools, ephemeral wetlands that have declined by >90% from their historic extent. Specifically, we describe the diet of a federally Threatened amphibian (Ambystoma californiense), and characterise interactions between this amphibian and two federally Endangered macrocrustaceans (Branchinecta conservatio and Lepidurus packardi) across three rain years to understand how these imperilled species coexist. We examined the dietary preferences of A. californiense larvae, metamorphs, juveniles, and breeding adults, and determined how prey electivity by larval A. californiense differs between natural playa pools and human‐modified stock ponds. Within playa pools, both breeding adult and larval A. californiense preyed extensively on L. packardi, whereas fully terrestrial juveniles had relatively empty stomachs. We provide evidence for size‐moderated optimal foraging by larval A. californiense, and show that larval prey differed dramatically between playa pools and stock ponds. Additionally, an ontogenetic progression from smaller to larger prey gave the relatively large, endangered macrocrustaceans an early‐season temporal refuge, during which they reached maturity in all three rain years. Consistent with complex life cycle theory, our results suggest that ephemeral wetland habitat offers abundant food resources for A. californiense relative to terrestrial habitat. Our findings also suggest that diet flexibility facilitates the persistence of this imperilled amphibian in human‐modified stock ponds. Temporal offsets in prey maturation rates and ontogenetic shifts in predator diets are likely to facilitate coexistence among the focal endangered species. We highlight the importance of accounting for spatial and temporal variation in interspecific interactions when predicting the effects of environmental change on biodiversity, particularly in highly threatened ecosystems.

Evaluating candidate wetlands for the assisted colonization of the western swamp turtle Pseudemydura umbrina in a changing climate: Macro‐invertebrate food resources and turtle diet

Abstract The natural habitat of the western swamp turtle (Pseudemydura umbrina Siebenrock, 1901) – the ephemeral, winter wet swamps north of Perth, Australia – is in danger owing to climate change and habitat fragmentation. The decline in rainfall in this area over the last five decades is predicted to continue, shortening the annual activity period for the turtles and potentially shifting their optimal climate zone to the south. Assisted colonization to wetlands in the cooler far south west of the state is one management response. As a contribution to such a measure, the diversity and abundance of food resources and consumption by turtles were evaluated at two potential and one existing colonization site. Thirty‐five captive‐bred juvenile P. umbrina were temporarily released into three sites: Moore River Nature Reserve north of Perth (into which the species had already been successfully translocated) and Meerup and East Augusta in the cooler far south of Western Australia. Food resources were assessed using sweep nets to sample invertebrates on two occasions at each wetland. Separate samples were collected for biomass determination and for assessing invertebrate diversity. Feeding by turtles was assessed by stomach flushing. Neither biomass nor biodiversity differed significantly between the southern sites and the reference site north of Perth. Stomach contents varied greatly, from 0 to 62 animals per turtle. The main prey items were beetles, ostracods, isopods and tadpoles. Each candidate wetland provided adequate food resources, indicating that assisted colonization to the cooler south coast of Western Australia has the potential to become a reasonable conservation tool to ensure the long‐term survival of P. umbrina.

Ontogenetic habitat shifts and vulnerability: lake-outlet-spawning sockeye salmon (Oncorhynchus nerka) sensitivity to habitat connectivity and hydrologic change

Sockeye salmon that spawn downstream of rearing lakes are an important example of the challenges faced by organisms with complex life histories requiring connectivity in aquatic habitat complexes. Specifically, newly emerged juvenile sockeye salmon must migrate upstream, against the flow of water, if they are to reach lake rearing habitat. Here, we examine the spatial and temporal dynamics of the water velocity landscape and juvenile sockeye salmon movement and condition at increasing distances downstream from the lake outlet of an important sockeye salmon system, the Babine Lake of British Columbia, one of Canada’s largest and most important sockeye salmon rearing lakes. The results of this study indicate that (i) there were seasonal and spatial patterns of water velocities that exceed the ability of juveniles to swim upstream to lake rearing habitat, (ii) higher water discharge was associated with more velocity barriers and potentially with less upstream movement of juveniles, and (iii) juveniles rearing in the lake obtained larger sizes (30% longer and 150% heavier) than those in downstream river habitats. Multiple processes that may be influencing these patterns could include more abundant food resources, lower metabolic demands, or size-selective immigration, emigration, or mortality among habitats. Years and seasons with high discharge may temporarily create one-way, downstream transport routes at lake outlets. Long-term changes in hydrology, perhaps driven by climate variability or land-use change, may control the degree to which lake outlets function as bidirectional travel corridors or one-way travel routes for young sockeye salmon.

Feeding habits of the spotted rose snapper, Lutjanus guttatus, (Actinopterygii, Perciformes, Lutjanidae), in the central Gulf of California, BCS, Mexico

The spotted rose snapper,Lutjanus guttatus(Steindachner, 1869), is an important resource for the coastal fisheries of the Gulf of California, mainly due to its high commercial value. Despite this, there are no management measures for this species, owing in part to a lack of information on its basic biology and its trophic ecology in the area. In this context, the presently reported study had as objective to describe the feeding habits ofL. guttatusthrough stomach content analyses, as well as to describe possible changes linked to sex, size, and season. Specimens were caught monthly from June 2016 to September 2017 with gillnets in Santa Rosalía, BCS, Mexico. The abundance, weight, and frequency of occurrence of each prey were assessed, and these parameters were integrated into the index of relative importance (%IRI) to determine the importance of each prey item in theL. guttatusdiet. The Levin’s index was used to assess the trophic niche width of the species, the feeding strategy was evaluated using Costello’s graphic method and the trophic level was calculated. Finally, to establish whether there were significant differences in the diet by sex, size, or season a PERMANOVA test was used with a 95% confidence level. A total of 202L. guttatusstomachs were analyzed, 191 of which contained food. A total of 26 prey items were identified. According to the %IRI, the most important prey were the teleost fishesHarengula thrissina(Jordan et Gilbert, 1882) (45.7%) andSardinops sagax(Jenyns, 1842) (34.8%), the euphausiidNyctiphanes simplex(13.4%), and the crustaceanPenaeusspp. (5.6%). The PERMANOVA analysis resulted in significant differences between the analyzed categories; however, there were no significant differences in the interactions among the categories. According to Levin’s index,L. guttatushad a narrow trophic width, with changes in the main prey consumed by the different categories. According to our results,L. guttatuscan be considered a benthopelagic opportunistic carnivorous predator with a narrow trophic niche, presenting mostly quantitative variations in its diet according to sex, size, and season. Its trophic plasticity allows it to take advantage of the most available and abundant food resources.

Environmental and periphyton response to stream revitalization – A pilot study from a tufa barrier

The formation of tufa barriers is driven by specific physicochemical and biological factors which make them very sensitive to environmental changes. The barriers provide great microhabitat complexity and are therefore inhabited by various periphytic organisms, whose metabolic activity alters the microenvironment, directly or indirectly affecting the physicochemical conditions of calcite precipitation. After the invasive plant species Ailanthus altissima (Mill.) Swinge was identified as one of the main factors causing current dryness of streams at the Skradinski buk barrier (Krka National Park, Croatia), the invasive species was removed, resulting in changes in the hydromorphology of the barrier and reactivating previously dry streams. The objective of this study was to determine potential differences between control and revitalized sites (reactivated streams) with regards to periphyton and the associated environmental changes over an annual cycle. Clear patterns were observed between sites reflecting the substantial changes in the landscape following invasive species removal. Revitalized sites had lower flow velocity, conductivity, pH, alkalinity and total water hardness values while exhibiting higher values of dissolved organic matter, nitrites and orthophosphates due to the presence of soil-derived organic material and intensive soil drainage. Organic matter content was generally higher at revitalized sites but did not inhibit tufa deposition. The influence of the surrounding forest soil was reflected not only in the mineralogical analysis of tufa sediment, but also in the abundance and diversity of periphyton. Revitalized site communities exhibited higher abundance and diversity and were dominated by bacterivorous and omnivorous ciliates and cercozoans due to the abundant food resources of the soil. The results presented show that ecosystem responses to hydromorphological changes generated by invasive species removal can be efficiently detected and monitored at microscale (i.e., periphyton scale) through a comprehensive interdisciplinary approach. As the first study to examine the relationship between aquatic ecosystems and sediments in the context of tufa stream revitalization, this pilot study provides data and guidelines for future management plans applicable to various tufa depositing systems facing invasive species propagation, allowing better understanding and protection of this unique and vulnerable karstic feature.

Response of aquatic macroinvertebrate density and diversity to wetland management and structure in the Montezuma Wetlands Complex, New York

We investigated how water management and other covariates affected aquatic macroinvertebrate density and diversity of wetlands in the Montezuma Wetlands Complex (MWC) of the Lake Ontario watershed, New York, USA. We conducted aquatic macroinvertebrate sampling during May–July in 2016–2018 to coincide with when juvenile wetland birds require these protein foods. Models that best explained aquatic macroinvertebrate density and taxon richness included water drawdown treatment, water depth, and water drawdown treatment from the prior year. Predicted mean density of aquatic macroinvertebrates was 117.2% greater in partial drawdown than passive wetlands (i.e., wetlands without active water removal) and increased by 516.2% with 15.5–48 cm increase in water depth. Density of aquatic macroinvertebrates also was ≥ 2.6 times greater in wetlands with a full drawdown the year prior. Taxon richness and Shannon Wiener Diversity Index (H′) varied positively with water depth, and there was greater diversity in partial drawdown than passive wetlands. Taxon richness was nearly 2 times greater in areas with full drawdown the year prior than those with partial drawdowns and passive wetlands. Other competing models for H′ also included negative effects of percentage monotypic cattail and invasive plant taxa. These findings are consistent with aquatic macroinvertebrate adaptation to dynamic wetland hydrology, and we recommend that managers actively manipulate hydrology to provide abundant and diverse food resources for birds at managed wetlands in the Great Lakes region.

Reconciling fish and farms: Methods for managing California rice fields as salmon habitat.

Rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the past century. Recently, through cooperative agreements with diverse stakeholders, winter-flooded agricultural rice fields in California’s Central Valley have emerged as ecologically functioning floodplain rearing habitat for juvenile Chinook Salmon. From 2013 to 2016, we conducted a series of experiments examining methods to enhance habitat benefits for fall-run Chinook Salmon reared on winter-flooded rice fields in the Yolo Bypass, a modified floodplain managed for flood control, agriculture, and wildlife habitat in the Sacramento River Valley of California. Investigations included studying the effect of 1) post-harvest field substrate; 2) depth refugia; 3) duration of field drainage; and 4) duration of rearing occupancy on in-situ diet, growth and survival of juvenile salmon. Post-harvest substrate treatment had only a small effect on the lower trophic food web and an insignificant effect on growth rates or survival of rearing hatchery-origin, fall-run Chinook Salmon. Similarly, depth refugia, created by trenches dug to various depths, also had an insignificant effect on survival. Rapid field drainage yielded significantly higher survival compared to drainage methods drawn out over longer periods. A mortality of approximately one third was observed in the first week after fish were released in the floodplain. This initial mortality event was followed by high, stable survival rates for the remainder of the 6-week duration of floodplain rearing study. Across years, in-field survival ranged 7.4–61.6% and increased over the course of the experiments. Despite coinciding with the most extreme drought in California’s recorded history, which elevated water temperatures and reduced the regional extent of adjacent flooded habitats which concentrated avian predators, the adaptive research framework enabled incremental improvements in design to increase survival. Zooplankton (fish food) in the winter-flooded rice fields were 53-150x more abundant than those sampled concurrently in the adjacent Sacramento River channel. Correspondingly, observed somatic growth rates of juvenile hatchery-sourced fall-run Chinook Salmon stocked in rice fields were two to five times greater than concurrently and previously observed growth rates in the adjacent Sacramento River. The abundance of food resources and exceptionally high growth rates observed during these experiments illustrate the potential benefits of using existing agricultural infrastructure to approximate the floodplain wetland physical conditions and hydrologic patterns (shallow, long-duration inundation of cool floodplain habitats in mid-winter) under which Chinook Salmon evolved and to which they are adapted.

Juvenile migration of Japanese dace Pseudaspius hakonensis revealed in a tributary of Lake Biwa with seasonal changes in abundance and stable isotope ratios

Migration patterns of Japanese dace Pseudaspius hakonensis in and around Lake Biwa, Japan are unknown, although fluvial–lacustrine life history has been known in most tributaries, the many mature individuals migrating upstream into tributaries in early spring. Field surveys and stable isotope analyses were used to clarify the migratory history of Japanese dace in the Ishida River, inflowing to Lake Biwa. In the field surveys, the number of young of the year (YOY) individuals caught per unit effort (CPUE) by hand net and casting net in the tributary and lake-shore area was calculated. The CPUE peaked from May to July, after the spawning season, thereafter decreasing rapidly, suggesting that YOY Japanese dace migrated downstream to Lake Biwa immediately after emerging, possibly due to the abundant food resources there. From September to November, the CPUE of YOY individuals increased in the lower reaches of the stream, although their stable nitrogen isotope values were variable, in some cases being similar to those recorded in the upper reaches and the lake-shore area. This suggests that some YOY individuals migrate upstream from the lake in autumn. In the present study, the juvenile migration pattern of fluvial–lacustrine Japanese dace in Lake Biwa was described using a CPUE survey and δ15N and δ13C analyses.

Factors limiting kererū (Hemiphaga novaeseelandiae) populations across New Zealand

Kererū declined rapidly following European settlement in New Zealand, and they remain at a reduced density. We assessed three sources of information to test the hypothesis that predation by introduced mammals and abundance of food resources are the two major factors determining kererū abundance across New Zealand. First, we reviewed the literature on factors affecting the vital rates of kererū. This analysis showed that predation is the cause of most nest failures and deaths in kererū. Second, we examined data from a major database of bird sanctuary outcomes across New Zealand to evaluate long-term responses of kererū to intensive pest control at local scales. Kererū detections did not always increase following predator control, which suggests that food supply or forest area may be more important limiting factors at some sanctuaries. Third, to understand the factors underlying temporal and spatial kererū distribution patterns at a national scale, we assessed changes and patterns in kererū local occupancy through time using data from the 1969–1979 and 1999–2004 editions of the Atlas of Bird Distribution in New Zealand. Specifically, we asked (1) whether there have been declines in kererū occupancy between the two Atlases, and (2) how patterns of kererū occupancy relate to indigenous forest cover, temperature, urbanisation, and forest type (podocarp or beech dominated). Kererū occupancy remained stable across the North Island between the two time periods but declined in the South Island. Across both islands and time periods, kererū occupancy decreased significantly as forest cover decreased, which suggests that forest availability is still a major limiting factor across some parts of New Zealand. Overall, our results support previous studies showing that predation by introduced mammals is the primary limiting factor for kererū in forests, but also highlight the importance of forest area and food supply for kererū recovery.

Foraging guild structure and niche characteristics of wintering waterbirds at Lake Shengjin, lower reaches of the Yangtze River

集团结构和生态位特征是量化动物群落组织过程的重要指标，鸟类集团结构及其食物资源分割的分析对于理解群落中不同鸟种生态适应性具有重要意义.越冬水鸟集团结构和生态位特征取决于食物资源的丰富度和可获得性.本文通过对升金湖越冬水鸟的觅食生境和觅食行为的观察，对水鸟群落的集团结构进行划分，采用Levins指数和Pianka指数计算生态位宽度和生态位重叠度.结果表明，升金湖越冬水鸟可被划分为4个觅食集团，即G1浅水啄食集团、G2草滩啄食集团、G3广食性集团和G4深水潜水觅食集团.在浅水和中水区的觅食集团物种组成比深水区的水鸟集团丰富.G3广食性集团的生态位宽度远高于其余3个特化集团.比较而言，所有水鸟物种的觅食行为均较特化，但在觅食生境方面却较宽化.同一集团内物种间的生态位重叠远高于集团间的生态位重叠.G3广食性集团内物种的生态位重叠度低于其它特化集团内物种的生态位重叠度.研究结果表明，升金湖越冬水鸟群落集团结构主要受食物资源空间配置及其可利用性的影响.水鸟群落结构和生态位特征的信息对监测升金湖湿地的质量和制定有效的湿地保护策略都具有重要意义.;Guild structure and niche characteristics are important indicators to quantify the assemble process of animal community. It is of great significance to analysis bird guild structure and food resource partitioning for understanding ecological adaptability of different bird species in a community. The guild structure and niche characteristics of wintering waterbirds depend on the abundance and availability of food resources. In this study we divided the guild structure of waterbird community based on the data of foraging habitat and foraging behavior of wintering waterbirds collected at Lake Shengjin, and calculated the niche width and niche overlap using Levin's index and Pianka index. The results showed that the waterbirds at Lake Shengjin can be divided into four different foraging guilds, namely the G1, pickers in shallow-water, G2, pickers in grassland, G3, generalists and G4, divers. The species composition of foraging guilds in shallow and middle-depth water is richer than that in deep water. The niche width of G3 generalists is much higher than that of the other three specialized species guilds. In comparison, the foraging behavior of all waterbird species is more specialized, but the foraging habitat is more generalized. The niche intra-guild overlap of waterbird species is much higher than that of inter-guilds. The niche overlap of species in G3 generalist is lower than that in other specialized guilds. The results show that the guild structure of wintering waterbird community at Lake Shengjin mainly affected by the spatial allocation and availability of food resources. The information of water bird community structure and niche characteristics is of great significance for monitoring the quality of Lake Shengjin wetland and developing effective wetland protection strategies.

Habitat selection of foraging male Great Snipes on floodplain meadows: importance of proximity to the lek, vegetation cover and bare ground

Drainage of wetlands and agricultural intensification has resulted in serious biodiversity loss in Europe, not least in grasslands. Consequently, many meadow birds have drastically declined, and the habitats they select for breeding currently rely on land management. However, the selection of habitats maintained by agriculture may contribute to reduced fitness and thus remain maladaptive for individuals, which makes conservation challenging. An understanding of the relationships between species’ habitat selection, food supply and land management in the context of species’ behaviour is therefore crucial for conservation. Lowland populations of Great Snipe Gallinago media are currently declining at a moderate rate, causing a conservation concern. We examined the daytime site selection (assumed as foraging sites) and food supply of radiotracked Great Snipe males breeding on a floodplain in NE Poland. Foraging sites were classified at micro‐ and macro‐scale levels using the logistic regression in a use–availability design. On the micro‐scale level, males selected moderate sward height and density, and a large amount of bare ground patches, and the importance of these increased as the breeding season progressed. On the macro‐scale level, these conditions were associated with (1) meadows mown twice per season and grazed thereafter (associated with the most abundant food resources – earthworms) and (2) extensively managed pastures, suggesting the importance of grazing. Abandoned or late‐mown meadows under agri‐environmental schemes (AES) were avoided by foraging males. However, parcels with delayed mowing offer safe breeding sites for females nesting close to leks, unlike land‐use types preferred by foraging males, which may act as an ecological trap. Effective conservation of Great Snipes on floodplain meadows requires precisely targeted AES schemes that will provide a mosaic of intensive and extensive land‐use patches in the vicinity of identified leks.

The economics of territory selection

Territorial behavior is a fundamental and conspicuous behavior within numerous species, but the mechanisms driving territory selection remain uncertain. Theory and empirical precedent indicate that many animals select territories economically to satisfy resource requirements for survival and reproduction, based on benefits of food resources and costs of competition and travel. Costs of competition may vary by competitive ability, and costs of predation risk may also drive territory selection. Habitat structure, resource requirements, conspecific density, and predator distribution and abundance are likely to further influence territorial behavior. We developed a mechanistic, spatially-explicit, individual-based model to better understand how animals select particular territories. The model was based on optimal selection of individual patches for inclusion in a territory according to their net value, i.e., benefits (food resources) minus costs (travel, competition, predation risk). Simulations produced predictions for what may be observed empirically if such optimization drives placement and characteristics of territories. Simulations consisted of sequential, iterative selection of territories by simulated animals that interacted to defend and maintain territories. Results explain why certain patterns in space use are commonly observed, and when and why these patterns may differ from the norm. For example, more clumped or abundant food resources are predicted to result, on average, in smaller territories with more overlap. Strongly different resource requirements for individuals or groups in a population will directly affect space use and are predicted to cause different responses under identical conditions. Territories are predicted to decrease in size with increasing population density, which can enable a population's density of territories to change at faster rates than their spatial distribution. Due to competition, less competitive territory-holders are generally predicted to have larger territories in order to accumulate sufficient resources, which could produce an ideal despotic distribution of territories. Interestingly, territory size is predicted to often show a curvilinear response to increases in predator densities, and territories are predicted to be larger where predators are more clumped in distribution. Predictions consistent with empirical observations provide support for optimal patch selection as a mechanism for the economical territories of animals commonly observed in nature.

Human activities and elevational constraints restrict ranging patterns of snub-nosed monkeys in a mountainous refuge.

Both natural conditions and anthropogenic factors affect the survivability, distribution, and population density of wildlife. To understand the extent and how these factors drive species distributions, a detailed description of animal movement patterns in natural habitats is needed. In this study, we used satellite telemetry to monitor elevational ranges favored by endangered golden snub-nosed monkeys (Rhinopithecus roxellana), in the Qinling Mountains, central China. We investigated the abundance and distribution of food resources through sampling vegetation quadrats at different elevations and sampled anthropogenic activities using field surveys. Our results indicated that although there was no significant variation in food resources between low- (<1500 m) and middle-elevations (1500-2200 m), monkeys were found most often in areas above 1500 m, where there was less anthropogenic development (e.g. houses and roads); however, monkeys rarely ranged above 2200 m and had limited food availability at this altitude. There was limited human disturbance at this elevation. We suggest that both human activity and ecological constraints (i.e. food resources) have considerable effects on elevational use of R. roxellana in the Qinling Mountains. This study highlights the critical roles these factors can play in shaping the vertical distribution of high-altitude primates. This research provides useful insights for habitat-based conservation plans in which human disturbance management and habitat restoration should be prioritized.

Songbirds promote connectivity between riparian galleries and adjacent habitats

AbstractRiparian galleries are among the most vulnerable habitats in the world and are well known for their importance to the most specialized riparian bird species. In this study, we analyzed songbird composition, songbird diet, trophic ecology and seed dispersal in riparian galleries and adjacent Montado matrices in southern Portugal to address the importance of birds in promoting the connectivity between riparian galleries and adjacent habitats. We used fecal samples to compare diet, and blood samples to compare nitrogen stable isotopes from birds in these two habitats. The seasonal variation in the abundance of arthropods and fruits was evaluated in both habitats and seed movement between both habitats was assessed from fruits marked with fluorescence. Abundance of food resources for birds (arthropods and fruits) declined throughout the season in a similar way for both habitats, and there were strong similarities in the diet and trophic ecology of songbirds in the riparian gallery and adjacent habitat. In both habitats, birds preyed heavily on Hymenoptera and Coleoptera but birds more abundant in the Montado fed more on Araneae and Hymenoptera. Seeds were moved significantly more frequently from the riparian gallery into the adjacent Montado than vice‐versa. Our results suggest that birds from the adjacent habitat move frequently to the riparian gallery to forage and disperse seeds into the adjacent habitat as they depart. This study shows that birds play an important role in promoting connectivity between riparian galleries and adjacent habitats.

Assessing the regional landscape connectivity for multispecies to coordinate on-the-ground needs for mitigating linear infrastructure impact in Brasov – Prahova region

While many initiatives, studies and projects are focusing only on modelling wildlife connectivity movement, coordinated efforts should help to deliver adaptative solutions for the on-the-ground needs, while helping the planners and involving communities in landscape protection. Multispecies spatial models and maps allow the generalisation of findings across more significant regions and provide insights to maintain, improve or restore landscape connectivity, while individual species could contribute in establishing regions of focus in conservation efforts. Given the challenge of multispecies connectivity, we chose to build single connectivity models through circuit theory for brown bear, wolf, red deer, wild boar and roe deer. Further, we combined best-supported models in a regional cumulative spatial map, on which we identified areas of high importance for connectivity conservation to investigate and mitigate the impact of linear infrastructure. Results for carnivores and their prey species were similar to those obtained from brown bear landscape genetics modelling. Eastern slope facing was a clear preference of multispecies, and we trust this is due to abundant vegetation, food resources, and lack of fragmentation of forest regions. A vital area called Cold River corridor was validated both functional (brown bear) and structural (for carnivores and prey species) by this study and the results from previous research. However, a highway is planned to bisect the Cold River for the first time, and we advocate that the remaining conservation potential of the area should be maintained whenever possible while planning for evolutionary resilience and prioritizing management actions and effective strategies for all the species. Conservation easements could provide protections against development considered together with coordinated efforts for "smart development", and maintenance of existing forest and wildlife management and land uses preservation.

Factors influencing riverine utilization patterns in two sympatric macaques

Many species of terrestrial animals, including primates, live in varied association with the aquatic (e.g., riverine or coastal) environment. However, the benefits that each species receive from the aquatic environment are thought to vary depending on their social and ecological characteristics, and thus, elucidating those benefits to each species is important for understanding the principles of wild animal behaviour. In the present study, to gain a more complete picture of aquatic environment use, including social and ecological factors in primates, factors affecting riverine habitat utilization of two macaque species (Macaca nemestrina and M. fascicularis) were identified and qualitative comparisons were made with sympatric proboscis monkeys (Nasalis larvatus), which have different social and ecological characteristics. Temporal variation in sighting frequency of macaques at the riverbanks was positively related to the fruit availability of a dominant riparian plant species and negatively related to the river water level which affects the extent of predation pressure. Riverine utilization of macaques was greatly influenced by distribution and abundance of food (especially fruit) resources, possibly in association with predation pressure. Additionally, qualitative ecological comparisons with sympatric proboscis monkeys suggest that the drivers of riverine utilization depend on the feeding niches of the species, and different anti-predator strategies resulting from their differing social structures.

Littoral habitats as major nursery areas for fish species in estuaries: a reinforcement of the reduced predation paradigm

For many decades, the role of estuaries as important nursery areas for fishes was accepted as fact by scientists and environmental managers. At the turn of the 21st century, a question mark was raised in relation to the reduced predation component of the nursery function, with some scientists contending that both large and small piscivorous fish species had access to the estuarine habitats that juvenile fishes in estuaries occupied. If true on a global scale, the nursery designation for these habitats would be compromised and the long-held paradigm that estuaries are important nursery areas for fishes would need to be revised. In this review, I examine the nature of fish nursery areas in estuarine littoral habitats from a mainly predation perspective and, based on a variety of ichthyofaunal and avifaunal studies, come to the conclusion that apart from a few selected estuarine systems, there is limited predation on juvenile fishes in these particular areas. This, coupled with the abundant suitable food resources for juvenile fish from different trophic categories, shelter from high-energy marine wave action and biological connectivity between a variety of submerged and emergent macrophyte communities, renders shallow estuarine littoral areas ideal nursery areas for the juveniles of mostly euryhaline marine fish species, the dominant component of estuarine ichthyofaunas globally. In addition, there are strong indications from the fossil record that these littoral estuarine nursery areas have been functioning since the Devonian, more than 350 million years ago.

Prey Choice of Introduced Species by the Common Vampire Bat (Desmodus rotundus) on an Atlantic Forest Land-Bridge Island

The proliferation of native, alien, invasive and domestic species offers enough novel and abundant food resources for the common vampire bat, Desmodus rotundus, to potentially alter preferences for prey. By reference to a stable-isotope analysis for carbon and nitrogen, we report here on the choices of introduced mammal prey made by D. rotundus residing on Anchieta Island — a tropical land-bridge island from which domestic animals were removed and 100 individuals of 15 mammal species were introduced intentionally. Our analysis shows that the studied individuals of D. rotundus were more likely to prey upon species of open habitats (mean value of δ13C = -14.8‰), that is, animals with high δ13C values characterising the consumption of C4 resources. The δ15N values for D. rotundus were higher than expected, most likely similar to apex predator species (mean value of 8.2‰) and overlapped the isotopic niche with capybaras (Hydrochoerus hydrochaeris) on the island. Values were in turn distant from those noted for coatis, as well as other potential prey from a preserved area on the mainland (capybaras included), indicating that, from among all the potential mammalian prey species, the studied bats were feeding exclusively on capybaras, which also represent the species with the greatest mammalian biomass on the island. Previous information regarding the time of human occupation suggests that the domestic animals then present on Anchieta Island might have been the main prey of D. rotundus and responsible for maintaining a viable population. As capybaras were introduced only 36 years ago, this suggests a rapid shift in predation preference induced by anthropogenic disturbances that have allowed D. rotundus to exploit these rodents successfully. Records in the literature further show that common vampire bats were not captured in preserved areas of the mainland close to Anchieta Island, indicating that the rate of capture characterising D. rotundus is usually low in natural forested habitats where potential prey are scattered. As three individuals of the introduced population of capybaras were confirmed to have died from bat rabies virus (RABV) in 2020, we advocate periodic monitoring for bat rabies viruses in the D. rotundus population on Anchieta Island (as well as nearby areas), so that the magnitude of the outbreak may be determined and control strategies developed. Such actions are all the more important given that both the island and nearby areas are frequented by tourists. We highlight that the prey choice indicated here is context-dependent, and possibly influenced by the removal of domestic animals, as well as the explosive population growth achieved by the introduced capybaras, in combination with the predictability of their foraging behaviour.

Effect of conspecific neighbors on the foraging activity levels of the wintering Oriental Storks (Ciconia boyciana): Benefits of social information.

Animals prefer to aggregate in patches with high abundance and availability of food resources. Group foragers typically receive information about food resources by monitoring external events and the behavior of neighbors. The Information Centre Hypothesis proposes that aggregations increase foraging activity levels as a result of social information provided by conspecifics. Increasing the foraging rate has as a result decreasing time devoted to anti‐predator vigilance and may intensify competition among group members. Studies have shown that foraging activities are influenced by factors other than flock size, such as the number and foraging intensity of neighbors. To test these hypotheses, we examined the effect of number and foraging intensity of neighbors on the foraging activity levels (foraging rate, foraging effort, and foraging success rate) of the wintering Oriental Storks (Ciconia boyciana). In this study, we collected focal sampling data on the foraging behavior of storks at Shengjin Lake during winter from 2017 to 2019, controlling the effects of other variables (group identity, wintering years, and wintering periods). We found that foraging activity levels were higher in the presence of foraging neighbors than in their absence. Moreover, individuals adjusted their foraging activity levels according to social information gathered from the behavior of neighboring conspecifics. Focal individuals’ foraging rate and foraging effort were positively correlated with the average foraging rate of neighbors. Their foraging success rate was not influenced by the average foraging rate and foraging success rate of neighbors; however, it was positively correlated with the average foraging effort of neighbors. In conclusion, foraging activity levels of individuals are primarily driven by the intensity of the foraging activity of neighbors. This result differs from the results of previous studies that suggested that flock size was the most important factor determining individual foraging activity levels.

Seasonal demography of different black rat (Rattus rattus) populations under contrasting natural habitats in Guadeloupe (Lesser Antilles, Caribbean)

The black rat (Rattus rattus) is one of the most widespread rodents on islands worldwide, introduced over the last five centuries. However, reliable information concerning how biotic or abiotic factors influence key parameters of black rat population biology in insular contexts is currently unavailable. Here we aim to document the relative abundance of rat populations and evaluate how the age structure and the body mass of adult individual vary seasonally in different forest environments under contrasting climatic conditions. Rats were captured during wet and dry seasons in 2017–2018 at one or two sites in each of the four natural forested environments of Guadeloupe, all of which experience widely different annual rainfall (semi-deciduous dry forest, seasonal evergreen forest, mountain rainforest and Pterocarpus officinalis swamp forest). A total of 171 black rats were captured during a 1018 trap-night effort. Overall capture results confirm this species to thrive in all the natural forested environments we investigated. With the exception of the P. officinalis swamp forest, black rat populations reach higher relative abundances during the wet season due to juvenile and sub-adult recruitment at the end of the dry season. In contrast, in the P. officinalis swamp forest, breeding activity continues during both seasons and relative rat abundance appears to fluctuate less seasonally. The relative abundance of adult black rats is also higher in the seasonal semi-evergreen and rainforests that experience little or no water stress. These contexts therefore appear the most favourable for sustaining black rat populations, a pattern that is most likely connected to a combination of climatic and/or edaphic parameters that condition the year-round availability and abundance of food resources.