Natural Food Availability Research Articles

Growth and Development of Stadia Artemia salina in Culture with Different Concentration of Bran Suspension

The annual need for Artemia in Indonesia reaches 40-60 tons, but up to now 100% of this need is still imported. Various efforts have been made to produce Artemia cysts, but the main obstacle in cultivating Artemia to produce cysts is the availability of natural food, namely phytoplankton which can survive in high salinity. The use of organic materials such as bran can be a solution for feeding and can increase the density of Artemia, but excessive use of bran suspension in Artemia cultivation ponds can trigger a decrease in the quality of the water for the growth of Artemia. This research was conducted to determine the optimal concentration of bran feed for the growth and development of Artemia salina without compromising the water quality of the cultivation. The Artemia feed used in this study was a bran suspension enriched with lemuru fish oil (12 ml/L bran suspension). The bran feed concentration treatments in this study were 5 treatments sequentially, namely P1 to P5 with feed concentrations of 11, 18, 26.34, and 41 mg/L. Artemia salina cultivation in this study was carried out at an initial density of 50 ind/L with a salinity of 30 pptl. The research results showed that cultivating Artemia salina using bran suspension feed with different concentrations had an effect on the growth and development of Artemia salina. The best growth and development of Artemia results from cultivation using bran suspension feed with a concentration of 41 mg/L.

Predation can shape the cascade interplay between heterothermy, exploration and maintenance metabolism underhigh food availability.

Maintenance metabolism as the minimum energy expenditure needed to maintain homeothermy (a high and stable body temperature, T b), reflects the magnitude of metabolic machinery and the associated costs of self-maintenance in endotherms (organisms able to produce heat endogenously). Therefore, it can interact with most, if not all, organismal functions, including the behavior-fitness linkage. Many endothermic animals can avoid the costs of maintaining homeothermy and temporally reduce T b and metabolism by entering heterothermic states like torpor, the most effective energy-saving strategy. Variations in BMR, behavior, and torpor use are considered to be shaped by food resources, but those conclusions are based on research studying these traits in isolation. We tested the effect of ecological contexts (food availability and predation risk) on the interplay between the maintenance costs of homeothermy, heterothermy, and exploration in a wild mammal-the yellow-necked mouse. We measured maintenance metabolism as basal metabolic rate (BMR) using respirometry, distance moved (exploration) in the open-field test, and variation in T b (heterothermy) during short-term fasting in animals captured at different locations of known natural food availability and predator presence, and with or without supplementary food resources. We found that in winter, heterothermy and exploration (but not BMR) negatively correlated with natural food availability (determined in autumn). Supplementary feeding increased mouse density, predation risk and finally had a positive effect on heterothermy (but not on BMR or exploration). The path analysis testing plausible causal relationships between the studied traits indicated that elevated predation risk increased heterothermy, which in turn negatively affected exploration, which positively correlated with BMR. Our study indicates that adaptive heterothermy is a compensation strategy for balancing the energy budget in endothermic animals experiencing low natural food availability. This study also suggests that under environmental challenges like increased predation risk, the use of an effective energy-saving strategy predicts behavioral expression better than self-maintenance costs under homeothermy.

Cozy den or winter walk: the effects of climate and supplementary feeding on brown bear winter behavior

AbstractHibernation is a key adaptation for coping with unfavorable climatic conditions and low food availability in areas with severe winter conditions. While understanding the physiology and phenology of this adaptation has received considerable attention, comparatively little information is available on how hibernation will be affected by changing climate conditions. We used GPS telemetry data from 20 free‐ranging brown bears monitored over 31 winters between 2007 and 2022, to identify behavioral strategies of bears during winter. We applied behavioral change point analysis to quantify brown bears’ hibernation phenology in a population close to the bear's southern latitudinal range limit in Europe where supplementary food is available to bears year‐round. We observed winter behavior patterns that varied across age and reproductive classes but also within individuals between winters. Among 31 winter events, we registered six cases in which bears exhibited a single hibernation/stationary period and 19 events where hibernation was split into up to five stationary periods. Moreover, six winter events did not show behaviors consistent with hibernation and individuals remained partly or completely active throughout winter. The movement of these active bears decreased with increasing snow depth. In addition, these winter‐active bears showed higher fidelity to supplementary feeding sites during the winter period compared to the rest of the year. Our data suggest that an abundance of human‐provided food resources during winter may facilitate the emergence of different wintering strategies in brown bears. Furthermore, supplemental feeding sites in combination with predicted mild winters and prolonged natural food availability suggest that the use of hibernation as an energy‐saving strategy to overcome severe environmental conditions may decrease in the future.

A Study on Potential Feed Sources to Boost Guppy Fish, Poecilia reticulata Productivity

Aquaculture may simply be referred as “Underwater Agriculture.”India is a major maritime state and an important aquaculture- based country in the worldhaving major aquaculture activitiesin the production of Carp from Freshwater,Shrimp from Brackish water, etc. Feed requirements of fish vary in quantity and quality according to the feeding habits, physiological stages of the species and environmental variations viz., temperature; amount and type of natural food availability in the culture system.A nutritious and cheap feed is a pre requested for profitable aquaculture. Though, use of commercially available feed is in practice in many countries. The feed cost consumes more Than half of running expenditure. Therefore, the search of nutritionally well-balanced feed Prepared from very cheap locally available ingredients in progress in all the aqua farming countries. In the present study, an attempt has been made to well-balanced nutritious feed Particularly from the locally available cheaper ingredients. The objectives of the present study are: to assess the effect of feed on the growth of finfish and shellfish in the laboratory, to prepare the conventional feed with traditional ingredients and to check the effect of feed on the growth performance of ornamental fish - Guppy, Poecilia reticulata.

Natural Food Intake and Its Contribution to Tambaqui Growth in Fertilized and Unfertilized Ponds

Natural food available in ponds can complement formulated feed in fed aquaculture. This study elucidated the natural food intake and its contribution to tambaqui (Colossoma macropomum) growth in fertilized and unfertilized ponds, using stable isotope and stomach contents analyses. Additionally, it described the impact of fertilization management on natural food availability, fish performance, and production costs. Tambaqui juveniles (93.8 ± 15.0 g) were stocked (0.55 fish/m2) in fertilized (Fert) and unfertilized (NoFert) ponds (600 m2) for a culture period of 10 months in quadruplicate. A lower food conversion ratio was observed in Fert ponds. The main natural food items ingested by tambaqui were insects, vegetables, and cladocerans. Plankton contributed 39.4% and 10.7% of muscle formation in Fert and NoFert ponds, respectively. Pond fertilization (2.45 g of nitrogen and 0.80 g of phosphorus per square meter every two weeks) did not significantly affect fish growth, survival, or productivity but had a slightly influence on water quality parameters. However, fertilization increased the zooplankton density (through phytoplankton) in the water, thereby increasing autochthonous food availability for tambaqui consumption. This species demonstrates the ability to alternate between natural food sources and commercial feed without compromising its development. Consequently, tambaqui exhibits suitability for farming within restorative and integrated aquaculture systems as well as intensive systems reliant on commercial feed.

Phytoplankton in the Anchialine Habitat of Red Shrimp (Parhippolyte uveae) at Mangrove Ecosystem Waters

The anchialine habitat waters of this study is located at mangrove ecosystem around Koguna Beach area, Buton Island, Indonesia. It is a closed water, isolated from the sea, and inhabited by Parhippolyte uveae red shrimp. The existence of phytoplankton in this habitat can be used to determine the availability of natural food and the water quality of this shrimp’s habitat. This study was conducted to examine the presence of phytoplankton in the anchialine habitat of red shrimp. Phytoplankton samples were obtained by filtering water using Plankton Net. Meanwhile, several biological indexes such as the diversity index, evenness index, and dominance index were used to analyze the phytoplankton community. The result showed that this habitat was dominated by phytoplankton from the classes Bacillariophyceae, Florideophyceae, and Globothalamea with a total of 13 genera in September 2021 and Bacillariophyceae, Cyanophyceae, Dinophyceae, and Globothalamea with a total of 18 genera in December 2021. The most common type of phytoplankton found in the red shrimp habitat during the study was Navicula sp. with a ban of 1436 cells L-1 and 479 cells L-1 in September 2021 and December 2021, respectively. The diversity index of phytoplankton in this habitat was low, meanwhile, the index of evenness and dominance indicated that this habitat was of good quality (evenness index was high and dominance index was low). This study can be used as a basic information for further research on the management control for this species habitat.

Ecological Insights, and Fin Fish Diversity in Carps Spawning Grounds: Case Studies from the Surma River and Tanguar Haor, Bangladesh.

This study aims to provide a thorough ecological understanding of fin fish diversity within carp spawning grounds in the Surma River and Tanguar haor. Over two spawning seasons, this research investigates ecological factors impacting fin fish diversity and abundance in carp spawning grounds of the Surma River and Tanguar haor, emphasizing water quality, habitat features, spawn availability, and environmental influences. Fish spawn samples were collected with eight "Savar nets" at chosen sites and reared in a fiberglass tank at the mini hatchery for species identification. The representative spawn samples were examined under a microscope for preliminary species identification before rearing. The study found that both the Surma River and Tanguar haor offer ideal conditions for carp spawning due to factors such as water quality, natural food availability, habitat suitability, and favorable climatic conditions. The study identified 39 fish species under the 10 fish groups from both locations, with a higher percentage of carp species (31.42%) in the Surma River in 2021 compared to 2022 (22.50%). In Tanguar haor, the percentage of carp species was 7.55% and 6.50% in 2021 and 2022, respectively. The Surma River's ecological indices (2021-2022) indicated decreased diversity, likely due to environmental degradation, while Tanguar haor showed lower diversity possibly attributable to multiple environmental stressors. The dominant carp species, Labeo calbasu, Labeo bata, and Labeo gonius, were identified in both the Surma River and Tanguar haor. The spawning distribution varied among different locations, with some sites showing a presence of carp species, such as Hajipur (T1) in the Surma River and Alam Duar (T2) in Tanguar haor. The findings highlight the importance of hydrological and environmental parameters in shaping carp spawning habitat distribution and abundance, contributing to aquatic biodiversity conservation and resource management.

Predictors of female American black bear body mass in an anthropogenic landscape

AbstractAnthropogenic pressure, such as urbanization and habitat loss, can wield many effects on wildlife that radiate through ecosystems. Large carnivores tend to experience these effects more severely than other species, diminishing their viability and altering ecosystem function by suppressing their role as an apex predator. Yet opportunistic carnivores that rely on an omnivorous diet can sometimes take advantage of anthropogenic food and improve their fitness prospects. We quantified the effect of phenotypic and ecological factors on female body mass of the American black bear (Ursus americanus) in New Jersey, USA. Habitat and reliable mast crops in New Jersey keep adult female black bear body mass and reproduction higher than many parts of the United States, and historically, female black bears in the mid‐Atlantic states tend to be larger than in other parts of their range. We used data collected from den surveys (n = 317) in northern New Jersey from 1984 to 2019 to examine the shared roles of climate, anthropogenic pressure (human food subsidies, harvest), habitat composition and configuration, natural food availability (hard mast production), and bear characteristics (age, history of human–black bear conflict) on female black bear body mass using generalized linear mixed models. Adult female body mass was heaviest with increased availability of cultivated crop and within low‐intensity developed land covers, suggesting anthropogenic food subsidies found in these 2 land cover types are contributing to female overall body mass. A history of conflict with humans explained heavier females, and a quadratic effect of age on body mass supported a senescent decline in adult female body mass later in life. Our results suggest that access to specific land cover types (i.e., crops, low‐intensity developments) that provide a diversity of food (e.g., corn, soft and hard mast) and support low human densities, explains female black bear body mass in a fragmented landscape.

Assessing the extent of land degradation in the eThekwini municipality using land cover change and soil organic carbon

ABSTRACT More than 75% of the global land has already suffered degradation, leading to the recognition of land degradation as one of the foremost challenges society faces. This recognition stems from its profound adverse impacts on natural ecosystem functioning, biodiversity, soil productivity, and food availability. Consequently, understanding the spatial distribution of land degradation across all scales becomes imperative. This study employed land cover change and soil organic carbon (SOC) stock assessments to analyse land degradation within the eThekwini Municipality beyond the baseline period (2000–2015). Utilizing remote sensing and machine learning techniques, this research examined land degradation within the eThekwini Municipality over the period spanning 2000 to 2022. Landsat 7 (Enhanced Thematic Mapper Plus – ETM+), Landsat 8 (Operational Land Imager 1 - OLI1), and Landsat 9 (Operational Land Imager 2 - OLI2) images were employed to extract variables for both land cover change and SOC stock prediction through XGBoost, LightGBM, Random Forest (RF), and Support Vector Machine (SVM) models. Among these models, LightGBM demonstrates superior performance, achieving an overall accuracy of 80.646 in land cover predictions and 77.869 in SOC stock predictions. Analysis of land cover change within the eThekwini Municipality unveiled a shift from forests and shrubland landscapes to cropland and built-up areas. This shift results in the municipality encountering losses in SOC stock between 2015 and 2022. The model predicted that most SOC stock losses occur at the 20–50 cm depth (9.27%), in comparison to the 7.21% loss at the 0–20 cm depth. These findings underscore the pivotal role of remote sensing and machine learning in aiding policymakers to assess land degradation and implement pertinent measures to enhance the landscape.

Potential Development of Sea Cucumber Farming in Tablolong Beach, Kupang, East Nusa Tenggara

Tablolong Beach, Kupang, West Nusa Tenggara, has significant potential for sea cucumber aquaculture development. This study examines the environmental conditions, climatic factors, and local natural resources that support sea cucumber farming in this area. The results showed that Tablolong Beach has very suitable environmental characteristics for sea cucumber growth, including suitable water temperature and sufficient natural food availability. In addition, the local community has strong traditional knowledge on sea cucumber collection and cultivation. the purpose of this study was to determine the potential and types of sea cucumbers found around Tablolong beach. This research method is an experimental method where samples are taken by diving in the waters of Tablolong beach. Sea cucumber species found consisted of H. atra, H. leucospilota, H. fuscocinerea, and S. monoturbeculatus. This research provides an important basis for designing a sustainable sea cucumber aquaculture development plan in Tablolong Beach, integrating ecological, economic, and social aspects. By utilizing the natural potential and local knowledge, the development of sea cucumber aquaculture in this area can become a model for sustainable utilization of marine resources and support the livelihoods of coastal communities

Food availability and population parameters for squirrels differ even in neighbouring urban parks

Some species occur in higher densities in cities than in natural habitats, despite the variety of urban stressors. Urban fragments can be extremely heterogeneous though, and species’ responses might vary between urban patches. However, only few studies examine mammalian populations from different fragments in the core of cities, where stressors are at their maximum. The Eurasian red squirrel (Sciurus vulgaris) is highly abundant in urban green spaces and readily makes use of supplemental food sources. We examined natural and supplemental food sources as well as squirrel populations in three small parks in an urban core. We found pronounced differences in natural and supplemental food availability between the parks. Squirrel population densities were generally higher at all three urban sites when compared to a geographically close located natural forest, but with variation between the parks. The squirrel density in the smallest park in the summer season was 42 times higher (index of minimum number alive: 8.8 individuals/ha) than in the forest, whereas it was only 20 or respectively 16 times higher in the two other parks. Individuals from the park with the highest population density had access to the highest amount of supplemental food sources. However, side effects from non-natural food items, e.g., related to nutrition, also need to be taken into consideration and might counteract the advantages of supplemental food sources. This study shows that urban effects can vary even at the smallest scale between nearby urban habitat patches and this needs to be considered when drawing conclusions about the effects of urbanisation and deciding about conservation actions.

Traditional polyculture as a mangrove restoration solution in Delta Mahakam, East Kalimantan Indonesia

The Mahakam Delta is a large mangrove ecosystem in East Kalimantan with a precious ecosystem and a massive mangrove species. Because of the conversion to shrimp aquaculture, the mangrove ecosystem has been devastated. This study looks at shrimp pond management in Salo Palai, Muara Badak, Kutai Kartanegara, East Kalimantan, using the traditional polyculture concept to increase pond productivity. The current shrimp pond condition was decreased water quality, substrate infertility, and natural food availability crisis. This model focused on traditional management, with a particular emphasis on pond preparation, polyculture, and used plant extracts. For 100 days, Penaeus monodon, Chanos chanos, Litopenaeus vannamei, Lates calcarifer, Scylla spp., and Gracilaria verrucosa were grown in the same time and pond. The yield from the pond was thrived: 332.14 kg/Ha. This concept can be used to restore mangroves, preserve the mangrove ecosystem, increase shrimp pond production, and protect the sea ecosystem; thus, this method achieves sustainable aquaculture.

Role of Natural Food in Enhancing the Productivity of Saline Nile Tilapia in the Mangrove Ecosystem of Segara Anakan Lagoon, Brackish Water Culture

Saline Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758) and Milkfish, Chanos chanos (Forskal, 1775) polyculture systems in brackish water culture require natural food to sustain their brackish water fish production. Brackish water culture of Saline Nile Tilapia is developed to improve the productivity of abandoned shrimp or crab pond. At present, there are no studies examining the potential of natural food to improve the productivity of these polyculture systems in the brackish water pond located in Tritih Kulon Village, Cilacap, Central Java. To assess the availability of this food source, the diversity and abundance of plankton in the water body were evaluated through analysis. Therefore, this study aimed to analyze plankton diversity in the water body and the relationship between plankton abundance as a natural feed and saline Nile Tilapia productivity in the brackish water polyculture. Phytoplankton and zooplankton were identified according the plankton characteristic available in the references. The results showed that 21 planktons, comprising 12 phytoplankton species and 9 zooplankton groups, were identified. In spite of low plankton diversity, however, this study proved that the plankton abundance positively supported Saline Nile tilapia productivity in the polyculture system with milkfish, as indicated by low mortality (17,5 ±8,59 %; R2= 0.825-0.908), absolute high weight gain (208.2 ± 22,5 gr; R2= 0.881-0.874), and high specific growth (2,28 ± 0.77 % day-1; R2= 0.87-0.91). The productivity of Saline Nile Tilapia in brackish water polyculture with milkfish is supported by the availability of natural food, with 5.95 to 18.50% of their gut content obtained from plankton.

VEGETASI TAMAN URBAN SEBAGAI PENYEDIA PAKAN BAGI BEBERAPA TROPHIC GUILD BURUNG HERBIVORA: STUDI TAMAN LAPANGAN BANTENG, JAKARTA PUSAT

Vegetal food is the most important resource for herbivores. The study of food consumed by bird community in Indonesia, especially in urban environments is needed to provide an overview of the ability of City Parks to support bird communities. The aim was to determine the urban park vegetation in the Lapangan Banteng park as a potential food source for urban birds, especially frugivores, nectarivores and granivores. The study was conducted in September until December 2018 . Data were analyzed using Rstudio and ImageJ. The results showed that there were 7 species of birds consisting: four species of granivores (Passer montanus, Streptopelia chinensis, Lonchura punctulata, and Pycnonotus aurigaster) and three species of frugivores (Psittacula alexandri, Dicaeum trochileum, Treron vernans) which were observed to use plants as food resource Lapangan Banteng park. Birds used 30% of trees (Syzygium polyanthum, Melaleuca leucadendra, Ficus benjamina) and 70% of herbaceous ground cover (Arachis pintoi., Phoenix sp., Pennisetum purpureum, Axonopus compressus, Cynodon dactylon, Cyperus rotundus, and Eleusine indica). The availability of sufficient natural food in nature will have an impact on both bird conservation and the environment. The availability of natural food will improve bird conservation and ensure the sustainability of urban biodiversity.

Experimental test of the efficacy of hunting for controlling human–wildlife conflict

AbstractHuman–wildlife conflict can cause major declines in wildlife populations and pose a threat to human safety and livelihoods. Large carnivores are among the most conflict‐prone species because they range widely, eat human‐associated foods, and can pose a risk to human safety. Legal harvest of carnivores by licensed hunters is an attractive method to attempt to reduce conflict; however, there is mixed evidence for its effectiveness. We leveraged a unique management project in Ontario, Canada in which a new spring American black bear (Ursus americanus) hunting season was implemented in selected wildlife management units in addition to the existing fall season. We examined human–bear interactions and incidents before (2012 and 2013) and after (2014 and 2015) this implementation in treatment and control areas. Further, using data from 2004–2019, we examined the longer‐term patterns of human–bear interactions and incidents before and after this management project when a spring season was implemented throughout the entire province beginning in 2016. Harvest increased significantly upon the implementation of the spring season in selected units, but there was no concomitant reduction in interactions or incidents, and these were higher in areas with the new spring season relative to control areas. Human–bear interactions, incidents, and harvest were strongly related to the availability of natural foods in all analyses. Regulated, presumably sustainable harvest was ineffective at reducing human–bear interactions and incidents in the near‐term and might have increased both. Our results support a long history of research showing that natural food availability is a primary driver of human–wildlife conflict. Programs promoting coexistence between people and wildlife, including education, capacity building, and management of unnatural food sources are likely to be the most successful at reducing conflicts between people and bears.

Dietary Diversity of Sumatran Elephants (Elephas Maximus Sumatrensis) At Elephant Training Center Way Kambas National Park

The Sumatran elephant (Elephas maximus sumatrensis) is a rare animal that is threatened with extinction, so conservation is needed. Elephant Training Center (PLG) Way Kambas National Park is one form of in situ conservation. The availability of natural food is one of the factors that determine the success of conservation. The purpose of this study was to determine the composition and diversity of forest community species as elephant feeding habitats, and to determine the types of plants that elephants eat. Purposive sampling was used to collect data using nested plots, 1 x 1 m2 for seedlings and undergrowth, 5 x 5 m2 for saplings, 10 x 10 m2 for poles and 20 x 20 m2 for trees. The results showed that the vegetation making up the forest as a grazing habitat for Sumatran elephants consisted of 27 species belonging to 19 families. The vegetation that elephants eat is Symplocos thwaitesii, Imperata cylindrica, Colopogonium sp., Bridelia monoica, Vitex pinnata, Shorea sp., Pennisetum purpureum, Gluta renghas, Mimosa pudica, and Melastoma. The most widely available plant species belong to the Poaceae and Leguminoceae families. The diversity index of the seedling level of 2.49 was categorized as high, while the vegetation level of sapling, poles, and trees was categorized as low. Meanwhile, the evenness index at the seedling, sapling, pole and tree levels was categorized as high. The richness index for all levels of growth is categorized as moderate.

High population prevalence of neonicotinoids in sharp-tailed grouse and greater prairie-chickens across an agricultural gradient during spring and fall

Neonicotinoids have been detected in many species of wild birds; however, few studies have quantified population-level exposure. We examined population-level exposure to 7 neonicotinoids in 2 species that use agricultural areas, sharp-tailed grouse (Tympanuchus phasianellus) and greater prairie-chickens (T. cupido). We sampled fecal pellets at leks in spring and collected livers from hunter-harvested birds in fall along an agricultural gradient throughout their respective ranges in Minnesota, USA. Most sharp-tailed grouse (93 %) and prairie-chicken (80 %) fecal pellets and livers (90 % and 76 %, respectively) had detectable concentrations of ≥1 neonicotinoid, with imidacloprid (IMI) and clothianidin (CLO) most commonly detected. Spring detections of IMI in both species increased with the proportion of a 2-km buffer in cultivation surrounding sampling locations and varied by year. A similar relationship with cultivation was not supported for CLO, which may reflect differences in the availability of seed types treated with IMI and CLO on the soil surface after planting. However, we also detected IMI and CLO from birds sampled in areas of low cultivation. Sharp-tailed grouse and prairie-chickens may select crop fields preferentially to forage, and thus have a higher risk of exposure than would be expected based only on the amount of cultivation. Year was important in models of IMI and CLO in both species and seasons, which likely reflects differences in planting and in the availability of natural foods among years. In contrast, the proportion of surrounding area in cultivation was not supported in models of fall neonicotinoid detections. Fewer crops are planted in the fall in Minnesota and grouse may be exposed through routes other than treated seeds. High detections, even in areas with little cultivation and during seasons with little planting, likely reflect prairie grouse selection of cultivated fields for food, but may also indicate that exposure risk extends beyond sites of application.

The spatial and temporal exploitation of anthropogenic food sources by common ravens (Corvus corax) in the Alps

BackgroundAnthropogenic food sources (AFSs) are widespread in human-transformed landscapes and the current scale at which they occur drives ecological change at the individual, population, and community levels. AFSs are exploited extensively by common ravens, Corvus corax. Understanding how raven populations use AFSs can provide insight into their ecological responses to AFSs.MethodsWe equipped 81 ravens in the Austrian Alps with GPS-transmitters over a period of 2.75 years. Using these tracking data, we investigated how cohort differences (i.e., age, sex, and origin) and seasonal changes influence raven movement patterns (i.e., occurrence distribution and maximum daily displacement) and AFS-use (i.e., number of AFSs visited and probability of being present at any AFS) at 45 extensively exploited sites.ResultsWe found that proxies for experience and dominance, inferred by age (i.e., juvenile versus adult) and origin (i.e., wild-caught versus captive-bred-released) cohorts, influenced movement patterns and the number of AFSs visited. However, all individuals were equally likely to be present at AFSs, highlighting the importance of AFSs for non-breeders in the study population. Seasonal changes in environmental conditions that affect energetic demands, the availability of natural and anthropogenic food, and foraging competition, influenced individuals’ occurrence distributions and AFS-use. We found that under harsher conditions in autumn and winter, individuals ranged wider and depended on AFSs to a larger degree. However, contrary to expectation, they were less likely to be present at AFSs in these seasons compared to spring and summer, suggesting a trade-off between time spent moving and exploiting resources. We attribute the small ranging movements exhibited by non-breeders in spring and summer to the presence of highly territorial and socially dominant breeders. As breeders mostly stay and forage within their territories during these seasons, competition at AFSs decrease, thereby increasing the likelihood of individuals being present at any AFS.ConclusionsWe emphasize that movement and AFS-use differ according to cohort differences and the seasonality of the environment. Our results highlight that predictable AFSs affect foraging strategies among non-breeding ravens. The extent of AFS-exploitation among non-breeding ravens in our study emphasize the potential of AFSs in shaping raven movement and resource-use.

Pharmaceutical contamination and biotic factors affecting parasitism in common carp ( Cyprinus carpio )

Increasing levels of persistent pollutants in the aquatic environment are likely to have serious impacts on host–parasite relationships. In this study, common carp (Cyprinus carpio) of the same age, origin and source were randomly stocked in two pond localities, one fed by treated water from a municipal sewage treatment plant and the other fed by a non-polluted stream. Fish biometric parameters and health status were evaluated after 2 years of exposure through the determination of somatic condition indices, parasite load and concentration of pharmaceuticals. Municipal pollutants were found at both sites, although at significantly higher levels at the polluted site, with antidepressants, antibiotics, analgesics and beta-blockers dominant in each case. Owing to a higher availability of natural food, carp from the polluted locality displayed significantly better body condition than those from the control site, while parasite abundance and species richness were higher at the control site. Our results suggest that, compared with fish from control locality exhibiting diverse and abundant natural parasite fauna, fish from the polluted locality were better able to cope with parasites, due to their better condition status. Fish from this study site may have profited from municipal waste water by avoidance of high levels of parasite infections.

Effects of supplemental feeding on nesting success and physiological metrics in eastern bluebirds Sialia sialis

Supplemental feeding is a common anthropogenic influence on wildlife which, dependent on natural food availability, can have positive or negative effects on physiological condition. For example, animals may respond negatively to supplemental feeding if the artificial food source increases disease exposure or there may be negative consequences from removal of a supplemental food source. We manipulated supplemental food availability in a wild population of eastern bluebirds Sialia sialis to examine the influence on body mass, physiological metrics and nesting success. Adult and nestling bluebirds were randomly assigned to one of three feeding groups. The first treatment group received mealworm Tenebrio molitor larvae inside nest boxes throughout the breeding attempt, the second treatment group received mealworms from nest completion until nestlings hatched, and the third treatment group received no supplementation. We collected blood samples from adults and nestlings to quantify bacterial killing ability, corticosterone levels and heterophil to lymphocyte ratios. As measures of nesting success, we quantified hatching success and fledging success. Supplement group tended to impact nestling mass near fledging; however, neither the physiological metrics nor the nesting success metrics differed significantly among experimental groups. Our results suggest eastern bluebird supplementation is largely neutral with the exception of its removal at the time of hatching, at least when natural food sources are abundant. Bird feeding by hobbyists may attract birds to locations with available nesting sites without demonstrably negative or positive effects, unless practiced inconsistently during breeding.