Effects of coypu (Myocastor coypus) abundances and diet selection on a wetland of the Patagonian steppe

We assessed diet selection, impact on vegetation, and explored habitat relationships with marsh birds of coypus (Myocastor coypus) in a steppe lagoon in Argentinean Patagonia. In two consecutive springs, abundance and spatial use of the coypus and nesting marsh birds were estimated by direct counts. The coypu was a selective consumer with seasonal variations in food items, and Myriophyllum sp. and Schoenoplectus californicus dominated its diet. Coypus and marsh birds showed a differential spatial use when rushes cover was high. However, when rushes cover decreased by coypu browsing, there was a similar use of space, and marsh birds were displaced to nest on the open water and other poorly protected areas of the rushes. Our results suggest that high abundances of coypu can have a detrimental effect on wetland ecosystems. Systematic monitoring and evaluation of their effects on wetlands in recently colonized areas is recommended.     

Feral horse impacts on threatened plants and animals in sub‐alpine and montane environments in Victoria,Australia

Feral herbivores are a major driver of biodiversity loss globally and can alter the structure, composition and functioning of ecosystems. The direct impacts of feral herbivores on plant communities are well studied, but the direct and indirect effect they have on wildlife is not well understood. In Victoria (south‐eastern Australia), a large feral Horse (Equus caballus) population coincides with highly sensitive and nationally endangered Alpine Sphagnum Bogs and Associated Fens communities, and several threatened animal species. We assessed the impact of feral horses on this ecological community and the Alpine Water Skink (Eulamprus kosciuskoi) and the Broad‐toothed Rat (Mastacomys fuscus) at 20 sites with varying levels of horse disturbance. We used scat counts to determine an index of feral horse abundance and quantified impacts associated with their presence in the landscape. Active searches were used for Alpine Water Skink and scat and runway surveys for Broad‐toothed Rat. We also measured the vegetation structure and the abundance of different vegetation types (life forms). Our results suggest that feral horses are associated with vegetation types and characteristics that negatively influence the presence or abundance of Alpine Water Skink and Broad‐toothed Rat. Sites with high horse activity had more low‐growing forbs, and the abundance of Alpine Water Skink was negatively related to this vegetation type. Grasses, sedges, rushes and shrubs were also less dense and lower in height in high horse activity sites, and Broad‐toothed Rat was less likely to be present in areas with these habitat attributes. We recommend that feral horses are controlled to protect these threatened vertebrate species and their Sphagnum bog habitat.     

Acquired Recognition of Chemical Stimuli from Pike,Esox lucius,by Brook Sticklebacks,Culaea inconstans (Osteichthyes,Gasterosteidae)

In this study we test whether brook sticklebacks (Culaea inconstans) can acquire predator recognition through releaser-induced recognition learning, i.e. simultaneous exposure to aversive ('releasing') stimuli and neutral stimuli causing learned aversion to the neutral stimuli. We exposed wild-caught pike-naive brook sticklebacks (collected from a creek containing fathead minnows, Pimephales promelas, but not pike, Esox lucius) to chemical stimuli from pike that were mixed with brook stickleback skin extract, fathead minnow skin extract, or a control of distilled water. In subsequent tests 2 d later, when only pike stimuli were presented, sticklebacks conditioned with stickleback skin extract and fathead minnow skin extract exhibited antipredator behaviour (i.e. increased schooling and movement toward the substrate), while those conditioned with distilled water did not. Sticklebacks conditioned with stickleback skin extract responded to pike with a more intense response, in terms of movement toward the substrate, than those conditioned with fathead minnow skin extract, suggesting that conspecific skin extract may be a stronger stimulus than heterospecific skin extract for learning recognition of predators. To our knowledge this is the first study to demonstrate that an acanthopterygian fish can acquire predator recognition through the pairing of conspecific alarm pheromone with the cue of a predator. Furthermore, our results are the first to demonstrate that fish can acquire predator recognition through the pairing of a heterospecific alarm pheromone with the cue of a predator. These results suggest that brook sticklebacks will benefit by being in close proximity to fathead minnows. Acquired predator recognition has long-term consequences in mediating predator-prey interactions.     

Effects of diet and temperature on condition, proximate composition and three major macro elements, Ca, P and Mg, in barbel Barbus barbus juveniles

Six feeding groups of 60 early juveniles (0.6?g) of a rheophilic cyprinid barbel Barbus barbus were reared in triplicate in 18?glass aquaria. Fish fed a commercial formulated dry diet Aller Futura were compared with those on natural food??commercially available frozen Chironomidae larvae at 17, 21 and 25°C. Daily food rations were adjusted according to fish biomass, differences in hydration between the two diets, and rearing temperature. No mortality occurred during experiment. Temperature, and especially diet, both affected whole body proximate and mineral composition of B. barbus juveniles. Under conditions of this experiment the formulated diet Aller Futura seems to satisfy the demands for calcium and magnesium, while an elevated lipid content in this diet was found and marginally deficient phosphorus content can be concluded. These resulted in a depressed content of phosphorus and total minerals in the body, and in elevated lipid content and condition coefficient in the Futura-fed fish, but no visible body deformities occurred. Advantages and limitations of the condition coefficient K were discussed. This is a non-destructive, express indicator that can be used as a supplementary tool for estimation of changes in body proximate composition in fish juveniles of similar size within a population.     

Strong spatial segregation between wildcats and domestic cats may explain low hybridization rates on the Iberian Peninsula

The European wildcat (Felis silvestris silvestris) is an endangered felid impacted by genetic introgression with the domestic cat (Felis silvestris catus). The problem of hybridization has had different effects in different areas. In non-Mediterranean regions pure forms of wildcats became almost extinct, while in Mediterranean regions genetic introgression is a rare phenomenon. The study of the potential factors that prevent the gene flow in areas of lower hybridization may be key to wildcat conservation. We studied the population size and spatial segregation of wildcats and domestic cats in a typical Mediterranean area of ancient sympatry, where no evidence of hybridization had been detected by genetic studies. Camera trapping of wild-living cats and walking surveys of stray cats in villages were used for capture–recapture estimations of abundance and spatial segregation. Results showed (i) a low density of wildcats and no apparent presence of putative hybrids; (ii) a very low abundance of feral cats in spite of the widespread and large population sources of domestic cats inhabiting villages; (iii) strong spatial segregation between wildcats and domestic/feral cats; and (iv) no relationship between the size of the potential population sources and the abundance of feral cats. Hence, domestic cats were limited in their ability to become integrated into the local habitat of wildcats. Ecological barriers (habitat preferences, food limitations, intra-specific and intra-guild competition, predation) may explain the severe divergences of hybridization impact observed at a biogeographic level. This has a direct effect on key conservation strategies for wildcats (i.e., control of domestic cats).     

A modular assessment tool for managing introduced fishes according to risks of species and their populations,and impacts of management actions

A modular assessment scheme for assisting the risk management of introduced fishes is described, with its recent application to England and Wales demonstrated. The initial module prioritises the introduced fishes in the risk assessment area according to their potential invasiveness and current distribution. The second module then assesses populations of the prioritised species in relation to the character of their receiving waters and the potential risks posed by their population in that circumstance; the output is a suggested management action for each population. The third module evaluates the suggested management action in relation to its potential impacts in the environment and how these impacts may be mitigated. The final module assesses the estimated cumulative cost of the selected management action relative to an alternative action. To demonstrate its potential value for managing extant populations of introduced fish, three eradication case-studies from England were assessed retrospectively using the scheme. This revealed eradication of two topmouth gudgeon Pseudorasbora parva populations was commensurate with their levels of ecological risk in the environment. By contrast, initial assessment of the eradication of a feral population of fathead minnow Pimephales promelas suggested control and containment was the commensurate management action due to a relatively low risk of natural dispersal. Application of the scheme elsewhere in the world and to other faunal groups should enable more objective decision-making in management programmes and enhance conservation outcomes.     

Biology of the minnow Phoxinus phoxinus and its interactions with brown trout Salmo trutta in Øvre Heimdalsvatn, Norway

Minnows have recently been introduced into the mountain lakes of southern Norway. In Øvre Heimdalsvatn, an intensively studied lake, the minnow population has increased rapidly during the last decade. Studies were performed on feeding habits, habitat preferences, age, growth, energy content, densities, parasites, predation and spawning activities. Several aspects were found to be different from other studies, e.g. higher age of sexual maturation, lower growth rate, no feeding on plants, and low infection of parasites. The interaction with the only other fish, the brown trout, is discussed in relation to the minnow population. In 1978 the minnows constituted little more than 10% of production and food consumption of the trout population, and only limited food competition and predation was documented. Increasing competition is likely with a greater minnow population.     

Dry Season Diet of the Sloth Bear (Melursus ursinus) in Hadagarh Wildlife Sanctuary,Eastern India

Dry season food habit of sloth bear (Melursus ursinus) in Hadagarh Wildlife Sanctuary was characterized by scat analysis. Importance value index (IVI) of contribution of different food items in the diet of sloth bear was estimated from the undigested food remnants. Percentage of dry weight and IVI score of Ziziphus fruits was highest, termites were the most frequently occurring food item in the diet and percentage of frequency occurrence was equal for both fruits and insects. The present study, as compared to previous studies, suggests that the dietary preference of sloth bear varies according to availability of food and the habitat quality.     

Comparative analysis of the diet of feral and house cats and wildcat in Europe

Differences in availability of food resources are often manifested in the differentiation of feeding habits of closely related mammal species. Therefore, we assumed that the diet composition and trophic niche of house (i.e., highly dependent on human households), feral (i.e. independent on human households) domestic cats (Felis silvestris catus) and wildcats (Felis s. silvestris) differs. Based on the literature data from Europe (53 study sites), we compared the diet of these three felids analyzed with use of indirect methods (stomach and scat analyses). In the case of the house cat, we additionally compared consumption data obtained directly from prey brought home. Data were expressed as the relative frequency of occurrence to compare dietary patterns. The main prey of the three cat types were small mammals in different ratios. According to the stomach and scat samples, the diet composition of the cat types showed differences in the consumption of rodents, insectivores, wild ungulates, and household food, supporting the “dietary differences originate from varying resources” hypothesis. More opportunistic house cats had a broader trophic niche than feeding specialist wildcats, while feral cats had an intermediate position. The trophic niche breadth of all three cat types increased along a latitudinal gradient from northern to southern areas of Europe. The predation of the house cat which was examined from prey brought home differed from the data obtained by indirect diet analysis; however, it yielded similar results to the diet of the feral cat and the wildcat. Due to their high numbers and similarity of its diet to the wildcat, house cats are a threat to wild animals; therefore, their predation pressure needs to be further investigated.     

Explaining Spatial Heterogeneity in Population Dynamics and Genetics from Spatial Variation in Resources for a Large Herbivore

Fine-scale spatial variation in genetic relatedness and inbreeding occur across continuous distributions of several populations of vertebrates; however, the basis of observed variation is often left untested. Here we test the hypothesis that prior observations of spatial patterns in genetics for an island population of feral horses (Sable Island, Canada) were the result of spatial variation in population dynamics, itself based in spatial heterogeneity in underlying habitat quality. In order to assess how genetic and population structuring related to habitat, we used hierarchical cluster analysis of water sources and an indicator analysis of the availability of important forage species to identify a longitudinal gradient in habitat quality along the length of Sable Island. We quantify a west-east gradient in access to fresh water and availability of two important food species to horses: sandwort, Honckenya peploides, and beach pea, Lathyrus japonicas. Accordingly, the population clusters into three groups that occupy different island segments (west, central, and east) that vary markedly in their local dynamics. Density, body condition, and survival and reproduction of adult females were highest in the west, followed by central and east areas. These results mirror a previous analysis of genetics, which showed that inbreeding levels are highest in the west (with outbreeding in the east), and that there are significant differences in fixation indices among groups of horses along the length of Sable Island. Our results suggest that inbreeding depression is not an important limiting factor to the horse population. We conclude that where habitat gradients exist, we can anticipate fine-scale heterogeneity in population dynamics and hence genetics.     

Predicting the Effects of Endocrine Disrupting Chemicals on Fish Populations

This study evaluates the applicability and sensitivity of fish population dynamics modeling in assessing the potential effects of individual chemicals on population sustainability and recovery. Fish reproductive health is an increasingly important issue for ecological risk assessment following international concern over endocrine disruption. Life-history data from natural brook trout and fathead minnow populations were combined with effects data from laboratory-based studies, mainly concerning species other than brook trout and fathead minnows, to assess the likely impact of nonylphenol (NP) and methoxychlor (MXC) on brook trout (Salvelinus fontinalis) and fathead minnow (Pimephales promelas) population size. A delay differential equation (DDE) model with a 1-day timestep was used to predict the population dynamics of the brook trout and fathead minnows. The model predicts that NP, could enhance populations by up to 17% at a concentration of 30?µg l^?1 based on the results of reduction in survival and increased fecundity from life-cycle toxicity tests, however attempting to allow for growth reduction and its effect on fecundity results in a prediction of a 28% reduction in population numbers. For fathead minnows the DDE model predicts that the same concentration of NP could cause a population reduction of 21%. The differences in these predictions are related to these two species having different life history strategies, which are considered in the parameterization of the model. Post-application concentrations of MXC may peak around 300?µg l^?1 and then decline rapidly with time. Predictions show that such applications could cause a reduction of up to 30% in brook trout populations if the application occurs at the peak of the spawning season on successive years but that the effect would be less than 1% if the spawning season is avoided. Effects on the fathead minnow population size are predicted to be smaller (<4%) even if application occurs during the spawning period. Risk based statistics generated by the population dynamics models, such as interval decline risk or quasiextinction risk and predicted time to recovery complement traditional effects parameters such as LC50 and LOEC and may ultimately prove to be more useful in risk assessment.     

Effects of Fathead Minnow Colonization and Removal on a Prairie Wetland Ecosystem

Fish communities in prairie wetlands are extremely dynamic. Due to complete winterkills and periodic colonization, individual basins alternate between supporting a fish population and being fishless. Here we assess the ecological consequences of colonization and subsequent extinction of a fathead minnow population in a prairie wetland. We used a BACI-type approach (before-after control impact) in which data from the colonized wetland were paired with data from a similar fishless site first when both wetlands were fishless (1996), then when the minnow population reached moderate densities in the colonized site (1998), and then again when the colonized site became fishless after treatment with rotenone (1999). Fish colonization resulted in significant increases in turbidity, total phosphorus, and chlorophyll a in the water column; it also caused significant decreases in the abundance of aquatic insects and large cladocerans. Elimination of the minnow population largely reversed the effects of minnow colonization. Our results indicate that characteristics of prairie wetlands can vary as they alternate between supporting fathead minnow populations and being fishless and that ecological characteristics may change rapidly in response to minnow colonization or elimination. Received 18 July 2000; Accepted 17 January 2001.     

Rural avenues as a refuge for feral honey bee population

Several honey bee (Apis mellifera) subspecies are in danger of local extinction because their feral population have almost completely disappeared. An important threat to the feral populations of bees is loss of habitat and loss of woodlands. In many places the only habitat suitable for honey bee nesting are rows of trees along roadsides. We studied a feral population of honey bees inhabiting avenues in northern Poland. We inspected 142 km of avenues and found 45 feral colonies. The estimated density of feral population inhabiting the avenues was 0.10 nest km^?2. Honey bees preferred to build their nests in trees with a thick trunk and a somewhat weak state of health. There was no strong preference of bees to any species of trees. We stress the importance of protection of existing avenues and creating new ones. This can provide suitable habitat not only for honey bees but also for other endangered species.     

A rapid, direct assay to measure degranulation of primary granules in neutrophils from kidney of fathead minnow (Pimephales promelas Rafinesque, 1820)

A direct, rapid, quantitative colorimetric assay to determine neutrophil primary granule degranulation was adapted for use with fathead minnow kidney neutrophils. The assay measures the exocytosis of myeloperoxidase (MPO) using 3,3',5,5'-tetramethylbenzidine as a substrate. The assay was validated by comparing the total myeloperoxidase content of neutrophil populations obtained from adult cattle, as a known positive, and fish; evaluating the effects of calcium ionophore (CaI), phorbol myristate acetate (PMA), aqueous solution of beta-glucan (MGAQ) and zymosan (Z) with and without cytochalasin B (cyto B) as stimulants of degranulation; determining the kinetics of primary granule exocytosis and detecting changes in degranulation when fish were exposed to stress and anaesthesia with MS-222. The MPO assay detected MPO activity in fathead minnow neutrophils that correlated to neutrophil numbers, confirmed that degranulation was increased when CaI was used compared to other stimulants, determined degranulation peak at 60 min and confirmed decreased degranulation after exposure to handling and crowding stress, with and without MS-222. Therefore, the MPO assay is capable of detecting important differences that may occur in degranulation of fathead minnow kidney neutrophil primary granules and in total neutrophil myeloperoxidase content.     

Niche separation of sympatric macaques, Macaca assamensis and M. mulatta, in limestone habitats of Nonggang, China

Comparative studies of sympatric species are essential in understanding those species’ behavioral and ecological adaptations as well as the mechanisms that can reduce resource competition enough to allow coexistence. We collected data on diet, activity budget and habitat use from two sympatric macaque species, the Assamese macaque (Macaca assamensis) and the rhesus macaque (M. mulatta), in a limestone seasonal rainforest of Nonggang Nature Reserve, southwestern Guangxi, China. Our results show that the two sympatric macaques differ in diet, activity budget, and habitat use: (1) out of the 131 plant species that were used by both macaque species as food over the year, only 15 plant species (11 %) were shared. Rhesus macaques used more plant species as major foods, and had higher dietary diversity and evenness indexes than Assamese macaques. (2) Assamese macaques fed predominantly on leaves, whereas rhesus macaques fed more selectively on fruits. The rhesus macaques’ diet varied according to season, and was significantly correlated to season fluctuation in fruit availability. (3) Assamese macaques devoted more time to resting, and less time to feeding than rhesus macaques (4) Assamese macaques were present mostly on the cliff, and tended to stay on the ground, whereas rhesus macaques were present mostly on the hillside, and showed preference to lower and middle canopy. The observed differences in diet and habitat use between the two macaque species represent behavioral patterns enabling their coexistence.     

Diet Shift and Its Impact on Foraging Behavior of Siberian Crane (Grus Leucogeranus) in Poyang Lake

The study of habitat selection and diet has a long history in ecology. This is often used to assess the functional roles of wetland in biodiversity conservation. Shifting habitat and diet may be one of the survival strategies during extremely adverse conditions. Therefore, sudden changes in habitat selection may indicate the deterioration of the habitat quality, and management interventions are necessary. Siberian crane (Grus leucogeranus) became critically endangered due to loss of habitat, and is currently a global conservation focus. Every winter, more than 95% of the species'' global population congregates at Poyang Lake, and feeds on tubers of Vallisneria spiralis in shallow water and mudflat habitat. In this study, we reported the first sighting of large numbers of Siberian cranes foraging at wet meadows, where they fed on a different plant, Potentilla limprichtii due to extreme scarcity of their preferred tuber. To understand how well the cranes adapted to such unusual habitat, field surveys to assess the distribution of cranes across different habitats, and food availability in each habitat were carried out in the winter of 2011. Field observations on crane behaviors at different habitats were also conducted. Results show that cranes displayed significantly different behavior patterns when using the wet meadow, compared to the crane''s optimal habitat - shallow water and mudflat. Both juveniles and adults spent significantly less time foraging, and more time alerting in meadows than in shallow waters and mudflats. These results indicated that the meadow might be a suboptimal wintering ground for Siberian crane, which helped the cranes survive from extreme unfavorable conditions. To some degree, this finding alleviates the general concern over the fluctuating of its food resources which was caused by hydrological disturbances. However, more studies are needed to assess the consequences of such diet and habitat shift for crane survival.     

Throwing the baby out with the bathwater: does laurel forest restoration remove a critical winter food supply for the critically endangered Azores bullfinch?

The invasive Clethra arborea has a dual-role in the diet of the Azores bullfinch, a critically endangered bird species endemic to the island of São Miguel (Azores, Portugal). This is a crucial winter food resource but it lowers the availability of native laurel forest species that compose most of the bird’s diet throughout the year. The removal of this and other invasive alien species is part of current laurel forest habitat restoration programmes, disregarding the impact on the Azores bullfinch population. In order to evaluate the first responses of the Azores bullfinch to habitat restoration, we studied bird diet, foraging behaviour, food availability and habitat occupancy in managed (without C. arborea) and control areas. Significant increases in the availability of native food resources in managed areas were noticeable in the diet, particularly the intake of Ilex perado ssp. azorica and Prunus lusitanica ssp. azorica flower buds. In most of the studied months birds heavily used and foraged in managed over control areas. The one exception was in December, when a resource-gap occurred in managed areas, which may be overcome in the short-term due to re-establishment of native plants following removal of invasive aliens.     

Fish assemblages across a vegetation gradient in a restoring tidal freshwater wetland: diets and potential for resource competition

Marsh habitats have been the focus of recent worldwide restoration efforts due to their degradation and destruction as a result of human development. We assessed fish resource use at a naturally restoring marsh (Liberty Island, California, USA) by comparing diet composition, stomach fullness, normalized stomach weight, and diet overlap across a vegetation gradient. Fish were collected using gill nets and fyke nets at six sites during spring 2010, summer 2011 and winter 2012. We analyzed 392 stomachs from the eleven most abundant species collected. Prey composition and biomass varied seasonally for all fish species, but there were no notable differences across sites or seasons for stomach fullness or normalized stomach weight for most fish species. Results from non-metric multidimensional scaling (NMDS) and two-way analysis of similarities (ANOSIM) indicated minimal diet overlap between species (R?=?0.633, p?=?0.001) and seasons (R?=?0.413, p?=?0.001). Seasonal habitat and resource use across the vegetation gradient was species-specific. Small but significant spatial diet differences were detected for inland silverside, striped bass and bigscale logperch. Delta smelt exhibited seasonal diet differences by shifting from chironomids and zooplankton during spring, to amphipods and zooplankton during winter. More generally, fish maintained stomach fullness across all sites and seasons while maintaining minimal dietary overlap. Our study emphasizes the importance of tidal marshes as feeding habitat for several fish species, including the endangered delta smelt.     

Live animal radiography to measure developmental instability in populations of small mammals after a natural disaster

Stress placed on individuals in a population from natural and anthropogenic disturbances can elevate developmental instability. We studied the result of a natural disaster when one-third of a forested nature preserve was destroyed by an F3 tornado. Populations of two abundant species of small mammals, Peromyscus maniculatus and P. leucopus, were monitored in both disturbed and undisturbed habitats. We used an X-ray technique to measure developmental instability as indicated by fluctuating asymmetry (FA) in cranial and skeletal features of live animals. FA in femur length was higher in disturbed habitat for P. leucopus but was higher in undisturbed habitat for P. maniculatus. This difference in developmental instability mirrors differences in habitat preference between these species: P. leucopus prefers forest habitat and P. maniculatus prefers open, herbaceous habitat. These results were not explained by either food availability or body condition, both of which were higher in the disturbed habitat suggesting higher quality for this habitat. Thus, the FA response may be related to other indicators of habitat quality, e.g., vertical stratification, coarse-woody debris, or population density, which may differ between undisturbed and disturbed habitats.     

Effects of Fish-farm Activity on the Limnetic Community Structure of Brown Trout, Salmo trutta, and Arctic Charr, Salvelinus alpinus

Establishment of four fish-farms during the period 1971 to 1994 in the oligotrophic lake Skogseidvatnet affected Arctic charr, Salvelinus alpinus, but not brown trout, Salmo trutta. From 1971 to 1987, an increase in mean individual size of Arctic charr was recorded, while the mean individual size of brown trout remained stable. Arctic charr were found to use deeper benthic areas than brown trout. Approximately 8% of the Arctic charr population (>26cm), were found to switch to waste food from fish-farms, resulting in a novel feeding habitat for the species. They were, however, found in gillnets distant from the fish farm cages, indicating high mobility. The habitat segregation between the two species can most likely be explained by selective differences and asymmetric competition with brown trout as the dominant species. Based on the present results, changes in the Arctic charr population may be due to increased food availability and due to a new habitat use as a waste food feeder. The reason for the brown trout population to have remained stable with respect to mean size, growth pattern and habitat use, may be due to a different diet choice than Arctic charr in this lake. Brown trout were found to feed mainly on terrestrial insects, while Arctic charr fed mainly on zooplankton and on waste food.