Electivity Index Research Articles

Ecological restoration amplifies riverine fish catch of Gudusia chapra (Hamilton, 1822): an impact study in the river Ganga using multivariate statistical tools and water quality indices.

Fish residing in the aquatic ecosystem are considered the best ecological indicator for monitoring environmental habitat. To evaluate the changes that occurred due to relative restoration in the ecological habitat, a study was conducted in the freshwater zone of the river Ganga between Buxar, Bihar, and Ballia, Uttar Pradesh, between July 2021 and July 2022. In the monitoring, the physico-chemical condition, as well as the food and feeding habits of the fish Gudusia chapra, were monitored with the help of various pollution evaluating indices, namely, the algal pollution index (API) for planktons, the comprehensive pollution index (CPI-WQI), and the National Sanitation Foundation Water Quality Indices (NSF-WQI) for water. The study showed that the relative restoration facilitated the amplification of the fish catch from 5.60 to 98.98% in two consecutive years. The reduction in the API (15 to 4) as well as CPI (0.80 to 0.72) during both years signified the reduction of the pollution status of the river in the region. The NSF-WQI also decreased from 88.27 to 79.27 from 2021 to 2022. The electivity index for the fish showed that fish preferred the groups Cyanobacteria, Rotifera, and Copepoda. The multivariate, as well as univariate analyses, revealed that the fish G. chapra is significantly influenced by multiple abiotic as well as biotic variables, among which the major contributors are riverine velocity, transparency, conductivity, pH, dissolved oxygen, total alkalinity, carbonate, bicarbonate, salinity, total hardness, calcium, silicate, and biochemical oxygen demand.

Enclosure design and welfare of plains zebras: Impact of enclosure design on behavior and space use of plains zebras under human care

ABSTRACT Plains zebras are commonly hosted in zoos, but few welfare-related studies are available in the literature. This research aimed to assess the effect of enclosure design on two groups of captive zebras housed at the Giardino Zoologico di Pistoia – GZP (Italy) and Parco Faunistico Valcorba – PFV (Italy) through the analysis of behavior and enclosure use. The groups consisted of an adult pair and a male juvenile at GZP and six adult females at PFV. We collected data in 2019 over 19 sampling days using the continuous focal animal sampling technique. We performed 12 observation sessions per day, with each session lasting 30 min. We analyzed the subjects’ behavioral time budget and enclosure use using Generalized Linear Mixed Models and the Electivity Index. The results showed that the time allocated to feeding behavior varied from 8–16% in the enclosure with gravel substrate (GZP) to 72–85% in the exhibit enriched with a pasture (PFV), with this last percentage resembling data reported for wild zebras. Results showed that institution was a significant predictor of feeding behavior, suggesting that the presence of a pasture can stimulate food-related behavioral patterns. Regarding enclosure use, the presence of hay and water troughs influenced the animals’ space use. Our findings also suggest that evaluating both behavior and enclosure use can provide a more comprehensive overview of the welfare state of the animals. However, future studies are needed to better investigate the influence of social factors on the behavior and enclosure usage of captive Plains zebras.

Predator-prey trait associations and feeding preferences of demersal fishes in the southern North Sea

In marine ecosystems under ongoing long-term changes, reducing complex food webs to their functionally important properties enables systematic analysis of bottom-up/top-down regulations and species turnover. The assessment of feeding interactions in the form of predator and prey trait associations provides a better understanding of predators’ criteria for prey selection and thus is a promising approach to reduce complexity. Here, we tested RLQ ordination and fourth-corner analysis, complementary multivariate approaches, as tools to identify ecologically relevant associations between the traits of 8 demersal fish species in the southern North Sea and their fish or benthic prey. To scrutinize the trait-based results in their appropriateness to reflect selective feeding behaviour of the predator species, we compared them with a taxon-based electivity index, Chesson’s α. Among 7 predator traits investigated, body tissue composition represented by omega-3 polyunsaturated fatty acid content was significantly associated with prey traits, being positively correlated with energy density of the prey and negatively with prey of low mobility. Comparisons with the electivity indices showed that the prey preferred by predators corresponded relatively well with the identified prey trait preferences. The results of the tested analysis approach support its use when assessing the mutual dependences of predator and prey populations on a functional level. Provided the data availability and quality of feeding-related traits is sufficiently high, trait-based predator-prey analysis with RLQ and fourth-corner analyses offers new possibilities for understanding food web dynamics in the context of climate-change-induced species distribution shifts.

Diet preference of black rhinoceros Diceros bicornis at Welgevonden Game Reserve, South Africa, across seasons

Diet preference of the black rhinoceros Diceros bicornis was determined in Welgevonden Game Reserve (WGR), located in the Waterberg region of Limpopo Province, South Africa. Fieldwork was conducted in the dry, early wet and late wet seasons. Diet preference was determined using microhistological faecal analysis and browse availability surveys. A chi-square goodness-of-fit test assessed similarity between the observed diet composition based on dung samples and the expected diet composition. To account for potential non-independence between browse availability and diet composition, a weighted approach was employed where browse availability was just one of several contributing factors to the expected composition. Plant species selectivity was quantified by Ivlev’s electivity index. Results obtained from this indicated that these black rhinos preferentially browsed certain plant species across different seasons. Plant species observations in the dung samples from the dry season totalled 3 984, with the evergreen Natal gum Euclea natalensis dominating the diet; for the early wet season, plant observations in the dung totalled 1 479, with buffalo thorn Ziziphus mucronata dominating in the diet; for the late wet season, plant observations in the dung totalled 4 424, with the small deciduous tree Ochna pulchra dominating in the diet. By obtaining information on food selection and the availability of browse species across seasons, this study provides a clearer understanding of black rhinos’ forage preference in WGR.

An Analysis of Cost-Effectiveness and Clinical Outcomes of a Comprehensive Aortic Service in a Tertiary Center over One Year

ObjectivesEndovascular aortic repair (EVAR) is an established and attractive alternative to open surgical repair (OSR) of abdominal aortic aneurysms (AAA) due to its superior short-term safety profile. However, opinions are divided regarding its long-term cost-effectiveness.We compared the total yearly cost of running endovascular and OSR services in a single tertiary centre, to determine whether fenestrated EVAR (FEVAR) represents a clinically efficacious, affordable treatment option. Design and MethodsA single centre retrospective review was performed on 109 patients undergoing a procedure related to index or previous abdominal aortic repair, with one year follow up. Data was collected from the National Vascular Registry and hospital records. The primary outcome was cost per QALY. Secondary outcomes included 30-day mortality and morbidity, re-intervention rates, length of hospital stay, aneurysm and all-cause mortality at one year for elective index procedures. ResultsThe average cost per patient of all FEVAR was £16,041.53 (+/-8,857.54), £13,893.51 (+/-£21,425.25) for standard EVAR, and £15,357.22 (+/-£15,904.49) for OSR (FEVAR vs EVAR p=.55, FEVAR vs OSR p=.83, OSR vs EVAR p=.76). Of the secondary outcomes, significant findings included increased length of stay and respiratory morbidity for patients undergoing open versus endovascular repair. There was no significant difference in 30-day or one-year mortality between groups. ConclusionFEVAR, EVAR and OSR all represent cost-effective options for aortic repair, with similar outcomes. Our data highlights the potential for FEVAR to present a viable alternative to open repair, particularly in higher risk groups, when performed in specialist centres.

FOOD PREFERENCES OF EARLY JUVENILE SCALLOPED SPINY LOBSTER IN EKAS BAY, LOMBOK, INDONESIA

Ekas Bay is the largest bay on the island of Lombok which is the location for catching and cultivating spiny lobsters. This research was conducted from May to July 2021 on the Scalloped spiny lobster (Panulirus homarus). This study aims to identify the types of natural foods consumed and determine the preferred types of food, as well as the early juvenile feeding time of Scalloped spiny lobster located in Ekas Bay, East Lombok Regency, West Nusa Tenggara Province (NTB). Puerulus samples were collected in the last week of May 2021, enlarged puerulus was performed in submerged cages measuring 15 cm × 15 cm × 15 cm, mesh size <3 mm, with a density of 4 puerulus/m2. The cages are placed at a location 70 m to the sea from the shoreline, at a depth of 0.5, 1.0, and 1.5 m. After reaching the juvenile phase, lobsters are collected during the new and full moon phases (06.00 am, 06.00 pm and 12.00 am, respectively) in June to July 2021. A total of 60 individual juvenile lobsters (algal phase) were analyzed for their stomach contents. The average percentage of the total Index of Relative Important (IRI) obtained for the identified taxa were bivalves (22.32%), copepods (23.64%), demosponges (24.98%), while digestibdle material was 29.06%. The electivity index data (Ei) shows that lobsters prefer bivalves over other taxa. Lobster samples taken in the morning had a stomach fullness rate of 50%, indicating active feeding at night.

Rare and Hungry: Feeding Ecology of the Golden Alpine Salamander, an Endangered Amphibian in the Alps.

Amphibians are considered critical species in the nutrient flow within and across ecosystems, and knowledge on their trophic ecology and niches is crucial for their conservation. For the first time we studied the trophic ecology of the rare and endemic Salamandra atra aurorae in a mixed temperate forest in northern Italy. We aimed to define the realized trophic niche, investigate the prey selectivity and explore possible levels of individual specialization. In summer 2022 we obtained stomach contents from 53 salamanders by stomach flushing and prey availability using pitfall traps. We used the Costello graphical method to analyse the realized trophic niche, and the relativized electivity index to study prey selectivity. Our results show that the Golden Alpine salamander adopts a generalist feeding strategy with positive selection of few prey categories (e.g., Myriapoda, Hymenoptera except Formicidae). Food preference seems to be driven by size, movement ability and chitinization of the prey. A high degree of inter-individual diet variation, modularity and clustering was found, describing a scenario that can be framed in a Distinct Preference model framework. This study gives new insights on the trophic ecology of the Alpine salamander complex, whose subspecies appear to adopt similar feeding strategies.

Effects of microplastic ingestion on feeding activity in a widespread fish on the southwestern Atlantic coast: Ramnogaster arcuata (Clupeidae)

The presence of microplastics (MPs) in the fish gastrointestinal tract has been documented in several studies. However, it is unclear whether this ingestion is active or passive and whether it affects feeding activity in natural environments. In this study, three sites with different anthropogenic pressure were selected from the Bahia Blanca estuary, Argentina, and the small zooplanktivorous pelagic fish Ramnogaster arcuata was used to evaluate MP ingestion and its effect on specie's trophic activity. We analyzed the zooplanktonic composition, levels, and types of MPs in both the environment and the stomach contents of R. arcuata. Moreover, we assessed the trophic behavior of R. arcuata to determine electivity, stomach fullness, and vacuity indexes. The results showed that despite the availability of prey in the environment, 100 % of the specimens ingested MPs, and their levels and characteristics were different according to the site. Stomach contents at sites related to harbor activities presented the lowest MPs concentrations, most of them were paint fragments, with the smallest sizes and a low diversity of colors. The highest MP ingestions were found near the principal sewage discharge, being mostly microfibers, followed by microbeads, and with a greater variety of colors. Electivity indices showed that R. arcuata has a passive or active ingestion according to the size and shape of MPs. In addition, the lowest stomach fullness index and the highest vacuity index values were associated with the highest level of MP ingestion near the sewage discharge. Altogether, these results demonstrate a negative effect of MPs in the feeding activity of R. arcuata and help to elucidate some mechanisms by which these particles are ingested by a bioindicator fish used in South America.

Camelthorn and blackthorn trees provide important resources for Southern Pied Babblers (Turdoides bicolor) in the Kalahari

In the southern Kalahari Desert, cooperatively breeding Southern Pied Babblers Turdoides bicolor frequently build their nests and forage in camelthorn trees Vachellia erioloba, a keystone species in the region, and blackthorn trees Senegalia mellifera, a widespread early successional shrub. Using Ivlev's electivity indices (Ei), we show that Southern Pied Babblers preferentially nest in camelthorn trees and preferentially forage in or under camelthorn and blackthorn trees. Southern Pied Babblers primarily forage on the ground; however, they will make use of arboreal resources when these are available. We observed the birds spending the highest proportion of foraging time off the ground during October, when breeding is also most common, compared with all other months within the austral summer breeding season. They are most likely to be observed foraging in camelthorn trees earlier in the breeding season and blackthorn trees later in the breeding season. We demonstrate that Southern Pied Babblers have a strong relationship with camelthorn trees, in which they prefer to both nest and forage. We highlight the importance of protecting camelthorn trees, a keystone species in the region, as part of the conservation and management of endemic Kalahari fauna such as the Southern Pied Babbler. In addition to contributing to the literature on keystone species, our observations raise questions about the ways in which avian reproduction in the arid zone could be decoupled from rainfall via the phenology of deep‐rooted tree species.

Foraging behavior of Raramuri Criollo vs. Angus cattle grazing California Chaparral and Colorado Plateau shrublands

Selecting livestock genetics adapted to arid environments, such as Criollo cattle, is one of several strategies recommended for decreasing the vulnerability to climate change of ranching in the southwestern USA. Our objective was to determine whether desirable foraging traits of Criollo cattle previously documented in the Chihuahuan Desert, held true in two of the most climate-vulnerable ecosystems of the Southwest. We conducted a study at Rancho Corta Madera (RCM) in southern California and Dugout Ranch (DR) in southeast Utah. Twenty mature cows, 10 Raramuri Criollo and 10 Red or Black Angus, were monitored with GPS collars during multiple seasons between 2018 and 2021. Geolocation data were used to compute daily distance traveled (km*d−1), movement velocity (m*min−1), path sinuosity (SI), time spent grazing, resting, or traveling (h*d−1), and area of the pasture explored (ha*d−1) as well as to calculate selection of vegetation cover types (E, Ivlev's Electivity Index) by cows of each breed. The effects of breed, season, year, and pasture on each of these metrics were modeled with repeated measures analyses of variance. At both ranches, statistically detectable differences (P ≤ 0.05) between breeds were observed for most behavior metrics during the dormant season. Conversely, few breed differences were observed during the growing season. Criollo cattle exhibited greater relative preference for a number of shrub dominated vegetation types at both ranches, and similar relative selection of grassland dominated sites compared to Angus counterparts. At both ranches, Criollo cattle exhibited similar or less relative preference for riparian areas vs. Angus counterparts. Breed divergence vs. convergence of foraging behaviors during the dormant vs. growing seasons, previously observed in the Chihuahuan Desert, was documented at both sites. Positive system outcomes associated with foraging traits of Criollo cattle could be expected to occur more broadly across the Southwest.

Wildlife habitat mapping using Sentinel-2 imagery of Mehao Wildlife Sanctuary, Arunachal Pradesh, India

Mehao Wildlife Sanctuary, situated in the state of Arunachal Pradesh, is part of an important biodiversity hotspot in the north-eastern part of India in the Himalayas. The current study deals with the identification of important wildlife habitats in the sanctuary. We used a supervised classification technique to delineate these habitats in the sanctuary, which are used by several mammals and bird species encountered during camera trap and sign surveys conducted between November 2017 and May 2020. Satellite images from Sentinel – 2A were used to classify the land use land cover (LULC) of the sanctuary. The LULC information was generated by using a maximum likelihood classifier. We classified a total of thirteen LULC classes, i.e., water, built-up, agriculture, orchard, grassland, bamboo forest, bamboo-mixed forest, riverbed, barren land, snow, wild banana, riverine forest and mixed forest. LULC classification reveals a high percentage of mixed forest, about 69.9%, followed by wild bananas at 7.2%. The commission and omission error rates, however, are high for riverbed and agriculture (0.5) and bamboo forest (0.5), respectively. The accuracy assessment showed an overall classification accuracy of 88.5% with a Kappa coefficient of 0.87. The abundance of mammals was high in the mixed forest, but Ivlev's electivity index shows that species generally avoided this habitat and preferred specialized forest habitats, such as bamboo forest, bamboo-mixed forest, grassland, riverbed and riverine forest. Our LULC map will provide a baseline for potential planning and monitoring changes of wildlife habitats in Mehao WLS.

Forage diversity and selection in white-tailed deer (Odocoileus virginianus Texanus MEARNS) in coahuila, mexico

Objective: To identify diet diversity and selection among white-tailed deer (Odocoileus virginianus texanus Mearns) at UMA Rancho San Juan, Monclova, Coahuila, Mexico, from October 2018 to August 2019. Design/methodology/approach: The composition of the white-tailed deer’s diet was identified by applying the microhistological technique. The line interception method was used to estimate the seasonal availability of forage. Diet and forage diversity were established based on the Shannon index, while their relation was identified using a simple linear regression. Diet selection was determined using the chi-squared test and Ivlev’s electivity index. Results: We identified 49 species and 20 families in the diet, which comprised 49.84% shrubs, 18.38% succulents, 16.02% herbaceous plants, and 15.72% grasses. Deer selected Opuntia engelmannii, consumed Acacia rigidula and Cenchrus ciliaris in proportion to their availability, and consumed Acacia berlandieri, Jatropha dioica, and Karwinskia humboldtiana below their availability. Study Limitations/Implications: This line of research should be further pursued, including nutritional quality aspects of the forage and diet variations between sampling years. We also recommend fostering the presence of herbaceous plants through habitat improvement techniques. Conclusions: No relation was found between diet and forage diversity. When forage diversity decreased, grass intake increased.

Visitors and observers otter-ly influence the behavior and enclosure use of zoo-housed giant otters.

The potential impact of human presence on captive animal behavior has recently been the focus of considerable research interest, especially following 2020 and 2021 periods of enforced closure as a result of COVID-19 opening restrictions. It is important to investigate whether human presence represents an enriching or stressful stimulus to a range of zoo-housed species. In 2020, during an easing of lockdown restrictions, investigations of the "visitor effect" and "observer effect" were carried out, using the giant otter (Pteronura brasiliensis) as a model species. To investigate the impact of both visitor and observer presence, otter behavior and space use was recorded for a pair of on-show and a pair of off-show otters. Observations were conducted using either a human observer, or cameras, allowing the researchers to investigate otter behavior when no one was present at the exhibits. The Electivity Index was used to assess the otters' use of four enclosure zones. Overall, otter behavior was significantly impacted by observer presence, though the impact of an observer differed between individual otters. Visitors had a minimal effect on otter enclosure use, whereas observers had a greater impact, whereby otters used their pools less frequently and houses more frequently when observers were present. However, this change in zone use differed between individuals, with more dominant otters tending to make use of indoor zones more often when observers were present. Zoos should consider the potential impact of human presence on their animals and use both behavior and space use when conducting their investigations.

Bottom‐up and top‐down control of seagrass overgrazing by the sea urchin Tripneustes gratilla

AbstractThe lack of top‐down control on Tripneustes gratilla, a sea urchin commonly known to graze on seagrass, and the bottom‐up control of its feeding preference, led to the overgrazing of seagrass meadows of the species Thalassodendron ciliatum in Changuu Island (Zanzibar Archipelago). The impact of overgrazing on seagrasses was assessed by mapping the presence of grazed versus non‐grazed seagrass patches in the study site, while the top‐down control on T. gratilla was assessed by measuring the abundance of its fish predators. The feeding preference and distribution of T. gratilla were characterized by calculating the electivity indexes for each seagrass species and measuring sea urchin density, respectively. Approximately half of the patches of T. ciliatum were overgrazed, while predatory fishes of T. gratilla were absent from the site. The Vanderploeg and Scavia's Relativized Electivity Index indicated that T. gratilla had a feeding preference for T. ciliatum, which was also supported by higher urchin densities within T. ciliatum dominated patches. Bottom‐up control of grazing activity was observed by quantifying and analyzing morphological, nutritional, and the chemical defense traits of the seagrass in relation to feeding preference and urchin density. Feeding was positively correlated to the seagrass tissue C:P ratio (ρ = 0.9), whereas urchin density showed no correlations. The bottom‐up control of the feeding preference and agglomeration of T. gratilla in T. ciliatum meadows, together with the lack of evidence of substantial top‐down control and the long recovery time of T. ciliatum led to the overgrazing of this species at this site. Overgrazing, therefore, was shown to be the result of multiple factors ranging from the traits of the seagrass and feeding preference of T. gratilla, to the abundance of predators in this area.

Dominant phytoplankton groups as the major source of polyunsaturated fatty acids for hilsa (Tenualosa ilisha) in the Meghna estuary Bangladesh

The tropical estuarine ecosystem is fascinating for studying the dynamics of water quality and phytoplankton diversity due to its frequently changing hydrological conditions. Most importantly, phytoplankton is the main supplier of ω3 polyunsaturated fatty acids (PUFA) in the coastal food web for fish as they could not synthesize PUFA. This study evaluated seasonal variations of water quality parameters in the Meghna River estuary (MRE), explored how phytoplankton diversity changes according to hydro-chemical parameters, and identified the major phytoplankton groups as the main source of PUFA for hilsa fish. Ten water quality indicators including temperature, dissolved oxygen, pH, salinity, dissolved inorganic nitrogen (DIN = nitrate, nitrite, ammonia) and phosphorus, dissolved silica and chlorophyll-a were evaluated. In addition, phytoplankton diversity was assessed in the water and hilsa fish gut. Principal component analysis (PCA) was used to analyze the spatio-temporal changes in the water quality conditions, and the driving factors in the MRE. Four main components were extracted and explained 75.4% variability of water quality parameters. The most relevant driving factors were dissolved oxygen, salinity, temperature, and DIN (nitrate, nitrite and ammonia). These variabilities in physicochemical parameters and dissolved inorganic nutrients caused seasonal variations in two major groups of phytoplankton. Peak abundance of Chlorophyta (green algae) occurred in water in nutrient-rich environments (nitrogen and phosphorus) during the wet (36%) season, while Bacillariophyta (diatoms) were dominant during the dry (32%) season that depleted dissolved silica. Thus, the decrease of green algae and the increase of diatoms in the dry season indicated the potential link to seasonal changes of hydro-chemical parameters. The green algae (53.7%) were the dominant phytoplankton group in the hilsa gut content followed by diatoms (22.6%) and both are contributing as the major source of PUFAs for hilsa fish according to the electivity index as they contain the highest amounts of PUFAs (60 and 28% respectively).

02. Investigating the behaviour and enclosure use of zoo-housed Cuvier’s dwarf caiman Paleosuchus palpebrosus

The welfare needs of reptiles in zoological collections are generally less well understood than those of other taxa. Crocodilians represent an excellent opportunity to study a commonly-housed, conservation-dependant zoo animal. We studied the behaviour and enclosure use of five dwarf caimans Paleosuchus palpebrosus through day and night, at two British zoological collections; the enclosures had either six or seven identifiable zones. Time of day, mean temperature and collection were used as predictors of behaviour and enclosure usage. Camera traps recorded the position and behaviour of caimans at 30-second intervals. At each zoo, 80 hours of data were collected from which we constructed activity budgets and calculate a relativised Electivity Index of enclosure usage. The results identified that water-based perching, floating, swimming, immobile water behaviour and underwater behaviour were significantly affected by time of day, and that collection and temperature were good predictors of some behaviours. As for enclosure use, zone 3 (shallow water) was slightly overutilised in both collections, while all other zones were underutilised. Time was a significant predictor of the use of zones 3, 5, 6 and 7. There is considerable scope for future research on crocodilians in zoos.

Patterns of variation in dietary composition among four populations of Alpine salamanders (Salamandra atra prenjensis)

Abstract In this paper we studied the diet in four allopatric populations of alpine salamanders in the Dinarides (Salamandra atra prenjensis). Food consumption was assessed by stomach flushing while food availability by pitfall traps and netting. We aimed to: (i) assess the realized dietary niche, (ii) investigate prey preferences, (ii) explore individual specialization, clustering and nestedness. All populations have an equally wide dietary span that is among the largest reported for terrestrial salamanders. On the other hand, the amount of ingested prey is rather low compared to other salamander species; the quantity of consumed prey did not differ among populations but younger individuals fed more than adults. Food composition somewhat differed among populations but not among sex/age classes. In all four populations, the bulk of diet consisted of beetles, spiders, snails and millipedes; except for beetles, such prey was also preffered together with centipedes and isopods. For most of the prey categories, the direction of the electivity indices was the same across populations. In none of the populations a nested pattern in the interindividual subdivision of dietary resources was registered. However, indications for individual specialization and modularity were observed disclosing that the broad niche of populations is composed of smaller individual niches that cluster along the dietary axis. Overall, the four populations have very similar structural characteristics of the dietary niche and there is little evidence for local dietary differentiation probably due to the absence of drivers for change.

Spatial variability in the abundance and prey selection of the corallivorous snail Drupella spp. in the southeastern Hainan Island, China

Global climate change has caused extensive loss of biodiversity and ecosystem function globally, particularly in coral reefs in shallow tropical waters. As the corallivorous snails represent considerable disturbances to coral reefs across Indo-Pacific region, it is becoming a threat to coral health and recovery in the Hainan Island, South China Sea, but current-knowledge gap remains on the spatial distribution, prey preferences, and the influence factors related. Thus, we investigated the abundance distribution of Drupella spp. in relation to coral-prey selectivity, availability, and nutritional value. The snail density was heterogeneously distributed in the study area with an average of 0.72 ± 0.32 ind m−2 (varying from 0.09 ± 0.03 to 1.78 ± 0.39 ind m−2), and the snail density was found generally higher in locations with higher coral cover, which resulted in much lower density where their preferred corals became scarce. Despite the snails showing a positive preference for Acroporidae corals, they displayed dietary plasticity by changing with prey abundance and availability. Further, we found the electivity index of the coral prey related to the substrate types, and the nutritional value of prey was an additional important determinant in the prey preference, suggesting that the specific reef habitat and environmental context may alter the prey preference of Drupella spp. Combined, these results provide preliminary evidence that Drupella spp. is among the common corallivories in the reef regions of Hainan Island, and we recommend that large-scale monitoring programs assess the spatial-temporal trends to better understand the dynamics of predation linked to both anthropogenic and natural impacts.

Postoccupancy evaluation of staff, visitors, and three species of animals in a zoo setting.

Postoccupancy evaluation (POE) was used to assess newly constructed zoo exhibits from the perspective of three user groups: zoo staff, zoo visitors, and the animals. Staff represents a generally understudied user group in zoo-based POEs. We asked staff to rate the animals' space, the visitors' space, and the staff's space at previous and new exhibits. We also compared zoo visitors' ratings of the animals' behavior and environments, overall exhibit impressions, and the time visitors spent viewing previous and new exhibits. Lastly, we compared activity and space use of a Komodo dragon (Varanus komodoensis), two red pandas (Ailurus fulgens), and one rhinoceros (Rhinoceros unicornis) in their previous and new exhibits. Staff rated animal, visitor, and staff areas higher at the new exhibits compared to the previous exhibits. Visitors also rated several factors higher and spent more time at the new exhibits. The most naturalistic exhibit received the most favorable ratings in all categories and animal activity increased visitor stay time. We found that red pandas were less active in their new exhibit, and the Komodo dragon and rhino showed no difference in activity. The red pandas and the Komodo dragon used more available space in their new exhibits; however, we recommend using Electivity index to examine resource preferences for these species, whose enclosure use has been less studied than large mammals. We emphasize the importance of including staff in zoo-based POE, make other recommendations for future POE studies, and discuss various factors that could have influenced our results.

Diet composition and trophic niche differentiation of Neogobius melanostomus along an invasion gradient in a large lowland river

The Ponto-Caspian goby Neogobius melanostomus (Pallas 1814) is a widespread non-native fish species in European rivers. It occurs in high abundance and can potentially alter the food webs of invaded water bodies profoundly. However, the invasion process usually goes unnoticed, and changes in food webs during the early stages of invasions are rarely described. Here, we studied populations of N. melanostomus along an invasion gradient in the Elbe River (Germany) and tested the effects of time since invasion on the diets and the associated trophic dynamics in two dominant habitats, i.e., rip rap and sand. Results showed that the abundance and biomass of N. melanostomus was lowest at the most recently invaded sites. The trophic niche space quantified by stable isotopes (δ ¹³ C and δ ¹⁵ N) showed that populations at earlier invaded sites exhibited a wider trophic niche than those at the most recently invaded sites. Diptera and Crustacea were the most abundant taxa in N. melanostomus guts at both habitat structures. At rip rap habitats, N. melanostomus showed a significant increasing preference for Crustacea and a decreasing one for Gastropoda along the invasion gradient. At sand habitats no significant relationships between the invasion gradient and electivity index for N. melanostomus were detected. We demonstrated that the invasion stage and habitat in which N. melanostomus occurs affect the feeding preference of this invasive fish and that these factors are therefore important for tracing changes in the macroinvertebrate communities of affected river systems.