Describe Habitat Use Research Articles

Trait‐based analyses reveal global patterns in diverse diets of albacore tuna (Thunnus alalunga)

AbstractSimplifying complex species interactions can facilitate tracking and predicting functional responses to ecological stressors. This is important for highly migratory pelagic predators, exploiting diverse prey fields as they respond to dynamic environments. We reconstructed the historical resource use of albacore tuna (Thunnus alalunga) globally from the 1900s to 2015 and confirmed highly biodiverse diets with 308 prey species, and an additional 238 taxa at coarser taxonomic resolution. We synthesised prey diversity into seven functional trait guilds using hierarchical divisive clustering algorithms as a function of four traits that describe habitat use and influence predator–prey encounter rates – prey habitat association vertically in the water column, horizontally along the coastal to pelagic gradient, seasonal and diel vertical migratory behaviour. We explored variability in historical composition of albacore diets across geographies based on species identity, individual trait information and functional trait guilds using a multi‐matrix modelling framework. Taxonomic information remains important for trophic ecology, however, species‐based diet composition in albacore tuna was highly variable across geographies and years sampled, making interpretation of these patterns difficult. By simplifying species identity into habitat‐based traits, we highlight changes in prey resources consumed, such as the historical importance of near‐surface epipelagic prey resources from coastal to oceanic habitats, and seasonally migrating continental shelf prey, with less frequent pulses of deeper water and demersal taxa. Trait information and trait guilds serve as useful classification frameworks for identifying functionally redundant food web linkages across biodiverse prey, and will prove useful in tracking predators' foraging responses to changing resource availability.

Environmental history of one of the largest freshwater neotropical fish (Zungaro jahu) from otolith isotopic analysis

AbstractThe Manguruyú Zungaro jahu, endemic to the La Plata Basin, is one of the largest neotropical fish species whose life history is virtually unknown. The objectives of this study were to determine if Z. jahu is a large‐scale migratory species and to describe habitat use throughout ontogeny using the otolith Sr isotope (87Sr/86Sr) ratio. Surface water samples were collected in 2020 at four sites representing the main water courses of the Great Pantanal in Brazil (upper Paraguay, Cuiabá, São Lourenço and Vermelho rivers). Eighteen fish individuals were collected from the Paraná River (Argentina). New water 87Sr/86Sr data were incorporated into previously established statistical models to infer the fish habitat use through the otolith 87Sr/86Sr ratios. The water 87Sr/86Sr ratio of the upper Paraguay tributaries varied (0.7209 and 0.7229) and were the highest in the La Plata Basin. The dispersal area of Z. jahu was restricted to the surroundings of the confluence of the Paraná and Paraguay rivers. Fish showed chemical signatures compatible with those of the middle Paraná (88%), Paraguay‐Pilcomayo‐Bermejo (50%) and the lower/upper Paraná (66%). The discriminant analysis based on otolith core indicated natal origins from the middle Paraná (37%), upper Paraná (32%), and Paraguay sub‐basin (32%). The dispersal area of Z. jahu migrations could be restricted to the surroundings of the confluence of Paraná and Paraguay, which highlights the need to review regional fishing regulations, especially between latitudes 30°–34° S.

Ground‐based vegetation descriptions and remote sensing as complementary methods describing habitat requirements of a frugivorous primate in northern Madagascar: implications for forest restoration

AbstractNon‐human primate species are threatened worldwide. Their population declines go along with the loss of ecological functions such as seed dispersal that plays a crucial role in plant regeneration. Restoring essential habitat structures could thus not only protect primates, but also facilitate forest regeneration. We used classical vegetation description on the ground and a remote sensing analysis to describe habitat use of crowned lemurs (Eulemur coronatus), a seed‐dispersing primate endemic to northern Madagascar. Our aim was to find vegetation characteristics important for lemurs that might be targeted in a restoration approach. For this, we applied both methods in differently degraded forest types. Both classical vegetation description and remote sensing analysis were able to distinguish these forest types. The habitat use of our two study groups was associated consistently with vegetation structures measured on a small scale such as tree height and density of thick trees. In contrast, vegetation productivity and water content derived from satellite imagery on a larger scale could not consistently explain habitat use of lemurs. Thus, measurements on the ground can identify suitable microhabitats that do not show on the satellite imagery scale. These microhabitats might be very important conservation elements to create buffer zones and corridors. Further, they might attract seed‐dispersing species into degraded areas targeted for forest restoration, acting as natural regeneration nuclei. The potential of these microhabitats for conservation would not be recognized when analyses were based solely on landscape analyses on large scales.

Scientific response to a cluster of shark bites

Abstract Shark bites are of high public concern globally. Information on shark occurrence and behaviour, and of the effects of human behaviours, can help understand the drivers of shark‐human interactions. In Australia, a number of shark bite clusters occurred over the last decade. One of these took place in Cid Harbour the Whitsundays, Queensland, a region for which little was known about the shark community. Here, we describe and evaluate the research in response to that shark bite cluster. Fishing methods, acoustic and satellite tracking, and baited remote underwater video cameras (BRUVs) were used to identify the shark species using Cid Harbour, estimate relative abundance, and describe habitat use and residency. Side‐scan sonar and BRUVs were also used to assess prey availability. Recreational users were surveyed to understand human behaviour and their awareness and perceptions of ‘Shark Smart’ behaviours. This allowed shark occurrence and behaviour to be interpreted in the context of human behaviours in the Harbour. Eleven shark species were identified. Relative abundance was not unusually high, and residency in Cid Harbour was typically low. For example, 79% of acoustically tagged sharks visited the harbour on <10% days at liberty. Shark prey was available year‐round. Notably, anchored boats regularly conduct activities that can attract sharks (dumping food scraps, provisioning and cleaning fish). Alone, the methods used in this study had variable success, but combined they provided a large amount of complementary information. Including a social science component in the research response to the shark bite incidents allowed for a more holistic understanding of the Cid Harbour bite incidents. This study did not identify anything unusual about the shark community that could have contributed to the Cid Harbour shark bite cluster. However, the three incidents involved people bitten almost instantly after entering the water, which is unusual and suggests that feeding/attracting sharks to boats could have been a contributor and also that any species capable of biting humans could have been responsible. The eradication of activities that attract sharks to areas where people enter the water may reduce shark bite risk. Read the free Plain Language Summary for this article on the Journal blog.

USO DE HÁBITAT POR ZORRO GRIS (Urocyon cinereoargenteus, CARNIVORA: CANIDAE) EN UN ECOSISTEMA TROPICAL ANTROPIZADO

<p><strong>Background. </strong>Gray fox, <em>Urocyon cinereoargenteus</em> is tolerant to habitat disturbance, but the biotic and abiotic factors that determine the selection of space in the subperennial medium forest (SMF) with different degrees of anthropization are not known, which is relevant to explain a fraction of an animal’s niche. <strong>Objective.</strong> We described the use of habitat by the gray fox, in four habitat units in the SMF, with different degrees of anthropization. <strong>Methodology.</strong> We classified four habitat units with vegetation structure criteria: Sugar cane-coffee plantation, Coffee plantation-forest, forest and Coffee plantation, where we evaluated parameters such as number of carnivores and potential prey and plant cover. In addition, we evaluated the altitude, temperature, precipitation and evaporation. Using indirect techniques, we obtained gray fox records in each habitat unit, which we related to biotic and abiotic parameters through a χ<sup>2</sup> test and a partial least squares analysis; we applied a dendrogram to estimate the similarity of use of the habitats; and a response surface-based model to describe habitat use. <strong>Results.</strong> We associated fourteen independent records of gray fox and six of them with the Coffee plantation-SMF habitat, where it was correlated with temperature. <strong>Implications.</strong> Shrub coverage, the number of competitors and evaporation in SMF and Coffee plantation-SMF are factors correlated with a low number of gray fox records. <strong>Conclusion.</strong> In this ecosystem anthropized by the production of coffee and sugarcane, the gray fox may be using open habitats for hunting and closed habitats to seek refuge while it is not active.</p>

On the habitat use and foraging ecology of the Yellow-headed Brushfinch (Atlapetes flaviceps), an endemic species of conservation concern from Colombia

Natural history information is one of the major knowledge gaps in Neotropical ornithology. Several range-restricted and threatened species in the region are still poorly known, hindering the design of effective conservation programs. Here, we used direct observations collected at 7 localities throughout the Tropical Andes to describe habitat use and foraging ecology of the Yellow-headed Brushfinch (Atlapetes flaviceps), a species of conservation concern and endemic to Colombia. Our observational records (n = 174) indicate that this species mainly occurs in secondary forests and landscape mosaics that include patches of native vegetation and agricultural areas, but it seems to be frequently associated with the presence of regenerating vegetation in early successional stages. We found that the species' diet was mainly composed of fruits and invertebrates, although other items are occasionally included. Although our data suggest the possibility of an association between habitat type and the activity recorded, as well as temporal variation in foraging behavior, this requires more research. Our observations support the idea of this species being tolerant to human-altered habitats, but this needs to be confirmed by measuring habitat-specific productivity and survival. The results presented here not only increase knowledge of this poorly known endemic but can be useful for the subsequent implementation of management strategies aimed at increasing the availability of high-quality habitat.

Predicting habitat use by the Argentine hake Merluccius hubbsi in a warmer world: inferences from the Middle Holocene.

Fish skeletal remains recovered from two archaeological sites dated in the Middle Holocene of Tierra del Fuego (Argentina) were analysed to describe habitat use patterns by hake in the past and predict changes in a warmer world. Mitochondrial DNA was successfully extracted and amplified from 42 out of 45 first vertebra from ancient hake and phylogenetic analysis assigned all haplotypes to Argentine hake (Merluccius hubbsi). According to osteometry, the Argentine hake recovered from the archaeological site were likely adults ranging 37.2-58.1cm in standard length. C and N stable isotope analysis showed that currently Argentine hake use foraging grounds deeper than those of Patagonian blenny and pink cusk-eel. Argentine hake, however, had a much broader isotopic niche during the Middle Holocene, when a large part of the population foraged much shallower than contemporary pink cusk-eel. The overall evidence suggests the presence of large numbers of Argentine hake onshore Tierra del Fuego during the Middle Holocene, which allowed exploitation by hunter-gatherer-fisher groups devoid of fishing technology. Interestingly, average SST off Tierra del Fuego during the Middle Holocene was higher than currently (11°C vs 7°C) and matched SST in the current southernmost onshore spawning aggregations, at latitude 47°S. This indicates that increasing SST resulting from global warming will likely result into an increased abundance of adult Argentine hake onshore Tierra del Fuego, as during the Middle Holocene. Furthermore, stable isotope ratios from mollusc shells confirmed a much higher marine primary productivity during the Middle Holocene off Tierra del Fuego.

Foraging Habitat, Home-Range Size and Diet of a Mediterranean Bat Species, Savi's Pipistrelle

The Mediterranean is considered one of the richest biodiversity regions in Europe, and bats contribute to this species richness. Within the last two decades, certain bat species traditionally considered as representatives of the Mediterranean have spread northwards and colonized areas outside this region. In our study, we focused on ecological requirements of one of these bat species, the Savi's pipistrelle (Hypsugo savii). We used radio-telemetry and diet analysis to describe habitat use, home-range size and diet composition of reproductive females of Savi's pipistrelle in the traditional core of its distribution range in the Mediterranean region. Our results indicate that Savi's pipistrelle is able to fly long distances and utilize a wide range of habitats within its home-range, with affinities for particular habitats depending on its reproductive status. In particular, pregnant females favoured rocky pastures and forest areas, followed by meadows and riparian habitat, whereas the affinity for riparian habitat increased in lactating females, followed closely by meadows, forest and rocky pastures. The larger affinity for riparian habitats during lactation might indicate its importance for successful rearing of young, which could be influenced in the future by increasing droughts and water shortage in the Mediterranean region. Nevertheless, based on our radio-telemetry and diet analysis the species shows a high degree of flexibility, as an opportunistic forager that flies across large areas on a nightly basis, which may be a good predisposition for colonizing new areas.

Habitat use by Asian elephants: Context matters

Asian elephants are isolated in fragmented habitat patches in and around Bardia National Park (BNP), Nepal. To describe habitat use patterns and ecogeographical variables (EGVs) that determine an elephant's niche in BNP, we used a General Niche-Environment System Factor Analysis (GNESFA) modeling framework. Novel to our study was the comparison of niche requirements between core (residential) and corridor (travel corridor) areas to elucidate site-specific preferences of Asian elephants in BNP. A total of 13 EGVs (four topographic variables, six land covers, heterogeneity index and two anthropogenic variables) were examined. We implemented a ‘bias file’ approach to address potential sampling bias in the transect survey methods for presence records. Our study illustrated that, regardless of study area, elephants' habitat use was positively influenced by presence of grasslands, mixed forest, and landscape heterogeneity, whereas use was restricted by the topographic variables of slope and elevation. Results also demonstrated different habitat preferences between elephants in the core and corridor, which may be attributed to differences in potential dangers posed in these areas; in the core, elephant habitat preference was mainly associated with food resources such as grassland or mixed forest, whereas in the corridor, where elephants are more likely to encounter human conflict, the anthropogenic factor of distance to human settlements contributed the most in predicting elephant presence. Correlations among significant factors from the three methods (FANTER, ENFA, and MADIFA) demonstrated the consistent and reliable results of these approaches. While these methods complemented each other by providing different points of view, FANTER was especially useful when bimodal niches were analyzed. We suggest a detailed conservation plan for the small populations of elephants in BNP and surrounding areas, while considering the protection of travel routes from human activities in the corridor habitats, and lastly, maintaining grasslands and waterholes in core habitats.

Mallard survival, movements, and habitat use during autumn in Illinois

ABSTRACTThe Illinois River Valley (IRV) in central Illinois, USA, provides migratory stopover habitat for millions of waterfowl during autumn and spring in the Mississippi Flyway. Mallards (Anas platyrhynchos) are the most abundant species of waterfowl during autumn migration and the most harvested duck in Illinois. We investigated mallard migration ecology in central Illinois, USA, to address information needs of biologists and managers in the Upper Mississippi River and Great Lake Region Joint Venture and Illinois Department of Natural Resources. Our objectives were to document daily movements and identify factors affecting inter‐wetland movements, investigate lengths of foraging flights, assess home range size during stopover, describe habitat use and identify factors associated with wetland use, estimate survival and cause specific mortality, and evaluate proportional use of refuges and areas open to hunting in and nearby the IRV by mallards. We employed standard radio‐telemetry techniques to achieve our objectives during autumns and early winters 2009 and 2010 (n = 86 F and 56 M mallards). The mean movement distance between locations collected on consecutive days was 2,822 ± 120 (SE) m (n = 1,862; max. = 56,966 m) across age, sex, and months. Female mallards (n = 35) traveled 2,708 ± 191 m during evening foraging flights (n = 145) to agricultural fields and emergent marshes. Mean home range size (95% minimum convex polygon) was 21,306 ± 1,925 ha across sex and age classes (n = 81 mallards). We documented 43 mortalities of 142 radio‐marked mallards (2009: 28.2%; 2010: 32.3%) with 85.0% and 69.6% of deaths attributed to hunting in 2009 and 2010, respectively. Body condition, hunting period, age, year, minimum daily temperature, and daily movement distance were important variables affecting survival, but differences were most pronounced for year and hunting period. Overall survival was greater in 2010 (Ŝi = 0.62) than 2009 (Ŝi = 0.39) and daily survival rates were 0.8% and 0.4% greater during closed than open hunting periods in 2009 and 2010, respectively. Mallards used open water most frequently across years (49.4% daily locations), followed by corn (dryland, flooded, standing, or harvested; 16.3%), herbaceous (10.6%), woody (10.5%), and other wetlands and upland cover types. Use of areas closed to hunting was low (18.7%) and most diurnal locations of mallards occurred in wetlands open to hunting (81.3%; i.e., not designated as refuge by statute). Similar to diurnal habitat use, female mallards returning from evening foraging flights (n = 138) used areas open to hunting (81.9%) more than refuges (18.1%). Refuges that were primarily composed of open water received low use by autumn‐migrating mallards in the IRV. Restoration or rehabilitation of moist‐soil and emergent wetlands within statutory refuges protected from unnatural flood regimes may improve foraging habitat quality and increase survival for mallards and other ducks during migration. © 2017 The Wildlife Society.

Habitat Use of Migratory Shorebirds on the Coastline of Deli Serdang Regency, North Sumatra Province

Mangrove forests an intertidal mudflat in the eastern coastal region of Deli Serdang are important habitats for migratory shorebirds. Land-use change and forest conversion threaten this important stopover point for migrating species. The lack of data and information of shorebirds habitats in this area limits conservation efforts and further threatens the survival of these species. The objective of this study is to investigate trends in habitat use by migratory shorebirds. Field work was conducted during migration season starting from October 2014 until April 2015. The presence of migratory shorebirds was assessed using binoculars and a monocular. Scan sampling was used to describe habitat use by shorebirds. The difference in behaviour among habitat was analyzed using analysis of variance. There were 30 species of shorebirds distributed across seven different habitat types in our study area. The most widely used habitat by shorebirds was mudflats, followed by marshes and plantations. This study revealed that mudflat habitat has high potential in supporting the existence of migratory shorebirds in this area.

Home range and habitat use of juvenile green turtles (Chelonia mydas) in the northern Gulf of Mexico

For imperiled marine turtles, use of satellite telemetry has proven to be an effective method in determining long distance movements. However, the large size of the tag, relatively high cost and low spatial resolution of this method make it more difficult to examine fine-scale movements of individuals, particularly at foraging grounds where animals are frequently submerged. Acoustic telemetry offers a more suitable method of assessing fine-scale movement patterns with a smaller tag that provides more precise locations. We used acoustic telemetry to define home ranges and describe habitat use of juvenile green turtles at a temperate foraging ground in the northern Gulf of Mexico. We outfitted eight juvenile green turtles with acoustic transmitters and tracked them from 14 to 138 days from September 2012 to February 2013 in St. Joseph Bay, Northwest Florida. Mean home range size was relatively small compared to other studies. For four turtles, we observed a moderate inverse relationship between water temperature and water depth which is consistent with the idea that turtles moved to deeper waters when temperatures cooled. On average distance to the channel from turtle locations were different by bottom cover type. These turtles appear to forage in shallow-water seagrass beds that border deep channels. When water temperatures dropped in winter, some of the tracked turtles moved to a deep-water channel on the western side of the study site. Turtles whose foraging sites were farther from the deep-water channel exhibited greater displacement than those with sites that were closer to the channel. Green turtles in St. Joseph Bay have relatively small home ranges and many contain multiple activity centers. The frequent use of channels by turtles suggests bathymetry plays a major role in habitat selection of juvenile green turtles, particularly as temperatures drop in winter. The quality and density of seagrass habitat in St. Joseph Bay and its proximity to deep channels appears to provide ideal conditions for juvenile greens. The results of this study help define characteristics of foraging habitat utilized by juvenile greens in the northern Gulf of Mexico that managers can use in creating protected areas such as aquatic preserves.

Use of Arctic ground squirrels (Urocitellus parryii) by brown bears (Ursus arctos)

Brown bears (Ursus arctos) in the Mackenzie Delta in the Northwest Territories of Canada are at the northern edge of their range and persist in a nutrient poor environment with limited available protein. Arctic ground squirrels (Urocitellus parryii) are widespread across northern Canada and are often cited as an important protein source for brown bears. We hypothesized that Arctic ground squirrels form an important part of brown bear diet in the Mackenzie Delta region, and that their importance varies seasonally, with peak use occurring during bears’ pre-dormancy hyperphagic period, as well as annually with fluctuating availability of other food. To investigate the seasonal use of Arctic ground squirrels by brown bears, we used resource selection function analysis to describe habitat use, stable isotope analysis to determine individual trophic level and examine its relationship with habitat use, and GPS satellite telemetry to facilitate site investigations. Arctic ground squirrel habitat was not a significant covariate in resource selection functions for pooled sexes, pooled females, and pooled males. However, at the individual level, bears displayed a range of behaviors from selection against, no selection, to selection for Arctic ground squirrel habitat. We found no significant interannual variation in use of Arctic ground squirrel habitat. Site investigations and stable isotopic values for individual bears also suggest a range of foraging behaviors for Arctic ground squirrels. Individual resource selection models combined with trophic level and site investigations provide support for limited use of Arctic ground squirrels that varied between individuals and provided additional evidence for the diversity of niches exploited by individuals.

High plasticity in habitat use of Lycengraulis grossidens (Clupeiformes, Engraulididae)

In this study, we analyzed the Sr:Ca and Ba:Ca ratios of the otoliths of 139 Lycengraulis grossidens individuals sampled along the southwestern Atlantic Ocean, including two freshwater areas, to describe patterns of habitat use and their latitudinal organization. Otolith sections were analyzed by laser ablation inductively coupled plasma mass spectrometry along core-to-edge transects. Otolith edge analysis revealed significant differences in Sr:Ca and Ba:Ca ratios between fish from freshwater habitats and those from estuarine/marine habitats, indicating that these ratios may be used to describe habitat use patterns. Lifetime transects of Sr:Ca and Ba:Ca indicate at least four distinct habitat use patterns: freshwater residents, estuarine/marine residents, and two distinct diadromous/nomadic types. Most individuals (88.6%) sampled at northern latitudes in sheltered marine bays and the coastal ocean were estuarine/marine residents, whereas at southern latitudes, most individuals were diadromous (72.5%). We also identified landlocked populations in the Uruguay River and in Mirim Lagoon. These results suggest that L. grossidens exhibits flexible habitat use strategies and may use freshwater, estuarine and marine environments throughout their lifetime.

Survival and habitat use by fledgling northern flickers in a fragmented forest landscape

ABSTRACTThe post‐fledging dependency period of birds is often characterized by high juvenile mortality, but fledglings in specific habitats may have increased survivorship. We describe habitat use by fledgling northern flickers (Colaptes auratus) in relation to the availability of patchy forest and prairie habitat in central British Columbia, Canada. We used radiotelemetry to monitor survival of fledglings according to their use of habitats during the dependency period. The fledglings occupied habitats with a higher density of trees than either random locations or nest sites and they switched from forested areas to more open grasslands after 7–10 days post‐fledging. Some moved >1 km from the nest within 4 days post‐fledging. Fledglings from nests in small tree clusters with little forest cover within 250 m moved farther from their nest within the first 4 days post‐fledging than fledglings from nests in larger forest patches. Fledgling survival was positively correlated with the amount of canopy cover and negatively correlated with the amount of forest cover at the larger landscape scale. Young flickers moved among habitat types, which may occur as a result of trade‐offs between predation risk and food abundance between habitats. We conclude that fledgling flickers at younger ages used dense forested areas and grassland habitat and forest at older ages to maximize survival and to access food sources. Maintaining patches of dense cover and the amount of forest cover on less than 35% of the landscape may improve fledgling survival of flickers. © 2014 The Wildlife Society.

Investigating Annual Diving Behaviour by Hooded Seals (Cystophora cristata) within the Northwest Atlantic Ocean

With the exception of relatively brief periods when they reproduce and moult, hooded seals, Cystophora cristata, spend most of the year in the open ocean where they undergo feeding migrations to either recover or prepare for the next fasting period. Valuable insights into habitat use and diving behaviour during these periods have been obtained by attaching Satellite Relay Data Loggers (SRDLs) to 51 Northwest (NW) Atlantic hooded seals (33 females and 18 males) during ice-bound fasting periods (2004−2008). Using General Additive Models (GAMs) we describe habitat use in terms of First Passage Time (FPT) and analyse how bathymetry, seasonality and FPT influence the hooded seals’ diving behaviour described by maximum dive depth, dive duration and surface duration. Adult NW Atlantic hooded seals exhibit a change in diving activity in areas where they spend >20 h by increasing maximum dive depth, dive duration and surface duration, indicating a restricted search behaviour. We found that male and female hooded seals are spatially segregated and that diving behaviour varies between sexes in relation to habitat properties and seasonality. Migration periods are described by increased dive duration for both sexes with a peak in May, October and January. Males demonstrated an increase in dive depth and dive duration towards May (post-breeding/pre-moult) and August–October (post-moult/pre-breeding) but did not show any pronounced increase in surface duration. Females dived deepest and had the highest surface duration between December and January (post-moult/pre-breeding). Our results suggest that the smaller females may have a greater need to recover from dives than that of the larger males. Horizontal segregation could have evolved as a result of a resource partitioning strategy to avoid sexual competition or that the energy requirements of males and females are different due to different energy expenditure during fasting periods.

Grazing effects of the sea urchinTetrapygus nigerand the snailTegula atraon a rocky shore of central Peru

Here we describe habitat use and the grazing effects of the sea urchinTetrapygus nigerand the gastropodTegula atrain the low intertidal zone of a rocky shore in central Peru (Ancón bay: 11°46′S 77°12′W), where these two species were documented as coexisting with no evidence of habitat segregation between them. Gut content and isotopic analyses revealed differences between their diets:T. atraconsumes mainly microalgae whileTetrapygus nigerconsumed also benthic macroalgae. Individual grazing effects were evaluated with inclusion/exclusion experiments.Tetrapygus nigerprevented the colonization of the substrate by sessile organisms, including the dominant musselSemimytilus algosus, whileTegula atrareduced the abundance of microalgae and green ephemeral macroalgae during early succession, but these effects were overwhelmed by the rapid increase in cover ofS. algosus. We suggest thatTetrapygus nigerplays a key role in this low intertidal community. Through directly limiting mussels to monopolize the substratum,T. nigercan reduce the diversity of mussel associated species; conversely, through controlling primary space holders,T. nigercan also benefit other grazers that live on bare substrate by maintaining a suitable area for feeding or living.

Estimating breeding season abundance of golden‐cheeked warblers in Texas, USA

AbstractPopulation abundance estimates using predictive models are important for describing habitat use and responses to population‐level impacts, evaluating conservation status of a species, and for establishing monitoring programs. The golden‐cheeked warbler (Setophaga chrysoparia) is a neotropical migratory bird that was listed as federally endangered in 1990 because of threats related to loss and fragmentation of its woodland habitat. Since listing, abundance estimates for the species have mainly relied on localized population studies on public lands and qualitative‐based methods. Our goal was to estimate breeding population size of male warblers using a predictive model based on metrics for patches of woodland habitat throughout the species' breeding range. We first conducted occupancy surveys to determine range‐wide distribution. We then conducted standard point‐count surveys on a subset of the initial sampling locations to estimate density of males. Mean observed patch‐specific density was 0.23 males/ha (95% CI = 0.197–0.252, n = 301). We modeled the relationship between patch‐specific density of males and woodland patch characteristics (size and landscape composition) and predicted patch occupancy. The probability of patch occupancy, derived from a model that used patch size and landscape composition as predictor variables while addressing effects of spatial relatedness, best predicted patch‐specific density. We predicted patch‐specific densities as a function of occupancy probability and estimated abundance of male warblers across 63,616 woodland patches accounting for 1.678 million ha of potential warbler habitat. Using a Monte Carlo simulation, our approach yielded a range‐wide male warbler population estimate of 263,339 (95% CI: 223,927–302,620). Our results provide the first abundance estimate using habitat and count data from a sampling design focused on range‐wide inference. Managers can use the resulting model as a tool to support conservation planning and guide recovery efforts. © 2012 The Wildlife Society.

Effects of urbanization on carnivore species distribution and richness

Urban development can have multiple effects on mammalian carnivore communities. We conducted a meta-analysis of 7,929 photographs from 217 localities in 11 camera-trap studies across coastal southern California to describe habitat use and determine the effects of urban proximity (distance to urban edge) and intensity (percentage of area urbanized) on carnivore occurrence and species richness in natural habitats close to the urban boundary. Coyotes (Canis latrans) and bobcats (Lynx rufus) were distributed widely across the region. Domestic dogs (Canis lupus familiaris), striped skunks (Mephitis mephitis), raccoons (Procyon lotor), gray foxes (Urocyon cinereoargenteus), mountain lions (Puma concolor), and Virginia opossums (Didelphis virginiana) were detected less frequently, and long-tailed weasels (Mustela frenata), American badgers (Taxidea taxus), western spotted skunks (Spilogale gracilis), and domestic cats (Felis catus) were detected rarely. Habitat use generally reflected availability for most species. Coyote and raccoon occurrence increased with both proximity to and intensity of urbanization, whereas bobcat, gray fox, and mountain lion occurrence decreased with urban proximity and intensity. Domestic dogs and Virginia opossums exhibited positive and weak negative relationships, respectively, with urban intensity but were unaffected by urban proximity. Striped skunk occurrence increased with urban proximity but decreased with urban intensity. Native species richness was negatively associated with urban intensity but not urban proximity, probably because of the stronger negative response of individual species to urban intensity.

Habitat Use of the Tuxedo Darter (Etheostoma lemniscatum) at Macrohabitat and Microhabitat Spatial Sclaes

ABSTRACT Underwater observation was used to quantify patterns of habitat use for the tuxedo darter (Etheostoma lemniscatum) throughout its range in the Big South Fork of the Cumberland River. Macrohabitat and microhabitat variables were recorded at 12 sites from July through early October in summer of 2008 and 2009. Probability of tuxedo darter presence at a site increased with available cobble substrate and shallow pool habitat. Preferred summer microhabitat included depths between 20 and 80 cm, velocities less than 0.1 m/s, and cover rocks with surface areas between 200 and 1400 cm2. Although other variables may affect presence, tuxedo darter distribution was limited by the availability of suitable habitat. Due to environmental variation in annual flow regimes, our models describe habitat use during drought and during above average flows. Models from this study identify critical tuxedo darter habitats, which can aid recovery efforts by identifying potential monitoring and reintroduction sites.