Habitat selection by adult walleye during spawning season in irrigation reservoirs: a patch occupancy modeling approach

Recruitment of walleye (Sander vitreus Mitchill) is limited in irrigation reservoirs of the Republican River basin in southwestern Nebraska. The causal mechanism for this limited recruitment is unknown, but may be related to a lack of suitable spawning habitat. Patch occupancy models were developed to describe variation in detection probability and habitat selection during spawning season using shoreline electrofishing data. Detection of adult walleye was negatively affected by water temperature, silt substrate, and woody cover. Adult walleye selected sites with cooler water temperatures and greater fetch at Enders Reservoir, and large rock substrate and no cover at Hugh Butler Lake; these characteristics are limited to areas on or near the riprap dams in both reservoirs. Walleye eggs were also only found in these areas. We conclude that patch occupancy modeling provided valuable information when considering habitat improvement projects and propose a management approach for the addition of walleye spawning habitat in irrigation reservoirs.     

Habitat selection by western snowy plovers during the nonbreeding season

Conservation of rare populations requires managing habitat throughout the year, especially during winter when northern populations may be limited by food and predation. Consequently, we examined distribution of nonbreeding western snowy plovers (Charadrius alexandrinus), including individually marked birds that were year-round residents and others that were migrants, in coastal northern California. Over 2 years, banded plovers exhibited high site faithfulness, occupying small linear stretches of beach (752 ± 626 m). Sites occupied by plovers had more brown algae (e.g., Macrocystis, Nereocystis, Postelsia, and Fucus) and associated invertebrates (e.g., amphipods, and flies), were wider, and had less vegetation than unoccupied sites. Our findings suggest that wintering plovers select habitats with more food and where they could more easily detect predators. Maintaining habitat with attributes that support abundant food (i.e., brown algae) and reduce predation risk (i.e., wide beaches, limited obstructive cover) may be important to individual survival and maintaining the Pacific Coast population of snowy plovers. Protecting occupied sites from human disturbance, which adversely alters nonbreeding habitat (i.e., beach grooming) and directly causes mortality, may be essential for conserving the Pacific coast population of the snowy plover, and it may benefit other shorebirds. © 2011 The Wildlife Society.     

Habitat modifications by sea lampreys (Petromyzon marinus) during the spawning season: effects on sediments

This study evaluated the habitat modifications of sea lampreys (Petromyzon marinus) during their spawning season. Males are responsible for digging circular or oval shape nests with lengths varying between 0.80 and 2.25 m (mean 1.49 m ± 0.43 SD). Females join later during the final phase of the process. Nest depth varies between 0.20 and 0.40 m (mean 0.28 m ± 0.07 SD). Significant differences in the mean particle size of the sediments were detected (F = 126.7; P < 0.01); sediments from the edge of the nest were coarser than the control plots, and sediments from the center of the nest were the finest. This species clearly changes the sediments in the spawning areas by altering the structure of the riverbed, with possible reverberating effects on other organisms. The burrows created by the sea lampreys remained intact for several months despite significant daily changes in the current velocity due to upstream dam operations. Given these results, and recognizing the great ecological importance of this species worldwide, their spawning activities should be taken into account in future ecological studies.     

Habitat selection by adult Golden Eagles Aquila chrysaetos during the breeding season and implications for wind farm establishment

Capsule: Global Positioning System (GPS)-tagged adult Golden Eagles Aquila chrysaetos breeding in forests in northern Sweden selected clear-cuts, coniferous forests with lichens and steep slopes during the breeding season but avoided wetlands and mixed forest.

Aims: To investigate the habitat selection patterns of tree-nesting Golden Eagles, and identify how potential conflicts with wind farm development could be minimized.

Methods: The study is based on GPS tracking data from 22 adult eagles. We estimated home range sizes using a biased random bridge approach and habitat selection patterns using resource selection functions following a use-availability design.

Results: Core home range size among adults was variable during the breeding season (5–30?km²). Individual movement extents were variable, but sexes did not significantly differ in their scale of movement. At the landscape scale, individuals selected for clear-cuts and coniferous forest with ground lichens, whereas wetland, water bodies and mixed forest were avoided. Steeper and south facing slopes were selected for, whereas, north facing slopes were avoided.

Conclusions: Potential conflicts between eagles and wind energy establishment can be reduced if wind farms are placed away from steep slopes, minimizing areas that are clear-cut during construction, and locating turbines within dense, young and other less favoured forest habitats.     

Habitat preferences of sympatric sandgrouse during the breeding season in Spain: a multi-scale approach

Predictive species’ distribution models may answer ecological questions about habitat selection, co-occurrence of species and competition between them. We studied the habitat preferences and segregation of two sympatric species of declining sandgrouse, the black-bellied sandgrouse (Pterocles orientalis) and the pin-tailed sandgrouse (Pterocles alchata), during the breeding season. We developed predictive models that related sandgrouse presence to environmental variables at three different spatial levels: large geographical, landscape and microhabitat scales. At the large geographical scale, differences between sandgrouse distributions, in the Iberian Peninsula, seem to be explained mainly in terms of bioclimatology: pin-tailed sandgrouse appear to be a more thermophilous species and occupy warmer sites usually located in flatter areas. At the landscape spatial level, in those areas that exhibit environmental conditions allowing for both species’ co-existence at a large geographical scale, black-bellied sandgrouse appear to be more tolerant to environmental variation than pin-tailed sandgrouse. At the microhabitat level, however, differences between species could be related to different flocking behaviour as a consequence of different sensitivities to vegetation structure and predators. Thus, the observed spatial distribution patterns are the result of different ecological factors that operate at different spatial levels. Conservation guidelines for these species should therefore consider their habitat preferences at large geographical, landscape and microhabitat scales.     

Habitat selection by helminths: a hypothesis

How do liver worms find the liver? Why are heartworms always found in the heart? Attempts to answer these questions have invariably yielded inconclusive results. A major problem has been the use of models or hypotheses derived from studies of free-living organisms. The parasite's environment is distinct from free-living environments in several fundamental ways and these differences will impact on the evolution of parasite behaviours. In this article, Michael Sukhdeo outlines a hypothesis for habitat selection behavior of helminths that is based on the specific environmental conditions within the host.     

Movements of lumpsucker females in a northern Norwegian fjord during the spawning season

The lumpsucker Cyclopterus lumpus is distributed throughout the North Atlantic Ocean and migrates considerable distances between offshore feeding areas and shallow inshore spawning grounds. The number of the lumpsucker has declined since the mid 1980s, probably as a result of overexploitation. The lumpsucker is the preferred host of the sea louse Caligus elongates, which is a problem for marine aquaculture. However, little is known about the biology of the lumpsucker. The aims of the study were to 1) examine the movements of female lumpsucker during the spawning migration, and 2) assess the potential for lumpsucker to act as a vector for transmission of parasites and diseases between aquaculture farms and wild fish. Twenty female lumpsuckers tagged with acoustic transmitters were released during the spawning season in the inner part of Øksfjord, northern Norway and their distribution was recorded by 22 automatic acoustic receivers. The average time until departure from the fjord was 3 days, and within 1 week all fish had left the fjord. Timing of departure from the fjord was unrelated with either tidal current patterns or the time of the day. A high proportion of the fish (75%) were recorded within 200 m of fish farms, but they did not stay for extended periods at these farms. Our results suggest that mature female lumpsucker exhibit a movement pattern characterized by rapid fjord-scale migrations during the spawning season, and that they are not attracted to salmon farms in the same way as a range of other fish species.     

Habitat selection by an Alpine ungulate: the significance of forage characteristics varies with scale and season

Habitat selection in ungulates should ensure access to abundant forage of sufficiently high quality. Species living in rugged mountain areas have to face nutritional bottlenecks regularly and should show particularly sophisticated habitat selection behaviour. However, patterns and mechanisms of such adaptations remain little studied. We analysed habitat selection and its seasonal variability of 10 GPS‐collared red deer Cervus elaphus living in a topographically challenging landscape of the Swiss Alps. We hypothesised that resource selection by red deer was scale‐dependent and predicted that scale‐dependence would vary among seasons in relation to seasonal changes of available forage biomass and quality, which we sampled across the entire study area of 250 km². The studied population of Alpine red deer undertook altitudinal migrations and showed scale‐dependent habitat selection that was strongest in winter and declined through spring and summer. Selection occurred mostly at the larger (landscape/home‐range location) scale and less so at the smaller (within home‐range) scale. Topographic parameters were selected mainly at the landscape scale and mostly in winter. About 70% of all instances of preference for habitat parameters were associated with above‐average forage characteristics, represented mostly by higher crude protein content, in a few cases also by higher biomass or both. The overall pattern of space use by red deer characterised by migration and seasonal habitat selection was therefore closely linked to the quality of food resources, although some trade‐offs with avoiding human disturbance may also have been involved.     

Habitat selection by small mammals in a Victorian heathland

Habitat preferences of five species of small mammals were studied on a 6.6 ha trapping grid in heathland on an undulating, deep, sandy podzol at Cranbourne, Victoria. The 120 sites were sorted into groups using a polythetic, agglomerative, non-hierarchical clustering procedure with (i) floristic and (ii) structural data. The dispersion of 4051 trap captures over 28 months was studied in relation to these groupings. Rattus lutreolus showed no preference for any of the structural groups, but good differentiation was obtained with the floristic groups. Dispersion of R. lutreolus was related to a sedge-food index, and seasonal change in R. lutreolus dispersion was related to change in rainfall. The preference of R. rattus for areas of wet heath of high structural complexity was best revealed using the structural classification. The results for the other species tended to favour the floristic rather than structural groups. Pseudomys novaehollandiae and Isoodon obesulus preferred dry heath of a younger successional stage. Mus musculus captures showed a preference for the dry heath generally. This preference was most pronounced in spring when the population was declining. The wet community species (R. lutreolus, R. rattus) tended to be food specialists and habitat generalists and the dry community species P. novaehollandiae, I. obesulus, M. musculus), exhibited converse traits.     

Habitat use by seed-eating birds: a scale-dependent approach

The seedbank in arable farmland represents an important foraging resource for birds, particularly in grassland landscapes where alternative foraging opportunities may be scarce. We used a stepwise approach to examine the importance of seed food resources for farmland birds in winter. First, results from a large-scale experiment in which seed resources were manipulated to test the notion that birds aggregate at food resources, subject to a minimum threshold level. Secondly, a multiscale approach was used to characterize habitat use at a landscape scale and how this may inform agri-environment implementation. Overall seed resources declined sharply over the winter and were relatively low in most arable fields. Large-scale declines in the arable seedbank mean that much habitat may not be of sufficient quality to support foraging bird populations through a winter. At a landscape scale, extensive analyses of breeding season abundance show that bird abundance is most influenced by arable (i.e. seed-rich) habitat in grassland landscapes. The scale at which birds respond to habitat differs between species, and is related to the extent of between-season movements. Implementation of agri-environment schemes will need to consider both the quality of habitat and the context in which it is provided if recent declines in farmland bird populations are to be reversed.     

Habitat degradation increases stress-hormone levels during the breeding season,and decreases survival and reproduction in adult common lizards

The allostatic load model describes how individuals maintain homeostasis in challenging environment and posits that costs induced by a chronic perturbation (i.e., allostatic load) are correlated to the secretion of glucocorticoids, such as corticosterone. Habitat perturbations from anthropogenic activities are multiple and functional responses to those are still unclear. Here, we manipulated the habitat quality in 24 semi-natural populations of the common lizard during 1 year. We tested the predictions of the allostatic load model that habitat degradation should increase baseline corticosterone levels, and should induce concomitant physiological changes, such as lipid mobilization and lower immunocompetence, and demographic changes, such as lower body growth, survival and/or reproductive performances. Our results highlight stage-dependent effects of habitat degradation on physiological traits during the breeding season: adult lizards had higher baseline corticosterone levels and yearling lizards had a lower inflammatory response than adults, whereas juveniles had higher circulating lipid levels than yearlings and adults without concomitant change in corticosterone levels. In addition, habitat degradation reduced the performances of adults but not of juveniles: in low habitat quality populations, adult males had a lower survival and females had a smaller fecundity. These results are in accordance with the allostatic load model given that allostatic load was detected only during the season and in life stages of maximal energy expenditure. This underlines the importance to account for individual energy requirements to better understand demographic responses to habitat perturbation.     

Habitat preferences as patch selection of larval and emerging chironomids (Diptera) in a gravel brook

Four common species of larval and emerging chironomids were investigated during 1981 and between 1984/1985 in an alpine gravel brook. The emergence patterns ofN. dubius, O. rivulorum andH. ornaticollis were significantly affected by fluctuations of the water level, while rises in water temperature tended to trigger the peaks in emergence of the same species and ofO. frigidus. N. dubius exhibited its main emergence activity over areas of bed sediment which had a lower mean water velocity or were discontinuously flooded. On the other hand, the imagines ofO. frigidus, O. rivulorum andH. ornaticollis reached peak densities in zones of the main current channel in the Seebach. The larvae of these species inhabited horizontally and vertically different areas of bed sediment depending on the developmental stage. Early instars ofN. dubius andH. ornaticollis preferred zones near the banks and reached their maximum densities in sediment depths of 10 to 20 cm and 20 to 30 cm, respectively. In contrast, the larvae ofO. frigidus andO. rivulorum reached their highest densities in the first 10 cm of the sediments with significant preferences for the zones of stronger water flow.     

植物生长季节不同栖息地高原鼠兔的食物选择

本文采用胃内容物镜检分析法,对栖息于青藏高原矮嵩草草甸、垂穗披碱草草甸和杂类草草甸中的高原鼠兔的主要食物组成进行了比较分析,旨在探讨栖息地变化对高原鼠兔食物组成的影响,揭示高原鼠兔对栖息地变化的生存对策和适应性.研究结果表明:在矮嵩草草甸,高原鼠兔主要取食垂穗披碱草、早熟禾、蓝花棘豆和甘肃棘豆;在垂穗披碱草草甸,主要选择垂穗披碱草、甘肃棘豆、蓝花棘豆、矮嵩草和二柱头蔗草;在杂类草草甸,喜食植物种类为垂穗披碱草、蓝花棘豆、甘肃棘豆、早熟禾、弱小火绒草、长茎藁本、兰石草和红花岩生忍冬.在整个植物生长季节,高原鼠兔在3种栖息地共取食27种植物,其中垂穗披碱草、甘肃棘豆和蓝花棘豆在不同栖息地中选择指数较高,为高原鼠兔优先选择的食物;在不同栖息地,高原鼠兔取食植物有差别,垂穗披碱草草甸为16种、矮嵩草草甸为22种,杂类草草甸为24种;喜食食物比例也存在着明显差别,在垂穗披碱草草甸,垂穗披碱草比例高达40.5%,在矮嵩草草甸,甘肃棘豆比例也达到23.7%,而在杂类草草甸,选食比例最高的兰石草仅为14.6%,说明在该草甸高原鼠兔食物选择呈现泛化趋势.相似性指数分析结果也表明,杂类草草甸中高原鼠兔主要食物组成与其它两种栖息地有较大的区别.从而说明当栖息地植物群落种类组成发生变化后,高原鼠兔可以通过改变其食物组成而适应新的栖息地.     

Osmotic and diffusive flows in single-file pores: new approach to modeling pore occupancy states

Background

The relation between osmotic permeability, P_f, diffusion permeability, P_d, and the number of water molecules, N_p, in the single-file membrane pore remains an open question. Theoretical analyses, empirical studies on aquaporins and nanotubes, and molecular dynamics simulations have yet to provide a consensus view.

Results

This paper presents a new combinatorial analysis of the different pore states formed from water molecules and the presence of a vacancy that differs from the several previous combinatorial approaches to analyzing pore states. It is the first such analysis to show that P_f / P_d?=?N_p. It is rooted in the concept of different classes of pore occupancy states, tracer states and tracer exit states, present in the pore. This includes pores with and without a single vacancy. The concepts of knock-on collisions and concerted Brownian fluctuations provide the mechanisms underlying the behaviors of the tracer and vacancy as each moves through the pore during osmotic or diffusive flow. It develops the important role of the knock-on collision mechanism for osmotic flow. An essential feature of the model is the presence, or absence, of a single vacancy in the pore. The vacancy slows down tracer translocation through the pore. Its absence facilitates osmotic flow.

Conclusions

The full pore states and the single vacancy states together with the knock-on and Brownian mechanisms account for the relative values of P_f and P_d during osmotic and diffusive flow through the single-file pore. The new approach to combinatorial analysis differs from previous approaches and is the first to show a simple intuitive basis for the relation P_f / P_d?=?N_p. This resolves a long persisting dichotomy.

     

Habitat selection by large mammals in a southern Brazilian Atlantic Forest

Habitat selection, which is mainly a consequence of competition and predation, allows species to coexist. The present study was conducted in two reserves in an Atlantic Forest area in Santa Catarina State, southern Brazil, and provided information on several large mammal species through photographic records. Records were related to certain environmental parameters, such as width of passages (trails and roads), vegetation density and proximity to water, in order to assess the relationship between each mammal species and its microhabitat. Thirty-two camera trap stations were placed during 17 months for 150.8 (±62.2) days on average. Terrestrial mammals tended to use different habitats: Puma concolor used mainly dirt roads and open areas; Leopardus pardalis, Cerdocyon thous and Nasua nasua used more large trails and intermediate-forested sites; and Cuniculus paca, Dasypus novemcinctus, Leopardus tigrinus, Eira barbara and Leopardus wiedii were recorded more often on narrow trails and in densely forested sites. Some of these forest species, such as D. novemcinctus, C. paca and L. pardalis, also showed relationships with watercourses. Information on habitat selection allows more effort to be addressed to the habitat associated with focal species, and indicates the significance of environmental heterogeneity, which makes it possible for species to coexist.     

Effects of abiotic factors on movements of pikeperch during pre-spawning and spawning season in a Baltic archipelago

The effects of temperature, water level and moon phase on the movements of pikeperch (Sander lucioperca) were studied during pre-spawning and spawning season from April to June. Trends in catches and temperature were removed with linear regression. Cross-correlation analysis showed that temperature change one and two days earlier had the strongest effect on catches. Close to the new moon, pikeperch catches increased, whereas changes in water level had no effects on movements. Handling editor: J. A. Cambray     

The relative contribution of local habitat and landscape context to metapopulation processes: a dynamic occupancy modeling approach

Changes in site occupancy across habitat patches have often been attributed to landscape features in fragmented systems, particularly when considering metapopulations. However, failure to include habitat quality of individual patches can mask the relative importance of local scale features in determining distributional changes. We employed dynamic occupancy modeling to compare the strength of local habitat variables and metrics of landscape patterns as drivers of metapopulation dynamics for a vulnerable, high‐elevation species in a naturally fragmented landscape. Repeat surveys of Bicknell's thrush Catharus bicknelli presence/non‐detection were conducted at 88 sites across Vermont, USA in 2006 and 2007. We used an organism‐based approach, such that at each site we measured important local‐scale habitat characteristics and quantified landscape‐scale features using a predictive habitat model for this species. We performed a principal component analysis on both the local and landscape features to reduce dimensionality. We estimated site occupancy, colonization, and extinction probabilities while accounting for imperfect detection. Univariate, additive, and interaction models of local habitat and landscape context were ranked using AICc scores. Both local and landscape scales were important in determining changes in occupancy patterns. An interaction between scales was detected for occupancy dynamics indicating that the relationship of the parameters to local‐scale habitat conditions can change depending on the landscape context and vice versa. An increase in both landscape‐ and local‐scale habitat quality increased occupancy and colonization probability while decreasing extinction risk. Colonization and extinction were both more strongly influenced by local habitat quality relative to landscape patterns. We also identified clear, qualitative thresholds for landscape‐scale features. Conservation of large habitat patches in high‐cover landscapes will help ensure persistence of Bicknell's thrushes, but only if local scale habitat quality is maintained. Our results highlight the importance of incorporating information beyond landscape characteristics when investigating patch occupancy patterns in metapopulations.     

The role of behavioral dominance in structuring patterns of habitat occupancy in a migrant bird during the nonbreeding season

Several species of territorial migratory birds exhibit sexualhabitat segregation on their wintering grounds, with some habitatscontaining mostly males and others mostly females. The objectiveof this study was to determine if in the American redstart(Setophaga ruticilla) in Jamaica habitat segregation is dueto social mechanisms or due to sex-specific habitat specialization.I used habitat-specific patterns of arrival by young males and females, observations of territorial displacements, removalexperiments, and simulations of territorial intrusions to differentiatebetween these two mechanisms. Redstarts were studied in twohabitat types, a male-biased mangrove forest and a female-biasedscrub habitat. In autumn, male and female hatch-year redstartsinitially settled in equal numbers in each habitat, and segregationof the sexes occurred gradually and mostly later in the arrival period. This shift corresponded with an increase in densityof older birds and an increase in territorial displacements.Removal experiments showed that vacancies in male-biased habitatwere filled more rapidly and with greater frequency than thosein female-biased habitat and that vacated male territoriesin mangrove were replaced more often by females than by males. Simulations of territorial intrusions and analyses of body sizeindicated that levels of aggression and body size of both malesand females were greater in mangrove habitat, suggesting thatthese factors may be important in determining the outcomesof dominance interactions. I conclude that patterns of sexualhabitat segregation in redstarts are structured by the dominance behavior of older and more dominant individuals, and these aremostly males.