Individual Habitat Use Research Articles

Spatiotemporal patterns in habitat use of natal and non-natal adult Atlantic sturgeon in two spawning rivers

BackgroundMonitoring movement across an organism’s ontogeny is often challenging, particularly for long-lived or wide-ranging species. When empirical data are unavailable, general knowledge about species’ ecology may be used to make assumptions about habitat use across space or time. However, inferences about habitat use based on population-level ecology may overlook important eco-evolutionary contributions from individuals with heterogenous ethologies and could diminish the efficacy of conservation and management.MethodsWe analyzed over a decade of acoustic telemetry data to understand individual differences in habitat use of federally endangered adult Atlantic sturgeon (Acipenser o. oxyrinchus) in the Delaware and Hudson rivers during spawning season. In particular, we sought to understand whether sex or natal origin could predict patterns in habitat use, as there is a long-held assumption that adult Atlantic sturgeon seldom stray into non-natal rivers.ResultsIn both rivers, migration timing, spawning habitat occupancy, and maximum upstream migration distance were similar between natal and non-natal individuals. While non-natal individuals represented only 13% of fish detected in the Hudson River, nearly half of all tagged fish detected in the Delaware River were non-natal and generally occupied freshwater habitats longer than natal individuals. In both systems males had more heterogenous patterns of habitat use and longer duration of occupancy than did females.ConclusionsThis study demonstrates the importance of non-natal rivers for fulfilling ontogenetic habitat requirements in Atlantic sturgeon. Our results may also highlight an opportunity to improve conservation and management by extending habitat designations to account for more heterogenous patterns in individual habitat use in non-natal freshwater environments.

Monitoring the movement, habitat use and mortality of captive‐bred reintroduced gharials in the Mahanadi River, India

Abstract Gharials (Gavialis gangeticus) are endemic to the Indian subcontinent and meet IUCN Red List criteria for critically endangered. The Mahanadi River, located in the southernmost part of the gharial range, currently has a few individuals survived although historically had many more. Between 2019 and 2021, the movement, habitat use and survival rate of 13 captive‐bred (juvenile = 6, subadult = 5, adult = 2) reintroduced gharials were monitored using very high frequency (VHF) radio transmitters tracked manually from the river banks. Kernel density estimates and generalized linear model (GLM) were used to investigate the home range and habitat use of individuals. Tagged gharials travelled throughout the river system, with the highest movement during summer and the least in winter. Females moved further and established larger linear home ranges than males. Kernel home ranges were established in and around the Satkosia Gorge wildlife sanctuary, which has favourable ecological conditions for gharials, namely, deep water, sandbars, abundant fish and low human disturbance. Gharial mortality was detected during the study, and post‐mortem examination indicated anthropogenic causes. The use of explosives for fishing, entanglement in fishing nets and a lack of ecological awareness within local communities were identified as key factors that need to be addressed if gharials are to survive the Mahanadi River.

Evaluating translocation success of wild eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) in Blue Ridge Ecoregion streams using pre- and post-translocation home range sizes and movement metrics.

Translocations of freshwater species have become a widespread conservation strategy to mitigate the impacts of habitat fragmentation, yet they are not often rigorously monitored using animal movement data to determine their success. We demonstrate the value of monitoring pre- and post-translocation movements and home-range sizes of a fully-aquatic, benthic stream salamander, the eastern hellbender (Cryptobranchus a. alleganiensis) to determine translocation success. We studied the home range sizes, movements, and habitat use of individuals (n = 27) in two self-sustaining populations (S1 & S2) for one year, and then subsequently collected similar data from a subset of these individuals (n = 17) that were translocated into two nearby streams (T1 & T2) with dam-isolated, declining populations in the Blue Ridge Ecoregion of Tennessee. We collected 1,571 location data points (869 pre-translocation and 715 post-translocation) from four study sites, and evaluated effects of mass, sex, and pre-translocation home range size/sedentariness, as well as habitat covariates on home range size and movements. Hellbender home range sizes increased from pre-translocation estimates at both sites, but response depended primarily on physical characteristics of release sites. Home range and fine-scale movement metrics indicated that hellbenders translocated from S1 to T1 settled in more quickly, had greater site fidelity, and smaller home ranges than hellbenders translocated from S2 to T2. Hellbender movements were influenced by cover rock size and density rather than individual characteristics. Study-long survival rates of translocated hellbenders increased from S1 to T1 (80% to 100%) and decreased from S2 to T2 (76% to 33%). Monitoring pre- and post-translocation movements was a valuable method for evaluating short-term translocation success in a freshwater environment. For future hellbender translocations, managers should prioritize selecting suitable release sites with contiguous boulder-dense areas (1-2 per m2), adequate prey (crayfish) densities (>1/m2), and habitats with low risk of predation.

Space use and site fidelity in the endangered Northern Bald Ibis Geronticus eremita: Effects of age, season, and sex

Summary Understanding space use of endangered species is critical for conservation planning and management. The advances in technology and data analysis allow us to collect data with unprecedented quality and inform us about the movements and habitat use of individuals and groups. With only about 700 individuals left in the wild, the Northern Bald Ibis Geronticus eremita is currently categorised as ‘Endangered’. However, little is known about the movements of this avian species in relation to breeding and individual differences. Using GPS transmitters we studied the movements of 32 Northern Bald Ibis from a semi-wild free-flying colony at the Konrad Lorenz Research Center in Austria during 1–4 years per individual. We investigated how sex, age class, breeding and non-breeding season affect space use and site fidelity. We found that individuals consistently showed high site fidelity, adults more than juveniles, and space use was highly overlapping between individuals and over successive years. When moving between different areas birds used consistent flyways thereby avoiding direct routes over mountainous areas. Adults had more expansive space use during the breeding season as compared to the non-breeding season, while juveniles only showed a slight decrease during the non-breeding season. We found no sex differences regarding space use or site fidelity. Our results lead to a better understanding of how Northern Bald Ibis move through their environment and how they use foraging areas, roosting sites, and space in general that in turn can help to inform conservation management of extant colonies and reintroduction programmes for new colonies.

The important role of animal social status in vertebrate seed dispersal.

Seed dispersal directly affects plant establishment, gene flow and fitness. Understanding patterns in seed dispersal is, therefore, fundamental to understanding plant ecology and evolution, as well as addressing challenges of extinction and global change. Our ability to understand dispersal is limited because seeds may be dispersed by multiple agents, and the effectiveness of these agents can be highly variable both among and within species. We provide a novel framework that links seed dispersal to animal social status, a key component of behaviour. Because social status affects individual resource access and movement, it provides a critical link to two factors that determine seed dispersal: the quantity of seeds dispersed and the spatial patterns of dispersal. Social status may have unappreciated effects on post-dispersal seed survival and recruitment when social status affects individual habitat use. Hence, environmental changes, such as selective harvesting and urbanisation, that affect animal social structure may have unappreciated consequences for seed dispersal. This framework highlights these exciting new hypotheses linking environmental change, social structure and seed dispersal. By outlining experimental approaches to test these hypotheses, we hope to facilitate studies across a wide diversity of plant-animal networks, which may uncover emerging hotspots or significant declines in seed dispersal.

Whisker growth in Tasmanian devils (Sarcophilus harrisii) and applications for stable isotope studies

AbstractIndividual longitudinal records of diet, movement, and physiological state of endangered Tasmanian devils (Sarcophilus harrisii) are needed for effective management of wild populations, yet most traditional techniques are expensive or labor‐intensive. Stable isotope analysis of inert tissue, such as vibrissae (whiskers), provides a viable and minimally invasive solution to chronologically record the foraging ecology and habitat use of individuals. Species‐specific information on whisker growth (i.e., time‐position growth of isotopic signatures), retention time, and arrangement on the face is required before the implementation of stable isotope analysis in wild populations. Here, whiskers of six captive Tasmanian devils were internally marked with 13C‐ and 15N‐labeled glycine at three‐month intervals followed by isotopic analysis of the longest whisker to provide a time stamp for whisker growth and estimate retention time. Intradermal and extradermal lengths of wild Tasmanian devil whiskers were used to assess the arrangement and relative length of whiskers on the face. We found that whiskers can record at least nine months of an animal's ecological history and that whisker growth is not linear, the growth gradually slows down as the whisker lengthens. Our findings demonstrate that sequentially sampled whiskers have the potential to track monthly and seasonal isotopic changes of an individual animal in the wild, both within its historical range and in areas to which it has recently been introduced. Such information can be used to identify temporal shifts in habitat and prey preferences within populations and help select suitable individuals for translocations. We recommend that the longest mystacial whiskers, positioned posteriorly at the third and fourth row, should be preferentially used for stable isotope studies in this species. The timeframe represented by the root of the whisker (˜3–63 d) can be used to adjust the base of cut whiskers to the correct time period.

Linking morbillivirus exposure to individual habitat use of common bottlenose dolphins (Tursiops truncatus) between geographically different sites.

Dolphin morbillivirus (DMV) is a virulent pathogen that causes high mortality outbreaks in delphinids globally and is spread via contact among individuals. Broadly ranging nearshore and open-ocean delphinids are likely reservoir populations that transmit DMV to estuarine populations. We assessed the seroprevalence of DMV antibodies and determined the habitat use of common bottlenose dolphins, Tursiops truncatus truncatus, from two estuarine sites, Barataria Bay and Mississippi Sound, in the northern Gulf of Mexico. We predicted that risk to DMV exposure in estuarine dolphins is driven by spatial overlap in habitat use with reservoir populations. Serum was collected from live-captured dolphins and tested for DMV antibodies. Habitat use of sampled individuals was determined by analysing satellite-tracked movements and stable isotope values. DMV seroprevalences were high among dolphins at Barataria Bay (37%) and Mississippi Sound (44%), but varied differently within sites. Ranging patterns of Barataria Bay dolphins were categorized into two groups: Interior and Island-associated. DMV seroprevalences were absent in Interior dolphins (0%) but high in Island-associated dolphins (45%). Ranging patterns of Mississippi Sound dolphins were categorized into three groups: Interior, Island-east and Island-west. DMV seroprevalences were detected across Mississippi Sound (Interior: 60%; Island-east: 20%; and Island-west: 43%). At both sites, dolphins in habitats with greater marine influence had enriched δ13 C values, and Barataria Bay dolphins with positive DMV titres had carbon isotope values indicative of marine habitats. Positive titres for DMV antibodies were more common in the lower versus upper parts of Barataria Bay but evenly distributed across Mississippi Sound. A dolphin's risk of exposure to DMV is influenced by how individual ranging patterns interact with environmental geography. Barataria Bay's partially enclosed geography likely limits the nearshore or open-ocean delphinids that carry DMV from interacting with dolphins that use interior, estuarine habitats, decreasing their exposure to DMV. Mississippi Sound's relatively open geography allows for greater spatial overlap and mixing among estuarine, nearshore and/or open-ocean cetaceans. The spread of DMV, and likely other diseases, is affected by the combination of individual movements, habitat use and the environment.

An African urban mesocarnivore: Navigating the urban matrix of Durban, South Africa

Urbanisation is rapidly transforming natural habitats with the potential to benefit synanthropic species, especially mesocarnivore species. Knowledge of the spatio-temporal ecology of mongoose species in an urban matrix is limited. Consequently, we examined the home range and habitat use of water mongoose (Atilax paludinosus, n = 14) in an urban matrix landscape. Mongooses were collared and radio-tracked using Global Positioning System (GPS)-Ultra high frequency (UHF) transmitters between July 2018 and October 2019 in the Upper Highway area’s urban matrix, eThekwini Municipality, Durban, KwaZulu-Natal, South Africa. Habitat selection for water mongoose indicated that the species avoided built-up urban areas favouring fragments of forest and bushland habitat types close to natural water sources within the urban mosaic. The adaptability and generalist nature of water mongoose has facilitated their persistence in the urban mosaic. Variability in the home range size and habitat use of individuals of the water mongooses highlights their ability to adapt to anthropogenically modified landscape, yet they were highly dependent on natural refugia in this urban matrix.

Humans shape the year-round distribution and habitat use of an opportunistic scavenger.

Research focused on evaluating how human food subsidies influence the foraging ecology of scavenger species is scarce but essential for elucidating their role in shaping behavioral patterns, population dynamics, and potential impacts on ecosystems. We evaluate the potential role of humans in shaping the year‐round distribution and habitat use of individuals from a typical scavenger species, the yellow‐legged gull (Larus michahellis), breeding at southwestern Spain. To do this, we combined long‐term, nearly continuous GPS‐tracking data with spatially explicit information on habitat types and distribution of human facilities, as proxied by satellite imagery of artificial night lights. Overall, individuals were mainly associated with freshwater habitats (mean proportion, 95% CI: 40.6%, 36.9%–44.4%) followed by the marine‐related systems (40.3, 37.7%–42.8%), human‐related habitats (13.5%, 13.2%–13.8%), and terrestrial systems (5.5%, 4.6%–6.5%). However, these relative contributions to the overall habitat usage largely changed throughout the annual cycle as a likely response to ecological/physiological constraints imposed by varying energy budgets and environmental constraints resulting from fluctuations in the availability of food resources. Moreover, the tight overlap between the year‐round spatial distribution of gulls and that of human facilities suggested that the different resources individuals relied on were likely of anthropogenic origin. We therefore provide evidence supporting the high dependence of this species on human‐related food resources throughout the annual cycle. Owing to the ability of individuals to disperse and reach transboundary areas of Spain, Portugal, or Morocco, international joint efforts aimed at restricting the availability of human food resources would be required to manage this overabundant species and the associated consequences for biodiversity conservation (e.g., competitive exclusion of co‐occurring species) and human interests (e.g., airports or disease transmission).

Use of otolith chemistry to assess recruitment and habitat use of a white bass fishery in a Nebraska reservoir

Perrion MA, Kaemingk MA, Koupal KD, Schoenebeck CW, Bickford NA. 2019. Use of otolith chemistry to assess recruitment and habitat use of a white bass fishery in a Nebraska reservoir. Lake Reserv Manage. 36:64–74.Managing fisheries that exhibit variable annual recruitment is challenging, and maintenance stockings are often prescribed to minimize interannual population variation. Maintenance stockings are costly and may not be necessary if sufficient natural recruitment is occurring. Therefore, developing tools and techniques that can collectively assess hatching origin and subsequent habitat use of individuals would be valuable. Herein, we aimed to assess the efficacy of otolith chemistry techniques to (1) determine whether there was evidence of natural recruitment within an annually stocked white bass population and (2) examine the potential to describe spatial reservoir use of these age-0 fish. A sample of hatchery-produced fingerling white bass (n = 17) was retained from a larger June 2015 stocking of white bass in Lake McConaughy, Nebraska, to characterize the hatchery fish natal elemental signatures. Age-0 white bass (n = 100) were then collected in Lake McConaughy in September 2015 from 2 sections of the reservoir (upper and main) to assess both natal origin (hatchery versus natural) and habitat use (upper versus main) using otolith concentrations of 5 chemical constituents at the otolith core and otolith edge, respectively. Otolith core signatures from the fall age-0 Lake McConaughy collected fish were different from the hatchery fish, indicating evidence for natural white bass recruitment. Otolith edge signatures were also distinct between fish collected from the upper and main sections of the reservoir. Otolith chemistry techniques can be useful for addressing challenges associated with managing erratic recruiting fish populations that are common to lake and reservoir systems.

Individual habitat use and behavior of acoustically-tagged juvenile green sturgeon in the Sacramento-San Joaquin Delta

Southern distinct population segment (sDPS) juvenile Green Sturgeon are thought to rear in the Sacramento-San Joaquin Delta for two to four years. The southern population segment has been listed as “threatened” under the Endangered Species Act. Habitat loss is cited as a significant driver in declines of the population. Specific to juvenile rearing, much of the historic floodplain habitat has been lost and replaced by leveed channelized waterways. In addition to geomorphic alterations, other direct and indirect activities such as water export, dredging, and the introduction of invasive species may have significant impacts to the viability of the species. The objective of this tracking study was to provide a first of its kind look at the movements and behaviors of wild caught juvenile Green Sturgeon within the putative nursery grounds of the Sacramento-San Joaquin Delta. We acoustically tagged and continuously tracked six yearling juvenile Green Sturgeon with mean total length (TL) of 50.6 cm (SD = 5.3) and mean mass of 563.3 g (SD = 151.7). We performed continuous mobile tracking for a period of up to five days per individual while recording GPS coordinates, depths, and water temperature at the sturgeon’s location. We used first-passage times, defined as the amount of time spent within a given area, for which a radius was determined post hoc. First passage times were used as a metric for parsing bouts of localized movements from directed movements. Our results indicate that juvenile Green Sturgeon largely oriented at or near the bottom. Depths utilized by all sturgeon ranged from >3 m to 20 m across all tracks. Individuals exhibited fidelity to the San Joaquin River Channel with only one individual leaving the main channel. Juvenile green sturgeon were shown to exhibit both positive and negative rheotaxis during sustained directed movements under independent ebb tidal cycles. This study provides the first detailed examination into the early life movements and behaviors of a rare species within their putative nursery grounds.

Boldness-mediated habitat use tactics and reproductive success in a wild large herbivore

The balance between resource acquisition and risk avoidance should vary according to personality type, with potential knock-on effects for fitness. Although previous studies have suggested a link between boldness and fitness components, little evidence is available on the behavioural mechanisms mediating this relationship in the wild. Because habitat use is the outcome of the trade-off between the costs and benefits associated with using each habitat type, we evaluated between-individual differences in habitat use of 64 GPS-collared female roe deer, Capreolus capreolus, using multinomial logit mixed models. To investigate whether deer differed in their habitat use tactics in relation to their personality type and their annual reproductive success, we assessed the link between individual habitat use patterns, boldness (measured as the strength of behavioural responsiveness to handling) and annual reproductive success (measured by the presence/absence of fawns at heel during autumn). Although daily and seasonal variations in the risk–resource landscapes clearly drove patterns of habitat use, individuals adopted contrasting habitat use tactics depending on their position along the shy–bold gradient and their reproductive status. Shy individuals occupied safer woodland more frequently, even at night when risk is lower. In contrast, bold individuals were better able to exploit rich open habitats. When this included mature autumn crops, these females weaned more offspring. Finally, irrespective of personality type, females that used meadows more often also achieved higher annual reproductive success. Overall, we demonstrate that individuals express divergent habitat use tactics as a function of their ability to avoid exposure to risk and their annual reproductive success.

Spatial conservation of large mobile elasmobranchs requires an understanding of spatio-temporal seascape utilization

The positioning of habitats interacts with variability in abiotic factors (e.g. seasonal changes in temperature and extreme weather events) to change how animals use a land or seascape. Marine reserves can regulate how human activities alter fish communities and increase the abundance of targeted species, but the combined influence of reserves and seascape context on species habitat use remains uncertain in many ecosystems. Further, marine reserve effectiveness might be low for mobile species if the size of the reserve is less than a species usual range, reducing the overall time a individual may be protected. In this study, we tracked 19 giant shovelnose rays (Glaucostegus typus), an IUCN listed vulnerable species within the Moreton Bay Marine Park in eastern Australia. We used an array of 28 acoustic receivers within a complex mosaic of seagrass patches, bare sand, mangrove forests and deep-water channels and used regression tree analyses to determine which spatial, temporal and protection factors contributed most to G. typus habitat use. Overall, 50% of the total detections in the study occurred inside marine reserves containing large seagrass beds (>7.09 m2) and in close proximity to mangroves ( 20.2 °C), the habitat use of individuals is contained in smaller centres of activity compared with winter, however, protection effects varied. Our results show that seascape context and marine reserves combine to provide the optimal areas for G. typus habitat selection. Limited food resources likely caused larger centres of activity during winter. Identifying priority habitats for vulnerable species is critical for ongoing protection and maintaining effective conservation initiatives. We have shown here that incorporating spatial features into the design of marine reserves can improve conservation outcomes for mobile benthic predators such as G. typus and other species that use such seascapes.

Individual specialization and behavioral plasticity in a long-lived marine predator

Individual specialization in vertebrates is often related to morphological variability, but can also reflect a diversity of trajectories during the learning sensitive period in early life. In both cases the capacity of adults to adapt to new environments can be limited if further morphological or behavioral change is not possible. Adult loggerhead turtles Caretta caretta (Linnaeus, 1758) from Cape Verde (NW Africa) may forage in the open ocean or on the continental shelf. Oceanic foragers prevail in the population, but neritic foragers grow larger, have a higher reproductive output and produce best fitted offspring. Previous research suggests that the high prevalence of oceanic foragers is because the migratory routes followed by juvenile turtles during their early life results into a low probability of settlement on the African shelf. The stable isotope ratios of C and N in 60μm carapace layers from 14 adult females have been analyzed to reconstruct retrospectively their individual habitat use patterns and test the hypothesis that adult loggerhead turtles remain faithful to their foraging grounds even if sub-optimal. Only two turtles exhibited clear oceanic—neritic shifts, approximately 22 and 15years before sampling. The remaining turtles had foraged in neritic (3) or oceanic (9) habitat as long as recorded in the carapace scutes (approximately 8–37years), despite the smaller body size and the lower reproductive output associated to oceanic foraging. These results suggest that habitat shifts during adulthood are unlikely in this species and support the hypothesis that only during the juvenile stage loggerhead turtles are flexible enough to adapt to contrasting environments.

Spring habitat use by stocked one year old European sturgeon Acipenser sturio in the freshwater-oligohaline area of the Gironde estuary

Post release habitat selection was studied on forty eight 10-month-old hatchery reared European sturgeon (mean fork length 31.0 cm ± 3.0) in the tidal part of their native catchment using acoustic telemetry. Most of the fish reached the oligohaline estuary within 2–4 days (70 km downstream the release site). Seventy four percent of the fish migrated rapidly downstream of the estuary into mesohaline waters while 26% selected habitat in the freshwater/oligohaline part of the estuary based on their linearity and residency indices. We focused on individual habitat use of these fish. The home range size (HR) was calculated using two methods: the kernel utilization distribution (KUD) which is driven by the maximum detection location density, and the Brownian Bridge (BB) approach which allows the time component of the trajectory path to be taken into account. The average 50% HR KUD was 5.6 ± 2.7 km2 (range 1.1–10.3 km2) and it was estimated to be 6 times larger using the 50% HR BB method (average reaching 31.9 ± 20.7 km2, range 5.2–77.8 km2). Habitat characterization (available prey, substrate and depth) in the studied area was described and the Ivlev electivity index was calculated using the habitat within the 50% HR BB for each individual. Despite the spatial use of different core areas among the fish tagged, we observed a convergence in habitat preference. For substrates, sturgeons showed avoidance of gravel and large rocks as well as fine and medium gravel. There was a significant preference for sand, silts and clay. For depth, they exhibited a preference firstly for the 5–8 m depth range and secondly for the 2–5 m range, a strong avoidance of depth range 8–20 m and a slight avoidance of shallow (0–2 m) and intertidal areas. For prey, individual variability was high. The most homogenous results were found for annelid polychaeta, with a slight preference for areas with this group of preys which are abundant in the saline estuary. For some individuals, a preference for areas with crustacea or nematodea and avoidance for areas with mollusks, insects or oligochaeta occured. We explain our results in light of foraging behavior and adaptation to the wild environment after captivity.For sturgeon population restoration projects in western Europe, these habitat preferences are key-features needed to evaluate the essential habitat availability for A. sturio juveniles in the tidal area at the front of the freshwater/saline transition waters.

Linking otolith microchemistry and dendritic isoscapes to map heterogeneous production of fish across river basins.

Production patterns of highly mobile species, such as anadromous fish, often exhibit high spatial and temporal heterogeneity across landscapes. Such variability is often asynchronous in time among habitats, which stabilizes production at aggregate scales of complexity. Reconstructing production patterns explicitly in space and time across multiple scales, however, remains difficult but is important for prioritizing habitat conservation. This is especially true for fishes inhabiting river basins due to long-range dispersal, high mortality at early life stages, complex population structure and elusive life history variation. We develop a new approach for mapping production patterns of Pacific salmon across a large river basin by integrating otolith microchemistry and dendritic isoscape models. The geographically continuous Bayesian assignment framework presented here yielded high accuracies (>90%) and relatively high precisions (precisions <4%; i.e., assignment areas of <530 river km of the 13 100km total river length) when used to determine the natal source of known-origin juvenile Chinook salmon captured throughout the study region. Integrating these methods enabled us to base estimates of provenance and habitat use of individuals on a per location basis using strontium isotopic data throughout the continuous spatial domain of a river network. Such a framework provides substantial advantages over the more common nominal approach to employing otolith microchemistry to reconstruct movement patterns of fish. In doing so, we reconstructed the spatial production patterns of adult Chinook salmon returning to a large watershed in Bristol Bay, Alaska and illustrate the power of such an approach to conservation efforts.

Pup Vibrissae Stable Isotopes Reveal Geographic Differences in Adult Female Southern Sea Lion Habitat Use during Gestation.

Individuals within populations often differ substantially in habitat use, the ecological consequences of which can be far reaching. Stable isotope analysis provides a convenient and often cost effective means of indirectly assessing the habitat use of individuals that can yield valuable insights into the spatiotemporal distribution of foraging specialisations within a population. Here we use the stable isotope ratios of southern sea lion (Otaria flavescens) pup vibrissae at the Falkland Islands, in the South Atlantic, as a proxy for adult female habitat use during gestation. A previous study found that adult females from one breeding colony (Big Shag Island) foraged in two discrete habitats, inshore (coastal) or offshore (outer Patagonian Shelf). However, as this species breeds at over 70 sites around the Falkland Islands, it is unclear if this pattern is representative of the Falkland Islands as a whole. In order to characterize habitat use, we therefore assayed carbon (δ13C) and nitrogen (δ15N) ratios from 65 southern sea lion pup vibrissae, sampled across 19 breeding colonies at the Falkland Islands. Model-based clustering of pup isotope ratios identified three distinct clusters, representing adult females that foraged inshore, offshore, and a cluster best described as intermediate. A significant difference was found in the use of inshore and offshore habitats between West and East Falkland and between the two colonies with the largest sample sizes, both of which are located in East Falkland. However, habitat use was unrelated to the proximity of breeding colonies to the Patagonian Shelf, a region associated with enhanced biological productivity. Our study thus points towards other factors, such as local oceanography and its influence on resource distribution, playing a prominent role in inshore and offshore habitat use.

Habitat use by Black Grouse Tetrao tetrix in a mixed moorland-forest landscape in Scotland and implications for a national afforestation strategy

Capsule Long-term conservation of Black Grouse in Scotland may rely upon the retention of sufficiently large and well-connected patches of moorland and a diversity of adjacent forest types.Aims To study Black Grouse habitat use within a moorland-forest mosaic and make recommendations for their conservation in more heavily forested future landscapes.Methods We carried out radio-telemetry on Black Grouse over three years to investigate individual habitat use. We used compositional analyses to investigate habitat selection in different seasons. We examined whether this matched previous population-level patterns and whether it differed between males and females. We used logistic regression to examine whether movements into large-scale commercial forests were restricted to the periphery relative to random locations.Results Males used seasonal ranges of >200 ha and females >70 ha. Birds selected strongly for moorland throughout the year, matching other population-level studies. Underlying this, however, males and females differed in their use of forests, with males associated with broadleaf woodland, while females preferred new native pinewoods in spring–summer or commercial conifer forests in autumn–winter. Use of commercial plantation forests was generally limited to their periphery, particularly to within <300 m of the forest edge.Conclusion When planning afforestation, moorland patches of at least 200 ha must be retained and their fragmentation should be minimized, particularly as young forests may provide breeding habitat over a limited duration. However, mature forests also form an important habitat component and, at a local scale, both coniferous and broadleaf forests should be made available to provide resources for both sexes. Some management decisions will therefore need to be made at the landscape-scale to balance broad national targets of afforestation with individual landowner/contractor decisions.

Spatial overlap, proximity, and habitat use of individual wolves within the same packs

ABSTRACTPacks are the basic social and breeding groups of wolf (Canisspp.) populations and are often the sampling unit for wolf research. Researchers commonly assume, either explicitly or implicitly, that telemetry data from ≥1 individual wolf can be used to represent the space use, distribution, presence, and resource selection of the pack. We tested these critical assumptions using Global Positioning System telemetry by directly comparing home range size, probability of spatial overlap, seasonal proximity, and habitat use of individuals within wolf packs in central and northern Ontario, Canada, 2006–2010. Space use was similar and probability of overlap was high for wolves within packs for individual 95% home‐range contours. Variation was greater for 50% contours, indicating that individual wolves may use space differently within territories. Wolves within packs spent more time &lt;100 m and &lt;1 km from each other during winter ( = 66 and 75%, respectively) than during other seasons ( = 33 and 40%, respectively) supporting earlier findings that pack cohesion was highest during winter. Individuals within all packs exhibited differences in the use of specific resource variables when separated by &gt;100 m. Use of habitat variables was more similar when we compared resource selection of individuals within packs using all locations (regardless of proximity), although we still detected differences within most packs. Our results suggest that telemetry data from individual wolves can be used to reliably estimate territories for packs, but that researchers should be cautious when making pack‐level inferences regarding finer scale space and habitat use within home ranges based on data from individual animals. © 2014 The Wildlife Society.

The relationship between individual habitat use and diet in brown trout

SummarySalmonids exhibit considerable variation within and between individuals in growth, diet, foraging strategy and habitat use, but little is known about how these characteristics covary. Previous work has shown that habitat use strongly influences growth rates in brown trout (Salmo trutta).We examined individual variation in diet of PIT‐taggedSalmo truttain three stream enclosures in relation to individual habitat use, size, sex and growth. Each enclosure consisted of a fine substratum pool and a coarse substratum riffle. By placing antennae between these habitats, we continuously monitored habitat use under field conditions. Fish were recaptured four times over the 2‐month study period, and diet, which was examined through stomach flushing, was related to habitat use over the previous 48 h. Individual fish growth was also measured.Based on habitat use, trout were classified as either movers or stayers, with stayers being of two types, those using only pools and those using only riffles and movers using and swimming between pools and riffles. The stayers in pools took more terrestrial prey than the stayers in riffles, whereas the latter fed more on aquatic invertebrates such as the crustaceanGammarus pulex,the plecopteranLeuctraand cased caddis larvae. Movers had diets intermediate between the stayers in pools and the stayers in riffles.Results of canonical correspondence analysis showed that variation in diet amongst individual fish over the study period was significantly influenced by enclosure, growth and % time spent in the pool during the day. Graphical models of diet analysis showed that population and mean individual prey diversity tended to differ amongst enclosures and suggested that stayers in pools consumed a greater prey diversity, whereas stayers in riffles consumed more prey. Discriminant analysis of diets revealed significant discrimination by habitat and sex on two of the four sampling occasions, based on daytime habitat use, but only on one date based on night‐time habitat use. Stoneflies and terrestrial prey contributed most to the separation.