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At least 145 records · Page 8Linked to original sources

USGS2011

Lipid catabolism of invertebrate predator indicates widespread wetland ecosystem degradation

Animals frequently undergo periods when they accumulate lipid reserves for subsequent energetically expensive activities, such as migration or breeding. During such periods, daily lipid-reserve dynamics (DLD) of sentinel species can quantify how landscape modifications affect function, health, and resilience of ecosystems. Aythya affinis (Eyton 1838; lesser scaup; diving duck) are macroinvertebrate predators; they migrate through an agriculturally dominated landscape in spring where they select wetlands with the greatest food density to refuel and accumulate lipid reserves for subsequent reproduction. We index DLD by measuring plasma-lipid metabolites of female scaup (n = 459) that were refueling at 75 spring migration stopover areas distributed across the upper Midwest, USA. We also indexed DLD for females (n = 44) refueling on a riverine site (Pool 19) south of our upper Midwest study area. We found that mean DLD estimates were significantly (P<0.05) less than zero in all ecophysiographic regions of the upper Midwest, and the greatest negative value was in the Iowa Prairie Pothole region (-31.6). Mean DLD was 16.8 at Pool 19 and was markedly greater than in any region of the upper Midwest. Our results indicate that females catabolized rather than stored lipid reserves throughout the upper Midwest. Moreover, levels of lipid catabolism are alarming, because scaup use the best quality wetlands available within a given stopover area. Accordingly, these results provide evidence of wetland ecosystem degradation across this large agricultural landscape and document affects that are carried-up through several trophic levels. Interestingly, storing of lipids by scaup at Pool 19 likely reflects similar ecosystem perturbations as observed in the upper Midwest because wetland drainage and agricultural runoff nutrifies the riverine habitat that scaup use at Pool 19. Finally, our results underscore how using this novel technique to monitor DLD, of a carefully selected sentinel species, can index ecosystem health at a landscape scale.

PLoS ONE↗

USGS2012

The early bird gets the shrimp: Confronting assumptions of isotopic equilibrium and homogeneity in a wild bird population

1. Because stable isotope distributions in organic material vary systematically across energy gradients that exist in ecosystems, community and population structures, and in individual physiological systems, isotope values in animal tissues have helped address a broad range of questions in animal ecology. It follows that every tissue sample provides an isotopic profile that can be used to study dietary or movement histories of individual animals. Interpretations of these profiles depend on the assumption that metabolic pools are isotopically well mixed and in equilibrium with dietary resources prior to tissue synthesis, and they extend to the population level by assuming isotope profiles are identically distributed for animals using the same proximal dietary resource. As these assumptions are never fully met, studying structure in the variance of tissue isotope values from wild populations is informative. 2. We studied variation in δ 13 C, δ 15 N, δ 2 H and δ 18 O data for feathers from a population of eared grebes (Podiceps nigricollis) that migrate to Great Salt Lake each fall to moult feathers. During this time, they cannot fly and feed almost exclusively on superabundant brine shrimp (Artemia franciscana). The ecological simplicity of this situation minimized the usual spatial and trophic complexities often present in natural studies of feather isotope values. 3. Ranges and variances of isotope values for the feathers were larger than those from previously published studies that report feather isotopic variance, but they were bimodally distributed in all isotope dimensions. Isotope values for proximal dietary resources and local surface water show that some of the feathers we assumed to have been grown locally must have been grown before birds reached isotopic equilibrium with local diet or immediately prior to arrival at Great Salt Lake. 4. Our study provides novel insights about resource use strategies in eared grebes during migration. More generally, it demonstrates the utility of studying variance structures and questioning assumptions implicit in the interpretation of stable isotope data from wild animals.

Utah↗

USGS2026

Predicting disease spread from host movement data: Chronic wasting disease in North America as a case study

1. Rare long-distance movements can increase the spatial spread of invasive species and shifts in species ranges. However, in the context of wildlife disease spread, seasonal migrations only matter if they lead to transmission beyond an individual’s initial set of contacts, and the importance of juvenile dispersal depends on whether those juveniles become infected before they disperse. 2. High resolution animal movement data are increasing, but it is unclear how to leverage these data to improve predictions future disease spread particularly in regions without pre-existing movement data. 3. We predicted the speed of chronic wasting disease (CWD) spread based on movement metrics of mule deer ( Odocoileus hemionus ) and white-tailed deer ( Odocoileus virginianus ) and compared our predictions to observed spreading rates in North America from 2005 to 2022. We hypothesized that CWD should spread faster in regions with long-distance migratory mule deer, but this hypothesis was only partially supported. 4. Observed rates of CWD spread were faster in western epicenters with more mobile mule deer than in epicenters with only white-tailed deer (14-18 km/yr compared to 5-7 km/yr, respectively). However, the observed speed of CWD spread did not align well with migration distances. Deer movements in the Canadian Prairie Provinces (CPP) were far shorter than those in Colorado and Wyoming, yet had faster CWD spread much of which was open prairies where deer movements tend to be along riverine corridors rather than the longer elevational migrations in more montane regions. 5. Generally, our predicted rates of CWD spread from three different models were far slower than the observed rates regardless of whether the model included dispersal or migration. Understanding of these discrepancies is needed before high-resolution animal movement data can be used to predict broad-scale patterns of disease invasion. 6. Anthropogenic movements likely explain longer-distance movements of CWD across North America, but it remains unclear whether human-mediated movements or alternative analytical methods and deer movement metrics can explain the faster than predicted local CWD spread.

Journal of Animal Ecology↗

USGS2021

Migration distance and maternal resource allocation determine timing of birth in a large herbivore

Birth timing is a key life-history characteristic that influences fitness and population performance. For migratory animals, however, appropriately timing birth on one seasonal range may be constrained by events occurring during other parts of the migratory cycle. We investigated how the use of capital and income resources may facilitate flexibility in reproductive phenology of migratory mule deer in western Wyoming, USA, over a 5-yr period (2015–2019). Specifically, we examined how seasonal interactions affected three interrelated life-history characteristics: fetal development, birth mass, and birth timing. Females in good nutritional condition at the onset of winter and those that migrated short distances had more developed fetuses (measured as fetal eye diameter in March). Variation in parturition date was explained largely by fetal development; however, there were up to 16 d of plasticity in expected birth date. Plasticity in expected birth date was shaped by income resources in the form of exposure to spring green-up. Although individuals that experienced greater exposure to spring green-up were able to advance expected birth date, being born early or late with respect to fetal development had no effect on birth mass of offspring. Furthermore, we investigated the trade-offs migrating mule deer face by evaluating support for existing theory that predicts that births should be matched to local peaks in resource availability at the birth site. In contrast to this prediction, only long-distance migrants that paced migration with the flush of spring green-up, giving birth shortly after ending migration, were able to match birth with spring green-up. Shorter-distance migrants completed migration sooner and gave birth earlier, seemingly trading off more time for offspring to grow and develop over greater access to resources. Thus, movement tactic had profound downstream effects on birth timing. These findings highlight a need to reconsider classical theory on optimal birth timing, which has focused solely on conditions at the birth site.

Wyoming↗

USGS2012

Developing a quality assurance plan for telemetry studies: A necessary management tool for an effective study

Telemetry has been used to answer various questions associated with research, management, and monitoring programs and to monitor animal behavior and population dynamics throughout the world. Many telemetry projects have been developed to study the passage, behavior, and survival of migrating adult and juvenile salmonids at hydroelectric projects on the mainstem Columbia and Snake rivers (Skalski et al. 2001a, 2001b; Skalski et al. 2002; Keefer et al. 2004; Goniea et al. 2006; Plumb et al. 2006). Telemetry based field evaluations of the survival of salmon through hydroelectric projects are costly because of the technology (tags, telemetry systems, infrastructure, etc.) and personnel required to conduct the evaluations. Given the cost of implementing these projects, and the financial and conservation implications of the decisions made from the research results (e.g., forgone electricity production and conservation of threatened and endangered animals), ensuring quality data are collected by documenting all procedures, training, data checks, and that sound protocols and quality assurance and control procedures are in place is paramount. Telemetry studies can pose unique data collection, processing, and analysis challenges. For instance, inferences about entire populations of animals are made from study animals that are captured, held, and tagged at disparate locations. Consequently great care must be taken to ensure that any potential biases that could arise from field procedures must be minimized (Peven et al. 2005). Interrogations of released study animals are remotely conducted by telemetry systems throughout the study area. The continuous recording of telemetry systems can result in large numbers of detections over a short time frame and the potential for false positive detections from records that are weak or erroneous. Thus, there is the potential to generate large data sets (many thousands of lines) that require significant postprocessing. Data reduction can be done using software or programming code within a software package or manually to discern noise from valid data and pull out the pertinent information for analysis. In either case, consistent well-documented procedures need to be in place to ensure quality results and allow for repeatability of study methods.

Book chapter↗

USGS2024

Migratory strategies across an ecological barrier: Is the answer blowing in the wind?

Background: Ecological barriers can shape the movement strategies of migratory animals that navigate around or across them, creating migratory divides. Wind plays a large role in facilitating aerial migrations, and can temporally or spatially change the challenge posed by an ecological barrier, with beneficial winds potentially converting a barrier to a corridor. Here, we explore the role wind plays in shaping initial southbound migration strategy between two populations departing from different locations along an ecological barrier. Methods: Using GPS satellite transmitters, we tracked the southbound migration of two populations of Short-billed Dowitchers ( Limnodromus griseus caurinus ) from breeding grounds in Alaska to wintering sites in coastal Mexico. The breeding grounds were positioned in distinct regions along an ecological barrier, the Gulf of Alaska. Between the two populations, we compared migratory timing, wind availability at, and tailwind support en route across the Gulf of Alaska. Results: Route choice and arrival timing to wintering sites differed markedly between the two populations: individuals departing from the more westerly site (King Salmon) left at the same time as those from further east (Beluga) but crossed the Gulf of Alaska farther west and arrived along the Pacific coast of Mexico an average of 19 days earlier than their counterparts. Dowitchers from both sites used a slight tailwind to cue departure, but once aloft over the Gulf of Alaska, birds from the more westerly site had up to ten times more tailwind assistance than birds from the more easterly one. Conclusions: The distinct migration strategies, and degree of wind assistance experienced, of these two populations demonstrates how differences in wind availability along migratory routes may form the basis for intraspecific variation in migration strategies with potential carryover effects. Future changes in wind regimes may therefore interact with changes in habitat availability to influence migration patterns and migratory bird conservation.

Alaska↗

USGS1983

Use of nearshore and estuarine areas by gray whales ( Eschrichtius robustus ) in the eastern Bering Sea

During spring aerial surveys of the coast of the southeastern Bering Sea significant numbers of gray whales were seen in nearshore waters along the north side of the Alaska Peninsula. Many (50-80%) of these animals were observed surfacing with mud trails or lying on their sides, characteristics both associated with feeding. A migration route close to shore (within 1-2 km) was used until whales neared Egegik Bay, where they began to head west 5-8 km offshore, across northern Bristol Bay. Smaller numbers of gray whales were present throughout summer in nearshore waters and estuaries along the north side of the Alaska Peninsula. At Nelson Lagoon gray whales normally used the lagoon in spring, were absent during early summer, returned in mid-summer, and then were present until late November when they departed for the wintering grounds. Gray whales were present in the lagoon most often during periods of peak tidal flow; those that appeared to be feeding were oriented into the current. Three behaviors that appeared to be associated with feeding were observed: side-feeding from a stationary position within shallow waters of lagoon channels, diving within the lagoon and in nearshore waters, and elliptical side-feeding in the surf zone along the outer coast. Large crustaceans of the genus Crangon were available to and probably eaten by gray whales at Nelson Lagoon.

Alaska↗

USGS2015

Population size and stopover duration estimation using mark–resight data and Bayesian analysis of a superpopulation model

We present a novel formulation of a mark–recapture–resight model that allows estimation of population size, stopover duration, and arrival and departure schedules at migration areas. Estimation is based on encounter histories of uniquely marked individuals and relative counts of marked and unmarked animals. We use a Bayesian analysis of a state–space formulation of the Jolly–Seber mark–recapture model, integrated with a binomial model for counts of unmarked animals, to derive estimates of population size and arrival and departure probabilities. We also provide a novel estimator for stopover duration that is derived from the latent state variable representing the interim between arrival and departure in the state–space model. We conduct a simulation study of field sampling protocols to understand the impact of superpopulation size, proportion marked, and number of animals sampled on bias and precision of estimates. Simulation results indicate that relative bias of estimates of the proportion of the population with marks was low for all sampling scenarios and never exceeded 2%. Our approach does not require enumeration of all unmarked animals detected or direct knowledge of the number of marked animals in the population at the time of the study. This provides flexibility and potential application in a variety of sampling situations (e.g., migratory birds, breeding seabirds, sea turtles, fish, pinnipeds, etc.). Application of the methods is demonstrated with data from a study of migratory sandpipers.

Biometrics↗

USGS2010

Bringing wisents back to the Caucasus Mountains: 70 years of a grand mission

We describe the history of mountain wisent restoration in the north-west Caucasus region. We review information on wisent during the 18th and 19th centuries, contemporary regional development and reasons for wisent extirpation. We emphasize the key role of the Kuban Hunting Reserve as a main factor in preserving wisent in this region between 1888 and 1909. The article provides information on the fate of three known Caucasus wisent and their impact on the common pedigree of EuropeanWisent. The importance of scientist’s efforts to conserve the survived wisent in Europe in 1920th and international cooperation is underscored. The issues of hybridization between wisent and American bison and the possible influence of hybridization events on the and taxonomic status of contemporary mountain wisent are discussed. We describes in detail the history of wisent reintroduced to the Caucasus, the establishment of seasonal migration patterns and adaptation to the mountainous region and poaching pressures. Mountain wisent reached a maximum number of 1500 animals in 1991. We review the significant role of the Caucasian Biosphere Reserve and its zoologists in conservation of mountain wisent in its historical area and current research objectives with the support of German conservation organizations.

European Bison Conservation Newletter↗

USGS2008

Flower power: Tree flowering phenology as a settlement cue for migrating birds

1. Neotropical migrant birds show a clear preference for stopover habitats with ample food supplies; yet, the proximate cues underlying these decisions remain unclear. 2. For insectivorous migrants, cues associated with vegetative phenology (e.g. flowering, leaf flush, and leaf loss) may reliably predict the availability of herbivorous arthropods. Here we examined whether migrants use the phenology of five tree species to choose stopover locations, and whether phenology accurately predicts food availability. 3. Using a combination of experimental and observational evidence, we show migrant populations closely track tree phenology, particularly the flowering phenology of honey mesquite (Prosopis glandulosa), and preferentially forage in trees with more flowers. Furthermore, the flowering phenology of honey mesquite reliably predicts overall arthropod abundance as well as the arthropods preferred by migrants for food. 4. Together, these results suggest that honey mesquite flowering phenology is an important cue used by migrants to assess food availability quickly and reliably, while in transit during spring migration. ?? 2008 The Authors.

Journal of Animal Ecology↗

USGS1975

Inhibition of salt water survival and Na-K-ATPase elevation in steelhead trout (Salmo gairdneri) by moderate water temperatures

The steelhead trout metamorphosis from a freshwater parr to a sea water-tolerant smolt possessing the migration tendency was evaluated at six different growth temperatures ranging from 6 to 15 C during January through July. The highest temperature where a transformation was indicated was 11.3 C. By April fish reared at 6 C had elevated ATPase levels typical of smolts or migratory animals and showed 92% survival in sea water. Ten and 11.3 C-reared fish showed a short-lived elevation in ATPase in mid-April alone concurrently with 100% sea water survival at that time. Only in 6 C-reared animals did the salt water survival ability continue into May. High ATPase levels likewise were prolonged into May and June only in the 6 C-reared group. The data indicate that metamorphosis (and therefore successful migration) of juvenile steelhead trout is directly controlled by water temperature.

Transactions of the American Fisheries Society↗

USGS2002

Using satellite telemetry to define spatial population structure in polar bears in the Norwegian and western Russian Arctic

1. Animal populations, defined by geographical areas within a species’ distribution where population dynamics are largely regulated by births and deaths rather than by migration from surrounding areas, may be the correct unit for wildlife management. However, in heterogeneous landscapes varying habitat quality may yield subpopulations with distinct patterns in resource use and demography significant to the dynamics of populations. 2. To define the spatial population structure of polar bears Ursus maritimus in the Norwegian and western Russian Arctic, and to assess the existence of a shared population between the two countries, we analysed satellite telemetry data obtained from 105 female polar bears over 12 years. 3. Using both cluster analyses and home-range estimation methods, we identified five population units inhabiting areas with different sea-ice characteristics and prey availability. 4. The continuous distribution of polar bear positions indicated that the different subpopulations formed one continuous polar bear population in the Norwegian and western Russian Arctic. Hence, Norway and Russia have a shared management responsibility. 5. The spatial population structure identified will provide a guide for evaluating geographical patterns in polar bear ecology, the dynamics of polar bear–seal relationships and the effects of habitat alteration due to climate change. The work illustrates the importance of defining population borders and subpopulation structure in understanding the dynamics and management of larger animals.

Arctic↗

USGS2023

Hidden Markov movement models reveal diverse seasonal movement patterns in two North American ungulates

Animal movement is the mechanism connecting landscapes to fitness, and understanding variation in seasonal animal movements has benefited from the analysis and categorization of animal displacement. However, seasonal movement patterns can defy classification when movements are highly variable. Hidden Markov movement models (HMMs) are a class of latent-state models well-suited to modeling movement data. Here, we used HMMs to assess seasonal patterns of variation in the movement of pronghorn ( Antilocapra americana ), a species known for variable seasonal movements that challenge analytical approaches, while using a population of mule deer ( Odocoileus hemionus ), for whom seasonal movements are well-documented, as a comparison. We used population-level HMMs in a Bayesian framework to estimate a seasonal trend in the daily probability of transitioning between a short-distance local movement state and a long-distance movement state. The estimated seasonal patterns of movements in mule deer closely aligned with prior work based on indices of animal displacement: a short period of long-distance movements in the fall season and again in the spring, consistent with migrations to and from seasonal ranges. We found seasonal movement patterns for pronghorn were more variable, as a period of long-distance movements in the fall was followed by a winter period in which pronghorn were much more likely to further initiate and remain in a long-distance movement pattern compared with the movement patterns of mule deer. Overall, pronghorn were simply more likely to be in a long-distance movement pattern throughout the year. Hidden Markov movement models provide inference on seasonal movements similar to other methods, while providing a robust framework to understand movement patterns on shorter timescales and for more challenging movement patterns. Hidden Markov movement models can allow a rigorous assessment of the drivers of changes in movement patterns such as extreme weather events and land development, important for management and conservation.

Wyoming↗

USGS2015

A new method for discovering behavior patterns among animal movements

Advanced satellite tracking technologies enable biologists to track animal movements at fine spatial and temporal scales. The resultant data present opportunities and challenges for understanding animal behavioral mechanisms. In this paper, we develop a new method to elucidate animal movement patterns from tracking data. Here, we propose the notion of continuous behavior patterns as a concise representation of popular migration routes and underlying sequential behaviors during migration. Each stage in the pattern is characterized in terms of space (i.e., the places traversed during movements) and time (i.e. the time spent in those places); that is, the behavioral state corresponding to a stage is inferred according to the spatiotemporal and sequential context. Hence, the pattern may be interpreted predictably. We develop a candidate generation and refinement framework to derive all continuous behavior patterns from raw trajectories. In the framework, we first define the representative spots to denote the underlying potential behavioral states that are extracted from individual trajectories according to the similarity of relaxed continuous locations in certain distinct time intervals. We determine the common behaviors of multiple individuals according to the spatiotemporal proximity of representative spots and apply a projection-based extension approach to generate candidate sequential behavior sequences as candidate patterns. Finally, the candidate generation procedure is combined with a refinement procedure to derive continuous behavior patterns. We apply an ordered processing strategy to accelerate candidate refinement. The proposed patterns and discovery framework are evaluated through conceptual experiments on both real GPS-tracking and large synthetic datasets.

International Journal of Geographical Information ↗

USGS2017

Assessment of PIT tag retention and post-tagging survival in metamorphosing juvenile Sea Lamprey

Background: Passive integrated transponder (PIT) tags have been used to document and monitor the movement or behavior of numerous species of fishes. Data on short-term and long-term survival and tag retention are needed before initiating studies using PIT tags on a new species or life stage. We evaluated the survival and tag retention of 153 metamorphosing juvenile Sea Lamprey Petromyzon marinus tagged with 12 mm PIT tags on three occasions using a simple surgical procedure. Results: Tag retention was 100% and 98.6% at 24 h and 28-105 d post-tagging. Of the lamprey that retained their tags, 87.3% had incisions sufficiently healed to prevent further loss. Survival was 100% and 92.7% at 24 h and 41-118 d post-tagging with no significant difference in survival between tagged and untagged control lamprey. Of the 11 lamprey that died, four had symptoms that indicated their death was directly related to tagging. Survival was positively correlated with Sea Lamprey length. Conclusions: Given the overall high level of survival and tag retention in this study, future studies can utilize 12 mm PIT tags to monitor metamorphosing juvenile Sea Lamprey movement and migration patterns.

Animal Biotelemetry↗

USGS2024

Geese migrating over the Pacific Ocean select altitudes coinciding with offshore wind turbine blades

Renewable energy facilities are a key part of mitigating climate change, but can pose threats to wild birds and bats, most often through collisions with infrastructure. Understanding collision risk and the factors affecting it can help minimize impacts on wild populations. For wind turbines, flight altitude is a major factor influencing collision risk, and altitude-selection analyses can evaluate when and why animals fly at certain altitudes under certain conditions. We used GPS tags to track Pacific Flyway geese (Pacific greater white-fronted goose, tule greater white-fronted goose and lesser snow goose) on transoceanic migrations between Alaska and the Pacific Coast of the contiguous United States, an area where offshore windfarm development is beginning. We evaluated how geographic and environmental covariates affected (1) whether birds were at rest on the water versus in flight (binomial model) and (2) altitude selection when in flight (similar to a step-selection framework). We then used a Monte Carlo simulation to predict the probability of flying at each altitude under various conditions, considering both the fly/rest decision and altitude selection. In both spring and fall, geese showed strong selection for altitudes within the expected rotor-swept zone (20–200 m asl), with 56% of locations expected to be within the rotor-swept zone under mean daylight conditions and 28% at night. This indicates a high possibility that migrating geese may be at risk of collision when passing through windfarms. Although there was some variation across subspecies, geese were most likely to be within the rotor-swept zone with little wind or light tailwinds, low clouds, little to no precipitation and moderate to cool air temperatures. Geese were unlikely to be in the rotor-swept zone at night, when most individuals were at rest on the water. Synthesis and applications . These results could be used to inform windfarm management, including decisions to shut down turbines when collision risk is high. The altitude-selection framework we demonstrate could facilitate further study of other bird species to develop a holistic view of how windfarms in this area could affect the migratory bird community as a whole.

Journal of Applied Ecology↗

USGS2017

Simulated juvenile salmon growth and phenology respond to altered thermal regimes and stream network shape

It is generally accepted that climate change will stress coldwater species such as Pacific salmon. However, it is unclear what aspect of altered thermal regimes (e.g., warmer winters, springs, summers, or increased variability) will have the greatest effect, and what role the spatial properties of river networks play. Thermally diverse habitats may afford protection from climate change by providing opportunities for aquatic organisms to find and use habitats with optimal conditions for growth. We hypothesized that climate‐altered thermal regimes will change growth and timing of life history events such as emergence or migration but that changes will be moderated in topologically complex stream networks where opportunities to thermoregulate are more readily available to mobile animals. Because climate change effects on populations are spatially variable and contingent upon physiological optima, assessments of risk must take a spatially explicit approach. We developed a spatially structured individual‐based model for Chinook Salmon ( Oncorhynchus tshawytscha ) in which movement decisions and growth were governed by water temperature and conspecific density. We evaluated growth and phenology (timing of egg emergence and smolting) under a variety of thermal regimes (each having a different minimum, rate of warming, maximum, and variability) and in three network shapes of increasing spatial complexity. Across networks, fish generally grew faster and were capable of smolting earlier in warmer scenarios where water temperatures experienced by fish were closer to optimal; however, growth decreased for some fish. We found that salmon size and smolt date responded more strongly to warmer springs and summers than to warmer winters or increased variability. Fish in the least complex network grew faster and were ready to smolt earlier than fish in the more spatially complex network shapes in the contemporary thermal regime; patterns were similar but less clear in warmer thermal regimes. Our results demonstrate that network topology may influence how fish respond to thermal landscapes, and this information will be useful for incorporating a spatiotemporal context into conservation decisions that promote long‐term viability of salmon in a changing climate.

Ecosphere↗

USGS2026

Predictability creates vulnerability: Long-term acoustic telemetry reveals hidden threat windows for endangered Atlantic sturgeon

1.Individual movement strategies govern access to important habitats but can expose certain animals to spatially and temporally variable threats, producing consistent, phenotype-specific differences in risk. For endangered Atlantic sturgeon ( Acipenser oxyrinchu s), migration timing shapes exposure risk to vessel strikes, dredging activity, and shifting estuarine conditions, yet management to minimize exposure to these threats is predominantly based on population-average patterns of river occupancy. 2. We analysed a decade of acoustic telemetry data from 195 Atlantic sturgeon in the Hudson River to quantify individual variation in migration timing. We clustered individuals into distinct behavioural phenotypes and evaluated the consistency of these phenotypes across years to determine whether certain individuals may be present in spatiotemporal areas that are not represented in current conservation frameworks. 3. Results identified two persistent phenotypes: the short-residency phenotype exhibiting synchronized occupancy typical of the prescribed Atlantic sturgeon spawning run and an extended-residency group that migrates into the river later, displays prolonged river occupancy and diffuse outmigration into the fall. Extended-residency individuals were last detected approximately 88 days after short-residency individuals and occupied habitats downriver of the presumed spawning grounds, extending the period of sturgeon presence into riverine habitats outside the current spatiotemporal area of conservation focus. 4. Individual phenotypic membership was repeatable across nearly a decade, indicating that these behaviours reflect stable, consistent phenotypes rather than stochastic variation. 5. Synthesis and applications . Our results reveal persistent intrapopulation movement diversity in the largest remaining Atlantic sturgeon population and highlight predictable periods during which a unique phenotype may experience disproportionate exposure to in-river threats. These findings indicate that environmental reviews, permitting decisions and seasonal work windows may benefit from incorporating phenotype-specific occupancy patterns and percentile-based estimates of river residency rather than relying solely on historical spawning dates or population averages. Expanding telemetry and monitoring designs to include broader spatial and seasonal sampling may further improve detection of overlooked movement strategies and reduce potential biases in demographic and habitat use assessments. More broadly, recognizing behavioural diversity in recovery planning may provide a more complete basis for evaluating habitat use, threat exposure, and conservation priorities across sturgeon populations.

New York↗