Study Movement Patterns Research Articles

MOVEMENT PATTERNS, HOME RANGE, AND MICROHABITAT USE OF ALLIGATOR SNAPPING TURTLES (MACROCHELYS TEMMINCKII) IN A SMALL EAST TEXAS STREAM SYSTEM

Abstract The alligator snapping turtle (Macrochelys temminckii), the largest freshwater turtle in North America, faces numerous threats, with population declines and range contractions suspected to have occurred across its historic range. Previous research studying movement patterns and microhabitat use of M. temminckii has mostly been conducted in large, open, lentic environments and few studies have been conducted in small, lotic habitats. We investigated the movement and microhabitat use of adult female and juvenile M. temminckii within Bonaldo Creek, a small tributary of the Angelina River in eastern Texas. Six M. temminckii were monitored (two or three relocations per week) via radiotelemetry from July 2008 to September 2009. We found that the linear home range for adult females (405.1–1395.5 m) was longer than that of the unsexed juveniles (439.7–996.9 m), although movement frequency was similar between groups. Juveniles utilized a smaller subset of microhabitats compared to adult females. Adult females utilized microhabitats with abundant submerged structure, while overhanging vegetation was an important microhabitat feature for juveniles. The broader microhabitat use we observed in adult females may have been influenced by seasonal factors, highlighting the need for more long-term, seasonal assessments of M. temminckii movement and microhabitat. Such investigations will bolster our understanding of the spatial and temporal factors that influence M. temminckii populations in different systems.

Movement patterns of the White‐tailed Sea Eagle (Haliaeetus albicilla): post‐fledging behaviour, natal dispersal onset and the role of the natal environment

Exploratory movements and natal dispersal form essential processes during early life history stages of raptors, but identifying the factors shaping individual movement decisions is challenging. Global positioning system (GPS) telemetry thereby provides a promising technique to study movement patterns on adequate spatio‐temporal scales. We analysed data of juvenile White‐tailed Sea EaglesHaliaeetus albicilla(WTSE) in north‐east Germany (n = 24) derived from GPS tracking to extensively analyse movements between fledging and emigration from the natal territory. Our goal was to determine the time point of fledging, characterize pre‐emigration movements and the onset of natal dispersal while investigating the influence of the natal environment. WTSE fledged at an average age of 72 days and showed strong excursive behaviour during the post‐fledging period regarding the number, distance and duration of excursions, yet with high individual variability. Excursive behaviour did not differ between sexes. On average, WTSE left the parental territory 93 days after fledging. The quantity of excursive behaviour delayed the timing of emigration and WTSE tended to postpone their emigration when foraging water was accessible within the boundaries of their parental territory. The overall results suggest that young WTSE assess the quality of the natal environment via pre‐emigration movements and stay in their territory of origin for as long as internal and external conditions allow for it. Our study is one of the first to characterize post‐fledging and natal dispersal movements of young WTSE to such an extent and applies modern techniques to understand related movements in relation to the natal environment. The results emphasize the urgent necessity for the extension of currently existing nest protection periods and guaranteeing sustainable management of potential breeding and foraging grounds for WTSE. Ultimately, the results are relevant for all large raptor species sensitive to human‐related disturbance, as they support the increasing importance of regulations with spatio‐temporal specifications for breeding populations of large raptors in densely human‐inhabited areas with increasing alteration of land.

A Review of Factors Affecting PIT Tag Detection Using Mobile Arrays and Use of Mobile Antennas to Detect PIT‐Tagged Suckers in a Wadeable Ozark Stream

AbstractAdvantages of PIT tags are their small size, longevity, and low cost compared to other tags. They are often used in fisheries to study movement patterns and survival or to estimate population size. However, PIT tags are limited by their short detection distance. Mobile PIT antennas may increase the utility of PIT tags in fisheries. In this study, we synthesized current detection efficiency literature for mobile PIT antennas, determined physical factors that decreased PIT tag detection probabilities for our antenna, determined factors that influenced the proportion of PIT‐tagged suckers detected by our mobile antenna, and summarized techniques used to increase detections of PIT‐tagged suckers using mobile antennas in a wadable stream. Our literature review indicated that tag size and orientation were the most important factors affecting detection probabilities. However, our manual testing suggested that the detection probability for our antenna was primarily influenced by water depth of the tag and distance from the antenna. Our sucker detection data showed that detection efficiency in our stream was most influenced by discharge, turbidity, and sample date. Tracking methods that include targeting key habitats (e.g., rootwads) and using natural features to congregate tagged fishes (e.g., riffles or pinch points) may increase detection efficiency in wadable streams. This is the first formal review of factors affecting mobile PIT antenna detection efficiency. The published literature, combined with our study results, indicates that several factors need to be considered prior to mobile PIT antenna tracking.

Environmental and anthropogenic correlates of seasonal migrations in the Dinaric‐Pindos brown bear population

AbstractSeasonal migrations (i.e. seasonal round‐trips between disjunct areas) have been rarely documented for large carnivores. The Dinaric‐Pindos brown bear (Ursus arctos) population is the third largest in Europe, but little information is currently available on individual movement patterns. We studied movement patterns by 12 GPS‐collared adult and subadult bears in Croatia and Bosnia Herzegovina during 2004–2017, including migratory movements by some instrumented bears. To investigate environmental correlates of migrations, we first used the canonical Outlying Mean Index analysis, identifying habitat descriptors of summer and fall ranges, and then applied mixed‐effects logistic regression to quantify variation in habitat use between them. Thirty‐seven per cent 37% of the bears (7 bear‐years) migrated during hyperphagia (i.e. partial migration), and seasonal migration was also facultative, as it occurred only during mast (i.e. beechnut) poor years. Migrating bears entered migration during early fall (median = 25 Sept) and returned to their pre‐migratory ranges after about 7 weeks (median = 18 Nov). Net distances between pre‐migratory (summer) and post‐migratory (fall) averaged (±sd) 26.5 ± 9.7 km, with a maximum distance of 38.8 km, corresponding to actual distances travelled of 61.1 ± 21.5 km. Summer ranges from which bears migrated were best described by proximity to supplemental feeding sites and mixed forests, whereas fall ranges reached by migrants were differentiated by lower elevations, and a higher share of deciduous forest, grasslands, forest edges and shrublands. Relative to pre‐migratory ranges, bears in post‐migratory ones increased their distance to anthropogenic features and showed higher use of cover types expectedly richer in berries and other fleshy fruits. Although we lack any causative evidence, we speculate migration in this bear population is triggered during poor beechnut years by increased social despotic interference at supplemental feeding sites that elicits redistribution of subordinate bears.

Movement patterns and habitat selection during dispersal in Eurasian lynx

Natal dispersal affects the gene flow, distribution, dynamics and social structure of a population. In many solitary mammals, dispersal is often male-biased, while females may remain philopatric. For the Eurasian lynx (Lynx lynx), dispersal distances vary greatly and may be explained by sex or by habitat characteristics, such as fragmentation. Juvenile lynx habitat selection during dispersal has not been studied before, but resident lynx select heterogeneous forested habitats and avoid human settlements and infrastructure through distinct temporal activity patterns. We studied movement patterns and habitat selection during the dispersal of 22 Eurasian lynx (7 females, 15 males) in Finland. We found no differences between the sexes in the onset age, duration, distance, route or route linearity. Dispersal took place mostly during the evening and at night but also during the day. Of the four most used habitats, the mixed forests and transitional woodlands were used more frequently than would be expected according to their availability, and conifer forests and fields less than would be expected. Housing and other human infrastructure, including roads, were the least frequently used categories. There was a highly significant difference between the used and available habitats in general. The lynx selected the habitat more carefully during the day than during the night.

Development and validation of statistical shape models of the primary functional bone segments of the foot.

IntroductionMusculoskeletal models are important tools for studying movement patterns, tissue loading, and neuromechanics. Personalising bone anatomy within models improves analysis accuracy. Few studies have focused on personalising foot bone anatomy, potentially incorrectly estimating the foot’s contribution to locomotion. Statistical shape models have been created for a subset of foot-ankle bones, but have not been validated. This study aimed to develop and validate statistical shape models of the functional segments in the foot: first metatarsal, midfoot (second-to-fifth metatarsals, cuneiforms, cuboid, and navicular), calcaneus, and talus; then, to assess reconstruction accuracy of these shape models using sparse anatomical data.MethodsMagnetic resonance images of 24 individuals feet (age = 28 ± 6 years, 52% female, height = 1.73 ± 0.8 m, mass = 66.6 ± 13.8 kg) were manually segmented to generate three-dimensional point clouds. Point clouds were registered and analysed using principal component analysis. For each bone segment, a statistical shape model and principal components were created, describing population shape variation. Statistical shape models were validated by assessing reconstruction accuracy in a leave-one-out cross validation. Statistical shape models were created by excluding a participant’s bone segment and used to reconstruct that same excluded bone using full segmentations and sparse anatomical data (i.e. three discrete points on each segment), for all combinations in the dataset. Tali were not reconstructed using sparse anatomical data due to a lack of externally accessible landmarks. Reconstruction accuracy was assessed using Jaccard index, root mean square error (mm), and Hausdorff distance (mm).ResultsReconstructions generated using full segmentations had mean Jaccard indices between 0.77 ± 0.04 and 0.89 ± 0.02, mean root mean square errors between 0.88 ± 0.19 and 1.17 ± 0.18 mm, and mean Hausdorff distances between 2.99 ± 0.98 mm and 6.63 ± 3.68 mm. Reconstructions generated using sparse anatomical data had mean Jaccard indices between 0.67 ± 0.06 and 0.83 ± 0.05, mean root mean square error between 1.21 ± 0.54 mm and 1.66 ± 0.41 mm, and mean Hausdorff distances between 3.21 ± 0.94 mm and 7.19 ± 3.54 mm. Jaccard index was higher (P < 0.01) and root mean square error was lower (P < 0.01) in reconstructions from full segmentations compared to sparse anatomical data. Hausdorff distance was lower (P < 0.01) for midfoot and calcaneus reconstructions using full segmentations compared to sparse anatomical data.ConclusionFor the first time, statistical shape models of the primary functional segments of the foot were developed and validated. Foot segments can be reconstructed with minimal error using full segmentations and sparse anatomical landmarks. In future, larger training datasets could increase statistical shape model robustness, extending use to paediatric or pathological populations.

Tree-Based and Optimum Cut-Based Origin-Destination Flow Clustering

Data about the movements of diverse objects, including human beings, animals, and commodities, are collected in growing amounts as location-aware technologies become pervasive. Clustering has become an increasingly important analytical tool for revealing travel patterns from large-scale movement datasets. Most existing methods for origin-destination (OD) flow clustering focus on the geographic properties of an OD flow but ignore the temporal information preserved in the OD flow, which reflects the dynamic changes in the travel patterns over time. In addition, most methods require some predetermined parameters as inputs and are difficult to adjust considering the changes in the users’ demands. To overcome such limitations, we present a novel OD flow clustering method, namely, TOCOFC (Tree-based and Optimum Cut-based Origin-Destination Flow Clustering). A similarity measurement method is proposed to quantify the spatial similarity relationship between OD flows, and it can be extended to measure the spatiotemporal similarity between OD flows. By constructing a maximum spanning tree and splitting it into several unrelated parts, we effectively remove the noise in the flow data. Furthermore, a recursive two-way optimum cut-based method is utilized to partition the graph composed of OD flows into OD flow clusters. Moreover, a criterion called CSSC (Child tree/Child graph Self-Similarity Criterion) is formulated to determine if the clusters meet the output requirements. By modifying the parameters, TOCOFC can obtain clustering results for different time scales and spatial scales, which makes it possible to study movement patterns from a multiscale perspective. However, TOCOFC has the disadvantages of low efficiency and large memory consumption, and it is not conducive to quickly handling large-scale data. Compared with previous works, TOCOFC has a better clustering performance, which is reflected in the fact that TOCOFC can guarantee a balance between clusters and help to fully understand the corresponding patterns. Being able to perform the spatiotemporal clustering of OD flows is also a highlight of TOCOFC, which will help to capture the differences in the patterns at different times for a deeper analysis. Extensive experiments on both artificial spatial datasets and real-world spatiotemporal datasets have demonstrated the effectiveness and flexibility of TOCOFC.

Spatio-temporal migratory dynamics of Jasus frontalis (Milne Edwards, 1837) in Alexander Selkirk Island, Juan Fernández archipelago, Chile.

Knowledge about the spatial patterns and movements of crustaceans has gained importance since the creation of marine protected areas and the development of spatial management for benthic ecosystems. The Juan Fernández spiny lobster (Jasus frontalis) is an endemic marine species and most valuable resource that exhibits migratory dynamics in a highly spatially regulated fishery. To study movement patterns around Alexander Selkirk Island, a mark-recapture program was implemented in 2008, when approximately 7000 non-commercial (undersized) lobsters were tagged and followed for nearly 14 months. Using quantitative georeferenced data, this study revealed spatial structuring of Juan Fernández spiny lobster and tested hypotheses about alongshore and inshore-offshore movements. Eight clusters were identified around Alexander Selkirk Island, with moderate time-varying connectivity between them. Seasonal inshore-offshore movements were detected all around the island, but more conspicuously to the north. Average travelling distance was 1.2 km (1.7 sd). Our results confirmed that towards the end of austral spring males and females embark in a seasonal offshore migration to deeper waters, returning to shallower waters only during winter. These findings quantitatively consolidate the conceptual migratory model that local fishermen had already inferred for this resource from about a century of sustainable fishing.

Enhancing data privacy with semantic trajectories: A raster‐based framework for GPS stop/move management

AbstractTracking facilities on smartphones generate enormous amounts of GPS trajectories, which provide new opportunities to study movement patterns and improve transportation planning. Converting GPS trajectories into semantically meaningful trips is attracting increasing research effort with respect to the development of algorithms, frameworks, and software tools. There are, however, few works focused on designing new semantic enrichment functionalities taking privacy into account. This article presents a raster‐based framework which not only detects significant stop locations, segments GPS records into stop/move structures, and brings semantic insights to trips, but also provides possibilities to anonymize users’ movements and sensitive stay/move locations into raster cells/regions so that a multi‐level data sharing structure is achieved for a variety of data sharing purposes.

Assessing impacts of intrinsic and extrinsic factors on Florida panther movements

Movement patterns can influence an animal's ability to secure food, find mates, and avoid enemies, potentially affecting individual fitness. We studied movement patterns of 10 male and 3 female endangered Florida panthers (Puma concolor coryi) using location data collected from a long-term (2005–2012) GPS collar study. Males traveled faster and covered longer daily distances than females during both the wet and dry seasons (wet:dry—males 289:372 m/h and 4,616:6,701 m; females 186:280 m/h and 2,629:5,239 m). Panthers occupying higherselected habitat traveled faster, but with shorter daily movement distances in comparison to habitats that were less frequently selected. An index of risk (derived using traffic volume and road density) that was linked to habitat predicted to be avoided by panthers was associated with reduced daily movement distances. Our results suggest that Florida panthers alter their movement patterns in response to environmental change and anthropogenic disturbances.

Movements and habitat use of the night parrot Pezoporus occidentalis in south‐western Queensland

AbstractThe nocturnal, cryptic and geographically remote nature of night parrots, combined with their apparent rapid decline, means that very little is known of their biology or ecology. The discovery of a resident population in south‐western Queensland in 2013 provides the first opportunity to undertake detailed studies on this most enigmatic of birds. We attached a radio tag to a bird for 20 days in April 2015 and a GPS tag to another bird for 5 days in May 2016 to study movement patterns and habitat use. Both birds displayed similar behaviour but the GPS‐tagging provided a much finer resolution of spatial data. They called at dusk from their diurnal roosts amongst spinifex hummocks and then flew to more floristically diverse habitats dominated by large‐seeded species to feed. We conducted floristic surveys to describe the feeding grounds of the GPS‐tagged bird and make dietary inferences. This individual spent most of its time in highly diverse but ephemeral habitats, including seasonally inundated plains and depressions associated with the outer Diamantina floodplain and gilgais on ironstone plains. Prolifically seeding ephemeral species, most notably the annual grass Uranthoecium truncatum, dominate these feeding grounds. This work suggests that the habitat mosaic containing roost sites in close proximity to feeding grounds with key seed‐producing species is an important factor, rather than an association with spinifex or samphire alone. Further work is needed to examine movement patterns and habitat use in more typical dry seasons and the impact of cattle grazing on night parrot feeding areas, particularly with regard to seed production. The information presented here is vital for both in situ conservation of the Pullen‐Pullen‐Mt Windsor‐Diamantina population and for setting future research and survey priorities.

Identification of potential fish stocks and lifetime movement patterns of Mugil liza Valenciennes 1836 in the Southwestern Atlantic Ocean

The mullet Mugil liza is the Mugilidae that lives southernmost in the western Atlantic Ocean. Knowledge about migration, movements and identification of stocks of this important fishery resource is scarce. Thus, we aim to study movement patterns and to identify the presence of different fish stocks in the southwestern region of the Atlantic Ocean, using cumulative otolith shape morphometric and microchemical analyses of sagittae otoliths. Specimens (n=99) were obtained in four coastal areas: Paranaguá Bay in Brazil, Samborombón Bay, Mar Chiquita Coastal Lagoon, and San Blas Bay in Argentina. Otolith shape indices (circularity, rectangularity, aspect ratio, percentage occupied by sulcus, ellipticity and form factor) were used for stock identification analysis; and otolith microchemistry using LA-ICP-MS (Sr/Ca and Ba/Ca ratios chronological variation) was used for both the analysis of movement behaviors and the identification of fish stocks (otolith edge ratios). Morphometrical indices did not reveal a clear separation among areas. San Blas bay individuals presented otoliths tending to be longer than wider, with a more elliptic shape than the otoliths from other studied areas; also, this area did not share individuals with the most northern one, Paranaguá Bay in Brazil. The analysis of microchemical lifetime profiles revealed three types of behavior pattern: Type I: most frequent use of estuarine environments; Type II: a fluctuating behavior between estuarine and sea/high salinity waters; Type III: most frequent use of sea/high salinity habitats. Otolith edge analysis did not reveal differences among Sr/Ca and Ba/Ca ratios for the different areas. Thus, it cannot be assured that there is more than one stock in the studied region. Mugil liza revealed different environmental migratory behaviors in the Southwestern Atlantic Ocean showing a facultative use of estuarine waters; hence, the species appears to be mostly coastal with the use of low estuaries, as seen also by the Sr/Ca otolith cores ratios; differing from the general mugilid behavior previoulsy described.

Where do Norway rats live? Movement patterns and habitat selection in livestock farms in Argentina

Context The Norway rat (Rattus norvegicus) is recognised as one of the most harmful invasive mammal species in natural, urban and rural environments worldwide. Prevention and control of pest species in livestock farms is necessary to protect animal and human health, but control practices usually do not take into account the biology and ecology of the species to be controlled. The understanding of the biological requirements of Norway rats is necessary for the implementation of efficient management actions. Aims The aim of this research was to study movement patterns and habitat selection of Norway rats on livestock farms in central Argentina. We hypothesised that rats select specific areas within the farms according to the farm’s structure and to the availability of resources. Methods We conducted live-trapping of rats in a pig farm and a dairy farm, during each of four seasons over 1 year. Traps were active for three consecutive days at each trapping session. Movements and habitat selection were assessed by spool-and-line technique combined with environmental surveys and GIS tools. Key results We captured a total of 133 Norway rats and evaluated the movements of 47 individuals. The mean length travelled, registered for one night, was 84.28 ± 38.21 m. They did not travel great linear distances within the farms, but instead performed tortuous trajectories around specific sites. Norway rats selected sites containing food, water and refuges; and avoided travelling across areas with short vegetation. Sites containing food sources were most preferred. Conclusions Because food sources for rats were present ad libitum in farms, our findings strongly support the idea that management strategies of prevention and control of this species must include adequate rodent-proof food storage. Also, because rats are found close to livestock, improvement in preventing rats’ access to animal sheds is necessary to prevent contamination of livestock feeders with pathogens carried by rats. Implications The present study provides novel information about the ecology of Norway rats on livestock farms. We encourage farmers to follow our recommendations in order to improve rodent-control strategies.

Cool Headed Individuals Are Better Survivors: Non-Consumptive and Consumptive Effects of a Generalist Predator on a Sap Feeding Insect.

Non-consumptive effects (NCEs) of predators are part of the complex interactions among insect natural enemies and prey. NCEs have been shown to significantly affect prey foraging and feeding. Leafhopper's (Auchenorrhyncha) lengthy phloem feeding bouts may play a role in pathogen transmission in vector species and also exposes them to predation risk. However, NCEs on leafhoppers have been scarcely studied, and we lack basic information about how anti-predator behaviour influences foraging and feeding in these species. Here we report a study on non-consumptive and consumptive predator-prey interactions in a naturally co-occurring spider–leafhopper system. In mesocosm arenas we studied movement patterns during foraging and feeding of the leafhopper Psammotettix alienus in the presence of the spider predator Tibellus oblongus. Leafhoppers delayed feeding and fed much less often when the spider was present. Foraging movement pattern changed under predation risk: movements became more frequent and brief. There was considerable individual variation in foraging movement activity. Those individuals that increased movement activity in the presence of predators exposed themselves to higher predation risk. However, surviving individuals exhibited a ‘cool headed’ reaction to spider presence by moving less than leafhoppers in control trials. No leafhoppers were preyed upon while feeding. We consider delayed feeding as a “paradoxical” antipredator tactic, since it is not necessarily an optimal strategy against a sit-and-wait generalist predator.

Geo-Located Tweets. Enhancing Mobility Maps and Capturing Cross-Border Movement.

Capturing human movement patterns across political borders is difficult and this difficulty highlights the need to investigate alternative data streams. With the advent of smart phones and the ability to attach accurate coordinates to Twitter messages, users leave a geographic digital footprint of their movement when posting tweets. In this study we analyzed 10 months of geo-located tweets for Kenya and were able to capture movement of people at different temporal (daily to periodic) and spatial (local, national to international) scales. We were also able to capture both long and short distances travelled, highlighting regional connections and cross-border movement between Kenya and the surrounding countries. The findings from this study has broad implications for studying movement patterns and mapping inter/intra-region movement dynamics.

Adaptable neighbours: movement patterns of GPS-collared leopards in human dominated landscapes in India.

Understanding the nature of the interactions between humans and wildlife is of vital importance for conflict mitigation. We equipped five leopards with GPS-collars in Maharashtra (4) and Himachal Pradesh (1), India, to study movement patterns in human-dominated landscapes outside protected areas. An adult male and an adult female were both translocated 52 km, and exhibited extensive, and directional, post release movements (straight line movements: male = 89 km in 37 days, female = 45 km in 5 months), until they settled in home ranges of 42 km2 (male) and 65 km2 (female). The three other leopards, two adult females and a young male were released close to their capture sites and used small home ranges of 8 km2 (male), 11 km2 and 15 km2 (females). Movement patterns were markedly nocturnal, with hourly step lengths averaging 339±9.5 m (SE) during night and 60±4.1 m during day, and night locations were significantly closer to human settlements than day locations. However, more nocturnal movements were observed among those three living in the areas with high human population densities. These visited houses regularly at nighttime (20% of locations <25 m from houses), but rarely during day (<1%). One leopard living in a sparsely populated area avoided human settlements both day and night. The small home ranges of the leopards indicate that anthropogenic food resources may be plentiful although wild prey is absent. The study provides clear insights into the ability of leopards to live and move in landscapes that are extremely modified by human activity.

Juvenile Alligator Gar Movement Patterns in a Disconnected Floodplain Habitat in Southeast Missouri

Telemetry is an extremely useful technique used to study movement patterns of fishes to gain insight into life history. This is especially important when dealing with species of conservation concern, such as the alligator gar (Atractosteus spatula). Alligator gar, despite dwindling populations or presumed extirpation across much of its native range, have received minimal attention in the literature. This study sought to evaluate movement patterns of juvenile alligator gar reintroduced to a historic, now disconnected, floodplain of the Mississippi River. Nineteen alligator gar fitted with radio transmitters were stocked into Mingo National Wildlife Refuge during May 2007 and tracked for 1 y. Over the course of the evaluation, 34.9 (se = 5.1) locations per individual gar were recorded and three distinct movement patterns emerged. Thirteen alligator gar (Groups A and B) exhibited site fidelity throughout the study while five alligator gar (Group C) showed highly variable movement patterns; at times showing site fidelity, then exhibiting long-distance movements. When exhibiting site fidelity, alligator gar occupied small areas of Monopoly Marsh or Ditch 5 (Group A: 12.9 ± 6.0 ha, Group B: 4.8 ± 4.9 ha, Group C: 11.8 ± 8.0 ha). Our study demonstrated telemetry of juvenile alligator gar is feasible, various movement patterns (i.e., site fidelity or long-distance movement) exist, and future stockings of juvenile alligator gar are likely to show site fidelity to the area in which they are released.

Spatial Ecology and Factors Influencing Movement Patterns of Desert Massasauga Rattlesnakes (Sistrurus catenatus edwardsii) in Southeastern Colorado

The Massasauga Rattlesnake (Sistrurus catenatus) occurs from extreme southeastern Canada to northern Mexico, and most populations are highly threatened due to habitat loss and fragmentation. Although their range is reduced from historical levels, they may be locally abundant in appropriate habitat. We studied movement patterns, home range and core activity centers, habitat use, and prey abundance in a robust population of Desert Massasauga Rattlesnakes (S. c. edwardsii) in southeastern Colorado by radiotracking 36 snakes over four active seasons (May–October). In the spring, snakes made long-distance directed movements (mean = 1.89 km) from the hibernacula (shortgrass, compacted clay soils) to summer foraging areas (mixed-grass/Sand Sagebrush, sandhills). Summer activity was characterized by short distance non-directional movements, and snakes were most often observed at the base of Sand Sagebrush (Artemisia filifolia). Home ranges and core activity centers were significantly larger for males than for females, but daily movements, total distance moved, and range length did not differ significantly between sexes. Prey base surveys indicated a significantly higher abundance of both rodents and lizards in summer foraging grounds than at hibernation sites. Snakes returned to the hibernaculum area in October and appeared to hibernate individually in rodent burrows. Migration patterns exhibited by S. c. edwardsii are likely resource driven, with the migratory movements observed in the spring resulting in utilization of summer foraging habitat with more abundant prey. Conversely, hibernacula with greater thermal and structural stability in the shortgrass habitat (perhaps due to the compacted clay soils versus loose sandy soils) favor migratory return for torpor in the fall. At present, the main populations in Colorado occur far from developing regions in the state, but due to habitat loss and fragmentation resulting from projected agricultural expansion and urbanization, these populations may be threatened in the future.

Modeling Animal Movements in Response to Human Disturbances

Abstract Background/Question/Methods The advent of GPS technology has made it possible to study human - wildlife interactions on large landscapes and quantify behavioral responses to recreation and other anthropogenic disturbances at increasingly fine scales. Of particular interest are the potential impacts on habitat use patterns, energetics, and cascading impacts on fecundity and other life history traits for key wildlife species that are increasingly exposed to human activities. However, the dynamics of free-ranging animal movements are complex, even without disturbances, and quantifying reactions to disturbance on heterogeneous landscapes is difficult. A modeling framework is required that can sort out diel and random movements that mask short and long-term behavioral response to disturbances.In this talk I will discuss how stochastic differential equations (SDE’s) are used to build potential function surfaces for describing movement patterns and responses to disturbances. I will demonstrate the methods using GPS data for free ranging elk within a 1450 ha study area on the Starkey Experimental Forest located in eastern Oregon. The telemetry data were collected as part of a long-term controlled experiment to understand the response of free ranging Rocky Mountain elk (Cervus elaphus) and deer (Odocoileus hemionus) to multiple anthropogenic disturbances including all terrain vehicles, hikers, mountain bikers and equestrians. This work includes the development of statistical procedures to estimate the simultaneous effects of two or more entities (combinations of animals and disturbance agents) on the potential surfaces, to understand the effects of multiple interacting disturbances on observed patterns of movement.2) Results/Conclusions We parameterized stochastic differential equations to quantify effects of topography; distance to roads; distance to disturbance, and random movements on elk locations. The GPS technology provided evidence that: 1) elk appear to know the location of roads and the routing of traffic on roads through the forest; 2) hikers and equestrians seem to generate a larger movement response compared to mountain bikers and ATV riders; and, 3) The threshold response distance appears to be well beyond those previously reported in studies that relied on visual methods.The study demonstrated the utility of SDE’s and the motivating concept of potential functions to model animal movements. These methods have also been applied by the authors to study movement patterns in yellow legged frogs (Rana sierrae), elephant seals (Mirounga angustirostris), Monk seals (Monachus schauinslandi) and whale sharks (Rhincodon typus ).

Canopy Closure and Emigration by Juvenile Gopher Frogs

ABSTRACT Although studies have addressed effects of abrupt transitions in habitat type (e.g., forest‐clear‐cut or forest‐field edges) on amphibian movements, little is known about effects of more subtle habitat transitions on patterns of migration and habitat use in amphibians. We used radiotelemetry to study movement patterns of juvenile gopher frogs (Rana capito) emigrating from ponds that were surrounded by longleaf pine (Pinus palustris) forest that varied in structure as a result of fire suppression. Our primary purpose was to determine if frogs emigrate directionally from their natal ponds and select habitat at random during their first month following metamorphosis. We found that frogs emigrated in nonrandom directions from ponds that were surrounded by heterogeneous habitat and selected fire‐maintained habitat that was associated with an open canopy, few hardwood trees, small amounts of leaf litter, and large amounts of wiregrass (Aristida beyrichiana). Fire‐maintained habitat contained higher densities of burrows excavated by gopher tortoises (Gopherus polyphemus) and small mammals, which are the priamry refuge sites for both juvenile and adult gopher frogs. Frogs moved up to 691 m from their natal ponds, frequently crossed dirt roads, and even seemed to use these roads as migration corridors. To maintain suitable terrestrial habitat for gopher frogs, including habitat used by migrating individuals, it is important to apply frequent prescribed fire to uplands surrounding breeding ponds that lead all the way to the edges of breeding ponds, as well as through ponds during periodic droughts.