Differences In Space Use Research Articles

Contrasting patterns of vertical and horizontal space use of two exploited and sympatric coral reef fish

Understanding spatial distribution and temporal variation in movement patterns of closely related species is relevant for deciphering how resources are selected and whether interactions between species affect resource use patterns. The horizontal space use and vertical space use of two exploited reef fish, Plectropomus leopardus and P. laevis (all adults), were compared at mid-shelf Helix Reef and Lodestone Reef in the Great Barrier Reef over ~3 years using passive acoustic telemetry. Both species were detected throughout the 12-month duration of transmitters (mean detection period: ~270 days) and often made deep movements to ~40 m possibly related to reproductive behaviour (spawning). Differences in space use were apparent between species, with P. laevis consistently using greater area around reefs throughout the year. Overall, depth use patterns were similar between species; however, when daily detections were grouped in 2-h periods, P. laevis remained shallower and had greater variation in depth use compared to P. leopardus. Contrasting patterns of space use between these co-occurring species, in conjunction with known dietary dissimilarities, indicate distinct habitat use and resource preferences that are important for conservation and fisheries management.

Movement patterns of two carangid species in inshore habitats characterised using network analysis

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 553:219-232 (2016) - DOI: https://doi.org/10.3354/meps11777 Movement patterns of two carangid species in inshore habitats characterised using network analysis Elodie J. I. Lédée1,2,*, Michelle R. Heupel1,3, Andrew J. Tobin1, Amos Mapleston1, Colin A. Simpfendorfer1 1Centre for Sustainable Tropical Fisheries and Aquaculture, College of Marine and Environmental Sciences, James Cook University, Townsville, QLD 4811, Australia 2AIMS@JCU, Australian Institute of Marine Science, College of Marine and Environmental Sciences, James Cook University, Townsville, QLD 4811, Australia 3Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia *Corresponding author: elodie.ledee@my.jcu.edu.au ABSTRACT: Carangids are important ecological components of coastal and reef habitats, in addition to their economic significance as a target species for some fishers. Despite these important ecological and economic roles, little information is available on the movement ecology of these species. Passive acoustic monitoring was used to track the movements of 16 giant trevally Caranx ignobilis and 20 golden trevally Gnathanodon speciosus in Cleveland Bay off the coast of Queensland, Australia. Long-term observations of behaviour and movement were recorded via a network of acoustic receivers, and a network analysis approach (a novel, alternative approach to conventional movement analysis) was applied to the collected data. Tagged individuals were present in the study region between 30 and 394 d (mean ± SD:166 ± 116 d) with a mean ± SE residency index of 0.7 ± 0.1. Notable inter-annual variation occurred with individuals that were detected on more days and more receivers, moved more frequently, and were more resident in some years than in others. In addition, movement patterns differed between species, with C. ignobilis being detected on fewer days by fewer receivers and moving less than G. speciosus. Network analysis revealed that a combination of factors including ontogeny, foraging niche, and habitat influences may explain differences in space use between the species. These results highlight unique behaviours between co-occurring and closely related species and enhance our understanding of animal interactions in inshore habitats. KEY WORDS: Acoustic monitoring · Caranx ignobilis · Gnathanodon speciosus · Information theoretic approach · Network analysis · Mixed model effects Full text in pdf format Supplementary material PreviousNextCite this article as: Lédée EJI, Heupel MR, Tobin AJ, Mapleston A, Simpfendorfer CA (2016) Movement patterns of two carangid species in inshore habitats characterised using network analysis. Mar Ecol Prog Ser 553:219-232. https://doi.org/10.3354/meps11777 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 553. Online publication date: July 14, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Morphological changes in hippocampal cytoarchitecture as a function of spatial treatment in birds.

Maintaining cognitive processes comes with neurological costs. Thus, enhanced cognition and its underlying neural mechanisms should change in response to environmental pressures. Indeed, recent evidence suggests that variation in spatially based cognitive abilities is reflected in the morphology of the hippocampus (Hp), the region of the brain involved in spatial memory. Moreover, recent work on this region establishes a dynamic link between brain plasticity and cognitive experiences both across populations and within individuals. However, the mechanisms involved in neurological changes as a result of differential space use and the reversibility of such effects are unknown. Using a house sparrow (Passer domesticus) model, we experimentally manipulated the space available to birds, testing the hypothesis that reductions in dendritic branching is associated with reduced Hp volume and that such reductions in volume are reversible. We found that reduced spatial availability associated with captivity had a profound and significant reduction in sparrow hippocampal volumes, which was highly correlated with the total length of dendrites in the region. This result suggests that changes to the dendritic structure of neurons may, in part, explain volumetric reductions in region size associated with captivity. In addition, small changes in available space even within captivity produced significant changes in the spine structure on Hp dendrites. These reductions were reversible following increased spatial opportunities. Overall, these results are consistent with the hypothesis that reductions to the Hp in captivity, often assumed to reflect a deleterious process, may be adaptive and a consequence of the trade-off between cognitive and energetic demands. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 93-101, 2017.

Microhabitat selection in the common lizard: implications of biotic interactions, age, sex, local processes, and model transferability among populations.

Modeling species' habitat requirements are crucial to assess impacts of global change, for conservation efforts and to test mechanisms driving species presence. While the influence of abiotic factors has been widely examined, the importance of biotic factors and biotic interactions, and the potential implications of local processes are not well understood. Testing their importance requires additional knowledge and analyses at local habitat scale. Here, we recorded the locations of species presence at the microhabitat scale and measured abiotic and biotic parameters in three different common lizard (Zootoca vivipara) populations using a standardized sampling protocol. Thereafter, space use models and cross‐evaluations among populations were run to infer local processes and estimate the importance of biotic parameters, biotic interactions, sex, and age. Biotic parameters explained more variation than abiotic parameters, and intraspecific interactions significantly predicted the spatial distribution. Significant differences among populations in the relationship between abiotic parameters and lizard distribution, and the greater model transferability within populations than between populations are in line with effects predicted by local adaptation and/or phenotypic plasticity. These results underline the importance of including biotic parameters and biotic interactions in space use models at the population level. There were significant differences in space use between sexes, and between adults and yearlings, the latter showing no association with the measured parameters. Consequently, predictive habitat models at the population level taking into account different sexes and age classes are required to understand a specie's ecological requirements and to allow for precise conservation strategies. Our study therefore stresses that future predictive habitat models at the population level and their transferability should take these parameters into account.

Spatial interactions between sympatric carnivores: asymmetric avoidance of an intraguild predator.

Interactions between intraguild species that act as both competitors and predator–prey can be especially complex. We studied patterns of space use by the black-footed ferret (Mustela nigripes), a prairie dog (Cynomys spp.) specialist, and the American badger (Taxidea taxus), a larger generalist carnivore that competes for prairie dogs and is known to kill ferrets. We expected that ferrets would spatially avoid badgers because of the risk of predation, that these patterns of avoidance might differ between sexes and age classes, and that the availability of food and space might influence these relationships. We used location data from 60 ferrets and 15 badgers to model the influence of extrinsic factors (prairie dog density and colony size) and intrinsic factors (sex, age) on patterns of space use by ferrets in relation to space use by different sex and age categories of badgers. We documented asymmetric patterns of avoidance of badgers by ferrets based on the sex of both species. Female ferrets avoided adult female badgers, but not male badgers, and male ferrets exhibited less avoidance than female ferrets. Additionally, avoidance decreased with increasing densities of prairie dogs. We suggest that intersexual differences in space use by badgers create varying distributions of predation risk that are perceived by the smaller carnivore (ferrets) and that females respond more sensitively than males to that risk. This work advances understanding about how competing species coexist and suggests that including information on both intrinsic and extrinsic factors might improve our understanding of behavioral interactions between sympatric species.

Comparing Interaction and Use of Space in Traditional and Innovative Classrooms

Despite myriad changes to language teaching methods over time, university-level classroom spaces have largely remained the same—until now. Recent innovations in classroom space design center on technological advances, include movable furniture and coffee-shop style rooms, and are believed to facilitate language learning in several ways. Specifically, compared to traditional classrooms, innovative spaces are designed in the hope of decreasing pre-task set up, increasing student-centered interaction, and facilitating collaborative work with multiple partners—features believed to be important for classroom learning. However, whether or not such features are present in these innovative spaces, or more so than in traditional classrooms, has yet to be tested empirically. This study set out to compare student interaction and the use of space in traditional and innovative classrooms, examining the presence of the aforementioned features. Data collected from university Spanish language and linguistic courses demonstrate that while some differences in use of space and interaction were observed when lessons in traditional and innovative classrooms were compared, notable differences were only present when the instructor was teaching all sections of a course in an innovative classroom and had adapted his/her lesson plans accordingly. Implications for language teaching, instructed language acquisition, and classroom space design are discussed.

Somewhere to hide: Home range and habitat selection of cheetahs in an arid, enclosed system

The decline in cheetah (Acinonyx jubatus) numbers during the last century has been severe, and fenced reserves may pose as a conservation option for the continued survival of this species. Understanding the use of space within these systems, however, is imperative for their management. Home range (95% Kernel Utilization Distributions) and use of space (Resource selection function models) for cheetahs reintroduced into a small (284 km2), arid, fenced national park was analysed. On average male home range size (139.94 km2) was smaller than female home range size (170.29 km2). Cheetahs did not use the space randomly and variables which aid hunting strategies appear to be important. Despite the chemical contraception of females and absence of competitively superior predators, differences in space use between male and female cheetahs were still observed. The factors that have been used to previously describe these differences were not present in this system, and this could therefore indicate the importance of additional factors such as the availability of prey and that perhaps the evolutionary history of the species results in a form of instinctual behaviour. The study demonstrates the adaptability of the species and if managed appropriately enclosed reserves can act as a population source for cheetahs.

Daily, seasonal, and annual variations in individual home-range overlap of two sympatric species of deer

Behavioural tactics of animals are determined by both environmental and social factors. Among nonmigratory ungulates, most home-range studies focused either on the effect of environmental variables on home-range size or on the overlap between home ranges of different individuals. Here, as rarely in previous studies, we aim to identify the dynamics of the home range of a given individual, involving variation in home-range size and home-range overlap between periods, for two resident populations of contrasting species: red deer (Cervus elaphus L., 1758) and roe deer (Capreolus capreolus (L., 1758)). In both species, yearly and seasonal home-range fidelity was high and constant (mean of 64% in red deer and mean of 66% in roe deer), possibly because of benefits accruing from knowledge of spatial distribution of food resources and refugia. Home range in winter, when food availability was low, was larger than other seasonal home ranges for both species. Differences in body size between red deer and roe deer accounted for observed between-species differences in space use, especially when the species were active at night. Our study clearly demonstrates that patterns of variation in home-range size are similar; however, between-species differences in body size lead to differential patterns of home-range size and fidelity.

Examination of fine‐scale spatial‐temporal overlap and segregation between two closely related congeners Gadus morhua and Gadus ogac in coastal Newfoundland

The spatial and temporal movement patterns of sympatric juvenile Atlantic cod Gadus morhua and Greenland cod Gadus ogac were studied using high-resolution radio-acoustic positioning in a coastal area of Newfoundland during the summers of 2009 and 2010. A total of 20 fish (10 G. ogac and 10 G. morhua) were equipped with acoustic transmitters and monitored for periods up to 23 days. Most fishes showed high site fidelity with mean residence times of 12·4 (G. morhua) and 14·4 days (G. ogac). A few individuals showed a transient use of the study area, ranging distances up to c. 4 km. Mean daily home ranges [95% kernel utilization distributions (KUDs)] and core activity areas were significantly larger for G. morhua (3·8 and 0·5 ha) than for G. ogac (2·7 and 0·3 ha). Home ranges were not related to total length (LT ) for G. morhua but showed a weak positive relationship for G. ogac. Gadus morhua occupied larger areas during the day while G. ogac occupied slightly larger areas at night. Mean rates of movement for G. ogac and G. morhua ranged from 0·83 to 1·24 and 0·76 to 1·76 LT s(-1) , respectively, and were highest during crepuscular periods. Overall, G. morhua were wider ranging, moved at faster rates and were active throughout the diel cycle compared to G. ogac of the same size. It is suggested that differential use of space and activity periods plays an important role in the successful coexistence of these two species.

Individuality in captive and field measures of behavior and space use in wild muskrat (Ondatra zibethicus)

The role of individual behavioral tendencies in wild populations remains largely unstudied, especially in mammals, despite its potential ecological importance. We examined whether individual variation in muskrat (Ondatra zibethicus) behavior in a captive novel environment correlates with other measures of behavior and habitat use. We compared the novel environment assay behavior with handling docility and trap habitat for all animals. We radio-collared subadults to look for correlation between assay behavior, summer space use, trappability and likelihood of autumn dispersal. In the novel environment test, we found many muskrat did not exit the shelter during the test. Muskrat that entered the arena showed activity and boldness/emotionality axes similar to behaviors identified in other taxa in similar tests. Participation in entering the arena appears to be related to boldness rather than activity. Both participation and boldness were lower in subadults and higher in males. Neither activity nor boldness of participants in the novel arena was correlated to handling docility, suggesting that such measures would not be interchangeable for evaluating muskrat behavioral tendencies. None of these behaviors related to fine-scale habitat use as reflected by the capture site. In subadults they did not relate to field measures of home range composition, trappability or autumn dispersal, and there is only a suggestion of a positive correlation between captive activity and home range size, although small sample size limits the power of these subadult analyses. Muskrat vary in their behavioral responses in captivity, but there is no strong indication that this variation reflects differences in space use in the wild.

Assessing the Status of Wild Felids in a Highly-Disturbed Commercial Forest Reserve in Borneo and the Implications for Camera Trap Survey Design

The proliferation of camera-trapping studies has led to a spate of extensions in the known distributions of many wild cat species, not least in Borneo. However, we still do not have a clear picture of the spatial patterns of felid abundance in Southeast Asia, particularly with respect to the large areas of highly-disturbed habitat. An important obstacle to increasing the usefulness of camera trap data is the widespread practice of setting cameras at non-random locations. Non-random deployment interacts with non-random space-use by animals, causing biases in our inferences about relative abundance from detection frequencies alone. This may be a particular problem if surveys do not adequately sample the full range of habitat features present in a study region. Using camera-trapping records and incidental sightings from the Kalabakan Forest Reserve, Sabah, Malaysian Borneo, we aimed to assess the relative abundance of felid species in highly-disturbed forest, as well as investigate felid space-use and the potential for biases resulting from non-random sampling. Although the area has been intensively logged over three decades, it was found to still retain the full complement of Bornean felids, including the bay cat Pardofelis badia, a poorly known Bornean endemic. Camera-trapping using strictly random locations detected four of the five Bornean felid species and revealed inter- and intra-specific differences in space-use. We compare our results with an extensive dataset of >1,200 felid records from previous camera-trapping studies and show that the relative abundance of the bay cat, in particular, may have previously been underestimated due to the use of non-random survey locations. Further surveys for this species using random locations will be crucial in determining its conservation status. We advocate the more wide-spread use of random survey locations in future camera-trapping surveys in order to increase the robustness and generality of inferences that can be made.

Tecnología lítica y uso diferencial del espacio en Estancia La Suiza, San Luis, Argentina

El trabajo pretende contribuir, desde la perspectiva de la organización de la tecnología, al conocimiento de las ocupaciones cazadoras-recolectoras que habitaron las inmediaciones de la Sierra de la Estanzuela, en la provincia de San Luis, Argentina. Se explican cómo fueron las secuencias de producción de herramientas en los sitios de la localidad arqueológica Estancia La Suiza, a partir del análisis de los materiales líticos recuperados en excavación y prospecciones sistemáticas. Las metodologías propuestas para abordar este estudio corresponden al análisis nodular y más específicamente a una combinación del análisis tipológico y no tipológico.Los resultados permiten interpretar que en esta localidad hubo un uso diferencial del espacio, particularmente en dos sitios que son Estancia La Suiza 2 y Estancia La Suiza 3.

Differences in space use and habitat selection between captive‐bred and wild‐born houbara bustards in Saudi Arabia: results from a long‐term reintroduction program

AbstractIn light of widespread declines of houbara bustard Chlamydotis macqueenii populations across its extant range, captive breeding has emerged as a viable option for regenerating viable populations of houbaras in addition to limiting hunting pressure, habitat management and amelioration of predation pressure. Although reintroductions of captive‐bred houbaras have been carried out in many regions in recent years, information on differences in ranging behavior and habitat selection between captive‐bred and wild‐born houbaras is lacking. In this study, we utilized radiotelemetry data spanning 13 years to assess differences in home range use and habitat selection by houbara bustards in the Mahazat as‐Sayd reserve in Saudi Arabia. The mean (±standard error of the estimate) annual home range size, estimated using the Kernel density method, was 307.76 ± 15.91 km2, and did not differ significantly between genders. Annual home ranges of wild‐born houbaras were however larger than those of their captive‐born counterparts (wild‐born: 423.77 ± 62.66 km2, captive‐bred: 299.31 ± 16.39 km2). Rainy season home ranges were the largest (279.29 ± 27.75 km2) followed by winter home ranges (245.79 ± 19.19 km2) and summer home ranges (110.51 ± 8.91 km2) indicating larger‐scale movements of houbaras when forage was available. Seasonal home ranges did not differ significantly between wild‐born or captive‐bred houbaras. Analysis of habitat selection patterns using the distance‐based method revealed consistent patterns of habitat preferences across years and seasons and between genders, ages and whether the bird was captive‐bred or wild‐born. Results indicate that scrub forms the most preferred habitat for houbaras, and should be conserved for the population welfare of the houbara in Saudi Arabia.

Differences in Space Use by Common Ravens in Relation to Sex, Breeding Status, and Kinship

Abstract. Group differences in avian space use relate to group differences in resource use and demographic parameters. However, studies that consider year-round, intraspecific variation in the space use of noncooperatively breeding species are relatively rare. A greater understanding of factors relating to intraspecific variation in space use is especially important for managing human-subsidized predators, such as the Common Raven (Corvus corax). We hypothesized that sex, sociality, and the distribution of bonanzas of food should influence year-round space use by breeding and nonbreeding Common Ravens on the Olympic Peninsula of Washington State. We detected differences in space use between breeders and nonbreeders but not between the sexes. Breeders shared little space with their neighbors and displayed strong site fidelity, except in the fall and winter or after the death of a mate, when some breeding ravens moved extensively. Nonbreeders moved widely, were more gregarious, and their home ranges interse...

Sexual and seasonal differences of space use in Alpine chamois

In spite of its wide distribution, little information has been published on factors affecting space use of northern chamois Rupicapra rupicapra. We radio-tracked 12 (≥ 4 years old) adult male and nine adult female chamois, for 2 years (from April to December), in an area of the south-western Italian Alps. Eight males occupied stable and small home ranges (“resident” males), while four moved between seasonal areas (“migrant” males). Residents showed smaller, stable home ranges, at lower altitudes than those of adult females, and selected forest, scrub, bush and meadow, avoiding rocks and scree. Females increased home range size in July-August, when they moved to rocky areas at the higher altitudes, and decreased it in November-December, at rut time. In spring and autumn, females selected both meadows and larch forest/scrub. Sexual and seasonal differences in space use, which reflected a marked sexual segregation, may have been linked to energetic and mating requirements, with females selecting high-quality feeding areas because of their energy demands during gestation and lactation. From spring to autumn, males remained at lower altitudes, in lower-quality habitats, only visited by females in the mating season.

Developing a deeper understanding of animal movements and spatial dynamics through novel application of network analyses

Summary1. Determining how animals move within their environment is a fundamental knowledge that contributes to effective management and conservation. Continuous ‘round‐the‐clock’ animal movement data are frequently gathered using biotelemetry technology, providing discrete data packages on the presence–absence of animals at known locations through time. Current analyses of such data do not generally account for the interconnectivity of locations as animals move between them and consequently do not integrate graphically or statistically a temporal component to spatial changes.2. Here, we describe the novel application of network analyses to electronic tag data whereby nodes represent locations and edges the movements of individuals. We demonstrate some of the descriptive and quantitative approaches for determining how an animal’s movement interconnects home range habitats. Telemetry data from arrays of recorders provide movement data of individual animals, and as examples of the method proposed, we examine the movements of two distinct shark species, the small‐spotted catshark (Scyliorhinus canicula) and the Caribbean reef shark (Carcharhinus perezi). In doing so, we consider both local and global network properties from an animal movement perspective and simulate the effects of node disruption as a proxy for habitat disturbance.3. Comparative visual representations of two catshark movement networks suggest, for example, potential differences in space use. Multiple regression quadratic assignment procedure shows that habitat is a significant predictor of movement behaviour.4. Null modelling ofC. perezimovement data, corrected for the spatial restriction of static nodes, demonstrated a significant, non‐random distribution of directed movements among sites. Additionally, the connectivity of this animal’s movement network is significantly reduced through targeted disruption of a site of high centrality but not through disruption of a randomly selected site.5. Network theory is a well‐established theoretical framework and its integration into the fast developing field of animal movement and telemetry might improve significantly how we interpret animal space use from electronically recorded data. This technique has potentially wide application in animal behaviour but may also inform the management of habitat harbouring threatened or endangered species via the simulation, modelling and intuitive visualisation of animal movement interactions.

Effects of human activity on space use and movement patterns of female Elk

AbstractIt is important to consider how human activity might influence behavior (e.g., space use and movement) in animals because such influences could have consequences for animal distribution or population performance. We documented and compared annual space use and daily movement patterns (i.e., movement distance and tortuosity) of female elk (Cervus elaphus) relative to human activity associated with development of energy resources in Colorado and New Mexico, USA, from 2006 to 2010. We analyzed data on 145 female elk fitted with global positioning system collars. While controlling for elevation, slope, and distance to anthropogenic features and vegetative cover, we found that proximity to the gas field generally was associated with smaller home ranges, more complex movement paths (i.e., greater tortuosity) and longer distance moved over a 3‐hr period (during most seasons). Comparing elk inside of the gas field to those outside of the gas field revealed differences in space use and movement patterns at varying levels of human activity. These differences likely reflected behavior by which elk in industrial areas attempted to minimize contact with sources of human activity; whereas, elk using both industrial and nonindustrial areas exhibited behavior that could be considered escape strategies (i.e., familiarity and use of large spatial extents, increased movement distance, and linear movement paths) in response to seemingly unpredictable levels of human activity due to their use of multiple areas. Understanding such behavioral responses informs efforts to minimize effects of human activity on animal populations. © 2011 The Wildlife Society.

Population regulation of territorial species: both site dependence and interference mechanisms matter

Spatial patterns of site occupancy are commonly driven by habitat heterogeneity and are thought to shape population dynamics through a site-dependent regulatory mechanism. When examining this, however, most studies have only focused on a single vital rate (reproduction), and little is known about how space effectively contributes to the regulation of population dynamics. We investigated the underlying mechanisms driving density-dependent processes in vital rates in a Mauritius kestrel population where almost every individual was monitored. Different mechanisms acted on different vital rates, with breeding success regulated by site dependence (differential use of space) and juvenile survival by interference (density-dependent competition for resources). Although territorial species are frequently assumed to be regulated through site dependence, we show that interference was the key regulatory mechanism in this population. Our integrated approach demonstrates that the presence of spatial processes regarding one trait does not mean that they necessarily play an important role in regulating population growth, and demonstrates the complexity of the regulatory process.

The interpretation of habitat preference metrics under use–availability designs

Models of habitat preference are widely used to quantify animal-habitat relationships, to describe and predict differential space use by animals, and to identify habitat that is important to an animal (i.e. that is assumed to influence fitness). Quantifying habitat preference involves the statistical comparison of samples of habitat use and availability. Preference is therefore contingent upon both of these samples. The inferences that can be made from use versus availability designs are influenced by subjectivity in defining what is available to the animal, the problem of quantifying the accessibility of available resources and the framework in which preference is modelled. Here, we describe these issues, document the conditional nature of preference and establish the limits of inferences that can be drawn from these analyses. We argue that preference is not interpretable as reflecting the intrinsic behavioural motivations of the animal, that estimates of preference are not directly comparable among different samples of availability and that preference is not necessarily correlated with the value of habitat to the animal. We also suggest that preference is context-dependent and that functional responses in preference resulting from changing availability are expected. We conclude by describing advances in analytical methods that begin to resolve these issues.

Determinants of home range and activity in two semi‐aquatic lizards

AbstractBy living in close proximity to waterbodies, semi‐aquatic varanids may be able to sustain activity and maintain relatively smaller home ranges than their terrestrial counterparts because of access to important resources (food and water) that are less abundant in terrestrial systems during dry seasons. The factors influencing home range and movement were examined in two semi‐aquatic Australian varanids, Varanus mertensi and Varanus indicus. We used radio‐telemetry and mark–recapture techniques to examine differences in space use between sexes, seasons and body sizes in the top end of the Northern Territory of Australia. Both V. mertensi and V. indicus were active throughout the year, unlike terrestrial varanids in this region. Varanus indicus had small home ranges when compared with other similar sized varanids, whereas the home ranges of V. mertensi varied substantially. Body size influenced the home range of V. indicus, with larger animals having larger home ranges, but not for V. mertensi. An interaction between body size and gender influenced the distance V. indicus moved, whereas interactions between body size, gender and seasonality all influenced the distance that V. mertensi moved.