Differences In Home Range Size Research Articles

Investigating the effects of landscape productivity on the spatial ecology of a threatened marsupial inside feral predator exclosures

AbstractLandscape productivity and resource dispersion are key drivers of the movement patterns of many species. In less productive environments, home ranges are generally larger as individuals travel further to access resources. The greater bilby (Macrotis lagotis) has been reintroduced to several feral predator exclosures to reduce their extinction risk. Understanding how landscape productivity and resource dispersion influence bilby space use is critical to enable effective management of populations in exclosures. At two exclosures, we tested three hypotheses: 1. Bilbies would preferentially utilize habitats with sandy substrates (<20% clay content), as they are suitable for digging burrows and foraging pits; 2. Home ranges would be larger at the arid site compared to the semi‐arid site due to lower productivity and patchier distribution of preferred habitats; and 3. Bilbies would travel further each night at the arid site to access preferred habitats. Rainfall was used as an indicator of productivity, and dispersion of preferred habitats as an indicator of resource dispersion. The study was undertaken during average rainfall conditions and under similar bilby population densities at both sites. GPS loggers recorded home ranges and movements of 10 bilbies at the arid site, and 11 bilbies at the semi‐arid site. Seventeen of the 21 bilbies preferentially utilized habitats with sandy substrates, which were less abundant at the arid site. There were no significant differences in home range size or nightly movements between the sites for either sex. We suggest the average rainfall conditions at both sites, and the dietary flexibility of bilbies, supported the maintenance of relatively small and stable home ranges (particularly for females). The effects of landscape productivity and resource dispersion on bilby space use are more likely to be evident during extended periods of below average rainfall. Bilby home range studies during low rainfall conditions (e.g. drought) are required for the effective, long‐term management of exclosure populations.

A window into the forest: post‐release behaviour of rehabilitated Bornean sun bears Helarctos malayanus euryspilus in Sabah, Malaysia

As the number of threatened wildlife species increases globally, captive rehabilitation and release of wild caught animals plays an increasingly significant role in conservation efforts, particularly where poaching threatens wild populations. Sun bear Helarctos malayanus populations are decreasing globally, with habitat loss and fragmentation and poaching as key threats to the species. This study aimed to assess post‐release behaviour of rehabilitated sun bears (n = 12) using GPS‐collar data to inform ongoing efforts to rehabilitate wild caught bears. We assessed spatial patterns of movement using kernel density estimates and utilisation distributions. We utilised an information theory (IT) and generalised linear modelling approach to assess temporal patterns of sun bear movement (n = 9). Post‐release home range estimates (mean = 56.68 km2, range:1.9–202.4) and behaviour varied widely between bears, with no significant difference in home range size between males (n = 3) and females (n = 6). Home ranges of most bears stabilised within the first month. Bears that were rehabilitated and released together did not spend a significant amount of time together following release. Bears were most active during daytime hours and most established a post‐release home range encompassing the riverside. The ultimate success of the releases is unknown, due to collar malfunction and damage, and the inaccessibility of the study terrain. We find that future releases of sun bears would benefit from soft‐release and in situ rehabilitation techniques. This study provides important insights into the complexity of bear reintroductions informing future rehabilitation and releases for threatened bear species.

How does an urban landscape influence spatiotemporal ecology of South American coatis (Nasua nasua)?

Abstract Increasing urbanization and consequent habitat fragmentation and loss call for studies of the influence of urbanization on native fauna. South American Coati (Procyonidae: Nasua nasua) live in groups and are common in urban areas of South America. Here, we aimed to understand how coatis occupy and select space, and whether they change their circadian activity in an urban environment. We estimated home range sizes, verified any overlap, and evaluated the effects of sex and weight on home range size. We also described coati activity patterns associated with habitat selection. Animals established their home ranges only within the study area, with few exploratory exits to surrounding areas. Furthermore, our home range estimates of 0.66 km2 are lower than previously found in natural habitats. We did not observe an effect of sex or weight on home range size. Coatis predominantly selected forested areas and explored houses only early in the morning. We suggest that this demonstrates the need for forested areas for survival of the species. Regarding activity patterns, coatis were active only during the day, as described for the species in its natural environment. Human barriers—in addition to human refuse that serves as food—could reduce the home range sizes. Our data demonstrate differences in home range size, but not circadian activity or habitat selection when compared to coatis in their natural environment.

Still little evidence sex differences in spatial navigation are evolutionary adaptations.

A putative male advantage in wayfinding ability is the most widely documented sex difference in human cognition and has also been observed in other animals. The common interpretation, the sex-specific adaptation hypothesis, posits that this male advantage evolved as an adaptive response to sex differences in home range size. A previous study a decade ago tested this hypothesis by comparing sex differences in home range size and spatial ability among 11 species and found no relationship. However, the study was limited by the small sample size, the lack of species with a larger female home range and the lack of non-Western human data. The present study represents an update that addresses all of these limitations, including data from 10 more species and from human subsistence cultures. Consistent with the previous result, we found little evidence that sex differences in spatial navigation and home range size are related. We conclude that sex differences in spatial ability are more likely due to experiential factors and/or unselected biological side effects, rather than functional outcomes of natural selection.

Trabecular bone morphology in big cats reflects the complex diversity of limb use but not home range size or daily travel distance.

A relationship exists between mechanical loading and bone morphology. Although studies show a relationship between trabecular bone morphology and locomotor strategy in mammals, none of them have studied trabecular bone morphology in felid species occupying disparate and overlapping habitats. We investigate trabecular bone volume fraction (BVF) in the femoral and humeral heads, and distal tibia of four felid species (mountain lions, jaguars, cheetahs, and leopards) to identify whether there is a relationship between BVF and locomotor behavior. This study's goals are to identify whether felid species with high daily travel distance or large home range size have greater BVF compared with those with small daily travel distance or home range size, and whether BVF is correlated among the three elements of the fore and hindlimb studied. We quantified BVF in micro- and peripheral computed tomography images and found no significant differences across species in the femoral and humeral head (p > 0.05). However, in the distal tibia, results showed that leopards, mountain lions, and cheetahs have significantly greater (p < 0.05) BVF than jaguars. Despite differences in home range size and daily travel distance, the proximal elements did not reflect differences in BVF; however, the distal-most element did, suggesting decreased loading among jaguars. These findings suggest that the observed pattern of trabecular bone morphology is potentially due to the diversity in locomotor strategy of the forelimb. Additionally, these results imply that neither home range size nor daily travel distance are clear indicators of activity levels. A cautious approach is warranted in studying how loading influences trabecular morphology.

Home range ecology of Indian rock pythons (Python molurus) in Sathyamangalam and Mudumalai Tiger Reserves, Tamil Nadu, Southern India

The Indian rock pythons (Python molurus) are classified as a near-threatened snake species by the International Union for the Conservation of Nature and Natural Resources (IUCN); they are native to the Indian subcontinent and have experienced population declines caused primarily by poaching and habitat loss. We hand-captured the 14 rock pythons from villages, agricultural lands, and core forests to examine the species' home ranges. We later released/translocated them in different kilometer ranges at the Tiger Reserves. From December 2018 to December 2020, we obtained 401 radio-telemetry locations, with an average tracking duration of (444 ± 212 days), and a mean of 29 ± SD 16 data points per individual. We quantified home ranges and measured morphometric and ecological factors (sex, body size, and location) associated with intraspecific differences in home range size. We analyzed the home ranges of rock pythons using Auto correlated Kernel Density Estimates (AKDE). AKDEs can account for the auto-correlated nature of animal movement data and mitigate against biases stemming from inconsistent tracking time lags. Home range size varied from 1.4 ha to 8.1 km2 and averaged 4.2 km2. Differences in home range sizes could not be connected to body mass. Initial indications suggest that rock python home ranges are larger than other pythons.

Sex and Season Affect Cortical Volumes in Free-Living Western Fence Lizards, Sceloporus occidentalis

The hippocampus plays an important role in spatial navigation and spatial learning across a variety of vertebrate species. Sex and seasonal differences in space use and behavior are known to affect hippocampal volume. Similarly, territoriality and differences in home range size are known to affect the volume of the reptile hippocampal homologues, the medial and dorsal cortices (MC, DC). However, studies have almost exclusively investigated males and little is known about sex or seasonal differences in MC and/or DC volumes in lizards. Here, we are the first to simultaneously examine sex and seasonal differences in MC and DC volumes in a wild lizard population. In Sceloporus occidentalis, males display territorial behaviors that are more pronounced during the breeding season. Given this sex difference in behavioral ecology, we expected males to have larger MC and/or DC volumes than females and for this difference to be most pronounced during the breeding season when territorial behavior is increased. Male and female S. occidentalis were captured from the wild during the breeding season and the post-breeding season and were sacrificed within 2 days of capture. Brains were collected and processed for histology. Cresyl-violet-stained sections were used to quantify brain region volumes. In these lizards, breeding females had larger DC volumes than breeding males and nonbreeding females. There was no sex or seasonal difference in MC volumes. Differences in spatial navigation in these lizards may involve aspects of spatial memory related to breeding other than territoriality that affect plasticity of the DC. This study highlights the importance of investigating sex differences and including females in studies of spatial ecology and neuroplasticity.

Impact of test, vaccinate and remove protocol on home ranges and nightly movements of badgers in a medium density population

In the British Isles, the European badger (Meles meles) is thought to be the primary wildlife reservoir of bovine tuberculosis (bTB), an endemic disease in cattle. Test, vaccinate or remove (‘TVR’) of bTB test-positive badgers, has been suggested to be a potentially useful protocol to reduce bTB incidence in cattle. However, the practice of removing or culling badgers is controversial both for ethical reasons and because there is no consistent observed effect on bTB levels in cattle. While removing badgers reduces population density, it may also result in disruption of their social behaviour, increase their ranging, and lead to greater intra- and inter-species bTB transmission. This effect has been recorded in high badger density areas, such as in southwest England. However, little is known about how TVR affects the behaviour and movement of badgers within a medium density population, such as those that occur in Northern Ireland (NI), which the current study aimed to examine. During 2014–2017, badger ranging behaviours were examined prior to and during a TVR protocol in NI. Nightly distances travelled by 38 individuals were determined using Global Positioning System (GPS) measurements of animal tracks and GPS-enhanced dead-reckoned tracks. The latter was calculated using GPS, tri-axial accelerometer and tri-axial magnetometer data loggers attached to animals. Home range and core home range size were measured using 95% and 50% autocorrelated kernel density estimates, respectively, based on location fixes. TVR was not associated with measured increases in either distances travelled per night (mean = 3.31 ± 2.64 km) or home range size (95% mean = 1.56 ± 0.62 km2, 50% mean = 0.39 ± 0.62 km2) over the four years of study. However, following trapping, mean distances travelled per night increased by up to 44% eight days post capture. Findings differ from those observed in higher density badger populations in England, in which badger ranging increased following culling. Whilst we did not assess behaviours of individual badgers, possible reasons why no differences in home range size were observed include higher inherent ‘social fluidity’ in Irish populations whereby movements are less restricted by habitat saturation and/or that the numbers removed did not reach a threshold that might induce increases in ranging behaviour. Nevertheless, short-term behavioural disruption from trapping was observed, which led to significant increases in the movements of individual animals within their home range. Whether or not TVR may alter badger behaviours remains to be seen, but it would be better to utilise solutions such as oral vaccination of badgers and/or cattle as well as increased biosecurity to limit bTB transmission, which may be less likely to cause interference and thereby reduce the likelihood of bTB transmission.

Anthropogenic subsidies influence resource use during a mange epizootic in a desert coyote population.

Colonization of urban areas by synanthropic wildlife introduces novel and complex alterations to established ecological processes, including the emergence and spread of infectious diseases. Aggregation at urban resources can increase disease transfer, with wide-ranging species potentially infecting outlying populations. The garrison at the National Training Center, Fort Irwin, California, USA, was recently colonized by mange-infected coyotes (Canis latrans) that also use the surrounding Mojave Desert. This situation provided an ideal opportunity to examine the effects of urban resources on disease dynamics. We evaluated seasonal space use and determined the influence of anthropogenic subsidies, water sources, and prey density on urban resource selection. We found no difference in home range size between healthy and infected individuals, but infected residents had considerably more spatial overlap with one another than healthy residents. All coyotes selected for anthropogenic subsidies during all seasons, while infected coyotes seasonally selected for urban water sources, and healthy coyotes seasonally selected for urban areas with greater densities of natural prey. These results suggest that while all coyotes were selecting for anthropogenic subsidies, infected resident coyotes demonstrated a greater tolerance for other conspecifics, which could be facilitating the horizontal transfer of sarcoptic mange to non-resident coyotes. Conversely, healthy coyotes also selected for natural prey and healthy residents exhibited a lack of spatial overlap with other coyotes suggesting they were not reliant on anthropogenic subsidies and were maintaining territories. Understanding the association between urban wildlife, zoonotic diseases, and urban resources can be critical in determining effective responses for mitigating future epizootics.

Home ranges of fossorial water voles (Arvicola amphibius) in urban grasslands.

Water voles (Arvicola amphibius) occur in urban areas in mainland Britain but relatively little is known about their ecology in these environments. In Scotland’s largest city Glasgow, fossorial water voles occupy areas of grassland, some of which may be faced with urban development. The aim of this study was to estimate the area of habitat required by water voles in these urban grasslands by determining their home range size and spatial overlap. Radio-tracking was undertaken at two grassland sites over 29 days during September to October 2018. The mean ± SD home range size of males was 881.4 ± 636.21 m2 (n=5, range 197.8 -1836.2) and 996.5 ± 643.45 m² (n=5, range=435.1 – 2044.6) for females. There was no difference in home range size between sexes or sites and no correlation with body mass. Where home ranges overlapped, the percentage area overlap was 37.4 ± 26.81%. These initial findings provide valuable information on spatial use of urban grasslands by water voles that will inform the management of habitats for this species.

Seasonal resource selection and movement ecology of free‐ranging horses in the western United States

AbstractUnderstanding factors driving resource selection and habitat use of different species is an important component of management and conservation. Feral horses (Equus caballus) are free ranging across various vegetation types in the western United States, yet few studies have quantified their resource selection and seasonal use. We conducted a study to determine effects of vegetation community, distance to water, and topographic variables on seasonal resource selection in 2 feral horse populations in Great Basin sagebrush (Artemisia spp.) ecosystems of west‐central Utah, USA: Conger Herd Management Area (HMA) and Frisco HMA. We deployed global positioning system (GPS) radio‐collars on 38 female horses and GPS‐transmitters braided and glued into the tail hair of 14 males, collecting locations every 2 hours for 1–4 years between 2016 and 2020. We calculated home range size and core use area of social groups (harems) and bachelor males using auto‐correlated kernel density estimators for each biologically defined season (breeding, fall, and winter) per study year. We examined seasonal home range size and overlap of harem groups and bachelor males and compared movement speed of bachelors and harems among seasons. We determined seasonal resource selection in a use‐availability framework using resource selection functions. We hypothesized that horses would select for areas of high herbaceous vegetation, that water would be a key variable in resource selection models like other equids, and home range size in winter would be largest because horses can eat snow for hydration and could therefore roam farther from surface water. Mean annual home range size was 103.12 ± 37.38 km2 (SD) for Conger harems and 117.47 ± 32.75 km2 for Frisco harems. At Conger there was no difference in home range size between harem groups and bachelor males, but home range size was smaller in winter than other seasons, whereas winter home range size at Frisco was larger than other seasons. Bachelor males moved at higher speeds than harems during all seasons, and harem groups from both populations had lower movement speeds in winter. Harem groups had distinct winter ranges with little overlap on breeding season ranges. In both populations, all horses selected for herbaceous vegetation types and avoided forest relative to shrubland throughout the year. Harems at Frisco were consistently located closer to water sources, whereas selection for water sources by Conger harems varied seasonally, with winter having the lowest selection. Harem groups at Conger had an average of 10.6% of their home ranges outside the HMA boundary and Frisco harems had up to 66.8% outside, likely because of the horseshoe shape of Frisco HMA in which shrub meadows (foraging areas) comprise the horseshoe center, which is outside the HMA. Our results highlight the importance of water sources, which were a key predictor of horse movement patterns in our study. We emphasize the utility of telemetry devices to understand resource selection of feral horses at a fine scale, enabling management to be more targeted and facilitate planning.

Very small collars: an evaluation of telemetry location estimators for small mammals

BackgroundFine-scale tracking of animals such as Peromyscus spp. is still done with micro-very high frequency collars due to the animal’s small size and habitat usage. In most cases, tracking micro-very high frequency collars requires manual telemetry, yet throughout the literature, there is little reporting of individual telemetry methods or error reporting for small mammal spatial analyses. Unfortunately, there is even less documentation and consensus on the best programs used to calculate fine-scale animal locations from compass azimuths. In this study, we present a strategy for collecting fine-scale spatial data on Peromyscus spp. as a model species for micro-very high frequency collars and assess multiple programmatic options and issues when calculating telemetry locations.ResultsMice were trapped from April to October 2018–2019 with Sherman traps in Howard County, Maryland, USA. Collars were placed on 61 mice, of which 31 were included in the analyses. We compared the two most cited location estimator programs in the literature, location of a signal software and Locate III, as well as the Sigloc package in program R. To assess the programmatic estimates of coordinates at a fine scale and examine programmatic impacts on different analyses, we created and compared minimum convex polygon and kernel density estimator home ranges from locations produced by each program. We found that 95% minimum convex polygon home range size significantly differed across all programs. However, we found more similarities in estimates across calculations of core home ranges. Kernel density estimator home ranges had similar patterns as the minimum convex polygon home ranges with significant differences in home range size for 95% and 50% contours. These differences likely resulted from different inclusion requirements of bearings for each program.ConclusionsThis study highlights how different location estimator programs could change the results of a small mammal study and emphasizes the need to calculate telemetry error and meticulously document the specific inputs and settings of the location estimator.

Trabecular bone morphology in felids reflects diversity in locomotor strategy but not home range size

A relationship exists between mechanical loading, and the resulting changes in bone morphology. When bones experience increased loading, they undergo change through bone modeling and remodeling in response to loading frequency and strain. Organisms with differing locomotor behaviors are distinguished by differences in limb bone morphology. In other words, an organisms’ biological structure such as limb morphology is adapted for its behavior including locomotor strategy. While there are studies showing a relationship between bone morphology and locomotor strategy in a myriad of taxa none of them have specifically investigated felid species occupying disparate geographical spaces. This study investigates trabecular bone morphology (bone volume fraction, BVF and degree of anisotropy, DA) in the femoral and humeral heads and distal tibia of four felid species to identify whether there is a relationship between these bone properties and their locomotor behavior. We test the hypotheses that felid species with large home ranges i.e., cougars and cheetahs will have significantly greater BVF than those with small home ranges (leopards and jaguars) in the forelimb than hindlimb and will exhibit greater DA because non‐primate mammals have greater vertical ground reaction forces on the fore‐than in the hindlimb. We found no significant differences across species in both the femoral and humeral BVF (p&gt;0.05). Results also showed that in the distal tibia, leopards, cougars and cheetahs have significantly greater (p&lt;0.05) BVF than jaguars. Additionally, humeral and distal tibia DA in the jaguars was significantly greater than in the femur. Interestingly, despite differences in home range size, the proximal limb elements do not reflect differences in BVF, however, the distal most element‐the tibia‐ suggests greater loading among jaguars. In the same vein, humeral and tibia suggest greater stereotypical loading among jaguars. The jaguar results are potentially due to the diversity in locomotor strategy rather than differences in home range size. This implies a cautious approach is warranted in studying how repeated loading influences trabecular morphology and places emphasis on investigating the diversity of locomotor behavior rather than overall loading.

Home range patterns of Helmeted Woodpecker (Celeus galeatus), Lineated Woodpecker (Dryocopus lineatus), and Robust Woodpecker (Campephilus robustus) in Misiones, Argentina, in a global perspective

Home range mapping studies of birds inform about area requirements and responses to land management as reflected by home range sizes and by resource selection within home ranges. Tracking studies of woodpeckers (<em>Picidae</em>) so far have been concentrated in temperate regions. In the subtropical Atlantic Forest of northeast Argentina, we assessed interspecific differences in home range sizes in old-growth forests and selectively logged forests of Helmeted Woodpecker (<em>Celeus galeatus</em>, a globally threatened species), Lineated Woodpecker (<em>Dryocopus lineatus</em>), and Robust Woodpecker (<em>Campephilus robustus</em>). Helmeted Woodpecker had larger breeding home ranges in selectively logged forests, averaging 105 ± 39 ha for pairs, versus 60 ± 13 ha in old-growth forests. Lineated Woodpecker breeding home ranges of pairs averaged 56 ± 22 ha, and those of Robust Woodpecker 43 ± 22 ha, with no differences between forest types. Helmeted Woodpeckers had an unusual separation between the home ranges of males and females in breeding pairs, with a mean area overlap of only 8% ± 9% near the nest tree, resulting in large home ranges for pairs. Helmeted Woodpecker and Robust Woodpecker individuals that were followed into the post-breeding stage had marked expansions of their home range sizes relative to breeding home ranges. To place our findings with Atlantic Forest woodpeckers in perspective we reviewed whether woodpecker home range sizes increase with latitude and body mass globally. For 29 populations of 22 woodpecker species, a power regression model with these factors explained 24.1% of variation in breeding home range sizes, with 17.1% of variation explained by latitude alone. Woodpecker species with larger home ranges than predicted values were three species of North American woodpeckers of coniferous forests, as well as the Helmeted Woodpecker. Our results of smaller home ranges in old-growth forests for the Helmeted Woodpecker affirm an association of this species with such forests. We urge the conservation of the few remaining tracts of old-growth Atlantic Forest and more restoration of logged forests to mature conditions.

Individual, sexual and temporal variation in the winter home range sizes of GPS-tagged Eurasian Curlews Numenius arquata

ABSTRACT Capsule: Eurasian Curlews Numenius arquata were faithful to foraging and roosting areas on their coastal wintering grounds, including a habitat creation site. Home range sizes were greater at night than during the day, and showed high inter-individual variability which was not related to sex. Aims: To examine factors affecting variation in the winter home range size of the largest European wader species: the near-threatened Eurasian Curlew Numenius arquata. Methods: We examined individual, sexual and temporal (day/night, seasonal and annual) variation in the size of the home ranges of 18 GPS tagged Curlews captured at two sites on the Humber Estuary, UK. Results: Home ranges were small (mean ± SD = 555.5 ± 557.9 ha) and varied slightly in size through the non-breeding season (September–March). We found some annual differences in home range size, and there was some evidence that home range size was greater at night compared to daytime. There was strong inter-individual variation in home range size, which was not related to the species’ sexual size dimorphism and thus potential differences in resource use. Conclusions: Our results highlight that wintering Curlews on the Humber Estuary maintain small home ranges which vary strongly between individuals. Knowledge of the home range size of wintering waders is vital to inform management responses to the potential impacts of environmental changes such as sea-level rise and improving the efficacy of compensatory habitats.

Spatio-temporal movement patterns and habitat choice of red foxes (Vulpes vulpes) and racoon dogs (Nyctereutes procyonoides) along the Wadden Sea coast

Wetlands such as the World Heritage Site in the Wadden Sea include important habitats for breeding waterbirds. Its saltmarshes and adjacent conservation polders are used by thousands of breeding birds. However, some alarming population declines have been recorded during recent decades and previous studies found indications that predation pressure from red foxes (Vulpes vulpes) and more recently from invasive racoon dogs (Nyctereutes procyonoides) played an important role. The current study aimed to assess habitat utilisation by foxes and racoon dogs along the coast of the Wadden Sea. We equipped 21 foxes and seven racoon dogs with GPS collars and recorded a total of 37,586 (mean: 2,088) GPS fixes during a total of 2,617 (mean: 145) equipment days for red foxes and 3,440 (mean: 573) GPS fixes during a total of 272 (mean: 45) equipment days for racoon dogs. Foxes showed high individual variability in Kernel 95% home range sizes, with a mean of 172.2 ha (range: 3 to 824 ha) and little overlap among territories. Males had significantly larger home ranges than females, and there were no differences in home range sizes between adults (n = 14) and young (n = 4). Racoon dogs had smaller home ranges than foxes (mean: 52.8 ha). The preferred habitat type of both predators during daytime was the conservation polders along the Wadden Sea, while foxes also selected saltmarshes during the night. In contrast, both species avoided farmland areas. Foxes showed 20% of their activity during daylight hours and spent this time largely in areas with dense vegetation cover. None of the tagged individuals entered areas with particularly high bird densities (i.e. Wadden Sea islands or Halligen). However, our data suggest that foxes and racoon dogs frequently make use of linear structures such as dykes and dams and patrol along the tide line for carcasses. This suggests that at least single individuals of both species are prone to enter islands that are connected by dams to the mainland.

Development and validation of a spatially-explicit agent-based model for space utilization by African savanna elephants (Loxodonta africana) based on determinants of movement

African elephants (Loxodonta africana) are well-studied and inhabit diverse landscapes that are being transformed by both humans and natural forces. Most tools currently in use are limited in their ability to predict how elephants will respond to novel changes in the environment. Individual-, or agent-based modeling (ABM), may extend current methods in addressing and predicting spatial responses to environmental conditions over time. We developed a spatially explicit agent-based model to simulate elephant space use and validated the model with movement data from elephants in Kruger National Park (KNP) and Chobe National Park (CNP). We simulated movement at an hourly scale, as this scale can reflect switches in elephant behavior due to changes in internal states and short-term responses to the local availability and distribution of critical resources, including forage, water, and shade. Known internal drivers of elephant movement, including perceived temperature and the time since an individual last visited a water source, were linked to the external environment through behavior-based movement rules. Simulations were run on model landscapes representing the wet season and the hot, dry season for both parks. The model outputs, including home range size, daily displacement distance, net displacement distance, and maximum distance traveled from a permanent water source, were evaluated through qualitative and quantitative comparisons to actual elephant movement data from both KNP and CNP. The ABM was successful in reproducing the differences in daily displacements between seasons in each park, and in distances traveled from a permanent water source between parks and seasons. Other movement characteristics, including differences in home range sizes and net daily displacements, were partially reproduced. Out of the all the statistical comparisons made between the empirical and simulated movement patterns, the majority were classified as discrepancies of medium or small effect size. We have shown that a resource-driven model with relatively simple decision rules generates trajectories with movement characteristics that are mostly comparable to those calculated from empirical data. Simulating hourly movement (as our model does) may be useful in predicting how finer-scale patterns of space use, such as those created by foraging movements, are influenced by finer spatio-temporal changes in the environment.

Using movement to inform conservation corridor design for Mojave desert tortoise

BackgroundPreserving corridors for movement and gene flow among populations can assist in the recovery of threatened and endangered species. As human activity continues to fragment habitats, characterizing natural corridors is important in establishing and maintaining connectivity corridors within the anthropogenic development matrix. The Mojave desert tortoise (Gopherus agassizii) is a threatened species occupying a variety of habitats in the Mojave and Colorado Deserts. Desert tortoises have been referred to as corridor-dwellers, and understanding how they move within suitable habitat can be crucial to defining corridors that will sustain sufficient gene flow to maintain connections among populations amidst the increases in human development.MethodsTo elucidate how tortoises traverse available habitat and interact with potentially inhospitable terrain and human infrastructure, we used GPS dataloggers to document fine-scale movement of individuals and estimate home ranges at ten study sites along the California/Nevada border. Our sites encompass a variety of habitats, including mountain passes that serve as important natural corridors connecting neighboring valleys, and are impacted by a variety of linear anthropogenic features. We used path selection functions to quantify tortoise movements and develop resistance surfaces based on landscape characteristics including natural features, anthropogenic alterations, and estimated home ranges with autocorrelated kernel density methods. Using the best supported path selection models and estimated home ranges, we determined characteristics of known natural corridors and compared them to mitigation corridors (remnant habitat patches) that have been integrated into land management decisions in the Ivanpah Valley.ResultsTortoises avoided areas of high slope and low perennial vegetation cover, avoided moving near low-density roads, and traveled along linear barriers (fences and flood control berms).ConclusionsWe found that mitigation corridors designated between solar facilities should be wide enough to retain home ranges and maintain function. Differences in home range size and movement resistance between our two natural mountain pass corridors align with differences in genetic connectivity, suggesting that not all natural corridors provide the same functionality. Furthermore, creation of mitigation corridors with fences may have unintended consequences and may function differently than natural corridors. Understanding characteristics of corridors with different functionality will help future managers ensure that connectivity is maintained among Mojave desert tortoise populations.

Home Range Size and Seasonal Variation in Habitat Use of Aye-Ayes (Daubentonia madagascariensis) in Torotorofotsy, Madagascar

Madagascar’s dramatic climatic fluctuations mean most lemurs adjust behaviors seasonally as resource availability fluctuates. Many lemurs will adopt one of two strategies, a resource maximizer or an area minimizer, when adjusting to seasonal shifts in resource availability. However, it is unknown if and how aye-aye (Daubentonia madagascariensis) ranging behavior is influenced by seasonality. We explored whether habitat use changed seasonally. We followed two aye-ayes, an adult male and an adult female, in the undisturbed forest of Torotorofotsy, Madagascar, from April 2012 to December 2017. We used instantaneous focal-animal sampling to collect behavioral data every 5 min and GPS locations every 20 min. We used the minimum convex polygon (MCP) to determine overall home range, and the Brownian bridge movement model (BBMM) to estimate overall and seasonal home range of the female aye-aye from November 2014 to October 2017. We used Wilcoxon signed-rank tests to determine whether there were significant differences in home range sizes between seasons across years and to examine whether there were seasonal differences in height of invertebrate foraging, generalized linear models to assess seasonal differences in travel rates and nesting locations, and χ² tests to determine whether there were differences in forest strata use when foraging on invertebrates. The male’s MCP home range was 2,586 ha, and the female’s MCP home range was 765 ha. The seasonal BBMM for the female varied between 443.6 and 1,010.0 ha, though infant rearing appears to have influenced these values. There were no significant differences in seasonal home range, travel rates, nesting locations, or height of invertebrate feeding. However, canopy level invertebrate foraging occurred more often than understory or ground levels. It appears aye-ayes in this undisturbed forest were not influenced by seasonal shifts and had larger home ranges than any previously reported. These findings may indicate that aye-ayes in an undisturbed forest are resource maximizers, closely linked to invertebrate assemblages.

Timing of Resource Availability Drives Divergent Social Systems and Home Range Dynamics in Ecologically Similar Tree Squirrels

Intraspecific variation in home range size has important implications for the distribution of animals across landscapes and the spatial structuring of population, community and ecosystem processes. Among species of similar trophic guild and body mass, differences in home range size can reflect extrinsic variables that exert divergent selective forces upon spacing behavior and social organization. We tested predictions about how resource availability and timing influence social system, home range size and territoriality in two tree squirrel species of similar size and ecological niches but that differ in foraging strategy and social organization. We estimated home range size and intraspecific home range core overlap in the Mt. Graham red squirrel (Tamiasciurus fremonti grahamensis; Arizona USA; MGRS) and the Eurasian red squirrel (Sciurus vulgaris; Alps, Italy; ERS) as functions of species, sex, season, and individual’s body mass. However, body mass did not explain differences found between the two species. We found MGRS home ranges being 3 times smaller with higher core area exclusivity compared to ERS in all seasons. In fact, territorial MGRS evolved in a system of brief resource pulses and are larder hoarders, whereas ERS experience prolonged resource availability and are non-territorial. Only male MGRSs increased their home range during the breeding season, reflecting interspecific differences in social organization and mating behavior. Male ERS home ranges always overlap with several females to enhance mating success, while male and female MGRS maintain nearly exclusive territories throughout the year. Only during spring and summer males temporarily leave their food-based territory to increase mating opportunities with neighboring estrus females. Home range comparisons between ecologically similar species emphasized the importance of divergent extrinsic factors in shaping variability in body size – home range size scaling relationships. Timing in resource availability influenced the social structure and space use in tree squirrels of similar body size, highlighting how the coevolution of arboreal squirrels with conifer tree species has shaped their natural history.