Minimum Convex Polygon Area Research Articles

Spatial proliferation of African swine fever virus in South Korea.

The African swine fever virus (ASFV) was first detected in South Korea on a pig farm in September 2019. Despite active preventive measures to control the spread of ASFV, outbreaks on pig farms and in wild boar have been increasing. In this study, we investigated the spatial contamination area using the minimum convex polygon (MCP) approach, and growth rate using a logistic diffusion model. On the basis of the ASFV outbreak locations recorded from September 17th, 2019, to May 20th, 2022, the MCP area for the second week was 618.41 km2 and expanded to 37959.67 km2 in the final week. The maximum asymptote of the logistic function was considered as the land area of South Korea, and we estimated logistic growth rates of 0.022 km2 per week and 0.094 km2 per month. Administrative bodies should implement preventive and quarantine measures for infectious diseases. The results of this study will be a reference for epidemiologists, ecologists, and policy makers and contribute to the establishment of appropriate quarantine measures for disease control and management.

Count me in: Leopard population density in an area of mixed land‐use, Eastern Cape, South Africa

Count me in: Leopard population density in an area of mixed land‐use, Eastern Cape, South Africa

Ecological drivers of helminth infection patterns in the Virunga Massif mountain gorilla population.

The Virunga Massif mountain gorilla population has been periodically monitored since the early 1970s, with gradually increasing effort. The population declined drastically in the 1970s, but the numbers stabilized in the 1980s. Since then, the population has been steadily increasing within their limited habitat fragment that is surrounded by a dense human population. We examined fecal samples collected during the Virunga 2015–2016 surveys in monitored and unmonitored gorilla groups and quantified strongylid and tapeworm infections using egg counts per gram to determine environmental and host factors that shape these helminth infections. We showed that higher strongylid infections were present in gorilla groups with smaller size of the 500-m buffered minimum-convex polygon (MCP) of detected nest sites per gorilla group, but in higher gorilla densities and inhabiting vegetation types occurring at higher elevations with higher precipitation and lower temperatures. On the contrary, the impact of monitoring (habituation) was minor, detected in tapeworms and only when in the interaction with environmental variables and MCP area. Our results suggest that the Virunga mountain gorilla population may be partially regulated by strongylid nematodes at higher gorilla densities. New health challenges are probably emerging among mountain gorillas because of the success of conservation efforts, as manifested by significant increases in gorilla numbers in recent decades, but few possibilities for the population expansion due to limited amounts of habitat.

Translocating Wild California Valley Quail to Texas: An Evaluation of Survival, Dispersal, Tracking Efficacy, and Roost Preference

Quail translocations are becoming increasingly popular in regions of suitable habitat where local quail populations have declined. In northeastern Texas, USA, northern bobwhite (Colinus virginianus) populations have drastically declined for over a century and have reached undetectable levels in many areas. As a result, the number of quail hunters and quail conservation funding have also declined. California valley quail (Callipepla californica; hereafter, valley quail) have increased across their range and have been translocated to many states and countries. Thus, the goal of this study was to determine whether translocating wild valley quail to Texas was feasible, and evaluate their survival, dispersal, roost location preference, and potential predator impacts. We translocated 748 wild valley quail from Idaho, USA to northeastern Texas in 2019 and 2020. We collected quail location data from very high frequency (VHF) and digital transmitters. Motion-triggered cameras, scent stations, simulated nests, and raptor transects were used to record predator presence and potential predator impacts. Survival of birds with tracking devices was 63% (VHF) in 2019, and 38.8% (VHF) and 92.5% (digital tag) in 2020. Survival was greater for quail with digital transmitters. Median dispersal distance was 633.5 m in 2019 and 246.6 m in 2020 for valley quail with VHF transmitters, and 310.4 m for quail with digital transmitters. Minimum convex polygon area medians were 4.3 ha in 2019 and 3.1 ha in 2020 for quail with VHF transmitters, and 16.1 ha in 2020 for quail with digital transmitters. Roost sites were primarily in young stands of oak trees. Median simulated nest survival was 2 days (minimum [min] = 1, interquartile range [IQR] = 2–5.4, maximum [max] = 23) in 2019, and 7.5 days (min = 2, IQR = 4.5–15.2, max = 23) in 2020. The most frequent mammalian predators observed were raccoons (Procyon lotor), feral hogs (Sus scrofa), and white-tailed deer (Odocoileus virginianus). Red-tailed hawks (Buteo jamaicensis) were the most frequent aerial predator. We completed the first documented translocation of wild California valley quail to Texas, demonstrating it is feasible. Future translocation may benefit from translocating more birds over a longer period of time, with more consistent methodology. The establishment of a sustainable population may require ≥7 years of translocation at a rate of 500 birds per year with >2,000 ha of suitable habitat.

Home Range and Nest Arrangement of the Siberian Flying Squirrel Pteromys volans in an Urban Edge, Northern Japan

Forest fragmentation by urbanizing and developing roads and fields is common in Japan; thus, the Siberian flying squirrel (Pteromys volans) population may decrease in the future. This study examined the effects of urbanization on P. volans by clarifying their home ranges and nest arrangements. Ten flying squirrels were captured and radio-telemetrically tracked from 2005 to 2007 in Obihiro City in eastern Hokkaido (Northern Japan). Males had significantly larger 100% MCP (minimum convex polygon) areas (mean ± SD; 6.5 ± 5.1 ha) and 95% MCP areas (3.6 ± 1.3 ha) than females (1.8 ± 1.0 ha and 1.0 ± 0.5 ha, respectively). Also the core area of males (1.2 ± 1.1 ha) was larger than females (0.2 ± 0.2 ha), though this difference was not significant. Males and females used more nests located inside than outside of their core areas. Distance from the core area edge to the nest located outside the core was longer for males (78.6 ± 139.9 m) than for females (39.7 ± 39.9 m), but this difference was not significant. Siberian flying squirrels in urban forests likely show similar ecology with flying squirrels in consecutive forests; however, they might change their behavior to share resources with others because urban forests restrict nest and food resources.

Distribution of Common Raccoons and Coyotes During Quail Nesting Season

Mammalian predation of quail and their eggs is a problem to many producers of quail particularly considering that abundance of common meso-predators, such as coyotes (Canis latrans) and common raccoons (Procyon lotor), is increasing. Predator removal programs are often not cost effective in increasing quail numbers but habitat management may be appropriate. There is a need for detailed knowledge of the habitat preferences and foraging patterns of these predators so producers of quail may limit predation of quail through management decisions and habitat manipulation. We placed GPS collars on 5 coyotes and 11 raccoons at Rolling Plains Quail Research Ranch, Fisher County, Texas during the nesting season of northern bobwhites (Colinus virginianus). The location of each animal was recorded at 5-min intervals for 35–42 consecutive nights. Habitat use and selectivity was calculated by Chi-square test of proportional use and availability of ecological sites both within the minimum convex polygon area used by each animal and throughout the ranch and adjacent 3-km buffer zone. Distribution of marked animals relative to roads, water, and quail feeders was compared to an equal number of randomly generated locations. Coyotes preferentially hunted in grassland which is prime nesting habitat for northern bobwhites. Coyotes were not deterred from accessing grassland with high concentrations of low growing plains prickly pear (Opuntia polyacantha). The nocturnal paths taken by coyotes over 1 month effectively covered virtually all the grassland habitat within their home range which increases the probability of locating nesting quail. Coyotes used ranch roads for travel but had little attraction to quail feeders and water sources. Raccoons favored areas of heavy cover such as riparian woodland and boulder strewn hillsides. Female raccoons had small home ranges and remained within thick cover. They rarely entered the more open habitats where quail nest and did not use ranch roads or seek out quail feeders which were mainly in grassland areas, nor did they encounter cactus-dominated grassland areas. Male raccoons had more expansive home ranges than females; they favored riparian strips and rocky hills as travel corridors but also ventured into more open habitats. They strongly avoided cactus-dominated areas but used grassland where scattered shrubs provided additional cover. Male raccoons within these areas used ranch roads for ease of travel and certain individuals frequently visited quail feeding stations. The tortuous nocturnal foraging path followed by raccoons provided efficient search patterns for locating scattered resources such as quail nests. Raccoons are generally considered to be more problematic predators of quail nests than coyotes. Where coyotes are less of a threat to quail than raccoons, tolerating the presence of coyotes may protect quail through competitive exclusion of raccoons from grasslands by the larger predator. Similarly, cactus in grasslands is seen as a problem for grazing livestock and a hindrance to quail hunters, but leaving some areas dominated by cactus may provide quail with valuable nesting refugia inaccessible to raccoons. The success of supplemental feed programs for quail should be balanced against the problem of altering the distribution of raccoons so they spend more time in quail nesting habitat and are more likely to discover quail nests. Placing feeders in areas where cover for predators is limited is advisable, as is targeted predator removal at quail feeding stations.

Movement patterns of soft-released, translocated Egyptian tortoises

Dispersal from the release site and high mortality are two main factors that contribute to low retention of hard-released translocated wildlife. A soft-release translocation is a method that may increase the likelihood of translocation success because individuals are forced to acclimatize and become familiar to the new release site prior to the translocation. The objective of this study was to compare the movement patterns and retention rate of resident and translocated Egyptian tortoises that were translocated just prior to the start of the aestivation season and therefore were forced to aestivate at the release site (a forced in-activity soft-release). The retention rate of translocated tortoises, the proportion of tortoises that remained at the release site and alive by the end of the study, was 71% (5/7) compared to a retention rate of 100% for resident tortoises. There was no significant difference in the minimum convex polygon area, total distance moved, or the number of relocations during the activity season between resident and translocated tortoises. Our results suggest that a forced in-activity soft release consisting of translocating Egyptian tortoises just before the aestivation season may be effective in minimizing dispersal from the release site.

Sex-specific indicators of landscape use by servals: Consequences of living in fragmented landscapes

The conversion of wetlands and its associated habitat for farming, residential development and commercial purposes has led to many small disconnected patches of native vegetation surrounded by generally inhospitable human altered land uses. Such human interventions pose a serious threat to the survival of wetland dependent indicator species such as the serval (Leptailurus serval) in the Drakensberg Midlands of KwaZulu-Natal, South Africa. To address the effects of habitat fragmentation on serval space use we used GPS fixes of collared individuals for 100 days between May 2013 and January 2014. We tracked five females and eleven male servals with GPS-UHF collars. Fragmentation indices at the class level (wetland, forest with bushland, grassland and cropland) were measured within the collared serval's minimum convex polygon area (MCP) of home range. Serval use points and fragmentation indices were extracted to each sub-landscape unit of 2km2 falling within the MCP home range. The response of serval population to fragmentation indices was analyzed using generalized linear models at three levels: male, female and the overall population. We found that core area of wetland positively explained landscape use by servals. Effects of forest core area, forest proximity and patch richness were important for landscape use by male servals. Male and female serval use declined with increase in complex shapes of forest and grassland, wetland clumpiness for females and overall, and cropland patches for servals overall. Our results showed that wetland is a key determinant for the survival of male and female servals in fragmented landscapes therefore effective conservation of serval population demands adequate viable native habitat.

Is there really no place like home? Movement, site fidelity, and survival probability of translocated and resident turtles

Wildlife translocations, the deliberate movement of wild individuals from one part of their distribution to another, are increasingly being used as a conservation tool. Despite the popularity of translocations as a conservation technique, translocations are often not successful as a result of excessive movement, poor release site fidelity, and low survival. This study compares the movement patterns, site fidelity, and survival probability of resident and hard-released musk turtles (Sternotherus odoratus) in a complex of patchy distributed wetlands. Our results are different from most translocation studies as the majority of translocated turtles had movement (minimum convex polygon area, total distance moved, number of wetlands used, and the number of movement shifts between wetlands), release site fidelity, and wetland fidelity patterns that were similar to resident turtles. In addition, the survival probabilities of resident and translocated turtles were both high. We believe the combination of poor overland movement capabilities and the patchy distribution of wetlands surrounded by a strong boundary matrix of terrestrial habitat, potentially increased the costs of leaving the wetland. The high costs of travelling overland to more distant wetlands may have constrained the translocated turtles dispersal from the release site and increased release site fidelity. Our study suggests that hard-release translocations may be an effective conservation method for highly aquatic species unlikely to leave the wetland and travel long overland distances.

Do Power Lines and Protected Areas Present a Catch-22 Situation for Cape Vultures (Gyps coprotheres)?

Cape vulture Gyps coprotheres populations have declined across their range due to multiple anthropogenic threats. Their susceptibility to fatal collisions with the expanding power line network and the prevalence of carcasses contaminated with illegal poisons and other threats outside protected areas are thought to be the primary drivers of declines in southern Africa. We used GPS-GSM units to track the movements and delineate the home ranges of five adult (mean ±SD minimum convex polygon area = 121,655±90,845 km2) and four immature (mean ±SD minimum convex polygon area = 492,300±259,427 km2) Cape vultures to investigate the influence of power lines and their use of protected areas. The vultures travelled more than 1,000 km from the capture site and collectively entered five different countries in southern Africa. Their movement patterns and core foraging ranges were closely associated with the spatial distribution of transmission power lines and we present evidence that the construction of power lines has allowed the species to extend its range to areas previously devoid of suitable perches. The distribution of locations of known Cape vulture mortalities caused by interactions with power lines corresponded to the core ranges of the tracked vultures. Although some of the vultures regularly roosted at breeding colonies located inside protected areas the majority of foraging activity took place on unprotected farmland. Their ability to travel vast distances very quickly and the high proportion of time they spend in the vicinity of power lines and outside protected areas make Cape vultures especially vulnerable to negative interactions with the expanding power line network and the full range of threats across the region. Co-ordinated cross-border conservation strategies beyond the protected area network will therefore be necessary to ensure the future survival of threatened vultures in Africa.

Foraging Ranges of Immature African White-Backed Vultures (Gyps africanus) and Their Use of Protected Areas in Southern Africa

Vultures in the Gyps genus are declining globally. Multiple threats related to human activity have caused widespread declines of vulture populations in Africa, especially outside protected areas. Addressing such threats requires the estimation of foraging ranges yet such estimates are lacking, even for widespread (but declining) species such as the African white-backed vulture (Gyps africanus). We tracked six immature African white-backed vultures in South Africa using GPS-GSM units to study their movement patterns, their use of protected areas and the time they spent in the vicinity of supplementary feeding sites. All individuals foraged widely; their combined foraging ranges extended into six countries in southern Africa (mean (± SE) minimum convex polygon area = 269,103±197,187 km2) and three of the vultures travelled more than 900 km from the capture site. All six vultures spent the majority of their tracking periods outside protected areas. South African protected areas were very rarely visited whereas protected areas in northern Botswana and Zimbabwe were used more frequently. Two of the vultures visited supplementary feeding sites regularly, with consequent reduced ranging behaviour, suggesting that individuals could alter their foraging behaviour in response to such sites. We show that immature African white-backed vultures are capable of travelling throughout southern Africa, yet use protected areas to only a limited extent, making them susceptible to the full range of threats in the region. The standard approach of designating protected areas to conserve species is unlikely to ensure the protection of such wide-ranging species against threats in the wider landscape.

ASSOCIATION BETWEEN MOVEMENT AND SIN NOMBRE VIRUS (BUNYAVIRIDAE: HANTAVIRUS) INFECTION IN NORTH AMERICAN DEERMICE (PEROMYSCUS MANICULATUS) IN COLORADO

Capture data from long-term, mark-recapture studies were used to evaluate movements of North American deermice (Peromyscus maniculatus) on mark-recapture webs in Colorado with respect to Sin Nombre virus (SNV) infection status, age, sex, and trapping site. Latitude and longitude coordinates for each capture during the approximately 12-yr study were used to produce an individual minimum convex polygon (MCP) area representing the movements (not home range) of an individual mouse over time. These MCP areas were compared by SNV infection status (as determined by the presence of antibody), age, and sex. Antibody-negative deermice had significantly larger mean MCP areas than did antibody-positive mice. No differences in MCP area were found between male and female mice (either positive or negative). The smaller MCP areas of antibody-positive mice correspond to decreased movement by SNV-infected deermice on the trapping webs. These findings may indicate that SNV has a negative effect on movement, perhaps by reducing the health of infected deermice.

Movement patterns of giant Pacific octopuses, Enteroctopus dofleini (Wülker, 1910)

We attached sonic transmitters to, and tracked, 40 giant Pacific octopuses (Enteroctopus dofleini) ranging from <1 to 21kg in size in south-central Alaska using near-continuous tracking by fixed-array receivers and intermittent tracking with a mobile receiver. We documented area use, daily activity patterns, spatial scale of movements and whether these differed by octopus size, and whether octopuses actively selected habitats. Near-continuous fixed tracking provided positions about every 4 min over a limited area, while intermittent mobile tracking provided positions every 1–6h but over open and larger areas. Mantle-mounted transmitters on modified Peterson disks had >83% retention to the end of a tracking period (range <1day [before animal left the study area] to at least 88days post-release), an improvement over published studies. Octopuses were found to be stationary or hiding 94% of the time. Otherwise, octopuses were active throughout the day but more so from midnight to 0500. During low tides, movements were restricted for animals in intertidal habitats but not for those deeper. Maximum movement distance from release was 4.8km (by a 16.5kg female). Minimum convex polygon area use averaged 4,300m2 for the smallest animals to an average over 50,000m2 for the largest during 2 to 20days of tracking, substantially larger than previously reported. Larger octopuses moved further and used greater area than smaller animals, but differences between sexes were not significant.Stationary behavior and periods without detection (rest) by fixed near-continuous tracking were bi-modally distributed, with peaks <3h duration and >18–48h. Direct movements (indicating relocation or den switching) were common at night, central-tendency movements (indicating localized area use and return to den) were common at dawn, and stationary behavior was common in daylight, although each pattern occurred at all periods. Central-tendency movements recorded by intermittent tracking were oriented parallel to contours, while movements without central-tendency crossed contours, suggesting that animals navigate by contour following to return to a known den. During a relocation experiment, octopuses released at shallow depths moved deeper and those released deeper moved shallower, both into habitats with greater kelp cover. Although >90% of their time was spent stationary and hiding, Enteroctopus dofleini utilizes information about its environment (contour following), selects habitats (preference for more kelp cover), and occupies large use areas (minimum convex polygons) by making substantial direct movements from previous use areas.

Detecting autocorrelation problems from GPS collar data in livestock studies

Uneven use of grasslands and savannas by livestock has a significant impact on ecosystem productivity, biodiversity, and function. In studies of livestock distribution, global positioning systems (GPS) collars are frequently used and the rapid rate of technological improvement has brought new opportunities to collect extremely large amounts of very accurate spatial information. However, these advances also pose statistical challenges associated with the analysis of large, temporally correlated, datasets. Our main goal was to find the optimal sampling time intervals for GPS collar schedules when studying livestock distribution in semi-arid ecosystems. The schedule must provide maximum spatio-temporal information while avoiding problems of autocorrelation of sequential locations to provide a methodology that is both practical and statistically valid. We used GPS collar data collected in the Southwestern region of the United States. In each study cattle were tracked and data were recorded every 5 min. Location information from the 5-min GPS fixes were subsampled into 10, 20, 30, 60, 90, 120, 150, 180, 240, 300, 360, and 420-min regular intervals. We calculated the Euclidean distance between pairs of successive locations then conducted correlation analyses to determine the degree of similarity between successive traveled distances. We then selected two correlated and two non-correlated time-interval datasets to compare estimates of kernel home range and minimum convex polygon areas. Successive Euclidean distances between GPS locations were significantly correlated when time intervals were <120 min. The calculated distance traveled was significantly reduced as time intervals between successive locations increased. Kernel home range values were smaller in correlated than in non-correlated datasets yet minimum convex polygon values were greater in correlated data than in non-correlated data sets. Our study shows the importance of considering different livestock sampling time intervals using GPS to achieve accurate and meaningful results on animal distributions especially in semi-arid ecosystems. Circumstances in which researchers may elect to use short-time interval autocorrelated data sets are also discussed.

Evaluation of fast-acquisition GPS in stationary tests and fine-scale tracking of green turtles

Fastloc GPS (FGPS) is a variant of Global Positioning System (GPS) technology that offers important new utility for investigating fine-scale movements of marine animals like green turtles that surface too briefly for effective use of standard GPS. I report here on the accuracy and efficiency of this novel technology, compare it with two alternative methods, namely boat-based ultrasonic tracking and Argos Platform Transmitter Terminals (PTTs), and provide new data on the vagility and habitat selection of green turtles in shallow coastal foraging habitat. I used a combined FGPS receiver and PTT transmitter (Sirtrack, Havelock North, New Zealand) mounted together with an ultrasonic transmitter and time-depth recorder in a tether-attached housing that allowed automatic detachment and subsequent retrieval of the equipment without the requirement to recapture turtles. With this equipment I conducted short deployments (4.5 to 16.8 d) on 3 free-living adult-size green turtles in coastal foraging habitat in Queensland, Australia. In addition, stationary tests in air and afloat were conducted at the same site. FGPS location error (mean ± SD) increased as the number of satellites used in each computation decreased, from 26 m ± 19.2 (8 satellites) to 172 m ± 317.5 (4 satellites). During live tracking the frequency of FGPS locations greatly exceeded Argos PTT, such that screened data comprised about 50 times more FGPS locations despite a much tighter screening threshold for FGPS (250 m) than for Argos PTT (1000 m). FGPS locations showed the three study turtles used modest short-term activity ranges with Minimum Convex Polygon area mean ± SD 662 ha ± 293.9. They all remained within < 4.7 km of their capture–release locations and favoured shallow water, with 86% of locations at charted depths ≤ 3 m and the deepest location at 5.9 m. Fine-scale movements of each turtle varied from day to day with respect to tortuosity and areas traversed. Statistically significant day–night differences were evident in average rates of movement (greater by day) and in habitat selection, where diurnal locations had greater seagrass density while nocturnal locations featured deeper bathymetry. Individual turtles revisited some of their centres of activity (identified from 50% fixed kernel utilisation distributions) on multiple occasions but none of the study turtles travelled consistently between the same day–night pair of sites as has been reported elsewhere. Such disparity and the day-to-day variation in movements revealed by these short-term findings highlight the need for detailed tracking over longer periods at multiple locations. Fastloc GPS technology proved an effective new tool for this area of research.

Site fidelity and movements of gilthead sea bream ( Sparus aurata) in a coastal lagoon (Ria Formosa, Portugal)

Short-time site fidelity and movements of gilthead sea bream ( Sparus aurata) in a coastal lagoon were determined using passive acoustic telemetry. Nine fish, ranging from 20.1 to 32.5 cm total length, were surgically implanted with acoustic transmitters and monitored for up to 179 days. Minimum convex polygon areas ranged from 18,698.6 m 2 to 352,711.9 m 2. Home range sizes were small, with individuals using core areas on a daily basis. However, these core areas shifted within the study site over time towards the opening to the sea. Two different diel behaviors were recorded, with some individuals more active at night and others during day time. Some individuals also demonstrated homing abilities, returning to the capture site after being released more than 4 km away.

Ecology and Behavior of the Midget Faded Rattlesnake (Crotalus Oreganus Concolor) in Wyoming1

We conducted a three-year study to describe the ecology and behavior of the Midget Faded Rattlesnake, Crotalus organus concolor. We encountered 426 and telemetered 50 C. o. concolor between 2000 and 2002. We found that their primary diet was lizards (associated with rock outcrops), though they will consume small mammals and birds. They den in aggregations, although in low numbers when compared to other subspecies. Movements and activity ranges were among the largest reported for rattlesnakes. Minimum convex polygon area was 117.8 ha for males, 63.9 ha for nongravid females, and 4.8 ha for gravid females. Mean distances traveled per year were 2122.0 m for males, 1956.0 m for nongravid females, and 296.7 m for gravid and postpartum females. Following emergence from hibernation, they spent several weeks shedding, often in aggregations before migration, and migrations occurred in early summer. Most snakes made straight-line movements to and from discrete summer activity ranges where short, multidirectional movements ensued, although others made multidirectional movements throughout the active season. We observed mating behavior between 21 July and 12 August. Gravid females gave birth during the third week of August. Mean clutch size was 4.17 (range 2–7). We found that the sex ratio was skewed favoring females 1:1.24, and they were sexually dimorphic in size (males SVL = 44.1 cm; females SVL = 40.8 cm). Our data further illustrate the diversity within the large group of Western Rattlesnakes (Crotalus viridis).

Application of GIS to investigate the use of space in coral reef fish: a comparison of territorial behaviour in two Red Sea butterflyfishes

The space use of two coral‐feeding Red Sea butterflyfish species (Chaetodon austriacus and C. trifascialis) was studied at three sites in the Gulf of Aqaba to determine the extent of intraspecific territoriality. Individuals or pairs were observed in shallow water (<5 m). Their locations were recorded on maps of each study reef. The Animal Movement Analysis Extension (AMAE) in ArcView was used to plot territory borders and compute territory size for each species. Chaetodon austriacus, a generalist corallivore that exploited evenly distributed food resources, maintained small exclusive pair territories with clearly defined territory boundaries. In contrast, C. trifascialis, a specialist corallivore that exploited patchily distributed food resources, demonstrated considerable variation in territorial behaviour that ranged from the defence of small exclusive solitary territories to the shared use of a large home range. Comparisons of territory area estimates showed that 95% kernel probability density function territory boundaries matched intuitive territory boundaries and, unlike the minimum convex polygon area, did not contain obvious areas that were not used by individuals or pairs. We show that comparing different territory size measures can be very useful in describing subtle differences in territorial behaviour between species and studies. For this purpose, GIS is an ideal technology with which to carry out such analyses quickly and easily.

Activity patterns and foraging behaviour of Audouin' s gulls in the Ebro Delta, NW Mediterranean

SUMMARY: Twenty Audouin’s gulls, Larus audouinii, breeding in the Ebro Delta (NW Mediterranean) were radio-tracked in 1998 to study their foraging behaviour and activity patterns. Some detrimental effects of tagging on the breeding success of the birds were detected, especially when both members of the pair were tagged. The results were actually constrained by the low number of locations due to natural breeding failure and failure in tag emission, as well as the adverse effect of tagging. However, through a combination of aircraft surveys at sea and a fixed station for automatic tracking of the presence of the birds at the colony, novel individual-based information of home ranges and activity patterns was obtained. Trawler fishing activity seemed to influence both the foraging range and habitat use: while trawlers operated, gulls overlapped their fishing grounds with vessels, probably to scavenge on discards. Very few locations were obtained during a trawling moratorium period, although they were all recorded in coastal bays and terrestrial habitats. During the trawling activity period, gulls ranged over a minimum convex polygon area of 2900 km2. Gulls were tracked up to 40 km from the colony, but some individuals were observed beyond 150 km while still breeding. Arrivals and departures from the colony were in accordance with the trawling timetable. However, most birds also showed some nocturnal foraging activity, probably linked to active fishing of clupeoids (following diel migrations) or to the exploitation of purse-seine fishing activity. Foraging trips lasted on average 15 hours: males performed significantly shorter trips than females, which spent more time outside the colony. The proportion of nocturnal time involved in the foraging trips was the same for males and females, but whilst all males initiated their trips both during the day and at night, some females only initiated their trips during the day. Hatching success was found to be related to foraging effort by males. Gulls spent on average ca. 38% of their time budget outside the nesting territory, representing the time devoted mainly to flying, foraging and other activities.

Survival and behavior of freshwater turtles after rehabilitation from an oil spill

An oil spill in February 2000 at the John Heinz National Wildlife Refuge in southeastern Pennsylvania affected four species of freshwater turtles including painted turtles (Chrysemys picta), snapping turtles (Chelydra serpentina), red-eared slider turtles (Trachemys scripta), and red-bellied turtles (Pseudemys rubriventris). In the summer and fall of 2000, there were no differences in survival, home range, and temperature preference of 16 oil exposed/rehabilitated (OER) turtles, 18 possibly exposed (PE) turtles, and 32 non-exposed (NE) turtles as measured with temperature sensitive radio transmitters. Post-release mortality or transmitter loss was not correlated to oil exposure (OER=25%, PE=22%, NE=31%). There were no statistically significant differences in home range minimum convex polygon area, (0.28<P <0.87) and water temperature preference (0.35<P <0.99) between OER, PE, and NE male and female C. picta, C. serpentina, and T. scripta. Mean home ranges scaled from 5.0 ha ±4.1 (male C. serpentina ) to 25.5 ha ±5.0 (male P. rubriventris) and mean water temperatures occupied varied from 19.6 °C±6.9 (female C. serpentina) to 22.3 °C±8.5 (female C. picta). Rehabilitation of oil exposed freshwater turtles is effective in restoring these animals to normal behavior in nature.