Spatial organization in the Ethiopian wolf Canis simensis: large packs and small stable home ranges

The spatial organization of the rare Ethiopian wolf ( Canis simensis ) was studied in the Afroalpine heathlands of Bale Mountains National Park, southern Ethiopia, between 1988 and 1992. Nineteen animals were radio-tracked, 48 ear-tagged and 64 others recognized by coat patterns and observed directly. Dry season (October—March) home ranges of resident wolves covered between 2 and 15 km². The ranges of adult males were slightly larger than those of females, and subadults' home ranges were slightly smaller than those of adults. The population density of the wolves was correlated with prey biomass. In optimal habitat, wolves lived in packs of 3—13 adults (mean 5.9 wolves > 1year old) containing several close-kin males; adult sex ratio favoured males 1.88: 1 and combined pack home ranges averaged 6.0km². In an area of lower prey productivity, wolves lived in pairs or small groups (mean 2.7), adult sex ratio was 1:1 and home ranges averaged 13.4 km².
Home ranges overlapped extensively (mean 85%) between members of the same pack. Four to seven percent of the population was additionally composed of non-resident females, inhabiting larger ranges (mean 11.1 km²). Home ranges of neighbouring packs were largely discrete, forming a tessellating mosaic of packs occupying all available habitat. Pack home ranges were stable in time, drifting only during major pack readjustment after the disappearance of a pack or significant demographic changes. Ethiopian wolf home ranges were smaller than would be expected for a carnivore of its size and sociality, presumably as a result of the high rodent productivity of the Afroalpine ecosystem.     

Population ecology of the white-nosed coati (Nasua narica) on Barro Colorado Island, Panama

The white-nosed coati, Nasua narica , is a common Neotropical carnivore with a social structure of band-living adult females and solitary adult males. A coati population on Barro Colorado Island, Panama, was studied over a four-year period by mark-recapture, radiotelemetry. and direct observation of habituated individuals. The population density was approximately 51.5 individuals/km² and the sex ratio was 1:1. Band size varied from six to 26 individuals (mean = 15.3) with extensive fluctuation within and between years. Mean foraging group size was smaller (7.2 individuals) than population group size, and fluctuated with food availability, synchronous parturition, and the emigration of mature males. Mean home-range size of six bands was 0.33 km², and ranges of adjacent bands overlapped from 0–66%. One band fissioned during the study; however, the resulting bands did not disperse from the original home range. Seven adult males had a mean home-range size of 0.37 km², each extensively overlapping the home ranges of several other males. Observations of 10 adult males whose natal bands were known indicate that when males disperse they do not simultaneously leave the band's home range. Rather, their home ranges remain within or broadly overlapping those of their natal bands. This dispersal pattern is unusual within the order Carnivora.     

Home range and habitat use of wolverines Gulo gulo in Yukon, Canada

Home ranges and habitat use are described for three adult female, one adult male, and one subadult male wolverines in the Kluane Game Sanctuary, Yukon. When long distance excursions are not included, home ranges of wolverines in the Kluane Game Sanctuary were between 76 and 269 km² for females and 209 and 269 km² for males. Habitat use of females was similar to habitat availability. Males used subalpine coniferous habitats more frequently than other habitat types during winter. Although individual variation in the use of forest cover types, aspects, slopes and elevations was apparent, seasonal use did not differ from availability for each sex. Within the 1590 km² study area, three adult males and six adult females were present, corresponding to a density of one resident wolverine 177 km^-2.     

Spatial organization of leopards Panthera pardus in Taï National Park, Ivory Coast: is rainforest habitat a 'tropical haven'?

Between June 1992 and July 1994, two female leopards and one male were radio-tracked. Regular locations of the leopards, the use of a phototrap, and spoor data, provided the first detailed ecological data about this elusive felid in tropical rainforest habitat. The home range of the male was 86 km², those of the two females were 29 km² and 22 km², respectively. One female's home range was fully included within that of the male. Home ranges of neighbouring residents were not exclusive. Population density is estimated at one leopard per 9-14 km². Intraspecific interactions were rare and predominantly involved mating. The large size of the home ranges and a relatively high population density imply large overlap between adjacent resident leopards' ranges. Differences in the leopard's land tenure system between the rainforest and the savanna are discussed. Doubt is cast on the validity of the often-quoted estimate of one leopard per 1 km² in tropical rainforest habitat.     

Wintering site fidelity and movement patterns of Western Sandpipers Calidris mauri in the San Francisco Bay estuary

Western Sandpipers Calidris mauri are the most numerous shorebird species in the San Francisco Bay estuary during winter. A sample of 106 Western Sandpipers was captured in mist nets and radio-marked with 1-g transmitters to examine their wintering site fidelity and movements. Differences in distances moved, home range extent and core area size were examined by age, sex, season, site, time of day and tide. All birds remained in the south San Francisco Bay region during winter and exhibited strong site fidelity, with a mean home range of 22.0 km² or only 8% of the study area. First-year birds had larger home ranges (26.6 ± 3.6 km²) than adults (17.2 ± 2.5 km²) in winter, but home range sizes of males and females were not significantly different in any period. Home range sizes were similar between seasons, but core areas were smaller in spring (6.3 ± 1.2 km²) than in early (9.6 ± 4.0 km²) or late (11.6 ± 1.6 km²) winter. Movements and home range size were similar for radio-marked birds located during day and night. The high degree of regional and local site fidelity demonstrated that the mixture of natural mud fiats and artificial salt ponds in southern San Francisco Bay provided sufficient resources for large wintering populations of Western Sandpipers.     

Jaguar spacing, activity and habitat use in a seasonally flooded environment in Brazil

Between July 1980 and February 1984, six jaguars (two males, four females) were fitted with radio-collars and monitored for a cumulative total of 105 months, in the Pantanal region of southwestern Brazil. Mean home range size (minimum convex polygon) for five of them (one male, four females) was 142- 1 km². Mean home range size during the dry season was 54·3 km², whereas in the wet season it was significantly smaller, 12·8 km². Mean home range overlap of the four females was 42%. Use of gallery forest and forest patches exceeded the availability of these habitat types in the animals' home ranges, whereas open forest and grassland were used less than expected on the basis of their availability. Mean distance moved between locations on consecutive days was 2·4 km (0.2-10·4 km). The mean one-day movement of the male jaguar was significantly (P<0·001) larger than that of the females. Mean distance travelled by all animals during one-day intervals in the dry season was significantly greater (P<0·001) than that travelled in other months. Jaguars were more active during daytime than night-time (P<0·001). Overall level of activity for the wet season did not differ from that of the dry season. With their larger body size, jaguars in the Pantanal may require more food than jaguars in other areas of the species' range. This, in addition to differences in prey availability and the annual availability of dry land, appear to influence the difference in home range size between jaguar populations.     

Ecology and behaviour of the Jaguar (Panthers onca) in Belize, Central America

Five adult male Jaguars and a translocated subadult female Jaguar were captured and followed by radio-telemetry in Cockscomb Basin, Belize. One adult male Jaguar, two resident female Jaguars, and a Puma were followed only by their tracks. Radio-collared males maintained overlapping ranges of 28–40 km², while resident females moved in minimum areas of 10 km² within the ranges of individual males. Despite range overlap, evidence of aggression or sign of more than one large cat in the same area simultaneously was uncommon. Such avoidance behaviour suggested some means of communication. Visual marking in the form of faeces and scrapes were found uncovered along roads and trails in areas of overlap between the cats; such marking could have helped in boundary delineation as well as spatial and temporal positioning. Males often remained in small areas of 2·5 km² for up to two weeks, a behaviour made possible by abundant prey. This behaviour may have facilitated avoidance with other Jaguars. Faecal analysis indicated opportunistic feeding on 17 prey species. Armadillo, Paca and brocket deer accounted for 94% of the available terrestrial prey and comprised 70% of the identified prey in the faeces. All Jaguars were primarily nocturnal, though activity varied between animals. The translocated female showed changes in activity patterns when feeding upon cattle. At least one Puma travelled within the ranges of several male Jaguars and appeared to be feeding on smaller prey items. The behavioural and ecological plasticity exhibited by the Jaguars in this study is beneficial for an animal whose habitat is rapidly diminishing.     

Abundance and distribution of endangered Franciscana dolphins in Argentine waters and conservation implications

This is the first study in Argentine waters on the abundance of the threatened Franciscana dolphin, Pontoporia blainvillei . During 2003–2004 we carried out 17 aerial surveys using line transect sampling methodology. We observed 101 Franciscanas in 71 sightings. In northern areas density was estimated at 0.106 individual/km². Density was lower in southern areas (0.055/km²) and declined with depth beyond 30-m isobaths (0.05/km²). A correction factor for submerged dolphins was applied to density and then extrapolated to the strip between the coastline and the 30-m isobath. Abundance in the northern area was estimated at 8,279 (4,904–13,960) individuals, while in the southern area it was estimated at 5,896 (1,928–17,999) individuals. Considering an annual mortality of about 500–800 individuals, about 3.5%–5.6% of the stock may be removed each year by the fishery and over the 2% recommended by the International Whaling Commission (IWC) and may not be sustainable by the population. Higher densities in coastal areas make Franciscanas more vulnerable to coastal fishing camps, which increased mortality in recent years. A remarkable finding was that while density decreases to the south, values of catch per unit effort (CPUE) increases, indicating different catchability of dolphins between areas.     

Movements and habitat use in gravid and nongravid female garter snakes (Colubridae: Thamnophis)

Two dhole ( Cuon alpinus ) packs were monitored in Mudumalai Sanctuary, southern India, during 1989-93 to look at population dynamics, movement pattern, and foraging strategy and their inter-relationship with the maintenance of social groups. Pack size fluctuated substantially (4–18 and 4–25 in the two packs) owing to dispersal and demographic factors such as females not breeding in a given year. Both packs killed a much higher proportion of chital ( Axis axis ) and sambar ( Cervus unicolor ) fawns (2 and 54.2km² for the two packs) was not correlated with pack size. Pack movement from one resource patch (consisting of resting sites and aggregations of prey species) to another was not random or based on factors such as inter-patch distance or relative prey densities. There was no difference in mean residence time of the pack across the four resource patches; the pack moved across these in a sequential manner in one direction. We conclude that dholes live in groups not because of any advantages accruing from enhanced group sizes through increased per capita yield of food, but as a consequence of the dispersion of resources.     

The population density, growth rate and production of roach Rutilus mtilus (L.) in Tjeukemeer, The Netherlands

A method of estimating the population density of roach in Tjeukemeer (21.3 km²) using 20 529 introduced fin-clipped fish is described. Fyke nets proved to be an effective method of sampling the population for marked fish during the spawning season. A total of 20 277 roach were processed during the recapturing period. The population density of roach (⋝ 14 cm) was estimated to be 1 246 458. The growth rate of roach in the lake although relatively poor (von Bertalanffy's L ∞ for males and females, 22 and 26 cm respectively) for the species was similar to that recorded in three other Friesian lakes. The mortality rate of males was higher than that of females. Logarithmic length-weight regression analyses showed that the value of the coefficient varied both within and between the sexes, that of females being higher (range 3.03–3.375) than that of males (range 2.76–3.254). Seasonal changes in the size of the coefficient were due to a disproportionate loss of gonad weight in larger fish. The fecundity of the population was comparatively high for the species.
The total production of the population was estimated to be 95 hg ha⁻¹ of which 39 kg ha⁻¹ was contributed by fry. In older (⋝ IV) fish the production of females (12 kg ha⁻¹) exceeded that (2 kg ha⁻¹) of males, due to differences in their growth and mortality rates. The relatively poor performance of roach in Tjeukemeer, in terms of biomass and production was due to a scarcity of zoobenthos and competition from other species offish. There is no evidence either from this study or the literature that the productive potential of roach in lakes is high, even though macrophytes and detritus can be consumed in significant amounts.     

Site fidelity and the demographic implications of winter movements by a migratory bird, the harlequin duck Histrionicus histrionicus

Understanding the degree of demographic connectivity among population segments is increasingly recognized as central to the fields of population ecology and conservation biology. However, delineating discrete population units has proven challenging, particularly for migratory birds as they move through their annual cycle. In this study, radio telemetry was used to assess movement rates among habitats by harlequin ducks Histrionicus histrionicus during the non-breeding season in Prince William Sound, Alaska. A total of 434 females were outfitted with radio transmitters over six years of data collection, and their signals tracked by aircraft. Using a spatially nested design, it was determined that 75% of radioed females remained in the bay or coastline area where they were originally trapped, 94% remained on the same island or mainland region of Prince William Sound where they began the winter period, and 98% remained within the 4500 km² study area as a whole. Home range analyses corroborated these findings, indicating that the scale of individual movements was small, with 95% kernel home range estimates averaging only 11.5±2.2 km². A simple demographic model, which incorporated estimates for population size, survival, and movement rates, was used to infer the degree of independence among population segments. Immigrant females were found to contribute little to population numbers in most areas, accounting for only 4% of the adult female population at a scale of approximately 100 km². These results have important implications for the scale of conservation action for the species and demonstrate that winter movements can have a strong influence local population dynamics.     

The demography of a high-density badger (Meles meles) population in the west of England

Data from the longest running capture-mark-recapture study of Eurasian badgers, in an undisturbed wild population at Woodchester Park in Gloucestershire, were used to investigate population dynamics. Twenty-one social groups of badgers occupying an area of 7.3km² were studied from 1978-1993. The density increased steadily over the study period, reaching the highest published density known anywhere at 25.3 adults per km² in 1993, and the average social group size increased to 8.8 adults (S.E. ± 0.85) in 1993. By 1993, 97% of the population trapped was of known age and overall the population consisted of 27% cubs and 73% adults. In addition, the results supported previous studies in that the population had an equal sex ratio as cubs, but became increasingly female biased with age. There was high juvenile mortality, nearly 50% dying in their first year. Between 58 and 90.2% of adult females did not breed each year.     

White rhinoceros range size in the south-western Kruger National Park

White rhinoceros range size was ascertained telemetrically in the south-western Kruger National Park. The mean annual range size of territorial males was 9.86 km² compared to 22.83 km² for adult females. White rhinoceros females' summer wet season range was larger (21.44 km²) than the winter dry season range (11.64 km²). It is argued that abundant field-water during the wet season enables animals to range further from permanent water supplies and to utilize larger foraging areas. White rhinoceros have core areas in their individual ranges that usually are situated along riverbanks in the preferred grazing regions. These core areas also include some favourite resting spots on high-lying areas. White rhinoceros range sizes in the south-western Kruger National Park were similar to those of other reserves with comparable white rhinoceros densities. In the Umfolozi Game Reserve, which has a higher white rhinoceros density than the Kruger National Park, the individual ranges are much smaller.     

Rangeland degradation is poised to cause Africa's first recorded avian extinction

Rangeland degradation by livestock threatens several restricted-range species, but is largely overlooked by conservation biologists. The Sidamo lark Heteromirafra sidamoensis , confined to the Liben Plain grassland in southern Ethiopia, is critically endangered by bush encroachment, permanent settlement and agricultural conversion. Its global range was previously estimated at 760 km², but in 2007–2008 available habitat covered<35 km². Density estimates from multi-model inference analysis of distance transect data provided a global population estimate of 90–256 adults (possibly with a serious sex-ratio bias towards males). Logistic regression models of habitat selection showed that males preferentially occurred in areas of grassland with greater cover of medium-length grass (5–15 cm), less cover of bare ground and fewer bushes. Habitat transects extending outward from its core range revealed massive and rapid bush encroachment, corroborating information from semi-structured interviews. The survival of both local Borana pastoralism and this species – mainland Africa's likeliest first avian extinction – depends on restoring seasonal patterns of grazing, resisting agricultural conversion of grasslands, reversing fire suppression policies and clearing bush.     

Determining the effects of habitat management and climate on the population trends of a declining steppe bird

The Little Bustard Tetrax tetrax is one of the most threatened steppe bird species in Europe, due mainly to agricultural intensification. Despite the relative importance of the Iberian population (approximately 50% of the global population) little is known about its dynamics and trends, especially in core distribution areas. This study evaluates the influences of meteorological factors and land management on the oscillations and medium-term trends of two Little Bustard populations in Central Spain. During 2001–2007, surveys of breeding male and female Little Bustards were carried out in two central Spanish locations: Valdetorres, in Special Protection Area (SPA) no. 139 (1600 ha), and Campo Real, in Important Bird Area (IBA) no. 075 (1150 ha). Densities were 3.3–4.0 and 1.1–2.1 males/km² in Campo Real, and 1.8–2.2 and 0.6–1.3 females/km² in Valdetorres. The sex ratio was biased towards males in both cases. Both populations declined during 2001–2007, especially in Valdetorres (60%). Variation in habitat composition did not explain variation in the numbers of males. Both populations were influenced by total precipitation in the preceding October–May period. Results suggest that the Little Bustard may be sensitive to future climate trends in Europe. Finally, different simulated demographic scenarios suggest that low female survival and productivity may be the immediate cause of the decline in Little Bustard populations, which is consistent with their sensitivity to climatic conditions.     

MOVEMENTS OF SATELLITE-TAGGED SUBADULT AND ADULT HARBOR SEALS IN PRINCE WILLIAM SOUND, ALASKA

Satellite-linked tags were attached to 49 subadult and adult harbor seals captured in Prince William Sound (PWS), Alaska, and their movements were monitored during 1992–1997. Seals were tracked for a total of 5,517 seal-days and were located on about 80% of the days that tags transmitted. Most locations were in or near PWS, but some juvenile seals moved 300–500 km east and west into the Gulf of Alaska. While several seals travelled to 50–100 km offshore, virtually all locations were in water <200 m deep. Overall, juvenile seals moved more than adults and had larger home ranges. Movements were significantly affected by month, and age by month and sex by month interactions. In all months, mean distances between successively used haulouts were <10 km for adults and <20 km for juveniles. Mean monthly home ranges varied from <100 km² to >1,500 km², and were smallest during June-July. Mean haul-out to at-sea distance was 5–10 km for adults and generally 10–25 km for juveniles. Satellite-linked tags provided an effective means of monitoring and describing the full range of harbor seal movements in this region, with the exception of late summer when tags were shed during the molt.     

Home range, association and related aspects of elephants in the eastern Transvaal Lowveld

Home range and association patterns of elephants Loxodonta africana in private nature reserves adjacent to the Kruger National Park, South Africa, were determined over a period of six years by using radio telemetry. The minimum convex polygon (MCP) and harmonic mean (HM) methods were used for data processing. The minimum and maximum range areas required by females were estimated at 115 and 465 km², respectively, whilst those of males varied between 157 and 342 km². Core areas of females comprised on average 10·1% of the range areas as calculated by the MCP method. Range areas between females in the Klaserie and Timbavati Private Nature Reserves differed significantly. A significant difference in range size was also found between the male population (pooled data) and the females of the Klaserie Private Nature Reserve. Range areas increased from the wet to the dry season. Three male elephant categories were established, namely males utilizing the same area during the study period, those who shifted their range areas and individuals with very large range areas which frequented the area on an irregular basis. A loose relationship existed between males. Association between females can be attributed to kinship and not to the overlapping of range areas. Results indicated avoidance behaviour between females in their core areas, which might partially explain the ability of elephants to tolerate high densities. It is concluded that male elephant hunting should be approached with caution.     

Home range of the raccoon dog (Nyctereutes procyonoides) in southern Finland

Home ranges, relationships between individuals and dispersal among raccoon dogs ( Nyctereutes procyonoides ) were studied in southern Finland in 1989-91. The average maximum home range, calculated by the harmonic mean method. was 9·5 km² and the core area (85% utilization) 3·4 km². There were no statistically significant annual. seasonal or sexual differences in the size of the average core area of adults, but the home ranges of juveniles in autumn were larger than those of adults. However. the maximum home ranges of adults were larger in autumn than in summer, especially those of males, which were conspicuously small in summer and large in autumn. The core areas of adjacent pairs did not usually overlap in the pup-rearing season. but in autumn some home ranges shifted and there was much more overlap. The home ranges of the male and female of a pair overlapped almost totally, and a male and a female sharing the same home range also travelled together or close to each other, thus supporting the idea that the raccoon dog is monogamous in Finland. None of the adults left the study area, but 38% of the juveniles were recovered further than 10 km from the marking place during the first autumn.     

Movement Patterns and Home Range Of The Bongo (Tragelaphus Eurycerus) In The Rain Forest Of The Dzanga National Park, Central African Republic

Bongos ( Tragelaphus eurycerus Ogilby) were studied for 8 months in the Dzanga National Park, Central African Republic. Tracks were followed and mapped with a compass and a pedometer to study movement patterns and home range. Natural licks were shown to be central points in the home range of the bongos: they visited the licks recurrently to consume soil, but also to forage on grass and herb species, and for social reasons. Forest areas far from licks were used much less than forest areas close to licks. When a lick was visited, distances between two resting sites were longer than in the forest without lick visits, caused by a direct and straight movement from the denser forest areas toward a lick. The study area of about 150 km² was presumably occupied by two groups of bongos. One of them seemed to split temporarily into two subgroups. Groups were not larger than 10–20 individuals. Estimated home ranges were at least 49 km² and 19 km² for the two groups, respectively. Estimated density in the Dzanga National Park was 0.25 bongos per km^2. This study shows the importance of natural licks for the largest social forest antelope, the bongo, and provides information which is important for its future conservation.     

Turnover and recruitment in a tundra population of Peregrine Falcons Falco peregrinus

The population dynamics of tundra-nesting Peregrine Falcons Falco peregrinus tundrius was studied over 7 years on a 450 km² study area in the Keewatin District of Canada's Northwest Territories. Peregrines showed strong fidelity to nest sites; none of 25 males ringed changed territories, while five of 38 females ringed were recorded changing territories. Such changes usually occurred after nesting failure. Annual turnover of territorial adults was estimated to be 22% (15% for males and 26% for females). Annual mortality of adults was estimated to be 17% (15% for males and 19% for females). If we assumed that territory vacancies, in addition to mate replacements, were indicative of mortality, then maximum annual mortality was estimated at 24% for each sex. Territories were held only by adult Peregrines. The oldest male on territory was at least 7 years old, the youngest was 2. The oldest female on territory was at least 7 years old, the youngest was 3. Territories were held by individuals of each sex for at least 6 years. One pair remained together for at least 4 years. Less than 4% of all young Peregrines produced on the study area in the first 5 years of the study were recruited into the breeding population. More male than female young were recruited despite an even sex ratio among nestlings. Peregrines did poorly in their first breeding attempts. The single young female recruited into the study population dispersed more than three times the median dispersal distance of six recruited males, suggesting that other females probably dispersed beyond the boundaries of the study area.