Spatial structuring and dispersal in a high density population of the California vole Microtus californicus

Space use patterns of California voles are described from intensive live-trapping data obtained during the late breeding season in a peak density year. Operational sex ratios were strongly female biased. Breeding males had mutually exclusive home ranges that overlapped the home ranges of one to several females. The average male home range was larger than the average female home range and tended to encompass female home ranges in their entirety. Breeding females had home ranges that often overlapped extensively with the home ranges of other breeding females. The degree of overlap, however, tended to be either very high or very low, indicating that groups of females may act territorially among themselves. Family groups that may include members of sequential litters formed at high density. Males on experimental removal grids had larger home ranges than males on the high density grids and some became wanderers while most females had home ranges comparable to those on the high density grids.
Dispersers onto low density grids were not a random sample of the high density population; large breeding adults and small juveniles were under-represented. No sex differences in dispersal were noted. Immigration into the high density populations was probably negligible.     

Effects of high density on spacing behaviour and reproduction in Akodon azarae: A fencing experiment

We studied the short term spacing behavioural responses of Pampean grassland mouse (Akodon azarae) with regard to population density in four 0.25 ha enclosures (two control and two experimental) in the 2011 breeding season. Based on the hypothesis that A. azarae breeding females exhibit spacing behaviour, and breeding males show a fusion spatial response, we tested the following predictions: (1) home range size and intrasexual overlap degree of females are independent of population density values; (2) at high population density, home range size of males decreases and the intrasexual home range overlap degree increases. To determine if female reproductive success decreases at high population density, we analyzed pregnancy rate, size and weight of litters, and period until fecundation in both low and high enclosure population density. We found that both males and females varied their home range size in relation to population density. Although male home ranges were always bigger than those of females in populations with high density, home range sizes of both sexes decreased. Females kept exclusive home ranges independent of density values meanwhile males decreased home range overlap in high breeding density populations. Although females produced litters of similar size in both treatments, weight of litter, pregnant rate and period until fecundation varied in relation to population density. Our results did not support the hypothesis that at high density females of A. azarae exhibit spacing behaviour neither that males exhibit a fusion spatial response.     

Movements and home range of ferrets (Mustela furo) at Pukepuke Lagoon,New Zealand

Abstract

Ferrets at Pukepuke Lagoon were live-trapped during the periods November 1970 to August 1973 and January 1976 to July 1977. Although the sex ratio of the 75 trapped ferrets was equal, there was a strong bias towards male captures in the earlier period (58.4%) and towards female captures in the later period (68.7%). Habitat modification and changes in the trapping programme for the later period probably resulted in the increased abundance and capture rate of females. Between consecutive captures 58.2% of male movements exceeded 250 m, as against on1y 39.7% of female movements; the mean distance between consecutive captures was 435 m for males and 285 m for females. Mean monthly movements varied from 700 m in January to 315 m in June for males, and from 360 m in March to 150 m in September for females. Juveniles of both sexes moved similar, intermediate distances. Dispersing juveniles were trapped from January until April; males tended to appear in traps earlier in the year than females. Only 4 of 14 juvenile males setNed as residents, hut 15 of 28 juvenile females did so. Male and female home ranges overlapped extensively, but within each sex individual ranges were usually separate. Resident males maintained a well defined spacing pattern, adjusting their boundaries if a juvenile settled or a neighbouring range became vacant. In 1976 six females had overlapping ranges in an area of albundant food. Female ranges (12.4 ha) were on average smaller than male ranges (31.3 ha); home ranges of both sexes were smaller during the breeding season (August-February) than at other times.     

Seasonal shifts within juvenile recruit sex ratio of Pampas mice (Akodon azarae)

Sex ratio (SR) variation of Akodon azarae juvenile recruits was analysed during 1985–86 on a Pampean grassland in central Argentina. Rodents were intensively live-trapped on a 0.81 ha grid. The SR (proportion of males) of the overall population did not differ significantly from evenness (0.49). In contrast, juvenile recruits (0.5–2.0 months of age) showed SR fluctuations according to their time of birth. SR was strongly female-biased among spring and autumn juveniles (0.13 and 0.33, respectively), while males were predominant (0.72) among the summer juveniles.
Social and demographic implications of these results are discussed in the framework of current SR theory. Spring female recruits should be selected for summer reproduction and autumn female recruits for winter survival and spring reproduction. The overwintered population was characterized by 1:1 SR and an age structure composed of males older than females. Most of these males had been recruited as juveniles during the summer. They also made up most of the resident male population in the spring. A selective allocation of energy by the mothers among their offspring is the mechanism proposed to explain the seasonal changes in SR, as pregnant females which gave birth to the summer recruits were in better physical condition than the mothers of both spring and autumn recruits. These results are consistent with the predictions of Werren & Charnov (1978), based on temporal overproduction of one or the other sex according to differential changes in the life-history expectations for both sexes.     

Home range size, habitat utilisation and movement patterns of suburban and farm cats Felis catus

The movements of 10 house cats (4 desexed females, 5 desexed males and 1 intact male) living on the edge of a suburb adjoining grassland and forest/woodland habitat, and a neighbouring colony of seven farm cats, were examined using radio-telemetry over nine months Nocturnal home range areas of the suburban cats varied between 0 02 and 27 93 ha (mean 7 89 ha), and were larger than diurnal home range areas (range 0 02 to 17 19 ha – mean 2 73 ha) Nocturnal home range areas of cats from the farm cat colony varied between 1 38 and 4 46 ha (mean 2 54 ha), and were also larger than diurnal home range areas (range 0 77 to 3 70 ha – mean 1 70 ha) Home ranges of cats in the farm cat colony overlapped extensively, as did those of cats living at the same suburban residence There was no overlap of home ranges of female cats from different residences, and little overlap between males and females from different residences Four of the suburban house cats moved between 390 m and 900 m into habitat adjoining the suburb Polygons describing the home ranges of these animals were strongly spatially biased away from the suburban environment, though the cats spent the majority of their time within the bounds of the suburb Movements further than 100–200 m beyond the suburb edge were always made at night There is evidence that home range sizes and spatial movement patterns of house cats are largely determined by a) the density and spatial distribution of cats utilising separate food resources, b) the personality and social dominance of individual cats, c) the location of favoured hunting and resting/sunning sites, and, d) barriers such as busy roads     

Population parameters of indigenous populations ofMyocastor coypus: the effect of hunting pressure

The coypu or nutriaMyocastor coypus Molina, 1782 is a semiaquatic rodent intensively harvested for fur in its native region. We studied population parameters at four sites differing in hunting pressure and characterised hunting activity in north-eastern Buenos Aires province, Argentina. Our interviews with hunters, local inhabitants and wildlife managers revealed that hunting is a cultural tradition in the countryside with the coypu being used as meat and, fur and the young occasionally used as pets. Quarterly live trapping captured a high proportion of all coypus present at each site. In sites with higher hunting pressure, low density of coypus was associated with high population losses and immigration. I n these sites the proportion of juveniles and pregnant females was similar to that obtained at sites with no hunting pressure. No foraging deficiencies were evident from diet quality analysis. Our results suggest that harvesting determines the dynamics of coypu populations in, this region where hunting pressure can be assessed by accessibility of hunting sites, their distance to urban or rural settlements, effective control of hunting, and human population density of the area.     

Molecular determination of paternity in a natural population of the multiply mating polygynous lizard Eulamprus heatwolei

We studied the mating system of the southern water skink, Eulamprus heatwolei, during spring and summer (encompassing the breeding season) in a population in southeastern Australia. We examined potential attributes that might influence the mating system and male reproductive success including home range size, physical proximity of adults and body size, and then genotyped all mothers, offspring and potential sires. Home range overlap of both sexes was extensive, with adult females sharing the greatest amount of space with each other and adult males the least amount of space with each other. However, not all adults hold home ranges. We classified approximately one quarter of adult males as home range holders and the rest as 'floaters'. Adult females occupy home ranges more than males, with approximately three-quarters classified as home range holders. Home range ownership is not correlated with body size for either sex, however, male body size is positively correlated with the number of adult female home ranges that his home range overlaps and adult male home ranges are larger than those of females. We used microsatellite genotyping to assign paternities to 55 offspring from 17 litters and then compared this data with our home range and behavioural observations. This species displays extreme levels of multiple paternity given the small mean clutch size of three. Multiple paternity was confirmed in 11 (64.7%) of 17 clutches but three other clutches (for a total of 82.4%) also may display multiple paternity. A total of 30 offspring from 12 litters were assigned to 10 of the 32 genotyped adult males from our study site. Of these 10 adult males, half were home range holders. Five complete clutches and a total of 25 out of the 55 offspring could not be positively assigned to any male surveyed as part of the study and were attributed to floater males or resident males adjacent to our study site that had not been genotyped. While sample sizes are small, neither male home range ownership nor body size is significantly correlated with the number of paternities a male obtained. Our study suggests a polygynous mating system for this species.     

Space use in the root vole: basic patterns and variability

Home range characteristics and spatial organization of the root vole Microtus oeconomus were assessed by radio-tracking The aim of this paper is to test the assumption that each microtine species employs a certain modal spatial system around which there is considerable flexibility In the studied population the basic modes of spatial organization were female territoriality and male use of overlapping home ranges Female territories were significantly smaller and less diversified in size than male ranges The size of male home ranges was positively correlated with body mass Each female territory was overlapped by several male ranges, larger male ranges usually overlapped more female territories The above spatial organization suggests that the prevailing mating system in the root vole is promiscuity, and larger males have an access to more receptive females than have small-sized males
Departures from these basic modes were found among young mature females from summer cohort, forming clusters even at low density, and occasionally among females in locally crowded habitat patches, where they held overlapping home ranges A single male usually monopolized such a cluster, excluding other males from the area used by the females     

Mating Tactics in Male Grey-Cheeked Mangabeys (Lophocebus albigena)

Reproductive tactics of males can change with individual quality, relatedness and social structure. Here we describe the behaviours of male grey-cheeked mangabeys towards other males, and females and their offspring ( Lophocebus albigena ) in relation to male status (high-ranking/low-ranking/transient) and group composition in Kibale National Park, Uganda. High-ranking males had the highest mating success, frequency of loud calls, mate guarding and aggression towards females and males. Only transient males were often observed to be aggressive towards juveniles, while some high-ranking males provided infant care. Mating tactics of high-ranking males varied greatly among the five studied groups, probably as a function of the intensity of male–male competition. These results are discussed with regard to the role of male–male competition and behaviours that could affect female mate choice as tactics to obtain reproductive success.     

Spacing system of the Mysore slender loris (Loris lydekkerianus lydekkerianus)

Loris lydekkerianus lydekkerianus has been shown to have a promiscuous copulatory pattern, to maintain social networks via frequent loud calls, to interact socially throughout the night with all age classes, and to sleep socially. Though these behaviors point towards a multimale social system, no study of their spacing system has yet been provided to support this view. From October 1997-August 1998, I conducted a study of the Mysore slender loris in Ayyalur, India. During 1,400 field hours, data were collected on range use of 3 adult females, 3 adult males, 1 subadult female, and 1 subadult male. Lorises slept in groups averaging 4 individuals, composed of an adult female, her offspring, and 1-2 adult and subadult males. Sleeping sites for three groups were located within 1.9 ha in the center of the study area. The minimum convex polygon in hectares encompassing each animal's range was determined, as well as overlap among home ranges of individual lorises. Average home range sizes were: adult males, 3.6 ha +/- 0.09; subadult/smaller males, 1.17 ha +/- 0.26; and adult and subadult females, 1.59 ha +/- 0.24. Male ranges overlapped with at least 2-3 other adult males (0.72 ha +/- 0.23). Female ranges overlapped slightly with at least 2 other female ranges (0.22 ha +/- 0.25). Male ranges overlapped those of at least 3 females (0.82 ha +/- 0.51). Patterns of home range and sleeping site support previous suggestions of a multimale social system, similar to aye ayes and some galagos.     

Home ranges of introduced mammalian carnivores at Trounson Kauri Park,Northland, New Zealand

Abstract

At Trounson Kauri Park, we monitored the movements of 21 feral cats (Felis catus), 11 stoats (Mustela erminea) and one male ferret (Mustelafuro). In feral cats, the average minimum home range was 446 ha (±82 SE) for 14 males, significantly larger than the average minimum of 117 ha (±40 SE) for seven females. In stoats the average minimum home range was 107 ha (±20 SE), for nine males compared with 81 ha (±31 SE) for two females. The single male ferret had a minimum home range of 197 ha. Adult male feral cats lived on apparently separate, non‐overlapping home ranges; females occupied exclusive home ranges which were overlapped by adult males; home ranges of sub‐adult male feral cats overlapped those of other sub‐adult male, adult male and female feral cats. The home ranges of two neighbouring male stoats overlapped, although their core ranges did not; both these and the ferret's home ranges overlapped those of the neighbouring feral cats. The feral cats were often located in cover in pastureland or near the edge of larger tracts of forest within their home ranges; stoats near waterways in the larger tracts of forest; and the ferret near the forest/pasture margins of Trounson Kauri Park. Our results suggest that control devices targeting all these species should be set at a minimum spacing of 800 m in order to put the majority of the resident and immigrant predators at risk.     

Male-biased reproduction and sex-ratio adjustment in muskrats

Summary Sex ratios of a population and of litters were sampled in muskrats in Ontario, Canada. Sex ratios of litters sampled from nests were male biased (54% male). Until weaning, no differential costs of producing and rearing male and female young were identified that could account for this greater production of males. Following weaning, however, male-biased dispersal of juveniles from their natal site and more frequent acquisition by females of these sites as breeding sites the following year suggested a greater investment by adult females in female young. Therefore, competition between female siblings for the acquisition of their natal site may be sufficient to result in the greater production of males. In addition, the simultaneous occupation of, and competition between, siblings and parents for the resources of the natal home range may not be necessary for local resource competition to result in a greater production of the dispersing sex. Greater-than-expected binomial variance in sex ratios of litters suggested that adjustment of sex-ratios occurred. However, we were unable to associate the adjustment of litter sex ratios with changes in maternal condition. The greater production of males and the predominance of monogamous associations between adults in this population may have lead to slightly greater variation in male fitness than female fitness. Therefore, a female in better-than-average condition may have benefited by producing more males. Similarly, a lower cost of producing dispersing males may allow nutritionally-stressed females to reduce their total expenditure on offspring by producing more males. Because these experiments were non-manipulative, maternal condition may not have varied sufficiently during this study to detect adjustments of litter sex ratios resulting from either of the above mechanisms acting separately, but the combined effects of small differences in matermal condition and selective pressures operating in the same direction may have resulted in the observed deviation from the binomial.     

Response by coypus to catastrophic events of cold and flooding

Population dynamics of the coypu, Myocastor coypus , were studied in central-West France. This species has recently colonized temperate regions despite physiological sensitivity to cold weather. Live-trapping over three years demonstrated that increasing population densities from summer into autumn were associated with a faster population turn-over, homogeneous dispersion, and reduced rates of weight gain. Densities fell by 71% over a cold winter in which canals froze for 20 consecutive days, and by 69% over a mild winter with a flood of 5 weeks duration. Mortality was high in the coldest weather, and 45% of those surviving had frost lesions. A scarcity of males after the cold winter (up to 1♂: 3.3♀) was matched in a nearby population at artificially low density, where dispersing males predominated after the flood. The effect of the cold winter on reproductive output was to synchronize littering in summer, at a time of rich food supply. It was concluded that a flexible response to winter conditions enabled coypus to minimize the effects of extreme events and maximize their colonizing potential.     

Mating system structure and population density in a polygynous lizard, Sauromalus obesus (= ater)

Increases in population density often are associated with achange in mating system structure in numerous taxa. Typically,male interactions are minimal in extremely low density populations.As density increases, males exhibit territoriality but if densitybecomes too high, the energetic cost of defending a territorywill eventually outweigh the reproductive benefits associatedwith territoriality. Consequently, males in high density populationsmay abandon territoriality and adopt dominance polygyny, lekking behavior, or scramble competition. We investigated the relationshipbetween population density and mating system structure in threepopulations of the chuckwalla, Sauromalus obesus (= ater),near Phoenix, Arizona. Densities in the Phoenix Mountains (2.7chuckwallas/ha) were lower than any population previously studied.In the Santan Mountains (10.9 chuckwallas/ha), densities weresimilar to populations studied in the Mojave Desert, and inthe South Mountains (65 chuckwallas/ha), densities were the highest yet recorded. Male mating behavior was examined by determininghome range overlap and by making direct behavioral observations.Male home range size decreased with increasing population density.There was little overlap in home ranges among males in allthree populations, whereas home ranges of males and femalesconsistently overlapped, indicating that males were strictly territorial. This conclusion was supported by behavioral observationsof interactions among individuals in a natural setting. Thenumber of females wihin male territories was correlated withfood resources (plants) in all three populations. Female homerange size appeard to be related to food resources whereasmale home ranges appeared to be related to female distribution,population density, and geology. The retention of territoriality in spite of high population densities raises new questions aboutthe relationship between density and resource defense.     

Do male roe deer clump together during the rut?

Movement s an d habitat use of 7 male and 7 female roe deerCapreolus capreolus (Linnaeus, 1758) were studied by radioteleme try from March 1999 to February 2001. Annual and bimonthly home ranges of males were small (ca 10 ha, 95% kernel), with large overlap among individuals throughout the year. Exclusive core areas (ca 0.4 ha, 25% kernel) were concentrated in the forest, a limited and sought-after resource in the study area. The difference in overlap between male exclusive core areas and female home ranges in the pre-rut and rut periods suggested that females made excursions to search for territorial males during the rut Our results support the mating strategy hypothesis of territorial behaviour Different space use patterns occurred between the sexes, with females apparently playing an active role in mate choice by visiting males at clumps of core areas in the forest.     

Spatial organization of the arboreal carnivorous marsupial Phascogale tapoatafa

Phascogale tapoatafa is a squirrel-sized carnivorous marsupial (Dasyuridae) found in dry eucalyptus forests of Australia. Radio-tracking and live-trapping studies at three sites in Victoria indicated that population densities were typically low, with females occupying home ranges averaging 41 ha (minimum convex polygon method) that were intrasexually exclusive. Male home ranges (mean 106 ha) overlapped extensively with females and other males, and expanded during the short breeding season to an average length of 2.7 km. When presented with the faeces of unfamiliar conspecifics, both female and male P. tapoatafa investigated the faeces of females significantly longer than those of males, suggesting that the exclusive home ranges of females are reinforced by olfactory communication, and that males are less responsive to the presence of potential rivals than to potential mates. Both sexes foraged throughout their home range, but the core area of intensive use was less than one-third of the total area traversed. The spatial organization of P. tapoatafa differs markedly from that of the closely related species Antechinus stuartii , but is similar to that of the only other extensively studied carnivorous marsupial, Dasyurus geoffroii.     

A telemetry-based study of bushbuck (Tragelaphus scriptus) home range in Valley Bushveld

With the aid of radio‐telemetry, bushbuck home range was investigated to determine total home range size, home range utilization and home range overlap for the summer season. Estimates of total home range size for males using minimum convex polygons (MCPs) and fixed kernels (FKs) were 33.9 and 32.1 ha, respectively. Estimates of total home range size for females using MCPs and FKs were 12.0 and 13.5 ha, respectively. A significant difference between total home range sizes for male and female was found but there was no significant difference for age (adult and subadult). Female bushbuck home range size was compared to that expected from the published allometric relationship for the scaling of home range area on body mass, where the study animals appeared to have home ranges of half of that predicted. Bushbuck typically utilized one core area within their home ranges in which 50% of their time was spent in approximately 17.0% and 11.7% of their total home range for males and females, respectively. A substantial overlap in total home range and core areas between animals was found.     

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.     

The reproductive success of female coypus in a feral population: variation in relation to age, fat reserves and the availability of mates

An introduced population of coypus ( Myocastor coypus ) has lived in the wetlands of eastern England since the 1930s. Female reproductive biology has been studied over a 17 year period using information from post mortem examinations of animals caught in a trapping campaign. Females breed throughout the year and produce litters. Litter size at conception and prenatal mortality vary in relation to the mother's age and nutrient reserves. Some embryos are resorbed and some die at or shortly after birth, perhaps to reduce litters to a size that the mother can support. In addition, selective mortality of male and female embryos may allow mothers to manipulate offspring sex ratio (Gosling, 1986). The proportion of females that have litters each year also varies in relation to population density. This variation may be mediated by both the food supply and the availability of mates (Gosling and Baker, in press).     

Space use of common genets<Emphasis Type="Italic">Genetta genetta</Emphasis> in a Mediterranean habitat of northeastern Spain: differences between sexes and seasons

The seasonal home range size and spatial relationships of 16 adult genetsGenetta genetta Linnaeus, 1758 (6 males and 10 females) were estimated in a Mediterranean habitat of northeastern Spain. Genets minimum density was estimated as 0.98/km². Mean annual home range was 113.1 ha in males and of 72.0 ha in females. Males had larger home ranges than females in all seasons, but differences were only significant in winter. Home range size changed seasonally and showed a similar pattern in both sexes, with lower values in summer (males — 41.2 ha, females — 29.0 ha) and maximum ones in spring (males — 78.8 ha, females — 56.1 ha). Animals displayed spatial fidelity throughout the year. Core areas (MCP50) represented 27% and 19% of total home range size for males and females, respectively. Resting home ranges (based on locations of inactive animals) were 9 times lower than overall home range size. Individuals of the same sex overlapped less than individuals of different sexes, especially with regard to core areas, which showed almost no overlap. The results obtained suggest that (1) different factors are likely to affect the space use of genets, such as body mass, food abundance and reproductive cycle; (2) genets use space in a heterogeneous way, with areas of greater activity than others within their home range; (3) there was intrasexual segregation with regard to space use.