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Female body mass and reproduction from harvested moose Alces alces were compared in four populations of moose at different stages (densities) of population development, i.e. pre-peak, peak and post-peak, in Sweden during 1961–1991. In two (1 and 2) of the four populations, age-related body mass and reproduction was significantly lower in the post-peak (intermediate density) stage than in the pre-peak stage; whereas for the other two populations (3 and 4), no differences, or higher growth and reproduction at post-peak density, were found. In one population (2) data from all three stages (densities) of population development were available. Age-specific mean body mass was 12.8% lower, and fecundity 46.0% lower (average among age classes), during the peak density stage, than during the pre-peak stage, but did not differ significantly between the peak and post-peak stages, except for fecundity in 1.5-year-old females. In the two populations showing a negative density-dependent response (1 and 2), fecundity decreased more from pre-peak to post-peak density than could be predicted from the reduction in body mass. This suggested a lower reproductive investment per unit body mass at high and intermediate densities, compared to the low density stage. Similar to age-related body growth and fecundity, the proportion of lactating and/or calf-rearing females was significantly lower at post-peak population density in populations 1 and 2 compared to pre-peak densities, but only in the youngest reproducing age class (2.5 years). It is concluded that: i) the large increase in population density has resulted in density-dependent resource limitation, which is expressed as lowered body growth and reproduction in two of the four populations studied; ii) the lower reproductive investment per unit body mass at higher densities may constitute an adaptive strategy to maximise juvenile survival as conditions deteriorate; iii) density-dependent effects in moose may occur at densities which are lower than close to the ecological carrying capacity; and iiii) the variable density-dependent pattern among populations may be due to differential harvest regimes, causing variable post-peak densities, and thus different levels of resource competition among populations.
Female barnacle geese Branta leucopsis were studied on their spring staging area on the coast of mid-Norway and 1,500 km further to the north on their breeding areas in the Arctic archipelago, Svalbard. The number of days between departure from their spring staging area and arrival on their breeding area ranged between 10 and 33 days. There was no significant relationship between the date of departure and the date of arrival for individual females (N = 51), indicating that early-leaving females were not necessarily the first to arrive at the breeding grounds. Late-arriving females were in better body condition upon arrival than early-arriving females (N = 25). These data imply that the barnacle geese breeding in Svalbard do not migrate directly from their traditional spring staging areas to their breeding areas, but spend a considerable amount of time, not only resting, but also feeding during their migration northwards. This result has important implications for the management of the barnacle goose population on Svalbard since areas other than their traditional spring staging grounds apparently determine the date of arrival at the breeding grounds, body reserves at arrival and subsequent reproduction.
The effect of mature forest fragmentation on breeding success of vole-eating Tengmalm's owls Aegolius funereus was studied in western Finland during 1981–1995. The owl pairs produced more fledglings in territories with high (>30%) proportions of clear-cut and plantation areas than in territories with low (<30%) proportions of such areas. Territory occupancy, clutch size, laying date, and parental characteristics such as wing length, body mass and age were not associated with the proportion of clearcut areas within territories. Snap-trapping data from the ‘increase’ vole year 1994 revealed that the Microtus vole density tended to be higher in large clear-cuttings than in small ones. The increasing amount of sapling and clear-cut areas in coniferous forests during the last three decades has created suitable grass habitats for Microtus voles, and simultaneously new hunting habitats for Tengmalm's owls. Therefore, forest fragmentation due to clear-cuttings may benefit Tengmalm's owls at the present scale. However, nest-boxes should be erected and old groves should be protected, because forest harvesting apparently reduces the number of suitable natural cavities for owls in the long run.
An omnibus procedure for Alectoris partridges density estimation is still lacking. The suitability of driven line and strip transect sampling for estimating red-legged partridge Alectoris rufa densities on mixed farmland, in southern Portugal, in March, May and July 1993 and 1994 was evaluated. Driven transect counts along a grid of dirt tracks were performed and compared to early spring territory mapping counts. Distance data sets exhibited prominent peaks near the origin, apparently caused by attraction of the birds to the tracks; nevertheless, line transect estimates computed using Fourier series models were similar to mapping counts in March of both years, as well as adult density estimates in July, but density was underestimated in May 1994. Line transect estimates were robust to the shift from individuals to clusters as sighting units, and to different grouping options, but not to data truncation. Driven strip transect estimates were computed using 10 m, 20 m, 40 m, 80 m, and 160 m strip widths. In March, estimates computed using the first three widths overestimated density and underestimated it in 1994 when the 160-m strip was used. May and July adult density estimates were not significantly different from those in March. In this study, driven line transect sampling was an efficient and accurate method of estimating red-legged partridge density on a farmland area in early spring and summer; however, further research is needed to evaluate its suitability in habitats of lower visibility, as detection models seem to require long-distance sightings to compensate for the attractiveness of tracks. Strip transects are not recommended because of the difficulty of choosing an adequate strip width for density estimation. Both methods revealed similar utility as indices of relative population abundance.
In the UK and elsewhere in Europe, high densities of mountain hares Lepus timidus are associated with heather moorland, the area of which has been diminished by large-scale afforestation. The consequences of this landscape change for the diet composition and body weight of mountain hares were investigated by comparing mountain hare carcasses collected in November 1990 simultaneously from a large hare-fenced, young forestry plantation and from the adjacent heather moorland. The sex, age, diet composition and body weight of individual hares were recorded. There were readily identifiable differences in the diet composition and body weight of hares that occupied the two different habitats, the segregation of which had been rigorously maintained for the previous nine months and included the period of births of leverets. Adult females and leverets in the young forestry plantation had a higher proportion of grasses and a lower proportion of heather in their stomachs than the same age/sex classes on the open moorland, and leverets occupying the forestry plantation were significantly heavier than those inhabiting the moorland habitat. Large-scale afforestation results in an improvement in diet quality and body weights in young mountain hares during the early plantation stages, and in those early years following planting, commercial afforestation is probably not detrimental to mountain hare populations. Persistence of mountain hare populations in afforested landscapes could be facilitated by the incorporation of appropriate young age classes of forest.
Brown bears Ursus arctos in Spain's Cantabrian Mountains are continuing to decline in numbers despite their protected status. Recovery plans for this population stress the need for monitoring of occupied habitat using non-intrusive methods. A population monitoring program to estimate bear abundance indices by quantifying tracks and scats (sign surveys) along a network of survey routes was designed. Each route was divided into consecutive 1,6-km segments, which comprised the basic sampling unit, and were assumed to provide independent observations. During a 3-year pilot study surveys were run twice per year, totaling 70 routes, including 950 segments, and covering over 1,500 km annually. Averages of 0.06 sign per segment were observed; only 4% of the segments had sign. It is concluded that the present sampling scheme does not provide enough statistical power to accurately detect significant declines in population level. The difficulties of monitoring trends of low density populations using surveys are recognized. However, by increasing the sampling intensity, more reliable information and greater precision of the population trend estimate should be obtainable. Thus, a future monitoring strategy should be based on increasing sampling intensity and closely monitoring bear distribution and occurrence.
Food selection by adult red foxes Vulpes vulpes was studied in a mountainous environment characterised by fluctuating populations of water voles. According to optimal foraging theory, the diets of adults and cubs should be similar during vole highs, with voles as staple prey. On the other hand, a difference should occur when water voles become scarce. Adults should then bring larger alternative prey to their cubs, and consume smaller prey at the capture site. Adult and cub scats were collected around breeding dens during a 6-year period, from the peak to a near-extinction phase of the water vole population, and analysed. As predicted by the optimal foraging theory, no significant difference was found between the diets of cubs and adults when voles were abundant. Furthermore, cubs consumed a higher proportion of large alternative prey, i.e. lagomorphs, than adults in the first year of low vole density. Unexpectedly, this difference did not persist the following years despite the water vole scarcity. The consumption of large alternative prey at the den decreased significantly, whereas the consumption of small alternative prey, i.e. invertebrates, increased. Consequently, the composition of prey brought to the den was similar to that consumed at the capture site. Food selection was probably affected by the unpredictability of large prey availability and accessibility. It is suggested that if small alternative prey proves less profitable to the cubs than large prey, a long-lasting shortage of water voles could possibly become a factor regulating fox numbers in the area studied.
Knowledge of directional tendencies among long-distance movements by animals can be important in planning conservation and management strategies for wildlife at the landscape scale. The direction of 23 long-distance movements (≥2 km) among a non-migratory population of white-tailed deer Odocoileus virginianus on the Osceola National Forest, Florida, during 1989–1991 was examined. Direction of dispersal by 10 yearlings (7 males, 3 females) was non-uniform in distribution and averaged 95°. Direction of 13 excursions by 12 adults (2 males, 10 females) also was non-uniform but was bimodally (east-west) distributed; mean directions of the two distributions were 83° and 261°. Thus, both excursions and dispersals of radio-instrumented deer were on an east-west axis. No prominent landscape features that would direct deer movement were apparent. However, the fact that deer movements followed a consistent directional trend, even in a relatively homogeneous landscape, may have important implications for management of gene flow among small populations.
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