Spatial memory, habitat auto-facilitation and the emergence of fractal home range patterns

Animals interact with their habitat in a manner which involves both negative and positive feedback mechanisms. We apply a specific modeling approach, “multi-scaled random walk”, for the scenario where a spatially explicit positive feedback process emerges from a combination of a spatial memory-dependent tendency to return to familiar patches and a consequently objective or subjective improvement of the quality of these patches (habitat auto-facilitation). In addition to the potential for local resource improvement from physically altering a patch, primarily known from the ecology of grazing ungulates, auto-facilitation from site fidelity may also embed more subtle subjective, individual-specific advantages from patch familiarity. Under the condition of resource superabundance, fitness gain from intra-home range patch fidelity creates a self-reinforcing use of the preferred patches on expense of a broader foraging in a priori equally favorable patches. Through this process, our simulations show that a spatially fractal dispersion of accumulated locations of the individual will emerge under the given model assumptions. Based on a conjecture that intra-home range patch fidelity depends on spatial memory we apply the multi-scaled random walk model to construct a spatially explicit habitat suitability parameter H_ij, which quantifies the dispersion of the generally most constraining resource from the individual's perspective. An intra-home range set of observed H-scores, H_obs, can then be estimated from a simple 2-scale calculation that is derived from the local dispersion of fixes. We show how the spatially explicit habitat utilization index H_obs not necessarily correlates positively with the local density fluctuations of fixes. The H-index solves some well-known problems from using the pattern of local densities of telemetry fixes - the classic utilization distribution - as a proxy variable for relative intra-home range habitat quality and resource selection. A pilot study on a set of telemetry fixes collected from a herd of free-ranging domestic sheep with overlapping summer home ranges illustrates how the H-index may be estimated and interpreted as a first-level approach towards a more extensive analysis of intra-home range habitat resource availability and patch preferences. Spatial memory in combination with site fidelity requires a modeling framework that explicitly describes the property of positive feedback mechanism under auto-facilitation in a spatio-temporally explicit manner.     

Estimated home ranges can misrepresent habitat relationships on patchy landscapes

Home ranges of animals are generally structured by the selective use of resource-bearing patches that comprise habitat. Based on this concept, home ranges of animals estimated from location data are commonly used to infer habitat relationships. Because home ranges estimated from animal locations are largely continuous in space, the resource-bearing patches selected by an animal from a fragmented distribution of patches would be difficult to discern; unselected patches included in the home range estimate would bias an understanding of important habitat relationships. To evaluate potential for this bias, we generated simulated home ranges based on optimal selection of resource-bearing patches across a series of simulated resource distributions that varied in the spatial continuity of resources. For simulated home ranges where selected patches were spatially disjunct, we included interstitial, unselected cells most likely to be traveled by an animal moving among selected patches. We compared characteristics of the simulated home ranges with and without interstitial patches to evaluate how insights derived from field estimates can differ from actual characteristics of home ranges, depending on patchiness of landscapes. Our results showed that contiguous home range estimates could lead to misleading insights on the quality, size, resource content, and efficiency of home ranges, proportional to the spatial discontinuity of resource-bearing patches. We conclude the potential bias of including unselected, largely irrelevant patches in the field estimates of home ranges of animals can be high, particularly for home range estimators that assume uniform use of space within home range boundaries. Thus, inferences about the habitat relationships that ultimately define an animal's home range can be misleading where animals occupy landscapes with patchily distributed resources.     

综合管廊兼顾疏散能力分析及辐射范围研究*

为研究综合管廊在安全疏散中的作用,应用Pathfinder疏散仿真软件对综合管廊疏散能力模拟分析,得出不同断面管廊通道、各疏散口部、楼梯处通过能力,分析管廊人员在单车、步行疏散速度下覆盖范围与事故波及范围,通过两者交集得到综合管廊疏散辐射范围。结果表明:综合管廊具备一定兼顾疏散能力,得出的通过能力可指导综合管廊人流量监控器布局,提供各部位人流量上限取值,预防拥堵和踩踏事故发生,为化工园区制定疏散方案提供新思路。     

Spatial relationships and matrilineal kinship in African savanna elephant (Loxodonta africana) clans

African savanna elephants, Loxodonta africana, live in stable family groups consisting of adult females and their dependent offspring. During the dry season, clans consisting of several family groups typically share a common home range. We compared spatial relationships and mitochondrial DNA (mtDNA) haplotypes among 14 adult female elephants within 3 clans during the dry season in northern Zimbabwe. Spatial relationships were studied by radio-tracking. Home-range similarity was quantified by correlating the estimated utilization distributions of all pairs of elephants. Clans were identified by cluster analysis of the home-range similarity values. All three clans contained at least two of the five mtDNA haplotypes that were found, indicating that clan members are not necessarily matrilineally related. Within clans, home ranges of elephants with the same haplotype were not significantly more similar to each other than those of elephants with different haplotypes. Most elephants within each clan used their shared home ranges independently of each other: the distribution of distances between their positions at any given time did not differ from the distribution expected by chance. However, 8 out of the 26 within-clan pairs exhibited long-term coordination of space use by remaining within known hearing distance of each others low-frequency calls significantly more often than expected by chance. At least four of these coordinated pairs consisted of animals in different family groups. Elephants in three of the four different-family pairs whose movements were coordinated had different haplotypes. Further research is needed to determine the relationship between these coordinated movements and conventionally defined bond-group behavior.Electronic Supplementary Material Supplementary material is available in the online version of this article at .Communicated by C. Nunn     

An Ecological Basis for Managing Giant Sequoia Ecosystems

A strategy for management of giant sequoia groves is formulated using a conceptual framework for ecosystem management recently developed by Region Five of the USDA Forest Service. The framework includes physical, biological, and social dimensions. Environmental indicators and reference variability for key ecosystem elements are discussed in this paper. The selected ecosystem elements include: 1) attitudes, beliefs, and values; 2) economics and subsistence; 3) stream channel morphology; 4) sediment; 5) water; 6) fire; 7) organic debris; and 8) vegetation mosaic. Recommendations are made for the attributes of environmental indicators that characterize these elements. These elements and associated indicators will define and control management activities for the protection, preservation, and restoration of national forest giant sequoia ecosystems.     

EFFECTS OF SIMULATED CANOPY COVER AND ANIMAL DISTURBANCES ON RILL AND INTERRILL EROSION1

ABSTRACT: A rainfall simulator was used on runoff plots to study the effects of simulated canopy cover, trampling disturbance, and soil type on nil and interrill erosion. Sandy loam soil was more erodible than clay loam soil. Furthermore, the simulated canopy cover signffi-Soilfactorsrelatedtonil cantly influenced nil and interrill erosion. The effect of trampling on rill and interrill erosion varied with soil type (clay loam versus sandy loam) and erosion type (nh versus interrill erosion). On large plots, where both nil and internill erosion were involved, 30 percent trampling significantly increased soil loss. However, on small plots, 30 percent trampling significantly reduced interrill erosion.     

基于CVM的旅游相关资源价值评估总体范围扩展方法研究

条件价值评估法(CVM)是旅游相关资源价值评估的重要方法,其评估结果的准确性主要由支付意愿(WTP)或补偿意愿(WTA)和总体范围扩展两者决定。目前,国内外关于CVM方法的相关研究主要是针对提高WTP(或WTA)的准确性,而关于总体范围扩展方法的相关研究较少。国外旅游相关资源价值评估总体范围主要扩展为使用者,或资源所在区域的家庭,或资源所在邻近区域的家庭;国内主要扩展为使用者,或资源所在区域的居民,或资源所在区域的就业者,或全国范围的相关居民或就业者;这些总体范围扩展方法均存在一些缺陷。论文以调查样本信息为依据,提出了一种基于旅游相关资源关注度系数(用出游小区相对旅游率表示)的非使用者总体范围扩展方法和基于游客量的使用者总体范围扩展方法,并以舟山普陀金三角景区非使用价值评估为例,以2008年为评价基准年份,进行了实证分析。结果表明:普陀金三角旅游资源非使用价值为345.83×10⁶元/a,其中非使用者贡献159.21×10⁶元/a,国内使用者贡献184.17×10⁶元/a,国外使用者贡献2.45×10⁶元/a。并与国内外各种总体范围扩展计算的结果进行对比,该结果较为合理。     

Spatial organization and behaviour of badgers <Emphasis Type="Italic">(Meles meles)</Emphasis> in a moderate-density population

Badgers are carnivores that show considerable variation in their social and spatial organization. At the westernmost part of their range, in Britain and Ireland, variation in spatial organization appears to be determined by the availability of resources. However, the majority of studies has focussed at one end of the social/spatial spectrum, where population densities are high and adjacent territories are contiguous and non-overlapping. To examine whether the same limiting factors appear to apply across a wider range of badger densities, we established a study site in a predominantly coniferous habitat within an upland area of northeast England, where population densities were predicted to be low. Seasonal home ranges of individual badgers were largest in autumn, followed by summer and spring, then winter. This pattern is reflective of the likely seasonal changes in food availability within the area, as opposed to being related to breeding patterns. There were also significant correlations between territory size and the number of grassland patches (positive) and the proportion of grassland (negative), which are consistent with predictions from the Resource Dispersion Hypothesis. Although badgers at the site were living at low to moderate densities relative to many other studied populations in Britain, they showed patterns of spatial organization that were close to those of high-density populations. The nature of the relationship between resource availability and abundance patterns is likely to have important consequences for the conservation and management of badgers and other species that show flexible spatial organization.     

Bisexually bonded ranging in chimpanzees (Pan troglodytes verus)

Abstact While male mammals seek to maximize access to potential mates, females maximize feeding efficiency. Ranging patterns are therefore often sex specific. Sex-specific ranging patterns have also been reported for East African chimpanzees and a recent study on female ranging patterns concludes that social organization is best described by a male-bonded community model, where females occupy individual home ranges that are distributed within the boundaries of the male-defended range. In West African chimpanzees, however, such sex-specific ranging patterns have not been consistently observed and a bisexually bonded community model, where both sexes use the entire home range equally, has been suggested to best describe social organization. In this study we analyze 5 years of data on individual ranging patterns of chimpanzees in the Taï National Park (Côte dIvoire) to test specific predictions of the different models of chimpanzee social organization. We found that although males in Taï had slightly larger home ranges than females, all individual home ranges and core areas overlapped highly. Small individual home range size differences were entirely due to the use of peripheral areas and were correlated with female social dominance. These findings strongly support the bisexually bonded community model for Taï chimpanzees. Thus, we conclude that there are fundamental differences in the space-use patterns of East and West African chimpanzees and discuss possible factors leading to such differences.Communicated by D. Watts