Exploring the relationship between NDVI and African elephant population density in protected areas

Assessing the extent to which populations are limited by bottom‐up processes driven by food limitation is crucial to our understanding of how ecosystems should be managed. Using satellite‐derived Normalised Difference Vegetation Index (NDVI) as an index of resource availability, we investigated the relationships between greenness levels and African elephant (Loxodonta africana) population densities. Our results unveiled a positive relationship between NDVI and elephant densities in nonforest populations, but failed to capture any significant effects of survey area and type, number of years after the continental poaching ban and the IUCN category of the protected area in which the survey was undertaken. The number of forest elephant populations for which density estimates were available was very low, and no significant relationship between NDVI and forest elephant density could be established. Altogether, our study suggests that NDVI can successfully be linked to megaherbivore abundance across Africa and further highlights that a continental approach to energy–abundance relationships can be conducted in a relatively low‐cost manner and short timescale, supporting managers' efforts to identify future suitable areas for elephant populations.     

Time geography and wildlife home range delineation

We introduce a new technique for delineating animal home ranges that is relatively simple and intuitive: the potential path area (PPA) home range. PPA home ranges are based on existing theory from time geography, where an animal's movement is constrained by known locations in space–time (i.e., n telemetry points) and a measure of mobility (e.g., maximum velocity). Using the formulation we provide, PPA home ranges can be easily implemented in a Geographic Information System (GIS). The advantage of the PPA home range is the explicit consideration of temporal limitations on animal movement. In discussion, we identify the PPA home range as a stand-alone measure of animal home range or as a way to augment existing home range techniques. Future developments are highlighted in the context of the usefulness of time geography for wildlife movement analysis. To facilitate the adoption of this technique we provide a tool for implementing this method. © 2011 The Wildlife Society.     

Daily movements and home range of Eastern Hermann's Tortoise,Testudo hermanni boettgeri (Reptilia: Testudines)

Understanding the movements of animals in the wild is critical for providing important information regarding their conservation and management. With this aim in mind, we studied a population of Testudo hermanni in their natural habitat using micro GPS devices. Additionally, using VHF transmitters we tracked six individuals (four females and two males) from May to August 2015. The overall home range size varied from 813 and 123,567 m². Home range size did not differ significantly between males and females, and was also independent of the size of the individual (expressed as straight carapace length). Individual movements were confined to short distances (males 25.7 m; females 18.5 m). Activity levels were highest in July and August for males and May and July for females.     

Home range size scales to habitat amount and increasing fragmentation in a mobile woodland specialist

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Plant biodiversity patterns along a climatic gradient and across protected areas in West Africa

Knowledge of spatial patterns of biological diversity is fundamental for ecological and biogeographical analyses and for priority setting in nature conservation, particularly in West Africa where the existing high biodiversity is increasingly threatened by human activities. The maximum entropy approach was used to model the geographic distribution of 3,393 vascular plant species at a spatial resolution of 0.0833°. Species richness decreases along temperature and precipitation gradients with high species numbers in the south and lower numbers towards the north of the transect. All centres of plant species diversity are confined to humid areas in concordance with the high positive correlation between species richness and rainfall which appears to be the most important delimiter for the distribution ranges of many species in the area. The effectiveness of the existing protected areas at regional and national levels is investigated based on the proportion of species covered. Considering the whole study area, 95% of all species are covered by protected areas according to their distribution ranges. However, the proportion of species covered is considerably lower for some countries such as Benin and Togo. Our results could provide guidance for essential land use management interventions to decision‐makers and conservationists in the region.     

Home range and seasonal movements of Giraffa camelopardalis angolensis in the northern Namib Desert

Estimates of home range size of giraffe in the northern Namib Desert were on average larger than those in other populations. In particular, the largest individual home range of any giraffe bull (1950 km²) was recorded – correlated with low population density, reduced forage density and increased searching for receptive cows. The predominant pattern of movement was linear, along the riparian environments, however, large-scale irregular movements into tributaries and other areas were also recorded. Small-scale movements by bulls into the mountains above the Hoarusib River as well as by cows into the northern tributaries of the Hoanib River were observed. Seasonal movements of giraffe were not as distinctive as those in other giraffe populations. Small-scale habitat segregation was observed in the Hoarusib River study area with giraffe cows foraging only in the Gomatum River during the hot-dry season. The first ever study of GPS satellite collared giraffe provided some of the highest resolution data on giraffe movements to date, including strong biphasic movement behaviour of giraffe over 24-h periods.     

Habitat utilization and home range of the redwing francolin, Francolinus levaillantii, in highland grasslands, Mpumalanga province, South Africa

The effects of intensive commercial livestock farming on the distribution and habitat use of the redwing francolin, Francolinus levaillantii, was investigated to identify habitat constraints that may contribute towards the observed decline of this species on livestock farms. Data on the size, placement of the home ranges and compositional habitat use from ten radio‐tracked individuals, five in commercially grazed (and frequently burned) and five in protected (and infrequently burned) highland grasslands, was collated to determine habitat preferences. Mean home range size within protected and grazed grassland study sites were similar and ranged between 7.6 and 15.4 hectares. However, habitat use by groups in grazed grasslands was restricted to areas of greater cover and food availability. Group sizes were significantly larger in protected (mean 3.77, n = 111 coveys) than in grazed and frequently burned grassland (mean = 2.96, n = 135 coveys). Smaller coveys in grazed habitats had smaller home ranges and were further spaced from one another. It is therefore suggested that habitat degradation, through excessive defoliation of the grassland from heavy grazing and frequent burning, both fragments francolin subpopulations and reduces the ecological availability of suitable habitat. Thus, undermining the metapopulation structure of the redwing francolin in these commercially grazed grasslands.     

人类足迹对东北虎豹国家公园景观破碎化的影响

探讨人类活动对东北虎豹国家公园景观破碎化的影响,对于掌握东北虎豹保护与人类发展之间的矛盾,优化虎豹栖息环境具有重要意义。基于人类足迹理论构建适地化的人类足迹指标体系,结合景观格局分析、回归分析、GIS空间分析等方法,从全局和局部两个角度探讨了各人类足迹指标对东北虎豹国家公园及核心保护区、一般控制区(虎豹潜在栖息地)、一般控制区(人口聚集区)三大管控分区景观破碎化的影响范围及其空间分异特征。结果表明：(1)虎豹公园内较高、高度景观破碎化区域占公园全域面积的8.96%,且主要分布在一般控制区(人口聚集区)中,占比高达60.54%;(2)从公园全域来看,对景观破碎化的影响从高到低的人类足迹指标依次为土地利用状况,交通可达性、人口密度、工矿活动,夜间灯光强度与景观破碎化的相关性不显著;(3)从各管控分区来看,核心保护区、一般控制区(虎豹潜在栖息地)与公园全域具有相似的规律,而在一般控制区(人口聚集区)中,工矿活动的影响程度上升到第二位;(4)从区域上占主导的人类足迹指标来看,以土地利用状况影响为主的区域最为广泛;以交通可达性影响为主的区域分布在春化镇、大肚川镇、春阳镇周边地区;以人口密度影响为...     

Staying close to home: Ecological constraints on space use and range fidelity in a mountain ungulate

Understanding patterns of animal space use and range fidelity has important implications for species and habitat conservation. For species that live in highly seasonal environments, such as mountain goats (Oreamnos americanus), spatial use patterns are expected to vary in relation to seasonal changes in environmental conditions and sex‐ or age‐specific selection pressures. To address hypotheses about sex, age, and seasonality influence on space‐use ecology, we collected GPS location data from 263 radio‐collared mountain goats (males, n = 140; females, n = 123) in coastal Alaska during 2005–2016. Location data were analyzed to derive seasonal and sex‐specific fixed‐kernel home range estimates and to quantify the degree of seasonal range and utilization distribution overlap. Overall, we determined that home range size was smallest during winter, expanded coincident with the onset of green‐up and parturition, and was largest during summer. Home range size of males and females did not differ significantly during winter, but females had larger home ranges than males during summer, a relationship that was switched during the mating season. Pairwise comparisons involving individual females across subsequent years indicated home ranges were significantly smaller during years when they gave birth to offspring. Mountain goats exhibited a strong degree of range fidelity, and 99% (n = 138) of individual animals returned to their previous year''s seasonal range with an average annual Bhattacharyya''s affinity utilization distribution overlap index of 68%. Similarity of seasonal home range utilization distributions varied in relation to sex and season in some respects. Home range overlap was highest during the summer vegetation growing season, particularly among females. These findings advance our understanding about how environmental variation and sex‐ and age‐related reproductive constraints influence space use and range fidelity among alpine ungulates. Documentation of the high degree of range fidelity among mountain goats has important conservation implications in landscapes increasingly altered by anthropogenic activities.     

西藏雅鲁藏布江中游斑头雁的越冬种群数量、分布和活动区

斑头雁(Anser indicus)是高致病性禽流感病毒的易感鸟类和潜在的传播源,在禽流感防控中占有重要地位。有关斑头雁的越冬种群现状缺乏研究。2009年1月,在雅鲁藏布江中游共统计到越冬斑头雁44657只,主要分布于一江两河地带的林周县、日喀则市、白朗县、拉孜县、江孜县和贡嘎县境内。这一统计数据远高于1990年代的统计数量,由此可将其全球种群数量估计值由5.2-6万只修正为至少7万只。越冬斑头雁的平均集群大小为(208±262)只(n=215),主要栖息环境包括冬小麦田、冬歇期农田、河流湖泊和沼泽湿地,其中在冬歇期农田中统计到的数量占72.1%。2006-2008年,对青海湖繁殖斑头雁的卫星跟踪表明,其越冬地点主要位于西藏雅鲁藏布江流域、拉萨河流域和印度,越冬期为11月至翌年的3月份,在越冬地平均停留(108±30)d,越冬活动区大小为(122.22±124.94)km2(n=3)。受西藏独特的宗教传统和农耕畜牧结合的生产方式的影响,越冬斑头雁经常与大量家畜和水鸟混杂在农田觅食,在禽流感疫情防控时应引起重视。     

Home range,core areas and movement in the ‘critically endangered’ kipunji (Rungwecebus kipunji) in southwest Tanzania

Understanding how threatened forest primates use a heterogeneous landscape is essential to ensuring their survival. Kipunji (Rungwecebus kipunji) are ‘critically endangered’, arboreal monkeys restricted to two sites in Tanzania. Over 90% of the population lives in the degraded Rungwe‐Kitulo forests of the Southern Highlands. In this study, we present the first comprehensive investigation into daily path length and home range size of kipunji, based on data from four groups followed simultaneously over 70 consecutive days on Mt. Rungwe. The mean daily distance travelled was 1293 m (SE 150.82), and daily distance was not significantly correlated to group size. Using fixed kernel density estimation, an area enclosing 90% of the home range calculated using the ‘reference’ method as a smoothing parameter, measured a mean of 306.18 ha (SE 67), and the core area (50% use) was 86.55 ha (SE 18.73). Using the ‘least‐squares cross validation’ method, the mean home range and core area were 205.45 ha (SE 57.02) and 55.45 ha (SE 14.23) respectively. Home range overlap was extensive, although contact between groups was rare, with >97.30% of all observations within 20 min separated by >250 m. The data strongly suggest that kipunji are not territorial.     

Movement patterns and herd dynamics among South African giraffes (Giraffa camelopardalis giraffa)

Giraffes reside in a fission–fusion social system, with sex, age proximity, kinship and home range overlap accounting for some of the variance in herd composition, while season, sex, age and time of day influence diet, home range size and distance travelled. To increase our knowledge of habitat use and fission–fusion herd dynamics, we placed GPS devices on eight adult female South African giraffes (Giraffa camelopardalis giraffa) living in the Khamab Kalahari Nature Reserve (South Africa). We tested four predictions about how season, kinship, home range and travel patterns influence habitat use and herd dynamics. Our two key findings were that females with a greater degree of home range overlap were more likely to form herds, but the degree of overlap was independent of the amount of time that they spent together in a herd, and that on the day prior to herd formation, females travelled about twice as far as their daily average and tended to move directly towards their future herd mate. We conclude that habitat use and movement patterns regulating fission–fusion dynamics reflect an interaction of ecological, social and reproductive factors operating in tandem, not independently.     

Increased isolation of two Biosphere Reserves and surrounding protected areas (WAP ecological complex, West Africa)

Protected areas such as nature reserves have been found to be effective in preventing habitat destruction and protecting ecosystems within their borders. Recent studies however found extensive loss of tropical forest habitat around protected areas, vastly contributing to increase the levels of ecological isolation. Using high-resolution satellite data we investigated the isolation trend occurring in the W-Arly-Pendjari (WAP) ecological complex in West Africa. A land-cover change analysis was performed for the period 1984–2002: savanna vegetation extension and loss were derived within the complex and in a 30 km peripheral buffer. Sample regions in the buffer were also analysed using selected spatial indicators to quantify temporal trends in habitat fragmentation. Implications for change in relative capacity to conserve biodiversity were discussed through the calculation of the species richness capacity (SRC). More than 14.5% of savanna habitat was lost in the WAP peripheral areas, while 0.3% was converted inside the complex. The degree of fragmentation of remnant savanna habitat has also drastically increased. Despite the effectiveness of the park conservation programme, we found through the SRC approach that the WAP complex is decreasing its potential capacity to conserve species richness. This process is mainly due to the rapid and extended agricultural expansion taking place around the complex. A better understanding of the ecological dynamics occurring in the peripheral regions of reserves and the consideration of development needs are key variables to achieve conservation goals in protected areas.     

Responses of 'resistant' vertebrates to habitat loss and fragmentation: the importance of niche breadth and range boundaries

Abstract. An ability to predict species' sensitivities to habitat loss and fragmentation has important conservation implications, and numerous hypotheses have been proposed to explain interspecific differences observed in human-dominated landscapes. We used occupancy data collected on 32 species of vertebrates (16 mammals and 16 amphibians) in an agricultural landscape of Indiana, USA, to compare hypotheses that focus on different causal mechanisms underlying interspecific variation in responses to habitat alteration: (1) body size; (2) morphology and development; (3) behaviour; (4) niche breadth; (5) proximity to range boundary; and multiple-process models combining main effects and interactions of hypotheses (1)–(2) and (4)–(5). The majority of habitat alteration occurred over a century ago and coincided with extinction of several species; thus, our study dealt only with variation in responses of extant species that often are considered 'resistant' to human modifications of native habitat. Corrected Akaike scores and Akaike weights provided strongest support for models incorporating niche breadth and proximity to range boundary. Measures of dietary and habitat breadth obtained from the literature were negatively correlated with sensitivity to habitat alteration. Additionally, greater sensitivity was observed for species occurring at the periphery of their geographical ranges, especially at northern or western margins. Body size, morphological, developmental and behavioural traits were inferior predictors of tolerance to fragmentation for the species and landscape we examined. Our findings reinforce the importance of niche breadth as a predictor of species' responses to habitat alteration. They also highlight the importance of viewing the effects of habitat loss and fragmentation in a landscape within a biogeographical context that considers a species' level of adaptation to local environmental conditions.     

Spatial ecology and habitat use of giraffe (Giraffa camelopardalis) in South Africa

The lack of long-term studies remains a limiting factor in understanding the home range, spatial ecology and movement of giraffes. We equipped eight giraffes with GPS satellite units and VHF capacity, which were built in to the collars for the remote collection of data on their movements and home ranges over two years on Khamab Kalahari Nature Reserve (KKNR) within the Kalahari region of South Africa. Giraffe numbers in KKNR dropped from 135 individuals to 111 in just five years, revealing the lack of knowledge about their required habitat needs, space use and diet. With over 1000 km² available for roaming within the reserve, habitat selection, principle and preferred food species played a significant role in home range size and overlap between individuals. These giraffes used an average annual home range of 206 km² (20 602 ha) as calculated by a 95% minimum convex polygon (MCP) with a standard deviation core home range calculated by a 50% MCP of 10.1 km² to satisfy their annual needs for survival and reproduction in their preferred vegetation. In the wet, hot season (summer: December–February) when food was abundant, giraffes frequented smaller areas (average 177 km²), while in the dry, cool season (winter: June to August) the mean home range size increased to approximately 245 km². Rainfall influenced spatial distribution since it determined vegetation productivity and leaf phenology. The different seasons influenced giraffe movements, while different vegetation types and season influenced their home range size. Season and food availability also influenced home range overlap between different giraffe herds. Home range overlap occurred when giraffes were forced to roam in overlapping areas during the dryer months when the winter deciduous nature of the majority of the tree species resulted in lower food availability. In winter, the overlap was approximately 31% and in autumn approximately 23%. During the wet and warmer months, overlapping was 15% in summer and 19% in spring, respectively. The percentage of time spent in different vegetation type areas was influenced by the abundance of the principal food species of that plant community. It is thus concluded that the movements of giraffes were primarily influenced by a combination of environmental factors such as season, rainfall and vegetation density.     

Navigating north: how body mass and winds shape avian flight behaviours across a North American migratory flyway

The migratory patterns of birds have been the focus of ecologists for millennia. What behavioural traits underlie these remarkably consistent movements? Addressing this question is central to advancing our understanding of migratory flight strategies and requires the integration of information across levels of biological organisation, e.g. species to communities. Here, we combine species‐specific observations from the eBird citizen‐science database with observations aggregated from weather surveillance radars during spring migration in central North America. Our results confirm a core prediction of migration theory at an unprecedented national scale: body mass predicts variation in flight strategies across latitudes, with larger‐bodied species flying faster and compensating more for wind drift. We also find evidence that migrants travelling northward earlier in the spring increasingly compensate for wind drift at higher latitudes. This integration of information across biological scales provides new insight into patterns and determinants of broad‐scale flight strategies of migratory birds.     

Importance of matrix permeability and quantity of core habitat for persistence of a threatened saltmarsh bird

Species habitat preferences can be obscured when individuals have been recorded in non‐core habitats because of dispersal, spillover effects or spatial errors in observation locations. Disentangling the direct effects of the habitats species are observed in from the effects of proximity to other nearby habitats is especially challenging in fragmented landscapes, as many fragmentation metrics are correlated and it is difficult to prove independent effects. In this paper we addressed this issue by comparing a number of models based on predefined ecological theories. We compared models based on quantity of core habitat surrounding observations, proximity to core habitat, or a combination of the two to explain the observed distribution of the saltmarsh inhabiting white‐fronted chat (Epthianura albifrons) in coastal New South Wales, Australia. Proximity to core habitat was considered as either Euclidean distance or cost distance, and models were assessed using Akaike's information criterion and the area under the receiver operator characteristic curve on 10 random subsets of the data. We found that all models performed similarly, with the combination of cost distance and the quantity of saltmarsh performing better, but not significantly so. We compared the advantages and disadvantages of different models and also present a model averaged result. Our models suggested that the majority of saltmarshes in New South Wales were too small to have a large effect on probability of occurrence. As climate change is expected to further reduce the amount of available saltmarsh through continued mangrove incursion, coastal populations of the white‐fronted chat are expected to come under increasing threat. The conversion of grasslands to urban areas may also increase the effective distance between different populations of the species and reduce gene flow and rescue effects.