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1.
Stable-isotope analyses (δ13C, δ15N and δ34S) of multiple tissues (fin, muscle, red blood cells and plasma), revealed ontogenetic shifts in resource use by grey reef sharks Carcharhinus amblyrhynchos and resource partitioning with silvertip sharks Carcharhinus albimarginatus within the British Indian Ocean Territory marine protected area (MPA). Resource partitioning varied temporally, with C. albimarginatus feeding on more pelagic prey during October to January, potentially attributable to an influx of pelagic prey from outside the MPA at that time. Reef sharks may therefore be affected by processes outside an MPA, even if the sharks do not leave the MPA.  相似文献   
2.
Peter Finck 《Oecologia》1990,83(1):68-75
Summary In a population of Little Owls (Athene noctua) at the Lower Rhine (FRG), the factors were studied that influence the size and shape of territories of this non-migrating, all-year territorial owl species. These studies were carried out between September 1984 and June 1987. The birds were individually marked with transmitter packages so that their locomotional movements could be monitored. Using a standard protable stimulus (a dummy with an attached loudspeaker) the territorial boundaries of 19 male Little Owls were surveilled during the different seasons of the year. Male Little Owls defended their territories in all seasons, but distinct seasonal changes of intraspecific aggressiveness and territory size were observed. The seasonal variations of territory size followed a common pattern in all studied Little Owls, in spite of individual differences in the size of the defended areas. The largest territories were defended in March/April during the courtship season . In May/June all male Little Owls reduced the size of their territories . This corresponds to the breeding and nestling period. The yearly minimum of territory size was reached in the summer months July and August when the fledglings were still fed in the parental territory. When the first-year birds started to disperse in autumn (September/October), the size of the defended areas of the adult tenants again increased . In winter (November to February), a further increase in territory size was observed for periods of warm weather . Male Little Owls, however, were less aggressive during winter than in the following courtship season. On cold winter days with a ground cover of snow territorial aggressiveness ceased. Pastures and meadows offered a continuous food supply almost throughout the year. In some seasons they were overproportionally represented in the territories of Little Owls compared to the general surroundings. In reaction to changing accessibility of food, the hunting ranges within the home ranges were shifted much faster than the boundaries of the defended territories. The significance of various factors contributing to the variability of territory size in Little Owls are discussed (e.g. availability of food, seasonal and individual differences in aggressiveness, experience in the occupied area, population density).  相似文献   
3.
Synopsis Social organization and spawning in the sharpnose pufferCanthigaster rostrataere studied on a reef in the San Blas Islands, Panama. Sexes were dimorphic. In mixed coral and rubble habitat, females defended territories against other females and small males. From one to six female territories were included within the territories of certain large males. These haremic males visited their females and patrolled their territories throughout the day. Smaller, non-haremic males occupied territories or home ranges within or adjacent to those of haremic males or were wanderers. Spawning between a haremic male and a territorial female occurred within the female's territory. The female prepared an algal nest into which demersal eggs were deposited. There was no parental care. Eggs were spherical, translucent, and measured approximately 0.66 mm in diameter. Larvae were about 1.4 mm TL and closely resembled those of other species ofCanthigaster.  相似文献   
4.
We present a new 23‐site network of white spruce ring‐width chronologies near boreal treeline in Old Crow Flats, Yukon Territory, Canada. Most chronologies span the last 300 years and some reach the mid‐16th century. The chronologies exhibit coherent growth patterns before the 1930s. However, since the 1930s, they diverge in trend and exhibit one of two contrasting, but well‐replicated patterns we call Group 1 and Group 2. Over the instrumental period (1930–2007) Group 1 sites were inversely correlated with previous‐year July temperatures while Group 2 sites were positively correlated with growth‐year June temperatures. At the broader northwestern North America (NWNA) scale, we find that the Group 1 and Group 2 patterns are common to a number of white spruce chronologies, which we call NWNA 1 and NWNA 2 chronologies. The NWNA 1 and NWNA 2 chronologies also share a single coherent growth pattern prior to their divergence (ca. 1950s). Comparison of the NWNA 1/NWNA 2 chronologies against gridded 20th‐century temperatures for NWNA and reconstructed northern hemisphere summer temperatures (ad 1300–2000) indicates that all sites responded positively to temperature prior to the mid‐20th century (at least back to ad 1300), but that some changed to a negative response (NWNA 1) while others maintained a positive response (NWNA 2). The spatial extent of divergence implies a large‐scale forcing. As the divergence appears to be restricted to the 20th century, we suggest that the temperature response shift represents a moisture stress caused by an anomalously warm, dry 20th‐century climate in NWNA, as indicated by paleoclimatic records. However, because some sites do not diverge and are located within a few kilometres of divergent sites, we speculate that site‐level factors have been important in determining the susceptibility of sites to the large‐scale drivers of divergence.  相似文献   
5.
It is generally accepted that high quality males are those that succeed in male–male competition: in either aggression or rivalry to attract and be selected by females. Previous studies of amphibians have suggested that the main characters influencing male mating success include variation in call characteristics (e.g. call rate, call intensity), calling behaviour, body condition, age and chorus tenure. In the present paper, several of the characters influencing female mate choice (male body size, body condition, call rate, call frequency and chorus tenure) are investigated in two closely related, explosive breeding frog species Litoria chloris and Litoria xanthomera. Smaller males of both species are shown to be more successful than larger males and this success is attributed to the increased chorus tenure of smaller males in L. xanthomera. This increased chorus tenure was attributed to the lower total energy used per call by a small male calling at a higher frequency. Whether increased chorus tenure explains female mate choice in L. chloris is uncertain but is highly probable given the strong similarity between the two species in both ecology and call characteristics.  相似文献   
6.
(i) The steady-state kinetic data obtained with purified gizzard and uterus smooth muscle myosins indicated the presence of a plateau region on the substrate-saturation curves. Hill plots of these data provided evidence for mixed positive and negative cooperative interactions. In contrast, when gizzard myosin was prepared according to the method of A. Sobieszek and R.D. Bremel (1975, Eur. J. Biochem.55, 49–60), the saturation curve in the presence of CaATP was hyperbolic and no cooperativity of the binding site(s) was discerned. However, in the presence of MgATP although the curve appeared hyperbolic the Hill plot of the data was biphasic with negative cooperativity at low MgATP concentration, (ii) When thiophosphorylated gizzard myosin was used for kinetic analysis, the plateau region in the presence of MnATP was eliminated from the saturation curve and this curve became hyperbolic. However, in the presence of MgATP, although the plateau was almost eliminated, the saturation curve was still biphasic with either no or greatly reduced negative cooperativity of binding sites at low MgATP concentrations but positive cooperativity of binding at high MgATP concentrations. In addition, the thiophosphorylation of myosin also increased the Km and V of MgATP and MnATP, thus indicating weaker affinity for these substrates with thiophosphorylated myosin. (iii) Gizzard myosin also hydrolyzed other nucleotides (the order of rates being CTP = ITP > ATP = UTP > GTP), therefore saturation kinetics using different nucleotides as substrates was also carried out. The saturation curves with each nucleotide were different i.e., hyperbolic with CTP, sigmoid with GTP, hyperbolic with biphasic Hill plot with ITP, and possessing plateau with UTP. In addition, it was observed that the kinetic pattern with each nucleotide was very sensitive to temperature and pH.  相似文献   
7.
Marine conservation programs in Oceania are increasingly turning to precautionary and adaptive management, particularly approaches which emphasize local participation and customary management. Although the application of community-based natural resource management is widespread in the region, the full integration of local knowledge and practices into the design, implementation, and monitoring of community-based conservation programs has been limited. There is also little empirical data to show whether or not community-based conservation projects are meeting their stated objectives. This paper summarizes an integrated method for selecting Marine Protected Area (MPA) sites and presents empirical evidence that illustrates how an MPA that was largely conceived using indigenous ecological knowledge and existing sea tenure governance (i.e., customary management practices), as part of a regional precautionary and adaptive community-based management plan, is showing signs of biological and social success. More generally, the paper shows how hybrid natural and social research approaches in tandem with customary management for designing MPAs can protect coral reefs in Oceania.  相似文献   
8.
Saltwater crocodiles (Crocodylus porosus) in the Northern Territory of Australia were protected in 1971, after a severe population decline resulting from 26 yr of intense commercial hunting. By that time wild saltwater crocodiles were rarely sighted anywhere and they were commercially extinct in areas where they had once been abundant. Standardized monitoring by spotlight surveys started in 1975 and provided relative density indices over time (1975–2009) as a unique record of the post-protection recovery of a wild crocodilian population. We examined the survey data for populations at 12 major tidal rivers, individually and as a single subpopulation. The pattern of recovery in the subpopulation in both abundance and biomass was approximated by logistic curves, predicting 5.26 non-hatchling crocodiles weighing 387.64 kg sighted per kilometer of river in 2010. We predicted potential carrying capacity as 5.58 non-hatchling crocodiles (5.73% higher than 2010) weighing 519.0 kg (25.31% higher than 2010). Individual rivers showed largely different abundance and biomass among rivers. The statistical model that best described the recovery in individual rivers was not always logistic. However, where it was logistic, expected carrying capacity of different rivers showed considerable variation in abundance and biomass. The variation indicates different habitat quality among the rivers. Recovery occurred despite various consumptive uses, particularly a widespread egg-harvest program, which has been an integral part of the incentive-driven conservation program for saltwater crocodiles in the Northern Territory since 1983. We suggest that the saltwater crocodile population of the Northern Territory is achieving full recovery from uncontrolled hunting in 1945–1971. Although saltwater crocodiles are considered an important natural resource, their increase in number, size, and distribution is posing management issues for public safety. Continuation of human–crocodile conflict management through public education and strategic removal of problem crocodiles will be essential. © 2011 The Wildlife Society.  相似文献   
9.
We studied foraging site partitioning between the sexes in Neolamprologus tetracanthus, a shrimp-eating Tanganyikan cichlid with harem-polygyny. Females maintained small territories against heterospecific food competitors within large territories of males, foraging exclusively at the inner side of their own territories (foraging areas). Males fed as frequently as females in their own territories, but mostly outside female foraging areas, although they frequently entered female territories and repelled food competitors from the territories. Soon after removal of the resident females, however, harem males, as well as many food competitors, invaded the vacant territories and intensively devoured prey of female foraging areas. This indicates that although female foraging areas appear to contain more food than outside the areas, harem males refrained from foraging there when the resident females were present. We suggest that harem males will attempt to keep female foraging areas in good condition, whereby they may get females to reside in male territories and/or promote female gonadal maturation.  相似文献   
10.
Andean cultural ecologists have made two claims in recent years: ecological decomposition is absent due to effective indigenous management of communal resources, and agricultural intensification is inversely related to altitude. Drawing on material from the Jukumani Indians of Northern Potosi, Bolivia, these assertions are challenged. First, there is little evidence to prove or disprove ecological degradation. Second, the location of agricultural intensification, as the Jukumani data suggests, is influenced by altitude as well as by the presence of market.Fieldwork in Bolivia was carried out between January 1979 and May 1981. This essay was originally presented at a conference entitled, How Communities Resolve Common Property Problems, sponsored by the Harvard Institute for International Development and the Center for Population Studies of Harvard University in the spring semester of 1983.  相似文献   
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