Trap Stations Research Articles

Particulate organic carbon fluxes to the ocean interior and factors controlling the biological pump: A synthesis of global sediment trap programs since 1983

Particulate organic carbon (POC) is vertically transported to the oceanic interior by aggregates and their ballasts, mainly CaCO 3 and biogenic opal, with a smaller role for lithogenic aerosols through the mesopelagic zone. Diel migrating zooplankton communities effect vertical transport and remineralization of POC in the upper layers of the ocean. Below 1.5 km, the presence of zooplankton is reduced and thus the aggregates travel mainly by gravitational transport. We normalized the fluxes of POC, CaCO 3, and biogenic opal from data published on samples collected at 134 globally distributed, bottom-tethered, time-series sediment trap (TS-trap) stations to annual mole fluxes at the mesopelagic/bathypelagic boundary (m/b) at 2 km and defined them as F m/bC org, F m/bC inorg, and F m/bSi bio. Using this global data set, we investigated (1) the geographic contrasts of POC export at m/b and (2) the supply rate of ∑CO 2 to the world mesopelagic water column. F m/bC org varies from 25 (Pacific Warm Pool) to 605 (divergent Arabian Sea) mmolC m −2 yr −1; F m/bC inorg varies from >8 (high latitude Polar Oceans) or 15 (Pacific Warm Pool) to 459 (divergent Arabian Sea) mmolC m −2 yr −1; and F m/bSi bio, the most spatially/temporally variable flux, ranges from 6 (North Atlantic Drift) to 1118 (Pacific Subarctic Gyre) mmolSi m −2 yr −1. The oceanic region exhibiting the highest POC flux over a significantly large region is the area of the North Pacific Boreal Gyres where the average F m/bC org = 213, F m/bC inorg = 126, and F m/bSi bio = 578 mmol m −2 yr −1. F m/bC org and F m/bC inorg are particularly high in large upwelling margins, including the divergent Arabian Sea and off Cape Verde. One of the data sets showing the lowest flux over a significant region/basin is F m/bC org = 39, F m/bC inorg = 69, and F m/bSi bio = 22 mmol m −2 yr −1 in the North Pacific subtropical/tropical gyres; Pan-Atlantic average fluxes are similar except F m/bSi bio fluxes are even lower. Where C org/C inorg and Si bio/C inorg are <1 defines the “Carbonate Ocean”, and where these ratios are ⩾1 defines the “Silica Ocean”. The Carbonate Ocean occupies about 80% of the present world pelagic ocean between the two major oceanographic fronts, the North Pacific Polar Front and the Antarctic Polar Front, and the Silica Ocean is found on the polar sides of these fronts. The total global annual fluxes of F m/bC org, F m/bC inorg, and F m/bSi bio at m/b calculated by parameterizations of the export flux data from 134 stations are surprisingly similar; 36.2, 33.8, and 34.6 teramol yr −1 (120, 112, and 114 mmol m −2 yr −1), respectively, resulting in a near uniform binary ratio between the above three elements of about one. The global ternary % ratios estimated from 152 TS-trap samples of the three elements are 35:32:33. From our global F m/bC org and a published model estimate of the global export production, we estimate the regeneration rate of CO 2 through the mesopelagic zone by the biological pump is 441 teramolC yr −1. Based on our global F m/bC inorg and recently estimated global primary production of PIC, 36–86 teramolC yr −1 of PIC is assumed to be dissolved within the upper 2 km of the water column.

Do animals select habitat at small or large scales? An experiment with meadow voles (Microtus pennsylvanicus)

Habitat and patch use are crucial to the dynamics of populations and the structure of ecological communities. But ecologists have not rigorously tested whether animals choose habitat at small or large scales. If individuals base their patch and habitat choices on fine-scale differences in habitat, then their use of different sites should correspond with measures of microhabitat at those sites. But if individuals use density to assess and respond to habitat at larger spatial scales, then site use should correspond with the scale of density-dependent habitat selection. We tested these predictions with experiments that measured microhabitat and monitored the use of capture sites by meadow voles ( Microtus pennsylvanicus Ord, 1815) in 0.25 ha old-field enclosures. We varied the density of voles in pairs of adjacent enclosures and tested for density-dependent habitat selection. Then we assessed whether their frequency of captures at trapping stations was best predicted at the small scale of microhabitat or at the much larger scale of enclosures where density varied. The voles selected habitat at different scales. When the use of enclosures was predicted by density, the scale of density-dependent choice trumped the use of small-scale patches. And when voles selected amongst different small-scale patches, their use of enclosures was independent of density. These results suggest that assessments of spatial scale in habitat use must include tests for both scale- and density-dependent habitat choice.

Fine‐scale microhabitat selection for dense vegetation in a heathland rodent, Rattus lutreolus: Insights from intraspecific and temporal patterns

Abstract Vegetation is a dynamic habitat component and successional changes in vegetation structure can lead to concomitant changes in the communities of animals living in a particular area. Heathland rodents are a classic example, with vegetation at different ages post fire being dominated by different species. While broad associations are often demonstrated between the distribution and abundance of species and vegetation structure, the causal relationships are poorly understood. Studies of temporal and sex‐ or age‐specific patterns can provide strong insights into the processes underling patterns of habitat selection. In an attempt to better understand the mechanistic links between rodent successional patterns and vegetation structure in heathlands, we conducted a detailed study of microhabitat use by the swamp rat, Rattus lutreolus, in a native heathland in south‐eastern Australia. Rattus lutreolus typically occurs in late‐succession heath and is frequently associated with high vegetation density. Our assessment of vegetation at trapping stations, and also along trails used by the animals (using the spool‐and‐line tracking technique), revealed strong selection by the rats for dense vegetation by both day and night. The spool‐and‐line tracking approach revealed distinct intraspecific and temporal patterns. During the day, females foraged in vegetation of much higher density than did juveniles, with males behaving intermediately. During the night, however, all animals selected dense vegetation irrespective of sex or age, although the mean density of vegetation selected during the night was lower than it was during the day. These patterns were independent of daily maximum and minimum air temperature and were therefore unlikely to be related to microclimate. We propose instead that high vegetation density acts as a source of protection from predators, allowing R. lutreolus to forage safely both by day and by night.

Seaport as a source of hantavirus: A study on isolated isles

Since small mammals from seaports have relative higher seroprevalences of hantavirus, this seroepidemiologic study was conducted on the isles in Kinmen and Lienchiang Counties along the coast of southern mainland China to determine whether seaport may play the role as a source of hantavirus. Among six species of small mammals trapped in Kinmen County, only male Mus musculus (6.7%) and Rattus losea (5.3%) were found to be positive. In Lienchiang County, five species of small mammals were trapped and positive findings were obtained only in male R. norvegicus (9.3%), male M. musculus (7.7%), and female R. losea (1.6%). There was no significant difference in the seroprevalence between the two counties (Kinmen 3.8% vs. Lienchiang 3.9%). The positive rate in Liaolo (17.9%) of Kinmen County was significantly higher than the remaining trapping stations and those in Matsu Distillery (10.3%) and Fushing (5.8%) of Lienchiang County were significantly higher than the remaining ones. Moreover, a significant inverse correlation was found between the seropositive rate and the distance of small mammal sampling sites to the seaport (p < 0.01). These findings suggest the role of seaport as a source of hantavirus.

How effective are grid trapping, oil cards and track boards in monitoring bush rat populations?

Monitoring populations is a key component of wildlife conservation and management. This study aimed to evaluate the effectiveness of abundance indices used for estimating populations of the bush rat Rattus fuscipes. The study was conducted on Fraser Island, Queensland, Australia. A trapping grid consisting of 5 x 5 trap stations, 20 m apart, was used because this configuration was typical of those used for small mammal trapping in Australia. Capture-recapture data were collected from trapping 18 grids over four consecutive nights, immediately followed by two consecutive nights of conducting oil card and track indices. On 11 grids, model Mb was selected by the CAPTURE model selection procedure, indicating increased capture probability after first capture (trap-happy). The estimated trappable population size (�) on these grids was not precise with the standard error on average being 28% of �. On the other seven grids, the number of animals caught was too small (&lt;3) to estimate model parameters.. The main problem of the grid trapping was that some grids caught too few animals to estimate �. Our data suggest that the minimum grid area for estimating useful � is one that would catch more than 8 individuals. The minimum grid area varies depending on the density of rats and should be determined by a pilot trapping study. The number of trapping occasions can be increased until a specific precision of � is reached. The correlation between track index and � was near the 0.05 significance level indicating tracks are potentially a reliable index for monitoring bush rat populations. The oil card index was not significantly correlated with �.

Description de la femelle dePhlebotomus (Larroussius) chadliiRioux, Juminer et Gibily, 1966 (Diptera : Psychodidae). D’après un exemplaire capturé aux environs du Kef (Tunisie)

The female of Phlebotomus chadlii Rioux, Jumminer & Gibily, 1966 is described and illustrated for the first time from a specimen collected in El Kef region, northwest Tunisia. It was distinguished from P. ariasi by several characters of the spermathecae: 1) the enlarged portion of P. chadlii spermathecae duct appears smooth and better developed than that of P. ariasi; 2) in P. chadlii, this part comprises three quarters of the duct whereas, in P. ariasi, it covers only the half; 3) the spermathecae neck of P. chadlii is shorter than that of P. ariasi. The duct base is compatible with the large aedeagus size of P. chadlii male. Besides, the assignment of this female to the species P. chadlii is supported by: 1) the presence of males in the same area, over the last three years; 2) the total absence in this area of P. ariasi; 3) the concomitant presence, in the same trap station, of the described female with P. chadlii males.

Interactions among prescribed fire, herbivore pressure and shortleaf pine ( Pinus echinata) regeneration following southern pine beetle ( Dendroctonus frontalis) mortality

We monitored natural and artificially regenerating shortleaf pine ( Pinus echinata) seedlings and their associated herbivores in forests stands that suffered extensive overstory mortality due to the southern pine beetle ( Dendroctonus frontalis). Seedling performance was evaluated based on survival and absolute and relative growth rates. Trapping stations were established to monitor the abundance and seasonal activity of pine regeneration insects. Seedlings were regularly inspected for the frequency and severity of herbivore pressure. Seedling performance, insect abundance and activity, and herbivore pressure were compared between stands treated with prescribed fire and untreated controls. Survival and absolute growth rates were greatest for naturally regenerating seedlings. Naturally regenerating seedlings grew more vigorously in the burned areas, but prescribed fire did not influence the growth of planted seedlings. Relative height growth comparisons indicated the growth potential of planted seedlings was not significantly different from that of the natural seedlings. Herbivore pressure was greater on natural regeneration, possibly due to superior seedling health and vigor. Pine weevil ( Hylobius pales and Pissodes nemorensis) and Nantucket pine tip moth ( Rhyacionia frustrana) abundance and herbivore pressure did not differ between the burned and unburned stands, but there was a significant interaction between sampling date and prescribed fire on their seasonal activity. Conifer sawfly (Hymenoptera: Diprionidae) abundance and activity was effectively suppressed by prescribed fire treatments. Pine webworm ( Tetralopha robustella) infestations occurred with greater frequency and severity on seedlings growing in burned areas. Mammalian herbivory was minimal. Herbivore-induced seedling mortality was low, and herbivory did not reduce seedling growth. Growth of naturally regenerating shortleaf pine seedlings was greater in burned plots.

HABITAT ASSOCIATIONS OF SMALL MAMMALS AT TWO SPATIAL SCALES IN THE NORTHERN SIERRA NEVADA

Effective management strategies require an understanding of the spatial scale at which fauna use their habitat. Toward this end, we sampled small mammals in the northern Sierra Nevada, California, over 2 years at 18 livetrapping grids among 5 forest types. Forest types were defined by overstory tree composition, and 19 microhabitat variables were measured at all trap stations. Forest type and year explained 93% of variation in abundance of North American deermice (Peromyscus maniculatus), whereas only 40% was explained by microhabitat and year. Similarly, variation in abundance of long-eared and shadow chipmunks (Neotamias quadrimaculatus and N. senex) was better explained by forest type and year (67%) than by microhabitat and year (30%). Red fir (Abies magnifica) forests supported more P. maniculatus and Neotamias species than mixedconifer and pine‐cedar forests, and more Neotamias species than mixed-fir forests. Five of 6 uncommon species were significantly associated with forest type; golden-mantled ground squirrels (Spermophilus lateralis), northern flying squirrels (Glaucomys sabrinus), and long-tailed and montane voles (Microtus longicaudus and M. montanus) were captured almost exclusively in red fir forests, whereas dusky-footed woodrats (Neotoma fuscipes) and California ground squirrels (Spermophilus beecheyi) were found in pine‐cedar, mixed-fir, and mixed-conifer forests. The first 2 axes of a canonical correspondence analysis on microhabitat variables explained 71% of variation in combined small mammal abundance. Microhabitat associations varied among species but were driven primarily by canopy openness, shrub cover, and shrub richness. Although much of the small mammal fauna appeared to select habitat at both spatial scales studied, canonical correspondence analysis using forest type as a covariate revealed that microhabitat explained much less variation in small mammal abundance than did forest type.

Characteristics of alkenone distributions in suspended and sinking particles in the northwestern North Pacific

We investigated alkenones recorded in suspended particles and a settling particle time series collected at three stations, 40N (40°N, 165°E), KNOT (44°N, 155°E), and 50N (50°N, 165°E), in the northwestern North Pacific from December 1997 to May 1999. Emiliania huxleyi, the most abundant alkenone producer in this area, is present in surface to subsurface (to ∼50 m depth) waters. The alkenone concentrations recorded in the suspended particles indicated that the seasonal alkenone particle distribution differed significantly interannually. Alkenone export fluxes at the three sediment-trap stations ranged from 0.16 to 49.3 μg m −2 day −1, and the maximum export flux, which occurred in summer to fall (July–November), was associated with a high organic carbon export flux. The amount of alkenone produced during the maximum export season accounted for 60–80% of the total annual amount of alkenone, and the alkenones accumulated in the sediment below the traps had characteristics corresponding to subsurface waters during the summer–autumn season. Alkenone-derived temperatures recorded in suspended particles corresponded to the in situ temperature within ∼2 °C. Although alkenone-derived temperatures corresponded approximately to the temperatures observed in the stratified subsurface waters at the three trap stations during the high-export season, large differences were observed during the low-export (winter–spring) period. For example, the alkenone-derived temperatures observed at stations KNOT and 50N were much higher than the in situ subsurface temperatures reported in the World Ocean Atlas 2001. Relatively large differences between alkenone-derived temperatures and in situ temperatures in the subarctic might be due to (1) a low-light limitation or (2) contributions of allochthonous alkenones in particulate material transported from subtropical areas within a warm-core ring.

Spatial heterogeneity in predator activity, nest survivorship, and nest-site selection in two forest thrushes

The ability of prey to find and use predator-free space has far-reaching consequences for their persistence and interactions with their predators. We tested whether nest survivorship of the ground-nesting veery (Catharus fuscescens) and shrub-nesting wood thrush (Hylocichla mustelina) was related to the local absence of a major nest predator, the white-footed mouse (Peromyscus leucopus). Mouse-free space was defined by trap stations that failed to trap a mouse during the avian breeding season (approximately May through July). In addition, mouse activity was quantified at individual trap stations based on the number of captures during the same period (six 2.25-ha trapping grids, each containing 121 trap stations trapped repeatedly throughout the summer between 1998 and 2002.) Annual mouse-free space was correlated with other measures of mouse activity based on trapping data. Both mouse-free space and activity metrics were significantly related to annual rates of nest predation (i.e., nest daily mortality rate) in veery but not wood thrush. Likewise, mouse-free space and mouse activity within the nest neighborhood (approximately 30x30 m2 surrounding each nest) was significantly related to nest survivorship in veery but not wood thrush. More trap stations had consistently greater (hotspots) and lesser (coldspots) mouse activity than expected by chance, and veeries were significantly more likely to nest near stations that had below the grid-average trapping success. Our study thus documented significant spatial variability in predator activity and its relationship to nest predation and nest-site selection in a ground-nesting songbird.

Habitat utilisation by small mammals in a coastal heathland exhibiting symptoms of Phytophthora cinnamomi infestation

Phytophthora cinnamomi is a soil-inhabiting ‘water mould’ that is pathogenic to many native plant species in Australia, and has been shown to alter plant species abundance and richness, as well as the structure of vegetation in sclerophyllous vegetation. This study investigated the effects of P. cinnamomi-induced vegetation disturbance and habitat degradation on microhabitat associations of small mammals in a coastal heathland in southern Australia. Seven small mammal species were trapped in a P. cinnamomi-infested heathland community over four years. Trap stations were classified into three disease classes (non-diseased, active disease and post-disease) and structural and floristic aspects of the vegetation were recorded at each station. The mean number of species captured was greatest in non-diseased areas and least in post-disease areas. The total capture frequency of small mammals was lower in post-disease areas except where they were covered by thick stands of tall tea-tree (Leptospermum sp.). Combined small mammal captures were associated with thick vegetation and floristic factors. Captures of Antechinus agilis, Rattus fuscipes, Rattus lutreolus and Sminthopsis leucopus were greatest in non-diseased vegetation and were less frequent in areas of diseased vegetation. A. agilis and R. fuscipes captures were correlated with a floristic factor associated with non-diseased vegetation, while R. lutreolus was associated with structural factors, preferring thick vegetation. The impact on Cercartetus nanus and Isoodon obesulus could not be assessed owing to low captures of these species. Modification of vegetation structure and floristics associated with P. cinnamomi infestation is having a significant impact on the habitat utilised by the small mammal communities in the area. This impact highlights the need to identify and protect those areas that remain free of P. cinnamomi infestation. Continued spread of the pathogen will reduce the area of suitable small-mammal habitat able to support the diverse communities of the eastern Otway Ranges, Victoria, Australia.

Floristic and structural components of habitat use by the eastern pygmy-possum (Cercartetus nanus) in burnt and unburnt habitats

The eastern pygmy-possum (Cercartetus nanus) occurs broadly but patchily in south-eastern Australia. It is a small, difficult-to-trap marsupial with poorly known resource and habitat preferences. This study investigated the structural and floristic habitat resources used and selected by C. nanus in Royal National Park (which was heavily burnt by bushfire in 1994) and Heathcote National Park (most of which had remained unburnt for over two decades at the time of study), in central-coastal New South Wales. Three different sampling methods were used – pitfall traps, Elliott traps and hair tubes – with pitfall trapping being by far the most effective method for detecting C. nanus. Live-trapping in different habitats revealed higher numbers of C. nanus in unburnt and burnt woodland, burnt heathland and burnt coastal complex than in unburnt coastal complex and burnt and unburnt rainforest. To identify the components of habitat contributing to this pattern, we first scored floristic and structural features of vegetation around trap stations and then quantified habitat components further by using spool- and radio-tracking. We found little evidence that C. nanus responded to any structural components of habitat, although arboreal activity was greater, not surprisingly, in wooded than in burnt heathland habitats. C. nanus was associated most strongly with the abundance of certain plants in the Proteaceae and Myrtaceae. In particular, the species prefers Banksia spp. (probably for food) and Eucalyptus and Xanthorrhoea spp. (probably for shelter).

Effects of trapping with bait on bait-station indices to black bear abundance

Indices of relative abundance allow managers and researchers to examine changes in population size over time or compare relative population sizes in different areas. In the Pisgah Bear Sanctuary, bait-station surveys were conducted in most years from 1983 to 2000 to follow trends over time in the black bear (Ursus americanus) population. Baited bear trapping also took place in the sanctuary during those years, and some trap lines coincided with bait-station lines. Because the same baits were used for both trapping and bait station lines, we hypothesized that visitation rates of bears to bait stations established in proximity to baited trap lines would differ from rates at bait stations that were not associated with baited trap lines. We modeled probability of bait stations being visited by bears on trapped and untrapped lines to estimate the effect baited trapping had on visitation rates. We found that population trends inferred from bait-station visits in areas that also were trapped with bait were biased high and that bias increased over time. Bears may have become habituated to the bait on trap lines and incorporated it as a regular food source. Bait-station indices should not be conducted near research sites that employ similar bait when both produce a tangible reward for the animals.

Turbulent mixing and mesoscale distributions of late‐stage fish larvae on the NW Shelf of Western Australia

AbstractLight traps were deployed to describe vertical and cross‐shelf distributions of late‐stage larval fishes during five cruises in each of the 1997/98 and 1998/99 summers in the region of the Gulf of Exmouth on the southern North West Shelf of Western Australia. At each light trap station on a cross‐shelf transect we measured water temperature, salinity and chlorophyll a and used vertical plankton tows to estimate zooplankton biomass and copepod abundance. Current meters were deployed on moorings near the transect and the data used to model flows and mixing on the NW Shelf and in the Gulf. The majority of reef, pelagic and baitfish larvae (81, 83 and 66% respectively) were collected at only two stations that marked the boundary between stratified waters offshore and well‐mixed water within the Gulf. Most baitfishes (primarily Spratelloides spp.) were captured by traps deployed near the seabed, while reef fishes (mostly pomacentrids, lethrinids and siganids) and pelagic species (mostly scombrids and carangids) were captured in traps deployed near surface. Catch composition varied between summers with 64% of baitfishes collected in the first summer, while the majority of reef and pelagic fishes (81 and 80% respectively) were captured in the second summer. Modelling of circulation showed that the velocity of tidal currents was enhanced by constriction of flow between NW Cape and South Muiron Island and by shallowing of the shelf. Flood‐tide intrusions of water allowed the thermocline to move up the continental shelf, upwelling cool nutrient‐rich water that was then mixed throughout the entire water column at stations in the mouth of the Gulf. This upwelling and mixing resulted in higher chlorophyll a concentrations and copepod abundances either as a result of local in situ growth or advection/aggregation processes, and may account for the great abundances of late‐stage fish larvae in the mouth of the Gulf.

VARIATION IN SMALL MAMMAL SPECIES RICHNESS BY TRAP HEIGHT AND TRAP TYPE IN SOUTHEASTERN AMAZONIA

Abstract Despite its biological richness, the rodent and marsupial fauna of many parts of the Amazon Basin remains poorly known and the efficacy of different methods in assessing its diversity are poorly understood. We present results of small mammal trapping at a previously unsurveyed site in the Xingu Basin of the southeastern Amazon, Para, Brazil; provide details on a new method for arboreal trapping; and compare species richness among traps at different heights and between different trap types. Mammals were livetrapped at 3 trap heights: ground, understory (1–3 m above ground), and canopy (mean height = 11.5 m ± 3.2 SD, range = 4.8–16.8 m, n = 76 trap stations). We recorded 1,769 captures of 1,178 individuals of 8 marsupial and 17 rodent species in 38,090 trap-nights (or 19,320 station-nights, where a station-night consisted of 1 Sherman and 1 Tomahawk live trap at 1 height for 1 night). Overall trap success was 6.1 individuals per 100 station-nights; success by trap position was 9.0% for ground (7,85...

Patterns of habitat utilization of small rodents in an area of Araucaria forest in Southern Brazil

Abstract We investigated patterns of spatial distribution and microhabitat selection of rodents in a patch (26 ha) of mixed ombrophilous forest (or Araucaria forest), dominated by the Araucaria ‘pine’Araucaria angustifolia, in the National Park of Aparados da Serra, RS, in southern Brazil. We conducted monthly trapping sessions lasting 6 days (from June 2000 to June 2001) using a square grid of 121 trap stations, separated by 15 m (2.25 ha). We measured 10 microhabitat variables that could influence species distribution. These variables were related to the occurrence of mammals by using canonical correspondence analysis (CCA) and stepwise multiple regression. The distribution patterns of the three most common rodents differed significantly (χ2 = 38.6; P &lt; 0.002), with Delomys dorsalis being more clumped than the other two species. Both CCA and multiple regression analysis showed a significant effect of microhabitat variables on species occurrence. The multiple regression parameters for Oligoryzomys nigripes were R2 = 0.142, P &lt; 0.05, for Akodon montensis were R2 = 0.222, P &lt; 0.01, and for D. dorsalis R2 = 0.323, P &lt; 0.001. Variables that significantly influenced species distribution were vegetation density at 1 m height and length of fallen logs for O. nigripes, canopy cover for A. montensis, and vegetation density at 2 m height, quantity of leaves of Araucaria trees (negative relationship), tree density (except Araucaria trees), and number of potential shelters, for D. dorsalis. The results indicated that D. dorsalis is the most habitat specialist among the rodent species and that there are no apparent competitive interactions.

Scale-dependent habitat selection in three didelphid marsupials using the spool-and-line technique in the Atlantic forest of Brazil

Habitat selection can be detected at different scales. For small mammals, habitat studies normally evaluate micro- or meso-habitat selection, but rarely are multiple scales analysed simultaneously. These studies use quantitative data of structural characteristics around the trap stations to evaluate selection. We test an alternative method to evaluate habitat selection in three didelphid marsupials (Didelphis aurita, Philander frenatus and Metachirus nudicaudatus), using a spool-and-line device, and measure habitat selection at two spatial scales. Habitat was characterized by seven habitat variables measured at ten points of direction change along the path traversed by each individual, and at 25 trap stations distributed in a 1-ha area. Micro-habitat selection was estimated at each point by comparing habitat measures between the direction selected against other directions. Meso-habitat selection was estimated by comparing habitat measurements on the whole path of an individual against habitat measures on the 25 trap stations. Patterns of selection for each species could only be detected at the meso-habitat scale, although a few individuals in each species were selective at the micro-habitat scale. Studies of habitat selection need to address the scale of study quantitatively, if possible comparing two or more scales to determine the scale of selection.

The home range of ship rats (Rattus rattus) in beech forest in the Eglinton Valley, Fiordland, New Zealand: A pilot study

Three male and two female ship rats (Rattus rattus) were radio‐tagged and tracked in beech (Nothofagus) forest in the Eglinton Valley, Fiordland, New Zealand over two field periods in 1996 and 2000. The home range of each animal was calculated using the minimum convex polygon method. Ranges of three male rats were 7.5, 9.1, and 11.4 ha whereas those of the female rats were 0.89 and 0.27 ha. The home ranges recorded for male rats were considerably larger than those reported from other studies in non‐beech forest. Ship rats are important predators of forest birds, and home range information could be used to provide a guide for trap or bait station spacing in beech forests. To carry out rat control in beech forests effectively, further studies are needed to determine if the results of this pilot study are typical, and if home ranges of ship rats change with season, or at various stages of the beech mast cycle.

Effects of mahogany ( Swietenia macrophylla) logging on small mammal communities, habitat structure, and seed predation in the southeastern Amazon Basin

Vast areas of the Amazon have been subjected to low-intensity selective logging for high value timber species such as mahogany ( Swietenia macrophylla). Although the ecological consequences of such logging are often assumed to be minimal, few studies have directly tested this assumption. In this paper we examine the effects of various intensities of mahogany logging on small mammal communities, habitat structure, and seed predation in the southeastern Amazon Basin. We sampled small mammal communities using live traps at two logged and two unlogged sites. Within each site, we established five 1 ha sampling grids that sampled the range of logging damage (in the case of logged sites) or mahogany densities (in the case of unlogged sites). Grids were sampled with 10 trap stations on the ground, 10 in the understory (at 1–3 m in height), and five in the canopy (at approximately 10 m in height) during three, 10-night trapping sessions over the course of the 10-month study. We measured a suite of forest structure and small mammal food resource (insect and fruit abundances) variables at each station and mahogany and peanut seed predation rates were measured at five locations per grid. We captured a total of 817 individuals of eight marsupial and 17 rodent species in 29,500 trap nights. Neither mahogany density across unlogged grids nor logging damage across logged grids were significantly correlated with variation in any of the measured habitat variables, seed predation rates, or measures of small mammal resource abundance. However, site-specific means for several variables (volume of downed wood, number of vines per tree, number of vines, number of herbaceous stems, and understory density) were higher in logged than unlogged sites, but significantly so in only two cases (number of vines per tree, volume of downed wood). When pooled, the logged grids had higher small mammal abundances and species richness than unlogged grids; however, predation of mahogany seeds and peanuts did not differ significantly between the two site types. When the two logged sites were analyzed separately, the effects of logging were found to be very different at the two sites. One of the logged sites showed few effects of logging and had similar forest structure and small mammal communities to the unlogged sites, whereas the other logged site demonstrated effects consistent with previous reports on logging, including increased small mammal abundances, increased seed predation, and decreases in seedling and sapling densities as a function of increasing levels of logging damage. This study provides evidence that the ecological consequences of mahogany logging are strongly dependent on local site features; however, the overall effects of the logging appeared to be small, suggesting that areas that have been subjected to only low-levels of logging can still make valuable contributions to conservation.

Calcareous dinoflagellates from a northwestern Pacific sediment trap and their paleoceanographic implications

Research Article| January 01, 2004 Calcareous dinoflagellates from a northwestern Pacific sediment trap and their paleoceanographic implications Yoshihiro Tanimura; Yoshihiro Tanimura 1Department of Geology, National Science Museum, Tokyo 169-0073, Japan Search for other works by this author on: GSW Google Scholar Chieko Shimada Chieko Shimada 2Doctoral Program in Earth Evolution Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Japan email: tanimura@kahaku.go.jp Search for other works by this author on: GSW Google Scholar Micropaleontology (2004) 50 (4): 343–356. https://doi.org/10.2113/50.4.343 Article history received: 08 Jun 2004 accepted: 17 Nov 2004 first online: 06 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Yoshihiro Tanimura, Chieko Shimada; Calcareous dinoflagellates from a northwestern Pacific sediment trap and their paleoceanographic implications. Micropaleontology 2004;; 50 (4): 343–356. doi: https://doi.org/10.2113/50.4.343 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyMicropaleontology Search Advanced Search Abstract Year-round changes in species composition and flux of calcareous dinoflagellates at station JT (34°09.8′N, 141°59.3′E; water depth, 8942m; trap depth, 916m) are reported. A time-series of thirteen sediment-trap samples of 29 days each, between March 5, 1991 and March 2, 1992, provided materials for this study. Vegetative cysts of a calcareous dinoflagellate, Thoracosphaera heimii, were found to be overwhelmingly dominant forming >95% of the calcareous dinoflagellate associations in all trap samples. Its’ flux ranges from 910,000 shells·m−2·day−1 in May, 1991, to 76,000 shells·m−2·day−1 in September, 1991. Cysts of other calcareous dinoflagellates (Leonella granifera, Calciodinellum albatrosianum and Calciodinellum levantinum) were also found, with a maximum flux of 11,000 shells·m−2·day−1 for C. albatrosianum between December, 1991 and January, 1992. Based on physiological information, we suggest that species flux depends on water mass distribution linked to migration of the path of the subtropical Kuroshio Current. High to moderate flux of T. heimii occurred when the current took a meandering or a straight nearshore pathway. Waters southeast of the current prevailed over the trap station during this time. The most favorable environment, May, 1991, for T. heimii production seems to occur around a shallow thermocline formed above Subtropical Mode Water (STMW) in the waters southeast of the current. The species flux dropped when the current took an offshore pathway and flowed over the trap station. Surface and subsurface waters of the Kuroshio Current, especially during summer to autumn, is not productive of this species. The species flux also dropped while a “cold water mass” (i.e. lower salinity water cut off from the subarctic Oyashio Current) emerged over the trap station. Three cysts, L. granifera, C. albatrosianum and C. levantinum, show broadly similar abundance fluctuations to T. heimii. This close relationship between temporal changes in T. heimii productivity and path migrations of the Kuroshio Current, which is linked to the wind stress field over the North Pacific, should potentially provide information for paleoclimatic reconstructions. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.