Home About us Contact
|
Home About us Contact | ||
|
|
||
Habitat Attributes (habitat + attribute)
Selected AbstractsEffects of off-bottom shellfish aquaculture on winter habitat use by molluscivorous sea ducksAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2009ydelis Abstract 1.Shellfish farming is an expanding segment of marine aquaculture, but environmental effects of this industry are only beginning to be considered. 2.The interaction between off-bottom, suspended oyster farming and wintering sea ducks in coastal British Columbia was studied. Specifically, the habitat use of surf scoters (Melanitta perspicillata) and Barrow's goldeneyes (Bucephala islandica), the most abundant sea duck species in the study area, was evaluated in relation to natural environmental attributes and shellfish aquaculture. 3.The extent of shellfish farming was the best-supported habitat variable explaining variation in surf scoter densities, and the only habitat attribute from the considered set that was a strong predictor of Barrow's goldeneye densities. In both cases, the findings indicated strong positive relationships between densities of sea ducks and shellfish aquaculture operations. These relationships are presumably the result of large numbers of wild mussels (Mytilus trossulus) that settle and grow on aquaculture structures and are preferred prey of these sea ducks. 4.Previous work has shown that aquaculture structures provide good conditions for recruiting and growing mussels, including refuge from invertebrate predators, which in turn provides higher densities of higher quality prey for sea ducks than available in intertidal areas. This offers a rare example in which introduction of an industry leads to positive effects on wildlife populations, which is particularly important given persistent declines in numbers of many sea ducks. Copyright © 2008 John Wiley & Sons, Ltd. [source] Effects of cover reduction on mulgara Dasycercus cristicauda (Marsupialia: Dasyuridae), rodent and invertebrate populations in central Australia: Implications for land managementAUSTRAL ECOLOGY, Issue 6 2003PIP MASTERS Abstract This study investigates the effect of cover reduction on the mulgara, Dasycercus cristicauda, a small marsupial classified as vulnerable to extinction, which occurs in areas of central Australia dominated by hummock grasslands. Loss or degradation of spinifex has been implicated in population declines of this species previously, but the importance of cover in maintaining quality habitat remains speculative. To determine the effect on D. cristicauda of cover reduction, caused by the harvesting of spinifex, we monitored population changes and changes in prey resources (rodents and invertebrates) before and after spinifex harvesting took place at a site near the Ayers Rock Resort, Northern Territory, Australia. Ten plots, each of 8.75 ha, were established and sampled from May 1994 to October 1995. Harvesting took place on five plots in August 1994, which reduced spinifex cover from 46 to 21% and the amount of spinifex >0.25 m high from 42 to 2%. Harvesting did not significantly affect the number of D. cristicauda known to be alive or captured despite other studies indicating that cover is an important habitat attribute. There was also no evidence that cover reduction impacted on the biomass of the invertebrate food resources. However, there was a significant reduction in the number of rodents captured. The lack of a response to cover reduction by D. cristicauda is possibly because the cover of Triodia remained high enough (above 15%) to sustain animals, and harvested areas were relatively small. This study therefore suggests that D. cristicauda can tolerate a moderate local reduction in cover of its preferred habitat. However, it remains possible that other land use practices that cause severe reduction of cover (including clearing for mining or fire prevention, grazing which may result in spinifex reduction through trampling, and fire management) will have more dramatic effects on D. cristicauda. Evaluation of such effects should be a priority for future research. [source] Winter selection of landscapes by woodland caribou: behavioural response to geographical gradients in habitat attributesJOURNAL OF APPLIED ECOLOGY, Issue 5 2008Daniel Fortin Summary 1Understanding animal,habitat relationships is central to the development of strategies for wildlife management and conservation. The availability of habitat attributes often changes along latitudinal and longitudinal axes, and animals may respond to those changes by adjusting their selection. We evaluated whether landscape selection by forest-dwelling woodland caribou Rangifer tarandus caribou varied along geographical gradients in habitat attributes. 2Centroids (n = 422) of track networks made by caribou in winter were recorded during aerial surveys conducted over 161 920 km2 of boreal forest in Québec, Canada. Autologistic models were estimated by comparing the characteristics of landscapes (201 km2) centred on each centroid to an equal number of randomly located landscapes, with an autocovariate controlling for the non-independence among caribou locations. 3The availability of habitat attributes varied along longitudinal and latitudinal gradients, and caribou altered their landscape selection with respect to those gradients. 4Information Theory provided substantial support for only one model. The model revealed that the probability of occurrence of caribou increased with the abundance of conifer forests over most of the study region, but this positive response gradually became negative towards the southern portion of the region. The association between caribou and lichens changed from being negative west of the study region to being positive in the eastern part. Availability of landscapes dominated by lichen decreased from west to east. Finally, caribou generally displayed an aversion to areas with high road density, a negative association that became positive in the southern part of the study region. 5Synthesis and applications. Under current legislation in Canada, the critical habitat of woodland caribou must be defined, and then protected. Our autoregressive models can help to identify landscapes to prioritize conservation efforts. The probability of occurrence of caribou was related to different landscape characteristics across their range, which implies that the typical habitat of woodland caribou differs spatially. Such behavioural plasticity could be problematic for defining critical habitat, but we showed that spatial variation in landscape selection was organized along geographical gradients. Our study illustrates how geographical trends in habitat selection can guide management and conservation decisions. [source] Diet of spider monkeys (Ateles geoffroyi) in Mesoamerica: current knowledge and future directionsAMERICAN JOURNAL OF PRIMATOLOGY, Issue 1 2009Arturo González-Zamora Abstract Here we review all published articles and book chapters, as well as unpublished theses and data of Ateles geoffroyi diet to (1) summarize the literature; (2) synthesize general feeding patterns; (3) document plant taxonomic similarity in diet across study sites; and (4) suggest directions for future research and conservation priorities. We found 22 samples from five countries: Mexico, Guatemala, El Salvador, Costa Rica and Panama. Tropical wet forest is the most studied habitat (N=13 samples), followed by tropical dry forest (6) and tropical moist forest (3). Most samples have been carried out in large protected forests. In spite of showing an overall high dietetic diversity (364 species, 76 families), A. geoffroyi concentrated the majority of feeding time on a few species in the families Moraceae and Fabaceae. At all study sites fruits were the most common food item in the diet followed by leaves. Furthermore, a greater variety of food items and less fruit were consumed in forest fragments. These findings suggest that fruit shortage in fragments results in primates using foods of presumably lower energetic content such as leaves. Similarity in diet was higher among groups geographically closer to each other than among distant groups, showing that the floristic and phenological characteristics of the forest can influence diet composition. We conclude that several years of data are required to fully describe the dietary list of A. geoffroyi at any one site, as studies of the same group over different years shared as little as 56% of species. As most populations of A. geoffroyi live in highly fragmented landscapes, it is crucial to carry out studies in these areas to evaluate (1) changes in diet and activity patterns that may negatively affect survival; and (2) habitat attributes that may favor their persistence in altered landscapes. Am. J. Primatol. 71:8,20, 2009. © 2008 Wiley-Liss, Inc. [source] Influence of mapping resolution on assessments of stream and streamside conditions: lessons from coastal Oregon, USA,AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2009Ken Vance-Borland Abstract 1.Digital hydrographic data are commonly employed in research, planning, and monitoring for freshwater conservation, but hydrographic datasets differ in spatial resolution and accuracy of spatial representation, possibly leading to inaccurate conclusions or unsuitable policies for streams and streamside areas. 2.To examine and illustrate the potential for different hydrographic datasets to influence in-channel and streamside characterizations, a study area in the US Pacific Northwest was chosen because 1:100,000, 1:24,000, and densified 1:24,000 hydrography are available and widely used in research and management for several species of Pacific salmon and trout at risk. The potential was examined for differences among the digital hydrographic datasets in: (1) spatial extent to influence estimated abundances of fish habitat, streamside buffer conditions, and fish distributions; and (2) spatial position to influence estimated streamside buffer conditions and estimated stream gradient. 3.The analysis of spatial extent found the total stream length represented by the 1:100,000 hydrography was approximately one half that of 1:24,000 hydrography and only one fifth that of densified 1:24,000 hydrography. The 1:100,000 and 1:24,000 networks differed significantly for 13 out of 18 fish habitat attributes, and the three hydrographic datasets differed significantly for many characteristics in streamside buffers; fish distributions mapped at 1:24,000 added 6,14% of stream length to 1:100,000 distributions. The analysis of spatial position found few differences between the 1:100,000 and 1:24,000 hydrography in streamside buffer characteristics but significant differences in channel gradient. 4.Overall, hydrographic datasets differed only slightly in spatial position but differed in spatial extent to the point of representing different populations of streams. If species inhabiting larger streams (greater mean annual discharge) are of interest, then results derived from studies based on 1:100,000 hydrography should prove useful. However, higher-resolution hydrography can be critical when designing and implementing strategies to protect fish and other aquatic species at risk in smaller streams. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||