The distribution and status of the polecat Mustela putorius in Luxembourg

1. The presence and distribution of the polecat Mustela putorius in Luxembourg was studied for the first time. Postal surveys were conducted among all the tenants of the hunting areas and all the farmers in the country. 2. Except for the otter Lutra lutra, the polecat appears to be the least common mustelid in Luxembourg. Farmers and hunters perceived the polecat differently according to their interests. Farmers had a more tolerant attitude towards the species but 17% still considered it a pest. 3. Live trapping of polecats was carried out for 3 years: 16 individuals were caught. This suggests a very low population density. Hunting records of this mustelid were examined for the period 1955–2000. There has been a very strong decrease in the number of polecats killed, giving rise to concerns that its population may be dramatically declining. Moreover, hunting data from neighbouring Germany confirm that this is a regional situation.     

Reserve Size,Conspecific Density,and Translocation Success for Black Rhinoceros

Abstract: Fighting and accidental injury commonly cause black rhinoceros (rhino; Diceros bicornis) death after release. Smaller reserves and higher conspecific density after release (release density) might increase a rhino's encounter rate with hazards like fenced boundaries and conspecifics. We conducted a science-by-management experiment on the influence of reserve size and release density on rates of movement, association, and injury and death amongst 39 black rhinos during the first 100 days after their release into 4 Namibian and 8 South African reserves ranging in size from 670 ha to 45,000 ha. Association rates were negatively related to reserve size and positively correlated with release density. There was also a negative relationship between the proportion of the reserve traversed by individual rhinos and reserve size. In reserves ≥18,000 ha association rates were consistently zero but became elevated in reserves ≤11,500 ha and at release densities ≤9 km²/rhino. Daily displacement did not increase with increasing reserve size >8,500 ha but in smaller reserves daily displacements indicated higher encounter rates by released rhinos with fenced boundaries. Three rhinos received fight-related injuries requiring intervention and 2 of 4 deaths were fight-related. All injuries and 3 deaths occurred in reserves ≤11,500 ha. Model selection based on Akaike's second-order Information Criterion indicated that the parameter release density alone best explained mortality risk. Traditionally considered risk factors, rhino sex, age, and presence of resident conspecifics, were superseded by the risk posed by releases into smaller reserves. Reserves ≤11,500 ha and release densities ≤9 km²/rhino pose an increasing risk to rhino survivorship and so larger reserves and lower densities than these should be favored as release sites.     

Neotropical Frog Biogeography: Paradigms and Problems

SYNOPSIS. The distributions and relationships of exemplary speciesgroups of the Neotropical frog genera Cycloramphus and Leptodactylusare discussed in terms of current biogeographic models. Fromthis exercise, the following conclusions emerge: (1) frog biogeographyis and will remain primarily a correlative science; (2) bothmorphological and genetic data are required to choose amongalternate biogeographic models; (3) frog speciation events significantlypredate recent distributional events complicating the understandingof past and recent distributions; (4) both data and theory areinadequate to completely understand Neotropical frog biogeographyat present.     

Glucose Utilization by Euglena gracilis var. bacillaris at Higher pH*

SYNOPSIS. Euglena gracilis var. bacillaris is able to grow luxuriantly on glucose in a mineral salts medium at pH 6.8–7.1 following an adaptation period of about 200 hr. If adapted cells are used as an inoculum or if 0.1% glycine is included in the medium, the lag is shortened to 70–100 hr. Inclusion of 0.1% acetate in the medium produces a diphasic growth pattern, with acetate being metabolized first, followed by the later (about 400 hr) utilization of the glucose. Glucose utilization was found to be sensitive to pH as compared to growth on ethyl alcohol. However, glycine partially overcame this sensitivity. Glycine is maximally stimulatory with regard to growth on glucose at pH 7.0 at a concentration of 0.03%, thus suggesting that it functions as a sparking substance. Glycine markedly stimulates the assimilation of ¹⁴C-glucose. A number of Krebs cycle acids and amino acids were also found to stimulate ¹⁴C-glucose assimilation at neutral pH. Adaptation to glucose utilization at neutral pH was due to the appearance of mutants able to grow more rapidly under these conditions. The nature of this mutation was not determined.     

Massive mortality of aspen following severe drought along the southern edge of the Canadian boreal forest

Drought‐induced, regional‐scale dieback of forests has emerged as a global concern that is expected to escalate under model projections of climate change. Since 2000, drought of unusual severity, extent, and duration has affected large areas of western North America, leading to regional‐scale dieback of forests in the southwestern US. We report on drought impacts on forests in a region farther north, encompassing the transition between boreal forest and prairie in western Canada. A central question is the significance of drought as an agent of large‐scale tree mortality and its potential future impact on carbon cycling in this cold region. We used a combination of plot‐based, meteorological, and remote sensing measures to map and quantify aboveground, dead biomass of trembling aspen (Populus tremuloides Michx.) across an 11.5 Mha survey area where drought was exceptionally severe during 2001–2002. Within this area, a satellite‐based land cover map showed that aspen‐dominated broadleaf forests occupied 2.3 Mha. Aerial surveys revealed extensive patches of severe mortality (>55%) resembling the impacts of fire. Dead aboveground biomass was estimated at 45 Mt, representing 20% of the total aboveground biomass, based on a spatial interpolation of plot‐based measurements. Spatial variation in percentage dead biomass showed a moderately strong correlation with drought severity. In the prairie‐like, southern half of the study area where the drought was most severe, 35% of aspen biomass was dead, compared with an estimated 7% dead biomass in the absence of drought. Drought led to an estimated 29 Mt increase in dead biomass across the survey area, corresponding to 14 Mt of potential future carbon emissions following decomposition. Many recent, comparable episodes of drought‐induced forest dieback have been reported from around the world, which points to an emerging need for multiscale monitoring approaches to quantify drought effects on woody biomass and carbon cycling across large areas.     

The origin and paleoecologic significance of the trace fossil Asteriacites in the Pennsylvanian of Kansas and Missouri

The trace fossil Asteriacites, recorded in Cambrian to Recent shallow- and deep-marine facies, is traditionally interpreted as the resting trace of asterozoans. Well-preserved specimens of A. lumbricalis are abundant in Pennsylvanian (Upper Carboniferous) shallow- and marginal-marine siliciclastic deposits of eastern Kansas and western Missouri. Detailed morphologic analysis of these specimens suggests that they record the activities of mobile epifaunal ophiuroids. Evidence of a brittle star (ophiuroid) producer rather than sea star (asteroid) is provided by (1) trace-fossil morphologic features reflecting the anatomy of the producer (e.g., well-differentiated central structure, slender vermiform arms) and ophiuroid burrowing technique (e.g., proximal arm expansion, arm branching), and (2) mode of occurrence (e.g., gregarious behavior, horizontal and vertical repetition). Vertical and horizontal repetition produces complex aggregates of A. lumbricalis that are interpreted either as escape structures (fugichnia) or as feeding structures, respectively. Ophiura texturata is proposed as a modern analogue for the A. lumbricalis producer, based on inferred life habit and feeding behavior. Asteriacites lumbricalis is present in two different intertidal trace-fossil assemblages. The first assemblage is characterized by high diversity and records tidal flats developed outside of embayments under normal marine conditions. The second assemblage consists of A. lumbricalis together with a few other ichnotaxa and represents a depauperate association that developed in restricted tidal flats within an embayment or estuarine setting. This challenges the conventional view of Asteriacites as a normal-marine salinity indicator. Some echinoderms, and particularly asterozoans, penetrate and inhabit modern environments of depressed salinity. The presence of Asteriacites in Pennsylvanian marginal-marine facies of Kansas and Missouri provides evidence that ophiuroids had adapted to brackish-water conditions by the late Paleozoic.