Archaea and Bacteria constitute a majority of life systems on Earth but have long been considered inferior to Eukarya in terms of solute tolerance. Whereas the most halophilic prokaryotes are known for an ability to multiply at saturated NaCl (water activity (aw) 0.755) some xerophilic fungi can germinate, usually at high-sugar concentrations, at values as low as 0.650–0.605 aw. Here, we present evidence that halophilic prokayotes can grow down to water activities of <0.755 for Halanaerobium lacusrosei (0.748), Halobacterium strain 004.1 (0.728), Halobacterium sp. NRC-1 and Halococcus morrhuae (0.717), Haloquadratum walsbyi (0.709), Halococcus salifodinae (0.693), Halobacterium noricense (0.687), Natrinema pallidum (0.681) and haloarchaeal strains GN-2 and GN-5 (0.635 aw). Furthermore, extrapolation of growth curves (prone to giving conservative estimates) indicated theoretical minima down to 0.611 aw for extreme, obligately halophilic Archaea and Bacteria. These were compared with minima for the most solute-tolerant Bacteria in high-sugar (or other non-saline) media (Mycobacterium spp., Tetragenococcus halophilus, Saccharibacter floricola, Staphylococcus aureus and so on) and eukaryotic microbes in saline (Wallemia spp., Basipetospora halophila, Dunaliella spp. and so on) and high-sugar substrates (for example, Xeromyces bisporus, Zygosaccharomyces rouxii, Aspergillus and Eurotium spp.). We also manipulated the balance of chaotropic and kosmotropic stressors for the extreme, xerophilic fungi Aspergillus penicilloides and X. bisporus and, via this approach, their established water-activity limits for mycelial growth (∼0.65) were reduced to 0.640. Furthermore, extrapolations indicated theoretical limits of 0.632 and 0.636 aw for A. penicilloides and X. bisporus, respectively. Collectively, these findings suggest that there is a common water-activity limit that is determined by physicochemical constraints for the three domains of life.
Summary 1.Livestock grazing is an important form of land use across the globe and changes in grazing pressure can have profound effects on vertebrate populations. 2. In Scotland, over the last decade sheep numbers in many areas have declined from historically high levels, providing an opportunity to explore the implications of these declines for biodiversity. 3. The hen harrier Circus cyaneus is a bird of high conservation importance in the UK, and a species that may be heavily influenced by the indirect effects of sheep on habitat and prey. The hen harrier population on the Orkney Islands in Scotland has been monitored since 1975 and represents an ideal case study for considering the impact of sheep de-stocking on a key predator. 4. Declines in the harrier population were associated with a doubling in sheep numbers between the early 1980s and the late 1990s. Subsequently, as sheep numbers have fallen the harrier population has recovered. These changes indicate an association but no clear mechanism, so we tested whether reductions in sheep numbers have led to increases in harrier prey or preferred foraging habitat. We then tested whether breeding output over the last 33 years correlates with sheep stocking levels or variation in weather conditions (rainfall and temperature). 5. Orkney sheep numbers declined by about 20% between 1998 and 2008. Surveys in 1999 ⁄ 2000 and repeated in 2008 showed increases in rough grassland, the preferred harrier foraging habitat, and increases in a key prey species, the Orkney vole Microtus arvalis orcadensis. 6. Overall, hen harrier breeding output over the last 33 years was significantly negatively correlated to both sheep abundance and spring rainfall. 7. Synthesis and application. This study provides strong evidence for the consequences of changes in sheep numbers on a top predator. Our results indicate that reductions in sheep numbers are likely to prove beneficial for some upland species, particularly small mammals and their predators.
Archaeological work preceding a housing development revealed mid-Devensian (MIS 3) deposits preserved in a geological fault, a graben feature, on an interfluve plateau. Rare evidence for Early Upper Palaeolithic open-air occupation was characterised by a scant lithic signature of the Lincombian-Ranisian-Jerzmanowician (LRJ) leaf-point techno-complex of the North European plain. The lithics included a complete leaf-point, another broken example with traces of impact damage, and knapping debitage indicating leaf-point maintenance. The site also preserved good evidence for an open-air hyaena den with abundant faunal remains. Discrete bone clusters were present, some of which probably represent meat caches for hyaena cubs in the burrows and scrapes of a maternity den. It is suggested that the hominins targeted the den site to forage the stored food. Their occupation is associated with a group of spirally-fractured wild horse bones thought to be the result of marrow extraction by humans, and these have been dated to 44,290–42,440 calibrated years before present (44.3–42.5 kyr cal bp), comparable to the date range of continental LRJ sites. The early date of the LRJ techno-complex corresponds with that of the oldest Neanderthals in northern Europe, but possibly overlaps with the recently reported early dates for anatomically modern humans. However, it is concluded that the oldest Early Upper Palaeolithic technology in northern Europe was the product of final Neanderthals.
Differing environmental conditions can have profound effects on many behaviours in animals, especially where species have large geographic ranges. Seasonal changes or progression through life history stages impose differential constraints, leading to changes in behaviours. Furthermore, species which show flexibility in behaviours, may have a higher capacity to adapt to anthropogenic‐induced changes to their environment. The red‐throated diver (RTD) is an aquatic bird, that is able to forage in both freshwater and marine environments, though little else is known about its behaviours and its capacity to adapt to different environmental conditions. Here, we use time‐depth recorders and saltwater immersion loggers to examine the foraging behaviour of RTDs from three regions across northwest Europe. We found that in the breeding season, birds from two regions (Iceland and Scotland) foraged in the marine environment, while birds from Finland, foraged predominantly in freshwater. Most of the differences in diving characteristics were at least partly explained by differences in foraging habitat. Additionally, while time spent foraging did not change through the breeding season, dives generally became more pelagic and less benthic over the season, suggesting RTDs either switched prey or followed vertical prey movements, rather than increasing foraging effort. There was a preference for foraging in daylight over crepuscular hours, with a stronger effect at two of the three sites. Overall, we provide the first investigation of RTD foraging and diving behaviour from multiple geographic regions and demonstrate variation in foraging strategies in this generalist aquatic predator, most likely due to differences in their local environment.
Feeding behaviors may differ between past and current predators due to differences in the environments inhabited by these species at different times. We provide an example of this behavioral variability in spotted hyena (Crocuta crocuta), for which our analysis of a late Pleistocene micromammal assemblage indicates that hyenas preyed upon small rodents, a feeding habit that is rarely observed today among hyenas.The Bois Roche cave site is situated at the edge of a low bluff overlooking the floodplain of a small stream in Cherves-Richemont (Charente, France). The deposits are dated by electron spin resonance (ESR) to about 69.7 ± 4.1 Ka. Excavations at the site recovered fossil bones and teeth of large and small mammals, together with hyena coprolites. Water screening of the sediments produced large accumulations of rodent remains with low taxonomic diversity. Small mammal bones were recovered from hyena coprolites as well. Descriptions of small mammal bone modification, both from the sediments and coprolites, are reported here. The analysis yielded a distinct taphonomic pattern representative of large carnivores (over 30 kg), which differs from any other modern or fossil predator-accumulated microfaunal assemblage taphonomically analyzed to date. To our knowledge, previous studies of hyena diet have not recorded high concentrations of a single-rodent prey species. We conclude that the low species diversity of this small mammal assemblage most likely relates to a local abundance of the prey species due to an outbreak in the rodent population, rather than from specialist predator behavior and hunting technique.
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