Negative effects of density on space use of small mammals differ with the phase of the masting‐induced population cycle

Home range size generally decreases with increasing population density, but testing how this relationship is influenced by other factors (e.g., food availability, kin structure) is a difficult task. We used spatially explicit capture–recapture models to examine how home range size varies with population density in the yellow‐necked mouse (Apodemus flavicollis). The relationship between population density and home range size was studied at two distinct phases of population fluctuations induced by beech (Fagus sylvatica) masting: post‐mast peak in abundance (first summer after mast, n = 2) and subsequent crash (second summer after mast, n = 2). We live‐trapped mice from June to September to avoid the confounding effects of autumn seedfall on home range size. In accordance with general predictions, we found that home range size was negatively associated with population density. However, after controlling for the effect of density, home ranges of mice were larger in post‐mast years than during the crash phase. This indicates a higher spatial overlap among neighbors in post‐mast years. We suggest that the increased spatial overlap is caused by negative density‐dependent dispersal that leads to high relatedness of individuals within population in the peak phase of the cycle.     

Demographic differences in diet breadth of Canada lynx during a fluctuation in prey availability

Population dynamics of specialist carnivores are closely linked to prey availability, but the extent of variability in diet breadth of individual carnivores relative to natural variability in the abundance of their primary prey is not well understood. Canada lynx (Lynx canadensis) specialize on snowshoe hares (Lepus americanus) and exhibit cyclic fluctuations in abundance that lag 1–2 years behind those of snowshoe hares. Declining hare densities spur demographic changes in lynx, but it is unclear whether a corresponding increase in diet breadth occurs: (1) broadly across a lynx population; (2) only among individuals who are able to effectively switch to alternative prey; or (3) only among individuals who cannot capture sufficient primary prey. We measured stable isotope ratios of lynx muscle tissue spanning a cyclic increase and decline in hare density (1998–2001) in Fort Providence, NT, Canada. We found that lynx cohorts responded differently to hare population change, with yearling animals having broader diets at low hare densities, while adults and dependent juveniles maintained a constant diet through the initial decline in hare density. This result was consistent irrespective of lynx sex and indicates that yearling lynx likely are forced to adopt a broader diet when primary prey densities decline. Our results imply that select cohorts of specialist carnivores can exhibit high dietary plasticity in response to changes in primary prey abundance, prompting the need to determine whether increased diet breadth in young lynx is a successful strategy for surviving through periods of snowshoe hare scarcity. In this way, cohort‐specific niche expansion could strongly affect the dynamics of organisms exhibiting population cycles.     

Density-dependent reproduction causes winter crashes in a common vole population

Common voles in western France exhibit three-year population cycles with winter crashes after large outbreaks. During the winter of 2011–2012, we monitored survival, reproduction, recruitment and population growth rate of common voles at different densities (from low to outbreak densities) in natura to better understand density dependence of demographic parameters. Between October and April, the number of animals decreased irrespective of initial density. However, the decline was more pronounced when October density was higher (loss of ≈54 % of individuals at low density and 95 % at high density). Using capture-mark-recapture models with Pradel's temporal symmetry approach, we found a negative effect of density on recruitment and reproduction. In contrast, density had a slightly positive effect on survival indicating that mortality did not drive the steeper declines in animal numbers at high density. We discuss these results in a population cycle framework, and suggest that crashes after outbreaks could reflect negative effects of density dependence on reproduction rather than changes in mortality rates.     

Variable prey development time suppresses predator–prey cycles and enhances stability

Although theoretical models have demonstrated that predator–prey population dynamics can depend critically on age (stage) structure and the duration and variability in development times of different life stages, experimental support for this theory is non‐existent. We conducted an experiment with a host–parasitoid system to test the prediction that increased variability in the development time of the vulnerable host stage can promote interaction stability. Host–parasitoid microcosms were subjected to two treatments: Normal and High variance in the duration of the vulnerable host stage. In control and Normal‐variance microcosms, hosts and parasitoids exhibited distinct population cycles. In contrast, insect abundances were 18–24% less variable in High‐ than Normal‐variance microcosms. More significantly, periodicity in host–parasitoid population dynamics disappeared in the High‐variance microcosms. Simulation models confirmed that stability in High‐variance microcosms was sufficient to prevent extinction. We conclude that developmental variability is critical to predator–prey population dynamics and could be exploited in pest‐management programs.     

Differential Expression of microRNAs and their Regulatory Networks in Skin Tissue of Liaoning Cashmere Goat during Hair Follicle Cycles

MicroRNAs (miRNAs) are endogenous small noncoding RNA molecules that negatively regulate gene expression. Herein, we investigated a selective number of miRNAs for their expression in skin tissue of Liaoning Cashmere goat during hair follicle cycles, and their intracellular regulatory networks were constructed based on bioinformatics analysis. The relative expression of six miRNAs (mir-103-3p, -15b-5p, 17-5p, -200b, -25-3p, and -30c-5p) at anagen phase is significantly higher than that at catagen and/or telogen phases. In comparison to anagen, the relative expression of seven miRNAs (mir-148a-3p, -199a-3p, -199a-5p, -24-3p, -30a-5p, -30e-5p, and -29a-3p) was revealed to be significantly up-regulated at catagen and/or telogen stages. The network analyses of miRNAs indicated those miRNAs investigated might be directly or indirectly involved in several signaling pathways through their target genes. These results provided a foundation for further insight into the roles of these miRNAs in skin tissue of Liaoning Cashmere goat during hair follicle cycles.     

Exploiting the Potential of Public Procurement: Opportunities for Circular Economy

The objective of a circular economy (CE) is to maintain the value of products, materials, and resources in the economy by closing material loops and minimizing waste generation. In recent years, the role of public procurement has been recognized as an important, but as yet not fully exploited, opportunity by cities and municipalities in their transition toward circular societies. This study analyzed public procurement opportunities to promote CE. Different approaches and examples of circular public procurement were identified using case studies. In addition, opportunities to promote CE through sustainable and green public procurement policy were identified analyzing predefined sustainable or green public procurement criteria. The study concludes that public procurement can promote CE and related business models by setting criteria and requirements for the extension of product life spans, efficiency and/or intensity of use, and efficient cycling of biological or technical materials, as well as for the securing of clean and nonrisky cycles. Circular procurement can occur through the procurement of better‐quality products in circular terms, the procurement of new circular products, the use of business concepts that support the CE, and investments in circular ecosystems. Several sectors and product groups were identified as having potential for circular procurement, such as construction, waste, and wastewater management, transportation, food, and catering, furniture, and textiles. The study also suggests that the use of certain tools, such as performance‐based procurement, life cycle approach, and life cycle costing, as well as criteria concerning reuse and recycling of materials, could promote circular procurement. Market dialogue and cooperation between procurers and actors in the supply chains are important for the future development of circular procurement.     

Functional Access to Neuron Subclasses in Rodent and Primate Forebrain

1. Download high-res image (172KB)
2. Download full-size image

     

Niche characteristics of rodents by diverse disturbance in Alashan desert, Inner Mongolia, China

Four diverse disturbance types, namely, farmland, rotationally grazed grassland, overgrazed grassland and forbidden grazing grassland, were identified in the Alashan desert region of Inner Mongolia. Rodents were sampled in April, July and October in 2002 and 2003 using the trap-day method. Their spatial and temporal niches among the four disturbance types were assessed using the Shannon-Wiener niche breadth index and the Pianka niche overlap index. The Shannon-Wiener niche breadth index was the highest for Allactaga sibirica and Meriones meridianus (0.925 and 0.908, respectively), intermediate for Cricetulus eversmanni, Phodopus roborovskii and Citellus dauricus (0.789, 0.782 and 0.711, respectively), and lowest for Cardiocranius paradoxus (0.003). The Pianka niche overlap indices of six-paired species were the highest and varied from 0.900 to 1.000, suggesting their spatial niche overlapped almost completely. Conversely, the spatial niche overlap index for Meriones unguiculatus, Cardiocranius paradoxus, and Salpingotus kozlovi was zero, thus indicating a complete absence of competition among them. In addition, the temporal niche breadth and overlap indices varied greatly in relation to disturbance types and season. The level of temporal niche overlap in spring and autumn was low while in summer it was high. For all disturbance types and for each season, the temporal niche overlap index of Meriones meridianus and Cricetulus barabansis was always highest but for Meriones unguiculatus and Salpingotus kozlovi always lowest. __________ Translated from Acta Ecologica Sinica, 2005, 25(10): 2,637–2,643 [译自: 生态学报]     

Mating success of timed pregnancies in Sprague Dawley rats: Considerations for execution

This study compares three different mating techniques in Sprague-Dawley rats, using the pregnancy rate as the main indicator of success. It provides recommendations for timed-pregnancy experiments to achieve an appropriate sample size for the study of human pregnancy disorders. The implementation of a preconditioning phase, determination of the estrous cycle, the use of two mating strategies (Lee-Boot and Whitten effect), female: male mating ratios, and cohabitation duration should be considered as they improve the mating success rate.     

Impacts of large mammals on movements of the pouched mouse (Saccostomus mearnsi) in central Kenya

Populations of large wild mammals are declining worldwide, while the abundance of livestock is increasing. The absence of large mammals frequently leads to increases in the abundance of small mammals such as rodents, but little is known about how the loss of large mammals affects the behaviour of small mammals. To investigate this question, we analysed long‐term data collected at the Kenya Long‐term Exclosure Experiment, which excludes different combinations of large mammals from a savannah ecosystem in central Kenya. We investigated the effects of excluding large mammals, both wild and domestic, on the movements of the pouched mouse (Saccostomus mearnsi), the most common species of small mammal in this habitat. Mice moved ~20% more in the presence of wildlife, but their movements were not significantly affected by the presence of cattle. An index of intraspecific contacts between mice was higher at higher mouse densities, and these high densities were more likely when wildlife and cattle were absent. The results suggest that the absence of large mammals led to higher densities of small mammals, which resulted in a greater probability of intraspecific contacts, despite lower average movement distances.