DNA-based seed intake quantification for enhanced ecological risk assessment of small mammals.

To prevent the non-acceptable effects of agrochemicals on arable fields, Environmental Risk Assessment (ERA) aims to assess and protect against a wide range of risks due to stressors to non-target species. While exposure to stress is a key factor in ERA models, exposure values are difficult to obtain and rely on laboratory studies with often debatable relevance to field situations. To improve intake estimates, data from realistic field-based scenarios are needed. We developed calibration curves relating known seed numbers of up to 20 onion and carrot seeds consumed by wild-caught wood mice (Apodemus sylvaticus) to the seed DNA content in the feces. Based on these inferred quantitative relationships, a field trial was run to determine seed intake in a natural setting using realistic levels of seed spillage. Onion DNA was detected in the fecal samples of the wood mice caught in the field, which resembled a seed intake of up to 1 onion seed. No intake of carrot seeds was detected. This is the first-ever study to quantify seed intake in a realistic field scenario using a DNA-based analysis, showing that accurate seed intake estimates can be obtained. Our approach can help to improve risk assessment models through its minimally-invasive and accurate assessment of seed intake by ERA representative and non-target species, which would otherwise be undetectable with traditional methods. Our novel approach and its results are highly relevant to studies of food intake and diet composition for basic and applied research alike.

Establishment of a faecal DNA quantification technique for rare and cryptic diet constituents in small mammals.

DNA-based approaches have greatly improved the applicability of dietary studies aimed at investigating ecological processes. These studies have provided direct insights into, otherwise difficult to measure, interactions between species and trophic levels, food web structure and ecosystem functioning. However, despite these advances, DNA-based methods have struggled to accurately quantify the whole breadth of diet constituents because of methodological biases, such as amplification bias and digestive processes. The present study is, to our knowledge, the first diet study to use droplet digital PCR to quantify diet constituents. We manipulated the diet of wild-caught wood mice (Apodemus sylvaticus) by feeding them with a known amount of small vegetable seeds (onion and carrot) and quantified the DNA traces of these diet constituents in faecal samples. The sensitivity of the technique combined with the control on the experimental design allowed mitigation of methodological bias. We were able to accurately determine DNA concentrations of small vegetable seeds in the diet of wood mice. Quantification of target DNA demonstrated significant differences in DNA content when one vs. five seeds were consumed. These differences remained significant when the age, sex and other diet constituents of the mice were altered. Different DNA markers, targeting different parts of the chloroplast, influenced onion DNA detectability. However, all onion and carrot markers showed higher DNA content for higher seed numbers. Overall, the sensitive DNA-based approach developed in this study allows for minimally invasive quantification of small diet constituents in faeces, which would otherwise be undetectable with traditional methods.

Population recovery of a common vole population (Microtus arvalis) after population collapse.

BACKGROUND: Population collapses in small mammals occur naturally after natural disasters and during multi-annual population fluctuations as well as after man-made intervention such as rodent management action. Although there has been extensive previous work on patterns and mechanisms of population fluctuations and cyclicity, little is known about population recovery after collapse. In Europe, the common vole (Microtus arvalis) is the major pest species in agriculture, damaging crops, competing with livestock and potentially posing a health risk to people. In this study, we investigated population recovery, recovery mechanism and recovery time of common vole populations after artificially inducing a collapse through rodenticide application. RESULTS: The rodenticide treatment reduced abundance in spring (by about 90%) but not in summer. Demographic data (age, sex-ratio, breeding activity) suggest that it was mostly immigration and not reproduction that led to population recovery after collapse. CONCLUSIONS: The findings indicate that rodenticide treatment should be conducted in spring before the main reproductive season starts. The treatment effect was transient and lasted for about 3 months before immigration offset the initial reduction in population abundance. This indicates that immigration patterns should be considered by managing vole populations at an appropriate spatial scale and frequency to prevent rapid repopulation. © 2018 Society of Chemical Industry.

Feasibility, understandability, and usefulness of the STEP self-rating questionnaire: results of a cross-sectional study.

The study was designed to evaluate the acceptance of the self-rated version of the Standardized Assessment of Elderly People in primary care in Europe (STEP) by patients and general practitioners, as well as the feasibility, comprehensibility, and usefulness in gaining new information. In all, 1007 of 1540 patients aged 65 and above, from 28 different Saxon general practices took part. We recognized that 96% of the patients were able to fill in the questionnaire by themselves. It took them an average of approximately 20 minutes to do so. Further analysis of 257 randomly selected patients identified 281 previously unknown problems (1.1 per patient). In the practitioners' opinion, 16% of these problems, particularly physiological and mental ones, could lead to immediate consequences. Remarkably, newly identified psychosocial problems were not followed by any consequences. Fourteen of the 75 questionnaire items were not answered by more than 9% of the participants. Eight of the 14 frequently unanswered items were marked as difficult to understand by the patients. Altogether the self-rating version of the STEP was found to be feasible and useful. It was well accepted among patients; however, some questions need further review to improve their comprehensibility. Furthermore, it should be investigated why some identified problems do not have consequences and whether there is a need to record these issues at all.