Background Biologgers have contributed greatly to studies of animal movement, behaviours and physiology. Accelerometers, among the various on-board sensors of biologgers, have mainly been used for animal behaviour classification and energy expenditure estimation. However, a general principle for the combined sampling duration and frequency for different taxa is lacking. In this study, we evaluated whether Nyquist–Shannon sampling theorem applies to accelerometer-based classification of animal behaviour and energy expenditure approximation. To evaluate the influence of accelerometer sampling frequency on behaviour classification, we annotated accelerometer data from seven European pied flycatchers (Ficedula hypoleuca) freely moving in aviaries. We also used simulated data to systematically evaluate the combined effect of sampling duration and sampling frequency on the performance of estimating signal frequency and amplitude. Results We found that a sampling frequency higher than Nyquist frequency at 100 Hz was needed to classify fast, short-burst behavioural movements of pied flycatcher, such as swallowing food with a mean frequency of 28 Hz. In contrast, high frequency movements with longer durations such as flight could be characterized adequately using much lower sampling frequency of 12.5 Hz. To identify rapid transient prey catching manoeuvres within these flight bouts, again a high frequency sampling at 100 Hz was needed. For both the experimental data of the flycatchers and the simulated data, the combination of sampling frequency and sampling duration affected the accuracy of signal frequency and amplitude estimation. For long sampling durations, the sampling frequency equal to the Nyquist frequency was adequate for accurate signal frequency and amplitude estimation. Accuracy declined with decreasing sampling duration, especially for signal amplitude estimation with up to 40% standard deviation of normalized amplitude difference. To accurately estimate signal amplitude at low sampling duration, a sampling frequency of four times the signal frequency was necessary (two times the Nyquist frequency). Conclusions The appropriate sampling frequency of accelerometers depends on the objective of the specific study and the characteristics of the behaviour. For studies with no constraints on device battery and storage, a sampling frequency of at least two times the Nyquist frequency will achieve relative optimal representative of signal information (i.e., frequency and amplitude). For classification and energy expenditure estimation of short-burst behaviours, 1.4 times the Nyquist frequency of behaviour is required.
ZusammenfassungUnfälle mit Gifttieren bei Reisenden sind selten. Die einheimische Bevölkerung ist meist gefährdeter. Vor einer Reise wird die Information über die vorkommenden Gifttiere empfohlen. Die Verhinderung einer Gifttierverletzung durch umsichtiges Verhalten steht im Vordergrund. Kommt es zu einer Verletzung, sollte nach den allgemeinen Erstmaßnahmen ein Arzt aufgesucht werden, um zu klären, ob eine spezifische Therapie nötig ist.
Background Different sampling approaches can be used in longitudinal surveys. The COVID-19 pandemic disrupted possibilities to conduct random based longitudinal surveys. However, longitudinal data on public mental health responses are urgently needed. Methods We conducted a longitudinal study in eight European countries (Albania, Belgium, Germany, Italy, Lithuania, Romania, Serbia, Slovenia) including 18+ year olds with the goal to reach as many people as possible and generate robust data. We used various sampling approaches (convenience sampling, snowball sampling, panel data) utilizing social media, professional organisations, educational institutions and personal direct contact. To gather robust data, focus was on multiperspectivity rather than representativeness. A mix of sampling approach is possible. Digital sampling methods were feasible in the European region. Results In total 2,426 participants filled out >50% of the questionnaire in the overall sample, which is, also due to the rapidness of survey development, a good result for data on mental health and resilience during COVID-19 pandemic. COPERS study has shown that a mix of various sampling approaches is possible and a good option to generate datasets in a relatively short time span. However, no responses rates can be calculated using. Conclusions Online surveys are a good tool to reach people in times of crisis. Furthermore, they can be adapted directly in case of changes, if necessary and desired. Using different ways of recruitment, a diverse group of people can be recruited. However, online surveys require a certain technical understanding, which not all potential participants have. Question remains how multinational research is evolving and being shaped. This asks for possibly new methods to define and detect sampling bias.
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