Circadian activity of the fat dormouse Glis glis measured with camera traps at bait stations

Monitoring of small nocturnal and arboreal rodents is difficult and often conducted using indirect techniques. Here, we measured the circadian activity of the fat dormouse (Glis glis) directly using camera traps. The study took place at the Spitzberg in SW Germany. Data were collected using six Bushnell Natureview cameras with a macro lens at baited feeding stations. At 14 out of 41 active camera locations, edible dormice occurred. We collected 301 events between 8th July and 5th October 2018. There were 21.5 events per camera trap (SD 30.4), ranging from 1 to 82. The edible dormouse showed a nocturnal pattern, with a mean activity around midnight at 24:15 h. The pattern shows a slightly bimodal activity. Feeding activity started around or even slightly before sunset and stopped right before sunrise. The study shows that circadian activity, in this respect feeding activity, can be captured by camera trapping, which is a non-invasive method, and can be applied easily in the field.

Is nesting in closed nestboxes advantageous for the European Robin (Erithacus rubecula)?

Background The European Robin (Erithacus rubecula) is eurytopic in its choice of nest site, which can be either half-open or closed, and situated either on the ground or at a height of several meters. On occasion, robins also nest in closed nestboxes, though generally only solitary such cases are documented, albeit that dozens of such events can be recorded during the course of some long-term studies. However, until now, nobody has summarised the peculiarities of robins nesting in closed nestboxes. Methods In the period 1978–2020, wooden tit and starling nestboxes were inspected regularly at five study sites in Lithuania, this totaling more than 18,000 nestbox-seasons. During these inspections, 90 cases of robins nesting in the nestboxes were recorded. Publications on this topic from the entire robin distribution range were reviewed. Results Robins prefer to nest in old large-sized fairly shallow nestboxes with wide entrance holes, for example starling nestboxes or tit nestboxes with enlarged entrance holes. Increased numbers of nestboxes being occupied by robins were recorded for 3–8 years in row. In Lithuania, nesting success in nestboxes is not higher than compared with nesting on the ground. Tree climbing mammals, Pine Martens (Martes martes), Hazel Dormice (Muscardinus avellanarius), Edible Dormice (Glis glis) and Forest Dormice (Dryomys nitedula), are the main predators of robin nests in nestboxes. Conclusions Some geographic variation was found in the occurrence of robins nesting in nestboxes with more such cases recorded in central and southern parts of the range. Possibly robins are more philopatric in these parts of the range, with the same females or their offspring nesting in nestboxes for several years in row. In areas inhabited by dormice, nesting in closed nestboxes is not advantageous for robins.

Flickering body temperature anticipates criticality in hibernation dynamics

Hibernation has been selected for increasing survival in harsh climatic environments. Seasonal variability in temperature may push the body temperatures of hibernating animals across boundaries of alternative states between euthermic temperature and torpor temperature, typical of either hibernation or summer dormancy. Nowadays, wearable electronics present a promising avenue to assess the occurrence of criticality in physiological systems, such as body temperature fluctuating between attractors of activity and hibernation. For this purpose, we deployed temperature loggers on two hibernating edible dormice for an entire year and under Mediterranean climate conditions. Highly stochastic body temperatures with sudden switches over time allowed us to assess the reliability of statistical leading indicators to anticipate tipping points when approaching a critical transition. Hibernation dynamics showed flickering, a phenomenon occurring when a system rapidly moves back and forth between two alternative attractors preceding the upcoming major regime shift. Flickering of body temperature increased when the system approached bifurcations, which were also anticipated by several metric- and model-based statistical indicators. Nevertheless, some indicators did not show a pattern in their response, which suggests that their performance varies with the dynamics of the biological system studied. Gradual changes in air temperature drove transient between states of hibernation and activity, and also drove hysteresis. For hibernating animals, hysteresis may increase resilience when ending hibernation earlier than the optimal time, which may occur in regions where temperatures are sharply rising, especially during winter. Temporal changes in early indicators of critical transitions in hibernation dynamics may help to understand the effects of climate on evolutionary life histories and the plasticity of hibernating organisms to cope with shortened hibernation due to global warming.

Radio-transmitters gnawed by edible dormice Glis glis in populations of different density

In a radio-tracking study of the edible dormouse Glis glis in Poland, 20 transmitters out of 125 used showed traces of gnawing, presumably by other dormice. All gnawed devices were found in a high-density population (8.0–9.5 individuals/ha) and none in low-density populations (2.5–5.5 individuals/ha). Sex, reproductive activity and season had no perceived impact on the damage done to the transmitters.