Biology subjects

Stryjek, R.

Publications and source records attributed to Stryjek, R..

4 recordsLinked to original sources

bioRxiv2026

Killer Mice: First Documentation of Lethal and Near-Lethal Attacks on Bank Voles by Free-Living Yellow-Necked Mice

In nature, the most common drivers of lethal aggression are predation and territorial defense. In northeastern Poland, the yellow-necked mouse (Apodemus flavicollis) coexists with several rodent species, including the bank vole (Clethrionomys glareolus). Compared to voles, A. flavicollis is larger, physically stronger, more aggressive, and dominant in the social ecosystem. However, no visually documented instance of a lethal attack by this species has been reported up to date. Here, we present the first recorded case of a fatal attack by a yellow-necked mouse following an encounter with a bank vole. A near-lethal attack is also reported. Importantly, these attacks were not predatory, as no consumption occurred. The attacks appeared instead to be related to interspecies competition, i.e., to competitive interactions between two species that live in the same habitat and use the same type of resources. Notably, while the aggressiveness of yellow-necked mice towards bank voles was known, it was unknown that it could take such extreme forms. Since, in rodents, most competition-related agonistic interactions are aimed at distancing the competitor, the physical destruction of the competitor appears as a surprisingly extreme way of addressing the game of interspecies competition through definitive removal of the opponent. Our observations highlight the need for further research on interspecific aggression among small mammals. They also emphasize the importance of field-based methods, such as camera trapping and continuous video monitoring, which allow for direct observation of animal behavior in natural settings and can reveal rare or previously overlooked interactions.

animal behavior and cognition↗

bioRxiv2026

Chronoecological interactions: Temporal niche-switching by black-striped mice after agonistic food competition with a dominant sympatric mouse species

When novel nutrient-rich food sources become available to species sharing the same natural habitat, interspecies competition may arise, yielding insights into the ecological and social dynamics of the observed species. Here, we investigated food consumption patterns, and consequent social interactions, by two sympatric species of mice in response to a novel nutrient-rich food source. By deploying, in the mices natural habitat, baited video-monitored chambers, we collected, over a 5-month period, 1805 observations of food visiting by Apodemus agrarius and Apodemus flavicollis. We also documented interspecific encounters, with 86.7% of the cases showing agonism. In these interspecies agonistic encounters, A. flavicollis was always the initiator of agonism, attacking within 2 sec in 92.3% of the cases, and being dominant over A. agrarius in 84.6%. Analysis of food visiting behavior revealed that, initially, both species preferred nocturnality. However, after the interspecies fights, A. agrarius switched its temporal preference to diurnality, leading to temporal niche segregation between the two species and a significant reduction of interspecies encounters. Moreover, A. agrarius demonstrated hour-specific avoidance of A. flavicollis, visiting significantly less in hours with A. flavicollis compared to hours without. Through temporal niche switching, A. agrarius managed to access the food source safely, without fights. In contrast, A. flavicollis remained consistently nocturnal across the entire study. Notably, our study presents the first 24h foraging actogram for free-living rodents. Moreover, while rodent interspecific competition is a well-known phenomenon, most of what we know about it comes from indirect observations. Direct observations of rodent interspecific interactions in nature are rare. Our work is the first direct (video-monitored) observation of temporal switch-inducing interspecies interactions in nature. As free-living rodents are currently considered a major model system for the study of interspecific competition, these results may offer precious insights for a better understanding of social dynamics, especially in asymmetric relationships. Furthermore, our findings highlight the significance of considering temporal dynamics in studies of interspecific interactions.

animal behavior and cognition↗

bioRxiv2025

Circadian rhythm distinctness predicts academic performance based on large-scale learning management system data

The subjective amplitude of circadian oscillations (distinctness) is an understudied dimension of circadian rhythmicity, which describes how strongly mood and cognition fluctuate during the day. Emerging evidence suggests that distinctness may be as important as chronotype in regulating the temporal organization of key physiological processes. Previous studies have relied on questionnaires and lacked an objective measure of distinctness. Here, we propose the first objective behavioral measure of distinctness based on circular statistics. We applied this approach to 3.4 million login events from 13,894 unique university students and found a non-linear association between distinctness and academic performance: students with moderate daily rhythmicity achieved the highest performance. This relationship varied by chronotype: larks benefited from stronger rhythms, finches from moderate rhythms, and owls from weaker, more flexible rhythms. Circadian distinctness was also closely linked to social jetlag, which increased with more rigid rhythmicity across chronotypes. These findings suggest that the academic disadvantage often attributed to specific chronotypes does not stem from time preference itself, but from the overall interplay of chronotype, distinctness, and schedules that are incompatible with individual biological timings. Considering rhythm flexibility alongside chronotype may therefore improve educational design and equity.

animal behavior and cognition↗

bioRxiv2021

First record of 'tail-belting' in two species of free-ranging rodents (Apodemus flavicollis and Apodemus agrarius): Adaptation to prevent frostbite?

Rodents are among the most successful mammals because they have the ability to adapt to a broad range of environmental conditions. Here, we present the first record of a hitherto unknown thermal adaptation to low temperatures that repeatedly occurred in two species of non-commensal rodents (Apodemus flavicollis and Apodemus agrarius) between January 16 and February 11, 2021. The classic rodent literature implies that rodents prevent heat loss via a broad range of behavioral adaptations including sheltering, sitting on their tails, curling into a ball, or huddling with conspecifics. Yet, we have repeatedly observed an undescribed behavior which we refer to as "tail-belting". The behavior was performed during the lowest temperatures, whereby animals - which were attracted out of their over-wintering burrows for a highly-palatable food reward - lift and curl the tail medially, before resting it on the dorsal, medial rump while feeding or resting between feeding bouts. We documented 115 instances of the tail-belting behavior; 38 in Apodemus agrarius, and 77 in Apodemus flavicollis. In A. flavicollis, this behavior was only observed below -6.9C, and occurred more often than in A. Agrarius. The latter only demonstrated the behavior below -9.5C. We further detail the environmental conditions under which the behavior is performed, and provide possible functions. We then set several directions for future research in this area.

physiology↗