Species composition and interspecific behavior affects activity pattern of free-living desert hamsters in the Alashan Desert

Animal-friendly behavioral testing in field studies: examples from ground squirrels

Field studies of behavior provide insight into the expression of behavior in its natural ecological context and can serve as an important complement to behavioral studies conducted in the lab under controlled conditions. In addition to naturalistic observations, behavioral testing can be an important component of field studies of behavior. This mini review evaluates a sample of behavioral testing methods in field studies to identify ways in which behavioral testing can be animal-friendly and generate ethologically relevant data. Specific examples, primarily from studies of ground squirrels, are presented to illustrate ways in which principles of animal-friendly behavioral testing can be applied to and guide testing methods. Tests conducted with animals in their natural habitat and that elicit naturally occurring behavioral responses can minimize stress and disturbance for animals, as well as disruption of the larger ecosystem, and can have high ethological validity. When animals are trapped or handled as part of a study, behavioral testing can be incorporated into handling procedures to reduce overall disturbance. When behavior is evaluated in a testing arena, the arena can be designed to resemble natural conditions to increase the ethological relevance of the test. Efforts to minimize time spent in testing arenas can also reduce disturbance to animals. Adapting a behavioral test to a species or habitat conditions can facilitate reduced disruption to subjects and increased ethological relevance of the test.

Rodents Inhabiting the Southeastern Mu Us Desert May Not Have Experienced Prolonged Heat Stress in Summer 2022

Climate change combined with human activities has altered the spatial and temporal patterns of summer extreme heat in the Mu Us Desert. To determine how those rodents living in the desert respond to increased extreme heat in summer, in July 2022, during the hottest month, we examined the rodent species, vegetation coverage, and small-scale heterogeneity in ambient temperature in the southeastern Mu Us Desert. The results showed that Meriones meridianus, Meriones unguiculatus, and Cricetulus longicaudatus were found in the study area, where the vegetation coverage is 33.5-40.8%. Moreover, the maximum temperature of the desert surface was 61.8 °C. The maximum air temperature at 5 cm above the desert surface was 41.3 °C. The maximum temperature in the burrow at a depth of 15 cm was 31 °C. M. unguiculatus might experience 4-9.3 h of heat stress in a day when exposed outside the burrow, whereas M. meridianus would experience 8.5-10.8 h of heat stress. Yet, inside the burrow, both species were barely exposed to heat stress. In conclusion, adjustments in behavioral patterns can be the main way that rodents in the Mu Us Desert adapt to the extreme heat in the summer.

Activity patterns and interactions of rodents in an assemblage composed by native species and the introduced black rat: implications for pathogen transmission

Background

The degree of temporal overlap between sympatric wild hosts species and their behavioral interactions can be highly relevant to the transmission of pathogens. However, this topic has been scantly addressed. Furthermore, temporal overlap and interactions within an assemblage of wild rodents composed of native and introduced species have been rarely discussed worldwide. We assessed the nocturnal activity patterns and interactions between rodent taxa of an assemblage consisting of native species (Oligoryzomys longicaudatus, Abrothrix hirta, and Abrothrix olivaceus) and the introduced black rat (Rattus rattus) in a temperate forest from southern Chile. All rodent species in this study are known hosts for various zoonotic pathogens.

Results

We found a high nocturnal temporal overlap within the rodent assemblage. However, pairwise comparisons of temporal activity patterns indicated significant differences among all taxa. Rattus rattus showed aggressive behaviors against all native rodents more frequently than against their conspecifics. As for native rodents, agonistic behaviors were the most common interactions between individuals of the same taxon and between individuals of different taxa (O. longicaudatus vs Abrothrix spp.).

Conclusions

Our findings reveal several interactions among rodent taxa that may have implications for pathogens such as hantaviruses, Leptospira spp., and vector-borne pathogens. Furthermore, their transmission may be facilitated by the temporal overlap observed between rodent taxa.

Activity strategy and pattern of the Siberian jerboa (Orientallactaga sibirica) in the Alxa desert region, China

Rodents exhibit seasonal changes in their activity patterns as an essential survival strategy. We studied the activity patterns and strategies of the Siberian jerboa (Orientallactaga sibirica) in the Alxa desert region to better understand the habitats and behavioural ecology of xeric rodents. We conducted an experiment using three plots to monitor the duration, time, and frequency of the active period of the Siberian jerboa using infrared cameras in the Alxa field workstation, Inner Mongolia, China in 2017. The relationships between the activity time and frequency, biological factors (perceived predation risk, food resources, and species composition), and abiotic factors (temperature, air moisture, wind speed) were analysed using Redundancy Analysis (RDA). Our results showed that: (1) relative humidity mainly affected activities in the springtime; temperature, relative humidity and interspecific competition mainly affected activities in the summertime; relative humidity and perceived predation risk mainly influenced activities in the autumn. (2) The activity pattern of the Siberian jerboa altered depending on the season. The activity of the Siberian jerboa was found to be bimodal in spring and summer, and was trimodal in autumn. The activity time and frequency in autumn were significantly lower than the spring. (3) Animals possess the ability to integrate disparate sources of information about danger to optimize energy gain. The jerboa adapted different responses to predation risks and competition in different seasons according to the demand for food resources.

Nighttime Ecology: The "Nocturnal Problem" Revisited

The existence of a synthetic program of research on what was then termed the "nocturnal problem" and that we might now call "nighttime ecology" was declared more than 70 years ago. In reality, this failed to materialize, arguably as a consequence of practical challenges in studying organisms at night and instead concentrating on the existence of circadian rhythms, the mechanisms that give rise to them, and their consequences. This legacy is evident to this day, with consideration of the ecology of the nighttime markedly underrepresented in ecological research and literature. However, several factors suggest that it would be timely to revive the vision of a comprehensive research program in nighttime ecology. These include (i) that the study of the ecology of the night is being revolutionized by new and improved technologies; (ii) suggestions that, far from being a minor component of biodiversity, a high proportion of animal species are active at night; (iii) that fundamental questions about differences and connections between the ecology of the daytime and the nighttime remain largely unanswered; and (iv) that the nighttime environment is coming under severe anthropogenic pressure. In this article, I seek to reestablish nighttime ecology as a synthetic program of research, highlighting key focal topics and questions and providing an overview of the current state of understanding and developments.

Lunar and temperature effects on activity of free-living desert hamsters (Phodopus roborovskii, Satunin 1903)

Time management of truly wild hamsters was investigated in their natural habitat in Alashan desert, Inner Mongolia, China during summer of 2009, 2010, and 2012. Duration of activity outside their burrows, duration of foraging walks, and nocturnal inside stays were analyzed with the aim to elucidate impact of moon, ambient, and soil temperature. Animal data were determined using radio frequency identification (RFID) technique; for that purpose, individuals were caught in the field and marked with passive transponders. Their burrows were equipped with integrated microchip readers and photosensors for the detection of movements into or out of the burrow. Lunar impact was analyzed based on moon phase (full, waning, new, and waxing moons) and moon disk size. A prolongation of aboveground activity was shown with increasing moon disk size (Spearman ρ = 0.237; p = 0.025) which was caused by earlier onsets (p =-0.161; p = 0.048); additionally, foraging walks took longer (Pearson r = 0.037; p = 0.037). Temperature of different periods of time was analyzed, i.e., mean of whole day, of the activity phase, minimum, and maximum. Moreover, this was done for the current day and the previous 3 days. Overall, increasing ambient and soil temperatures were associated with shortening of activity by earlier offsets of activity and shorter nocturnal stays inside their burrows. Most influential temperatures for activity duration were the maximum ambient temperature, 3 days before (stepwise regression analysis R = 0.499; R² = 0.249; F = 7.281; p = 0.013) and soil temperature during activity phase, 1 day before (R = 0.644; R² = 0.283; F = 7.458; p = 0.004).

Oestrus cycle of the Desert hamster (Phodopus roborovskii, Satunin, 1903)

The Desert hamster, Phodopus roborovskii, is one of the lesser-known laboratory animal models and therefore knowledge of its reproductive system and physiology is limited. This study investigated the time course of vaginal and behavioural oestrus cycles by means of vaginal smear cytology, serum luteinizing hormone (LH) levels, wheel-running activity patterns, and pairing tests. The oestrus cycle lasts between four and six days and follows a pattern rather similar to that described for other rodent species. An important finding of this study is the existence of a fifth cycle stage between pre-oestrus and oestrus, the so-called early oestrus. Early oestrus differs from pre-oestrus by a complete lack of leucocytes in the vaginal cytology and a dramatic increase of serum LH levels just before activity onset. The early oestrus stage lasts 4-6 h, but was not observed in every female. When present it affects the length of the whole oestrus cycle. With early oestrus the pre-oestrus stage lasts only 14-18 h and the total length of the oestrus cycle length is four days. Without early oestrus, the pre-oestrus is prolonged to 18-36 h and the oestrus cycle length varies between four and six days. Desert hamsters showed only subtle oestrus-correlated changes in wheel-running activity, i.e. they failed to show the characteristic scalloping of activity onset, but showed prolonged activity during early oestrus. Pairing tests revealed characteristic changes in the relative frequencies of socio-positive, neutral, aggressive and sexual behaviour during the course of the oestrus cycle, with an elevated level of sexual behaviour during oestrus.