Search

Individuals colonizing new areas at expanding ranges encounter numerous and unpredictable stressors. Exposure to unfamiliar environments suggests that colonists would differ in stress levels from residents living in familiar conditions. Few empirical studies tested this hypothesis and produced mixed results, and the role of stress regulation in colonization remains unclear. Studies relating stress levels to colonization mainly use a geographical analysis comparing established colonist populations with source populations. We used faecal glucocorticoid metabolites (FGMs) to assess both spatial and temporal dynamics of stress levels in an expanding population of midday gerbils (Meriones meridianus). We demonstrated that adult males and females had higher FGM levels in newly emerged colonies, compared with the source population, but differed in the pattern of FGM dynamics post-foundation. In males, FGM levels sharply decreased in the second year after colony establishment. In females, FGM levels did not change with time and remained high despite the decreasing environmental unpredictability, exhibiting among-individual variation. Increased stress levels of colonist males damping with time post-colonization suggest they are flexible in responding to immediate changes in environmental uncertainty. On the contrary, high and stable over generations stress levels uncoupled from the changes in the environmental uncertainty in female colonists imply that they carry a relatively constant phenotype associated with the reactive coping strategy favouring colonization. We link sex differences in consistency and plasticity in stress regulation during colonization to the sex-specific life-history strategies. [ABSTRACT FROM AUTHOR]

In a study of gerbils with contrasting social and mating systems (group-living monogamous Mongolian gerbil Meriones unguiculatus , solitary nonterritorial promiscuous midday jird M. meridianus , and solitary territorial promiscuous pale gerbil Gerbillus perpallidus), we employed partner preference tests (PPTs) to assess among-species variation in sociability and pair-bonding patterns and tested whether the nature of contact between individuals: direct contact (DC) versus nondirect contact (NDC) affected our results. We measured male preferences as the time: 1) spent alone, 2) with familiar (partner), and 3) unfamiliar (stranger) female in the 3-chambered apparatus. Gerbil species differed strongly in sociability and male partner preferences. The time spent alone was a reliable indicator of species sociability independent of the nature of contact, whereas the pattern and level of between-species differences in male partner preferences depended on contact type: DC PPTs, unlike NDC-tests, discriminated well between monogamous and promiscuous species. In the DC-tests, stranger-directed aggression and stranger avoidance were observed both in the highly social monogamous M. unguiculatus and the solitary territorial promiscuous G. perpallidus , but not in the nonterritorial promiscuous M. meridianus. In M. unguiculatus , stranger avoidance in the DC-tests increased the time spent with the partner, thus providing evidence of a partner preference that was not found in the NDC-tests, whereas in G. perpallidus , stranger avoidance increased the time spent alone. This first comparative experimental study of partner preferences in gerbils provides new insights into the interspecific variation in gerbil sociality and mating systems and sheds light on behavioral mechanisms underlying social fidelity and pair-bonding. [ABSTRACT FROM AUTHOR]

We aimed to investigate whether two closely related but socially distinct species of gerbils differ in personality patterns. Using a suit of multivariate repeated assays (docility test, dark-light emergence test, startle test, novel object test, elevated platform test, and stranger test), we assessed contextual and temporal consistency of docility, boldness, exploration, anxiety, and sociability in the solitary midday gerbil, Meriones meridianus, and social Mongolian gerbil, M. unguiculatus. We revealed contextually consistent and highly repeatable sex-independent but species-specific personality traits. Species differed in temporal repeatability of different behaviours, and contextual consistency was more pronounced in solitary M. meridianus than in social M. unguiculatus. This finding contradicts the social niche specialization hypothesis, which suggests that personality traits should be more consistent in more social species. Instead, we hypothesize that social complexity should favour more flexible and less consistent behavioural traits. The habituation effect indicative of learning abilities was weak in both species yet stronger in social M. unguiculatus, supporting the relationship between the sociality level and cognitive skills. In both species, only a few different behavioural traits covaried, and the sets of correlated behaviours were species-specific such that the two species did not share any pair of correlated traits. Between-species differences in personality traits, habituation, and behavioural syndromes may be linked to differences in sociality. The lack of prominent behavioural syndromes is consistent with the idea that context-specific individual behavioural traits might be favoured to allow more flexible and adequate responses to changing environments than syndromes of correlated functionally different behaviours. [ABSTRACT FROM AUTHOR]

Hibernating mammals have annual cycles with strict timing of all processes including reproduction, yet female reproductive physiology is only poorly studied in such species. We investigated the estrous cycle in yellow ground squirrels (Spermophilus fulvus), which hibernate up to 9 months. Using vaginal cytology and serum progesterone and estradiol profiles, we identified proestrus, estrus, metestrus, and anestrus in the cycle. As in other rodents, predominance of cornified cells marked estrus, and an increase in the leukocyte number reflected metestrus. The only estrus in a year started, and then, pregnancy occurred mostly within 3 days after spring emergence. In one female, we noticed a copulatory plug for the first time for this species. The progesterone level increased from proestrus/estrus to pregnancy and decreased in the postlactation period. Estradiol concentration did not change significantly throughout the estrous cycle but varied among females and was consistently high in some of them. The hormone levels did not vary with female age despite smaller body size in yearling females than in older ones. During postlactation, progesterone concentration diminished toward hibernation, and we could not detect signs of prehibernation activation of the female reproductive system. Probably, gonadal preparation in S. fulvus females proceeds at periodic arousals during hibernation. Our data showed fast transitions between phases of the female estrous cycle and early maturation of juvenile females, consistently with the hypothesis of the fast life-history strategy of S. fulvus. [ABSTRACT FROM AUTHOR]

The speckled ground squirrel, Spermophilus suslicus (Güldenstead, 1770) was formerly a widely distributed species in eastern Europe, and it was even considered a pest species. The distribution range of the speckled ground squirrel is now fragmented, most of its settlements are small and separated from each other. This tendency is observed over most of the species' range. At present, the speckled ground squirrel usually inhabits areas difficult to plough, hills, gullies and lows, often situated on the banks of different water management facilities. Last significant decrease of the species' numbers occurred at the end of the 20th century. However, in recent years a slight tendency to population increase has been observed in some regions. The main causes of the decline are climatic factors -- cold end little-snow winters, spring and summer droughts, or increase of humidity. Further threats are changes in land use and habitat fragmentation that, together with applicatication of pesticides and other toxic chemicals, lead to isolation and decrease in the number of settlements. The current state of the speckled ground squirrel can be characterised as unsatisfactory and unstable. To be preserved, this species undoubtedly needs special conservation actions. [ABSTRACT FROM AUTHOR]

Alarm calls of ground squirrels are innate signals, showing substantial geographical variation across populations without the masking effects of sex and age- related variation. This makes them a convenient model for studying population genetic effects on the evolution of alarm communication. We compared data on the alarm call structure and the mitochondrial DNA (mtDNA) complete control region (C-region) (998–1002 bp) polymorphism in the same 90 individual speckled ground squirrels ( Spermophilus suslicus ) across 6 populations (15 individuals per population), separated by distances from 12 to 1274 km. We calculated acoustic distances between each pair of populations based on acoustic variables of alarm calls, averaged for each individual using Euclidean distances of population centroids, in the space of canonical axes of discriminant function analysis. Genetic distances ranged of 0–1.1% within populations and of 0.5–4.9% between populations. Prominent differences were found between eastern and western populations separated by the Dnieper River. Both genetic and acoustic distances showed a significant positive correlation with geographical among populations. Positive correlation between acoustic and genetic distances did not reach significance. These results support effects of ecological selection on the alarm call variables rather than the genetic drift hypothesis. In addition, these results support the current taxonomic separation between subspecies of speckled ground squirrels differing in diploid chromosome sets 2 n = 34 ( Spermophilus suslicus guttatus ) and 2 n = 36 ( Spermophilus suslicus odessanus ). [ABSTRACT FROM AUTHOR]