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Small rodents are a key indicator to understand the effect of rapidly changing winter climate on Arctic tundra ecosystems. However, monitoring rodent populations through the long Arctic winter by means of conventional traps has, until now, been hampered by snow cover and harsh ambient conditions. Here, we conduct the first extensive assessment of the utility of a newly developed camera trap to study the winter dynamics of small mammals in the Low Arctic tundra of northern Norway. Forty functional cameras were motion-triggered 20 172 times between September 2014 and July 2015, mainly by grey-sided voles (Myodes rufocanus (Sundevall, 1846)), tundra voles (Microtus oeconomus (Pallas, 1776)), Norwegian lemmings (Lemmus lemmus (Linnaeus, 1758)) and shrews (Sorex spp.). These data proved to be suitable for dynamical modelling of species-specific site occupancy rates. The occupancy rates of all recorded species declined sharply and synchronously at the onset of the winter. This decline happened concurrently with changes in the ambient conditions recorded by time-lapse images of snow and water. Our study demonstrates the potential of subnivean camera traps for elucidating novel aspects of year-round dynamics of Arctic small mammal communities.

Phenacomys cf. intermedius, the heather vole, is known from three late Pleistocene and early Holocene localities on Vancouver Island, British Columbia, Canada, where they are absent today. This study reports the heather vole specimens from one of these sites, P2 Cave, and provides a human behavioural context for its presence and eventual extirpation as a consequence of changing environments. Heather vole is a cold-adapted rodent. The early Holocene thermal maximum and subsequent development of coastal western hemlock forests contributed to its Vancouver Island extinction without an apparent corresponding range restriction in higher elevation habitats as has been noted elsewhere in Western North America. Tendency for low population densities in closed-canopy forests, antisocial intraspecies behaviours, and limited immigration across fragmented habitats supported local extinction. The absence of heather vole in the modern environment elsewhere along the coasts of British Columbia, Southeast Alaska, and Washington is probably due to similar factors as are highlighted here. Toward environmental reconstruction and the archaeological setting this study suggests that humans are unlikely to have occupied the Vancouver Island area during a hiatus in the vertebrate faunal record including the cold-adapted heather vole from about 19 700 to 14 700 years ago when the Cordilleran Ice Sheet extended west to the continental shelf. Improved environmental conditions for humans occurred both before and after this time. It also suggests that the glacial conditions in which the heather vole occupied Vancouver Island diverge from the Holocene interglacial setting that has seen an expansion of a human presence and of the corresponding archaeological record. [ABSTRACT FROM AUTHOR]

Parasites can influence host population health and dynamics and are often an overlooked aspect of the ecology of ecosystems. Understanding the impacts of ecological interactions between parasites and small mammals can provide insights into ecosystem dynamics. We live trapped small mammals within the Apostle Islands archipelago (2017–2020) and assessed factors influencing the presence of mites from the Trombiculidae family. Archipelagos provide unique research opportunities because in small mammal–parasitic trombiculid systems, they are essentially closed systems. We detected trombiculids on 47% of red-backed vole (Myodes gapperi (Vigors, 1830)) individuals but rarely detected trombiculids on other species. We developed and ranked a set of a priori logistic regression models of trombiculid presence relative to habitat quality, host abundance, body condition, sex, and sexual maturity to identify factors significant in predicting trombiculid infection for M. gapperi. Parasitic trombiculids were more likely when M. gapperi abundance was high and body condition was poor; however, it is unknown whether trombiculids affect condition or if trombiculids are more likely to parasitize hosts in poor condition. The significance of host abundance may indicate density-dependent transmission. Our work suggests that host density and body condition are important factors influencing parasitism by trombiculids in M. gapperi populations. [ABSTRACT FROM AUTHOR]

Gallic acid (GA), a phenol that is present in various plants, potentially contains antioxidant properties. This study aimed to investigate the effects of GA on the reproduction of adolescent male Brandt's voles (Lasiopodomys brandtii (Radde, 1861)). Antioxidant levels and apoptosis in the testis, as well as reproductive physiology, were evaluated in adolescent males treated with GA. The results showed that a low dose of GA enhanced relative epididymis mass and the sperm density in the epididymis, increased the mRNA levels of steroidogenic acute regulatory protein in the testis, and reduced the percentages of abnormal and dead sperm. In addition, a low dose of GA significantly increased the levels of superoxide dismutase, catalase, and glutathione peroxidase, and decreased the level of malondialdehyde in the testis, as well as the mRNA and protein levels of the apoptosis-related gene, caspase-3. However, a high dose of GA sharply reduced the mean diameter of the seminiferous tubules compared with a low dose. Collectively, these findings demonstrate that GA treatment during puberty affects the reproductive responses of male Brandt's voles in a dose-dependent manner by regulating antioxidant levels and apoptosis. [ABSTRACT FROM AUTHOR]

The growing rate of resource extraction forces increasing numbers of late-seral species to occupy habitats that are in early stages of succession. Sustainable management must maintain habitat features that are required for recovery of these species, which may be challenging because their response to those features can vary following nonsystematic trends during stages of succession. We investigated whether simple movement rules could explain such variations by assessing how movements of a late-seral species, the red-backed vole (Myodes gapperi (Vigors, 1830)), vary during postlogging forest succession using the spool and line technique in recent cuts, mid-successional forests, and old-growth forests. We found that voles moved selectively along coarse woody material (CWM), and this selection was weaker in mid-successional forests. This change was best explained by a simple functional response, whereby voles selected CWM more strongly in stands where canopy cover availability was moderately high. Likewise, voles more rapidly left patches that had high canopy cover when it was less available in stands and tended to spend more time in patches with high CWM volumes. Our study demonstrates that the highly dynamic nature of animal–habitat relationships observed during forest succession can be summarized by a few simple functional responses in movement and habitat selection. [ABSTRACT FROM AUTHOR]

Home range is shaped by an individual's interactions with the environment and conspecifics, and both size and placement may vary in response to population fluctuations. The method used to collect locational data may also affect home-range estimates. We examined the effect of density, sex, and field method on home range of southern red-backed voles (Myodes gapperi (Vigors, 1830)) inhabiting eastern hemlock (Tsuga canadensis (L.) Carrière) forests. Twelve mark–recapture grids were used to census M. gapperi from 2014 to 2017. In 2017, individuals were radio-collared. Home-range size, core-area size, and shared space were calculated using kernel density estimators from both mark–recapture and radiotelemetry data. Density effects on home range and core area were analyzed and differences between sex and field method were compared. We found (i) density did not affect home-range size, (ii) male home range was larger than female home range, (iii) females shared space more frequently and to a greater extent with males than other females, and (iv) home-range estimates were not significantly different between mark–recapture and radiotelemetry. Male home range, however, was larger under radiotelemetry and may reflect a truncation effect when mark–recapture grid size is smaller than male home range. [ABSTRACT FROM AUTHOR]

Competing species and predators can alter the habitat use of animals, but both factors are rarely simultaneously controlled. We studied in experimental enclosures how closely related species, the sibling vole ( Microtus levis Miller, 1908) and the field vole ( Microtus agrestis (Linnaeus, 1761)), adjust their habitat use when facing either the competing species or simultaneously competition and predation risk. The species responded differently in their proportional use of two habitat types, a low cover (productive but riskier) and a high cover (safer but poorer). When alone, field voles used the low-cover habitat according to availability at low densities, but decreased its use with increasing density. Sibling voles, however, avoided the low-cover habitat in single-species populations. Under interspecific competition, the habitat-use patterns switched between species: sibling voles used the low-cover habitat according to availability, with decreasing use as densities increased. Sibling voles responded to predation risk by showing a stronger density-dependent decrease in the use of low-cover habitat. Field voles, initially using mostly high cover, did not change behaviour under risk of predation. Our results highlight the importance of considering both predation risk and interspecific competition when interpreting patterns of habitat selection among coexisting species. [ABSTRACT FROM AUTHOR]

Mole voles are the most specialized subterranean members of the subfamily Arvicolinae. We assess the basic reproductive parameters of the Zaisan mole vole ( Ellobius tancrei Blasius, 1884) and compare our data with the characteristics reported for other Ellobius species and surface-dwelling voles. In most respects, reproduction of the E. tancrei follows the pattern that is typical for voles. Females undergo postpartum estrus, but rarely combine pregnancy with lactation. The rate of embryonic and postembryonic growth (0.13 and 0.54 g/day, respectively) are slightly lower, whereas the relative neonate and weanling masses (8% and 40% of maternal mass, respectively) are slightly higher than the respective values predicted for non-subterranean arvicolines. The combination of these trends results in the protracted pregnancy and lactation (both ∼30 days). The age at first breeding is delayed (>2.5 months). Despite heavy weanlings, total maternal investment per litter in E. tancrei is low due to small litter size (2.31). Although the species of Ellobius are similar to each other by the parameters of developmental time, they vary by litter size, total investment per litter, and possibly by relative neonate body mass. This is consistent with the idea that when body-size effect is removed, fecundity variables and degree of precociality at birth are dissociated from timing variables. [ABSTRACT FROM AUTHOR]

Understanding the success of habitat generalist species requires knowledge of how individuals respond to stressors that vary across habitats within landscapes. Habitat structure can affect stress by altering predation risk, conspecific densities, and densities of heterospecific competitors. Increased demand for biofuels will alter habitat structure for species in agroecosystems worldwide. We measured stress responses of deer mice ( Peromyscus maniculatus (Wagner, 1845)), a widespread habitat generalist, in a biofuels landscape. We quantified fecal corticosterone concentrations for individuals in four biofuel crops: switchgrass ( Panicum virgatum L.), miscanthus ( Miscanthus × giganteus Greef & Deuter ex Hodkinson & Renvoize), mixed prairie, and corn ( Zea mays L.). We also evaluated stress responses of deer mice to the annual harvesting of corn. Deer mice inhabiting switchgrass and mixed prairie had higher fecal corticosterone concentrations compared with mice in corn and miscanthus. Fecal corticosterone concentrations correlated positively with abundances of conspecifics and behaviorally dominant voles (prairie vole, Microtus ochrogaster (Wagner, 1842); meadow vole, Microtus pennsylvanicus (Ord, 1815)) across habitats. Stress levels of deer mice depended on how habitat structure modified the competitive environment. Deer mice did not exhibit increased fecal corticosterone concentrations in response to corn harvest, a rapid and extensive habitat disturbance common to agroecosystems. Our research is the first to investigate how landscape change due to biofuels expansion can affect stress levels of individuals. [ABSTRACT FROM AUTHOR]

Research on mammals and birds has shown that predation may have indirect effects on prey reproduction. Some of the indirect effects may give prey an adaptive advantage. Females of several vole species respond to the presence of predators from the genus Mustela L., 1758 with suppressed breeding; this response increases females' chances of survival. However, breeding suppression is observed only in a certain part of the female population; it is unclear whether predation risk affects the remaining females. We investigated this in a capture-mark-recapture experiment on reproductive effort of female common voles ( Microtus arvalis (Pallas, 1778)) facing simulated presence of mustelid predators. We measured two parameters: the number of recruits per litter and the litter interval. Compared with control populations, the number of recruits per litter was not affected, but the litter interval was longer in females facing mustelid risk of predation. This indicates that predation risk affects females in a more complex way than originally proposed: it induces breeding suppression in some, but also influences litter frequency in others. Our result suggests that predatory stress deregulates the estrous cycle. Decreased frequency of litters can be a viable antipredatory adaptation in iteroparous organisms. [ABSTRACT FROM AUTHOR]

The Lusitanian pine vole (Microtus lusitanicus (Gerbe, 1879)) and the Mediterranean pine vole (Microtus duodecimcostatus de Selys-Longchamps, 1839) are sister species with burrowing habits and a restricted European distribution. Our aim was to assess the relative effect of environmental, soil, and spatial characteristics on the distribution of these species in Portugal, and obtain predicted occurrence maps for each species, particularly to identify areas of sympatry. We used spatial eigenvector mapping (SEVM) to describe the spatial autocorrelation in species data, and we partitioned the variance in species distributions to quantify the relative effects of environmental, soil, and spatial characteristics. The spatial variables explained the major part of variability in both species distributions and were more important than environmental or soil variables. The Lusitanian pine vole occurs in areas outside landscape units of grassland, higher rainfall, frost, and cambisols, with mostly acid soils, lower abundance of litosols, and presence of solonshaks. The Mediterranean pine vole is distributed in grassland areas within intermediate values of soil pH, dominated by litosols and luvisols, and lower rainfall, frost, and cambisols. Our results showed disjunct sympatric areas of small size and a parapatry boundary for the centre of Portugal, suggesting that contact zones are probably narrow. [ABSTRACT FROM AUTHOR]

The preferences of the deer mouse (Peromyscus maniculatus (Wagner, 1845)), southern red-backed vole (Myodes gapperi (Vigors, 1830)), heather vole (Phenacomys intermedius Merriam, 1889), long-tailed vole (Microtus longicaudus (Merriam, 1888)), and meadow vole (Microtus pennsylvanicus (Ord, 1851)) for lodgepole pine (Pinus contorta Dougl. ex Loud.), white spruce (Picea glauca (Moench.) Voss), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) seeds were investigated using cafeteria-style feeding experiments. Seed selection by P. maniculatus and M. gapperi in the field was also studied. Peromyscus maniculatus, M. gapperi, M. longicaudus, and M. pennsylvanicus showed a distinct preference for lodgepole pine seeds and avoidance of subalpine fir seeds, and consumed the different species of seeds in similar relative proportions. Phenacomys intermedius behaved very differently from the other rodent species in that it did not show a preference among seed species, and consumed very few seeds in total. Findings from the field seed selection trials were consistent with laboratory results. We suggest that postdispersal seed predation by small mammals could limit the recruitment success of lodgepole pine and white spruce, but would not be a major problem in the regeneration of subalpine fir stands. This could provide an advantage for subalpine fir over neighbouring competitive species. [ABSTRACT FROM AUTHOR]

High-latitude arvicoline rodents usually reproduce in warmer months, but winter breeding has been documented in several species, including the northern red-backed vole (Myodes rutilus (Pallas, 1779) Wilson and Reader, 2005; formerly Clethrionomys rutilus (Pallas, 1779)). We tested whether the reproductive condition of the species is linked to changes in environmental parameters or its body condition, and we tested the frequencies at which different reproductive phenotypes are exhibited under field and laboratory conditions. Free-living voles in south-central Alaska reached peak reproductive organ masses in spring (females) and early summer (males). Between-subject comparisons showed an effect of body mass, photoperiod, percent fat, temperature, and snow depth on reproductive organ masses, depending on the sex and breeding period (p < 0.05). One instance of late-summer photoperiod nonresponsiveness was observed, but we detected no winter breeding. Captive male voles given food ad libitum and housed at room temperature exhibited strong phenotypic variation in testis mass in response to short photoperiods. The percentage of nonresponders was 28.2% and was within the known range of nonresponsiveness for lower latitude species (20%-40%). Thus, photoperiod nonresponsive morphs are conserved in at least one arctic and subarctic species at frequencies comparable to lower latitude voles despite no observance of winter breeding in the field. Voles exhibit reproductive elasticity and may breed in winter if environmental conditions enable them. Les rongeurs arvicolinés des hautes latitudes se reproduisent généralement durant les mois plus chauds, mais on a signalé des cas de reproduction hivernale chez plusieurs espèces, en particulier chez le campagnol boréal (Myodes rutilus (Pallas, 1779) Wilson and Reeder, 2005; antérieurement Clethrionomys rutilus (Pallas, 1779)). Vous avons testé si la condition reproductive chez cette espèce est reliée aux changements des variables environnementales ou à sa condition corporelle et avons vérifié les fréquences auxquelles les divers phénotypes reproductifs se présentent dans des conditions de terrain et de laboratoire. Chez les campagnols libres en nature dans le centre-sud de l’Alaska, la masse des organes reproducteurs atteint son maximum au printemps (femelles) et au début de l’été (mâles). Des comparaisons entre individus révèlent un effet de la masse corporelle, de la photopériode, du pourcentage de graisses, de la température et de la profondeur de la neige sur la masse des organes reproducteurs en fonction du sexe et de la période de reproduction (p < 0,05). Nous avons observé un cas d’absence de réaction à la photopériode en fin d’été, mais détecté aucune reproduction hivernale. Des campagnols mâles en captivité, nourris ad libitum et maintenus à la température de la pièce, montrent une importante variation phénotypique dans leur masse testiculaire en réaction aux photopériodes courtes. Le pourcentage d’individus sans réaction était de 28,2 %, ce qui est dans la gamme connue d’absence de réaction chez les espèces de latitudes plus basses (20 % - 40 %). Ainsi, les formes qui ne réagissent pas à la photopériode sont conservées chez au moins une espèce arctique et subarctique à des fréquences comparables à celles trouvées chez les campagnols de latitudes plus basses, même si aucune reproduction hivernale n’a été observée en nature. Les campagnols possèdent une plasticité reproductrice et peuvent se reproduire en hiver si les conditions du milieu le permettent. [ABSTRACT FROM AUTHOR]

In this paper we explore the cyclic interactions of prey-predator systems by examining the relationship between cycle lengths of both species and the strength of their interaction. As a probe of interaction strength, we use the degree of counter-clockwise rotation in phase plots with the prey on the x axis and the predator on the y axis. We compare the results from a 25-year time series from the Hudson’s Bay Company data on American mink (Neovison vison (Schreber, 1777)) and muskrat (Ondatra zibethicus (L., 1766)) with results from three simulation models. We found that the strength of interaction (rotation range: -0.4 to 1.1 rad/year) was strongest when the two cycle lengths were similar and that it increased with the amplitude of the cycles (cycle range: 4-10 years). The time difference between prey and predator cycles that corresponded to the highest interaction strength was 2-3 years. Similar results were obtained with simulation models; the most complex Hanski model showing the overall best fit with observations. However, none of the models were able to reproduce long ranges of stable cycles by only changing one of their parameters at a time (ranges 2-4 years), whereas the observed range of stable cycles was 4-10 years. Nous examinons dans notre recherche les interactions cycliques des cycles proies-prédateurs par l’étude de la relation entre les longueurs des cycles des deux espèces et l’intensité de leur interaction. Comme mesure de l’intensité de l’interaction, nous utilisons le degré de rotation dans le sens inverse des aiguilles d’une montre dans des diagrammes de phase sur lesquels les prédateurs sont placés en abscisse et les prédateurs en ordonnée. Nous comparons les résultats d’une série chronologique de 25 ans de données de la Compagnie de la baie d’Hudson sur les visons (Neovison vison (Schreber, 1777)) et les rats musqués (Ondatra zibethicus (L., 1766)) avec les résultats de trois modèles de simulation. L’intensité de l’interaction (étendue de la rotation : -0,4 à 1,1 rad/année) est la plus grande quand les deux longueurs de cycles sont semblables et elle augmente en fonction de l’amplitude des cycles (étendue des cycles : 4-10 ans). Les différences temporelles entre les cycles de la proie et du prédateur qui correspondent à l’intensité d’interaction la plus grande sont de 2 à 3 ans. Les modèles de simulation produisent des résultats semblables et le modèle de Hanski le plus complexe présente le meilleur ajustement aux observations. Cependant, aucun des modèles n’est capable de reproduire des cycles stables à long terme par le changement successif des variables une seule à la fois (étendues 2-4 ans), alors que l’étendue observée des cycles stables est de 4 à 10 ans. [ABSTRACT FROM AUTHOR]

In this study of 35 years of data, we examine the short-term (cyclic) and long-term relationship between breeding success of great grey owls (Strix nebulosa Forster, 1772) and their food supply (bank voles (Clethrionomys glareolus (Schreber, 1780)), grey-sided voles (Clethrionomys rufocanus (Sundevall, 1846)), and field voles (Microtus agrestis (L., 1761))) in northern Sweden. Annual number of owl nests showed a 3 year cyclicity, which as predicted, corresponded to the length of the vole cycle in the region. Mean annual brood size also fluctuated and was positively dependent on the vole supply during the same spring. In this region, there has also been a decline in vole numbers in recent decades, from high-amplitude cycles in the 1970s to subsequent low-amplitude cycles. Correspondingly, and as predicted, mean annual brood size of the owls also declined, although only during the third years of the vole cycle when vole supply in spring and brood size of the owls is at its highest level in high-amplitude cycles. We predict that in the long run the vole decline, associated with increasingly milder winters, and the reduction of the brood size of the owls, especially in years of high owl breeding success, will have serious implications for the population of great grey owls in Scandinavia. L’examen de données sur 35 ans, nous sert à examiner les relations à court (cycliques) et à long termes entre le succès de la reproduction des chouettes lapones (Strix nebulosa Forster, 1772) et leur source de nourriture (les campagnols roussâtres (Clethrionomys glareolus (Schreber, 1780)), les campagnols gris-roux (Clethrionomys rufocanus (Sundevall, 1846)) et les campagnols des champs (Microtus agrestis (L., 1761))) dans le nord de la Suède. Il existe un cycle de 3 ans dans le nombre annuel de nids de chouettes, ce qui correspond, comme prédit, à la période du cycle des campagnols de la région. Il y a aussi une fluctuation de la taille des couvées qui est en corrélation positive avec l’approvisionnement en campagnols durant le printemps correspondant. Dans cette région, il y aussi eu un déclin des nombres de campagnols au cours des dernières décennies, depuis les cycles de forte amplitude des années 1970 jusqu’aux cycles subséquents de faible amplitude. Comme prédit, il y a aussi eu un déclin correspondant de la taille annuelle moyenne des couvées des chouettes, mais seulement durant la troisième année des cycles des campagnols, lorsque la présence de campagnols au printemps et la taille des couvées atteignent leur maximum dans les cycles de forte amplitude. Nous prédisons qu’à long terme le déclin des campagnols, associé aux hivers de plus en plus doux, et la diminution de la taille des couvées des chouettes, particulièrement les années de fort succès reproductif des chouettes, vont avoir d’importantes conséquences sur les populations de chouettes lapones en Scandinavie. [ABSTRACT FROM AUTHOR]

Many small mammals consume lichen and fungi, but southern red-backed voles (Clethrionomys gapperi (Vigors, 1830)) and northern flying squirrels (Glaucomys sabrinus (Shaw, 1801)) exhibit strong mycophagy compared with other North American taxa. We analyzed nutrient content of lichen and fungi and observed feeding preferences of voles and flying squirrels to understand the foraging behavior of these mammals and their strategy for surviving on relatively low-quality diets dominated by lichen and fungi. We analyzed nutrient characteristics of 10 hypogeous (fruiting belowground) fungi and four arboreal lichens eaten by red-backed voles and northern flying squirrels in the Rocky Mountains. Hypogeous fungi contained higher nitrogen, lipid, neutral detergent fiber, acid detergent fiber, ash, potassium, and phosphorous concentrations than arboreal lichens, but lichens were higher in calcium. To assess diet preferences, 10 pairwise feeding trials using four hypogeous fungi and two arboreal lichens were conducted with voles and seven trials using three hypogeous fungi and two lichens were conducted with squirrels. In general, squirrels and voles preferred hypogeous fungi over arboreal lichens. We then calculated dry matter and nitrogen digestibilities for flying squirrels and red-backed voles fed diets of arboreal lichen and hypogeous fungi. Overall mean dry matter digestibilities were >=70% for all diets. For hypogeous fungi, nitrogen digestibility was 12.3% and 24.9% for squirrels and voles, respectively, suggesting that most nitrogen was indigestible. Animals maintained positive nitrogen balance when fed fungi but were unable to maintain positive nitrogen balance when fed lichens. Maintenance nitrogen requirements for flying squirrels were lower than predicted. Low requirements may allow for increased consumption of lichen in winter, but lichen diets must be supplemented with a source of nitrogen because animals were unable to maintain nitrogen balance when fed lichen alone. Consumption of numerous fungi and lichen taxa is necessary to sustain these animals year-round. De nombreux petits mammifères consomment des lichens et des champignons, mais les campagnols à dos roux de Gapper (Clethrionomys gapperi (Vigors, 1830)) et les grands polatouches (Glaucomys sabrinus (Shaw, 1801)) font une importante mycophagie par comparaison aux autres taxons nord-américains. Nous avons analysé le contenu nutritif de lichens et de champignons et observé les préférences alimentaires de campagnols et de polatouches afin de comprendre le comportement de quête de nourriture de ces mammifères et leur stratégie pour survivre avec ces régimes alimentaires de relativement faible qualité dominés par les lichens et les champignons. Nous avons analysé les caractéristiques nutritives de 10 champignons hypogés (à fructification dans le sol) et de quatre lichens arboricoles mangés par les campagnols et les polatouches dans les Rocheuses. Les champignons hypogés contiennent de plus fortes concentrations d’azote, de lipides, de fibres détergentes, de fibres acides, de cendres, de potassium et de phosphore que les lichens arboricoles, mais les lichens sont plus riches en calcium. Afin de déterminer les préférences alimentaires, nous avons procédé à 10 essais alimentaires appariés impliquant quatre champignons hypogés et deux lichens arboricoles avec les campagnols et sept essais avec trois champignons hypogés et deux lichens avec les polatouches. En général, les polatouches et les campagnols préfèrent les champignons hypogés aux lichens arboricoles. Nous avons ensuite calculé la digestibilité de la matière sèche et de l’azote chez des polatouches et des campagnols nourris de régimes alimentaires de lichens arboricoles et de champignons hypogés. La digestibilité globale moyenne de la matière sèche est >=70 % pour tous les régimes. Pour ce qui est des champignons hypogés, la digestibilité de l’azote est respectivement de 12,3 % et de 24,9 % chez les polatouches et les campagnols, ce qui indique que la majorité de l’azote est indigestible. Les animaux gardent un bilan azoté positif avec un régime de champignons, mais sont incapables de le faire avec un régime de lichens. Les besoins de base en azote des polatouches sont moins élevés que ce que nous avions prédit. Ces faibles besoins peuvent permettre une consommation accrue de lichens en hiver, mais les régimes à base de lichens doivent être complétés avec une source d’azote, car les animaux sont incapables de maintenir leur bilan azoté lorsqu’ils se nourrissent de lichens seuls. La consommation de nombreux taxons de champignons et de lichens est nécessaire pour assu [ABSTRACT FROM AUTHOR]

Dissected colluvial sediments on a Peace River terrace at Bear Flat, northeast British Columbia enclosed a late Pleistocene micromammalian faunule. The fossil remains, including a few loosely articulated skulls and mandibles, were dominated by taiga voles (Microtus xanthognathus). The Bear Flat site constitutes the second fossil occurrence in the region of this elusive species, which is unknown in British Columbia in historic times. The late Pleistocene age, determined by accelerator mass spectrometry directly on taiga vole bone collagen, is consistent with the ages of widespread taiga vole records peripheral to the Laurentide ice sheet in western, mid-western, and eastern North America. The presence of allo-chronous remains within a comprehensively dated sedimentary sequence provides a cautionary note about straightforward acceptance of relative stratigraphic dating. Des sédiments colluviaux disséqués sur une terrasse de la rivière de la Paix, à Bear Flat, dans le nord-est de la Colombie-Britannique renfermaient une faunule micro-mammifère du Pléistocène tardif. Les restes fossiles, incluant quelques mandibules et crânes faiblement articulés, étaient dominés par des campagnols de la taïga (Microtus xanthognathus). Le site de Bear Flat constitue la seconde occurrence fossile de cette espèce problématique, laquelle est historiquement inconnue en Colombie-Britannique. L’âge Pléistocène tardif, déterminé par spectrométrie de masse par accélérateur directement sur le collagène des os de campagnols de la taïga, concorde avec les âges des nombreuses découvertes de campagnols de la taïga en bordure de l’Inlandsis laurentidien dans l’ouest, le centre-ouest et l’est de l’Amérique du Nord. La présence de restes allochrones à l’intérieur d’une séquence sédimentaire entièrement datée constitue une mise en garde contre l’acceptation pure et simple de la datation stratigraphique relative. [ABSTRACT FROM AUTHOR]

Habitat and patch use are crucial to the dynamics of populations and the structure of ecological communities. But ecologists have not rigorously tested whether animals choose habitat at small or large scales. If individuals base their patch and habitat choices on fine-scale differences in habitat, then their use of different sites should correspond with measures of microhabitat at those sites. But if individuals use density to assess and respond to habitat at larger spatial scales, then site use should correspond with the scale of density-dependent habitat selection. We tested these predictions with experiments that measured microhabitat and monitored the use of capture sites by meadow voles (Microtus pennsylvanicus Ord, 1815) in 0.25 ha old-field enclosures. We varied the density of voles in pairs of adjacent enclosures and tested for density-dependent habitat selection. Then we assessed whether their frequency of captures at trapping stations was best predicted at the small scale of microhabitat or at the much larger scale of enclosures where density varied. The voles selected habitat at different scales. When the use of enclosures was predicted by density, the scale of density-dependent choice trumped the use of small-scale patches. And when voles selected amongst different small-scale patches, their use of enclosures was independent of density. These results suggest that assessments of spatial scale in habitat use must include tests for both scale- and density-dependent habitat choice. [ABSTRACT FROM AUTHOR]

The hormonal stress response is adapted to deal with acute (short-term) stressors; however, chronic (long-term) stressors have negative effects on survival and fitness. Field and laboratory evidence suggest that voles respond behaviourally to predator odours. However, it is unknown whether voles mount an acute hormonal stress response to predator odour. We determined whether reproductively active, captive male meadow voles (Microtus pennsylvanicus (Ord, 1815)) mounted a more pronounced hormonal stress response to weasel odour (ermine, Mustela erminea L., 1758), one of their principal mammalian predators, than to nonpredator and control odours. We compared the corticosterone response of captive voles to weasel, jumping mouse (Zapus hudsonius (Zimmermann, 1780)), and control odours following acute (20 min) exposure. The hormonal stress response to the treatment odours did not differ, indicating that captive male voles in the reproductive season do not mount an acute stress response to predator odour. We hypothesize that voles do not respond to weasel odour because, independent of other stimuli, olfactory signals are not reliable enough to outweigh the costs, such as suppression of reproduction and reproductive behaviour, associated with a response. [ABSTRACT FROM AUTHOR]

Vole population sex ratio varies seasonally. However, population sex ratios have usually been estimated using naïve estimators that do not allow for biases owing to the sex difference in capture probabilities and movement distances (i.e., effective areas sampled). Here we aimed to advance the methodological approach, recognizing that there are two different classes of contributing mechanisms to the pattern which are best addressed separately: (1) those mechan isms imposing a systematic error (bias) in population estimates and (2) those generating the true process variation. Analyzing 7-year capture–recapture data in the common vole (Microtus arvalis (Pallas, 1778)), we quantified both types of biases and revealed that the bias owing to differential capture rates was often severe and less predictable, whereas that owing to differential effective areas was smaller and overestimated male numbers for most of the year. We demonstrated unambiguously that the unbiased population sex ratio indeed varies seasonally, with the males usually being more numerous over winter and spring. By testing predictions from two mechanistic hypotheses to explain the process variability, we found evidence for both the differential recruitment hypothesis and the differential survival hypothesis. From April–May to August, it was the females that were recruited more to the population and that had higher survival rates than males. We suggest that the seasonal variation in the population sex ratio is not merely a result of biasing mechanisms but an important population property driven by the joint effect of differential recruitment and differential survival between sexes. [ABSTRACT FROM AUTHOR]

Animals use day length (photoperiod) to time seasonal adaptations to annual changes in their environment. Reproductive adjustments in deer mice (Peromyscus maniculatus (Wagner, 1845)) from high latitudes are more extensive in response to short days than in deer mice from low latitudes. These adjustments may permit individuals to survive the severe seasonal changes (e.g., temperature and food abundance) in high-latitude environments. Immune function is also affected by photoperiod. Short days were predicted to result in elevated immune and reproductive responses in meadow voles (Microtus pennsylvanicus (Ord, 1815)) from the Northwest Territories (NWT), Canada (~62°N), compared with voles from Ohio (OH), USA (~39°N). Male voles from both latitudes were maintained in long or short days for 10 weeks prior to a delayed-type hypersensitivity (DTH) immune challenge. Both populations displayed similar testicular regression and reduction of testosterone concentrations in short days. DTH immune responses, however, diverged between the two populations. DTH immune responses were enhanced in long-day NWT voles and short-day OH voles, but decreased in short-day NWT voles and long-day OH voles. Total and free corticosterone concentrations did not explain the latitudinal differences in immune responses. These results suggest that photoperiod affects reproductive and immune systems differently and that immune responses may reflect other environmental factors. [ABSTRACT FROM AUTHOR]

Prairie voles (Microtus ochrogaster (Wagner, 1842)) exhibit behavioral, morphological, and neuroendocrinological traits associated with monogamy and are considered a model system to examine the biological foundations of monogamy in mammals. We examined allelic polymorphism at microsatellite loci to assess mating exclusivity in wild prairie voles sampled in east-central Illinois and found evidence of multiple paternity in five of nine litters (56%) analyzed. Thus, a female in this socially monogamous mammal with extensive mechanisms for pair bonding does not always mate solely with its partner and raises the paradox of why some pair-bonded females mate multiply. [ABSTRACT FROM AUTHOR]

Adaptive models predict that variation in the spacing of microtines during reproductive periods may reflect mating strategies linked to differences in habitat characteristics. Using spatial and morphological analyses, we aimed to assess the mating system adopted by a population of rock-dwelling snow voles, Chionomys nivalis (Martins, 1842), and its functional significance within high-mountain environments. Spacing data coincided with a pattern generally associated with promiscuous mating: males had largely overlapping home ranges, whereas female home ranges showed a very reduced or absent degree of overlap. In addition, ranges overlapped considerably between sexes. Males had significantly greater body mass than females, and the magnitude of this difference resembled more a promiscuous than a polygamous or monogamous species. Also, relative testis size of males was in the range reported for promiscuous voles. Our results fit the predictions made by food abundance and distribution optimality models, suggesting that mating strategies might be related to the habitat occupied by C. nivalis. In alpine rocky formations, vegetation is sparse and patchily distributed, and competing females could benefit from defending an exclusive territory. In turn, males might be unable to monopolize widely spaced females by defending exclusive territories, which may result in extensive overlap between their spatial ranges. [ABSTRACT FROM AUTHOR]

The hypothesis that high temporal variability of northern spotted owl (Strix occidentalis caurina) reproductive success is a response to prey abundance remains largely untested. We evaluated this relationship in the Oregon Cascade Mountains. Despite similar biomass of northern flying squirrels (Glaucomys sabrinus) (169 ± 13.9 g/ha) and deer mice (Peromyscus maniculatus) (160 ± 18.8 g/ha), flying squirrels dominated the breeding season diet based on both biomass (49%) and numbers (40%). Abundance of flying squirrels and western red-backed voles (Clethrionomys californicus) was more variable spatially (≥38% of process variation) than temporally (15%-24%), whereas abundance of deer mice was more similar across stands (12% spatial variation) than among years (68% temporal variation). Spotted owl reproductive success was statistically associated only with the abundance of deer mice (number of young per territory: r² = 0.68). However, deer mice comprised only 1.6 ± 0.5% of the biomass consumed. The low temporal variability of the dominant prey species provided evidence that simple prey relationship models were not likely to explain the highly synchronous and temporally dynamic patterns of spotted owl reproductive performance. Reproductive success was likely a result of the interaction of both weather and prey and the life history strategy of this long-lived owl. [ABSTRACT FROM AUTHOR]

The paper investigates effects of kin recognition on estrus and breeding in mandarin voles, microtus mandarinus, in the laboratory using a cross-fostering method. Nonsiblings reared apart produced significantly more litters than siblings or nonsiblings reared together. These results may support the hypothesis that familiarity through association before weaning, plays an important role in kin recognition. On the other hand, nonsiblings reared apart produced significantly more litters than siblings reared apart. These observations show that phenotype-matching mechanisms of kin recognition may operate in conjunction with familiarity in kin recognition in this species.

Population fluctuations may occur in synchrony among several rodent species at a given site, and they may occur in synchrony over large geographical areas. We summarize information on synchrony in lemmings and voles from the Canadian Arctic for the past 20 years. The most detailed available information is from the central Canadian Arctic, where snap-trap samples have been taken annually at several sites for periods of up to 15 years. Geographical synchrony in the same species among different sites was strong, especially for the central and eastern Canadian Arctic. Synchrony among different species at a given site was also generally high. When one species is at high density, densities of all species at that site tend to be high. These results do not easily fit the mobile-predator hypothesis proposed to explain regional synchrony, and are more consistent with the weather hypothesis, which we suggest both entrains synchrony among sites and enforces synchrony among species within a site. We tentatively support the weather hypothesis for geographical synchrony in lemmings, and recommend the establishment of a circumpolar program to monitor lemming cycles and predator movements that would advance our understanding of these large-scale patterns of cyclic synchrony. [ABSTRACT FROM AUTHOR]

Presents an experimental field study on the risk of parasite-induced predation in the case of Townsend's voles. Causes of mortality in rodents; Description of predation; Effect of predation on the overall survival rate of the animals.

Studies the microhabitat use in relation to microhabitat availability of a population of snow voles Chionomys nivalis, a nonhibernating microtine rodent inhabits in alpine biotopes. Influence of the nature of some adaptations among small mammals; Emphasis on the trade-off between biotic and abiotic factors; Determination of the regular use of rocky microhabitats.

Examines the effects of litter size on pup defense and weaning success of neighboring bank vole females. Increase of the defense intensity of bank vole females; Relationship between the dominance rank in mammals and their body mass; Accounts on the determinants of small-mammal breeding success.

Common voles (Microtus arvalis) use networks of runways around their burrows, which are dug in meadows. Their orientation among such networks could be based on rigid "egocentred" routes (possibly through the use of olfactory "trails") or on more general, "allocentred" spatial representations (with distant visual cues). In this 5-day study, male voles should reach food in the centre of a maze of three-way (Y) junctions offering similar local views but surrounded by distant visual cues. I tested whether the animals navigated using olfactory trails, implying one main direct foraging route, or allocentered representations, allowing flexibility among equivalent routes. Males quickly marked their environment, preferentially at the periphery, where they moved the most. However, during most direct trips between the nest and the food, they used one of the central shortest routes, which included the least scent-marked zones. Moreover, the voles preferred different shortest routes to go to the food and return from it, showing a bias in favour of the side where the distant goal (food or nest) was situated. This suggests that male common voles base their choices on the general direction of their goal rather than on trails. Finally, there was no major difference in initial exploration between a clean and a scent-marked maze.Les Campagnols des champs (Microtus arvalis) utilisent des réseaux de sentes autour de leurs terriers creusés dans des prairies. Leur orientation au sein de tels réseaux pourrait être basée sur des routes égocentrées rigides (éventuellement via des « pistes » olfactives) ou sur des représentations spatiales allocentrées plus générales (avec des repères visuels à distance). Dans cette étude de 5 jours, des campagnols mâles devaient atteindre leur nourriture au centre d'un labyrinthe de jonctions à trois voies (en Y), offrant des vues locales similaires mais entouré de repères visuels à distance. J'ai tenté de déterminer si les animaux allaient s'orienter selon des pistes olfactives, en suivant une route directe principale vers leur nourriture, ou selon une représentation allocentrée, permettant une flexibilité entre des routes équivalentes. Les mâles ont rapidement marqué leur environnement, particulièrement à la périphérie, où ils se déplaçaient le plus souvent. Toutefois, lors de la plupart des parcours directs entre leur nid et leur nourriture, ils ont emprunté l'un des chemins centraux les plus courts, là ou se trouvaient les zones les moins marquées. De plus, ils ont choisi, parmi les trajets les plus courts, des chemins différents pour aller à leur nourriture et pour en revenir, avec une préférence pour le côté de leur but lointain (nourriture ou nid). Cela semble indiquer que les campagnols des champs mâles basent leur choix sur la direction générale de leur but plutôt que sur des pistes. Enfin, il n'y a pas eu de différences majeures entre l'exploration d'un labyrinthe propre et celle d'un labyrinthe marqué d'odeurs. [ABSTRACT FROM AUTHOR]

Three pairs of the endangered Cabrera vole, Microtus cabrerae, which is endemic to the Iberian Peninsula, were captured in the wild and reared in captivity. They did not breed under standard laboratory conditions, and bred only under conditions similar to those found in wild colonies. Six litters were obtained and a total of 24 pups were monitored. Five external variables were measured and timing of 11 developmental events was recorded for each pup until it was 80 days old. Litter size was 4.0 ± 0.89 (mean ± SE; range = 3–5) pups per female, falling within the range reported for other Microtus species. Litter size of M. cabrerae was lower in the laboratory than in the field. Female body mass was correlated with litter mass at birth. Newborns were heavy (3.5 g, on average) compared with those of other Microtus species because of the relatively large size of adult M. cabrerae. Timing of the main developmental events followed a similar pattern to that observed for other species of the genus. Juvenile M. cabrerae grew fast in length during lactation, rapidly increasing their body mass during postweaning. Observations on parental behaviour in rearing pups support the previously published hypothesis that the species is monogamous. A global assessment of our results suggests that M. cabrerae should be included among the species that use the K strategy of reproduction.Trois couples de Campagnols de Cabrera, Microtus cabrerae, espèce menacée et endémique dans la Péninsule ibérique, ont été capturés en nature et élevés en captivité. Ces campagnols ne se sont pas reproduits dans l'environnement normal de laboratoire, mais seulement lorsque les conditions qui prévalent dans les colonies naturelles ont pu être simulées. Ils ont produit six portées et, au total, 24 petits ont été suivis. Cinq variables externes ont été mesurées et la chronologie de 11 étapes du développement a été notée pour chacun des individus jusqu'à l'âge de 80 jours. Le nombre moyen de petits par portée était de 4,0 ± 0,89 (moyenne ± écart type; étendue de 3 à 5) par femelle, ce qui correspond à ce qui prévaut chez d'autres espèces de Microtus. Les portées de M. cabrerae comptaient moins de petits en laboratoire qu'en nature. Il y avait une corrélation positive entre la masse des femelles et la masse des portées à la naissance. Les nouveau-nés étaient lourds (3,5 g en moyenne) comparativement à d'autres Microtus, à cause de la taille relativement grande des adultes. La chronologie des principales étapes du développement était la même que chez les autres espèces de Microtus. Les jeunes M. cabrerae subissaient une croissance en longueur rapide au cours de l'allaitement et une augmentation de masse au cours de la période suivante. L'observation du comportement des parents durant l'élevage des petits apporte des arguments en faveur de l'hypothèse de la monogamie de cette espèce, telle que publiée antérieurement. Une évaluation globale de nos résultats permet de croire que M. cabrerae fait partie des espèces qui utilisent la stratégie K au cours de leur reproduction.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The sources of sexually discriminable scent were identified for montane voles, Microtus montanus, and compared with known sources in other species of voles. I tested two different hypotheses. The data support the hypothesis that each vole species has a unique number and pattern of sources of sexually distinct scent. The location, pattern, and number of these sources of scent on the integument may allow individuals to convey particular types of information to conspecifics. The data also support the hypothesis that the greater the number of sources of scent for signaling opposite-sex conspecifics, the greater the number of encounters that individuals within that species have with opposite-sex conspecifics. The montane vole, a semisocial species, has six sources of scent, which is intermediate between the numbers found in the meadow vole (Microtus pennsylvanicus), an asocial species, and the prairie vole (Microtus ochrogaster), a social species. The results suggest that the number, pattern, and locations of sexually distinct scents are positively associated with the frequency with which individuals encounter the scent marks of neighboring conspecifics.Les points d'origine des odeurs sexuellement distinctives ont été identifiés chez le Campagnol montagnard, Microtus montanus, et comparés à ceux d'autres espèces de campagnols. Deux hypothèses ont été mises à l'épreuve. Les données corroborent l'hypothèse selon laquelle chaque espèce de campagnol possède un ensemble de sources d'odeurs sexuelles dont le nombre et la répartition lui sont particuliers. L'emplacement, la répartition et le nombre de ces sources d'odeur sur les téguments permettent aux individus de transmettre des informations particulières aux individus de la même espèce. Les données appuient aussi l'hypothèse selon laquelle plus un individu a de points d'odeur pour signaler sa présence aux individus conspécifiques du sexe opposé, plus il a de rencontres avec des individus de l'autre sexe. Chez le Campagnol montagnard, une espèce semi-sociale, il y a six sources d'odeurs, un nombre intermédiaire entre celui qui prévaut chez le Campagnol des champs (Microtus pennsylvanicus), une espèce asociale, et chez le Campagnol des Prairies (Microtus ochrogaster), une espèce sociale. Nos résultats indiquent que le nombre, la répartition et l'emplacement des sources d'odeurs sexuelles distinctes sont en corrélation positive avec la fréquence des contacts qu'un individu peut avoir avec les marques d'odeurs des individus conspécifiques avoisinants.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Body condition (energy reserves) can have important fitness consequences. Measuring condition of live animals is typically done by regressing body mass on measures of body size and using the residuals as an index of condition. The validity of this condition index was evaluated by determining whether it reflected measured fat content of five species of small mammals (yellow-pine chipmunks (Tamias amoenus Allen), bushy-tailed wood rats (Neotoma cinerea Ord), deer mice (Peromyscus maniculatus Ord), red-backed voles (Clethrionomys gapperi Vigors), and meadow voles (Microtus pennsylvanicus Ord)). We also determined whether body water could predict fat content, enabling the use of hydrogen-isotope dilution for estimating condition. For all five species, condition estimates weakly predicted fat content and more accurately predicted variation in lean dry mass and water content. The relationship between body water and fat content was inconsistent among the five species, discouraging against the general use of isotope dilution in these animals. Although ecologically important, these indices are best interpreted as explaining variation in all constituents of body composition.La condition physique (réserves énergétiques) peut avoir une influence importante sur le fitness. La mesure de la condition physique d'animaux vivants se fait généralement par une régression de la masse du corps en fonction de mesures de la taille du corps, les résidus servant de coefficient de condition. La validité de ce coefficient de condition a été évaluée en déterminant s'il reflète bien le contenu lipidique mesuré chez cinq petits mammifères (le Tamia amène (Tamias amoenus Allen), le Néotoma à queue touffue (Neotoma cinerea Ord), la Souris à pattes blanches (Peromyscus maniculatus Ord), le Campagnol-à-dos-roux de Gapper (Clethrionomys gapperi Vigors) et le Campagnol des champs (Microtus pennsylvanicus Ord). Nous avons également tenté de déterminer si le contenu hydrique du corps permet de prédire le contenu lipidique, ce qui justifierait l'utilisation d'une dilution des isotopes d'hydrogène pour estimer la condition physique. Chez les cinq espèces, les indices de la condition physique se sont révélés des indicateurs médiocres du contenu lipidique; ils permettent toutefois de prédire plus exactement la masse du corps sans les graisses, la masse sèche et le contenu en eau. La relation entre le contenu hydrique et le contenu lipidique n'est pas la même chez les cinq espèces, ce qui nous empêche de recommander la méthode de dilution des isotopes chez ces animaux. Malgré leur intérêt écologique, c'est comme facteurs explicatifs de la variation de toutes les composantes du corps que ces indices semblent le plus utiles.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

When separated from conspecifics, the young of many rodent species produce ultrasonic vocalizations (USVs) that may facilitate parental approach. Ultrasounds were recorded from infants (0–14 days post partum) of two closely related species that exhibit different social systems, the montane vole (Microtus montanus) and the prairie vole (Microtus ochrogaster). Infant prairie voles emitted a greater number of USVs when isolated from conspecifics than did infant montane voles. Infant prairie voles also emitted a greater number of USVs in the presence of a parent than did infant montane voles. For both species, parental responses to individual infants were most rapid when pups were at those ages when they emitted the greatest numbers of USVs. Prairie vole parents approached pups most rapidly on days 6–8, whereas montane vole parents approached pups most rapidly on days 12–14. There were no differences between sires and dams of either species in their latencies to approach and contact pups. In general, however, infants of both species were retrieved more rapidly by dams than by sires. We suggest that differences in ultrasound production among vole species may correlate with differences in their species-specific social systems. It appears that the number of USVs produced by pups may vary with the amount of parent-pup contact typical of each species.Lorsqu'ils sont séparés des autres animaux de leur espèce, les jeunes de plusieurs rongeurs émettent des ultrasons (USVs) qui peuvent faciliter l'approche des parents. Nous avons enregistré les ultrasons émis par des petits (âgés de 0 à 14 jours) de deux espèces très apparentées, mais à systèmes sociaux différents, le Campagnol montagnard (Microtus montanus) et le Campagnol des Prairies (Microtus ochrogaster). Les petits du Campagnol des Prairies émettent un plus grand nombre de USVs lorsqu'ils sont isolés que les petits du Campagnol montagnard. Les petits Campagnols des Prairies émettent aussi plus de cris en présence d'un parent que les petits Campagnols montagnards. Chez les deux espèces, les parents réagissent plus rapidement aux cris des petits à l'âge où ils en émettent le plus. Les parents des petits Campagnols des Prairies réagissent le plus rapidement aux cris de leurs petits lorsque ceux-ci sont âgés de 6 à 8 jours, alors que chez le Campagnol montagnard, c'est lorsque les petits ont 12–14 jours que les parents réagissent le plus rapidement. Il n'y a pas de différence entre pères et mères quant au temps de latence avant l'approche et le contact des petits. Cependant, de façon générale, les petits des deux espèces sont récupérés plus rapidement par leur mère que par leur père. Nous croyons que les différences dans la production des ultra-sons chez les différentes espèces peuvent dépendre des systèmes sociaux particuliers à chaque espèce. Il est possible que le nombre de USVs émis par les petits varie en fonction de l'importance du contact physique parent-petit propre à chaque espèce.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

We studied small-mammal populations across a range of spatial scales to determine if they exhibited spatial variability that was independent of the distribution of vegetation. Between 1996 and 1999, systematic livetrapping surveys were conducted on nested grids at three scales: (1) extent (total area covered by a grid) = 4900 ha, grain (minimum space between sampling points) = 1000 m; (2) extent = 306 ha, grain = 250 m; and (3) extent = 31 ha, grain = 125 m. The four most abundant species were the red-backed vole (Clethrionomysgapperi), the short-tailed shrew (Blarina brevicauda), the deer mouse (Peromyscus maniculatus), and the woodland jumping mouse (Napaeozapus insignis). Small mammals exhibited spatial population structure over distances up to 250 m but not over 1000 m. There was a component of this population structure that appeared to be temporally and spatially dynamic, and that was not correlated with measured vegetation variables. We discuss processes that would create the observed metapopulation structure in seasonal landscapes.Nous avons étudié des populations de petits mammifères à plusieurs échelles spatiales pour déterminer si ces populations subissent une variabilité spatiale indépendante de la répartition de la végétation. De 1996 à 1999, nous avons procédé au piégeage d'animaux vivants dans des grilles d'échantillonnage emboîtées, sur trois échelles : (1) étendue = 4900 ha, pas d'échantillonnage = 1000 m; (2) étendue = 306 ha, pas d'échantillonnage = 250 m; (3) étendue = 31 ha, pas d'échantillonnage = 125 m. Le Campagnol-à-dos-roux de Gapper (Clethrionomys gapperi), la Grande Musaraigne (Blarina brevicauda), la Souris sylvestre (Peromyscus maniculatus) et la Souris sauteuse des bois (Napaeozapus insignis) étaient les quatre espèces les plus abondantes. Les populations de petits mammifères avaient une structure spatiale à un pas d'échantillonnage de plus de 250 m, mais pas à un pas de plus de 1000 m. L'une des composantes de cette structure semblait dynamique en temps et en espace, mais n'était en corrélation avec aucune des variables reliées à la végétation. Nous examinons les processus qui pourraient être responsables de la structure observée dans les paysages saisonniers.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]