Is communal burrowing or burrow sharing a benefit of group living in the lesser cavy <Emphasis Type="Italic">Microcavia australis</Emphasis>?

Burrow systems play an important role in the life of rodents in arid environments. The objectives of this study were to examine the hypothesis that group living is beneficial to the semifossorial rodent, and determine whether Microcavia australis (Geoffroy and d’Orbigny, 1833) burrows communally and/or shares burrow systems. I related the structure of burrow systems to the number of cavies inhabiting them, in two habitats with different soil hardness and different plant cover (El Leoncito and Ñacuñán). El Leoncito has a harsh climate, with lower plant density and softer soil than Ñacñuán. A total of 18 burrow systems were characterized at Ñacuñán, and 12 at El Leoncito. Social groups at El Leoncito have a higher number of individuals than at Ñacuñán, but the structure of burrow systems in softer soil is narrower (small area size), with fewer holes, less slope and depth of galleries, and with no relationship between the number of holes and burrow area. Therefore, considering the development of the burrow system as an indicator of the cost of burrowing, I conclude that communal burrowing to reduce the energetic cost of burrowing per capita is not the primary cause of cavy sociality. M. australis were not active diggers, because digging behaviour was rarely recorded at either site. Burrow systems of cavies persisted over the years of study, occupied by the same cavies and new offspring, and digging new burrow systems and tunnels was a relatively rare event at both sites. Under the burrow-sharing hypothesis, sociality could prevail in M. australis that regularly dig to build and maintain a burrow system which they use for a long time.     

Comparing composition of social groups,mating system and social behaviour in two populations of Microcavia australis

Microcavia australis is a semifossorial, diurnal and social rodent, native to South America. The objective was to determine and compare the composition of social groups, mating system and social behaviours of cavies in two populations of the Monte (El Leoncito and Ñacuñán). The two sites differ in climate conditions and plant resource availability. Trapping was carried out on 7–11 consecutive days at three times of the year (food abundance, food shortage, reproduction), from 2003 to 2005. Individuals were identified with metal ear tags. Continuous focal samplings were performed during 4 days. The female/male proportion per group was 1/1 at both sites which, together with the absence of sexual dimorphism in body size (0.94), the accomplishment of oestrus synchronization, the large size of scrotal testes during the reproductive season and sexual patterns, suggests a promiscuous mating system. Social groups were larger and with more adults at the site with more severe climate conditions (El Leoncito). The index of association among individuals was higher at El Leoncito. Cavies could use seismic communication to avoid encounters ending in fights at El Leoncito, and the agonistic behaviour was significantly lower in this population.     

Grazing impact on desert plants and soil seed banks: Implications for seed-eating animals

We assess whether the knowledge of livestock diet helps to link grazing effects with changes in plant cover and soil seed bank size, aiming at inferring the consequences of grazing on seed-eating animals. Specifically, we test whether continuous and heavy grazing reduce the cover, number of reproductive structures and seed reserves of the same grass species whose seeds are selected and preferred by granivorous animals in the central Monte desert, Argentina. Grass cover and the number of grass spikes usually diminished under grazing conditions in the two localities studied (Telteca and Ñacuñán), and soil seed bank was consistently reduced in all three years evaluated owing to a decline of perennial grass and forb seeds. In particular, the abundance of those seeds selected and preferred by birds and ants (in all cases grass species) declined 70–92% in Ñacuñán, and 52–72% in Telteca. Reduction of perennial grass cover and spike number in grazed sites reinforced the causal link between livestock grazing and the decline of grass soil seed reserves throughout failed plant reproduction. Grass seed bank depletion suggests that grazing may trigger a “cascade” of mechanisms that affect the abundance and persistence of valuable fodder species as well as the availability of seed resources for granivorous animals.     

Net primary productivity and nitrogen and carbon distribution in two xerophytic communities of central-west Argentina

Net primary productivity and the nitrogen, carbon, and energy contents of the leaf, aerial wood and root components of the five most important woody dominants in two xerophytic forests in central-west Argentina were measured. Nitrogen and carbon contents of litter and mineral soil beneath individual plant canopies were also studied. The woody dominants in the 8-yr old ‘chaco’ woodland in Chamical, La Rioja, covered a greater proportion of total community area but had less aerial biomass than the 5 woody dominants of the 50-yr-old openProsopis flexuosa woodland in Ñacuñán, Mendoza. Marked differences in net primary production among species of the two communities were also noted (29–115 kg aerial biomass ha^?1 yr^?1 in the Chamicalvs 51–524 kg ha^?1 yr^?1 in the Ñacuñán woodland). Nitrogen in vegetation varied by species, and within species, varied by season and plant component. In general, leaf-N was higher in legumes in summer than in non-legumes in summer, and for most species higher in summer than in winter. Differences in %N in other plant components and in per cent C among species and seasons were less consistent. In both communities, soil N and C were higher and more variable with depth under individual plant canopies than in non-vegetated areas, and differences among species were apparent.     

Locomotion and Escape Modes in Rodents of the Monte Desert (Argentina)

Modes of locomotion and escape tactics are attributes that affect the structure of animal communities, promoting exploitation of different microhabitats and the coexistence of different species. Bipedal locomotion is considered to be more effective than a quadrupedal gait in escaping attacks by predators because it allows for higher speed, a faster response to attack, sudden changes of direction and better detection of aerial raptors. The aim of this study was to determine the type of locomotion used at the moment of escape by three rodent species of the Monte desert –Eligmodontia typus, Akodon molinae and Graomys griseoflavus. The study was carried out in three plant communities of the Ñacuñán Reserve (Mendoza). All three species showed differences in both mode of escape and locomotory pattern. Graomys griseoflavus exhibited the highest proportion of escapes using quadrupedal saltation. The mode of locomotion employed by E. typus varied according to the type of plant communities it inhabited. Those occurring at open sites (Medanal community) exhibited a greater propensity to jump during escapes than those from more sheltered habitats (Algarrobal community). Akodon molinae relied primarily on a quadrupedal gait when fleeing from predators, which would explain its greater dependence on plant cover. Therefore, the morphological and behavioural characteristics of these species are related to their mode of locomotion and the strategies they employ to diminish the risk of predation.     

Effects of wild boar disturbance on vegetation and soil properties in the Monte Desert,Argentina

The wild boar (Sus scrofa) is an exotic agent of disturbance that arrived in the Ñacuñán Reserve of Argentina in the 1980s. When foraging, the wild boar overturns extensive areas of soil leaving them bare of vegetation. Knowledge is scarce about the boar's impact on vegetation composition and soil properties in the Monte Desert, Argentina. The objective of our study was to determine the short terms effects of wild boar rooting on vegetation and on soil physical, chemical and microbiological properties. Our results indicate that rooting activities significantly reduced the plant cover of herbs, perennial grasses and shrubs, and decreased plant richness and diversity. Disturbed soils showed less compaction, more moisture, a low C/N ratio, and high content of mineral nitrogen. These new soil characteristics could be responsible for a reduced plant cover and less soil bulk density, which could increase soil degradation by wind erosion.     

Habitat protection,cattle grazing and density‐dependent reproduction in a desert tree

Anthropogenic activities usually trigger changes in the population density of plants. Thus, land management practices can influence density‐dependent demographic parameters and species interactions. We investigated plant‐pollinator interactions and reproduction in Prosopis flexuosa, the largest tree species in the Central Monte desert of Argentina, an important economic and cultural resource for humans and a functionally prominent species. We hypothesized that reproductive output of P. flexuosa would be limited at low densities, and that exclusion of catle grazing would enhance population density and consequently interaction frequency with pollinators and reproductive success. The study was conducted in and around Ñacuñán Biosphere Reserve (Mendoza, Argentina), where cattle grazing has been excluded for over 35 years. Working in five pairs of protected and cattle grazed 1‐ha plots, we recorded density of adult trees, pollinator visitation frequency to inflorescences and seeds per inflorescence in focal trees. Adult tree density was higher in protected plots than in cattle grazed plots. Density of reproductive trees was positively correlated with seed production, suggesting positive density dependence for reproduction (Allee effect). Pollinator visitation to inflorescences and seed production was higher in protected plots compared with plots under cattle grazing. Suppression of anthropogenic degradation has resulted in higher adult tree density in protected plots, indirectly higher pollinator visitation to inflorescences and higher reproductive success of trees. Increased frequency of plant‐pollinator interactions and tree reproduction suggest success of management practices aimed at protecting P. flexuosa woodlands.     

Dendroecology of Prosopis flexuosa woodlands in the Monte desert: Implications for their management

In the Monte desert of Argentina open woodlands of several species of Prosopis occur in areas with accessible underground water. The great latitudinal extent of the Monte (26–43°S) exhibits strong climatic gradients involving temperature, rainfall seasonality, and wind regime. Prosopis woodlands have been a source of subsistence for human communities for several centuries and continue to be exploited by the local inhabitants. The “mining” of this resource has led to severe desertification and consequent impoverishment of the local people. In order to suggest strategies for the better management and recuperation of these woodlands we studied the population structure and productivity of Prosopis flexuosa from multiple plots at Pipanaco (27°58′S), Telteca (32°20′S), and Ñacuñán (34°03′S). For each plot we measured the density of P. flexuosa trees, number of stems, basal diameter (DAB), height and canopy diameter of each tree. Tree ring data were used to determine the growth rates, annual wood production and biological rotation age for each area. The ecological structure of the woodlands differs between the three sites. Along this north–south transect, there is a decrease in adult tree density, mean basal diameter, mean tree height, canopy cover, productivity and total wood biomass. Consequently, the potential sustainable use of these woodlands varies. Only the northern, Pipanaco, woodlands have the potential for lumber production. In contrast, the short, multi-stem and low-productivity trees in the Telteca and Ñacuñán areas can only sustain a combination of local firewood production and activities such as extensive grazing by livestock. The present, uniform regulations for harvesting wood in these areas must be changed to acknowledge these differences in order to optimize wood production in, and conservation of, these woodlands.     

Mechanic defences and reproduction in desert trees under different habitat management

Herbivory can have deleterious effects on plant reproduction by limitation of photosynthates that are either lost by consumption, used to re-growth or invested in defences. In addition, herbivores can also exert direct impact on plant reproduction by consuming flowers. Spine length can act as an inducible defence in plants, because it tends to increase with increasing herbivore pressure. I hypothesized that almost 40 years of different habitat management (cattle exclusion within a protected area vs. cattle grazing in adjacent areas) could affect inflorescence abundance, spine length and fruit production in Prosopis flexuosa trees. The study area was located in the Central Monte desert of Argentina. I estimated differences in spine length, number of inflorescences and fruit production in trees inside the Man and Biosphere Reserve of Ñacuñán and in the adjacent cattle ranches surrounding the protected area. Inflorescence abundance in the tree canopy was similar in cattle grazed and protected sites, but the presence of large herbivores was associated with limited fruit production. Spines were 37% shorter and fruit production three times higher in trees inside the reserve than in trees in cattle ranches. A negative exponential model was used to describe the relationship between reproduction and spine length in trees. The results indicate that after almost four decades of cattle exclusion, trees inside the protected area show higher reproduction and shorter spines than cattle-browsed trees in surrounding areas. The negative association between defence and reproduction may be due to competition for photosynthates. The present results could be useful and relevant in conservation because they provide evidence on how anthropogenic habitat use can affect plant phenotypes and fitness, which in turn can affect the long-term ecological and evolutionary dynamics of plant populations.     

El Niño and dry season rainfall influence hostplant phenology and an annual butterfly migration from Neotropical wet to dry forests

We censused butterflies flying across the Panama Canal at Barro Colorado Island (BCI) for 16 years and butterfly hostplants for 8 years to address the question: What environmental factors influence the timing and magnitude of migrating Aphrissa statira butterflies? The peak migration date was earlier when the wet season began earlier and when soil moisture content in the dry season preceding the migration was higher. The peak migration date was also positively associated with peak leaf flushing of one hostplant (Callichlamys latifolia) but not another (Xylophragma seemannianum). The quantity of migrants was correlated with the El Niño Southern Oscillation, which influenced April soil moisture on BCI and total rainfall in the dry season. Both hostplant species responded to El Niño with greater leaf flushing, and the number of adults deriving from or laying eggs on those new leaves was greatest during El Niño years. The year 1993 was exceptional in that the number of butterflies migrating was lower than predicted by the El Niño event, yet the dry season was unusually wet for an El Niño year as well. Thus, dry season rainfall appears to be a primary driver of larval food production and population outbreaks for A. statira. Understanding how global climate cycles and local weather influence tropical insect migrations improves the predictability of ecological effects of climate change.     

El Niño,Host Plant Growth,and Migratory Butterfly Abundance in a Changing Climate

In the wet forests of Panama, El Niño typically brings a more prolonged and severe dry season. Interestingly, many trees and lianas that comprise the wet forests increase their productivity as a response to El Niño. Here, we quantify the abundance of migrating Marpesia chiron butterflies over 17 yr and the production of new leaves of their hostplants over 9 yr to test the generality of the El Niño migration syndrome, i.e., whether increased abundance of migrating insects and productivity of their food plants are associated with El Niño and La Niña events. We find that the quantity of M. chiron migrating across the Panama Canal was directly proportional to the sea surface temperature (SST) anomaly of the Pacific Ocean, which characterizes El Niño and La Niña events. We also find that production of new leaves by its larval host trees, namely Brosimum alicastrum, Artocarpus altilis, and Ficus citrifolia, was directly proportional to the SST anomaly, with greater leaf flushing occurring during the period of the annual butterfly migration that followed an El Niño event. Combining these and our previously published results for the migratory butterfly Aphrissa statira and its host lianas, we conclude that dry season rainfall and photosynthetically active radiation can serve as primary drivers of larval food production and insect population outbreaks in Neotropical wet forests, with drier years resulting in enhanced plant productivity and herbivore abundance. Insect populations should closely track changes in both frequency and amplitude of the El Niño Southern Oscillation with climate change.     

Spatial and temporal litterfall heterogeneity generated by woody species in the Central Monte desert

In arid and semiarid environments, the presence of woody species generates a series of environmental gradients that increase spatial heterogeneity and modify the pattern of distribution of the other species. We postulate that the temporal and spatial variability in litter input generated by woody species is a relevant factor in the generation of edaphic heterogeneity by redistribution of nutrients and the physical effects of litter. The objective of this study was to determine the temporal and spatial variability in the amount of litter input under the canopy of dominant woody plants (Prosopis flexuosa and Larrea divaricata) and in exposed areas at the Ñacuñán Reserve, in the central zone of the Monte desert. Litterfall was collected during 2 years from 30-cm-diameter litter traps distributed at three microsites: under P. flexuosa canopy, under L. divaricata canopy, and in exposed areas. Microhabitats beneath Prosopis showed the highest litter input per m² (between 320 and 527 g/m²), and, consequently, more than 50% of it fell to the soil beneath the canopy of P. flexuosa. Only 10% fell on exposed areas, which exhibited an annual input rate per m² of a lower order of magnitude than the sites under Prosopis. Litterfall presented a peak in summer as a consequence of convective storms, and a second one in autumn due to phenological shedding. Our results suggest that woody species have a central importance in the dynamics of nutrients in arid lands by both the increase of total productivity and litterfall, and the spatial and temporal regulation of litter input.     

Revaluación de la versión española del cuestionario Diabetes Quality of Life (EsDQOL)

La experiencia acumulada a lo largo de varios años con la versión española del Diabetes Quality of Life Questionnaire (EsDQOL) nos ha conducido a proponer una serie de modificaciones que incrementan la fiabilidad y mejoran la aplicación del cuestionario.Se ha realizado un nuevo análisis de la fiabilidad (consistencia interna) mediante α de Cronbach, con la exclusión de los ítems 3, 8 y 16 de la subescala “Impacto”, al observar que estos ítems pueden generar confusión en la interpretación y evaluación del cuestionario. El análisis se ha llevado a cabo en una población de 823 pacientes diabéticos (711 tipo 1 y 112 tipo 2) tratados con insulina. Este nuevo análisis muestra que la eliminación de los tres ítems incrementa α de Cronbach en ambos grupos de pacientes, tanto en la subescala de “Impacto” como en la fiabilidad global del cuestionario, por lo que se propone la utilización de esta versión reducida del cuestionario EsDQOL.     

Preliminary Evidence of the Importance of ENSO in Modifying Food Availability for White‐tailed Deer in a Mexican Tropical Dry Forest1

The influence of El Niño/Southern Oscillation (ENSO) on rainfall and its possible effect on availability of food for white‐tailed deer (Odocoileus virginianus) in a tropical dry forest in the Pacific coast of Mexico was studied. From 1977 to 2003 there were three significant El Niño and La Niña events. During El Niño years rainfall decreased during the wet season ( June to October) and increased during the dry season (November to May), with the opposite effect during La Niña years. Plant diversity was monitored in permanent plots during the wet and dry seasons of 1989–1993. The results provide evidence that ENSO events affect deer food availability, particularly in the dry season.     

The effects of El Niño–La Niña on reproductive parameters of elephant seals feeding in the Bellingshausen Sea

Aim To assess the impacts of El Niño–La Niña events on the pup weaning mass and diet of female southern elephant seals (Mirounga leonina) feeding in the Bellingshausen Sea, Antarctica, and to understand the ecological processes that drive these impacts. Location Atlantic southern elephant seal weaning mass and diet were measured at King George Island (62º14′ S, 58º30′ W). Feeding areas for pregnant female seals from King George Island are located west of Alexander Island in the Bellingshausen Sea. Methods Data on weaning mass were collected between 1985 and 1994 during the breeding season (September–November). Moulting females were anaesthetized and cephalopod beaks were isolated and identified from stomach contents obtained from stomach lavages. Sea‐surface temperature anomaly (SSTA) data for the ‘El Niño 3.4’ geographical region (5º N–5º S, 120º W–170º W) were used to define El Niño–Southern Oscillation (ENSO) event years (grouped as El Niño, La Niña and Neutral) as well as the strength of each ENSO event year. Using data from the US National Center for Environmental Prediction, temperature, sea ice concentration and atmospheric pressure anomalies in the Bellingshausen Sea were calculated from March to August, corresponding to the feeding period of pregnant female seals. Results Positive temperature anomalies and negative pressure anomalies in the Bellingshausen Sea were observed during La Niña years and negative temperature anomalies and positive pressure anomalies during El Niño years. These data correlate with sea ice concentration anomalies, which are highly negative during La Niña years and highly positive during El Niño years. Warm temperature conditions in the Bellingshausen Sea during La Niña years are strongly related to both higher weaning mass in elephant seals and to an increase in squid beaks in the stomach contents of females. Main conclusions It is possible that higher elephant seal weaning masses in La Niña years correlate with warmer waters in the Bellingshausen Sea leading to the rapid growth of squid and their more frequent descents to depths frequented by elephant seals. This results in increased predation by pregnant females, leading to a greater mass among weaned pups. This hypothesis may guide future research about interactions between climate and the marine biosphere.     

Functions of Intermittent Locomotion in Mustached Tamarins (<Emphasis Type="Italic">Saguinus mystax</Emphasis>)

Many animals interrupt their moving with brief pauses, which appear to serve several different functions. We examined the function of such intermittent locomotion in wild living mustached tamarins (Saguinus mystax), small arboreal New World primates that form mixed-species groups with saddleback tamarins (Saguinus fuscicollis). We investigated how different environmental and social factors affect pausing during locomotion and used these data to infer the function of this behavior. As measures of intermittent locomotion, we used percentage of time spent pausing and pause rate. We considered 3 possible functions that are not mutually exclusive: increased endurance, route planning, and antipredator vigilance. Mustached tamarins spent on average (mean ± SE) 55.1 ± 1.0% of time pausing, which makes effective resource exploitation more time consuming and needs to be outweighed by correspondingly large benefits. Percentage of time spent pausing decreased in larger mixed-species groups vs. smaller mixed-species groups and decreased with height and in monkeys carrying infants. It was not affected by sex, age, spatial arrangement, or single-species group size. Pause rate increased in individuals traveling independently compared to those traveling in file, but was not affected by other factors. The group size effect in mixed-species groups lends support to the notion that pausing during locomotion is an antipredator tactic that can be reduced in the increased safety of larger groups, but other results suggest that additional functions, particularly route planning, are also of great importance. Benefits in terms of predator confusion and group movement coordination are also likely to play a role and remain a topic for further research.     

Effects of Microhabitat‐Dependent Predation Risk on Vigilance during Intermittent Locomotion in Psammodromus algirus Lizards

Animals should be able to adjust their behavior by tracking changes in predation risk level continuously. Many animals show a pattern of intermittent locomotion with short pauses that may increase detection and vigilance of predators. These locomotor patterns may depend on the microhabitat structure, which affect predation risk levels. We examined in detail in the laboratory the characteristics of spontaneous locomotion, scanning behavior, and the escape performance of Psammodromus algirus lizards moving in two different microhabitats (leaf litter patches and open sand areas). Results showed that in leaf litter, lizards moved at slower speed and had shorter bursts of locomotion both in distance and duration, than in sand substrates. This locomotor pattern allowed lizards to increase scanning rate and total time spent in vigilance behavior. When lizards were forced to flee, they escaped to longer distances and during more time in open sand areas, but lizards were able to attain similar escape speed in the two substrates. Lizards may be able to compensate the cost of moving between different microhabitats with different predation risk by behaviorally changing their locomotor and vigilance patterns. However, complex interactions between the visibility of lizards to predators and the ability of lizards to detect predators, together with the need of attending simultaneously to other conflicting demands, may lead to apparently non‐intuitive solutions in locomotor patterns and the rate of vigilance behavior.     

Phytogeographic analysis of taxa endemic to the Yucatán Peninsula using geographic information systems, the domain heuristic method and parsimony analysis of endemicity

Abstract. The distribution of plant taxa endemic to the Yucatán Peninsula was studied using Parsimony Analysis of Endemicity (PAE). The known distribution of 162 endemic plant taxa was plotted and the DOMAIN method together with environmental data were used to model the potential distribution for each taxon. The Peninsula was divided into a grid of quarter‐degree cells for the purpose of identifying distribution patterns. A total of 294 cells were analysed using known collection records and potential distribution of endemic taxa data. Two data matrices were constructed, a matrix of known distribution and a matrix of both the known and potential distribution. The two matrices were included in the PAE to identify areas of endemism. The areas determined with the known distribution were restricted and almost half of them remained unresolved, whereas with the potential distribution, approximately 90% of the cells were assigned to any one of the endemicity areas. Four endemism areas were identified: the Yucatán dry zone, Yucatán, El Petén and Belize. The areas of Yucatán and El Petén could be explained by current and Pleistocene climatic conditions and their congruence with other biological groups. Analysis of the potential distribution identified areas with patterns that share current environmental characteristics and a palaeoclimate history. Potential distribution modelling can eliminate uncertainties in biogeographical analysis caused by lack of data distribution and sample variation and produce information about the relationships between areas and taxa as well as the environmental affinities of taxa.     

Head raising during foraging and pausing during intermittent locomotion as components of antipredator vigilance in chipmunks

Although many studies of vigilance examine head raising in foraging, grooming or resting animals, pauses during intermittent locomotion are rarely considered from the perspective of vigilance, and no studies have compared head raising and pausing in the same system. We videotaped central place foraging chipmunks, Tamias striatus, as they approached a patch, collected sunflower seeds, and left to return to their burrows. There was a strong similarity between head raising during foraging and pausing during intermittent locomotion. Chipmunks paused more frequently when moving towards the patch than when leaving the patch. Chipmunks in the patch raised their heads at an intermediate rate, which tended to decrease with time in the patch. Pauses and the duration of motionless periods during head raises were very short (∼0.4 s), and their frequency distributions were similar. Animals remained motionless during 22% of the time spent approaching the patch, 14% of the time spent in the patch and 7% of the time spent leaving the patch. Rates of pausing and head raising generally decreased with short-term familiarity (number of trips to the patch) and with long-term familiarity (proximity of the patch to the burrow). Trials with higher pause rates when approaching the patch had higher head-raising rates in the patch. Whether the focal individual was solitary, dominant or subordinate in a dyad, or competing with multiple chipmunks in the patch had no effect on pausing or head raising. In a separate experiment, exposure to a model hawk increased pause and head-raising rates. We conclude that head raising during foraging and pausing during locomotion serve a similar vigilance function, that this vigilance is directed towards detection of predators rather than conspecifics, and that time allocated to vigilance is sufficient to significantly reduce foraging rates and affect many space use and foraging decisions.     

A damped precipitation‐driven,bottom‐up model for deer mouse population abundance in the northwestern United States

Small‐mammal population densities can be regulated by bottom‐up (food availability) and top‐down (predation) forces. In 1993, an El Niño Southern Oscillation event was followed by a cluster of human hantavirus with pulmonary syndrome in the southwestern United States. An upward trophic cascade hypothesis was proposed as an explanation for the outbreak: Increased plant productivity as a consequence of El Niño precipitations led to an unusual increase in distribution and abundance of deer mice (Peromyscus maniculatus ; reservoir host of Sin Nombre virus). Could such drastic events occur in mesic habitats, where plant productivity in response to climate conditions is likely to be much less dramatic? In this work, we investigate to what extent deer mouse populations follow a precipitation‐driven, bottom‐up model in central and western Montana and discuss important conditions for such a model to be possible. We found positive correlations between deer mouse abundance and on‐the‐ground measured plant productivity with a several‐month lag in three of six study sites. This effect was weaker when deer mouse populations were more abundant, indicating density‐dependent effects. Dispersal resulting from territoriality may be important in attenuating local density increments in spite of high food availability. In addition, there is evidence that population abundance in the study area could respond to other abiotic factors. In particular, precipitation in the form of snow may reduce deer mice survival, thus compensating the benefits of improved plant productivity. Deer mouse populations in Montana study sites follow complex dynamics determined by multiple limiting factors, leading to a damped precipitation‐driven bottom‐up regulation. This prevents dramatic changes in rodent abundances after sudden increments of food availability, such as those observed in other regions.