Rodent Abundance Research Articles

Drivers of Bird and Rodent Assemblage Composition in Rangelands of Southern Mexican Plateau

Rangelands provide ecosystem services for livestock and habitat for many wildlife species. However, the key features that determine their value for biodiversity conservation need to be assessed regionally. To elucidate the structural attributes that drive bird and rodent assemblages in semiarid rangelands in the southern Mexican Plateau, we studied patches of rangelands dominated by herbaceous plants (open) and xerophytic shrub communities (closed). We hypothesized that different guilds and species of birds and rodents are influenced differently by rangeland condition and different habitat components, and that bird assemblages had a higher turnover rate between patches than rodents. We surveyed the birds and rodents during the three regional climatic seasons and measured ground plant cover of herbs, shrubs, nopales, and trees. Through an information-theoretic approach we tested the effect of range condition and season on all variables of habitat and bird and rodent species richness and abundance. Habitat components (shrubs and nopales) most often included in the best/most parsimonious models explained bird and rodent abundances. Rodent species turnover is lower among rangeland plots of the same type geographically separated than between nearby plots of different type. In contrast, bird species turnover was higher because their higher mobility allows them to explore landscape patches than might offer complementation and/or supplementation. Rangelands in the southern Mexican Plateau should be viewed not only as livestock-producing areas but also as landscape components that can and should be used to effectively support biodiversity conservation, complementing the conservation role of other regional habitats. The high biodiversity conservation potential of the rangelands we studied should be recognized, and both habitat conditions should be incorporated in any regional conservation plans.

Demographic and functional responses of kit foxes to changes in prey abundance

Many carnivores exhibit demographic and functional responses to changes in prey abundance. Demographic responses often include changes in population size, litter size, and recruitment of young into the adult population. Functional feeding responses are commonly reported for many carnivore species. We investigated demographic and functional responses of kit foxes ( Vulpes macrotis Merriam, 1888) to changes in prey abundance during 2010–2013 in western Utah, USA. Between 2010 and 2013, litter size averaged 3.9 (±1.4) pups/litter. Survival rates of kit fox pups were 0.07, 0.01, 0.46, and 0.16, respectively, and there was a correlation between pup survival rates and rodent abundance; leporid (family Leporidae Fischer, 1817) abundance did not influence pup survival. There was a functional response as occurrence of kangaroo rat in the diet closely followed changes in kangaroo rat abundance. The occurrence of rodents in kit fox diet followed declines in rodent abundance (excluding Dipodomys spp. Gray, 1841). Leporid consumption by kit foxes was not correlated to leporid density. Kit fox survival was dependent on rodent abundance and more specifically, kangaroo rats. Understanding which population parameters of kit foxes are influenced by prey is critical for the conservation of this native mesocarnivore.

Rongeurs de la localité éocène de Cos (Tarn-et-Garonne, Quercy, France). Comparaison avec les rongeurs de localités de la transition Éocène inférieur/Éocène moyen

Rodents from the Eocene locality of Cos (Tarn-et-Garonne, Quercy, France). Comparison with rodents from localities of the transition lower Eocene/middle Eocene. This article describes the rodents of the new fauna of Cos (Tarn-et-Garonne, Quercy) whose primates were first studied and published (Godinot et al. 2021) Among these poorly diversified rodent assemblage, the smallest species is assigned to Eogliravus wildi. All Eogliravus Hartenberger, 1971 species are redescribed here and their diagnoses are emended. Two specimens are designated as a small-sized indeterminate theridomorph. The largest and most abundant rodent represents a new species of the Theridomorph genus Masillamys namely M. cosensis n. sp. The analysis of its morphological and morphometric variability enables to highlight a high variability of the lower and upper premolars, whereas molars variability is lower. This species is compared with the late Ypresian and early Lutetian Masillamys. It represents a more derived evolutionary grade than Masillamys mattaueri Hartenberger, 1975, from Mas de Gimel (Hérault; MP10) especially by its slightly larger size, and a less derived stage than that of the Masillamys from Messel (Hesse; MP11), especially by its still weaker hypocone relative to the protocone on the upper molars. Masillamys cosensis n. sp. also occurs in Viélase (Aveyron). These rodents pointe toward a time interval comprised between the European reference levels MP10 and MP11, near the Ypresian-Lutetian transition, and contribute to the discussion about the biochronology of this time interval.

Influence of vegetation structure, seasonality, and soil properties on rodent diversi community assemblages in west Mount Kilimanjaro, Tanzania.

Rodent diversity and community assemblages are affected by several biotic and abiotic factors such as vegetation structure and seasonality. Vegetation structure particularly ground cover influences rodent diversity and community assemblages through provision of food resources and protection from predators. Such information is important for understanding species–habitat relationships for management and conservation. This study was conducted to determine the influence of vegetation structure, seasonality, and soil properties on species richness, abundance, community assemblages, and habitat association of rodents in west Mt Kilimanjaro. Rodent trapping was conducted using removal and capture–mark–recapture (CMR) methods with medium‐sized Sherman's live traps, snap, and Havarhart traps. Rodents were trapped during wet and dry seasons for three consecutive nights at 4 weeks intervals from April 2020 to March 2021. Environmental variables including vegetation structure, soil physical properties, and disturbance levels were recorded for each habitat type. Fourteen species of rodents were trapped in 25,956 trap nights. Rhabdomys pumilio, Praomys delectorum, and Lophuromys verhageni were the most dominant species across all habitats and seasons. L.verhageni occurred in all habitats while R.pumilio was restricted from occurring in montane forests. Moreover, species richness and abundance were influenced by habitat types, seasonality, soil type, and ground cover. Generally, both species richness and abundance were higher in fallows and montane forests and significantly lower in plantation forest and agricultural fields. In addition, rodent diversity was highest in fallows, followed by montane forests, and lowest in agricultural fields. Furthermore, rodents were associated with habitat types and vegetation structure forming two major community assemblages that significantly differed between habitats. Our study conclude that, community assemblages of rodents on Mt. Kilimanjaro were affected by functional spatial heterogeneity of the habitats occupied. Therefore, use of different habitats by rodents may be indicative of the landscape integrity and ecosystem changes based on species assemblages.

The influence of sugarcane pre‐harvest fire on hantavirus prevalence in Neotropical small mammals

AbstractThe use of pre‐harvest fire in sugarcane fields surprisingly results in an increase in the abundance of Neotropical Sigmodontinae rodents, which might carry hantavirus. By contrast, fire suspension induces a decline in rodents in the first 5 years. The present study aimed to evaluate the effect of sugarcane harvest regimes on hantavirus prevalence in wild rodents. Field collections were carried out on a sugarcane production area in Northeast São Paulo, which is responsible for 30% of the ethanol production in Brazil. A few years after pre‐harvest fire suspension, a high prevalence of hantavirus was found in small rodents at lower population density, but apparently higher population growth rate. Differences in life cycle between the rodents and their predators may explain such density patterns, as small rodents can breed twice or even three times each year, whereas their predators usually breed only once a year. Similarly, the temporal dynamics of the predator–prey relationship suggests that hantavirus prevalence is related to small rodent's population growth and not density. OnlyAkodon montensis,Calomys tener, andNecromys lasiuruscontained immunoglobulin G antibodies against the recombinant nucleoprotein ofAraraquara orthohantavirus, a genotype ofAndes orthohantavirus, with no interspecific variation in seroprevalence among these species. However, males presented higher prevalence rate than females, possibly due to a male‐biased dispersal pattern and a higher frequency of antagonistic interactions. Governance measures to mitigate the role of small wild rodents on the emergence of hantavirus in agricultural landscapes dominated by sugarcane plantations should include the use of wildlife‐friendly management techniques (e.g., to mitigate the mortality of the predators of small rodents), human capacity building concerning wildlife‐related conflicts, and multifunctionality of agricultural landscapes. Future studies should prioritize the possible relationship between microhabitat structure and hantavirus prevalence in small rodents in agricultural landscapes dominated by sugarcane fields.

First record of Black-eared Rice Rat, Handleyomys melanotis (Thomas, 1893) (Rodentia, Cricetidae), on a protected island off the Pacific Coast of Jalisco, Mexico, with notes on its potential threat for avian nesting species

Black-eared Rice Rat, Handleyomys melanotis (Thomas, 1893), is a small, abundant rodent thought endemic to Mexico. We present a new record of this rat on Cocinas Island off the Chamela coast of Jalisco, Mexico. On this protected island located at 19.5°N, 105.1°W, we captured 11 specimens with the physical characteristics that confirm their identity as H. melanotis. We explore the possible implications of this species on Cocinas Island. 

Population and Community Responses of Small Mammals to Single-tree Selection Harvest in Laurentian Hardwood Forests

Small mammals are ubiquitous members of vertebrate communities that are sensitive to habitat change. In the Great Lakes region of North America, small mammal communities have changed rapidly, but experimental tests of potential mechanisms are lacking. Using a before-after, control-treatment design, we quantified the response of small mammals to single-tree selection harvest in Laurentian hardwood forests of Wisconsin, United States. We documented changes in forest structure and small mammal abundance, species diversity, and community similarity from silvicultural treatment. Treatment reduced tree density and canopy cover and increased mean tree diameter, woody stem density, variation in woody stem density, and volume of coarse woody debris. Peromyscus and northern short-tailed shrews (Blarina brevicauda) were dominant community members across treatments and years. White-footed mice (P. leucopus) outnumbered woodland deer mice (P. maniculatus gracilis) before treatment, but declined by almost fifty percent after treatment; deer mice and total rodent (i.e., Rodentia) abundances were unchanged. Small mammal species diversity increased twofold following treatment. Our experiment identified species-specific responses within Peromyscus to timber harvest: white-footed mice, the numerically dominant and generalist species, were most sensitive to habitat change, and their response produced cascading effects to small mammal community structure. Future experiments should assess these small mammal responses in a multi-year framework and quantify their effects on the broader vertebrate community.

Cryptosporidium spp. and Giardia spp. in wild rodents: using occupancy models to estimate drivers of occurrence and prevalence in native forest and exotic Pinus radiata plantations from Central Chile

The conversion of native forest to forestry plantations is a worldwide practice, affecting biodiversity and host-parasite interactions. One of the most common timber plantations in the world are monocultures of Monterey pine (Pinus radiata). Using occupancy models, we analyzed the occurrence and prevalence of Cryptosporidium spp. oocysts and Giardia spp. cysts in fecal samples of wild rodents from a landscape dominated by extensive Monterey pine plantations in central Chile. We aimed to assess drivers of parasite infection such as habitat type, abundance of rodent hosts, species richness, and season. Small mammals were sampled seasonally for two years in three habitat types: native forests, adult pine plantations and young pine plantations. A total of 1091 fecal samples from seven small mammal species were analyzed by coprological analysis. Occurrence probability of Cryptosporidium spp. and Giardia spp. was similar for the most abundant rodent species (Abrothrix longipilis, A. olivacea, and Oligoryzomys longicaudatus) and for all habitat types. For Cryptosporidium spp., variation in prevalence was mostly explained by season with higher prevalence during winter season and lower during spring. For Giardia spp., the prevalence was significantly higher in young pine plantations, followed by adult pine plantations and native forests. In addition, higher prevalence of Giardia spp. was associated with lower host richness, suggesting a possible dilution effect. Our findings reveal that Monterey pine plantations increase Giardia spp. transmission among rodents, but has no clear effect on Cryptosporidium spp., providing evidence that the impact of land use on parasitism can be idiosyncratic. Since both parasites have zoonotic potential, our findings may be useful for land use planning and management considering health issues.

Whole-genome sequencing analysis of wild house mice (Mus musculus) captured in Madagascar.

In Madagascar, the house mouse (Mus musculus) is widely believed to have colonized with human activities and is now one of the most abundant rodents on the island. However, its genetic background at the genomic level remains unclear, and clarifying this would help us to infer the timing of introduction and route of migration. In this study, we determined the whole-genome sequences of five Madagascar house mice captured from an inland location in Madagascar. We examined the genetic background of samples by analyzing the mitochondrial and autosomal genomes. We confirmed that the mitochondrial genome lineages of collected samples formed a single clade placed at one of the most basal positions in the Mus musculus species. Autosomal genomic sequences revealed that these samples are most closely related to the subspecies M. m. castaneus (CAS), but also contain a genetic component of the subspecies M. m. domesticus (DOM). The signature of a strong population bottleneck 1,000-3,000 years ago was observed in both mitochondrial and autosomal genomic data. In a comparison with global samples of M. musculus, the Madagascar samples showed strong genetic affinity to many CAS samples across a wide range of Indian Ocean coastal and insular regions, with divergence time estimated as around 4,000 years ago. These findings support the proposition that the ancestors of these animals started to colonize the island with human agricultural activity and experienced a complex history during their establishment.

Increased Prevalence of Lassa Fever Virus-Positive Rodents and Diversity of Infected Species Found during Human Lassa Fever Epidemics in Nigeria.

ABSTRACTThe dynamics of Lassa virus (LASV) infections in rodent reservoirs and their endemic human caseloads remain poorly understood. During the endemic period, human infections are believed to be associated with the seasonal migration of Mastomys natalensis, thought to be the primary reservoir that triggers multiple spillovers of LASV to humans. It has become imperative to improve LASV diagnosis in rodents while updating their prevalence in two regions of Lassa fever endemicity in Nigeria. Rodents (total, 942) were trapped in Ondo (531) and Ebonyi (411) states between October 2018 and April 2020 for detection of LASV using various tissues. Overall, the LASV prevalence was 53.6%. The outbreak area sampled in Ondo had three and two times higher capture success and LASV prevalence, respectively, than Ebonyi State. This correlated with the higher number of annual cases of Lassa fever (LF) in Ondo State versus Ebonyi State. All rodent genera (Mastomys, Rattus, Crocidura, Mus, and Tatera) captured in both states showed slightly variable LASV positivity, with Rattus spp. being the most predominantly infected (77.3%) rodents in Ondo State versus Mastomys spp. (41.6%) in Ebonyi State. The tissues with the highest LASV positivity were the kidneys, spleen, and testes. The finding of a relatively high LASV prevalence in all of the rodent genera captured highlights the complex interspecies transmission dynamics of LASV infections in the reservoirs and their potential association with increased environmental contact, as well as the risk of zoonotic spillover in these communities, which have the highest prevalence of Lassa fever in Nigeria.IMPORTANCE Our findings show the highest LASV positivity in small rodents ever recorded and the first direct detection of LASV in Tatera spp. Our findings also indicate the abundance of LASV-infected small rodents in houses, with probable interspecies transmission through vertical and horizontal coitus routes. Consequently, we suggest that the abundance of different reservoir species for LASV may fuel the epizootic outbreaks of LF in affected human communities. The high prevalence of LASV with the diversity of affected rodents has direct implications for our understanding of the transmission risk, mitigation, and ultimately, the prevention of LF in humans. Optimal tissues for LASV detection in rodents are also presented.

Invasive brown treesnakes (Boiga irregularis) move short distances and have small activity areas in a high prey environment

Animal movements reflect temporal and spatial availability of resources as well as when, where, and how individuals access such resources. To test these relationships for a predatory reptile, we quantified the effects of prey abundance on the spatial ecology of invasive brown treesnakes (Boiga irregularis) on Guam. Five months after toxicant-mediated suppression of a brown treesnake population, we simultaneously used visual encounter surveys to generate relative rodent abundance and radiotelemetry of snakes to document movements of surviving snakes. After snake suppression, encounter rates for small mammals increased 22-fold and brown treesnakes had smaller mean daily movement distances (24 ± 13 m/day, overline{x } ± SD) and activity areas (5.47 ± 5 ha) than all previous observations. Additionally, snakes frequenting forest edges, where our small mammal encounters were the highest, had smaller mean daily movement distances and three-dimensional activity volumes compared to those within the forest interior. Collectively, these results suggest that reduced movements by snakes were in part a response to increased prey availability. The impact of prey availability on snake movement may be a management consideration when attempting to control cryptic invasive species using tools that rely on movement of the target species to be effective.

ZoonosisImpact of Rodent Outbreaks in Rice Paddies on Incidence of Rodent-borne Zoonosis in Human Populations

A study conducted in an area encircled by rice paddies on a rodent abundance, population, and flea vector index during normal and rodent outbreak periods revealed that the rodent populations of rice paddies were colonised in rice fields and are not migrated much to the residential areas even during the outbreak years. The predominance of Rattus rattus (94.2%) was recorded among the rodent species in residential premises, whereas in rice paddies, it was lesser bandicoot Bandicota bengalensis (98.9%). Among the structures in a residential area, bakeries were the most infested with pest rodents followed by grocery and vegetable stores. The recorded rat flea index of below 1 from the animals trapped in residential premises and no progression in fever and other ill health conditions among the residents even during field rodent outbreak years show no risk of zoonotic diseases like plague. Rodenticide poison offered through liquids has recorded high intake and control success over the market available ready-to-use bait cakes.

A global evaluation of the associations between long-term dynamics of seed falls and rodents.

One classic system of pulsed resource and animal population is mast seeding and population dynamics of seed-eating rodents in forests. However, we still lack an understanding of the global patterns regarding the contributions of seed falls to rodent outbreaks or population dynamics. We analyzed a global dataset of coupled long-term time series of seed abundances and rodent populations from published literature, including 66 and 89 time series (156 rodent-seed pairs from 37 studies) for rodent and seed abundances, respectively. We found only half of the examined rodent populations showed statistically significant coincidence between rodent outbreak and mast-seeding years. Over all the coupled time series, seed abundance was found to positively correlate with rodent abundance with a one-year lag, and the relative importance of seed abundance was much lower than that of density dependence in affecting rodent population growth rates. We also found the relative importance of seed abundance decreased, but that of rodent density dependence increased with the latitude of study. For the first time, our work provides a global pattern on the associations between seed falls and rodent population dynamics mostly in mid- and high-latitude forests, and highlights the necessity of more long-term studies on this subject in more forest ecosystems.

Socio-environmental changes and rodent populations in lowland agroecosystems of the lower delta of the River Senegal, West Africa: results of observations over a decade, 2008-2019

In the context of food self-sufficiency, the River Senegal Valley has been undergoing profound environmental changes for several decades. Rice production has increased due to the development of vast irrigated perimeters, which has been accompanied by recurrent proliferations of rodent populations that are crop pests and reservoirs of zoonoses. The aim of our study was to determine the factors underlying these phases of increased rodent abundance over a ten-year (2008 to 2019) sampling period during the hot dry season (February-May). A total of 1,867 rodents of four species were captured, among which Arvicanthis niloticus and Mastomys huberti dominated. Our results showed that, during this season, rodent abundance (i) increases significantly with rainfall from the previous year, (ii) is higher in cultivated than in uncultivated plots, (iii) increases with plant cover, (iv) increases, for M. huberti, with the presence of open water. We showed that in an area that was first sparsely cultivated and then impacted by hydro-agricultural rehabilitation of irrigation and drainage infrastructure, the abundance of A. niloticus changed following this program, reaching the level of a nearby area that has been intensively cultivated for decades. Moreover, we showed that the proportion of adults among the captured individuals was lower in rice plots than in vegetable gardening fields and uncultivated plots. The breeding pattern of adult individuals was also affected by land use. Results suggest that uncultivated areas and vegetable gardening fields constitute refuge and breeding ground hotspots and would thus form a starting point for the invasion of rice fields. Following these results, we advocate for regular monitoring of rodent breeding and abundance patterns, with a special focus on these refuge areas, particularly during the hot dry season. We recommend implementing effective and sustainable science-based control strategies at national and community levels to keep rodent populations within tolerable limits.

Niche overlap in rodents increases with competition but not ecological opportunity: A role of inter-individual difference.

Niche variation at population level mediates niche packing (i.e. patterns of species' spread within the niche space) and species coexistence at community level. Competition and ecological opportunity (resource diversity) are two of the main mechanisms underlying niche variation. Dense niche packing could occur through increased niche partitioning or increased niche overlap. In this study, we used stable carbon and nitrogen isotope data of 635 individual rodents from four species across nine sites in the montane region of a subtropical island to test the effects of competition and ecological opportunity on population isotope niche size, inter-individual niche difference within population and interspecific niche overlap within community. We used the Bayesian Standard Ellipse Area (SEAB, the ellipse area enclosed by carbon and nitrogen isotope values of organisms on a bi-plot) to estimate population niche size and interspecific niche overlap. Inter-individual niche difference within population was quantified as isotopic divergence and isotopic uniqueness. We used rodent abundance (the number of unique individuals captured) to measure competition and plant isotope niche size (plant SEAB) to measure ecological opportunity. The rodents experienced competition as evidenced by a negative relationship between population change rate and conspecific abundance. Rodent population niche size increased with ecological opportunity but not competition. The inter-individual niche difference (isotopic uniqueness) increased with competition (interspecific competition only) but not ecological opportunity. At community level, interspecific niche overlap (herbivore-omnivore pair only) increased with competition (the combined abundance of the pair) but not ecological opportunity. This study demonstrated that isotope niche variation of the rodents could be hierarchically influenced by ecological opportunity and competition, with the former setting the limit of population niche size across communities and the latter shaping inter-individual niche difference and interspecific niche overlap within communities. Under strong intraspecific competition and limited ecological opportunity for niche expansion, individuals may choose to increase their isotopic uniqueness from conspecifics at the cost of overlapping with heterospecifics of different trophic roles within the community niche space as overall competition increases. Denser niche packing of these rodent communities might be achieved through increased niche overlap.

Determinants of the relative abundance of rodents in landscapes dominated by Eucalyptus plantations

Abstract Forestry plantations have increased considerably over recent decades to fulfil human demand for wood, pulp and paper. Eucalyptus globulus Labill is one of the most abundant plantation species, particularly in Europe, where its largest presence is in Portugal. Furthermore, plantations in Mediterranean areas, such as Portugal, frequently suffer from forest fires, and thus it is crucial to understand their impacts on vertebrates. This is especially relevant for some species, like small mammals, that use landscapes at smaller scales for which even small changes in forest cover may have a profound effect. In this study, we evaluate the effects of several environmental, disturbance and habitat drivers on the relative abundance of rodents (Muridae) in Eucalyptus plantations in central Portugal. Specimen capture took place across two seasons and at eight study sites representing six different stages of Eucalyptus plantations and two native forests from 2019 to 2020. Using a structural equation modelling approach, we show that the relative abundance of rodents was promoted by recent wildfire events and was higher in areas where carnivores and wild boar were more abundant. By contrast, abundant deer and increased percentages of herbaceous or litter cover and bare soil limited the abundance of rodents. We did not detect a significant relationship between Eucalyptus plantations and the relative abundance of rodents. The presence of other species, either by direct contact (carnivores) or by inducing habitat changes (ungulates), and vegetation structure, likely linked to plantation management or fire regime, are the more important factors dictating the population dynamics of rodents across plantation forests in central Portugal.

Biotic resistance in a stochastic world: Do rodents act as a filter to alien tree invasion in pampean old fields?

AbstractBiotic resistance from post‐dispersal seed predators has been shown to influence invasion and spread of woody plants in grasslands and savannas. Yet, the role of rodent granivores as a barrier to woody plant invasion remains poorly studied. We examined the impact of rodent exclusion and canopy disturbance on two exotic tree seedling establishment (Gleditsia triacanthos and Robinia pseudoacacia) in an old‐field grassland of the Inland Pampa, Argentina. The experiment was conducted over 4 years with substantial climatic variation, which affected both rodent abundance and seedling performance. Our results showed that, for both tree species, rainfall was the main factor affecting both seedling emergence and survival, while the effect of rodent seed predation and disturbance depended on variability in natural rodent density. The response of G. triacanthos seedling emergence after the onset of favorable water conditions was more rapid than the recovery of rodent populations. This delay provided an opportunity to escape from potential seed predation, reducing its importance as a biotic filter to woody invasion. Robinia pseudoacacia seedlings emerged during the first growing period and died because of hydric stress, while remnant seeds did not remain viable in the seed bank after 2 years of sowing. From our results, we suggest that the dynamic of tree invasion depends highly on climatic variability, which has direct effects on seed germination and survival, as well as effects mediated by rodent abundance and herbaceous competition.

Masting benefits seedling recruitment of Armeniaca sibirica through directed dispersal by rodents

In animal-dispersed plants, masting is often claimed to promote fitness through increasing seed survival (e.g., predator satiation hypothesis) and/or seed dispersal (e.g., predator dispersal hypothesis). Plant fitness is also enhanced when seeds are disproportionally deposited at the safe sites by animals in spatially heterogeneous environments (i.e., directed dispersal hypothesis). However, little is known about the relationship between masting and directed dispersal in animal-dispersed plants. Here, we tracked seed production, seed dispersal and seedling establishment of a rodent-dispersed plant (Armeniaca sibirica) from 2005 to 2017 in a warm-temperate forest in northern China. We hypothesized that masting would improve seed dispersal fitness through directed dispersal mediated by small rodents. Compared to the null model of random dispersal, more seeds were deposited at the safe sites and more seedlings were established from the safe sites in seed-rich years, indicating that directed dispersal occurred in the masting years. The proportions of seed deposition and seedling establishment at the safe sites were positively associated with seed abundance and seed-rodent ratio, suggesting that masting increased directed dispersal effects. Overall, seed abundance was better in predicting directed dispersal effects than rodent abundance or seed-rodent ratio. Beyond the most commonly considered advantages of predator satiation and predator dispersal, our results are the first to suggest that masting is beneficial for seed dispersal through directed dispersal mediated by animals. This finding might contribute to a better understanding of masting effects on plant recruitment.

Differential Responses of Small Mammals to Woody Encroachment in a Semi-Arid Grassland

Encroachment by woody invasive plants is a major threat to grasslands and savannah ecosystems worldwide. Rodents, being primary consumers, are likely to be the first to respond to changes in the structure and composition of native vegetation. We examined the effect of an invasive shrub Prosopis juliflora (hereafter Prosopis) on the native rodent community of an arid grassland system of Western India. Our sampling plots were divided into five categories representing different stages of Prosopis invasion and other land cover types. These consisted of restored native grassland, agriculture fallow, open brushland, sparse-Prosopis plots, and Prosopis-dominated plots. We also examined the impact of woody invasion on the response of native rodents toward moonlight and temperature. As hypothesized, we found a significantly higher abundance of rodent species in the native grassland habitat compared to sparse-Prosopis habitats. However, there was no significant difference in rodent abundance and diversity between the grassland and Prosopis-dominated habitats. Thus, species richness and abundance of rodents were the highest in the restored grasslands and dense Prosopis thickets, and the lowest in the sparse Prosopis, potentially showing a “U” shaped response to Prosopis invasion. We observed a species-specific effect of Prosopis on the activity of Tatera indica, Bandicota bengalensis, and Millardia meltada. Habitat type mediated the effect of different environmental factors (moonlight and temperature) on the activity of the most commonly ocurring species T. indica while activity of M. meltada showed a weak association with environmental factors. B. bengalensis was the most generalist species showing similar activity across all habitat types. Thus, the impact of Prosopis invasion on the rodent community was uneven, and depended on species as well as on local environmental characteristics.

Composition, abundance and distribution of rodent species in Alemsaga Priority State Forest and farmlands, northwestern Ethiopia

AbstractThe aim of this study was to investigate species composition, relative abundance, habitat preference and seasonal variations of rodents in Alemsaga Priority State Forest and the nearby farmlands. A total of 1311 individual rodents were captured in six permanent grids and line transects, comprising of nine species, namely Lophuromys simensis, Arvicanthis abyssinicus, Desmomys harringtoni, Mastomys natalensis, Stenocephalemys albipes, Rattus rattus, Arvicanthis dembeensis, Mus musculus and Acomys cahrinus. Hystrix cristata and Tachyoryctes splendens were also recorded but not captured in trapes. About 44.4% of captured species are endemic to Ethiopia. Lophuromys simensis was captured from all habitats, while Acomys cahrinus was recorded only in Carissa land. The highest abundance of rodents was recorded in crop fields and the lowest in Carissa land. The overall trap success was 14.76%. Statistical variation was observed between individual rodent species among different habitats. Highest rodent populations were recorded during the wet season. Females comprised more individuals than males. Adults outnumbered sub‐adults and juveniles. Vegetation composition, altitudinal variations and human disturbance were the major factors affecting the distribution of rodents in the area. Attention should be given by the local administrators to conserve the area.