Rodent Community Research Articles

Response of rodent assemblages to change in habitat heterogeneity in fruit-oriented nopal orchards in the Central High Plateau of Mexico

In the Central High Plateau of Mexico, perennial nopal (Opuntia spp.) orchards are used by several native rodent species. The effect of orchard aging on habitat heterogeneity and rodent assemblages are not known. I surveyed rodent community abundance, species richness, diversity and composition, and habitat heterogeneity (hab-H) in 3 nopal orchards—6 months (O1), 2 years (O2), and 12 years (O3) old—and 1 natural nopalera (NN). Hab-H increased with orchard age, and a unique rodent assemblage was associated with each nopal orchard. Grassland rodents dominated O1 and O2. The shrubby habitat of O3 supported a complex suite of rodents that included grassland and shrubland species, and the NN supported a rodent assemblage that was dominated by shrubland species. In O3, aging of the orchard had led to a hab-H and establishment of a rodent assemblage resembling that of NN. Similar ecological relationships are expected in other nopal orchards of the region. In view of my data, regional conservation efforts should take advantage of the mosaic of differently-aged nopal orchards, because they offer suitable conditions for different species of native rodents, particularly given that some of these species occupy natural habitats that are currently highly fragmented.

The role of phylogeny in desert rodent community assembly

Recent advances in molecular genetics and phylogenetic reconstruction have the potential to transform ecology by providing new insights into the historical evolution of ecological communities. This study by Stevens and collaborators complements decades of previous research on desert rodents, by combining data from a field study and a phylogenetic tree for Mojave Desert rodents to address patterns and processes of community assembly. The number of coexisting rodent species is positively correlated, and the average phylogenetic distance among these species is negatively correlated with perennial plant species richness. As rodent species diversity increases along a gradient of increasing environmental heterogeneity, communities are composed of increasingly related species: there is a consistent pattern of phylogenetic structure from over-dispersed through random to clumped. I discuss this pattern in the light of complementary results of previous studies. This paper is noteworthy for calling attention to still unanswered questions about how the historical events of speciation, colonization, extinction, and trait evolution and their relationship to past climates and vegetation have given rise to current patterns of community organization.

Comunidad de roedores en el municipio de san marcos, sucre, colombia

El objetivo de esta investigación fue determinar la composición de las comunidades de roedores en áreas urbanas y rurales del municipio de San Marcos, Sucre, Colombia. Los roedores fueron muestreados empleando trampas tipo Sherman desde diciembre de 2007 hasta julio de 2009, con un esfuerzo de captura de 1200 trampas-noche (éxito de captura 12%). Fueron capturados un total de 144 individuos, registrándose 8 especies: Mus musculus (60), Zygodontomys brevicauda (44), Rattus rattus (21), Oryzomys azuerensis (10), Oligoryzomys fulvescens (4), Neacomys spinosus (2), Proechiymys cayennensis (2) y Heteromys anomalus (1). El número de roedores murinos fue mayor en hábitats urbanos, mientras en ambientes rurales predominaron las especies silvestres de la subfamilia Sigmodontinae. Además, el mayor porcentaje de la población correspondió a machos adultos. Los resultados sugieren que las condiciones (homogeneidad y heterogeneidad) de los hábitats fueron determinantes en la distribución y diversidad de los roedores tanto en ambientes urbanos como rurales.

Consequences of Human Land Use for an Afro-alpine Ecological Community in Ethiopia

The Guassa area of Menz in the Central Highlands of Ethiopia is an Afro-alpine ecological community with an indigenous resource management system. The local community harvest different resources including collecting grass and firewood from the Guassa area. Cattle and other livestock are also grazed in the Guassa area, especially during the dry season. Several sympatric species of endemic rodents dominate the small mammal ecological communities in the Guassa area, and form most of the diet of the endangered Ethiopian wolf. This study aimed to determine if current levels of resource use by the local community through the indigenous resource management system had any discernible effect on rodent community structure. We found that the structure of the rodent community differs between habitat types, and that different species of rodents show diurnal variations in their patterns of activity. We also found that populations of different species show variable responses to each type of resource use in different habitats; some species show increases in abundance in relation to use while others show decreases. Although the indigenous resource management system was not specifically designed to conserve wildlife, it has nevertheless allowed wildlife, specifically small mammals or rodent communities, to co-exist alongside the ongoing resource use by the local community. We conclude the Guassa area represents an interesting model of community-led resource management of an Afro-alpine habitat which supports populations of endemic and threatened species.

Experimental treatment-control studies of ecologically based rodent management in Africa: balancing conservation and pest management

Context Rodent pests severely affect crop production, particularly in monocultures where one or two rodent pest species dominate. We predict higher species richness of native small mammal species in more heterogeneous mosaic (crop–fallow–bush) subsistence agro-ecosystems in Africa. Conservation and agro-ecological imperatives require that such diverse natural communities should be maintained and may benefit crop protection through limiting domination of pest species. Ecologically based rodent-management alternatives to rodenticides are urgently required and one such method (community trapping) is herein advocated. Aims To provide baseline information on rodent and shrew communities in agro-ecosystems in three African countries and to demonstrate efficacy of ecologically based rodent management (EBRM) in Africa (e.g. community household trapping). Methods Removal-trapping in a variety of agro-ecological habitats provided accurate small-mammal species lists. Intensive kill-trapping by rural agricultural communities was carried out experimentally where the efforts of communities were scientifically monitored by kill-trapping to measure impact on rodent numbers and the levels of post-harvest damage to stored grains. Key results Our study revealed a high diversity of endemic species in agricultural habitats in Tanzania and Namibia (but not Swaziland) and the existence of undescribed and possibly rare species, some of which may be at risk of extinction from unchecked habitat transformation for agriculture. Treatment-control studies showed that communities in three African countries could effectively reduce pest rodent populations and rodent damage by intensive trapping on a daily basis in and around the community. Conclusions Community trapping reduced pest rodent populations and damage to stored grains. Unlike the use of indiscriminate rodenticide, this practice is expected to have a negligible effect on beneficial non-target rodent and shrew species. Implications Ecologically based rodent management approaches such as community trapping will conserve beneficial non-pest rodent communities and ultimately improve crop protection.

On the nature of a paradoxical rodent community

On the nature of a paradoxical rodent community

Effect of Removal of Woody Biomass after Clearcutting and Intercropping Switchgrass (Panicum virgatum) with Loblolly Pine (Pinus taeda) on Rodent Diversity and Populations

Plant-based feedstocks have long been considered viable, potential sources for biofuels. However, concerns regarding production effects may outweigh gains like carbon savings. Additional information is needed to understand environmental effects of growing feedstocks, including effects on wildlife communities and populations. We used a randomized and replicated experimental design to examine initial effects of biofuel feedstock treatment options, including removal of woody biomass after clearcutting and intercropping switchgrass (Panicum virgatum), on rodents to 2 years post-treatment in regenerating pine plantations in North Carolina, USA. Rodent community composition did not change with switchgrass production or residual biomass removal treatments. Further, residual biomass removal had no influence on rodent population abundances. However,Peromyscus leucopuswas found in the greatest abundance and had the greatest survival in treatments without switchgrass. In contrast, abundance of invasiveMus musculuswas greatest in switchgrass treatments. Other native species, such asSigmodon hispidus, were not influenced by the presence of switchgrass. Our results suggest that planting of switchgrass, but not biomass removal, had species-specific effects on rodents at least 2 years post-planting in an intensively managed southern pine system. Determining ecological mechanisms underlying our observed species associations with switchgrass will be integral for understanding long-term sustainability of biofuels production in southern pine forest.

Ecological Aspects of Rodent Communities in Agrarian Ecosystems of Moldova

The transformations of anthropogenic ecosystems in the last decades provoked significant structural-functional changes in rodent communities, as well as modification of dominance status of some wide spread species. In the 80s the dominant species were those from genus Apodemus, with 63%, of which A. sylvaticus and A. uralensis had the abundance of 55%, being constant on the agricultural fields. The genus Mus species had the abundance of 25% and were the main species on agricultural fields. M. musculus was more frequent and more abundant (15%). After 2000 the abundance of some rodent species increased (A. agrarius, M. spicilegus) and of other species decreased (A. sylvaticus, A. uralensis M. musculus). In the last years abundance decreasing of M. spicilegus was registered. The Microtus vole population is in depression phase its abundance decreasing from about 20% in 2006 to 3% in 2009 and is still low. A. sylvaticus is the most prosperous species among rodents, being dominant and constant in the republic ecosystems.

Long‐term variations in rodent abundance in a rural landscape of the Pampas, Argentina

AbstractThe goal of this study was to analyze the variations in abundance of rodent communities over the last 24 years in a rural area, and their relation to possible changes in climatic variables and land use. The principal change in the area observed along the study period was an increase in the area covered by soybean. The habitats studied were crop fields and borders. The total abundance of rodents did not show a significant trend of variation over time in crop fields while in borders the abundance in autumn–winter (A–W) showed a significant trend to decrease over time. The different rodent species showed a differential response over time. While Calomys laucha and C. musculinus showed a decrease between the period before and after the soybean expansion, Akodon azarae did not change its abundance over time. The mean minimum temperature increased over time while the number of days with frost decreased. Total rodent abundance in A–W was positively associated with the cumulated precipitation of the previous spring–summer period and negatively with the cumulated precipitation of the same period. We conclude that rodent abundance variations in crop fields and borders of the study area are influenced by precipitation, but the observed trends of variation over time are better explained by changes in agricultural practices than by meteorological variables.

Design and application of group-specific oligonucleotide probes for detecting and monitoring mouse Clostridia

Clostridia dominate the rodent intestinal bacterial community and play an important role in physiological functions of the host. However, their ecology and diversity are still unclear. In our previous report, we showed that phylogenetically novel groups of clostridia inhabit the mouse intestine and contribute to the normalization of germfree mice. In this study, five new oligonucleotide probes were designed and applied to detect these clostridial groups that are essential for the normalization of germfree mice. Faecal microbiota of conventional mouse strains and specific pathogen-free mice from different breeding colonies were analysed by fluorescence in situ hybridization using these five probes. Our results showed that the composition of clostridia differed among mouse strains and also among mouse groups of the same inbred strain from different breeding colonies. These five new probes for mouse clostridia were able to detect the difference in clostridial diversity in each mouse group. In addition to Clostridium, we also analysed Bacteroides and Lactobacillus using previously described probes and the number or the frequency of occurrence of Bacteroides was shown to be different among mouse groups analysed. The oligonucleotide probe set including our newly developed and previously described probes used in this study can be applied to monitoring of significant groups of mouse intestinal microbiota.

Phylogenetic structure illuminates the mechanistic role of environmental heterogeneity in community organization

1. Diversity begets diversity. Numerous published positive correlations between environmental heterogeneity and species diversity indicate ubiquity of this phenomenon. Nonetheless, most assessments of this relationship are phenomenological and provide little insight into the mechanism whereby such positive association results. 2. Two unresolved issues could better illuminate the mechanistic basis to diversity begets diversity. First, as environmental heterogeneity increases, both productivity and the species richness that contributes to that productivity often increase in a correlated fashion thus obscuring the primary driver. Second, it is unclear how species are added to communities as diversity increases and whether additions are trait based. 3. We examined these issues based on 31 rodent communities in the central Mojave Desert. At each site, we estimated rodent species richness and characterized environmental heterogeneity from the perspectives of standing primary productivity and number of seed resources. We further examined the phylogenetic structure of communities by estimating the mean phylogenetic distance (MPD) among species and by comparing empirical phylogenetic distances to those based on random assembly from a regional species pool. 4. The relationship between rodent species diversity and environmental heterogeneity was positive and significant. Moreover, diversity of resources accounted for more unique variation than did total productivity, suggesting that variety and not total amount of resource was the driver of increased rodent diversity. Relationships between environmental heterogeneity and phylogenetic distance were negative and significant; species were significantly phylogenetically over-dispersed in communities of low environmental heterogeneity and became more clumped as environmental heterogeneity increased. 5. Results suggest that species diversity increases with environmental heterogeneity because a wider variety of resources allow greater species packing within communities.

Ecological change and the extinction of the Levantine Neanderthals: implications from a diachronic study of micromammals from Amud Cave, Israel

It has been hypothesized that the climate shift associated with the Heinrich 5 event (H5) and the decrease in productivity throughout MIS 4 contributed to the demise of Neanderthals from the Levant. The Middle Paleolithic stratigraphic sequence of Amud Cave (Israel) spans MIS 4 and the transition to MIS 3 and contains Neanderthal skeletal remains as well as microfaunal assemblages, often used in the literature as reliable paleoecological proxies. This combination offers a unique case study to address the question of the effects of climate on Neanderthal population dynamics. Here we present a diachronic study of the rodent assemblages from Amud Cave, Israel, using taphonomic and nested hierarchical paleoecological models to test the hypothesis of a decrease in environmental productivity throughout the Amud sequence. Results suggest that there is no change in high-level presence–absence and rank abundance of rodent species throughout the sequence of Amud Cave, but there is change in low-level relative abundance of four taxa. Paleoecological analysis suggests that while all the stratigraphic sub-units of Amud Cave can be assigned to a Mediterranean biome, an apparent trend of decrease in grasslands proportions throughout the sequence is discordant with other regional paleoecological proxies. Taphonomic analysis reveals that this may be attributed to specific predator preferences of rodent prey, and thus does not reflect the true shift in paleoecology throughout the temporal sequence represented in the cave. The high-level overall stability in rodent community suggests that climatic shifts during the MIS 4–3 transition were of a magnitude that did not have a major impact on small mammals in the region. Such results are consistent with evidence from analysis of large mammal community and vegetal remains in Amud and contemporaneous Middle Paleolithic cave sites, and suggest that climate change may not have had the hypothesized effect on Neanderthal extinction in the Levant.

Effects of Pinus armandii seed size on rodents caching behavior and it's spatio-temporal variations

Pinus armandii, a native pine species, has large (about 300 mg), wingless seeds, and distributes from central to western China at an altitude of 1000-3300 m. To determine how the seed size affects rodents caching behavior, tagged seed releasing and tracking experiments were conducted at 3 sites in Northwest Yunnan province in 2006 and 2007. Our data indicated that for all sites and both years, compared with the smaller seeds, the proportions of cached large seeds were significantly higher, whereas the consumed ones were significantly lower. Meanwhile, the mean and maximum values of caching distances were also significantly increased in large seeds. Seed fate was different between the two years and within the three sites as there have different rodent community compositions.

Tale of two metrics: density and biomass in a desert rodent community

Numerous studies have been made of rodent population and community dynamics, especially in arid ecosystems. Most have centered on understanding how total and species-specific densities of rodents change over time. The standing biomass each species contributes also is important to the energy available to the mesocarnivore community. Although density and standing biomass are related, how they might differ and if those differences are of importance to community structure and function have not received much attention. We analyzed 12 years of rodent density and body mass data from the Chihuahuan Desert in northern Mexico. Data were collected yearly in spring and fall from radial livetrapping webs. Total density and biomass changed significantly in a parallel manner from year to year, and both were related to precipitation and percent cover of grass and forbs. Based on density and biomass, the rodent community was dominated by 2 or 3 principal species. However, on a species-specific level, the numerically dominant species was a small-bodied granivore (Chaetodipus nelsoni), and a large-bodied folivore (Neotoma albigula) dominated in biomass. As total density increased, the proportion contributed by dominant species decreased. As total biomass increased, the proportion in the 2 dominant species increased and accounted for approximately 80% of total biomass. Over the 12 years of the study, species distributions based on density showed no directional change. In contrast, biomass of the rodent community gradually concentrated in a single, large-bodied folivore, N. albigula. Although total density and biomass responded similarly to precipitation and plant productivity, considerable differences between these 2 characteristics existed in their species-specific contributions to and changes within the community. The significance of these differences relative to foraging strategies and variable feeding opportunities within the community is discussed.

Effects of ENSO-linked climate and vegetation on population dynamics of sympatric rodent species in semiarid grasslands of Inner Mongolia, China

El Niño Southern Oscillation (ENSO) linked climate has been known to be associated with several rodent species, but its effects on rodent community at both spatial and temporal scales are not well studied. In this study, we investigated the possible causal chain relating ENSO, precipitation, temperature, and vegetation index (normalized difference vegetation index, NDVI) to rodent abundance for 14 sympatric rodent species in 21 counties of semiarid grasslands in Inner Mongolia, China, from 1982 to 2006. We found that both precipitation and temperature showed a generally direct positive effect on rodent abundance in many species in the current year, but indirect effects that operate through NDVI in the current or following year could have a reverse effect on abundance. We described one ENSO-linked precipitation bottom-up chain and three ENSO-linked temperature bottom-up chains. These observed bottom-up links reveal that in El Niño years, or 1 year after La Niña years, or 2 years after El Niño years, ENSO-driven climate or vegetation factors tend to increase population abundances of many sympatric rodent species in this region. We also found time-lag effects and the life-history strategy (i.e., functional groups of hibernating behavior, activity rhythm, or food habits) also contribute to the observed complicated effects of SOI on precipitation, temperature, NDVI, and ultimately rodent abundance.

Ecology of Hepaticola hepatica infection in rodents in southern West Siberia

The paper analyzes data of the long-term monitoring of Hepaticola hepatica (Bancroft, 1893) Hall, 1916 prevalence in rodents in subtaiga small-leaf forests of the Northern Baraba lowland (the Severnyi raion of Novosibirsk oblast). The study found that the prevalence was (10.4 ± 1.02)% in Arvicola terrestris L., 1758; 4.5% in Microtus agrestis L., 1761; 3.4% in M. oeconomus Pall.,1776; 1.4% in Clethrionomys glareolus Schreb., 1780; 1.0% in C. rutilus Pall., 1779; and 0.2% in Apodemus agrarius Pall., 1771. A. terrestris was shown to become dominant in rodent communities during its outbreaks and play the main role in completing the life cycle of the parasite. During low density of A. terrestris, the H. hepatica reservoir in the biocenosis is maintained by other rodent species.

Wildfires Alter Rodent Community Structure Across Four Vegetation Types in Southern California, USA

We surveyed burned and unburned plots across four habitat reserves in San Diego County, California, USA, in 2005 and 2006, to assess the effects of the 2003 wildfires on the community structure and relative abundance of rodent species. The reserves each contained multiple vegetation types (coastal sage scrub, chaparral, woodland, and grassland) and spanned from 250 m to 1078 m in elevation. Multivariate analyses revealed a more simplified rodent community structure in all burned habitats in comparison to unburned habitats. Reduction in shrub and tree cover was highly predictive of changes in post-fire rodent community structure in the burned coastal sage scrub and chaparral habitats. Reduction in cover was not predictive for the less substantially burned woodlands and grasslands, for which we hypothesized that interspecific competition played a greater role in post-fire community structure. Across vegetation types, generalists and open habitat specialists typically increased in relative abundance, whereas closed habitat specialists decreased. We documented significant increases in relative abundance of the deer mouse (Peromyscus maniculatus Wagner) and Dulzura kangaroo rat (Dipodomys simulans Merriam). In contrast, we found significant decreases in relative abundance for the California mouse (Peromyscus californicus Gambel), San Diego pocket mouse (Chaetodipus fallax Merriam), desert woodrat (Neotoma lepida Thomas), and brush mouse (Peromyscus boylii Baird). Currently, our research program involves assessment of whether habitat conservation plans (HCPs) in southern California provide long-term protection to HCP covered species, as well as preserve ecosystem function. The scenario of increased wildfires needs to be incorporated into this assessment. We discuss our results in relation to management and conservation planning under a future scenario of larger and more frequent wildfires in southern California.

Comparative characterization of mouse-like rodent communities in altitudinal belts of the Kuznetsk Alatau

The composition and structure of mouse-like rodent communities in altitudinal belts of the Kuznetsk Alatau Mountains are studied, and their comparative characterization is made. It is shown that the complex altitudinal-zonal differentiation of the mountain range leads to the formation of several types of mouse-like rodent communities: forest-steppe, dark coniferous-taiga, chern forests, and mountain tundra. The communities differ in species composition, structure, and total number. The main factors influencing the spatial distribution of species and their number are hydrothermal conditions, vegetation type, and anthropogenic transformation of the territory.

Guinean biodiversity at the edge: Rodents in forest patches of southern Mali

Southern Mali mainly belongs to the Sudanian savanna bioclimatic zone, but forest patches showing botanical affinities with Guinean humid forest remain as gallery forests or ravine forests. To characterize the rodent diversity of this area and check for the presence of some species of Guinean affinities in this group, rodent assemblages were sampled in four regions of southern Mali, using trapping and observational data in forest and surrounding habitats. Twenty-four species were recorded, comprising a representative sample of the expected overall diversity in this group according to rarefaction curves. Praomys rostratus was the dominant species in the most humid, closed lowland forest. Praomys daltoni was also present in this habitat type, being all the more abundant as habitat degradation was apparent. It became the dominant species in ravine forest on rocky substrate where P. rostratus was completely absent. In Sudanian savanna habitats and in herbaceous and cultivated areas, Mastomys erythroleucus dominated a diverse rodent community. A few species were found that testified for Guinean affinities of the most humid forest patches, especially in the extreme southeast of the country (region of Sikasso). Rodent assemblages of the Bafing and Mts Mandingues areas, in the western part of the study area, showed the highest similarity, in relation with environmental characteristics of this region representing an extension of the Fouta Djallon plateau in Guinea. The results obtained highlight the high biodiversity value of this forest-savanna mosaic, and provide new arguments in favour of the preservation of West African forest patches and their surrounding habitats.

Nonlinear effect of climate on plague during the third pandemic in China.

Over the years, plague has caused a large number of deaths worldwide and subsequently changed history, not the least during the period of the Black Death. Of the three plague pandemics, the third is believed to have originated in China. Using the spatial and temporal human plague records in China from 1850 to 1964, we investigated the association of human plague intensity (plague cases per year) with proxy data on climate condition (specifically an index for dryness/wetness). Our modeling analysis demonstrates that the responses of plague intensity to dry/wet conditions were different in northern and southern China. In northern China, plague intensity generally increased when wetness increased, for both the current and the previous year, except for low intensity during extremely wet conditions in the current year (reflecting a dome-shaped response to current-year dryness/wetness). In southern China, plague intensity generally decreased when wetness increased, except for high intensity during extremely wet conditions of the current year. These opposite effects are likely related to the different climates and rodent communities in the two parts of China: In northern China (arid climate), rodents are expected to respond positively to high precipitation, whereas in southern China (humid climate), high precipitation is likely to have a negative effect. Our results suggest that associations between human plague intensity and precipitation are nonlinear: positive in dry conditions, but negative in wet conditions.