Native Small Mammals Research Articles

Tracking native small mammals to measure fine-scale space use in grazed and restored dry woodlands

The degradation of dry woodlands in South America by agricultural activities affects wildlife through a decrease in available habitat and fine-scale changes in habitat structure. The impact of land use can be perceived by small, mobile organisms as preventing or facilitating their movement through and among habitats, consequently altering ecosystem functions. By tracking with radiotelemetry we describe for the first time the pattern of movement of a small mammal (Graomys griseoflavus) that inhabits dry woodland ecosystems in South America and its relationship with environmental features that affect movement. We measured environmental variables linked to the ecological requirements of the species (e.g., plant cover and patches of forage species consumed) in restored and grazed woodlands and compared movements between seasons (dry and wet). We found that the fine-scale differences in the vegetation cover associated with livestock grazing changed the mobility and use of space of this small mammal. The step-lengths and used area for G. griseoflavus were greater under passive restoration compared to the area grazed by livestock. Small rodents moved between patches of similar mean size of forage species, avoiding large inter-patches of bare ground. Although both management conditions showed seasonal variations in plant cover, the step-lengths decreased significantly in the grazed woodland during the wet season, while step-lengths in the restored area were unaffected by season. The fine-scale spatial arrangement of plants in restored woodlands elucidated notable changes in animal movement on grazed lands, suggesting that space use by small mammals may be an important tool to identify habitat structures that facilitate the movement of animals in restoration of degraded systems.

Factors influencing the residency of bettongs using one‐way gates to exit a fenced reserve

AbstractUnderstanding the conditions under which small native Australian mammals can persist in the presence of introduced predators remains a key challenge to conservation ecologists. Bettong‐specific one‐way gates were used at a predator‐free reserve in South Australia to allow the burrowing bettong (Bettongia lesueur) – a small potoroid, listed as ‘vulnerable’ nationally – to disperse out of the reserve. We conducted a field experiment to explore the conditions affecting residence time of bettongs that left the reserve. We monitored bettong and mammalian predator activity outside the fence using track surveys across 18 sites over two seasons. We examined the effect of supplementary feeding as a strategy for increasing residence time, as well as the influence of predator presence and habitat quality, using linear mixed models. Bettong activity was positively associated with supplementary feeding, midstorey vegetation cover and shelter availability. After gates were closed, bettong activity near gates declined to almost zero the following weeks, likely either due to death from predation or due to movement away from the sites. To a small extent, mammalian predators were more likely to be present at sites with high bettong activity. Further research on conditions to support persistence of burrowing bettongs and other small mammals, including understanding minimum necessary predator control effort, is required before successful establishment of populations outside of fences can occur.

Patterns of decline of small mammal assemblages in vegetation communities of coastal south-east Australia: identification of habitat refuges

Since European settlement Australian native mammals have experienced significant extinctions and severe declines in the range and abundance of populations. Longitudinal studies are required to identify declines and activate timely management. Population studies of native small mammal communities were conducted across the eastern Otway Ranges during 1975–2007; however, their subsequent status was unknown. We aimed to: compare the current occurrence and abundance of species and communities (2013–18) to those in previous decades across major vegetation communities (heathy woodland, low forest, sand heathland, headland scrub, coastal dunes and estuarine wetland), and identify change characteristics and management priorities. Live trapping was employed to assess mammals at 30 sites across seven vegetation communities. In total, 67% of sites exhibited large to severe decreases in abundance and only 3% of sites had more than four species compared to 27% in earlier decades. Declines occurred following wildfire and drought, with drivers likely to be multifactorial. While regional declines were significant, higher mammal abundance (two- to six-fold) and native species richness were recorded at coastal dune sites, indicating that this community provides important mammal refuges. Identification of refuges across the landscape and their protection from inappropriate fire and predators should be management priorities.

Populations of Small Mammals, Tallgrass Prairie and Prescribed Fire: A Fire-Reversal Experiment

We sampled small mammals in burned and unburned tallgrass prairie by using three sites in each of two contiguous ungrazed experimental fire-reversal treatments during 1999-2010. One of the experimental treatments (001A to R20A) had been burned in spring for >20 years and then was switched to an unburned research treatment after the spring fire in 2000. In contrast, the other treatment (020A to R01A) had been left unburned for 20 of 29 years before it was switched to an annually burned treatment beginning with the prescribed fire in spring 2001. Overall, we recorded 11 species of rodents and two of shrews for a total of 2,444 individuals. The white-footed mouse (Peromyscus leucopus) was the most abundant species followed by the hispid cotton rat (Sigmodon hispidus) and deer mouse (P. maniculatus). Of the seven common species (>25 individuals), six were strongly associated with one of the treatments, and several species showed positive associations with some part of the landscape within each treatment. Furthermore, white-footed mice, deer mice, prairie voles (Microtus ochrogaster), western harvest mice (Reithrodontomys megalotis) and Elliot's short-tailed shrews (Blarina hylophaga) showed significant temporal patterns of abundance in either R01A or R20A in one or both seasons (autumn or spring). Our study also supports a very important conservation message. That is, the white-footed mouse (a woodland species) and the hispid cotton rat (a colonizing species) were more numerically dominant than the most common rodent, the deer mouse, (a native prairie species) throughout the 10-year study. These observations demonstrate that areas not burned frequently allow encroachment by shrubs and then trees, which subsequently allow the white-footed mouse and hispid cotton rat to expand into these areas. Conversely, the stoppage of frequent fires ultimately degrades the mosaic of prairie habitats for native prairie small mammals [such as the deer mouse, prairie vole and western and plains harvest mice (R. montanus)] and these species move out as shrubs and trees become common. Visual observations indicate that the latter (degradation of native tallgrass prairie) occurs much more rapidly (potentially within a decade) than the restoration of native tallgrass prairie by the elimination of shrubs and trees by annual burning (potentially 50 or more years).

The short-term response of feral cats to rabbit population decline: Are alternative native prey more at risk?

The impacts of invasive predators can be amplified by high densities of invasive prey species. In Australia, hyper abundant rabbit populations lead to high densities of feral cats and correspondingly high impact of cats on native species, especially small mammals. Therefore, it would be expected reducing rabbits could also reduce abundance of cats, and thereby alleviate predation on native small mammals. However, cats might respond to the loss of rabbits by prey-switching to native small mammals, resulting in increased predation on those species. Our aim was to understand the short-term effects of an experimental reduction of rabbit abundance on feral cats and their small-mammal prey in arid South Australia. We reduced the rabbit population in a 37 km2 experimental enclosure by ~ 80%, while monitoring an adjacent unmanipulated area as a control. Cat activity and survival of VHF-collared cats in the enclosure decreased by 40% following the rabbit reduction. Surviving cats increased their consumption of reptiles, birds and invertebrates, but they nevertheless evinced hunger by increased intake of experimentally-supplied sausages. There was no change in either the proportion of cat scats that contained remains of small mammals, or the rate at which video-collared cats were recorded killing small mammals, even though the activity of small mammals declined. Our results demonstrate that individual feral cats prey-switch in response to removal of their primary prey. However, we also show that survival and overall activity of cats decreased, which could result in net, long-term benefits for native prey threatened by cats. Management of feral cats using food lures or baits would also be more effective when introduced prey are scarce, as cats are more likely to eat novel food.

Unexpectedly high densities of feral cats in a rugged temperate forest

Effective invasive predator management requires accurate knowledge of population density. However, density can be difficult to estimate for wide-ranging, cryptic and trap-shy species, such as the feral cat Felis catus. Consequently, few density estimates exist for this invasive predator of global significance, particularly from rugged, mesic or structurally complex habitats where detection is challenging. In this study, we estimated feral cat density in the wet forests and cool temperate rainforests of the Otway Ranges, south-eastern Australia, to (1) provide a density estimate for this rarely surveyed habitat type, and (2) verify predictions from a continental-scale model of feral cat density. We deployed 140 camera traps across two independent 49km2 grids and identified individual feral cats based on unique pelage markings. Using spatially explicit mark-resight models, we estimated that there were 1.14 cats km−2 (95% CI: 0.89–1.47). This is more than three times the average cat density in natural environments across Australia, and at least five times higher than model-based predictions for the Otway Ranges. Such high densities of feral cats likely reflect the abundance of small native mammals and lack of apex predators in our study area. Our findings contradict the widespread assumption that feral cats occur at very low densities in mesic and rugged habitats. Underestimating the density of feral cats in these environments has significant implications for pest animal management and biodiversity conservation.

Limits to alien black rats (Rattus rattus) acting as equivalent pollinators to extinct native small mammals: the influence of stem width on mammal activity at native Banksia ericifolia inflorescences

Alien species are a major cause of species extinctions globally and the effects of introductions can become substantial, especially once aliens become entrenched and impossible to eradicate. Some entrenched aliens may assume niches of extinct native species that are functionally similar, but the capacity of an alien to perform specialised ecological processes is unknown. Here we examine the potential for the alien black rat (Rattus rattus) to effectively pollinate native Banksia ericifolia in heath at North Head, Sydney where endemic mammalian pollinators such as brown antechinus (Antechinus stuartii) and eastern pygmy-possums (Cercartetus nanus) had been locally extinct prior to recent reintroductions. Using artificial inflorescences, we compared the use of inflorescences, visit frequency and duration of alien black rats to reintroduced natives according to the stem diameter of the inflorescence. Black rats were the most frequent visitor and they spent similar or more time at artificial inflorescences as natives, but they also spent more time visiting inflorescences with thicker stem diameters. In contrast, the native mammals visited artificial inflorescences regardless of the stem thickness. We suggest that, as black rats are heavier than the native mammals, this could limit their capacity as substitute pollinators of B. ericifolia. This finding shows the importance of understanding the extent of the benefits of aliens before relying on them as functional replacements for extinct natives.

Genetic structure of an abundant small mammal is influenced by low intensity urbanization

Urban development can fragment and degrade habitat, and such habitat alterations can have profound effects on wildlife, including influencing population genetics. We used nine microsatellite loci to determine the effects of urbanization on genetic diversity and genetic structure in a native small mammal, Merriam’s kangaroo rat, in areas in and around Las Cruces, NM, an expanding low density urban center. We found that Merriam’s kangaroo rats in urban areas had increased genetic differentiation among populations as compared to wildland animals, and detected some evidence of lower genetic diversity in urban areas, indicating that the population genetics of a common and abundant wildlife species can be impacted by low density urbanization. Our results suggest that although abundant and common wildlife such as Merriam’s kangaroo rats may persist in urban environments, these animals may still be influenced by more subtle effects of urbanization, such as genetic isolation.

Minimal Spillover of Native Small Mammals From Bornean Tropical Forests Into Adjacent Oil Palm Plantations

In the face of rapid tropical agricultural expansion, preservation of tropical forest remnants is crucially important. Forest remnants often abut the edges of new or established plantations, so landscape-level conservation requires an understanding of the balance between ecosystem services and disservices provided by forest, including potential crop yield reductions caused by species such as rodents, an important pest group in oil palm plantations. However, very little is known about the scale of any spillover of native species which inhabit forest into adjacent agricultural areas. We examined the distribution and behaviour of small mammals across an edge separating logged tropical forest and oil palm plantations in Sabah, Malaysian Borneo, using a dual approach. We used a trapping grid to reveal patterns of species relative abundance across the forest-plantation edge, and tracked individuals of forest species using a spool-and-line. We uncovered little evidence that the native forest small mammal community crosses the edge and uses the plantation, although two invasive small mammal species were found across the whole edge gradient. Of 10 forest species detected, we found only the adaptable murid Maxomys whiteheadi in the plantation, where it persisted at low abundances across all sampling points, including in the plantation interior control site. This pattern is more consistent with persistence of M. whiteheadi throughout plantations than with spill-over from forest fragments. On the forest side, observed species richness of small mammals increased with distance into the interior, suggesting a negative edge effect may exist within forest remnants. Of 23 successfully tracked small mammals, only one M. whiteheadi crossed the forest-plantation edge, and overall, this species was significantly repelled from crossing into plantation habitat. Our results suggest that spillover of native small mammals contributes little to oil palm damage close to forest-plantation edges, but that oil palm negatively impacts small mammal populations within adjacent forest remnants.

Assessment of potential impact of domestic cats on small mammals in a protected insular area

Abstract The presence of domestic cats in natural areas is considered one of the main reasons for species loss, especially on islands and among native small non-volant mammals, birds and reptiles. However, in this study, we detected values opposite to those expected for species richness, abundance, and diversity among different areas when considering the presence or absence and density of these felines. We also observed that in the evaluated environments, prey availability did not influence consumption of small mammal species. Our results reinforce the theory of domestic cats’ behaviour as being opportunistic and generalist predators. In addition, we only recorded the presence of exotic species in the faeces of cats; that is, we did not capture exotic species in the traps. The close relationship between these exotic species and anthropogenic environments indicates that felines are likely hunting in areas close to the homes where they live. Assessing the impact of predation by domestic cats on native fauna is important for the development and implementation of strategic resource management and to minimize long-term impacts.

Changes in small native animal populations following control of European rabbits (Oryctolagus cuniculus) by warren ripping in the Australian arid zone

Context European rabbits have a great impact on native vegetation and small vertebrates in Australia. Rabbits consume vegetation and promote invasive plants and invasive predators, and compete directly and indirectly with native animals suppressing those populations. Aims We explored the changes in small native vertebrates and invertebrates following the removal of rabbits. Methods Warren ripping was undertaken on a property in south-western Queensland at four sites and the results of pitfall trapping were compared with four nearby paired control sites. Invertebrates and small mammals were counted in pitfall traps, and bird surveys were conducted in all treatment and control sites. Key results Following a rabbit-control program, we observed a four-fold increase in the number of dunnarts trapped in treatment plots, whereas no change was observed in control plots. The spring following the rabbit-control program also saw an increase in some lizards in treatment plots. Conclusions The presence of rabbits in arid-zone Australia can suppress native animal populations. Implications Many species of small native mammals and lizards rely on food sources that fluctuate greatly with environmental conditions. The presence of rabbits altering the landscape, supporting introduced predators, reducing vegetation and, therefore, insects, adds increased pressure for insectivorous species. Rabbit control through warren ripping in arid-zone Australia is an effective method to reduce rabbit numbers, and allowed for an increase in small vertebrates in treated areas.

Zonation of a small mammal community within coastal dunes

Zonation is a dominant feature of coastal ecologies, yet comparatively few studies are available on zonation of ecological assemblages in coastal dunes. Studies of zonation often focus on invertebrate macrofauna in the sub or inter-tidal regions; rarely has zonation of small mammal communities been considered in dunes. In this study we use 10 years of mammal trapping data and show that a diverse small mammal community was present within a coastal dune system. Nine species were captured within the dune, only one of which was introduced. The invasive house mouse was limited to a narrow band above the beach/dune interface, while the native small mammal assemblage dominated in the rest of the dune field. This clear zonation may result from habitat preference, interspecific competition, predation, species-specific predator risk tolerances, marine or beach subsidies or a combination of these influences. We demonstrate the conservation value of dune systems and highlight the presence of zonation within a mobile small mammal community.

Urban green area provides refuge for native small mammal biodiversity in a rapidly expanding city in Ghana.

Urbanization is a key driver of global biodiversity loss. Although sub-Saharan African countries are experiencing unprecedented urbanization and urban expansion, very little is known about how this impacts tropical biodiversity. Here, we assessed the effects of urban expansion and urban green space on local small mammal species diversity in Accra, Ghana. We surveyed small mammals in the University of Ghana botanical garden, an urban green area (UGA) and adjoining built-up environment (BE) and compared the results with baseline data (BLD) collected when large areas of the current city still remained mostly undeveloped. The methodology involved live-trapping using Sherman collapsible live-traps. Our data showed higher small mammal abundance and diversity in the UGA than BE. Similarity of species composition was higher between UGA and BLD than between BE and BLD. The small mammal species captured in BE (the rodents Mastomys erythroleucus, Rattus rattus, and Arvicanthis rufinus, and the shrew Crocidura olivieri) are known to easily adapt to human-modified landscapes. Our results suggest that urbanization negatively influenced the abundance, diversity, and community composition of small mammals. Efforts should be directed towards the integration of urban green areas into urban land development planning in developing countries in order to conserve local wildlife and ecological services that enhance the quality of urban life.

The chronology and environmental context of a cave deposit and associated faunal assemblage including megafauna teeth near Wee Jasper, southeastern Australia

A limestone cave on the lower slopes of the southeastern Australian high country reveals a deep, stratified deposit dated from ca. 14,000 to 2000 cal. BP and rich in predominantly non-cultural faunal remains. Located in a sensitive ecological area between the Australian Alps and the Southern Tablelands, the site provides a valuable chronological archive for the interpretation of local environmental change using the faunal record as a proxy, in particular native rodents and other small mammals. Inferred palaeoenvironmental trends include the cessation of periglacial conditions in the surrounding ranges during the Terminal Pleistocene; a shift to warmer conditions and the establishment of forest and wetland habitats from around 13,500 to 10,000 cal. BP, with a significant decline in cold-adapted species at ca. 11,500 cal. BP and a period of significant taxon fluctuation and extinctions corresponding to a possible peak in warm and moist conditions (a ‘Holocene Optimum’), beginning around 8000 cal. BP and lasting perhaps 1500 to 2000 years. Complications to the relatively steady and continuous chronostratigraphy, formed from an AMS radiocarbon sequence from sedimentary charcoal, arose from the presence of several teeth of extinct sthenurine megafauna. These were resolved with direct U-series analysis to establish their much greater antiquity and comparison of the sthenurine teeth with teeth of extant macropodids from the same deposit through fluoride absorption analysis, which also identified the megafauna teeth as anomalous to the sequence. The site provides an important case study for the interpretation of megafauna remains in stratified sedimentary deposits, especially for sites that appear to contain evidence for the co-occurrence of megafauna and humans in primary contexts.

Exclusion of small mammals and lagomorphs invasion interact with human-trampling to drive changes in topsoil microbial community structure and function in semiarid Chile

Species losses and additions can disrupt the relationship between resident species and the structure and functioning of ecosystems. Persistent human-trampling, on the other hand, can have similar effects through the disruption of biocrusts on surface soils of semiarid systems, affecting soil stability and fixation of carbon and nitrogen. Here, we tested the interactive and synergistic impacts of the exclusion of native mammalian herbivores and the effects of introduced lagomorphs in a semiarid thorn scrub ecosystem, where soils were subjected to two different trampling intensities (i.e., trampled and non-trampled). We postulated that because of their differential habitat use and fossorial activities, with respect to native small mammals, lagomorphs would have strong negative effects on soil structure, biocrust cover, and biocrust bacterial community structure. Our expectations were that changes in biocrust cover in response to trampling where native mammals were excluded, but exotic lagomorphs were present, will spread their impacts on soil chemical and physical features. To test our hypotheses, we measured changes in soil biogeochemical properties in four experimental plots where lagomorphs (L)/small mammals (SM) were experimentally manipulated to exclude them from the plots (−), or let them be present (+). The experimental combinations monitored were: -L/+SM, -L/-SM, +L/+SM, and +L/-SM. Results showed that human-trampling disturbance interacted with the loss of native small mammals and the presence of non-native lagomorphs to cause large changes on biological (i.e., biocrust cover, bacterial and nifH genes abundance), physical (i.e., soil moisture and soil stability) and chemical (i.e., TC and TN) soil features. The relative impacts of trampling disturbance on biological and physicochemical features were strongly influenced by the presence of non-native lagomorphs. For example, larger decreases in biocrust cover and bacterial abundance were observed in treatments without lagomorphs (-L/+SM; -L/-SM). In turn, losses of biocrust cover, in addition to trampling, determined decreases in soil stability in all treatments. These results suggest that non-native lagomorphs surpass the effects of the loss of native small mammals in reducing soil quality and productivity. Therefore, human-trampling has the potential to convert low disturbed soils, as those observed in non-trampled soils in treatments -L/+SM, -L/-SM into poor soils with low biocrusts cover and concomitant low stability, as observed in +L/+SM; +L/-SM treatments. These findings agree with previous observations that different components of global change act in synergic ways in fragile, water-limited environments. Because biological invasions and soil surface disturbance are becoming widespread in dryland regions globally, understanding the long-term consequences of these interactions is essential.

The effect of wildfire on population dynamics for two native small mammal species in a coastal heathland in Queensland, Australia

The influences of wildfire through population dynamics and life history for two species of small mammals in a south-east Queensland heathland on Bribie Island are presented. Trapping results provided information on breeding, immigration and movement of Melomys burtoni (Grassland melomys) and Rattus lutreolus (Swamp rat). We first investigated and optimized the design of trapping methodology for producing mark-recapture population estimates to compare two adjacent populations, one of which was subjected to an extensive wildfire during the two year study. We consider how well rodents survive wildfire and whether the immediate impacts of fire or altered habitat have the greatest impact on each species. We found the R. lutreolus population was far more influenced by the fire than the M. burtoni population both immediately after the fire and over 18 months of vegetation recovery.

Species’ traits help predict small mammal responses to habitat homogenization by an invasive grass

Invasive plants can negatively affect native species, however, the strength, direction, and shape of responses may vary depending on the type of habitat alteration and the natural history of native species. To prioritize conservation of vulnerable species, it is therefore critical to effectively predict species' responses to invasive plants, which may be facilitated by a framework based on species' traits. We studied the population and community responses of small mammals and changes in habitat heterogeneity across a gradient of cheatgrass (Bromus tectorum) cover, a widespread invasive plant in North America. We live-trapped small mammals over two summers and assessed the effect of cheatgrass on native small mammal abundance, richness, and species-specific and trait-based occupancy, while accounting for detection probability and other key habitat elements. Abundance was only estimated for the most common species, deer mice (Peromyscus maniculatus). All species were pooled for the trait-based occupancy analysis to quantify the ability of small mammal traits (habitat association, mode of locomotion, and diet) to predict responses to cheatgrass invasion. Habitat heterogeneity decreased with cheatgrass cover. Deer mouse abundance increased marginally with cheatgrass. Species richness did not vary with cheatgrass, however, pocket mouse (Perognathus spp.) and harvest mouse (Reithrodontomys spp.) occupancy tended to decrease and increase, respectively, with cheatgrass cover, suggesting a shift in community composition. Cheatgrass had little effect on occupancy for deer mice, 13-lined ground squirrels (Spermophilus tridecemlineatus), and Ord's kangaroo rat (Dipodomys ordii). Species' responses to cheatgrass primarily corresponded with our a priori predictions based on species' traits. The probability of occupancy varied significantly with a species' habitat association but not with diet or mode of locomotion. When considered within the context of a rapid habitat change, such as caused by invasive plants, relevant species' traits may provide a useful framework for predicting species' responses to a variety of habitat disturbances. Understanding which species are likely to be most affected by exotic plant invasion will help facilitate more efficient, targeted management and conservation of native species and habitats.

Landscape trends in small mammal occupancy in the Makira–Masoala protected areas, northeastern Madagascar

Madagascar’s native small mammals (Tenrecidae and Nesomyinae) are understudied. To help fill these knowledge gaps, we analyzed 1,575 detections of small mammals obtained during camera-trap surveys at 7 sites in northeastern Madagascar (2008–2011) using single-season occupancy analyses in program PRESENCE. We estimated landscape occupancy and detection probabilities of tufted-tailed rats ( Eliurus spp.), red forest rats ( Nesomys spp.), greater hedgehog tenrecs ( Setifer setosus ), and common tenrecs ( Tenrec ecaudatus ) and examined how these parameters responded to habitat characteristics, habitat degradation, and the trap success of native and exotic carnivorans. Only Nesomys showed a marked difference in mean occupancy between intact (ψ = 0.71 ± SE 0.06), intermediately degraded (ψ = 0.23 ± SE 0.05), and degraded (ψ = 0.34 ± SE 0.06) forest sites. Only Nesomys and Setifer occupancy was strongly influenced by habitat characteristics; Nesomys occupancy was positively related to distance away from forest edge (β = 1.39 ± SE 0.27) and percent rainforest cover (β = 1.89 ± SE 0.39), and Setifer occupancy negatively related to average canopy height (β = −0.52 ± SE 0.25). We found trap success of exotic carnivorans had little influence on small mammal occupancy and detection probabilities (with the exception of Eliurus ). We suggest that camera traps are a valid method for studying aspects of small mammal ecology, but caution researchers to consider characteristics of camera traps (e.g., trigger speed) to increase potential inference.

Effects of cattle grazing on small mammal communities in the Hulunber meadow steppe.

Small mammals play important roles in many ecosystems, and understanding their response to disturbances such as cattle grazing is fundamental for developing sustainable land use strategies. However, how small mammals respond to cattle grazing remains controversial. A potential cause is that most of previous studies adopt rather simple experimental designs based solely on the presence/absence of grazing, and are thus unable to detect any complex relationships between diversity and grazing intensity. In this study, we conducted manipulated experiments in the Hulunber meadow steppe to survey small mammal community structures under four levels of grazing intensities. We found dramatic changes in species composition in native small mammal communities when grazing intensity reached intermediate levels (0.46 animal unit/ha). As grazing intensity increased, Spermophilus dauricus gradually became the single dominant species. Species richness and diversity of small mammals in ungrazed and lightly grazed (0.23 animal unit/ha) area were much higher than in intermediately and heavily grazed area. We did not detect a humped relationship between small mammal diversity and disturbance levels predicted by the intermediate disturbance hypothesis (IDH). Our study highlighted the necessity of conducting manipulated experiments under multiple grazing intensities.

Temporal fluctuation in shrub species preferences of two native rodents: The effect of infection status on habitat use

AbstractSmall mammals use plant species for gathering food resources and for shelter. Preferences for certain plant species are related to nutritional restrictions and behavioural patterns, which could be altered in the presence of an infectious disease. Several native small mammals are part of the wild cycle of the protozoan Trypanosoma cruzi, responsible for Chagas disease in humans. This is a vector‐borne disease transmitted by insects of the subfamily Triatominae. We examined the effect of T. cruzi infection status on the use and preference patterns of shrub species by two native rodent species: Octodon degus and Phyllotis darwini. This study was conducted during four sampling years (2010–2013) in a hyper‐endemic zone of Chagas disease located in a semiarid Mediterranean ecosystem. We captured individuals of 599 O. degus and 575 P. darwini (89% of the total captures), which were related to nine shrub species and examined for T. cruzi infection. In a community‐level analysis, infected and non‐infected O. degus used individual shrub species within the shrub community significantly non‐randomly relative to their availability; the same pattern was detected for non‐infected P. darwini individuals, whereas infected individuals used the shrub community according to the abundance of each shrub species. Examining individual preferences, both rodents showed a strong preference for Flourensia thurifera and Colliguaja odorifera regardless of their infection status. Preferences for specific shrub species were variable among years, showing a ‘core’ of preferred shrub species and variable levels of use of the remaining ones. Our results show that T. cruzi infection in wild small mammals can modify habitat use patterns and preferences for certain shrub species, probably affecting processes acting at community level.