Burrowing Activity Research Articles

Aspects of social behaviour and reproduction in the wild rabbit – Implications for rabbit breeding?

Further knowledge on aspects of social behaviour in the wild rabbit (Oryctolagus cuniculus), including the link to reproduction, could possibly point to new ways to improve housing and breeding conditions in rabbit farming. In this review, I present some results of our long-term study on a 2-hectare field enclosure population of wild rabbits (University of Bayreuth, Germany), exploring group-level and individual-level differences in agonistic behaviour of females and their potential associations with reproductive traits, including offspring survival. The frequency of agonistic behaviour in which females were involved, increased with increasing group size, and was lower in groups with a more heterogeneous age structure. At the individual level, reproducing females were involved in more agonistic interactions when groupmates gave birth and thus built their burrows and nests at around the same time, and higher-ranking mothers were particularly aggressive when other females approached close to their nursery burrows. Associations between females’ social environment and reproduction were evident, as the numbers of litters and offspring per female were lower at higher female densities, high-ranking females produced more offspring and had a lower offspring mortality than low-ranking ones, and cases of infanticide were lower in more stable groups, which we quantified by the more heterogeneous age structure of the females’ rank hierarchy in such groups. Furthermore, perinatal offspring mortality was increased in females with a delayed burrow and nest building activity, i.e. does that dug their nursery burrow and built their nest only during the last 24 h pre-partum, possibly driven by the more unfavourable social environment experienced by such females. Most importantly, our studies highlight the importance of the presence of litter siblings in improving an individual’s social environment, which resulted in an earlier onset of breeding in such females. Higher levels of positive social interactions with litter siblings were also associated with lower stress hormone (corticosterone) levels and with a better health status in terms of lower loads with an intestinal nematode. These findings on ameliorating effects of litter sibling presence in growing rabbits as well as in reproducing females may be a promising starting point worth further exploration in the context of group housing of domestic rabbits.

Classification of airborne multispectral imagery to quantify common vole impacts on an agricultural field.

BACKGROUNDThe common vole (Microtus arvalis) is a very destructive agricultural pest. Particularly in Europe, its monitoring is essential not only for adequate management and outbreak forecasting, but also for accurately determining the vole's impact on affected fields. In this study, several alternatives for estimating the damage to alfalfa fields by voles through unmanned vehicle systems (UASs) and multispectral cameras are presented. Currently, both the farmers and agencies involved in the integrated pest management (IPM) programs of voles do not have sufficiently precise methods for accurate assessments of the real impact to crops.RESULTSOverall, the four multispectral classification methods presented showed similar performances. However, the normalized difference vegetation index (NDVI)‐based segmentation exhibited the most accurate and reliable appraisal of the affected areas. Nevertheless, it must be noted that the simplest method, which was based on an automatic classification, provided results similar to those obtained by more complex methods. In addition, a significant direct relationship was found between the number of active burrows and damage to the alfalfa canopy.CONCLUSIONUnmanned vehicle systems, combined with multispectral imagery classification, are an effective and easily transferable methodology for the assessment and monitoring of common vole damage to agricultural plots. This combination of methods facilitates decision‐making processes for IPM control strategies against this pest. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Development of behavioral patterns in young C57BL/6J mice: a home cage-based study

Evidence exists that behavioral patterns only stabilize once mice reach adulthood. Detailed information about the course of behavioral patterns is of particular relevance for neuroscientific research and for the assessment of cumulative severity in genetically modified mice. The analysis considered five age groups focusing on behavioral assessments in the animals’ familiar home cage environment during the adolescence phase. We confirmed age- and sex-specific differences for several of the behavioral parameters and fecal corticosterone metabolites. Interestingly, an age-dependent decline in saccharin preference was detected in female mice. Regardless of sex, relevant levels of burrowing activity were only observed during later developmental phases. The development of nest complexity following the offer of new material was affected by age in female mice. In female and male mice, an age-dependency was evident for wheel running reaching a peak at P 50. A progressive increase with age was also observed for Open field activity. The data sets provide guidance for behavioral studies and for development of composite measure schemes for evidence-based severity assessment in young mice. Except for the burrowing test, the different behavioral tests can be applied in different age groups during post-weaning development. However, age- and sex-specific characteristics need to be considered.

Native herbivores indirectly facilitate the growth of invasive Spartina in a eutrophic saltmarsh.

Current theory (e.g., consumer-controlled theory) predicts that nutrient enrichment typically amplifies herbivory and thereby suppresses the growth and expansion of invasive plants. Herbivores can facilitate plant regrowth in the native community by stimulating complementary growth or ameliorating habitat conditions (e.g., by increasing soil oxygen and nutrient availability), but whether they have similar positive effects on invasive plants, especially under nutrient enrichment, remains unknown. Using a field nitrogen (N)-enrichment × crab exclusion experiment, we evaluated and compared the effects of both N enrichment and crab herbivory on the growth performance of a global invasive cordgrass, Spartina alterniflora, and a co-occurring native plant, Phragmites australis. We found that crabs consistently suppressed P. australis by density and aboveground biomass regardless of N enrichment. In contrast, for S. alterniflora, the negative effects of crabs under ambient N were replaced by positive effects under N enrichment, with crabs stimulating complementary increases in density and aboveground biomass. The differing effects between the N treatments were driven by crab burrowing activity, which increased soil N availability, and the nutrient-use efficiency of S. alterniflora. Our findings revealed that native herbivores can have opposing effects on native and invasive plants, which broadens our understanding of how exotic plants can achieve dominance in a changing world.

Burrow Characteristics and Habitat Associations of Gopher Tortoises in Urban Pine Rockland Reserves (Miami, Florida, USA)

The Gopher Tortoise is a keystone species and a species of conservation concern in the southeastern United States, but the biology of tortoises at the extreme southeastern limit of the range is poorly understood. We examined physical characteristics and habitat associations of Gopher Tortoise burrows in pine rockland natural preserves in the highly urbanized Miami-Dade County (Florida, USA). We measured width, depth, and orientation of burrows at two sites. We compared a suite of 11 habitat features (e.g., canopy cover, understory density, ground cover, soil depth, and soil compaction) at random points and at Gopher Tortoise burrows in each of the two sites. Burrow widths were similar between sites and included burrows of both adults and juveniles—evidence that both populations are reproducing. Burrows were very short (most <2 m) compared to burrow lengths reported from other sites (>4 m), likely because soil depth is very shallow in extreme south Florida. We used multidimensional scaling and analysis of similarity to detect differences in habitat variables among sites, among point types (random points and burrows), and between active and inactive burrows. Low leaf litter cover, high grass cover, low canopy cover, and deep soil were among the major variables associated with all burrows and active burrows. The habitat associations of the burrows were similar to studies from other areas, yet the short burrows and association with the deepest available soils appear to be a strong response to the unique geology of pine rockland habitats. We discuss vegetative associations of Gopher Tortoises in the context of management in urban natural areas and implications for protection of Gopher Tortoises at the southern limit of their geographic range.

Mussels and Local Conditions Interact to Influence Microbial Communities in Mussel Beds.

Microbiomes are increasingly recognized as widespread regulators of function from individual organism to ecosystem scales. However, the manner in which animals influence the structure and function of environmental microbiomes has received considerably less attention. Using a comparative field study, we investigated the relationship between freshwater mussel microbiomes and environmental microbiomes. We used two focal species of unionid mussels, Amblema plicata and Actinonaias ligamentina, with distinct behavioral and physiological characteristics. Mussel microbiomes, those of the shell and biodeposits, were less diverse than both surface and subsurface sediment microbiomes. Mussel abundance was a significant predictor of sediment microbial community composition, but mussel species richness was not. Our data suggest that local habitat conditions which change dynamically along streams, such as discharge, water turnover, and canopy cover, work in tandem to influence environmental microbial community assemblages at discreet rather than landscape scales. Further, mussel burrowing activity and mussel shells may provide habitat for microbial communities critical to nutrient cycling in these systems.

Systemic Inflammation Accelerates Changes in Microglial and Synaptic Markers in an Experimental Model of Chronic Neurodegeneration.

Bacterial infections are a common cause of morbidity and mortality in the elderly, and particularly in individuals with a neurodegenerative disease. Experimental models of neurodegeneration have shown that LPS-induced systemic inflammation increases neuronal damage, a process thought to be mediated by activation of “primed” microglia. The effects of a real systemic bacterial infection on the innate immune cells in the brain and neuronal networks are less well described, and therefore, in this study we use the ME7 prion model to investigate the alterations in microglia activation and phenotype and synaptic markers in response to a low grade, live bacterial infection. Mice with or without a pre-existing ME7 prion-induced neurodegenerative disease were given a single systemic injection of live Salmonella typhimurium at early or mid-stage of disease progression. Immune activation markers CD11b and MHCII and pro-inflammatory cytokines were analyzed 4 weeks post-infection. Systemic infection with S. typhimurium resulted in an exaggerated inflammatory response when compared to ME7 prion mice treated with saline. These changes to inflammatory markers were most pronounced at mid-stage disease. Analysis of synaptic markers in ME7 prion mice revealed a significant reduction of genes that are associated with early response in synaptic plasticity, extracellular matrix structure and post-synaptic density, but no further reduction following systemic infection. In contrast, analysis of activity-related neuronal receptors involved in development of learning and memory, such as Grm1 and Grin2a, showed a significant decrease in response to systemic bacterial challenge. These changes were observed early in the disease progression and associated with reduced burrowing activity. The exaggerated innate immune activation and altered expression of genes linked to synaptic plasticity may contribute to the onset and/or progression of neurodegeneration.

Using tracking technology to locate endangered ʻuaʻu or Hawaiian Petrel (Pterodroma sandwichensis) burrows

The ʻuaʻu, or Hawaiian Petrel, <em>Pterodroma sandwichensis</em>, is an endangered seabird endemic to the Hawaiian Islands. Although its distribution on some of the islands is well documented, on larger islands such as Hawaiʻi there are significant distribution gaps. Previous work within the Puʻu O ʻUmi Natural Area Reserve (NAR) on Hawaiʻi strongly suggested that a breeding colony of the species was present, but active burrows had not been located making it difficult to focus management actions. Searching for burrows of this nocturnal burrow-nesting seabird had been particularly challenging in the NAR, as the birds are very rare, widely dispersed, and breeding in remote areas with dense vegetation and challenging topography. To locate active burrows, we employed the use of tracking devices to track breeding adults back to their burrows. Six data loggers (e-obs Bird Solar 10g) were attached to transiting birds caught using lights in 2018 and 2019. Overland locational data was then interrogated for concentrated areas of circling and ground activity. This resulted in several areas of concentrated activity and two different locations where tracked birds ended up transmitting from the ground. Burrow searching teams were then deployed to these areas and an active Hawaiian Petrel burrow was located. This represents the first active burrow ever documented in the NAR and the entirety of Kohala Mountain. Management actions have since been initiated to protect birds breeding within the areas defined by our tracking data. Logistical and methodological considerations inherent in the use of telemetry for locating endangered seabird colonies are discussed.

Elevation influences salt marsh crab abundance, diversity, and burrowing

Identifying drivers of the spatial distribution of organisms is a key aim of ecology. Salt marsh ecosystems can exhibit extreme gradients in abiotic conditions, including orders of magnitude differences in physical conditions across the marsh platform, which may contribute to the spatial distributions of organisms found in marshes. Small-bodied consumers, such as crabs, have been identified as key residents of salt marshes, with strong impacts on salt marsh persistence and stability at local scales. However, due to a lack of consensus regarding crab impacts across larger biogeographic scales, continued investigation into the factors driving crab community spatiotemporal dynamics is needed. We used an observational approach to investigate the small-scale spatial patterns and environmental correlates of marsh crab abundance, burrowing activity, and community composition in a representative southeastern US salt marsh. We documented contrasting trends in crab abundance and burrowing activity across the marsh platform elevation gradient, with abundance increasing and burrow density decreasing from the creek bank to forest edge. Crab diversity generally increased with distance from tidal creeks, though the effect of marsh zone on crab diversity was site-specific. Finally, we demonstrated elevation as the key environmental predictor of marsh crab abundance, burrowing activity, and community diversity and identified specific elevations that serve as breakpoints in those metrics. Our results contribute to reconciling differences between small-scale manipulative experiments and large-scale biogeographic sampling of these ecosystem engineering salt marsh residents.

Human influence on burrow activity of the Chinese pangolin in Nepal

Context People and wildlife are coming into greater contact worldwide because of the increasing human footprint. Although some species tolerate certain levels of human activities, others are vulnerable to human disturbance, potentially altering their spatial or temporal patterns of activity in response to disturbance by humans. Aims We evaluated the influence of human activity on burrow activity of the Chinese pangolin, a Critically Endangered species that is heavily persecuted for subsistence and illegal trade. Methods We deployed remotely triggered camera traps at pangolin burrows located at four sites with contrasting levels of human density and infrastructure in Nepal, and estimated burrow-activity patterns of pangolins by using a kernel-density estimator based on the time stamp of camera trap observations. Key results Our findings did not suggest that anthropogenic disturbance affected pangolin burrow activity, but we acknowledge that these findings were based on a limited number of observations. Peak pangolin burrow activity was observed after midnight in three of the study sites, including those with highest and lowest levels of human activity. The fourth area, which had intermediate levels of human activity, had an earlier peak in burrow activity, possibly caused by prey deficiency owing to intense agriculture. Conclusions We suggest that pangolins may tolerate human activity because of their strictly nocturnal temporal niche, but that this tolerance has made them vulnerable to poaching because it allows them to co-exist spatially with humans. Implications Nocturnal species may be particularly prone to non-conflict-related persecution, because they may be easily accessible targets for illegal hunting activities.

It’s a trap: effective methods for monitoring house mouse populations in grain-growing regions of south-eastern Australia

Abstract Context Wild house mice cause substantial economic damage to grain crops in Australia, particularly during mouse plagues. Populations were monitored to detect changes in abundance, with data from surveys used in models to forecast likely mouse outbreaks. However, it is not always feasible to use live-trapping (the ‘gold standard’) for assessing mouse abundance at a large number of monitoring sites spread across south-eastern Australia. A range of alternative methods was tried to assist the grains industry with strategic decisions to reduce crop damage. Aims The aim of this work was to determine which survey methods could provide useful and effective indexes of mouse abundance across a large area. Methods Monitoring of mouse populations was conducted at representative grain farms by using (1) live-trapping at long-term ‘benchmark’ sites (n = 2), and (2) mouse chew cards and active burrow counts at ‘rapid-assessment’ sites (n = 44 farms across 5 regions). Monitoring was conducted for 22 monitoring sessions over 7.5 years through low, medium and high mouse abundance conditions. Key results Live-trapping provided the most useful, but most resource-intensive, information. There were strong relationships between the index of mouse abundance from live-trapping with mouse chew cards and active burrow counts at a local (explaining 63% and 71% of variation respectively) and regional (explaining 71% and 81% of variation respectively) scales. The same quantitative relationship held between the mouse chew cards and trapping regardless of season and year. However, the relationship between active burrow counts and trapping was best in winter and autumn seasons. There was a strong relationship between mouse abundance from live-trapping and active burrows across 1 ha grids (R2 = 0.88). We determined there were 1.3 ± 0.2 (mean ± s.e.) mice per active burrow. Conclusions Live-trapping supplemented with data from chew cards and active burrows remains sufficient to monitor a wide range of sites to show regional trends. Implications It is likely that live-trapping will need to be used for the foreseeable future to provide useful parameters such as breeding condition and population abundance that are required for the forecast models. Supplementary monitoring at rapid-assessment sites (using chew cards in all seasons and active burrow counts particularly in autumn and winter), that can be collected easily without the need for animal handling, will provide additional indications of region-specific changes in mouse abundance and activity.

Integrating earthworm movement and life history through dynamic energy budgets.

Earthworms are considered ecosystem engineers and, as such, they are an integral part of the soil ecosystem. The movement of earthworms is significantly influenced by environmental factors such as temperature and soil properties. As movement may directly be linked to food ingestion, especially of endogeic species like Aporrectodea caliginosa, changes in those environmental factors also affect life history traits such as growth and reproduction. In our laboratory studies, earthworms showed a decrease in burrowing activity with decreasing moisture levels and, to some extent, the organic matter content. The burrowing activity of earthworms was also affected by temperature, for which the casts produced per earthworm was used as a proxy in laboratory experiments. We integrated changes in earthworm movement and life histories in response to temperature, soil organic matter content and the moisture level, as observed in our experiment and reported in the literature, through dynamic energy budget (DEB) modelling. The joint parametrization of a DEB model for A. caliginosa based on movement and life history data revealed that food ingestion via movement is an integral part of the earthworms' energy budgets. Our findings highlight the importance of soil properties to be considered in the model development for earthworms. Furthermore, by understanding and incorporating the effect of environmental factors on the physiology, this mechanistic approach can help assess the impact of environmental changes such as temperature rise or drought.

Хронология плейстоценовых находок рода Homo в Сибири: результаты и проблемы (краткий обзор)

This overview article contains a brief critical analysis of the chronology of Late Pleistocene and Early Holocene finds of Homo remains in Siberia. Direct dating of the Homo bones and teeth, as well as the isolation and analysis of the ancient human DNA, has now become firmly established in the practice of paleoanthropological research. About 62% of the Late Pleistocene and Early Holocene Siberian Homo remains have information on ancient DNA and direct dates of the bones and teeth. Particular attention is given to the assessment of the reliability of ages determined by the radiocarbon dating method. Information on the taphonomy (conditions and process of burial and fossilization) of Homo remains in the caves of the Mountain Altai is also of great importance. At present, three species of Pleistocene Homo are known in Siberia: Denisovans, Neanderthals, and anatomically modern humans (Homo sapiens). For the DenisovanNeanderthal hybrid, there is a direct date obtained by the Uranium series method, which shows the age of 67,500 cal BP. The age of other Denisovan fossils cannot be precisely determined due to the significant mixing of layers in Denisova Cave. The timing of the Denisovans in Siberia can be preliminarily determined at 130,000–44,000 cal BP (the upper limit is very approximate). The age of Siberian Neanderthals is greater than 50,000 cal BP; it is difficult to be more precise due to the widespread disturbance of the Altai caves’ stratigraphy by the burrowing activity of animals, primarily cave hyenas. Early Homo sapiens inhabited Siberia from 45,000 cal BP to the Early Holocene. No clear correspondence can be observed between climate changes in the second half of the Late Pleistocene (45,000–12,000 cal BP) and the chronology of Homo sapiens in Siberia. The age of some Homo sapiens fossils (Baigara, Solovyinaya Luka, and Sibiryachikha 6) after direct dating turned out to be much younger than initially expected. The taxonomic status of some Siberian Homo (Tuyana; an individual from the Okladnikov Cave with a date of 28,300 cal BP) has not yet been reliably identified. Obviously, it is necessary to increase the number of direct dates for Siberian hominins.

Crayfish connections: Linking ecology and hydrogeology in Alabama’s Black Prairie using crayfish distribution patterns

Abstract Floodplain ecosystems host diverse surface‐water habitats (e.g., lotic, lentic, ephemeral) and groundwater features that support high levels of species diversity. Our understanding of species–habitat relationships within these complex ecosystems, however, remains incomplete, potentially hindering conservation efforts. Understanding associations between burrowing crayfish and habitat features of floodplains is particularly valuable because crayfish, through burrowing, play an important role in establishing aquatic‐terrestrial connections which enhance local biodiversity. Species of crayfish that persist in floodplains must burrow deep enough to access shallow groundwater. Consequently, burrow presence may indicate a preference for specific surface and subsurface habitat characteristics. The primary goal of our study was to evaluate specific habitat attributes as predictors of burrowing crayfish presence/absence, and our secondary goal was to evaluate species‐specific habitat associations with respect to the same environmental variables. We evaluated burrowing crayfish presence/absence and crayfish species composition with respect to groundwater depth, flood frequency (standing surface water), soil characteristics, and tree size in the Bogue Chitto Creek catchment, Dallas County, Alabama, U.S.A. Active burrows were expected at sites with access to water (a shallow water table) and at sites with environmental variables more conducive to burrow stability (fine‐grained soils and mature trees). Species composition was predicted to vary with groundwater depth and flood frequency. Groundwater depth was the primary driver of burrowing crayfish presence/absence in our system; active burrows were more likely to be present in areas with relatively shallow groundwater depths. Within occupied sites, differences in crayfish species composition were significantly associated with the degree of flooding during the 1‐year study period. Species associated with a high dependence on surface waters were collected alongside species dependent on burrowing to access groundwater, suggesting that the environmental features of floodplains satisfy a diverse set of requirements. In particular, sites offering a mosaic of accessible groundwater depths and floodplain pools may provide critical habitat for diverse assemblages of burrowing crayfish species. Our study revealed a strong association between the presence/absence of active crayfish burrows and the depth to groundwater, a result that supports using burrowing crayfish as indicators of accessible groundwater. This will be increasingly important in the context of how climate change might influence water availability and local species diversity.

Distress Analysis of Mice with Cervical Arteriovenous Fistulas.

Simple SummaryFunctional hemodialysis access is essential for the survival of patients with end-stage renal disease. Although various guidelines recommend autologous arteriovenous fistula as the first choice for hemodialysis, it is still the Achilles heel for patients. Several in vivo models have been used to study and improve the mechanisms of vascular remodeling of arteriovenous fistula. However, some models have the disadvantage of having anatomical features or a hemodynamic profile different from that of the arteriovenous fistula in humans. In the presented cervical arteriovenous fistula model, these disadvantages were eliminated. It resembles the human physiology and is an ideal animal model for arteriovenous fistula research. Moreover, in order to understand the impact of this model on animal welfare, the distress of this new animal model was analyzed. Body weight, faecal corticosterone metabolites, burrowing activity, nesting behaviour and distress scores were analysed after fistula creation and during the following three weeks. The physiological, behavioural, and neuroendocrine assessments all indicated that this model causes only moderate distress to the animals. This not only meets the need for animal ethics but also improves the quality of scientific research. Therefore, this cervical model is suitable for arteriovenous fistula research and should be used more frequently in the future.The welfare of laboratory animals is a consistent concern for researchers. Its evaluation not only fosters ethical responsibility and addresses legal requirements, but also provides a solid basis for a high quality of research. Recently, a new cervical arteriovenous model was created in mice to understand the pathophysiology of arteriovenous fistula, which is the most commonly used access for hemodialysis. This study evaluates the distress caused by this new animal model. Ten male C57B6/J mice with cervical arteriovenous fistula were observed for 21 days. Non-invasive parameters, such as body weight, faecal corticosterone metabolites, burrowing activity, nesting activity and distress scores were evaluated at each time point. Six out of ten created arteriovenous fistula matured within the observation time as defined by an increased diameter. The body weight of all animals was reduced after surgery but recovered within five days. In addition, the distress score was significantly increased during the early time point but not at the late time point after arteriovenous fistula creation. Neither burrowing activity nor nesting behaviour were significantly reduced after surgical intervention. Moreover, faecal corticosterone metabolite concentrations did not significantly increase. Therefore, the cervical murine arteriovenous fistula model induced moderate distress in mice and revealed an appropriate maturation rate of the fistulas.

Ontogeny in the steinmanellines (Bivalvia: Trigoniida): an intra- and interspecific appraisal using the Early Cretaceous faunas from the Neuquén Basin as a case study

AbstractDespite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

Reviews and syntheses: Composition and characteristics of burrowing animals along a climate and ecological gradient, Chile

Abstract. Although the burrowing activity of some species (e.g., gophers) is well studied, a comprehensive inventory of burrowing animals in adjacent biomes is not yet known, despite the potential importance of burrowing activity on the physical and chemical evolution of Earth's surface. In this study, we review the available information with a focus on the following: (a) an inventory of burrowing vertebrates and invertebrates along the climate and ecological gradient in Chile; (b) the dimensions and characteristics of burrows; and (c) calculation of excavation rates by local species compositions. Methods used include a literature compilation (&gt; 1000 studies) of Chilean burrowing animal species integrated with global, species-specific excavation rates. A field study augments literature findings with quantification of the zoogeomorphic effects on hillslope mass transport at the animal community level and along the arid to humid–temperate climate gradient within the Chilean Coastal Cordillera (27–38∘ S latitude). The literature review indicates a minimum of 45 vertebrate and 345 invertebrate burrowing species distributed across Chile in different biomes. Burrowing depths for Chilean mammals range between 3 m (e.g., for skunks, Conepatus) and 0.25 m (for rock rats, Aconaemys). For invertebrates, burrowing depths in Chile range between 1 m for scorpions to 0.3 m for spiders. In comparison, globally documented maximum burrow depths reach up to more than 6 m for vertebrates (gopher tortoises and aardvarks) and 4 m for invertebrates (ants). Minimum excavation rates of local animal communities observed from field sites in Chile are 0.34 m3 ha−1 yr−1 for the arid site, 0.56 m3 ha−1 yr−1 for the semiarid site, 0.93 m3 ha−1 yr−1 for the mediterranean site and 0.09 m3 ha−1 yr−1 for the humid–temperate site, with the latter likely an underestimation. The calculated minimum Chilean excavation rates are within the large range of globally observed single species rates ranging between 0.01 and 56.20 m3 ha−1 yr−1 for vertebrates and from 0.01 to 37.31 m3 ha−1 yr−1 for invertebrates. Taken together, results not only highlight the diverse and latitudinally varying number of burrowing vertebrates and invertebrates present in different biomes, but also foster the understanding of how burrowing activity changes over a gradient and is influenced by mean annual temperature, mean annual precipitation, slope aspect and latitudinal-related incoming solar energy.

Changes in Vegetation Structure and Gopher Tortoise Population Structure after 17 Years of Restoration Management

We examined a study plot sampled in the Conecuh National Forest of southern Alabama in 1999 and again in 2016 after stand thinning and persistent prescribed fire were used to improve habitat quality. These management activities were designed, in part, to enhance habitat quality for the gopher tortoise (Gopherus polyphemus), a species considered for protection under the Endangered Species Act because of range-wide population declines. Comparisons of vegetation structure were made at burrows that were active in 1999 and remained active in 2016, and at burrows that were active in 1999 but were classified as abandoned in 2016. Burrows that remained active across this span of time were distinctive in retaining a greater reduction of canopy cover and lacking hardwoods while having a high percentage of longleaf pine in neighboring canopy trees. Active burrows that were abandoned in 2016 were distinctive in possessing hardwoods among neighboring canopy trees, lacking pine seedlings in the midstory, and having increased frequency of legumes and decreased bare ground in the understory. All burrows experienced a decrease in canopy cover and an increase in distance to, and dbh of, neighboring canopy trees; all burrows also had a decrease in litter and non-legume forbs as well as an increase in shrub stems in the understory and midstory. These results indicate that management activities were successful in opening canopy cover but were largely unsuccessful at reducing shrub stems and increasing understory grasses and forbs. Nevertheless, burrows of gopher tortoises increased in abundance during this time period. The size distribution of these burrows changed from a unimodal distribution dominated by adults to a bimodal distribution indicative of increased juvenile recruitment. Thus, the gopher tortoise population increased in association with vegetation changes that suggest tortoises are more sensitive to shading caused by canopy closure than they are to available forage.

Effects of anecic earthworms on runoff and erosion on the slope with soil from the Loess Plateau under a rainfall simulation experiment

Earthworms are ecological engineers that play an important role in hydrological processes and soil erosion by their burrowing and casting activities. Little is known, however, about the ecological function of the activities of an anecic species (Metaphire guillelmi) from the Loess Plateau in China where the soil is severely eroded. We conducted rain-simulation experiments on artificial slopes (mesocosms) filled with soil from Loess Plateau. Two rain intensities (90 and 120 mm h−1) and slope gradients (5° and 15°) were used to investigate the influences of earthworm activity on runoff and soil loss under multiple conditions. Data from 15 d of earthworm activity and 1 h of rain indicated that earthworm activity significantly reduced runoff but aggravated soil erosion. Runoff initiation time increased 2.7–3.1-fold, contributing to the promotion of water infiltration, and the amounts and rates of runoff were 35.8–61.6% and 35.1–60.8% lower under earthworm activity than the controls, respectively. Earthworms greatly influenced the physical and chemical properties of the soil, and these properties were strongly correlated with runoff initiation time and cumulative runoff. The surface casts produced by the earthworms on the soil surface were completely dispersed, increasing the cumulative sediment by a maximum of 169%. Both rain intensity and slope gradient greatly influence runoff and soil detachment, but with earthworm activity, slope gradient was more influential due to its superior contribution to sediment transport. This study quantified the effects of M. guillelmi on runoff and soil erosion and provides basic data for developing a more integrated control of soil erosion on the Loess Plateau.

Pikas burrowing activity promotes vegetation species diversity in alpine grasslands on the Qinghai-Tibetan Plateau

The burrowing activity of plateau pikas (Ochotona curzoniae; hereafter, pikas) may profoundly influence vegetation species composition on the Qinghai-Tibetan Plateau (QTP). Although significant efforts have been made to examine the relationship between vegetation species composition and pikas disturbance, our knowledge regarding the direct influence of pikas activity on vegetation species diversity is still limited. We conducted field observations on pikas burrows and surrounding vegetation patches at 23 alpine grassland sites to investigate this effect. When compared to vegetation patches, pikas burrowing activity decreased soil hardness, thus improving water infiltration, while caused the less reduction of soil nutrition and soil moisture when compared to adjacent vegetation patches. Vegetation species composition on pikas burrows significantly differed from that on vegetation patches. Common plant species between pikas burrows and vegetation patches were fewer than three in all types of grasslands, and ten species were found exclusively on pikas burrows. The total species richness, including both pikas burrows and vegetation patches, was approximately 1.3–2.5 times higher than that on each single patch type (pikas burrows or vegetation patches). A conceptual framework was proposed to synthesize the evolution of vegetation species composition under a disturbance regime resulting from pika’s burrowing. Overall, we concluded that pika’s burrowing activity enhanced vegetation species richness by loosening the soil, creating safe sites for seed settling and germination, which provided a novel habitat for vegetation invasion.