Distribution Of Burrows Research Articles

Identifying habitat modification by Chinese pangolin in subtropical forests of southern China.

The excavation of Chinese pangolin (Manis pentadactyla) is expected to alter habitat heterogeneity and thus affect the functioning and structure of forest ecosystems. In this study, the bioturbation of Chinese pangolin on forest soils in three regions (Heping, Tianjingshan, and Wuqinzhang) across Guangdong province was quantified. Overall, a mean of 2.66 m3·ha-1 and 83.1 m2·ha-1 of burrows and bare mounds, respectively, was excavated by Chinese pangolin; the disturbed soils had significantly lower water content and P, C, available N concentrations, but higher bulk density, pH, and microbial abundance than those undisturbed soils. The unevenness of habitat heterogeneity improvement was mainly ascribed to the stronger soil disturbance caused in resting burrows by pangolins. Patterns of altering habitat heterogeneity were site-specific, with high-intensity soil disturbance occurring most in shrubs, meadows, steep habitats at high elevations, and mountain tops in Heping, while in broad-leaved, coniferous andmixed coniferous and broad-leaved forests away from human settlements in Tianjingshan and upper mountains at high elevations far away from roads and human settlements in Wuqinzhang. Road networks are the main interference for the burrow distribution in Heping and Wuqinzhang and should be programmed.

Grazing affects ecosystem traits by regulating plateau pika activities at the landscape scale

The mechanism underlying the effects of livestock grazing on grassland ecosystem traits has been greatly discussed. However, as a common small burrowing mammal on the Tibetan Plateau grasslands, the plateau pika's (Ochotona curzoniae) influence on alpine grassland ecosystem traits has rarely been investigated, especially beyond the plot scale. In this study, we flew an unmanned aerial vehicle (UAV) over a grassland landscape under grazing and nongrazing treatments. Mounted visible spectral remote sensing, in combination with field surveys, was utilized to explore how livestock and pika grazing modify grassland ecosystem traits at the landscape scale on the Tibetan Plateau (TP). Using object-oriented classification and partial least squares regression, we retrieved the pika burrow distribution and grassland ecosystem traits. Then, the relationships among livestock grazing, pika burrowing and ecosystem traits were evaluated. The results indicated that livestock grazing reduces the alpine meadow community height by 0.13 cm and the species number by 0.25 while increasing the vegetation coverage by 9.69 % and the aboveground biomass (AGB) by 10.07 g/m2. A lower statue grassland community with greater coverage caused by livestock grazing promotes pika burrowing. Pika burrow density increases 100/ha per 1.70 % increase in vegetation coverage, a 1.87 g/m2 increase in AGB or a 0.08 m decrease in community height. Under livestock grazing, both community structure and nutrients are more strongly associated with pika burrow density. The structural equation model demonstrated that livestock grazing regulates pika burrow density by moderating structural value and subsequently affecting nutritional value. Pika burrowing activity explains 40 % of the total variation in nutritional value. Our findings revealed an intrinsic linkage between mammal activities and alpine grassland ecosystems, which can provide guidelines for grassland management through pika population control by adjusting grazing intensity on the TP.

Response mechanism of rodent burrow density to natural environmental factors in desert areas based on multisource data

Timely and accurate prediction and early warning of rodent infestation are highly important for the sustainable development of desert ecosystems. This study combines data from 1376 UAV images of actual rodent burrows with natural environmental factor data, aiming to reveal the mechanism through which these factors affect rodent burrow density in the desert areas. The relationships between rodent burrow density and the 9 plant communities and 34 plant species in this area were analyzed by the K-W test and Spearman rank correlation analysis, respectively. The Boruta algorithm and the boosted regression trees (BRT) model were used to determine the six main factors influencing rodent burrow density from a total of 32 factors and to determine the distribution pattern of the burrows. The results show that (1) the density of rodent burrows in the Junggar Basin desert area gradually decreases from south to north and from west to east. (2) There were significant differences in rodent burrow density across the different plant community types (P = 0.048**). A total of 50.0 % of the species significantly influenced rodent burrow density at at least one level. (3) Among the 17 factors with lag effects, nine had the most significant correlation with rodent burrow density in April. Only two natural environmental factors demonstrated lag effects of less than one month. (4) The soil clay content, elevation, Normalized Difference Salinity Index (NDSI), vegetation cover, precipitation, and soil bulk density were the most important influencing factors on rodent burrow density. Considering the pairwise interactions among factors, the collective impact of these factors on rodent burrow density is at least sevenfold greater than the independent effect of a single factor. This study provides a theoretical basis for obtaining a timely and accurate understanding of the spatial distribution of rodent burrows, mitigating the degradation trend of desert ecosystems, and ensuring healthy and sustainable development.

The impact of sward height, forage quality and competitive conditions on foraging behaviour of free-ranging rabbits (Oryctolagus cuniculus L.)

The habitat choice of the small hindgut fermenter, the European rabbit (Oryctolagus cuniculus L.), was studied in relation to sward height, forage quality, population size fluctuations and spatial distribution of burrows in a temperate grassland. In a multi-phase differential clipping experiment with alternating short and tall vegetation strips, rabbits tended to graze near the closest burrows in situations of equal vegetation heights, while a clear preference for short swards was found during summer (July). In this period, general crude protein content was significantly lower than in spring (April) and autumn (September), apparently leading to a potential forage quality deficit. The summer behavioural pattern with short sward preference coincided with the relatively higher crude protein content of short swards as compared to tall swards in this period, and with higher intraspecific competition, due to significantly larger numbers of animals present in summer. In autumn, rabbit densities decreased, while crude protein content of both short and tall vegetation increased to a higher, though not significantly different level, comparable with spring crude protein content. In those conditions, significant preference for low vegetation height could no longer be detected. Data suggest that selection for nutritive quality appears when intraspecific competition is high and nutritive quality remains under a certain threshold value. When, in autumn, competition decreases and nutritive quality increases again, short sward preference disappears. We conclude that short sward preference is primarily caused by the better forage quality of re-growth in periods of forage quality limitation, while this preference disappears when forage quality limitation no longer occurs.

Seasonal regulation of tidal creek burrow distribution: Unveiling the dynamic interplay of biotic and abiotic factors

Intertidal creek ecosystems in saltmarsh wetlands provide crucial ecological services, with burrows facilitating material exchange between these environments. Investigating burrow distribution in tidal creeks is essential, yet the underlying mechanisms remain poorly understood. Our study conducted field observations during two seasons, dividing the typical creek section into microhabitats: flat (F), gentle edge (GE), gentle slope (GS), steep slope (SS), and steep edge (SE). Comprehensive analysis of sediment samples encompassed assessments of water content, organic matter, particle size, and salinity. Burrow parameters were extracted using a deep learning method applied to sample images. Benthic biodiversity and community compositions were characterized through eDNA analysis. Our findings revealed significant variations in burrow distribution, sediment properties, and community compositions, both between and within creek sections. Temporal heterogeneity emerged as a substantial influencer of burrow characteristics, while the propensity of benthic communities to respond to topography and sediment properties constituted a chief determinant of burrow distribution. Utilizing a structural equation model based on field data, we illuminated four response pathways governing burrow distribution. Abiotic factors, especially under temporal heterogeneity, had a paramount impact, highlighting the need to explore relative biotic and abiotic influences, considering seasonal regulation. These findings establish a foundational understanding of burrow distribution and its driving mechanisms in creek ecosystems. They offer valuable insights for future field observations and research directions in this field.

Impact of Mangrove Deforestation on Fiddler Crab Distribution and Soil Physico-chemistry at Eagle Island, Rivers State

Mangrove forest in the Niger Delta and its associated biotic and abiotic has been greatly impacted by several factors, some natural and others anthropogenic in nature. Anthropogenic activities have negatively affected the organisms that inhabit the forest resulting in the decrease in size of population of fiddler crabs (Uca tangeri). To investigate the influence of anthropogenic activities on the mangrove habitat, burrow distribution and population of fiddler crabs and soil physico-chemistry were determined in forested and deforested sites. Burrows and number of crabs outside burrows were counted while samples of soil were retrieved and moved to the laboratory for the determination of cadmium (Cd), lead (Pb), total hydrocarbon content (THC) and Zinc (Zn) using atomic absorption spectrophotometer. The conclusions show a lack of significant difference in burrow distribution between forested and deforested areas (P>0.05). Contrastingly there is significance in the difference in crab population in forested and deforested sites. (P<0.05), which showed that there were more crabs in deforested areas than forested areas. There was also a significant difference in chemical and microbial population (P<0.05). There was higher THC in deforested areas, which was probably impacted by the heavy-duty vehicles used to cut down the trees. The result implies that human activities of deforestation and pollution influence crab population and soil physicochemistry in mangrove forest.

Burrow-Nesting Seabird Survey Using UAV-Mounted Thermal Sensor and Count Automation

Seabird surveys are used to monitor population demography and distribution and help us understand anthropogenic pressures on seabird species. Burrow-nesting seabirds are difficult to survey. Current ground survey methods are invasive, time-consuming and detrimental to colony health. Data derived from short transects used in ground surveys are extrapolated to derive whole-colony population estimates, which introduces sampling bias due to factors including uneven burrow distribution and varying terrain. We investigate a new survey technique for nocturnally active burrow-nesting seabirds using unoccupied aerial vehicles (UAVs) and thermal sensor technology. We surveyed a three-hectare short-tailed shearwater (Ardenna tenuirostris) colony in Tasmania, Australia. Occupied burrows with resident chicks produced pronounced thermal signatures. This survey method captured a thermal response of every occupied burrow in the colony. Count automation techniques were developed to detect occupied burrows. To validate the results, we compared automated and manual counts of thermal imagery. Automated counts of occupied burrows were 9.3% higher and took approximately 5% of the time needed for manual counts. Using both manual and automated counts, we estimated that there were 5249–5787 chicks for the 2021/2022 breeding season. We provide evidence that high-resolution UAV thermal remote sensing and count automation can improve population estimates of burrow-nesting seabirds.

The role of Magellanic penguins (Spheniscus magellanicus) on landscape dynamics and lithic taphonomy in La Pastosa Islet, North Patagonia, Argentina

This study presents the results of a systematic survey of La Pastosa Islet, located 700 m off the west coast of Río Negro, Argentina. This small islet has the particularity of hosting the northernmost colony of Magellanic penguins ( Spheniscus magellanicus) to date and contains evidence of its use by hunter-gatherer groups during the late Holocene. This growing colony started around 2002 and has had a significant impact on the subsurface archeological record of the islet by increasing erosion and exposing buried materials through nest excavation, particularly lithic artifacts. The spatial analysis of the distribution of artifact and penguin burrows indicates that the actions of the latter generated a “snapshot” of the subsurface distribution of the lithic record. The observed distribution suggested higher discard rates at the center of the islet. Furthermore, this study shows the synergy between both types of records in the formation dynamics of the lithic landscape and the agency of penguins as active landscape engineers. Finally, the obtained results have important implications for the management of the protected sector of the recently established Islote Lobos National Park, within which the study area is located.

The use of cameras on commercial deep-water trawls to investigate habitat associations and scampi trawl efficiency in New Zealand scampi Metanephrops challengeri

AbstractThis study assessed the effectiveness of using video cameras mounted on commercial trawls for a deep-sea lobster, the New Zealand scampi Metanephrops challengeri, for acquiring information on habitat associations of demersal species and fishing efficiency. Randomly selected frames from 1 h of recording replicated over 12 trawls and conducted over three fisheries management areas (FMA), were analysed for counts of visible scampi, scampi burrows, visible topographical features and visible epifauna and fish taxa. Poisson regression analysis indicated a positive relationship between the distribution of scampi burrows (a proxy of scampi abundance) and conical mounds (formed by bioturbators), but a negative relationship with smooth topography. Counts of scampi burrows were also positively associated with counts of visible scampi for four trawls, while significant relationships were seldom found between counts of scampi burrows and other commonly observed individual taxa. Scampi trawl efficiency was low, with only 56 of the 186 observed scampi (30%) passing over the footrope and into the trawl net. The results confirm the effectiveness of video sampling from commercial trawls to improve our understanding of habitats and fishing efficiency in deep-sea fisheries.

Red Ghost Crab Ocypode Macrocera (H. Milne Edwards, 1852) Population Dynamics Changes at Bay of Bengal Coast Line in Response to Construction of Digha Marine Drive and Tajpur Port: EIA Study by Rammohan College

Abstract: On the sand beaches of the Bay of Bengal, from Bichitrapur in Orissa to Mandermani in West Bengal, population dynamics of Ocypode macrocera (H. Milne Edwards, 1852) were investigated. The crabs are found across the coastal areas that face the sea. Bichitrapur, Talsari, Udaipur, New Digha, Mohana, Shankarpur, Tajpur, and Mandermoni were the principal study locations. The infra-littoral sand flats zone is where the Red Ghost Crabs live. The development of the particular stretch of beach and the prevalence of crab burrows are related. Crab activity occurs both during the day and at night. One to three openings towards the sea can be found in each crab burrow. EIA (Environmental Impact Assessment) is an essential study required before onset of any project or for any ongoing project. This EIA study was conducted in 2017, prior to the start of "Marine drive & Tajpur port" construction, and in 2020, following completion of "Marine drive& Tajpur port" by Rammohan College. At the construction areas, it was discovered that the Red Ghost Crab population had substantially decreased. Additionally altered is the burrow distribution pattern. An essential ecological stabilizer of Sea beach is the red ghost crab. Additionally, it was discovered that the sea beach began to erode where the crabs were completely gone.

Factors affecting the occupancy of Chinese pangolins (Manis pentadactyla) suggest a highly specialized ecological niche

AbstractThe Chinese pangolin is a critically endangered and biologically unique species, yet information on its status, distribution, and habitat preferences is still scarce in Nepal, which limits effective conservation action. This study identified the current burrow density status, distribution pattern, and important habitat parameters associated with Chinese pangolin distribution in Nepal through opportunistic field surveys. Fifty‐four belt transects were examined for the presence of pangolin burrows. For each active burrow (burrow with freshly dug soil, footprints, and scat near the entrance) and old burrow (burrow with compacted soil, presence of dead leaves, and spider web in the entrance), we recorded the geographic coordinates and assessed data on 11 habitat parameters that included elevation, aspect, slope, canopy cover, ground cover, presence or absence of ant and termite colonies, habitat type, soil type, and distances to the nearest water source, road, and settlement. A total of 141 active burrows and 430 old burrows were recorded with an overall clumped distribution . Active burrow density was estimated to be 1.04 burrows/ha. Of the 11 habitat parameters predicted to influence the probability of encountering pangolin burrows, all parameters were significant except elevation. More than 92% of the burrows were found at elevations between 450 and 750 m and facing either the SE or NW aspect. Similarly, about 90% of the burrows were distributed in areas having slopes between 0% and 30% with moderate to high canopy and ground cover, and located close to water sources, roads, and settlements. Additionally, they strongly preferred forest habitats (with Shorea robusta, Castanopsis indica, Schima wallichii, Clerodendron infortunatum, and Nephrolepis auriculata as the dominant vegetation), areas with red soil, and areas located near ant and termite colonies. Although the study area currently provides suitable habitat for Chinese pangolins, it is slowly being degraded due to increasing rates of forest degradation. Conservation efforts should be increased in order to protect this critically endangered species and their preferred habitats. Finally, our findings reveal the preferred habitat characteristics of Chinese pangolins, which could be instrumental for policy makers and forest managers in making conservation plans for Chinese pangolins.

Популяційна динаміка та розподіл за біотопами хом’яка (Cricetus cricetus) в Медоборах (Поділля)

The results of the surveys and data on biotopic distribution of common hamster burrows in the vicinity of the Medobory Nature Reserve were collected and summarised. In order to study the abundance and density of hamsters, two monitoring sites were established. The first is in the fields between the village of Butsyky and the town of Hrymailiv, and the second is on a farming field in the town of Hrymailiv, where since 2013 the number of common hamster burrows have been recorded in the autumn period of the year. Homestead plots and small-scale plantations of agricultural crops were surveyed using the transect method by one or two investigators. During nine years of research, 170 living burrows were found on the first site, which covers an area of about 10 hectares, and only 7 on the second site, which is located on a farm field. The majority of living burrows were recorded on crops of 3 to 4-year-old alfalfa. An increase in the number of burrows was observed in 2015 and 2019. Additional research was carried out in separate gardens with alfalfa in the vicinity of the town of Hrymailiv, the villages of Lezhanivka, Lychkivtsi, Zelene, and Paivka, and in farm fields, where 52 living burrows were recorded. Separate data were obtained from observation cards of reserve workers and by surveying the local population. The largest colony was found in the village of Lychkivtsi in 2021 in a garden with a four-year-old alfalfa plantation of 0.3 ha, and there were 16 settlements there (3 to 5 burrows per settlements). During nine years of observation, live animals were found only twice: in the village of Butsyky in 2013 (two individuals in a field in fodder beet crops) and near Lezhanivka in 2019 (one individual in a disced rapeseed field, during stork foraging). Usually, they are recorded dead: killed by predators or killed by motor vehicle collisions. Taking into account the distribution of burrows by biotopes, it is worth noting that the decline in the number of hamsters is the result of a decrease in agricultural land area suitable for their existence. The exception is the years 2019–2020, when their number began to increase rapidly, the cause of which could be the mass death of foxes that occurred as a result of poisoning by mouse-like rodents in farm fields in 2018, which served as their food base. As for the animals of the dark morph, their share in the population is no more than 10%, and they often become victims too, since their colouration is clearly visible in their living environs.

Influence of landscape transformation and anxiety factor on the distribution of burrows of the Common hamster (Cricetus cricetus L., 1758) (Rodentia: Cricetidae) in the conditions of the park zone of the city of Simferopol

Based on our analysis of long-term (2015–2021) observations carried out at a registration spot in the park named after Yu. A. Gagarin (Simferopol, Crimea), patterns were revealed in the spatial distribution of burrows of the Common hamster (Cricetus cricetus L., 1758) depending on the state of the tree and shrub layer, as well as disturbance factors. It is shown that the leading factor influencing the spatial distribution of burrows is the location of trees, and the total number of burrows is mainly affected by the projective covering by shrubs; these factors were revealed as a result of cluster analysis for the spatial-geographical formulation of the problem and crosscorrelation analysis. It is assumed that the use of spatial modeling makes it possible to identify environmental factors, including plant communities, influencing the choice and exploitation of microhabitats by animals, as well as to find approaches to the analysis of the implementation of behavioral patterns during the development and exploitation of a habitat.

Can the distribution of red fox burrows indicate the chafer larvae density?

Due to their general occurrence the European badger and the red fox have an important role in most of the ecosystems of the Carpathian basin. Both species use burrows for resting and cub rearing. Based on the previous studies, differences were found in the burrow site selection of these predators. The differences can be seen in case of the vegetation type, the soil texture and the density of primary food sources. This knowledge is important for wildlife managers and nature conservationists, but maybe useful for other sectors (e.g. agriculture, forest management) as well. In the present study, we have taken plant protection approach. Our question was the following: does the chafer larvae density differ in the surrounding of badger and red fox burrows? The study area is located between Gödöllő and Valkó, in the Gödöllő Hills. Its size is 3728 ha and mainly covered by forests (96%). Two methods were used during the study. At first strip transect method was implemented to find the burrows. 81 burrows were found in total, 14 of them were used by badger and 14 by red fox, 53 of them were abandoned. The second method was the chafer larvae density and biomass measurement. Eight samples were taken per each active burrow, it means 224 samples in total. Our results showed higher chafer larvae density and biomass in case of red fox burrows, than in case of badger burrows. We conclude that the soil texture could be in the background of this difference.

Role of abiotic drivers on crab burrow distribution in a saltmarsh wetland

Crab burrows play an important role in saltmarsh wetlands and are a useful indicator of wetland condition. The spatiotemporal distribution of crab burrows varies considerably in tidal wetlands. However, the reasons for these variations are poorly understood, in part, due to the limited availability of comprehensive field data. Based on a two-year continuous observation at a tidal wetland in the northern Jiangsu Coast, China, this study explored the relationship between crab burrow density and environmental variables, including median grain size, water content, organic matter content, soil salinity, and elevation. Our results show that the distribution of crab burrows was unimodal across the shore in winter and spring (Nov-Apr) when air temperature was relatively low, while bimodal in summer and autumn (May-Oct) when temperature was relatively high. The density of crab burrows was larger at areas with higher water content, higher organic matter content, and lower soil salinity, while it was lower with stronger hydrodynamics and lower suspended sediment concentration. Crab burrows were more abundant in vegetated areas than in un-vegetated areas. A backward stepwise model selection was performed based on R-square and Akaike information criterion (AIC) to distinguish the main driving factors that determine crab burrow distribution. Results suggested that the principal driving factors were organic matter content and soil salinity in all the seasons, with the addition of water content in warm seasons. Overall, this study provides a comprehensive field dataset for a more in-depth understanding of crab burrow distribution and a scientific basis for sustainable management of tidal wetlands.

Investigating a probable relationship between the distribution of microplastics and crab burrows in the intertidal zone of Chongming Island, Yangtze Estuary

Crab burrows are common biogeomorphic structures in the sedimentary environment of the intertidal zone. Existing studies have revealed crab burrows could function as traps and sinks for fine sediment particles and organic detritus transported by the overlying water. However, it was unknown whether the distribution of microplastics was related to crab burrows. To build on past work, we investigated the distribution characteristics of microplastics and crab burrows in the intertidal zone of Chongming Island and explored the probable relationship between them. The detection rate and abundance of microplastics in burrows were higher than in no-burrowing areas, indicating that crab burrow have a trapping function for microplastics. Crab burrows also increased the abundance and detection rate of microplastics in the deeper sediment layer, rather than just the surface layer. Furthermore, microplastics were more abundant in large burrows than in small burrows. The microplastics in the large burrow were significantly smaller in size than those in the small burrows and no-burrowing area. The abundance of microplastics positively correlated with the area occupied by burrows in the majority of study sites. Our findings provide a new perspective for exploring the transport and migration of the microplastics between the sediment and water column in the intertidal zone. Further controlled experiments should be carried to investigate the source-sink effects of crab bioturbation in the intertidal flat on microplastics.

Effect of Anthropogenic Pressure on Distribution and Burrow Morphology of the Brachyuran Crab, Dotilla blanfordi Alcock, 1900 (Decapoda: Brachyura) Inhabiting Mudflats of North Western India

Coastal regions are one of the most crucial ecosystems as they support biology of numerous vertebrate and invertebrate taxa which provide economic aid to mankind. Monitoring of the natural resources of the coasts and to test the ecological impact of human disturbance therefore becomes necessary. The present study was conducted from 26th January to 18th February 2019 to investigate the effect of anthropogenic impacts on the population (burrow density, distribution and size) and burrow characteristics (burrow length, depth, inclination angle, weight and volume) of Dotilla blanfordi Alcock, 1900. Total eight sandy beaches of Gujarat and Maharashtra states of India were examined. The beaches were categorised into pristine, moderately impacted or heavily impacted sites on the basis of various levels of anthropogenic pressures. It was found that the burrow density was observed maximum at the low impacted sites (Tithal --21.11±13.53; Dandi site-2 --20.66±11.23), as compared to the moderately impacted sites (Umargam-- 16.11±21.62; Gorai-- 20±10.77; Uran-- 7.11±10.99) and heavily impacted sites (Kuda-- 5.11±14.24; Koliyak-- 1.56±2.01; Dandi site 1-- 11.78±8.27). The crabs built simple burrows in heavily impacted sites as compared to the complex burrows in the moderately affected and pristine sites. Burrow weight and burrow volume showed significant variation across all study sites as compared to other morphological traits. The results inferred that anthropogenic stress can directly influence the distribution and burrow morphology of Dotilla blanfordi. The results also suggested utility of D. blanfordi as an indicator species for effective coastal management but the outcomes would benefit with a comprehensive study of environmental as well as ecological characters.

Coexistence of Juvenile with Adult Ocypode gaudichaudii at Culebra Beach, Panama: A Temporal-spatial Partitioning Compromise.

The temporal-spatial resource use patterns of juvenile and adult Ocypode gaudichaudii were studied by comparing the zonation patterns and activity budgets of the two life stages at Culebra Beach, Panama. Burrow distribution of the crabs during the day and at night was studied over six months. Diurnal activity budgets of 46 crabs (22 juveniles and 24 adults) were determined by observing seven predominant behaviors upon emergence from their respective burrows when the burrow zone is uncovered after the tide recedes. The behaviors comprise three foraging-related activities (i.e., deposit-feeding, scavenging, and probing for food), the maintenance of burrow, walking, staying within the burrow, and resting at the burrow entrance. Juvenile crabs occupied a higher intertidal zone than the adults and had a higher emergence rate at night. This temporal-spatial habitat partitioning could possibly reduce intraspecific competition between the two life stages, thereby enabling their coexistence in the habitat as well as increasing the survival rate of the juveniles, potentially raising the carrying capacity of the population at Culebra Beach. All 46 crabs-regardless of life stage-spent the highest mean proportion of time on foraging-related activities. Out of the three feeding-related behaviors, adults spent most time on deposit-feeding while juveniles spent most time probing. Only juveniles scavenged. In both life stages, a similar proportion of time was spent maintaining the burrow and staying within the burrow.

Characterization of the spatial distribution of plateau pika burrows along an alpine grassland degradation gradient on the Qinghai-Tibet Plateau.

Plateau pika burrows are common feature of degraded grassland in the Qinghai–Tibet Plateau (QTP) and serve as an important indicator of pika activity and grassland degradation. However, the current understanding of the spatial pattern changes of pika burrows and their critical thresholds across a degradation gradient in alpine grassland is deficient. In this study, we investigated and quantified changes in the spatial pattern of plateau pika burrows under typical degraded alpine shrub meadows in the northeastern QTP using an unmanned aerial vehicle and landscape pattern metrics. The degradation of the alpine shrub meadow leads to a change in landscape pattern from a two‐layered structure of alpine shrub and alpine meadow to a mosaic of alpine meadow and bare soil, with plateau pika burrows scattered throughout. Moderate degradation is the tipping point for changes in surface landscape patterns, followed by the disappearance of alpine shrub, the retreat of alpine meadows and the encroachment of bare soil, and the increasing density and size of pika burrows. The area characteristics of alpine meadows have influenced changes in the spatial pattern of pika burrow, and maintaining its proportional area is a vital measure to control the threat of pika burrows to pastures. The results of this paper provide a methodological reference and guidance for the sustainable utilization of grassland on the QTP.

Burrow occupation rates and spatial distribution within habitat of the ghost crab Ocypode quadrata (Fabricius, 1787): Implications for impact assessments

The most conspicuous characteristic of ghost crabs (Crustacea: Ocypodidae) is the construction of semi-permanent burrows on the sand, widely used as tools for impact assessments. Thus, it is now critical to understand the factors driving burrowing activity and burrow occupation rates, including the effects of natural and anthropogenic disturbances. We tested three hypotheses in the present study with the ghost crab Ocypode quadrata: (i) overestimation of population size by traditional burrow counts depends on disturbance level at local scale; (ii) burrow occupation rate is density-dependent; and (iii) the predominant spatial distribution of burrows within the habitat is uniform. The last two predictions were assessed using a meta-analysis for a macro scale assessment. The comparison of distinct methods for burrow counting confirmed that ghost crab density is overestimated on non-urbanized beaches at local scale. A non-linear relationship between burrow occupation rates and burrow density was found at local and regional scales. When burrow density increases, the burrow occupation rate is also higher. However, from approximately 20 to 30 burrows/100 m2, the occupation rate reduces with increased density. Thus, the overestimation of the ghost crab density on non-urbanized beaches can be partially explained by a density-dependence in burrowing activity probably driven by a stronger intraspecific competition on non-urbanized areas. Finally, the distribution pattern of the ghost crab is predominantly uniform in most of its distribution range, despite of urbanization level and sampling design, hence suggesting intra-specific interactions as a driver of burrowing behaviour. In conclusion, burrow density, occupation rate and spatial distribution within the habitat evidenced at various spatial scales that burrowing activity of the ghost crab is density-dependent and this constitutes an issue never considered before in impact assessments inherent to coastal monitoring and management.