Roost Size Research Articles

Roosting Behaviour and Population of Indian Mynas; & its Correlation with Sunset (light intensity) and the Time of Arrival

Abstract: Communal roosting behaviour is a very fascinating phenomenon that has been observed in numerous avian species wherein many birds stay together during night or daytime. Size of communal roosts may range from 5-6 individuals (e.g. Peafowl, drongo) to over 10,000 birds (e.g. Indian myna, crow, parakeets). Such birds have tendency to flock on their roost-ward journey. In this research, we observed communal roosting behaviour and population of Indian Myna (Acridotheres tristis). We identified one of the communal roosts of Indian Myna in Vaikunth Crematorium, Navi Peth area Pune and counted their population size at the time of their arrival to the roost during sunset on a fortnightly basis for a year by point count method. Census records were taken at 5 minutes interval on the number of flocks and flock sizes of these birds arriving to the communal roost in the evening. Also, recorded the light intensities over those intervals with the help of photometer. Our objective was to find out their population size and changes in the size at this particular roost and also to find out the correlation between the time of sunset (light intensity) and their time of arrival to the roost. This study illustrates the effect of light intensity on their roosting behaviour and analysis of any seasonal and monthly changes observed during the data collection period from 2 consecutive post breeding periods.

Presence of coronaviruses in the common pipistrelle (P. pipistrellus) and Nathusius´ pipistrelle (P. nathusii) in relation to landscape composition.

Changes in land use can modify habitat and roosting behaviour of bats, and therefore the transmission dynamics of viruses. Within bat roosts the density and contact rate among individuals increase and may facilitate the transmission of bat coronaviruses (CoVs). Landscape components supporting larger bat populations may thus lead to higher CoVs prevalence, as the number of roosts and/or roost size are likely to be higher. Hence, relationships between landscape composition and the presence of CoVs are expected to exist. To increase our understanding of the spread and shedding of coronaviruses in bat populations we studied the relationships between landscape composition and CoVs prevalence in the species Pipistrellus pipistrellus and Pipistrellus nathusii. Faecal samples were collected across The Netherlands, and were screened to detect the presence of CoV RNA. Coordinates were recorded for all faecal samples, so that landscape attributes could be quantified. Using a backward selection procedure on the basis of AIC, the landscape variables that best explained the presence of CoVs were selected in the final model. Results suggested that relationships between landscape composition and CoVs were likely associated with optimal foraging opportunities in both species, e.g. nearby water in P. nathusii or in areas with more grassland situated far away from forests for P. pipistrellus. Surprisingly, we found no positive association between built-up cover (where roosts are frequently found) and the presence of bat-CoVs for both species. We also show that samples collected from large bat roosts, such as maternity colonies, substantially increased the probability of finding CoVs in P. pipistrellus. Interestingly, while maternity colonies of P. nathusii are rarely present in The Netherlands, CoVs prevalence was similar in both species, suggesting that other mechanisms besides roost size, participate in the transmission of bat-CoVs. We encourage further studies to quantify bat roosts and colony networks over the different landscape compositions to better understand the ecological mechanisms involved in the transmission of bat-CoVs.

A population in perpetual motion: Highly dynamic roosting behavior of a tropical island endemic bat.

Although island endemic bats are a source of considerable conservation concerns, their biology remains poorly known. Here, we studied the phenology and roosting behavior of a tropical island endemic species: the Reunion free-tailed bat (Mormopterus francoismoutoui). This widespread and abundant species occupies various natural and anthropogenic environments such as caves and buildings. We set up fine-scale monitoring of 19 roosts over 27 months in Reunion Island and analyzed roost size and composition, sexual and age-associated segregation of individuals, as well as the reproductive phenology and body condition of individuals. Based on extensive data collected from 6721 individuals, we revealed a highly dynamic roosting behavior, with marked seasonal sex-ratio variation, linked to distinct patterns of sexual aggregation among roosts. Despite the widespread presence of pregnant females all over the island, parturition was localized in a few roosts, and flying juveniles dispersed rapidly toward all studied roosts. Our data also suggested a 7-month delay between mating and pregnancy, highlighting a likely long interruption of the reproductive cycle in this tropical bat. Altogether, our results suggest a complex social organization in the Reunion free-tailed bat, with important sex-specific seasonal and spatial movements, including the possibility of altitudinal migration. Bat tracking and genetic studies would provide additional insights into the behavioral strategies that shape the biology of this enigmatic bat species. The fine-scale spatiotemporal data revealed by our study will serve to the delineation of effective conservation plans, especially in the context of growing urbanization and agriculture expansion in Reunion Island.

Long‐term analysis of persistence and size of swallow and martin roosts in the US Great Lakes

AbstractIn this study, we combined a machine learning pipeline and human supervision to identify and label swallow and martin roost locations on data captured from 2000 to 2020 by 12 Weather Surveillance Radars in the Great Lakes region of the US. We employed radar theory to extract the number of birds in each roost detected by our technique. With these data, we set out to investigate whether roosts formed consistently in the same geographic area over two decades and whether consistency was also predictive of roost size. We used a clustering algorithm to group individual roost locations into 104 high‐density regions and extracted the number of years when each of these regions was used by birds to roost. In addition, we calculated the overall population size and analyzed the daily roost size distributions. Our results support the hypothesis that more persistent roosts are also gathering more birds, but we found that on average, most individuals congregate in roosts of smaller size. Given the concentrations and consistency of roosting of swallows and martins in specific areas throughout the Great Lakes, future changes in these patterns should be monitored because they may have important ecosystem and conservation implications.

Evaluation of roost culling as a management strategy for reducing invasive rose-ringed parakeet (Psittacula krameri) populations

Rose-ringed parakeets (Psittacula krameri) are one of the most widespread invasive avian species worldwide. This species was introduced to the island of Kaua‘i, Hawai‘i, USA, in the 1960s. The rapidly increasing population has caused substantial economic losses in the agricultural and tourism industries. We evaluated the efficacy of a roost culling program conducted by an independent contractor from March 2020 to March 2021. We estimated island-wide minimum abundance was 10,512 parakeets in January 2020 and 7,372 in April 2021. Over 30 nights of culling at four roost sites, approximately 6,030 parakeets were removed via air rifles with 4,415 (73%) confirmed via carcasses retrieval. An estimated average of 45 parakeets were removed per hour of shooter effort. The proportion of adult females removed in 2020 was 1.9 × greater when culled outside of the estimated nesting season. Of the four roosts where culling occurred, the parakeets fully abandoned three and partially abandoned one site. Of the three fully abandoned roosts, an estimated average of 29.6% of birds were culled prior to roost abandonment. The roost culling effort was conducted during the COVID-19 pandemic, when tourist numbers and foot traffic were greatly reduced. It is unknown how public perception of roost culling in public areas may impact future efforts. Findings suggest roost culling can be utilized for management of nonnative rose-ringed parakeet populations when roost size is small enough and staff size large enough to cull entire roosts in no greater than two consecutive nights (e.g., if two shooters are available for three hours per night, roost culling should only be attempted on a roost with ≤ 540 rose-ringed parakeets).

Rewarming rates of seven insectivorous bat species along an altitudinal gradient in South Africa

Small endotherms commonly use daily torpor to maintain energetic homeostasis. During daily torpor, rewarming rates have a large impact on overall energy savings because they influence heat loss in this energetically costly phase of torpor. These rates are affected by both intrinsic and extrinsic ecological factors; however, data on rewarming rates along temporal and spatial scales between and within species are scant. We investigated how seven insectivorous bat species differing in body size and thermal stability of preferred roosts vary in rewarming rates along an altitude gradient (0–1400 m.a.s.l.) in South Africa, predicting that rewarming rates would increase with altitude. We kept individuals overnight at 15°C and monitored their surface temperature during induced rewarming with infrared thermal imaging to calculate rewarming rates. In contrast to our prediction, we found no significant variation between species or altitudes despite differences in body mass and life history traits. However, we did find evidence that males rewarmed more rapidly than females at low temperatures despite the higher energetic cost of slow rewarming, possibly due to reluctance of females to initiate active rewarming at low ambient temperatures. We found some support for the prediction that cool temperatures at high altitude result in lower initial surface temperatures during cold-exposure, as an adaptation to mitigate heat loss through thermal conductance to the ambient environment. This is particularly important for small insectivorous bats given their high surface area to volume ratios.

The Ecology of Nipah Virus in Bangladesh: A Nexus of Land-Use Change and Opportunistic Feeding Behavior in Bats.

Nipah virus is a bat-borne paramyxovirus that produces yearly outbreaks of fatal encephalitis in Bangladesh. Understanding the ecological conditions that lead to spillover from bats to humans can assist in designing effective interventions. To investigate the current and historical processes that drive Nipah spillover in Bangladesh, we analyzed the relationship among spillover events and climatic conditions, the spatial distribution and size of Pteropus medius roosts, and patterns of land-use change in Bangladesh over the last 300 years. We found that 53% of annual variation in winter spillovers is explained by winter temperature, which may affect bat behavior, physiology, and human risk behaviors. We infer from changes in forest cover that a progressive shift in bat roosting behavior occurred over hundreds of years, producing the current system where a majority of P. medius populations are small (median of 150 bats), occupy roost sites for 10 years or more, live in areas of high human population density, and opportunistically feed on cultivated food resources—conditions that promote viral spillover. Without interventions, continuing anthropogenic pressure on bat populations similar to what has occurred in Bangladesh could result in more regular spillovers of other bat viruses, including Hendra and Ebola viruses.

Historic and contemporary use of catfish aquaculture by piscivorous birds in the Mississippi Delta

AbstractPiscivorous birds are the primary source of catfish (Ictalurus spp.) depredation at aquaculture facilities in northwestern Mississippi. Of particular concern is the Double-crested Cormorant (Phalacrocorax auritus), which can cost aquaculture producers millions of dollars annually through the depredation of cultured fish. Historical research conducted in the early 2000s estimated cormorant use of aquaculture ponds in the region, but aquaculture area has decreased by more than 70% since those estimates were made. With less aquaculture available, we predicted cormorant densities on aquaculture would be greater today than historically. Applying a similar methodology as in historical studies, we used aerial surveys to collect data on cormorants at night roosts and using catfish aquaculture ponds during 3 consecutive winter seasons, beginning in 2015. Although the mean annual number of cormorants at roosts in the Delta during our study was 64% less than historically, we found no significant change in densities on aquaculture, suggesting that aquaculture area is likely the factor influencing cormorant occurrence in northwestern Mississippi. During contemporary surveys we also measured the abundance of Great Blue Herons (Ardea herodias) and Great Egrets (A. alba) on the aquaculture clusters, and built predictive models of abundance relative to variables associated with forage at and surrounding the clusters. We found abundance of all 3 species was strongly related to the amount of aquaculture area both within and surrounding a cluster, although patterns varied by species. Cormorant abundance was also greater on clusters with proportionately more food fish (≥20 cm in length) than fingerlings (<20 cm) and was positively related to the proximity and size of night roosts. The relationships described here can be used by producers and wildlife managers to predict the abundance of these piscivorous birds at aquaculture facilities and to design efficient management plans to mitigate potential impacts of depredation and disease.

Usage of buildings in the life cycle of two endangered Rhinolophus species in the Mediterranean region: implications for roost protection

Synanthropic roosting may allow cave-dwelling bats to cope with habitat fragmentation provided that suitable buildings are sustainably protected. This study on Asinara Island, Sardinia, focuses on roost requirements in synanthropy at different life stages of two endangered bat species, Rhinolophus hipposideros and Rhinolophus ferrumequinum. We rated the roost potential of 532 buildings and compared it with actual roost usage. Microclimate was compared across different roost types and between species, and bat composition and behaviour in nurseries of R. hipposideros were related to roost structure and microclimate. The two species occupied 25% of structures rated as “high potential”, versus 5% and 0% rated as “intermediate” and “low potential”. Concerning microclimate, R. hipposideros preferred warmer and drier day roosts, with higher temperature fluctuations during summer, while winter, and night, roost microclimate was comparable between species. In larger, warmer, and drier nurseries, colony size and proportion of reproductive females were higher and parturition started earlier. Before parturition, roost temperatures were inversely correlated to clustering, supporting its thermoregulatory function. Mothers spent in total 50% of the night inside the nursery caring the pup. Roost microclimate, size, and location close to foraging areas may thus promote breeding success. We conclude that a structure-based rating of roost potential supplemented by species-specific microclimatic requirements constitutes a promising predictor of roost usage. Moreover, adequate buildings support the complete life cycle of R. hipposideros in the absence of suitable caves. Buildings thus deserve increased protection measures in fragmented Mediterranean landscapes to ensure sustainable bat conservation.

Evidence for Communal Roost Size Regulation in Heliconius erato Butterflies (Nymphalidae)

Communal roosting behavior in Heliconius passion-vine butterflies has fascinated scientists for centuries. Despite recent research on the complex dynamics involved with this behavior, little work has been done to examine whether butterflies regulate their communal roost sizes and if there is preference to form roosts of a particular size. Here I present results from two studies, that tested 1) whether wild-captured Heliconius erato butterflies, exposed to different roost sizes in captivity, prefer to join small, medium, or large-sized roosts; and 2) whether established H. erato butterflies in natural wild populations abandon roosts when they become too large. In captivity, butterflies significantly preferred to join small- and medium-sized aggregations, and avoided large aggregations, when introduced to a new environment. In the wild, butterfly attendance decreased significantly as roost size increased, showing that butterflies leave natural roosts when they become too large or crowded. Although a number of potential explanations exist for the adaptive significance of communal roost size regulation in H. erato, one of the most striking details about these results are that preferred roost size by individual butterflies corresponds with the average number of butterflies found in natural roosts. This preferred roost size also overlaps with previous studies showing an experimentally optimal roost size with the same number of butterflies (for anti-predatory benefits), in this species in this same field location. These results combine multiple sources of evidence from old and new data suggesting that optimal communal roost sizes exist in Heliconius and that the butterflies regulate their roost sizes in their home ranges. Further studies are welcome to help understand the decision-making process used by these butterflies for joining – or abandoning – communal roosts.

Ecological determinants of pathogen transmission in communally roosting species

Many animals derive benefits from roosting communally but may also face increased risk of infectious disease transmission. In spite of recent high-profile disease outbreaks in roosting animals of conservation and public health concern, we currently lack general theory for how attributes of roosting animals and their pathogens influence pathogen spread among roosts and overall population impacts on roosting species. Here we develop a model to explore how roost size and host site fidelity influence the time for a pathogen to escape from its initial roost, overall infection prevalence, and host population size, for pathogens with density- or frequency-dependent transmission and varying virulence. We find that pathogens spread rapidly to all roosts when animals are distributed among a small number of large roosts, and that roost size more strongly influences spread rate for density-dependent than frequency-dependent transmitted pathogens. However, roosting animals that exhibit high site fidelity and distribute among a large number of small roosts are buffered from population-level impacts of pathogens of both transmission modes. We discuss our results in the context of anthropogenic change that is altering aspects of roosting behavior relevant to emerging pathogen spread.

In artificial roost comparison, bats show preference for rocket box style.

Understanding microhabitat preferences of animals is critical for effective conservation, especially for temperate-zone bats, which receive fitness benefits from selecting optimal roost microhabitats. Artificial roost structures are increasingly being used in conservation efforts for at-risk bat species. To evaluate microhabitat differences in common artificial roost structures and determine if roost selection occurs based on structure type, we installed artificial roosts of three different styles (bat box, rocket box, and bark mimic) in six clusters. We compared size and measured temperature parameters (12 points/roost) while bats were excluded from one cluster. We simultaneously conducted census counts during the active season at five more clusters open to bats for 1–2 years. The rocket box style provided larger entrance area, surface area, and volume versus other roost types. Microclimate varied with roost design. More positions inside the bat box and rocket box stayed within critical temperature limits for bats (0–45°C)—i.e., were usable. The bark-mimic provided less usable space than the rocket box and, often, large proportions of the roost were > 45°C. The rocket box provided the widest temperature availability in a given hour (max range available 7°C) and was more stable than the bark mimic. A maternity colony of Indiana bats (Myotis sodalis) selected the rocket box style; four of five available rocket boxes became primary maternity roosts, with 2–210 bats emerging per night. Future work should aim to manipulate roost size, temperature availability, and temperature stability in isolation to identify which features drive roost microhabitat selection by bats. Comparative studies of artificial roosts account for some inherent irregularity in natural systems, allowing us to study the dynamics of roost microhabitats. We recommend season-long monitoring of microhabitat in novel artificial refuges and comparative studies of artificial and natural roosts, and urge managers to consider potential positive and negative effects when substituting artificial roosts for natural habitat.

Roosting, Foraging and Mating Behaviour of Indian Flying Fox (Pteropus Giganteus) in Rourkela, Odisha

A reconnaissance survey was carried out to investigate the roosting, foraging and mating behaviour of the Indian flying fox (Pteropus giganteus) in Rourkela, Odisha during 20th February 2016-5th March 2017. A total of 8 roosting sites were identified, Parks (1), temples (3), police stations (2), courts (1), and on the bank of the Koel river. They roosted on 19 tree species belonging to 18 genera and 11 families. Roost size varied from 43 to 6141 individuals, depending on the habitat and preferred tree species. It was found that they forage both in groups as well as alone. They foraged twice a day. Their diet included fruits, nectar and petals of some flowers, belonging to 23 species 21 genera and 12 families. Two mating seasons were recorded. During the mating process, male tried to approach the female and fanned its patagium and spread it around the female, trying to hold her, but the female tried to escape from the male. Male copulated successfully for 20-42 seconds. Females involved in copulation gave birth to young ones around April-June with a gestation period of 145-160 days . Maternal care was observed. Tactile communication was observed between mother and the Pup. Pups became matured within 1.5 years.

Assessing Bat Roosts Using the LiDAR System at Wind Cave Nature Reserve in Sarawak, Malaysian Borneo

Conventionally, bat roost counts and roost size estimation are potentially a disruptive, repetitive method and are time consuming. Introduction of the Light Detection and Ranging (LiDAR) scanning system, an optical remote sensing technology, for scientific purposes have open many research possibilities especially on cave wildlife surveys. Scanned images at high resolution provide new effective biological tools for assessing bat roosts inside caves on walls or ceiling in total darkness. LiDAR system was applied to census bats that roost in Wind Cave Nature Reserve, Sarawak, Malaysia, based on laser return intensity values from the images. Bats that roost in large clusters, specifically Penthetor lucasi were determined through automated counting using connected components labelling, a graph theory algorithm mostly used in image analysis applications. Roost surface area of bats species was calculated based on point clouds extracted and using simple trigonometry. Wind Cave was successfully modelled into three dimensional (3D) cave images with bats roosting inside the cave. The roost sites of bats in the cave were represented in coloured point clouds that represent the species. Through LiDAR images, bats in Wind Cave consisted of about 979 individuals of P. lucasi and 1,907 individuals of insectivorous bats from nine species representing four families. There is a positive correlation between group size and roost area. For every additional bat, roost area is expected to increase by an average of 1.75 m2. Our result suggested that terrestrial LiDAR technology is capable of assessing bat roosts in their natural habitat to determine their roost size and number of individuals that roost in the cave. Terrestrial LiDAR application is most complementary when integrated with field surveys to produce more reliable outcomes which open up possibilities of effective conservation action plans.

How Does Africa's Most Hunted Bat Vary Across the Continent? Population Traits of the Straw-Coloured Fruit Bat (Eidolon helvum) and Its Interactions with Humans

The straw-coloured fruit bat, Eidolon helvum, is a common and conspicuous migratory species, with an extensive distribution across sub-Saharan Africa, yet hunting and habitat loss are thought to be resulting in decline in some areas. Eidolon helvum is also a known reservoir for potentially zoonotic viruses. Despite E. helvum's importance, ecological and behavioural traits are poorly described for this species. Here we present extensive data on the distribution, migration patterns, roost size, age and sex composition of 29 E. helvum roosts from nine countries across tropical Africa, including roosts not previously described in the literature. Roost age and sex composition were dependent on timing of sampling relative to the annual birth pulse. Rather than a single ‘breeding season’ as is frequently reported for this species, regional asynchrony of reproductive timing was observed across study sites (with birth pulses variably starting in March, April, September, November or December). Considered together with its genetic panmixia, we conclude that the species has a fluid, fission-fusion social structure, resulting in different roost ‘types’ at different times of the year relative to seasonal reproduction. Bat-human interactions also varied across the species' geographical range. In the absence of significant hunting, large urban colonies were generally tolerated, yet in regions with high hunting pressure, bats tended to roost in remote or protected sites. The extensive quantitative and qualitative data presented in this manuscript are also valuable for a wide range of studies and provide an historical snapshot as its populations become increasingly threatened.

Social organization of an endangered subtropical species, Eumops floridanus, the Florida bonneted bat

Abstract Many Chiropteran species are gregarious, yet much remains to be learned about details of the sociality of most species. This is especially true for the endangered Eumops floridanus (Florida bonneted bat). Scant knowledge of the species’ natural history and ecological interactions has precluded the development of effective conservation strategies. We investigated several aspects of the social organization of E. floridanus roosting in bat houses in southwest Florida: group size, group composition, group stability, and seasonality of reproduction. Our findings suggest the species has characteristics more common to tropical bat species than temperate ones. The average roost size was 10 individuals, with colonies in a harem social structure all three times in the year they were assessed. Adults were much more likely than sub-adults to be recaptured at the same roosts during subsequent capture sessions. We suggest that the availability and distribution of roosts may alter the social structure of these bats and ultimately limit local populations. We did not find evidence of a distinct seasonal birthing period matching that of other temperate bat species. Results suggests the species is aseasonally polyestrous, making non-volant E. floridanus vulnerable to disturbance across a larger portion of the year than other bat species in the US.

Seeing the Forest through the Trees: Considering Roost-Site Selection at Multiple Spatial Scales.

Conservation of bat species is one of the most daunting wildlife conservation challenges in North America, requiring detailed knowledge about their ecology to guide conservation efforts. Outside of the hibernating season, bats in temperate forest environments spend their diurnal time in day-roosts. In addition to simple shelter, summer roost availability is as critical as maternity sites and maintaining social group contact. To date, a major focus of bat conservation has concentrated on conserving individual roost sites, with comparatively less focus on the role that broader habitat conditions contribute towards roost-site selection. We evaluated roost-site selection by a northern population of federally-endangered Indiana bats (Myotis sodalis) at Fort Drum Military Installation in New York, USA at three different spatial scales: landscape, forest stand, and individual tree level. During 2007–2011, we radiotracked 33 Indiana bats (10 males, 23 females) and located 348 roosting events in 116 unique roost trees. At the landscape scale, bat roost-site selection was positively associated with northern mixed forest, increased slope, and greater distance from human development. At the stand scale, we observed subtle differences in roost site selection based on sex and season, but roost selection was generally positively associated with larger stands with a higher basal area, larger tree diameter, and a greater sugar maple (Acer saccharum) component. We observed no distinct trends of roosts being near high-quality foraging areas of water and forest edges. At the tree scale, roosts were typically in American elm (Ulmus americana) or sugar maple of large diameter (>30 cm) of moderate decay with loose bark. Collectively, our results highlight the importance of considering day roost needs simultaneously across multiple spatial scales. Size and decay class of individual roosts are key ecological attributes for the Indiana bat, however, larger-scale stand structural components that are products of past and current land use interacting with environmental aspects such as landform also are important factors influencing roost-tree selection patterns.

Roost and diet selection by Southern Spotted Owlet Athene brama brana (Temminck, 1821) in the Cauvery Delta of Nagapattinam District, southern India

The Spotted Owlet Athene brama is the commonest among the 62 species of owls of India and also a widely distributed bio-control agent of agricultural pests in India. We studied the roost site selection and diet composition of the Southern Spotted Owlet A.b. brama in the Cauvery Delta in southern India during 2007-08. The roost selection evaluated based on roost site characteristics observed from 22 roost sites revealed that the owlets preferred to roost closer to human habitation than in agricultural fields, with all the roosts found among trees. Albizia saman (Rain Tree) was the most commonly used roost tree species. Tree species with 20-30 m height and 1-3 m gbh were most preferred for roosting due to the presence of a greater number of branches. Roost species and size class selection appeared to depend on availability of suitable locations with better protection from weather and concealment to avoid disturbance from humans and other birds. Diet composition examined through analysis of 55 regurgitated pellets revealed that undigested food items from insects constituted the bulk of the owls diet (57%) followed by mammals (rodents) (24.4%), reptiles (7.8%) and birds (7.3%). However, it is argued that mammals in the form of digestible parts could have contributed more to the diet of the owlet than any other taxa. Higher consumption of rodents and insects is discussed in the light of reducing agricultural pests; adequate roosting sites (mature trees) and creating awareness among the local community about the role of Spotted Owlets will improve their population and help control agricultural pests more effectively.

アユの大量放流はカワウのねぐらやコロニーの分布に影響するか

アユの大量放流はカワウのねぐらやコロニーの分布に影響するか

Bat conservation in China: should protection of subterranean habitats be a priority?

AbstractSubterranean environments are essential for the survival of many bat species and other cave fauna but these places are subject to increasing human disturbance. To examine the significance of subterranean habitats for the conservation of bats in China we surveyed bat species in 225 underground sites during 2003–2011. Our results show that 77% of bat species in China, including 30 nationally Endangered or Vulnerable species and nine endemic species, roost in caves and other subterranean habitats. The number of species in occupied roosts was 1–15. Almost 90% of the roosts surveyed contained signs of human disturbance, most of which was from recreational activities. One hundred and twenty-one roosts merit special concern because they harbour ≥ 6 species or > 1,000 individuals, or species of special concern (threatened or endemic species). Generally, larger roosts support more species and a greater abundance of bats than smaller roosts but there is no direct correlation between the presence of species of special concern and roost size. Disused tourist caves have significantly more bat species than other types of roosts. Our data demonstrate that roost disturbance by recreational activities has pronounced detrimental effects on the number of bat species and the presence of species of special concern. We discuss the social, economic and political issues that could adversely affect bat conservation in caves in China, and we recommend that protection of subterranean habitats should be a high priority for bat conservation.