Van der Meij T.,Statistics Netherlands CBS |
Van Strien A.J.,Statistics Netherlands CBS |
Haysom K.A.,Bat Conservation Trust |
Dekker J.,Dutch Mammal Society |
And 16 more authors.
Mammalian Biology | Year: 2015
Monitoring data on hibernating bats were aggregated for the first time across a number of European countries. These supranational trends revealed that nine out of 16 bat species examined increased at their hibernation sites in Europe between 1993 and 2011, while only one is decreasing. This is reflected in the positive trend shown by a prototype multispecies bat indicator which combined the individual species trends. Our findings suggest that after a period of strong decline in the 20th century, populations of most of the investigated bat species are stabilising or recovering, although with profound differences between European bio-geographical regions and countries. Bat populations in the Continental region have a less positive tendency, compared to those in the Atlantic region. More data from more countries may reveal whether these differences are systematical. So far, the prototype indicator covers 9 countries and 16 of the 45 bat species found in Europe. The next steps will be to refine the methodology behind the indicator and to improve the indicator's representation of European bat populations and its capacity to compare trends among biogeographic regions. This should be achieved by participation of more countries and incorporating data from additional bat species, including data collected by other surveillance methods, such as summer roost counts. Robust information on trends in bat populations at a range of geographic scales is essential to the long-term conservation of bats. Further development of this indicator will make an important contribution to conservation of bats because it will stimulate international cooperation and capacity building for monitoring and research, thus exchanging and broadening knowledge of the status of bats and improving the identification of threats. © 2014 Deutsche Gesellschaft für Säugetierkunde.
Van Schaik J.,Max Planck Institute for Ornithology (Seewiesen) |
Janssen R.,Bionet Natuuronderzoek |
Bosch T.,Ad Hoc Zoogdieronderzoek |
Haarsma A.-J.,Radboud University Nijmegen |
And 3 more authors.
PLoS ONE | Year: 2015
During autumn in the temperate zone of both the new and old world, bats of many species assemble at underground sites in a behaviour known as swarming. Autumn swarming behaviour is thought to primarily serve as a promiscuous mating system, but may also be related to the localization and assessment of hibernacula. Bats subsequently make use of the same underground sites during winter hibernation, however it is currently unknown if the assemblages that make use of a site are comparable across swarming and hibernation seasons. Our purpose was to characterize the bat assemblages found at five underground sites during both the swarming and the hibernation season and compare the assemblages found during the two seasons both across sites and within species. We found that the relative abundance of individual species per site, as well as the relative proportion of a species that makes use of each site, were both significantly correlated between the swarming and hibernation seasons. These results suggest that swarming may indeed play a role in the localization of suitable hibernation sites. Additionally, these findings have important conservation implications, as this correlation can be used to improve monitoring of underground sites and predict the importance of certain sites for rare and cryptic bat species. Copyright: © 2015 van Schaik et al.
van Strien A.J.,Statistics Netherlands |
Meyling A.W.G.,Statistics Netherlands |
Meyling A.W.G.,Anemoon Foundation |
Herder J.E.,Reptile |
And 11 more authors.
Biological Conservation | Year: 2016
We calculated a Living Planet Index (LPI) for the Netherlands, based on 361 animal species from seven taxonomic groups occurring in terrestrial and freshwater habitats. Our assessment is basically similar to the global LPI, but the latter includes vertebrate species and trends in population abundance only. To achieve inferences on trends in biodiversity more generally, we added two insect groups (butterflies and dragonflies) and added occupancy trends for species for which we had no abundance trends available. According to the LPI, the state of biodiversity has slightly increased from 1990 to 2014. However, large differences exist between habitat types. We found a considerable increase in freshwater animal populations, probably because of improvement of chemical water quality and rehabilitation of marshland habitats. We found no trend in the LPI for woodland populations. In contrast, populations in farmland and open semi-natural habitats (coastal dunes, heathland and semi-natural grassland) declined, which we attribute to intensive agricultural practices and nitrogen deposition, respectively. The LPI shows that, even in a densely populated western European country, ongoing loss of animal biodiversity is not inevitable and may even be reversed if adequate measures are taken. Our approach enabled us to produce summary statistics beyond the level of species groups to monitor the state of biodiversity in a clear and consistent way. © 2016 The Authors
Van Strien A.J.,Statistics Netherlands |
Van Strien A.J.,University of Amsterdam |
Dekker J.J.A.,Dutch Mammal Society |
Straver M.,Statistics Netherlands |
And 4 more authors.
Wildlife Research | Year: 2011
Context Wild rabbits are considered a key species in the coastal dunes of the Netherlands, but populations have collapsed as a result of viral diseases. Aim We studied to what extent population collapse led to local extinction and whether recolonisation of empty patches in the dunes happened. Methods We investigated occupancy dynamics using data of 245 transects where rabbits were surveyed in 19842009. Dynamic site-occupancy models were used to analyse the data. These models adjust for imperfect detection to avoid bias in occupancy-trend estimation. Key results The decline of the rabbit population has resulted in many local extinctions, especially in woodland and in the northern part of the coastal dunes. Most transects along grassland and mixed vegetation have recently been reoccupied. The recovery of woodland occupancy is slow, probably not because of limited dispersal capacity of rabbits, but because the quality of woodland habitats is poor. Detection probability of rabbits varied considerably over the years and among habitat types, indicating the necessity of taking detection into account. Rabbits were slightly better detected when it was cloudy, windy and rainy and when lunar phase approached new moon. Conclusion Extinction and recolonisation of habitat patches varied considerably among habitat types. Implications The current slow recolonisation hampers the recovery of rabbit populations in woodland habitats in the Dutch coastal dunes. Furthermore, monitoring rabbit occupancy should take imperfect detection into account to avoid biased results. © CSIRO 2011.
Jonker M.N.,Wageningen University |
Boer W.F.D.,Wageningen University |
Kurvers R.H.J.M.,Wageningen University |
Dekker J.J.A.,Dutch Mammal Society
Acta Chiropterologica | Year: 2010
Decision making by animals is likely to be influenced strongly by the behaviour of conspecifics. In this study we tested whether public information affected the foraging behaviour of common pipistrelles (Pipistrellus pipistrellus) by manipulating public information about the quality of foraging patches. Capture attempts during foraging are revealed by terminal buzzes, which are a potential source of public information about prey abundance for other foraging bats. We tested whether the estimation of food patch quality was affected by the number of terminal buzzes emitted by conspecifics. We conducted an experiment at 12 different locations in an urban habitat in the Netherlands. At each location we played back recordings of echolocation sounds of hunting bats with different terminal buzz rates and scored the bat activity. No significant differences between treatments were found. Our results do not support the hypothesis that bat activity increases in response to an increase in simulated terminal buzzes, suggesting that public information does not influence the choice of foraging patches in P. pipistrellus. We propose that P. pipistrellus does not use this kind of information because of either the high reliability of personal information or of the low collection costs associated with personal information. © Museum and Institute of Zoology PAS.
van Strien A.J.,Statistics Netherlands |
Bekker D.L.,Dutch Mammal Society |
La Haye M.J.J.,Dutch Mammal Society |
van der Meij T.,Statistics Netherlands
Mammalian Biology | Year: 2015
The EU Habitats Directive prescribes the monitoring of several small mammals on a national scale. A cost-effective way of monitoring these species is by using owl pellet data. Unfortunately, owl pellet data suffer from several methodological difficulties, all associated with the imperfect detection of the presence of prey species. Occupancy models can overcome the difficulties by taking detection into account, but they require temporal replicates. To supply these, we created replicates by splitting each pellet batch into two equal parts. A pellet batch consists of a number of pellets collected together in the field.Here we show how occupancy models can be applied to derive trend estimates from owl pellet data using such half batches as temporal replicates. We justify this approach by showing that the results from occupancy models treating half batches as temporal replicates in a test dataset were similar to the results of treating individual pellets as temporal replicates.The owl species and the number of prey individuals examined were included in the occupancy model applied to all data. We studied eleven small mammal species, two of which showed positive trends in occupancy. The confidence intervals of the trend estimates were satisfactorily small. Our methodological innovations reinforce the usefulness of pellet data for trend estimation in small mammals and increase the feasibility of large-scale monitoring of such species under the Habitats Directive. © 2015 Deutsche Gesellschaft für Süugetierkunde.