R. Janssen

Bats Swarm Where They Hibernate : Compositional Similarity between Autumn Swarming and Winter Hibernation Assemblages at Five Underground Sites

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.

Swarming Behaviour, Catchment Area and Seasonal Movement Patterns of the Bechstein's Bats: Implications for Conservation

Bats display marked seasonality throughout the temperate zone and use different habitats during different parts of the year. Unfortunately, detailed information regarding seasonal distribution and movements is often lacking, thereby hampering the development of adequate conservation measures. In this study we used radio telemetry to track females of the endangered Bechsteins bat (Myotis bechsteinii) from autumn swarming sites to their summer maternity colony ranges. We were able to tag 22 individuals, 18 of which were subsequently recovered at nine roost sites up to 20.6 km away. Females from multiple colonies visited the same swarming site on a single night. Concurrently, we recovered females from a single maternity colony at different swarming sites on the same night. The catchment area of the investigated swarming sites measured 27.1 km2, and was skewed to the northwest. Tagged bats were recovered in forest fragments ranging in size from 5.42 to 128.98 ha. Notably, all but one of the recovered roosts were found in forests that have been continuously wooded since at least 1775. Surveys during the summer at these sites confirmed the presence of maternity colonies at six out of seven locations that could be investigated. Our study contributes to our understanding of swarming behavior and seasonal movement patterns, and exemplifies how these can be used to complete the year-round habitat use of bat species.

A MULTI OBJECTIVE DECISION SUPPORT SYSTEM FOR PUBLIC PLANNING

Our decision support system DEFINITE is intended to support decisions with a finite set of alternatives in relation to a finite number of criteria. It can be used to generate, compare and evaluate alternatives as a preparation to policy decisions. The system intends to function as a learning, comminication and decision making tool for one or more decision makers.

Ein Hilfssystem zur Entscheidungsfindung für das Management Schadstoffbelasteter Böden

Nach den Bestimmungen des vorlaufigen Gesetzes zur Bodensanierung mussen in den Niederlanden 6000 Altlasten dringend saniert werden. Die zur Losung dieses Problems verfugbaren Mittel sind beschrankt, wahrend die geschatzten jahrlichen Kosten der Sanierung Dfl. 500.000.000,- betragen. Wegen der Komplexitat der beteiligten Faktoren ist die Ermittlung einer angemessenen Sanierungsstrategie schwierig. Die Sanierungsmasnahmen mussen speziell auf den Schadstofftyp, die Art des Bodens, die geologischen und hydrologischen Eigenschaften und die Nutzung des Bodens abgestimmt werden. Daruber hinaus sind die Daten, die zu verschiedenen Aspekten des Problems verfugbar sind, nicht klar strukturiert und den Entscheidungstragern deshalb nicht einfach zuganglich. Diese Situation macht deutlich, das ein systematischer Ansatz benotigt wird, der einerseits kosteneffiziente und umweltvertragliche Optionen fordert und andererseits konsistente und transparente Entscheidungen erleichtert.

A Decision Support System for Management of Polluted Soils

In the Netherlands 6000 contaminated sites urgently require remedial action according to the rules set in the Interim Soil Clean-Up Act. The available funds for the solution of this problem are limited, but the estimated yearly costs for the clean-up operation are Dfl. 500,000,000. Determination of appropriate remediation strategies is difficult, due to the complexity of factors involved. Clean-up activities are specific to contaminant type, the nature of the soil, geological and hydrological features and the use of the location. Moreover, data available on various aspects of the subject are not well structured and therefore not easily accessible to decision makers. This situation emphasizes the need for a systematic approach, that supports cost-effective and environmentally sound choices and facilitates a uniform and transparant decision.