Abstracts - Deutsche Zoologische Gesellschaft

60 Ecology SymposiumO EC.15 (Mo) - DEWetness-based activation of traps in carnivorous pitcher plantsUlrike Bauer, Walter FederleDepartment of Zoology, University of Cambridge, UKNepenthes pitcher plants have highly specialized leaves to attract, capture, retain and digest arthropodprey. Several capture mechanisms have been proposed, ranging from slippery wax crystals todownward-pointing cells and anesthetizing alkaloid secretions. We recently discovered that in manypitcher plants, insects are captured when slipping on the upper pitcher rim (peristome). Unlike mostother plant surfaces, the peristome is completely wettable, and thin water films cover the surface underhumid conditions. Insects loose their foothold on these water films, similar to the ‘aquaplaning’of a car tyre on a wet road. To investigate the ecological implications of this mechanism, we combinedcontinuous measurements of peristome wetness and meteorological data with experimentalassessments of the pitchers’ capture efficiency in the field. We found that pitchers can be temporarilyhighly effective with capture rates up to 80% but completely ineffective at other times. These dramaticchanges are due to the wetting condition of the peristome. Variation of peristome wetness andcapture efficiency was perfectly synchronous, and caused by rain, condensation, and nectar secretedfrom extrafloral nectaries. We propose that the intermittent and unpredictable activation of Nepenthespitcher traps facilitates ant recruitment and constitutes a strategy to maximize prey capture.O EC.16 (Mo) - ENSleeping single in a double bed? Social hibernation in a tropical primate species(Cheirogaleus medius) – possible causes and consequencesKathrin DausmannDepartment of Ecology & Conservation, University of HamburgCold periods are energetically demanding for small endotherms that have to keep up a comparativelyhigh body temperature, especially as cold seasons usually coincide with periods of restricted foodavailability. The fat-tailed dwarf lemur (Cheirogaleus medius) has found an intriguing way to escapethis dilemma during the cool dry season of western Madagascar. It hibernates for up to seven monthsin tree holes. C. medius lives in life-long pairs and during the activity season the couples share sleepingsites in tree holes for more than 60% of the days. It is known from temperate zones that groupliving during hibernation is crucial for the maximisation of energy savings or even mere survival. Itmay therefore seem surprising that C. medius hibernates in all kinds of group sizes and has no preferencefor social hibernation. In fact, the percentage of days spent together during the hibernationseason decreases to about 40%. During hibernation, the lemurs show a very unusual, flexible patternof body temperature and metabolic rate, depending on the insulation capacities of the tree holes usedas hibernaculum, as they adjust their T bto the prevailing temperature in the tree holes. This possiblyturns sleeping mates into a disturbing nuisance, rather than a benefit. Considering this exceptionalhibernation physiology it seems likely that social hibernation in this tropical species is not driven byenergetic demands. Other factors (social, ecological) may be of greater influence.