68 research outputs found

    Flagellar sensilla in male and female European beewolves, Philanthus triangulum F. (Hymenoptera: Sphecidae)

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    We investigated the morphology of the antennal sensilla of a sphecid wasp, the European beewolf Philanthus triangulum, to provide an inventory for the species and to compare the sensillar equipment between the sexes. The density of sensilla increased from the base to the tip of the antennae. We distinguished nine different types of sensilla. One type has not yet been described in Hymenoptera. The large sensilla basiconica occurred only on the antennae of female beewolves. We discuss the functional significance of the difference between the sexes and compare our results with data from other sphecids and the honeybee Apis mellifera

    Clouded leopards, the secretive top-carnivore of South-East Asian rainforests: their distribution, status and conservation needs in Sabah, Malaysia

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    BACKGROUND: The continued depletion of tropical rainforests and fragmentation of natural habitats has led to significant ecological changes which place most top carnivores under heavy pressure. Various methods have been used to determine the status of top carnivore populations in rainforest habitats, most of which are costly in terms of equipment and time. In this study we utilized, for the first time, a rigorous track classification method to estimate population size and density of clouded leopards (Neofelis nebulosa) in Tabin Wildlife Reserve in north-eastern Borneo (Sabah). Additionally, we extrapolated our local-scale results to the regional landscape level to estimate clouded leopard population size and density in all of Sabah's reserves, taking into account the reserves' conservation status (totally protected or commercial forest reserves), their size and presence or absence of clouded leopards. RESULTS: The population size in the 56 km(2 )research area was estimated to be five individuals, based on a capture-recapture analysis of four confirmed animals differentiated by their tracks. Extrapolation of these results led to density estimates of nine per 100 km(2 )in Tabin Wildlife Reserve. The true density most likely lies between our approximately 95 % confidence interval of eight to 17 individuals per 100 km(2). CONCLUSION: We demonstrate that previous density estimates of 25 animals/100 km(2 )most likely overestimated the true density. Applying the 95% confidence interval we calculated in total a very rough number of 1500–3200 clouded leopards to be present in Sabah. However, only 275–585 of these animals inhabit the four totally protected reserves that are large enough to hold a long-term viable population of > 50 individuals

    Only distance matters - non-choosy females in a poison frog population

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    Background: Females have often been shown to exhibit preferences for certain male traits. However, little is known about behavioural rules females use when searching for mates in their natural habitat. We investigated mate sampling tactics and related costs in the territorial strawberry poison frog (Oophaga pumilio) possessing a lek-like mating system, where both sequential and simultaneous sampling might occur. We continuously monitored the sampling pattern and behaviour of females during the complete period between two successive matings. Results: We found no evidence that females compared males by visiting them. Instead females mated with the closest calling male irrespective of his acoustic and physical traits, and territory size. Playback experiments in the natural home ranges of receptive females revealed that tested females preferred the nearest speaker and did not discriminate between low and high call rates or dominant frequencies. Conclusions: Our results suggest that females of O. pumilio prefer the closest calling male in the studied population. We hypothesize that the sampling tactic in this population is affected by 1) a strongly female biased sex ratio and 2) a low variance in traits of available males due to strong male-male competition, preventing low quality males from defending a territory and mating

    A new ant-tree from SE Asia: Zanthoxylum myriacanthum (Rutaceae), the Thorny Ivy-Rue

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    Zanthoxylum myriacanthum, a small Rutaceous tree growing mainly in secondary hill forests in SE Asia, is a true myrmecophyte. It possesses stem domatia in the form of hollow branches with slitlike openings. Branch hollows and entrance slits are produced by the plant itself through pith degene~.tion ?u.d growth proceSses. If the entrance is not kept open by ants it closes again by growth ol the surrounding tissue after some time. The domatia are colonized opportunistic ally by different arboreous ants, e.g. Crematogaster and Campono tus. Additionally many small extrafloral nectaries are found on the leaflets of Zanthoxylum myriacanthum. Judging from herbarium studies and literature records at least four more true ant trees are found in the genus Zanthoxylum namely Z. rhetsa in SE Asia, Z. conspersipunctatum, Z. pluviatile and Z. vinkii in New Guinea. We could not confirm ant inhabitation in Drypetes pendula (Euphorbiaceae) on the Malay Peninsula, which has also been recorded to be an anttree

    The effect of climate on the distribution and abundance of isopods

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    Climate affects both the distribution and abundance of isopods. Humidity and moisture affect their activity and distribution. Survival of juveniles is largely dependent on moisture. The reproductive pattern is affected by temperature and light. Food affects growth and thus, indirectly, also reproduction, as larger females tend to produce larger broods and more frequent broods than smaller ones. Generally in isopods there is little evidence to suggest that food is a very important factor affecting their abundance. Both semelparity and iteroparity are found in isopods and both reproductive strategies are apparently successful. Mortality factors affect the oocytes, the marsupial stages, and most of all the newly released individuals . Apart from climatic factors, predation and, to a lesser extent, parasitism are the main causes of mortality. Longevity of isopods ranges from one to five years. Occasional population explosions ofisopods are known to take place, their cause being unknown

    Saving the injured: Evolution and mechanisms

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    Rescue behavior focused on injured individuals has rarely been observed in animals. These observations though are from very different taxa's: birds, mammals and social insects. Here we discuss likely antecedents to rescue behaviors in ants, like social carrying and alarm pheromones. We then compare similarities and preconditions necessary for rescue behavior focused on injured individuals to evolve across taxa's: a high value of individuals, a high injury risk and social interaction. Ultimately we argue that a similar problem, how to rescue injured group members, has led to different mechanisms to save injured individuals across different taxa
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