Diss. (sammanfattning) Skara : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Uppsatsen undersöker björnklor upptäckta i järnåldersgravar (ca 500 e.Kr. – 1100 e.Kr.) på Gotland, Sverige. Brunbjörnen har aldrig funnits som en del av i öns fauna, vilket innebär att varje björnklo som upptäcks är ett spår av ett forntida utbyte mellan ön i fråga och omgivande fastlandsområden. Tidigare forskning inom ämnet har mest bestått av sammanställningar av gravkontexter med björnklor. För att ytterligare tolka björnklorna och för att diskutera det möjliga syftet bakom deponeringar i gravar behöver emellertid klor knytas till tillhörande tassar. En vanlig förklaring är att björnklor härstammar från pälsverk. Teorin om päls fungerar dock inte för alla upptäckta klor. Därför syftar uppsatsen till att skapa en metrisk metod genom mätningar av referensmaterial av björnklor. Tanken är att mätmetoden ska användasför att undersöka och tolka arkeologiska fynd av björnklor. Tolkningen av klorna är en viktig del i förståelsen om hur djurresurser nyttjades under förhistorisk tid. / This paper examines bear claws discovered in Iron Age graves (c. 500 AD – 1100 AD) in Gotland, Sweden. The brown bear has never existed as a part in the island's fauna, meaning that every bear claw discovered is a trace of the ancient exchange between this island and the surrounding mainlands. Previous research on the subject has mostly consisted of compilations of the number of grave contexts with bear claws. However, to further interpret bear claws from each burial context and to discuss the possible purpose behind deposition in the grave, claws need to be assessed for associated paws. A common explanation is that bear claws derives from fur. However, the theory of fur does not work for all discovered claws. Therefore, the paper aims to create a metric method through measurements of reference material of bear claws. The idea is that the measurement method could be used to examineand interpret the archaeological bear claws. The interpretation of the claws is an important part of the understanding of how animal resources were used in prehistoric times.

The ability to grip on petal surfaces is of crucial importance for the interactions between bees and flowers. In this thesis, I explore the biomechanics of attachment and morphological diversity of bee attachment devices, linking this to the behavioural ecology of bee interactions with flowers. Attachment devices come in two main kinds: claws or spines, and adhesive pads. Claw functioning is poorly described, particularly in terms of how their performance depends on body size, claw geometry, and surface roughness. Claw attachment performance was investigated using several insect species, each covering a large range of body masses. Weight-specific attachment forces decreased with body size, with claw sharpness seemingly playing a role. In bees there is considerable interspecific variation in tarsal claw morphology. This variation, and arolia presence/absence, was categorised for the large bee family Apidae. Cleft/bifid claws were shown to be present in the majority of the Apidae, often with differences between sexes and clades. Using Bombus terrestris, there was no evidence that cleft claws are important for pollen collection; however, I found that the inner tooth of cleft claws can act as a backup if the main tooth breaks. Although this may be one function of cleft claws, there are clearly other unresolved functions well worth further exploration. Investigations were undertaken to explore how petal surface roughness affects bee foraging behaviour. Lab-based foraging trials on B. terrestris visiting artificial flowers varying in slope, surface texture and sugar reward revealed a trade-off between the biomechanical difficulty of visiting and handling the ‘flowers’ and the quality of the reward offered. Flowers that were difficult to grip were often avoided even if they offered a higher reward. To further investigate reward preferences of bees, the effect of sucrose concentration on honey stomach offloading times was also explored. Although the majority of petals do have a rough surface, some have slippery petals. In the field, bumblebees avoided landing on slippery hollyhock petals in favour of the easy-to-grip staminal column. In contrast, honey bees, which are smaller and have larger adhesive pads, landed on both the staminal column and the petals. Slippery petals may be an adaptation to increase contact with plant reproductive structures. Grip is also important to allow the honey bee parasite Varroa destructor to climb on to their host. Attachment forces experiments found that V. destructor could support > 300 times their body mass on honey bees, giving them strong attachment even when bees attempt to remove them through grooming. A grooming-based device for treating V. destructor was tested in an apiary trial. The device was ineffective, providing valuable information for beekeepers considering using this product. In summary, this thesis improves our understanding of the biomechanics of attachment as well as identifying several important aspects of grip in bee-plant interactions.