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Factors Affecting Reproductive Investment by a Burying Beetle (Nicrophorus Orbicollis)

Bayley, Kristen Nicole
Reproductive investment is an important activity in an animal�s life. Organisms must balance multiple tradeoffs in a way that maximizes their lifetime reproductive fitness. This often leads to a conflict of interest between the strategies of males and females attempting to optimize their own success. Burying beetles are unique among insects in that both the male and female participate in extensive parental care. Because they rely on vertebrate carcasses to breed, the nutritional quality of the resource is especially influential. To investigate if the beetles would adjust their reproductive strategies when the resource was manipulated, beetle pairs were provided carcasses that spanned a wide range of nutritional quality. The protein and fat contents of carcasses were measured using a dual energy x-ray absorptiometry (DXA) machine. I found the resource to be extremely influential in all aspects of investment. Both parents stayed with the brood longer when breeding on higher quality resources compared to lower quality resources. The total mass of the resource was the most important variable determining how long the male stayed. The female residence time depended on the protein content of the mouse as well as the interaction of the fat content with the quality of the male she was paired with, but not her own condition. The condition of the male had a large effect on whether any larvae were produced or not. More larvae were produced when carcasses had more fat and parents were in better condition. Burying beetles have the ability to adjust their investment according to the benefits received from reproduction. The fact that the resource plays a large role in determining reproductive strategies has ecological implications for the lifetime fitness of burying beetles. Future research should also include data on both males and females since that can be an important dynamic in burying beetle reproduction.