Production of sperm not only seems to lower one's immunity but is also a more biologically taxing process than previously thought. Damian Dowling of Monash University's chool of Biological Sciences and Leigh Simmons, professor at the University of Western Australia, have investigated the trade-off between sperm quality and immunity. "Males that invested heavily in their sperm paid the price of being more likely to succumb to a bacterial infection," said Dowling, the journal Public Library of Science ONE reports. "This study challenges the traditional view that sex, and sperm production, come cheaply to males," he added, according to a Monash University statement. "Here we show that the costs are in fact large, and these costs dictate how much effort a male will devote into any given sexual encounter," he added. Dowling said investigations into life history trade-offs -- investment in reproduction versus future reproduction and survival prospects -- have historically focused on females. Researchers used the Teleogryllus oceanicus Australian field cricket to prove that the production of quality sperm is expensive and males are strategic about investing energy in the biological process. The crickets were housed either with sexually immature females, sexually mature females incapable of reproduction, or sexually mature females capable of reproduction. Sperm quality was measured twice and immune function once during the experiment. Dowling said the male crickets were more likely to produce high quality sperm when housed with sexually mature females with whom they could mate, indicating a strategic investment of energy.