intake than females in groups of smaller sizes. The reduction in energy gain seen in females of the larger group also then negatively affected the development rates of any infant offspring. Therefore, despite the benefits of animals forming groups that increases foraging efficiency due to the presence of social information, large groups of animals may also incur a cost of having to compete for the resources available in the environment. Reproduction Another cost to group living is the effect that a larger group size has on the reproductive success of individuals. While forming groups may benefit the reproductive success of individuals as there are more potential mates, consequentially individuals may also have increased competition between one another to successfully find a mate and reproduce. This means some individuals will have a reduction in their reproductive success as it now competes with other group members. An example can be seen in a study conducted on the Eurasian badger (Meles meles). This study showed that females belonging to a large group of badgers had a higher failure rate of reproduction in comparison to badgers living in solitary. Therefore, some individuals may actually show reduced reproductive success while living in a group despite the increased presence of potential mates. Stress It is clear that animals that form groups need to maintain a group size around an optimal level. Individual group members in group sizes much larger or smaller than the optimum may have increased stress levels. Individuals in groups much larger than their optimum group size may have increased stress levels due to competition for food resources or mates. In contrast, individuals in groups smaller than their optimum have increased stress levels arising from inadequate defense from predators. An example of this can be seen in a study conducted on a species of ring-tailed lemurs (Lemur catta). This study predicted that the optimum group size of ring-tailed lemurs is 10-20 individuals. The study then showed that groups within the optimum group size produced the lowest level of cortisol (an indicator of stress), while groups larger or smaller than the optimum group size had a significant increase in cortisol production. Therefore, group sizes that are not maintained within their optimum size may incur a cost of increased stress levels of individuals within those groups. Inbreeding Another proposed cost of group living is the increased risk of inbreeding. As members of the group in close