Does feeding competition influence tammar wallaby time allocation?

Animals may aggregate to reduce predation risk, but this potentially incurs the cost of increased competition. We studied the degree to which competition for food influenced the time tammar wallabies (Macropus eugenii) allocate to foraging and vigilance by experimentally manipulating access to food, while holding other factors constant. Groups of six wallabies were observed when they had access to either one or six non-depleting bins of supplemental food. Food availability had no effect on the time allocated to foraging, looking or affiliative interactions, and this was true whether individuals or groups were treated as the unit of analysis. However, wallabies engaged in substantially more aggressive acts in the high-competition treatment. These results, when combined with other findings, suggest that the moderately social tammar wallaby receives an antipredator benefit by aggregating with conspecifics which is not reduced significantly by foraging competition.