The advantages and disadvantages to group living are debatable and vary across the animal kingdom. Living in a group can result in increased disease transmission, increased vulnerability to predators and fast depletion of food resources. However living in a group can benefit many animals through social interactions, and there are also more individuals to watch out for predators (dilution results in there being a lower chance of any one individual being predated).
In my research project I found that the group of 5 sifaka individuals moved less, and had a smaller home range size than the group of 4 individuals. It is thought that this is because the group of 4 individuals was living in a depleted habitat subjected to far more disturbance than the habitat where the group of 5 individuals resided. So even though there was more of them, because their habitat was less disturbed, they didn’t need to move around as much as the group of 4. This demonstrates the importance of taking into account as many factors as possible when studying the behaviour of wild animals.
The benefits of group living are very apparent in the larval stages of many lepidopteran species (Despland and Le Huu, 2007). Caterpillars living in groups use pheromone marked silk trails to mark the routes between feeding and resting sites. By following these trails it is thought that the caterpillars purchase on leaves is enhanced, group cohesion is maintained and the individuals are directed by group communication to food resources. Forest tent caterpillars continuously spin silk behind them, marked with a non-volatile pheromone, which has been found to enable young caterpillars to reach food sources quicker. The groups are very close knit when the caterpillars are young but begin to disperse as the caterpillars mature, suggesting a decreased importance of group living with age. As caterpillars grow, group living can become costly due to competition for food and space.
Despland, E. Le Huu, A. 2007. Pros and cons of group living in the forest tent caterpillar: separating the roles of silk and of grouping. Entomologia Experimentalis et Applicata. 122(2). 181-189.