What evidence did Chapman and Chapman (2000) use to conclude that competition limits group size in the primates they studied?
-They found a positive correlation between group size and the density of food trees
-They observed a decline in group size with natural decline in food availability
-They observed an increase in group size with the experimental addition of food
-They observed an increase in fitness of individuals with a decline in group size
-They observed an increase in group size with an experimental reduction in competitors