Question

Suppose you are a graduate student studying primate sociality (the area that examines reasons why primates live in groups). You observed a group of howler monkeys in northern Argentina to determine whether competition over resources or predation avoidance is the primary factor favoring group living. (a) First, describe both the Resource Defense Model and the Predation Avoidance Model. (b) One piece of data you obtained was that larger howler groups had larger territories. If the howlers formed groups for resource defense, what would be the expected relationship between group size and territory size? [Your answer to this question should include something like, "As groups size increases, territory size is expected to (increase, decrease, stay the same."] Explain how this data supports the Resource Defense Model. (c) Another piece of data you obtained was that predation rates were the same regardless if howlers lived in large or in small groups. If howlers formed groups to avoid getting eaten, what would be the expected relationship between group size and predation rates? Explain why this data contradicts the Predation Avoidance Model. [Your answer to this question should include something like, "As groups size increases, predation rate is expected to (increase, decrease, stay the same."]

Answer 1

Answer a:-

1. Resource Defense Model:-
   1. This can be explained in terms of defense, aggressiveness and density of species.
   2. When the density of animals foraging for a part or resource of any food resource increases, there is increase in the aggressiveness that is associated with depending the resource or the foraging part to derived the nourishment.
   3. When the density is low, there is less aggressiveness seen as compared to that of the point mentioned above. In other words, there is no intraspecies interaction which in turn allows equal attribution to consuming the resource however when the density increases, there is increase in rate of conflicts within the members of the species. This would result in the origin group finder to show the aggressiveness nature in order to trace and remove the other members away from the resource.
   4. In case when there is a different species member foraging for the resource, this would in turn show much variations in competition which would affect the benefits associated with defending the resource.
2. Predation Avoidance Model:-
   1. ​​​​​​​This Model or theory basically defines a particular strategy applied either in the form of group or as an individual to prevent themselves from potent predation.
   2. ​​​​​​​Larger the group size in most of the cases provides more protection due to decrease in time associated with vigilance or guarding the group. This can be stated as a benefit in terms of presence of group members who are better at spotting locations occupied by predators and at the same time this social grouping may also decrease the rate of associated predation. Living in group but presence of small number may increase the chances of successfully predation.