module 5_ discussion worksheet (ANTH 173)

Module 5: Discussion Worksheet ANTH 173: Mating Systems and Reproductive Success Worksheet: Polygyny Savannah baboons live in multi-male, multifemale polygynous groups. Male-male competition is very strong and there is a clear dominance hierarchy with high ranking makes getting, usually, the best of everything. Now look at this data on the mating success of the males. It is shown in both a figure and in data from in the table below. The males are shown in order of their dominance rank (ability to win fights) with 1 being the highest rank and 5 being the lowest ranking male. For 4 year period and 27 offspring were born so we can calculate: Male Rank 1 2 3 4 5 Average Percentage 85.2 7.4 0 0 7.4 20% Number Offspring 23 2 0 0 2 5.4 Number Offspring Per Year 5.8 0.5 0 0 0.5 1 1. What information can you see about the ability of different males to father offspring? The dominant Male 1 has the highest reproductive success as it invests in the most related to the amount of offspring he has produced and impacts the future generation. For Male 2, who shares the same amount of offspring as Male 5, his dominance, mating behavior during the fertile periods, and paternity inclusion is higher than the rest, but it yields very little offspring. These results tell us that because of Male 1’s reproductive success is at a high variance which is why some of the males are producing some and others do not produce at all. The reproductive results of both Males 2 and 5 may be from the availability of fertile females of the males could have been a victim of female choice because of the male to male competitions. 2. What do you think male 5 is doing that makes him more successful than some higher-ranking males? In a multi-male polygyny group, we can see multiple types of mating systems within the groups that can be an alternative to the norm. These groups can have females that defend food patches and defend against other female groups while the dominant males are defending the female groups. This results in the less dominant males to stay in the group and reproduce behind the dominant males. I think this is what makes Male 5 more successful compared to Male 3 and Male 4. Now look at the following data for Xavante, an indigenous people of eastern Mato Grosso state in Brazil. This figure and table show the same information on how many men and women had that number of children, the average number of children for men and women (which is the same) and the variance in the number of children. Xavante society allows polygyny. The variance measures how variable the data is, with a higher value meaning that there is a lot of variation in the number of children whereas a low value means that individuals have nearer the same number of children. # of Children 0 1 2 3 4 5 7 8 9 11 23 Average Variance # of Women 1 7 7 7 7 7 3 1 0 0 0 3.6 3.9