Special reading - counter intuitive behaviour -1 - supressing subordinates in meerkats

Question 1

who wrote the paper?

Answer 1

Bell et al (2014)

Question 2

what are the hypotheses?

Answer 2

when dominant females successfully supress subordinate reproduction fitness of the dominants offspring increases

Question 3

what is the aim of the paper?

Answer 3

to understand the evolutionary paradox of eusociality by explaining the benefits of extreme reproductive inequality within stable societies - paper hopes to understand the fitness benefits to dominant meerkats when they supress subordinates

Question 4

how did the experiment simulate subordinate suppression?

Answer 4

• used contraceptive injections to prevent subordinate reproduction in a long term study
• in year 1 in six treated groups all subordinate females over 180 days old were injected (n=35)
• in 6 control groups all subordinate females (n=38) were injected with an equivalent volume of saline solution
• in year 2 - control and treatment groups were swapped and protocol repeated

Question 5

how did they measure benefits to dominant from supressed subordinate reproduction?

Answer 5

• individuals were tagged for identification- meerkats were trained to step on scales and weight was measured throughout experiment (twice a week)

Question 6

how did they observe the meerkats throughout the experiment?

Answer 6

visited the group twice per week: collected behavioural data, recorded group composition and weighted meerkats
- every week focal watches were done on dominant females to monitor aggression towards subordinates

Question 7

in treated groups what were the results for how the behaviour of the dominants changed?

Answer 7

aggression towards subordinates decreased

dominants more tolerant of treated subordinates and less likely to evict them

Question 8

what changed in the treated groups?

Answer 8

• Ratios of helper to pups increased in treated groups (less subordinate females were evicted + less kids born)
• Dominant females in treated groups captured more food per minute
• Pups born to dominant females in treated groups were heavier when they first emerged from burrows +grew faster

Question 9

Meaning of results

Answer 9

• results prove that dominants are selected to suppress subordinate breeding because it reduces dominant fitness
• subordinates represent a resource, which is depleted when they attempt to breed
• Results also indicate the cost of subordinate repression behaviour for dominant females
• this is shown by dominants increased foraging success, gestational weight gain and pup emergence weight in treated groups.