Unit 5 Day 4 - Kin Selection & Altruism (Eusocial Mammals) Flashcards
when subordinates don’t breed
- more likely to help and increase fitness of dominant and her offspring
assumptions of theoretical models
- females compete over resources to breed
- dominants benefit from subordinates not breeding
- controlling reproductive output decreases energy = costly
reproductive skew
breeding is isolated to a certain group of dominant females –> dominant produces significantly more than others
eusocial
dominate female reproduces and non reproductive individuals cooperate in caring for young
What are the two assumptions of theoretical models that attempt to explain reproductive bias that is presented in the first two paragraphs of the introduction?
- group-living females compete over the resources required to breed, and that dominants benefit from the reproductive inactivity of subordinates
- in attempting to exert control over the distribution of reproduction is itself costly, reducing the total reproductive output
What is the evidence the author collected to support these two assumptions?
-negative effects of subordinate reproduction on dominants is limited to observations that subordinate breeding is sometimes associated with reduction in aspects of dominant female reproductive success
-the cost of attempting to alter the distribution of reproduction by interfering with the reproduction of other individuals is restricted to a few observations of declines in the quality of offspring subsequently produced by dominants, the quality of care they receive or their probability of survival
Where is the study site and study population?
-Kuruman River Reserve, South Africa
-Wild, habituated Meerkats
What life history and behavioural data did they collect?
-Dominant individuals were identified by their behaviour towards other group members
-Subordinates responded to dominance assertions by adapting a submissive posture
Bell Experiment
-Six treated groups, all subordinate females were injected with a hormone contraceptive
-Six control groups, all subordinate female were injected with a saline solution
Did dominant females treat subordinates differently in control vs treated groups?
-Dominant females attacked treated subordinates at lower rates
-Dominant was more tolerant of the presence of treated subordinate female
- Treated females were less likely to be interrupted by the dominant female during a foraging bout
Did the probability of evicted subordinates differ in control vs treated groups?
-Treated females were less likely to be evicted by the dominant female
-Closer in the size to dominant and older subordinates were more likely to be evicted
-Dominants targeted those most likely to attempt to breed themselves
Was there a difference in the number of females provisioning pups in control vs treated groups?
-Treated groups increase their helping effort both b/c they were unable to invest in their own reproduction
-Provisioning rates declined in Control Groups when females were themselves pregant
What are the beneficial effects of less aggression on dominant females and their pups?
-Subordinate females in treated groups provided more food
-Pups in treated groups started life heavier, but were also in groups with more helpers, many of whom were feeding at higher rates
Why do the authors expect dominants in cooperatively breeding species to develop low cost mechanisms for restricting subordinate reproduction?
Rather than direct attacks, dominants may simply reduce opportunities for subordinate reproduction, for instance by denying access to unrelated members of the opposite sex
Why do banded mongooses, which are a closely related social mongoose to meerkats, often have multiple females breeding together?
-They are one of the few cooperative vertebrates where multiple females commonly breed together: direct competition between pups is limited b/c pups are cared for by a single helper who does not provision other pups
