Reading 2.1 Bell Meerkats Flashcards

1
Q

What hypotheses were tested in Bell’s study

A
  • To quantify the effect of subordinate reproduction on dominant behaviour and reproductive success
  • To assess the consequences of experimentally preventing subordinate breeding in 12 groups of wild meerkats
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2
Q

Study assumption 1

A
  • Group-living females compete over the resources required to breed, and that dominants benefit from the reproductive inactivity of subordinates
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3
Q

Study assumption 2

A
  • The tug of war model -attempting to exert control over the distribution of reproduction is itself costly, reducing the total reproductive output
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4
Q

Some methods to the study

A
  • Each meerkat group visited at least 2 days per week
    • Subordinate meerkats were injected with contraceptive hormone depo-provera)
    • Control received saline solution
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5
Q

Results of dominant attacking subordinates

A
  • Dominant females attacked treated subordinates at lower rates P= 0.003
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6
Q

Results of tolerance of treated subordinates

A

Dominants were more tolerant of treated subordinates presence (2m) P = 0.005

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7
Q

Interruption of foraging by dominant females

A
  • Treated females were less likely to be interrupted by the dominant female during a foraging bout p<0.001
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8
Q

Reduction in aggression and subordinate aggression

A
  • Treated females less likely to be evicted by the dominant female during her gestation p=0.004
    • Larger and older subordinates were more likely to be evicted p=0.029
    • Dominants target those most likely to attempt to breed themselves https://www.journals.uchicago.edu/doi/full/10.1086/656492#
    • No change in vigilance behaviour
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9
Q

The helper: pup ratio

A
  • Greater in treated groups
    • Positive effect on future pup development
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10
Q

Dominant female weight gain and pup emergence weight

A
  • More weight gain in pregnancy due to more efficient foraging and reduced effort in eviting subordinates
    • Subordinate pups would detract from the milk available to dominant pups
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11
Q

Subordinate female helping effort

A
  • Provided more food
    • Provisioning rates declined in control groups when dominant and submissive females were pregnant
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12
Q

Dominant pup growth rate

A
  • Grew faster between emergence and 95 days
    • This increases survival and size, which affects dominance, and reproductive success
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13
Q

What does the study add to animal behaviour in general?

A
  • Our results also suggest why plural breeding is rare in cooperative vertebrates
    • dominants are only likely to tolerate subordinate reproduction when it has little effect on dominant reproductive success, which is only likely where social structure limits direct competition between offspring.
    • This may explain why banded mongooses, a closely related social mongoose, are one of the few cooperative vertebrates where multiple females commonly breed together13: direct competition between pups is limited because pups are cared for by a single helper who does not provision other pups30. (Bell 2007)
    • Helps explain the evolution of singular breeding in vertebrate societies
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14
Q

1 weakness/ issue with the study

A
  • Evidence for negative effects of subordinate reproduction on dominants is limited to observations that subordinate breeding is sometimes associated with reductions in aspects of dominant female reproductive success, including care received by offspring18, offspring weight at independence15 and offspring survival13,16,19. It is unclear that this is causal, and may be due to age or condition related declines in dominant condition or capacity to prevent subordinate breeding.
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15
Q

a second weakness/ issue with the study

A
  • Evidence for 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 survival20,21. Again, it is difficult to rule out correlations with other social or ecological variables (food availability in particular).
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