Reciprocal altruism, vampire bats, and relatedness
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Reciprocal altruism, vampire bats, and relatedness
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[post_date] => 2024-12-28 11:58:27
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[post_content] => Practice Passage (Question 1-5)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
Vampire bats (Desmodus rotundus) are social mammals, which naturally determine kinship differences, form dyadic relationships that remain consistent over time, and practice food sharing with roost-mates who were unable to feed. These dyadic relationships occur between both kin and non-kin. Vampire bats can die if unable to feed for more than 70 hours. Roost-mates may regurgitate food into the mouth of the unfed roost-mate.
An experiment was conducted on 20 vampire bats (11M, 9F) over a 2-year period to determine whether this food sharing behavior was altruistic. The bats were housed in a flight cage, large enough to allow the bats to freely associate, for more than 2 years before the beginning of the study. The bats were removed, fasted for 24 hours, re-introduced into the roost, and their social interactions were recorded for two hours after reintroduction. None of the bats tested showed signs of parasite infestation. Researchers examined food sharing (licking the roost-mate’s mouth for more than 5 seconds with > 5 seconds between bouts of licking) and subsequent allogrooming (licking locations other than the roost-mate’s mouth). The bat’s behavior was monitored to determine subsequent interactions. The coefficient of determination values for food donated, donor sex, allogrooming, and relatedness are shown in Figure 1. Sharing happened most often between females; males were not recorded sharing food with other males. Donors initiated food sharing more often than fasted bats and three donors, on average, fed each of the fasted bats. There was no relation found between recipient (age or size) and donations or allogrooming received. Some donors rejected certain begging (harassing) recipients; however, some fasted subjects rejected food sharing from certain perspective donors.
Figure 1: Relative variation in food donated; 38% of the variation in the amount of food donated can be explained by this model. Food donated (p < 0.0002), donor sex (p < 0.0002), and allogrooming (p < 0.0002) received were all significant; however, relatedness was not (p = 0.16).
[post_title] => Reciprocal altruism, vampire bats, and relatedness
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[question] => Which statement would support the hypothesis that reciprocal help is determined independent of kin discrimination?
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[description] => Reason for the Correct Answer:
It is not apparent in the passage that any of the donors were related.
While familiarity may have influenced the amount of food donated/received both donors and recipients were observed rejecting food sharing. Food sharing was not indiscriminate.
It is not apparent from the passage whether allogrooming between food recipients was also between family members.
Food previously received was much more predictive than relatedness.
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[each_answer] => A. Each fasted bat was fed by three donors.
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[each_answer] => B. Food previously received was much more predictive than relatedness.
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[each_answer] => C. Familiarity between dyads produced indiscriminate altruism.
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[each_answer] => D. Allogrooming received from food recipients was statistically significant.
)
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[1] => Array
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[quiz_unique_key] => 3873426850
[question] => How did the difference in sex effect the food sharing between dyads?
[value] => Array
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[answer] => 2
[description] => Reason for the Correct Answer:
Food sharing was recorded between males and females.
Food sharing was recorded between females and other females.
Food sharing was not recorded between males and other males.
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[0] => Array
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[each_answer] => A. Food sharing was not recorded between females and other females.
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[each_answer] => B. Food sharing was not recorded between males and other males.
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[each_answer] => C. Food sharing was only recorded between males and females.
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[each_answer] => D. Food sharing was not recorded between males and females.
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[quiz_unique_key] => 83407773
[question] => Which of these statements describes the influence of harassment on food sharing?
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[answer] => 1
[description] => Reason for the Correct Answer:
The donor, not the recipient, initiated most of the food sharing.
Donor size and age were not found to be related to either allogrooming received or food donations received.
The donor initiated most of the food sharing, which does not support harassment as an influence on food sharing.
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[each_answer] => A. The donor initiated most of the food sharing, which does not support harassment as an influence on food sharing.
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[each_answer] => B. Older recipients initiated sharing more often than donors initiated sharing, which supports harassment as an influence on food sharing.
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[each_answer] => C. The recipient initiated most of the food sharing, which does not support harassment as an influence on food sharing.
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[each_answer] => D. Recipients with larger forearms initiated sharing more often than comparably sized dyads, which supports harassment as an influence on food sharing.
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[3] => Array
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[quiz_unique_key] => 2261298308
[question] => Which conclusion describes the correlation of allogrooming and social bonding in vampire bats?
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[answer] => 2
[description] => Reason for the Correct Answer:
There was no correlation described in the results between allogrooming and food refusal.
Male-male dyads were not observed sharing food during this experiment.
None of the bats in the experiment were infested with parasites during the experiment.
Allogrooming was higher on non-test days between food-sharing dyads and was consistent throughout the experiment.
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[each_answer] => A. Some vampire bats refused food from certain perspective donors.
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[each_answer] => B. Allogrooming was higher on non-test days between food sharing dyads and was consistent throughout the experiment.
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[each_answer] => C. Allogrooming was highest between vampire bats infested with parasites and was consistent throughout the experiment.
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[each_answer] => D. Male-male dyads were observed performing allogrooming after sharing food.
)
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[4] => Array
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[quiz_unique_key] => 574431310
[question] => For actions to be described as strongly altruistic, the action must reduce the absolute fitness of the donor. Do the actions of the vampire bats, described by the researchers, fit this definition?
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[answer] => 4
[description] => Reason for the Correct Answer:
A reduction in absolute fitness decreases the total number of offspring or the donor’s lifetime reproductive success.
Although some begging individuals were rejected, it is not clear that the individual was not fed by another roost-mate.
No assertions were made about the offspring of the bats in this study.
Only 38% of the variation in the amount of food donated was explained by this model. This means that 62% of the variation was not described by the model shown in Figure 1.
It is not possible to tell if the donor’s absolute fitness was reduced. The model described so little of the variation in food donated.
)
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[each_answer] => A. No, in this experiment the donor’s absolute fitness was not reduced. Altruistic bats would be selected for.
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[each_answer] => B. Yes, in this experiment the donor’s absolute fitness was reduced. Some donors rejected certain begging individuals.
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[each_answer] => C. Only the male vampire bat’s absolute fitness was reduced. Males were not recorded sharing with other males.
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[each_answer] => D. It is not possible to tell if the donor’s absolute fitness was reduced. The model described so little of the variation in food donated.
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