Radiolab: "Blood Buddies" (December 28, 2010)

Overview of Episode's Main Theme

In "Blood Buddies," Radiolab hosts Jad Abumrad and Robert Krulwich dive into the mysteries of generosity and niceness in nature, focusing on a remarkable story of vampire bats who share their most precious resource—blood. The episode traces biologist Jerry Wilkinson's groundbreaking research showing that, for vampire bats, sharing food with non-relatives isn't just possible—it's critical to their survival, upending traditional ideas about animal altruism as purely gene-driven.

Key Discussion Points and Insights

Recap of the Previous Episode & Central Question

• The conversation opens with a playful exchange about sharing (00:00–00:30), setting the stage for an exploration of why animals help each other in what seems to be a cruel, competitive world.
• The hosts review how biologists often see "niceness" as disguised selfishness—helping kin is really helping one's own genes (00:50–01:22).

Introducing Jerry Wilkinson and His Bat Research

• Dr. Jerry Wilkinson, biologist at University of Maryland, shares how he stumbled upon this research during his first summer as a graduate student in Costa Rica in 1977 (01:28–01:50).
• He chose to study vampire bats due to their abundance on local cattle ranches (01:58–02:25).

Vampire Bat Behavior Observed in the Wild

• Wilkinson describes how vampire bats feed at night, returning home engorged on cow’s blood.
• Unexpectedly, he observes:
  • Highly social behaviors: grooming each other for up to 30% of their time (04:17–04:29).
  • Bats "hugging" and "kissing"—one bat licking inside another's mouth (05:01–05:21).
  • Discovery: adult bats regurgitating and feeding blood to other adult bats, not just their young (05:34–05:41).
    • Memorable quote: "And that was a shock...these were adult animals feeding other adult animals food that they could have been eating themselves." — Jerry Wilkinson (05:38)

Testing the Nature of Bat Generosity

• The expectation: such generosity should be limited to close relatives, consistent with gene-centric evolutionary theory (06:04–06:21).
• Wilkinson sets up an experiment with unrelated bats:
  • Starves one bat while others feed, returning the hungry bat to the group to observe whether it's fed by others (06:31–07:16).
  • Results: Non-relatives feed the starving bat by regurgitating blood, contradicting strict kin selection theory (07:24–08:01).
    • Wilkinson's reaction: "At that point, I was thrilled that I had found something that seemed to indicate that it wasn't just all about relatedness..." (07:30)

How Vampire Bat "Friendships" Work

• Further analysis uncovers a pattern: bats reciprocate favors—giving blood to those who have helped them before (08:32–09:15).
  • Jad Abumrad: "If I feed you, you feed me." (09:15)
• Wilkinson formalizes "friend numbers" based on data, finding that social bonds (friendships) are better predictors of sharing than genetic relatedness (09:33–10:01).
  • Memorable quote: "Buddies beat kin." — Robert Krulwich (10:12, echoing Wilkinson's findings)

Implications and Broader Impact

• The research challenged prevailing ideas, suggesting that chosen social bonds, not just genes, are powerful drivers of "niceness."
  • Robert Krulwich: "This is in effect an idea that niceness is really deeply chosen." (10:19)
• Despite early excitement, such reciprocal altruism among unrelated adults has not been widely documented in other species (11:28–12:15).
  • Wilkinson: "I don't think it's unique, but I don't think it's very common...vampire bats are really pretty special because of this reliance on blood." (12:15)

The Evolutionary Why: Survival Demands Sharing

• Theorizing on evolution, Wilkinson explains that mass extinctions of large mammals likely drove bats to develop sharing behaviors as an emergency survival strategy (12:26–13:29).
  • Wilkinson: "If they didn't help each other, I think you would find vampire bats gone." (13:19)
• The episode comes full circle: in extreme circumstances, generosity isn’t an optional virtue but a necessity for survival (13:34–13:57).
  • Jad Abumrad: "When the going gets tough, the tough get nice." (13:57)

Notable Quotes and Memorable Moments

• On the revolutionary aspect of bat generosity:
  • "I was thrilled that I had found something that seemed to indicate that it wasn't just all about relatedness..." — Jerry Wilkinson (07:30)
• On bats' friendship matrix:
  • "It turns out that number is the best predictor of who will feed whom. It's better than who's related to whom." — Jerry Wilkinson (09:54)
• On the evolutionary necessity of sharing:
  • "If they didn't help each other, I think you would find vampire bats gone." — Jerry Wilkinson (13:19)
• On altruism and survival:
  • "When the going gets tough, the tough get nice." — Jad Abumrad (13:57)

Timestamps for Key Segments

• Topic Introduction & Relevance of Sharing: 00:29–01:22
• Meet Jerry Wilkinson / Early Bat Research: 01:28–02:25
• Vampire Bat Social Behaviors Observed: 04:17–04:29
• First Observations of Food Sharing: 05:01–05:41
• Testing the Relatedness Hypothesis: 06:31–08:01
• Discovering Reciprocal Sharing / Bat Friendships: 08:13–10:01
• Comparison: Friends vs. Kin: 10:01–10:19
• Why Is This Rare? Evolutionary Perspective: 12:15–13:29
• Summary: Survival Drives Niceness: 13:34–13:57

Tone and Style

The conversation is lively, playful, and accessible, mixing scientific insight with humorous asides (like joking about being pooped on by bats or comparing the friendship matrix to "eighth grade"). Quotes are direct and capture the speakers' sense of surprise and curiosity. The episode weaves curiosity, wonder, and a bit of skepticism into the heart of scientific discovery.

Summary Conclusion

This episode of Radiolab uses the surprising generosity of vampire bats to question and expand our understanding of altruism. Wilkinson's research shows that social bonds—like friendships—can shape survival just as strongly as genetic ties. In the world of vampire bats, when life is on the line, sometimes kindness is more than a virtue—it's a strategic lifeline.