Bonus: Wild Animal Dads from Terrestrials
This Radiolab/Terrestrials bonus episode explores remarkable animal fathers across species—from owl monkeys to seahorses, poison dart frogs, burying beetles, and stickleback fish—to challenge stereotypes about what fatherhood looks like in nature. Human dad Michael reflects on how his assumption that chimp-like absence was 'natural' for fathers was overturned by learning about these diverse parenting examples. The episode ultimately argues that nurturing, caregiving fatherhood is deeply ancient and biologically ingrained across the animal kingdom.
Summary
The episode opens as a Father's Day special drop from Radiolab's Terrestrials podcast, hosted by Lulu Miller, featuring biological anthropologist Dr. Eduardo Fernandez-Duque and human dad Michael as guides through the world of animal fatherhood.
The central story begins with owl monkeys in Argentina, where Dr. Eduardo's team made the unprecedented observation of a wild owl monkey birth. The father was present at the birth and appeared to assist with the umbilical cord. After a brief nursing period, the baby transfers almost exclusively to the father's back for a three-month piggyback ride through the forest canopy, during which the dad grooms the infant, teaches camouflage sleeping techniques, and instructs on foraging. Research suggests the infant ultimately forms a stronger attachment to the father than the mother.
Michael's personal story is woven throughout: growing up, he was told humans should compare themselves to chimps, whose dads were understood as aggressive or absent. This led him to believe the 'softer' side of parenting wasn't natural for dads. After a chance conversation with Dr. Eduardo during a swim playdate, he began questioning who chose chimps as the comparison species, and embarked on researching other animal dads.
The episode then tours six additional animal dads: Seahorse dads carry eggs in an abdominal pouch that regulates oxygen and salt, gestate the young, and go into labor themselves. Poison dart frog dads guard eggs, then carry each individual tadpole on their back to separate small water-filled plants, returning repeatedly to check water levels and singing to attract females to lay feed-eggs for the tadpoles. Darwin frog dads swallow eggs and incubate them in a vocal sac in their throat, with the fully-formed froglets eventually walking out of dad's mouth. Burying beetle dads team up with a mom to bury and shape a small animal carcass into an antimicrobial nursery (using secretions from both mouth and rear), then chew-feed the larvae from the carcass walls, and sometimes raise the entire brood solo if the mother leaves. Jacana bird dads are selected by competing females for their caregiving quality, with dads solely incubating and protecting eggs while mothers don't incubate. Stickleback fish dads build architecturally complex nests from plant material glued with protein-based mucus, perform zigzag courtship dances, and raise the eggs alone after the female deposits them.
The episode also revisits chimp dads, noting recent research showing they are not uniformly aggressive or absent—some groom, cuddle, and even adopt unrelated babies—suggesting individual variation that mirrors human fatherhood diversity.
A neuroscience angle is introduced: studies show that when fathers interact with babies, activity lights up in evolutionarily ancient brain regions. Researcher Kumi Kuroda's work suggests the very first parental nesting behavior appeared in male fish millions of years ago, predating mammals entirely. This leads to the conclusion that caregiving fatherhood is not modern or unnatural—it is one of the oldest biological drives on Earth.
The episode closes with a listener Q&A with Dr. Eduardo about owl monkeys, a moon-reading experiment testing human night vision, and a musical tribute to dads. Staff credits and support acknowledgments are included throughout.
About this episode
Father nature.
Key Insights
- Dr. Eduardo's team made the first-ever recorded observation of an owl monkey birth in the wild, revealing that the father was present and physically engaged, possibly helping sever the umbilical cord.
- Owl monkey infants spend approximately three months riding exclusively on the father's back and research suggests they ultimately form a stronger attachment bond to the father than to the mother.
- Michael argues that the widespread cultural narrative comparing human dads to chimp dads—who were understood as absent or aggressive—shaped his belief that nurturing behavior was unnatural for fathers, and he questions who made that comparison and why.
- Researcher Kumi Kuroda's work suggests that the very first parental nesting behavior in vertebrate evolution appeared in male fish, predating the emergence of mammals, implying that caregiving fatherhood is one of the most ancient biological drives.
- Burying beetle dads construct an antimicrobial nursery from a small animal carcass using secretions from their mouths and rear ends, and will raise broods of 10–30 larvae entirely alone if the mother abandons the family.
- Darwin frog fathers incubate eggs inside a vocal sac in their throat, suppressing their own calls to avoid drawing predator attention, with fully-formed froglets eventually emerging by walking out of the father's mouth.
- Jacana bird mothers compete aggressively with each other to secure a high-quality male partner, after which the father alone incubates and protects the eggs while the mother does not participate in incubation at all.
- Neuroscience studies of human fathers interacting with infants show activation in evolutionarily ancient brain regions, suggesting caregiving responses in dads draw on deep, primitive neural architecture rather than purely learned or cultural behavior.
Topics
Transcript
Radio Lab is supported by Viking, committed to exploring the world in comfort, offering destination-focused small ship experiences on all seven continents with programs designed for cultural enrichment and a shore excursion included in every port. And every Viking voyage is all-inclusive with no children and no casinos. More at Viking.com. Radio Lab is supported by USA for UNHCR, the UN Refugee Agency. Thank you. emergency relief to displaced families in more than 120 countries worldwide. For more information, visit unrefugees.org slash Radiolab. And this is a moment unlike any other. Nearly a year ago, Congress eliminated our federal funding, and so many of you stepped up to support Radiolab at that time. Thank you. Thank you from the bottom…
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