# #76 どんぐりの戦略とあこがれの祭り話

- Show: 聞く図鑑
- Published: 2026-10-08
- Canonical: https://podc.club/en/episode/1813814072_3ba02c98f1b0.html
- Audio: https://anchor.fm/s/10407d7f8/podcast/play/126915113/https%3A%2F%2Fd3ctxlq1ktw2nl.cloudfront.net%2Fstaging%2F2026-9-6%2F900d0973-db55-cd42-3a9f-ea9f6de2bd72.mp3
- Source: Edited from a machine transcript of the first 30 minutes of the episode. Not an official summary.

Matsubara and Shoji (松原・翔二), editors at Gakken's Zukan LIVE imprint, break down the surprisingly complex world of acorns — 22 species, two distinct defense strategies, and a boom-bust reproductive cycle that manipulates predator populations. The second half of the episode shifts to autumn festivals, as Shoji shares what it was like growing up with Kishiwada's Danjiri Matsuri, then both hosts open up about festivals they have yet to experience.

## What this episode answers

### What kinds of acorns exist, and does the chestnut count as one?

Every nut produced by a beech-family (Fagaceae) tree is technically an acorn, so chestnuts are included; Japan has 22 species, with Konara and Mizunara being the archetypal image, though the chestnut's spiny husk is simply a cupule that has grown to enclose the entire fruit and sprouted dense spines.

### What shapes do the cupules (kakuto) come in, and what purpose do they serve?

The cupule is a protective structure whose form varies dramatically by species: Sudajii and beech use a physical-defense strategy in which the cupule fully encloses the fruit, while Konara and Mizunara use a chemical-defense strategy in which a small cupule is paired with tannin-rich flesh that acts as a poison against insects.

### Why do acorn-bearing trees alternate between bumper crops and poor harvests?

By producing few nuts in lean years to suppress predator populations — birds, squirrels, and the like — and then flooding the forest with nuts in a bumper year, the trees ensure that more fruit survives than animals can eat; the strategy is amplified because the acorn trees within a single forest synchronize their boom-bust cycles.

### What is Kishiwada's Danjiri Matsuri, and how do local children take part?

Held over two days around September 19–20, the festival centers on pulling large wooden floats (danjiri) through the streets; children participate by holding the ropes at the rear, walking all day until their legs are swollen, while the entire community — including local schools — is consumed by the event.

### What other autumn festivals did the two hosts discuss, and which ones are on their wish list?

Shoji spoke of his longing to see the Aoi Matsuri (葵祭) in Kyoto — a procession in Heian court dress with horses and ox-drawn carriages — which he missed due to the pandemic despite living in the city; Matsubara mentioned the Ieyasu Gyoretsu in his hometown of Okazaki, Aichi, featuring armored arquebusiers and yabusame; both said their top festival to visit someday is the Gujo Odori (郡上踊り) in Gujo Hachiman, Gifu, one of Japan's three great Bon dances, famous for its all-night dancing that runs until dawn.

## Article

## What Is an Acorn? 22 Species in Surprising Variety

The word "acorn" in Japanese (donguri) is a collective term for the fruit of any tree in the beech family (Fagaceae). Pages 168–169 of Gakken's Zukan LIVE Plants volume display all 22 species found in Japan, shown at actual size. Konara and Mizunara fit the classic mental image, but the chestnut is technically a beech-family fruit too — and therefore an acorn. The chestnut's spiny husk is simply a cupule (kakuto, 殻斗) that has expanded to enclose the entire fruit and grown a dense coat of sharp spines. Kunugi has a rounded, spherical nut fitted with a cupule covered in curling, worm-like spines, and Abemaki sports a similarly sea-urchin-shaped cupule. Sudajii and beech have cupules that wrap the nut completely; when ripe, the cupule splits open with a sharp crack and the nut falls out. The acorn Totoro carries in My Neighbor Totoro most closely resembles Konara, which is slightly elongated.

## The Cupule's Role: Physical Defense vs. Chemical Defense

The cupule's primary job is to protect the developing nut from predators. Weevils, for example, use their long, slender rostrums to bore into acorns and consume the interior. If you find a fallen acorn with a small hole in it, something has already been inside — so when collecting acorns, choose only ones with no holes.

Defense strategies fall into two broad categories. Species like Sudajii and beech rely on **physical defense**: the cupule encases the nut completely, making it mechanically difficult to breach. Species like Konara and Mizunara instead rely on **chemical defense**: the cupule is small, but the nut itself is packed with tannins — the compounds responsible for astringency — which function as a toxin against small insects even if humans experience them merely as bitterness. Jomon-era people who ate acorns had to soak them in water for long periods to leach out the tannins, and today's workshops on making ancient-style acorn bread still require thorough tannin removal as the first step.

## The Boom-Bust Strategy: Manipulating Predators Through Timing

Acorn trees do not produce a steady annual yield. Instead, they cycle between abundant years and near-barren ones. The prevailing explanation is that lean years starve predator populations — birds, squirrels, and other animals that depend on acorns — keeping their numbers low, so that when a bumper year arrives, the sheer volume of nuts produced far exceeds what the reduced predator population can consume. Any nuts left uneaten have a chance to germinate and become the next generation. A steady annual supply, by contrast, would allow predators to grow in proportion to the yield, leaving little surplus. What makes this even more striking is that acorn trees within the same forest synchronize their boom-bust cycles, amplifying the effect. Matsubara compared it to the kind of revenue management strategy a restaurant chain might use.

## Kishiwada's Danjiri Matsuri: Growing Up Inside the Festival

Shoji grew up in Kishiwada, Osaka, and spent his childhood immersed in the Danjiri Matsuri (だんじり祭り), held over two days around September 19–20 each year. Danjiri are large wooden floats fitted with ropes at the front and rear; teams haul them at a run through the city streets. Children hold the rear ropes and walk the route — not sprinting with the adults, but still covering enough ground to leave their legs thoroughly exhausted by day's end. Throughout the festival period, the neighborhood smells of Aire Salon Pas muscle spray. Practice calls echo through the streets late at night, and local schools effectively release students early during the festival days, so thoroughly does the event consume the entire community.

Shoji's uncle served as a daiku-kata (大工方) — one of the performers who dances on top of the float — providing an up-close model of cool that young Shoji admired. After the festival, crab season begins and the local table fills with watarigani (migratory swimming crabs).

The crowd favorite spectacle is the yari-mawashi (やり回し): a nearly four-ton float taken through an S-curve at full speed, close enough to graze the walls of houses lining the street. Children used to imitate the move with school carts in hallway corners, and Shoji recalled how normally relaxed neighborhood older brothers became electrifyingly cool in their hachimaki headbands — an image that hooked every kid in the area.

## Dream Festivals: Aoi Matsuri, the Ieyasu Procession, and Gujo Odori

Shoji lived in Kyoto during graduate school but was unable to see the Aoi Matsuri (葵祭) because of the pandemic. Organized by Shimogamo and Kamigamo Shrines, the festival is a procession of hundreds of participants in full Heian court dress, accompanied by horses and ox-drawn carriages. He did occasionally spot a costumed figure or a horse moving through the city streets, which only deepened his desire to see the full event.

Matsubara's hometown of Okazaki in Aichi Prefecture hosts the Ieyasu Gyoretsu (家康行列), a parade commemorating Tokugawa Ieyasu that features armored arquebusiers and yabusame horseback archery. The festival both hosts said they most want to attend is the Gujo Odori (郡上踊り) in Gujo Hachiman, Gifu Prefecture — one of Japan's three great Bon dances, renowned for its tetsuyaodori, an all-night dance session that continues until dawn with the whole town joining in.

## Takeaways

- Acorn is a collective name for all beech-family fruits, encompassing 22 Japanese species including the chestnut, each with a cupule adapted for either physical or chemical defense against predators.
- Acorn trees cyclically manipulate predator populations through synchronized boom-bust harvests, flooding the forest with surplus nuts in bumper years to guarantee that some survive to germinate.
- Shoji's firsthand account of Kishiwada's Danjiri Matsuri — from childhood rope-pulling to admiring his uncle atop the float — illustrates how a festival can define an entire community's rhythm and identity.