The Boy Who Counted Butterflies
Data Collection & Citizen Science

The Boy Who Counted Butterflies

Data science starts with counting.

Data Collection & Citizen Science12-Month Curriculum 12h

The Story

The Butterfly Notebook

In a small village at the edge of Namdapha National Park in Arunachal Pradesh, a boy named Talo carried a notebook everywhere he went. It was not a school notebook — it was a butterfly notebook. Every page had a date, a place, and a drawing of a butterfly, coloured with the pencils his teacher had given him.

"Why do you count butterflies?" asked his sister, Yami, who thought bugs were boring.

"Because somebody should," said Talo.

That was the only reason he had, and it was enough.

The Forest of Wings

Namdapha is one of the wildest places in all of India. It stretches from the river valleys to the snow-capped peaks of the Patkai Range, and inside it live tigers, clouded leopards, red pandas, and more species of butterfly than almost anywhere on Earth.

Talo knew this because his father, a forest guard, had told him. "The scientists say there are over five hundred species of butterfly in Namdapha," his father said. "But no one has counted them all. The forest is too big, and the butterflies are too many."

Talo decided he would try.

Every morning before school, he walked the trail from his village to the river, noting every butterfly he saw. He drew the ones he didn't recognise — their wing patterns, their colours, the shape of their antennae. He gave them names until he could look them up: the blue flasher, the orange dot, the tiny white one that only comes out at noon.

The Pattern

After six months, Talo had filled three notebooks. He spread them on the floor of his house and looked at the numbers. Something strange jumped out.

In the part of the trail near the old-growth forest, where the trees were ancient and the canopy was thick, he had counted forty-two species. But near the part where loggers had cleared trees five years ago, he had counted only eleven.

"Baba," Talo said to his father, "why are there fewer butterflies where the trees were cut?"

His father sat down and looked at the notebooks carefully. "Because butterflies don't just need flowers," he said. "They need specific plants for their caterpillars. They need shade at certain times of day. They need moisture. They need the whole forest — not just a piece of it."

"So if the butterflies are gone," said Talo slowly, "it means the forest is sick?"

"Exactly," said his father. "Butterflies are like a thermometer for the forest. When you count butterflies, you are counting how healthy the whole ecosystem is."

The Scientist's Visit

That winter, a butterfly scientist from the Zoological Survey of India came to Namdapha. Talo's father introduced them. The scientist, Dr. Mitra, looked at Talo's notebooks and her eyes went wide.

"This boy has recorded species we haven't documented in this part of the park," she said. "And his data on population changes — this is exactly what we need. You've been doing real science, Talo."

Talo blushed. "I was just counting."

"Counting is science," said Dr. Mitra. "The most important science starts with someone paying attention."

The Butterfly Census

Dr. Mitra helped Talo organise the first Namdapha Butterfly Census — a day when children from villages across the park walked their trails, counted butterflies, and sent their numbers to a central tally. Thirty-seven children participated. Together, they counted two hundred and fourteen species in a single day.

The data showed what Talo's notebooks had already whispered: the forest was healthiest where it was oldest, and most fragile where it had been disturbed. The park authorities used the census to decide where to focus their conservation efforts.

Talo kept counting. He is still counting. His notebooks now fill an entire shelf, and every page is a tiny portrait of the forest's health, drawn in coloured pencil by a boy who believed that somebody should pay attention — and decided that somebody was him.

The end.

Try It Yourself

Choose your level. Everyone starts with the story — the code gets deeper as you go.

Story Progress

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Ready to Start Coding?

Here is a taste of what Level 1 looks like for this lesson:

Level 1: Explorer — Python
# Mark-recapture: estimate butterfly population!
marked_first_visit = 40    # M: butterflies marked
caught_second_visit = 50   # C: total caught in round 2
recaptured_marked = 8      # R: marked ones recaptured

# Lincoln-Petersen formula: N = (M * C) / R
estimated_population = (marked_first_visit * caught_second_visit) / recaptured_marked
print(f"Estimated population: {estimated_population:.0f} butterflies")

# How confident are we? 95% confidence interval
import math
se = estimated_population * math.sqrt((1/recaptured_marked) - (1/caught_second_visit))
print(f"95% CI: {estimated_population - 1.96*se:.0f} to {estimated_population + 1.96*se:.0f}")

This is just the first of 6 coding exercises in Level 1. By Level 4, you will build: Conduct a Butterfly Population Survey.

By Level 4, enrolled students build: Conduct a Butterfly Population Survey

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