In a 20 km² forest fragment, a survey recorded 200 individuals of the Sundarbans mangrove frog. Of these, 25% are subadults and 15% are recent immigrants. The average reproductive output per adult per year is 3 eggs, and the survival rate from egg to adult is 35%. Estimate the net increase in the adult population per year.

Step-by-step solution

1. Calculate number of subadults: $200\times 0.25=50$.
2. Calculate number of immigrants: $200\times 0.15=30$.
3. Determine adult population: $200-50-30=120$.
4. Compute eggs laid by adults: $120\times 3=360$ eggs.
5. Find surviving adults: $360\times 0.35=126$ new adults.
6. Estimate net increase: $126-120=6$ adults per year.

Concept tested: Population growth estimation

Published 23 September 2026 · How this solution was prepared and checked