UPSC Prelims 2021 Q23: Environment & Ecology – Ecosystems & Ecology Concepts
- (a) 1 and 2
- (b) 2 only
- (c) 3 only
- (d) 1 and 3
Answer: (d) 1 and 3
Explanation
Animals that Roll Up for Defence
| Animal | Defence Mechanism | Rolls Up? |
|---|---|---|
| 1. Hedgehog | Rolls into a ball, exposing sharp spines outward | YES |
| 2. Marmot | Alarm calls, running to burrow | NO - Does not roll up. |
| 3. Pangolin | Rolls into a ball, exposing hard keratin scales | YES |
Hedgehog (1) and Pangolin (3) both roll into balls for defence. Answer: (d).
Additional roll-up examples: Armadillo (three-banded armadillo), pill bug/woodlouse, and hoglets. Marmots are burrow-dwelling rodents that use alarm calls, not rolling.
Answer: (d) 1 and 3.
Why each option is right or wrong
- (a) Incorrect. Marmots do NOT roll up - they use burrows and alarm whistles.
- (b) Incorrect. Marmots do not roll up.
- (c) Incorrect. Hedgehogs also roll up - it is their signature defence.
- (d) CORRECT. Hedgehog (rolls into ball exposing spines) and Pangolin (rolls into ball exposing keratin scales) both use rolling as defence. Marmots do not.
Key point
Roll-up defence: Hedgehog (spines) + Pangolin (keratin scales). Also Armadillo (three-banded) and Pill bug. Marmot uses burrows and alarm calls, NOT rolling. Answer: 1 and 3.
Remember
Hedgehogs (spines) and Pangolins (keratin scales) roll into balls to protect vulnerable parts from predators. Marmots use burrows and alarm calls but do not roll. Answer: (d) 1 and 3.
Common mistakes
- Confusing pangolins with anteaters. Both eat ants, but pangolins have scales and roll up; anteaters do not.
- Not knowing marmots are ground squirrels of the Himalayas and Alps - they retreat to burrows, not roll.
- Assuming all small mammals roll up. Very few do - it requires specialised skeletal and muscular structure.
Exam tip
Pangolins are the most trafficked mammals in the world - all 8 species are threatened. India has Indian Pangolin (Schedule I, Wildlife Protection Act) and Chinese Pangolin (both traded illegally for scales in TCM).
Sources
- IUCN Red List - Pangolin Species Assessment
- Wildlife Institute of India - Indian Pangolin Studies