1. Touch: Pricking the hydra with a needle causes the body to contract. Leaves, aquatic plants, objects, etc. are stuck by hydra treads.
2. Hunger: A hungry hydra contracts and expands its muscles. Moves the body at a very fast speed to search for food. If they are not hungry, they slow down.
3. Temperature: Hydra always prefers cool water with a temperature of 20 degrees Celsius. When the surface temperature of the reservoir rises, the hydra slowly moves down. Dr. Siddiq Publications
4. Light: Hydra does not like either too much light or darkness. Always like moderate light. Dr. Siddiq Publications
5. Current: A continuous current causes the hydride body to bend towards the anode. Later, the whole body contracts. Dr. Siddiq Publications