The ninja knew that the pupils of cats’ eyes shrink when there is light and expand when there is no light. They could easily tell the time by looking at the cats’ eyes. This was necessary if they had to hide indoors for a long time and if they needed to know exactly the middle of the day. The pupils of cats’ eyes shrink the most and become like a needle right around the noon.
Ninjas often faced watch dogs when they were on a mission. To distract them, they used the same kind opposite sex dogs. If they had a time to prepare for the mission, then they repeatedly gave the the dogs treats and got them familiarized with the smell of the ninja.
The ninja released rabbits or similar small animals in front of the target building they are trying to sneak in which would confuse and distract the guards.
Ninja used the feather of the crow to attach the arrows of the blowgun (Fukiya-dutsu). The ninja also observed the crows in the river. A swimming crow means it will rain.
Ninja often used poison by putting it on the sharp edges of the shuriken (ninja stars). They often extracted the poison from blowfish, commonly found in Japan.