The yukkuris residing on the southern islands have outer skin similar to tires and are extremely resilient. It is strong against physical blows, and it will rarely break. However, its movements are extremely slow and it has no attack capability to speak of. It is difficult and painful to try to abuse these types of yukkuris.* Also, the skin forms during the baby-yukkuri and koyukkuri stage, so all of them possess this resistance.
*Not sure about this part. It's either hard to abuse the yukkuri or you abuse the yukkuri long and hard. /shrug.
The yukkuris residing on the southern islands have outer skin similar to tires and are extremely resilient. It is strong against physical blows, and it will rarely break. However, its movements are extremely slow and it has no attack capability to speak of. It is difficult and painful to try to abuse these types of yukkuris.* Also, the skin forms during the baby-yukkuri and koyukkuri stage, so all of them possess this resistance.
*See comments