Lonza takes great care to not harm the crabs during the harvesting of their blood. During harvesting blood is collected by puncturing the septum on the underside of the animal with a small needle. The animal will only give as much blood as it can afford (about 25%) before it shuts off the blood supply. This ensures that the animal will not bleed to death. The horseshoe crab is then released back into the water in the vicinity of where it was caught. The mortality rate for the crab as a result of the process is less than 5%.