● Failures in 2012 and Steps to Success in 2013 ●
Emperor penguins hold their eggs and raise their chicks on unstable legs. As a result, the rate of egg-raising is not as high as that of nesting penguins, due to the risk of eggs breaking and chicks being crushed. In order to ensure the successful rearing of chicks, the six chicks born between 2004 and 2011 have all been raised artificially (i.e., by humans acting as parents). Although we have established the "artificial rearing technique," we have also observed "imprinting on humans (the phenomenon of remembering the first moving object as the parent after birth).
　We decided to try "natural brood rearing" (letting the parent birds raise the chicks) in 2012.
　In 2012, we artificially raised chicks for the first 10 days after hatching, and then returned them to their parents. However, after 24 hours of observation, we could not confirm feeding from the parent birds, so we gave up natural rearing and switched back to artificial rearing. The reason for the lack of feeding from the parents was thought to be that the chicks were less demanding of food from the parents because they had been imprinted by humans during the initial artificial brood rearing.

　In 2013, we decided to make two improvements: to acclimate the parent birds to the space for raising chicks as quickly as possible and to prevent the chicks from imprinting on people. To prevent imprinting on humans, we decided to wear penguin-shaped hats and gloves when artificially raising chicks and to feed the chicks while playing the parent birds' calls.

We have been observing the chicks for 48 hours, but they were not feeding from the parents. After 48 hours of observation, the chicks were still not feeding from the parent birds. Twenty-one days after hatching, the chick weighed 773g and was returned to the parent birds again, but still no feeding was observed. However, the chicks were requesting more food from the parent birds than before, so we decided to monitor the situation through "attendant feeding," in which the parent birds hold the chicks while the staff feeds them. After that, we could not confirm any feeding from the parent birds.　Five days later, on the morning of November 12, I weighed the birds and found that they had not lost any weight since last night. I couldn't believe my eyes, but the weight was the same no matter how many times I weighed her. I wondered, "Could it be ......." So I stopped feeding the chicks that day.
　However, the next day's weight was also up, so at this point I became convinced that the parent birds were feeding the chicks. Still, we could not confirm that they were feeding at all. We decided to set up a video camera to check the chicks at night, and when we went to the exhibit in the evening, we saw the parent birds feeding the chicks at that very moment.
　I succeeded in taking a picture of the parent birds feeding the chicks, even though my hands were shaking. I will never forget the joy and excitement I felt at that moment. It was the moment when my conviction finally turned into truth. After we confirmed that the parent birds were feeding the chicks, their weight gain was about the same as the growth of the artificially raised chicks up to about 50 days after hatching. From then on, the growth curve was much higher than that of the artificially raised chicks, and they grew steadily with only feedings from the parent birds. More than six months after their birth, they have grown to weigh approximately 25 kg and are now nesting from the parent birds and swimming in the pool in good health.
　Based on the failure in 2012, we considered and implemented improvement measures, which led to the success of natural chick rearing. Our goal for the future is to return the chicks to their parents at an earlier stage.
　（Kenta Tsukui)