The age-defying laboratory mouse known by his keepers as Yoda died peacefully in his cage in Ann Arbor, Mich., on April 22. The cause of death is unknown. Autopsy results are pending. The oldest known living member of his species at the time of his death, Yoda was 4 years and 12 days old.
Yoda carried a mutation that disables the production of three hormones required for normal growth. Scientists were studying the diminutive mouse to learn how hormonal irregularities enabled him to postpone signs of aging and associated diseases.