The 4-month-old rhino died Friday of unknown causes, the Montgomery Advertiser reported.
Sarah McKemey, a public relations director for the zoo, said a necropsy will be performed to determine Ethan's cause of death.
"It is a shock and a loss to us for it to be so sudden and unexpected," McKemey said.
Indian rhinos are an endangered species; Ethan's birth, which was achieved by staff at the Montgomery Zoo impregnating female Jeta with sperm from Himal, a male rhino, was seen as a sign artificial insemination may help sustain the remaining population.
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