the gestation period of rhinos (487 days) is what percent longer than the gestation period of dogs (65days).

percent change = ((new value) - (reference value)) / (reference value) * 100%

... = (487 - 65) / 65 * 100%

... = 422/65 * 100%

... = 6.492 * 100%

... ≈ 649%

The gestation period of rhinos is 649% longer than the gestation period of dogs.