Depending on the mother animal, rhino species and season, rhinoceros offspring see the light of day a few weeks earlier or later. Findings should help breeding programs in zoos.
Female rhinoceros end their pregnancy (pregnancy) a week earlier in summer than in winter, reports Viennese zoologist Franz Schwarzenberger. The individual gestation period differs from rhinoceros female to rhinoceros female by up to seven weeks. They also carry their babies for different lengths of time depending on whether they are black, white or Indian rhinos, he explains in the journal General and Comparative Endocrinology.
Franz Schwarzenberger, who researches at the Institute for Physiology and Pathophysiology at the University of Veterinary Medicine (Vetmed) in Vienna, and a German colleague examined the hormone profiles of 35 rhinos kept in European zoos, which were created over three decades as part of pregnancy tests (pregnancy examinations). The researchers also compared the gestation periods of the individual animals and between different species.
Gestation averages 460 days for black rhinos (Diceros bicornis), 504 days for white rhinos (Ceratotherium simum), and around 480 days for great one-horned rhinos (Rhinoceros unicornis), reports Schwarzenberger. However, there are large variations within the individual species, namely gestation time differences of around seven weeks. There are also “pronounced individual differences” in the point at which the female sex hormone “gestagen” is first produced in the placenta to develop and maintain a pregnancy.
Due to the different lengths of daylight at the time of birth, the seasons also have a major influence on the duration of pregnancy, according to the Viennese researcher: “It is regarding a week shorter if the birth takes place in summer and not in winter.”
The findings should ensure that there are more rhino babies in zoos. “The implementation of new physiological findings in internationally coordinated breeding programs has already made a significant contribution to the fact that the number of breeding rhinos in zoos has increased significantly over the past few decades,” explains the scientist.
According to the Red List of the International Union for Conservation of Nature (IUCN – International Union for Conservation of Nature), free-living rhinos are either threatened with extinction, endangered or near threatened because they are shot by poachers. “The protection of wild populations and captive breeding are essential measures to ensure the conservation of rhino species,” says the Vetmed broadcast.
