That was then, this is now – Over two decades of progress in rhinoceros reproductive science and technology

Despite dipping to perilously low numbers over the past century, all five rhinoceros (rhino) species still survive in the wild with four also in managed breeding programs. These managed populations have been essential for advancing rhino reproductive science and technology. Despite a plethora of challenges and the incremental nature of sound science, researchers have made significant progress over the past quarter century in broadening our knowledge of rhino reproduction, developing new technologies, and expanding the scope of existing research tools. When we compare the state of this scientific field a quarter century ago to where it stands today, there is much to celebrate. For example, at the turn of the century, the Sumatran rhino breeding program had failed to produce a single calf, the first rhino artificial insemination (AI) procedures had just been described, but no pregnancies had been documented, and in vitro fertilization (IVF) had not succeeded in any rhino species. As we reach the end of 2023, 8 Sumatran rhino calves have been born, a total of 17 white and greater one-horned rhino calves have been produced by AI, and 51 white rhino IVF embryos have developed into blastocysts. Furthermore, several theories based on the evidence available at that time have been disproven as additional scientific data have deepened our knowledge and understanding. However, many unanswered questions still exist, and reproductive technologies require refinement, development, or application to additional rhino species, so plenty of challenges remain on the landscape for future generations of rhino reproductive scientists to conquer.