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The endangered Sumatran rhino is on the brink of extinction, and some of the few remaining animals are too stressed or damaged to get pregnant. Conservation officers are scrambling to use breeding programs to save them, but it may already be too late.

The world is currently in the midst of a major extinction event due to human activities such as deforestation and pollution. Many animal populations have become too small, dispersed and unable to reproduce fast enough to remain sustainable. It’s sad, and it can have a lot of ripple effects – having a great diversity of species on the planet helps give people the air, water, food, medicine and energy that we need to thrive.

There is no single answer to the problem. A lot of work is focused on protecting habitats to save biodiversity – like the Half-Earth project by the late biologist EO Wilson. Such work is vital, but equally urgent is learning more about the biology of how these animals make babies. Unfortunately, far less money is spent on wildlife reproductive science than on ecosystem protection.

As a research veterinarian with 25 years of wildlife breeding experience, I have seen firsthand in conservation breeding facilities how complicated and difficult successful sex can be for many animals. . Even at the height of breeding season, clouded leopards can injure each other instead of making babies if there is no chemistry in the pair. Some species of frogs will not be able to reproduce if there is just a slight change in temperature or humidity in their environment.

Yet researchers understand extremely little about wildlife reproduction: less than 5% of mammalian species have had their reproduction characterized at cellular and hormonal levels. The number is even lower for non-mammalian species. It’s a lack of comic knowledge.

Understanding reproductive biology is extremely valuable, both for saving small populations through assisted reproduction, and also for determining what is wrong with natural populations struggling to reproduce in the wild.

Fertility depends on animal diet, hormone levels, stress levels and more. Examination of fecal samples has shown that lions and whales can be stressed by human encounters, for example, which could affect their ability to have children. In many animals (including humans), poor nutrition for a pregnant mother can affect the health of her offspring, creating a long-term effect on reproduction that spans generations. In one particularly interesting case, researchers in the early 2000s realized that their efforts to feed supplemental food to an endangered New Zealand wild parrot, the kakapo, had the undesirable effect of biasing the chicks towards males.

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Increasing our understanding of reproductive biology is daunting. It can be difficult even to collect semen – many wild animals must be sedated to obtain samples; getting sperm from frogs requires the right injection of hormones, which vary from species to species. Freezing samples is also very tricky, as protocols must be species-specific.

There are life-saving biobanks that freeze and store sperm, eggs, embryos, and reproductive tissues (similar to seed banks), including one at the Smithsonian Institution. But I estimate they cover less than 1% of the 5-10 million species on the planet.

In vitro fertilization (IVF) is highly sensitive to temperature, pH, and culture media or materials used to grow cells in the laboratory. We now know that IVF should be performed at 39 degrees Celsius for ruminants, 38.5 degrees for cats and 37 degrees for rodents, with near zero tolerance for temperature variations. Years of hard work have led to the identification of a particular protein from the oviducts that helps stabilize the sperm of sheep, cattle, pigs and the Iberian brown bear.

There are success stories, where decades of hard work, including in reproductive science, have resulted in successful breeding programs. The number of giant pandas, for example, has increased from around 150 in the early 2000s to more than 600 in captivity today. Black-footed ferrets have gone from just 18 individuals rescued in the 1980s to hundreds bred in captivity and reintroduced into the wild, in part through artificial insemination with fresh or frozen semen samples. But we need a lot more knowledge to get similar results for other species.

We also have to go fast. Last-minute efforts to save a few remaining rhinos through assisted breeding are laudable, but they should have started many years ago.

There is no point in conserving habitats if animals face threats to their reproduction. A crucial – and sorely overlooked – part of the solution must be the study of reproductive biology, so that we can understand how and why species thrive or struggle, and how best to help them – before it happens. be too late.

Comizzoli is a biology researcher at the Smithsonian’s National Zoo and Conservation Biology Institute in Washington. This piece was co-produced with Knowable magazine.


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