Birds do it. Bees do it. Even bats, penguins, cheetahs and elephants do it. Sex spans the animal kingdom. But the way animals get the job done varies tremendously from one species to the next. Most of those reproductive strategies, according to a new study, have been completely ignored by science. WATCH: The world's most promiscuous bird is a sparrow that lives in tidal marshes in the northeastern United States. Researchers found that in most nests, saltmarsh sparrow chicks had multiple fathers. Jorge Ribas gets the sordid details.
The Same Old Species
Of the more than 12,000 studies published in major journals over the last decade, more than 90 percent focused on the same old species, scientists reported in the journal Molecular Reproduction & Development. Mice, rats and cows topped the list. Such a narrow focus is a major opportunity lost, said David Wildt, head of the Center for Species Survival at the Smithsonian Conservation Biology Institute in Front Royal, Va. By tapping into the diversity of animal reproduction, he said, scientists could better protect threatened species. A broader view might also help human couples coping with infertility. "There's this powerful biological diversity out there," Wildt said. "And most species have never been studied." WATCH: Synchronized wing beats help mosquitoes meet their mates. James Williams discovers what the flap is about.
Smithsonian's National Zoo
In 1998, a mere 124 giant pandas lived in captivity around the world, most of them in China. Breeders there were having an impossible time getting the animals to make babies. Part of the problem was that nobody knew the details about how the animals reproduce. After some basic research, scientists discovered that female giant pandas become fertile just once a year for a tiny window of time, lasting between 24 and 72 hours. Males, meanwhile, are sexually active for about half year, from October through May. "We learned so much through all of this," Wildt said, "that we started turning around the breeding program." Today, there are 293 captive giant pandas worldwide, 253 of them in China. In just a decade, the number of animals in captivity has more than doubled. For such an endangered species, a strong captive community is like an insurance policy for shrinking wild populations. WATCH: Why is it so special when a giant panda cub is born? The problems associated with panda reproduction is explored in this Animal Planet video.
Big, cute mammals aren't the only animals that can benefit from some attention to their sex lives. Consider seahorses. Most people know that male seahorses carry the pregnancies, even though they also provide the sperm. For a long time, scientists assumed that a male seahorse ejaculated through an opening in his baby-carrying pouch to fertilize eggs that were placed there by the female. Careful dissections, however, revealed that seahorse sperm actually travels outside the body and into the pouch. What's more, the male produces only a very tiny amount of sperm, and almost every one fertilizes an egg. Those findings suggest that good water quality is essential for seahorse sperm to get to their destinations safely. Seahorse numbers are dwindling as many of them are scooped out of the sea for use in Chinese traditional medicine, said Bill Holt, a reproductive biologist at the Zoological Society of London. Basic studies on the reproductive systems of these and other animals are crucial to keep life going. "The more biology you know," he said, "the easier it is for people preserving seahorses to make sure they get everything right." WATCH: Seahorse dads are an anomaly in the animal kingdom, because they are the ones who are impregnated and go through labor. Not only that, but they can actually give birth to up to 1500 babies at a time!
Smithsonian's National Zoo
Conservation Through Copulation
As a growing number of people struggle with infertility, there may be a vat of untapped insight in the way other animals manage to create life. Female bats, for example, are able to store sperm for an extraordinarily long period of time before fertilization occurs. Giant pandas produce sperm that freezes well. Pigs and koalas have resilient sperm that resist DNA damage, unlike rhinoceros sperm, whose DNA deteriorates faster than any other animal. These details inform conservation strategies: To do artificial insemination on a rhino, for example, you have to be quick! But that's not all. WATCH: In this Animal Planet video, Saba Douglas-Hamilton lingers too long in rhino country. When an aggressive male rhino takes notice of her, she has only a log for protection.
Borrowing From Nature
Figuring out the reproductive strengths and weakness of other species could lead to better ways of preserving vulnerable human sperm for fertility treatments. The research could also aid agricultural breeding programs. "If we could understand why rhinos and sheep are so susceptible to DNA damage -- and we have a number of ideas about this -- we could find treatments," Holt said. If treatments become available, he added, "then, there would be applications to humans." WATCH: We've cloned sheep, mice, dogs and more. So are humans next?
Cheetahs Are Not Cows
Considering the reproductive systems of overlooked species can foster an appreciation for the multitude of ways that mating occurs in the animal kingdom -- even when species are closely related to each other. Female domestic cats, for example, only ovulate after they've mated. Clouded leopards, on the other hand, release eggs spontaneously. Cheetahs produce a lot of abnormal sperm, while ocelots produce a large percentage of normal ones. These are all types of cats, but differences among groups are significant. "When you do comparative studies, you find out that not only are cows not cheetahs, cheetahs aren't even tigers, and tigers aren't even leopards," Wildt said. "There's an amazing variation among species in terms of reproductive mechanisms." WATCH: From the archives of Discovery: Watch as this group of cheetahs feasts on gazelle and zebras. Learn more about cheetahs and hunting in this video.
The ancestors of modern carpenter bees may have vanished from Earth roughly 65 million years ago, around the same time the dinosaurs were wiped out, a new study finds.
Researchers examined the DNA of four types of carpenter bees -- belonging to the group Xylocopinae -- from every continent, except Antarctica, to search for clues about their evolutionary relationships. Peering back into the lineages of the bees, the scientists noticed something unusual with all four groups, beginning roughly 65 million years ago, at the boundary between the Cretaceous and Paleogene periods.
"We can track periods of diversification and stasis," lead study author Sandra Rehan, an assistant professor of biological sciences at the University of New Hampshire, told LiveScience. "There was a period where there was no genetic diversification happening for millions of years -- a real dearth of speciation. This is an indication of a mass extinction event." (The 10 Weirdest Animal Discoveries)
The end of the Cretaceous Period, corresponding to the beginning of the Paleogene Period, was already known to be a dynamic time in history. It is commonly thought that a massive asteroid or comet slammed into Earth 65 million years ago, wiping out the dinosaurs and killing up to 80 percent of all species.
"We found this mass extinction event signature in the DNA that just happened to correspond to the extinction of dinosaurs, which was a major change in the global diversity at the time," Rehan said.
Rehan and her colleagues did not study possible relationships between the bee and dinosaur extinctions, but said the similar timings act as secondary support for both theories.
Since there are no reliable fossil records for carpenter bees, the researchers used a technique called molecular phylogenetics. This involves analyzing DNA sequences and searching through the data for evolutionary insights. To understand where in time evolutionary changes were happening, the researchers used fossils of other types of bees as reference points.
"We used fossils of other lineages of bees to make inferences and calibrate time," Rehan explained. "Then, we backtracked over time."
The new research suggests the bee extinction lasted about 10 million years, she added.
The findings should generate great interest in the field, said John Ascher, assistant professor in the department of biological sciences at the National University of Singapore and a research associate in the division of invertebrate zoology at the American Museum of Natural History in New York City. But Ascher, who wasn't involved in the current research, said studies that use molecular phylogenetics tend to be "speculative in their reliance on unrealistic and insufficiently justified evolutionary models."
"I would be much more enthusiastic about the discovery of a reliable fossil within any of the extant Xylocopinae tribes (the authors note that there are none)," Ascher told LiveScience in an email.
Still, the findings could shed some light on the declines that are being observed in current bee populations, Rehan said.
"Bees have gone through hard times, and negative effects have occurred," Rehan said. "We can maybe learn from the past, and learn how pollinators and plants respond to natural disturbances. If we can understand what happened in the past, it can help us understand the current perturbations and loss of diversification."
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Wipe Out: History's Most Mysterious Extinctions
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6 Strange Species Discovered in Museums
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