Zoologist Wilmer Tanner poses with a mounted tiger at Brigham Young University’s Life Sciences Museum.Wilmer Tanner, Wikimedia Commons

For decades, it's been standard practice to collect and kill specimens for museums and private collections. Most such animals come from small and isolated populations, though.

In a paper published in the latest issue of Science, lead author Ben Minteer of Arizona State University’s School of Life Sciences and colleagues argue that these so-called “voucher” specimens can harm already weakened plant and animal populations, possibly leading to the species’ extinction or re-extinction.

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A female pygmy slow loris clings to a human arm.Lionel Mauritson, Wikimedia Commons

Researchers have collected live specimens for bringing back to the lab. The collected individuals might not survive the journey, or captivity. They might not breed in captivity as well, so this practice is also less than optimal.

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Great spotted woodpecker feathers, ready for collectionChristian Fischer, Wikimedia Commons

Sometimes unique items can help to distinguish one species from another. Feathers and fur, which animals naturally shed, can help to identify new species. Minteer and his team, for example, mention that collected feathers have already been employed for such a purpose.

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A U.S. Customs and Border Protection chemist reads a DNA profile.James Tourtellotte, Wikimedia Commons

DNA, even from dung, hair and other items, can help to reveal new species. It can also help scientists to noninvasively monitor the health of certain animal populations, both in the wild and in captivity.

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A dog gets its DNA collected on a swab.National Institutes of Health

Skin swabs, as for humans, can reveal an animal's genetic makeup. As Minteer and his team mention, “For rediscovered, rare and newly discovered species, molecular techniques, such as skin swabbing for DNA, are an increasingly effective way to sample a specimen to confirm an identity with no or minimal harm to the organism.”

Close-up of a western Nomada beeUSGS Bee Inventory

High-resolution photography is now being used to identify species. Images can capture details of an organism, such as this western Nomada bee, in incredible detail. Minteer and his colleagues also point out that photos helped researchers to recently discover a bird, Bugun liocichla, in India.

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Howler monkeys vocalizingWikimedia Commons

Field recordings of birdcalls, animal calls and more can also identify species. Like photography, the quality of the recording helps to tease out the species' distinctive features. Scientists can also analyze the calls using software that translates the sounds into visual patterns, which can then be compared with other known patterns.

Super-hot hydrothermal vents harbor unexpected life.NOAA

New species are often found in very hot or very cold spots, such as near undersea thermal vents or in icebergs. For example, numerous bacteria and other small creatures live next to “white smokers” like these, which spew out nutrients. NASA pays attention to such studies, noting what life might be possible in extreme temperature conditions that could also occur on other planets.

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Mount EverestWikimedia Commons

Remote spots, like mountainous regions or isolated islands, still yield new species. Usually, when larger collections of new animals are found in a single field exploration, the locations tend to be less-accessible places that have been poorly studied before.

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Goliath frogs are preserved at the Harvard Museum of Natural History.istolethetv, Flickr

Museums are full of species waiting to be discovered. That's because naturalists from the past would collect unusual specimens (see #1) and bring them to museums or to collectors. Most specimens are tucked away in drawers or other storage.

Lorna Steel, a curator in the Department of Paleontology at the Natural History Museum in London, told Discovery News, “It is great to see old collections being re-examined, and it demonstrates the scientific value of museum collections.”