The Macaque Shuffle

macaque dreamstime 16409287 The Macaque ShuffleSome tales only the dead can tell. And thanks to the clever use of some chemical isotopes, biologists can now use dusty old museum specimens to reveal how massive biodiversity losses can shuffle the diet of the species that still survive.

Since the early 19th century, the city-state of Singapore has lost more than 95% of its primary forest. Researchers estimate it has also lost 34% to 59% of all bird species, and 42% to 78% of all mammals, Luke Gibson of the National University of Singapore reports in the journal Primates. The long-tailed macaque (Macaca fascicularis) is one of two remaining primates on the island, and some 70% of the less than 1500 remaining macaques now live in nature reserves.

To see how Singapore’s massive ecological changes may have affected macaque feeding behavior, Gibson took hair samples from eight live macaques, and from six skins from macaques collected in Singapore between 1893 and 1944 that are now preserved in the Raffles Museum of Biodiversity Research. Then, he measured the ratios of certain carbon and nitrogen isotopes in the hair; the isotopic composition is heavily influenced by what the animals have eaten.

It turned out the carbon ratios were essentially the same in the animals from the two time periods – meaning both the dead and living animals foraged in the same kind of habitat. The nitrogen ratios, however, were different, indicating that modern macaques have shifted their diets. In particular, the data suggested the animals were now feeding at a lower “trophic level” – or lower down on the food chain – than they had in the past.

“This decline in trophic level may be because of the disappearance or decline of other species that compete with macaques for fruit,” Gibson writes. “Macaques consume mostly leaves, seeds, and fruit supplemented with some invertebrates and vertebrates, and increased fruit abundance may cause a proportional decrease of invertebrates and small vertebrates in their diet.”

The study “highlights the effect of continued habitat modification and associated biodiversity loss on animal communities,” Gibson concludes. “The ability of species such as the long-tailed macaque to persist despite extensive forest degradation may be possible because of their ability to alter their behavior.” And since macaques are now one of the most-widespread non-human primates, “their persistence in degraded forest habitats may be critical to the preservation of key ecosystem functions such as seed dispersal, in Singapore and beyond.”David Malakoff | May 31, 2011

Source: Gibson, L. (2011). Possible shift in macaque trophic level following a century of biodiversity loss in Singapore. Primates DOI: 10.1007/s10329-011-0251-9

Image © Sunsetman | Dreamstime.com

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3 Comments

  • Judith June 1, 2011 at 11:07 am

    Museum professionals work diligently to care for these important materials, only to hear the “dusty old museum specimens” meme every time use of collections hits the news. You would think all that dust would mess with the isotope analysis…

    Reply

  • Joshua June 2, 2011 at 2:19 pm

    I concur with Judith, museums are active places where thousands of samples are exchanged among institutions every year. These samples, as you point out, are used as the basis for important work discovering new biodiversity, documenting environmental changes and helping scientists create novel and innovative ways to address threats to global sustainability. With all the projects museum collections fuel, they hardly get a chance to collect dust!

    While I understand that the phrase “dusty old museum specimens” might have been chosen for literary emphasis, it belies the importance of collections based research. With museums throughout the world facing looming financial difficulties, it is important for the educated readers of Conservation Magazine, recognize, and speak out for, the importance of natural history institutions.

    Reply

  • Chris June 2, 2011 at 6:28 pm

    It’s also important to realize that using museum collections as a source of biological information is not exactly “novel” – isotopic studies of diet have been going on for years, on extant, extinct, and even fossil species. From dental microwear to CT scanning and PCR amplification, the utility of collections continues to grow with each new methodological advance. And despite this, we still have time to dust occasionally!

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