[Adam Bolton] said Einstein rings, which are "very rare," offer astronomers an opportunity to calculate the mass of an elliptically shaped foreground galaxy, composed of stars and dark matter, the invisible form of matter thought to make up most of the mass of the universe. Astronomers can indirectly observe dark matter by measuring its gravitational influence.
Virtually all salamanders are carnivorous, living mostly on insects, but the perpetually dark caverns of the Ozarks are mostly devoid of such life. Dante Fenolio, then at the University of Oklahoma and now at the University of Miami, led atomic isotope studies to track the source of the carbon and nitrogen in the animals, and showed that the bat droppings were the salamanders' main food group.
Bat guano is as nutritious as insects, the team found -- perhaps because bats' short intestines pass much of their diet undigested. Other cave dwellers may also depend on guano, Fenolio and colleagues suggest in the Nov. 16 issue of Proceedings of the Royal Society B. They warn that the decline of bat species in some environs may threaten such species.
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