White-bellied 

 ^g^^wa^bird 



SAMPLINGS 



Animal Party Line 



A number of animals eavesdrop on warn- 

 ings sounded by other species: if a predator 

 is afoot, everyone wants to hear the news. 

 Most prey species known to heed "second- 

 language" alarm calls are social creatures with large vocal reper- 

 toires of their own — good indicators of intelligence. 



But Gunther's dik-diks don't fit that pattern. Mated pairs of 

 the miniature antelopes live by themselves on multi-acre territo- 

 ries on the East African savanna, and they make only a few quiet 

 little calls, including just one alarm: the breathy "zik-zik" behind 

 their name. So when local lore that dik-diks heed the alarms of 

 white-bellied go-away birds reached Amanda J. Lea, two fellow 

 undergraduates at the University of California, Los 

 Angeles, and their advisor, Daniel T. Blumstein, 

 they pricked up their own ears. 



Go-away birds announce incoming predators from 

 their treetop perches for all to hear. When the re- 

 searchers played recorded go-away-bird alarm calls, 

 dik-diks usually assumed a vigilant stance or stopped 

 foraging and headed for cover, whereas they all but 

 ignored broadcasts of unalarming birdsong. 



Dik-diks can't afford to miss out on a warning: 

 more than twenty predators include dik-dik in their 

 diets. Lea and Blumstein expect that interspecies 

 eavesdropping is much more common than biolo- 

 gists now appreciate among vulnerable animals — 

 regardless of how social, vocal, or intelligent they 



Gunther's $ 

 - dik-dik { 



mm rjftiriii-'Til 



are. {Behavioral Ecology) 



-Rebecca Kessler 



Wet Suit 



Predatory reptiles called ich- 

 thyosaurs cruised the oceans 

 between 230 million and 90 

 million years ago. In a classic 

 case of convergent evolution, 

 their body and fin shapes re- 

 sembled those of today's dol- 

 phins, tunas, and great white 

 sharks — the fastest swimmers 

 in the sea. A new study shows 

 that the convergence even ex- 

 tended to the molecular com- 

 position of the animals' skin. 



Soft tissues are seldom pre- 

 served, but a few rare ichthyo- 

 saur fossils still bear patches of 

 skin that clearly display multi- 

 ple layers of fiber bundles. Liv- 

 ing dolphins, tunas, and sharks 

 have similar strata, in which the 

 fibers are made of collagen — a 

 strong protein that, in layers, 

 stiffens skin against flowing 

 water. The ichthyosaur fibers 

 were probably collagen, too, 

 but proving it isn't easy: scien- 

 tists usually identify fossilized 



Fossil ichthyosaur 



molecules chemically, a tricky, 

 destructive procedure requir- 

 ing large samples. 



Fortunately, two biologists 

 found a way around the prob- 

 lem. Knowing that collagen 

 molecules pack themselves 

 in bands separated by about 

 three-millionths of an inch, 

 Theagarten Lingham-Soliar 

 and James Wesley-Smith of the 

 University of KwaZulu-Natal 

 in Durban, South Africa, ex- 

 amined a small sample of fos- 

 silized ichthyosaur skin with a 

 scanning electron microscope. 

 Sure enough, they found bands 

 with just the right spacing. 



The pair thinks electron 

 microscopy could solve other 

 questions about ancient soft 

 tissue, such as the contentious 

 nature of "proto-feathers" in 

 some Chinese dinosaur fossils, 

 which may turn out to be noth- 

 ing more than degraded colla- 

 gen fibers. (Proceedings of the 

 Royal Society B) — S.R. 



THE WARMING EARTH 



Toot Spews Soot 



Lovable Little Toot has come in for a 

 scolding. An extensive survey of ship- 

 ping lanes along the Gulf Coast of the 

 United States concludes that tugboats 

 emit far more soot than any other kind 

 of vessel, and four times more than pre- 

 viously estimated. What's more, large 

 cargo ships emit twice the soot attrib- 

 uted to them, with serious implications 

 for global warming and air quality near 

 major ports. 



Daniel Lack and colleagues at the Na- 

 tional Oceanic and Atmospheric Admin- 

 istration's Earth System Research Labo- 

 ratory in Boulder, Colorado, measured 

 sooty emissions from ninety-six vessels. 

 Previous studies had observed only one 

 or two ships. Lack lists several factors that 

 make tugs the worst polluters: they burn 

 low-grade fuel, their engines are inefficient 

 because of frequent transitions between 

 idle and full power, and many receive poor 

 maintenance. Since tugs operate almost 

 exclusively within ports, they substan- 



tially degrade air quality in coastal cities. 



Ships now contribute less than 2 per- 

 cent of all airborne soot — which warms 

 the atmosphere — but global shipping 

 is expected to increase by as much as 6 

 percent annually. That bodes ill for the 

 climate, particularly in the Arctic. As ris- 

 ing temperatures shrink summer sea ice 

 and open passage to shipping, additional 

 settled soot will darken the remaining ice 

 so it absorbs more solar radiation, thus 

 accelerating the region's warming. (Geo- 

 physical Research Letters) — H.L. 



