SAMPLINGS 



Cooked Fish 

 and Fowl 



It's no secret that Earth's 

 warming climate is imper- 

 iling many denizens of 

 the maritime north. Two 

 new studies show its ef- 

 fect on the breeding be- 

 havior of the Atlantic cod 

 and a common seabird 

 known as the Arctic tern. 

 Cod populations have 

 suffered precipitous de- 

 clines in recent years, 

 largely because of overfishing. In the North 

 Sea, the species is now virtually absent from 

 its southern range. To understand why, Anna 

 Rindorf and Peter Lewy, fisheries scientists at 

 the Danish Institute for Fisheries Research in 

 Charlottenlund, analyzed hydrographic 

 records and cod survey data spanning the 

 years 1983 until 2003. The investigators dis- 

 covered that the recent series of warm, windy 

 winters swept cod eggs and larvae northward 

 and may have reduced their survival in the 

 southern parts of their range. The cod's ten- 



What's in a Mane? 



African lions have been classified into as many 

 as twenty-three subspecies, many of them on 

 the basis of variations in the appearance of 

 the males' manes. Some populations have an 

 extensive coverage of long, dark hair, whereas 

 others have almost no shag at all. Even within 

 populations, manes vary a great deal accord- 

 ing to a given lion's age, health, nutrition, so- 

 cial status, and testosterone levels, among 

 other factors. A recent study, however, shows 

 that yet another factor affects mane growth, 

 and that manes may not be such a good way 

 to distinguish subspecies after all: the king of 

 beasts' mane, it seems, varies with climate. 



Bruce D. Patterson, a zoologist at the Field 

 Museum in Chicago, and three colleagues 

 studied lions living in seventeen zoos in vari- 

 ous climatic regions of the United States — 

 many of the factors that affect mane growth 

 in wild lions are held constant in zoos. Sure 

 enough, climate explained much of the varia- 

 tion among the zoo lions' manes. Patterson's 

 team concludes that the manes of many of 

 the subspecies may actually reflect environ- 

 mental — not genetic — differences. 



An abundant mane signals a male's 

 prowess, but the social advantages it confers 



12 NATURAL history September 2006 



Cod fishing in Norway, above; Arctic tern, far left 



dency to spawn where it was born leads sub- 

 sequent generations to begin their travels at 

 ever higher latitudes. Without a string of cold, 

 calm winters and restrictions on fishing in 

 southern areas, the cod of the North Sea is 

 unlikely to regain its former range, never mind 

 its former numbers. {Journal of Applied Ecolo- 

 gy 43:445-53, 2006) 



In a second study, Anders P. Moller, an evo- 

 lutionary biologist at Pierre and Marie Curie 

 University in Paris, and two colleagues discov- 

 ered that by 1998 Arctic terns were laying 

 eggs eighteen days earlier than they were in 

 1929. Generations of biologists have been fit- 

 ting birds with identifiable leg rings for more 

 than a hundred years. Because young birds 

 are ringed before they leave the nest, Moller 

 could estimate when, on average, terns laid 

 their eggs. He then related the historical egg- 

 laying dates to data on local and regional cli- 

 mate. Steadily warming temperatures, Moller 

 says, explain the advancing dates. (Journal of 

 Animal Ecology 75:657-65, 2006) 



— Nick W. Atkinson 



conflict with the distinct physiological disad- 

 vantage — for a desert-dweller — of trapping 

 heat. Indeed, wild lions from equatorial 

 deserts tend to be virtually maneless com- 

 pared with lions from cooler habitats. 

 Investigators have assumed that reduced 

 manes are an adaptation to heat. 

 Patterson's group, however, 

 found that winter — not 

 summer — temperatures deter- 

 mined mane growth. Yet manes 

 can't be an adaptation to cold 

 because female lions don't have 

 them. Clearly, it's going to take 

 more work to figure out the 

 mane game. {Journal of Mam- 

 malogy 87:193-200) —N.W.A. 



Male lion in Kenya, with the wind 

 in his mane 



Written in Stone 



A dogma of the Earth sciences may be on 

 shaky ground. Geologic hotspots — long 

 thought to be relatively fixed points be- 

 neath Earth's shifting tectonic surface — are 

 themselves moving around. 



Hotspots are areas of long-term vol- 

 canic activity that have served as handy 

 reference points for tracing the move- 

 ments of tectonic plates. The Hawaiian Is- 

 lands, for instance, are thought to have 

 formed from the lava spewed by a hotspot 

 up onto the Pacific plate as the plate 

 moved northwestward over the hotspot. 

 The islands, known as a hotspot "trace," 

 thus record the track of the plate over the 

 hotspot (which is now centered under the 

 Big Island of Hawai'i). From the ages of the 

 islands, the direction and speed of the 

 plate's movement can be inferred. 



To model the movements of the planet's 

 plates, earth scientists have assumed for 

 more than three decades that the hotspots 

 remain fixed relative to one another, and 

 that the plates themselves have not under- 

 gone any recent reorganization in the ways 

 they butt up against one another. Now a 

 statistical analysis by Shimin Wang and Mian 

 Liu, geophysicists at the University of Mis- 



