Keep looking up: Australian lace monitor perches 

 in a stringybark eucalyptus tree. 



One Big 

 Toxic Family 



What makes the bite of the Komodo drag- 

 on a wound that can kill? Most biologists 

 would point to the bacterial infection it 

 causes. According to a new study, howev- 

 er, there may be a better explanation: ven- 

 om. Fourteen scientists from six nations, 

 led by Bryan G. Fry, a biochemist at the 

 University of Melbourne in Australia, dis- 



covered that 

 iguanas and moni- 

 tor lizards (the 

 group to which 

 Komodos belong) 

 have venom 

 glands in their 

 mouths. The in- 

 vestigators found 

 that, in rats, the 

 venom of the lace 

 monitor, an Aus- 

 tralian cousin of 

 the Indonesian 

 dragon, reduced blood pressure and clot- 

 ting. Both effects would be handy for in- 

 ducing loss of consciousness and extensive 

 bleeding in prey. 



Among reptiles, only snakes and two 

 lizards — the Gila monster and its close rela- 

 tive, the beaded lizard — were previously 

 known to possess venom. Its rarity in lizards 

 had led biologists to think venom evolved 

 independently in snakes and lizards. But the 

 discovery of venom glands in iguanas and 

 monitor lizards — along with the genes nec- 



Is There a Doctor in the Barn? 



All animals get sick from time to time, but 

 most of them can't just reach for the aspirin. 

 Anecdotes of nonhuman species that seem 

 to self-medicate abound, but few have been 

 experimentally corroborated. Now a study 

 of domestic sheep shows that their pharma- 

 ceutical skills are surprisingly sophisticated. 



Juan J. Villalba, an animal behavior special- 

 ist at Utah State University in Logan, and two 

 colleagues conditioned four-to-five-month- 

 old lambs to eat barley grain and food laced 

 with tannins or oxalic acid. Each food gave 

 the lambs some temporary discomfort: barley 

 grain causes heartburn, tannins cause indi- 

 gestion, and oxalic acid causes low energy 

 and shortness of breath. After they were ac- 

 customed to eating each of the three foods, 

 the test lambs were conditioned to consume 

 the medicine appropriate to each food. 

 (A control group of lambs got no treatment 

 for each of their illnesses, but was instead 

 allowed to recuperate naturally.) 



After ten weeks of conditioning, all the 

 lambs were fed just one of the toxins at a 

 time, then given a choice of the three cures. 

 Only the lambs that had previously tried the 

 medicines and recovered from each ill- 

 ness — as many as five months earlier — were 

 able to select the appropriate medicine, 



demonstrating for the first time in nonhu- 

 mans the ability to learn about a range of 

 cures for different maladies. Villalba's study 

 adds scientific weight to the idea that early 

 humans may have acquired pharmacological 

 knowledge by observing the foraging 

 behavior of animals. (Animal Behaviour, in 

 press, 2006) — Nick W. Atkinson 



essary for making at least nine different 

 toxins that are shared by snakes — has 

 forced a reevaluation of the reptiles' evolu- 

 tionary history. Fry and his colleagues say 

 that a system for venom production and 

 delivery probably evolved just once, in an 

 ancestor common to all venomous reptiles. 

 The system evolved 200 million years 

 ago — just when bite-size mammals were 

 diversifying and spreading. {Nature 439: 

 584-8, 2006) —S.R. 



Red Means Grow 



Sunny but parched, or rainy but gloomy: 

 only two seasons come and go in tropical 

 rainforests, and which one might encour- 

 age more plant growth seems a toss-up. In 

 the Amazon, it turns out, the dry season, 

 roughly July through November, is the 

 greener. Until recently, only a few locales 

 had been studied, but in those areas the 

 leaves fall early in the dry season, some of 

 them choked by moss that prospers dur- 

 ing the preceding rainy months. New 

 growth replaces the dead leaves as the 

 dry season advances. A new study shows 

 that the same pattern applies to most of 

 the Amazon basin, except where the for- 

 est has been disturbed by people. 



Since 2000, a NASA satellite has 

 recorded the amount of red light reflected 

 by the Amazon rainforest. Plants absorb 

 red wavelengths of light for photosynthe- 

 sis, and reflect green. Thus, the less red 

 they reflect, the more they are growing 

 and greening up. A team led by Alfredo 

 Huete, an ecologist at the University of 

 Arizona in Tucson, found that, according to 

 the satellite data, the greenery increased 

 by 25 percent in the dry season. But where 

 people had converted the forest to agri- 

 culture or other uses, the satellite de- 

 tected exactly the opposite effect. In 

 those areas, the red-light reflection indi- 

 cated that the remaining flora had 

 "browned down" by 25 percent. 



Big rainforest trees have deep roots 

 that can tap underground water reserves 

 in all but the driest years, says Huete, so 

 their growth depends more on sunlight 

 than rain. The relatively puny vegetation 

 in disturbed areas has no such advantage; 

 it withers once the rains stop. (Geophysi- 

 cal Research Letters 33:L06405, 2006) 



—S.R. 



Mary's smart little lamb 



June 2006 N A T U K A I HISTORY 



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