one of the most valuable natural products 

 ever appropriated by humans). 



For a microbe, a stinky chemical repre- 

 sents a flag of possession. For a hyena, it's 

 a deterrent. But what about the dead bird 

 itself? If the bird had wanted to deter po- 

 tential predators by a stink, shouldn't it 

 have had to stink while it was still alive? 

 Perhaps the post-mortem stink should be 

 viewed as just a chemical weapon evolved 

 by a microbe without any cooperation 

 from the dead bird. 



Nevertheless, I'm suspicious because 

 the only two New Guinea bird species that 

 I've known to stink so quickly are both 

 big, clumsy, noisy, slow-moving species 

 that represent lots of meat for a potential 

 predator, and that seem otherwise ill- 



equipped to deter predators. If you fill 

 yourself with a stinking poisonous chemi- 

 cal while you're still alive, you have to de- 

 velop resistance to the chemical yourself 

 You might find it much better to harbor 

 potentially stinky microbes and keep them 

 suppressed while you're alive, but ready 

 to stink as soon as you die. Or you could 

 design your tissue chemistry to attract a 

 stinky microbe after you die. If a predator 

 then makes the mistake of killing and eat- 

 ing you, it will get sick and learn to avoid 

 killing your relatives in the future. In the 

 language of population genetics, that's 

 called "increasing your inclusive fitness," 

 or passing on your genes by aiding the sur- 

 vival of relatives sharing your genes, even 

 though you yourself don't survive. That's 



A female crested bird of paradise: does her plain plumage 

 encode an untold evolutionary story? 



why animal parents risk their lives to de- 

 fend their young, and why worker ants in 

 an ant colony forgo reproduction. 



Naturally, all that I can offer at present 

 to explain stinking birds is this speculation 

 without evidence. It might prove to be 

 nothing more than one of those "just-so 

 stories" that biologists are often accused of 

 dreaming up to provide a functional expla- 

 nation where there really is none. But I 

 have a clearly formulated, testable hypoth- 

 esis. I propose that an ambitious chemical 

 ecologist with a weak nose and strong 

 stomach (1) measure the rates at which e- 

 yos and pinis stink after death, compared 

 with other birds, (2) identify the stinking 

 chemical, (3) identify the microbe or en- 

 zyme synthesizing the stinking chemical, 

 (4) test the stinking chemical or other 

 chemicals in a dead e-yo or pini carcass on 

 various microbe and scavenger species, 

 and (5) do feeding trials to see if experi- 

 enced New Guinea predators avoid e-yos 

 and pinis when given a choice of non- 

 stinking, similar-sized birds. Might stink- 

 ing birds prove to harbor another drug like 

 penicillin? 



The "Case of the Living Hytrap" is my 

 other speculative example, designed to 

 tantalize chemical ecology graduate stu- 

 dents still searching for a thesis project. 

 This case began one afternoon in August 

 1965, when the Fore tribesman Paran 

 brought in a Papuan frogmouth (yasa in 

 the Fore language) that he had shot. As its 

 name implies, this raven-sized bird has a 

 very wide mouth reminiscent of a frog's. 

 Supposedly, the bird is stiictly nocturnal, 

 catches large prey like mice, lizards, and 

 large beetles, and sleeps during the day. 

 Paran insisted that this yasa, which he had 

 just shot that afternoon, had been sitting 

 motionless on a branch of a tree, with its 

 mouth wide open. He explained that he 

 had often seen yasas in that posture during 

 daylight hours, and that insects flew into 

 the bird's cavernous maw, attracted by a 

 smelly, sticky paste on its palate. 



My first thought was, nonsense! If so, 

 frogmouths would have achieved every 

 species' evolutionary dream — getting 

 food without work or cost. Then I reflected 

 that there was indeed a cost, that of syn- 

 thesizing the sticky chemical bait. On the 

 other hand, a raven-sized bird would have 

 to attract a lot of flying insects before its 

 strategy of setting itself up as a living fly- 

 trap could rate as successful. Then again, 

 Paran was a cautious observer who had 

 been right about everything else that he re- 

 ported to me. My confidence in Paran in- 

 creased when I read a note by an Aus- 



Frithfoto; Bruce Coleman, Inc. 



10 Natural History 2/94 



