The predators may well have got the message, according to a study by Molly Cummings of the University of Texas at Austin. Her team collected strawberry poison dart frogs from western Panama, and measured how toxic the frogs' skin chemicals were. She also measured their colours precisely, using an instrument called a spectrophotometer, and determined how easily predatory birds could detect them. As before, the brighter frogs were more toxic, and Cummings' calculations suggested they were also more conspicuous to the birds. Back in , she also showed that predatory birds quickly learn to avoid the colourful frogs.
Clearly, being poisonous is advantageous to the frogs. The question is, how did they become so lethal? View image of Poison dart frogs evolved in rainforests millions of years ago Credit: The group was born some million years ago, somewhere in the forests of northern South America, says Juan Santos of the University of British Columbia in Vancouver, Canada.
Deaths Bright Dart by V. C. Clinton Braddeley (1982, Paperback)
The poison dart frogs' ancestors were not poisonous, and nor were they colourful or small, says Santos. In a study published in , Santos attempted to trace the ancestry of the frogs by examining their genes. The results are not definitive, but it seems the frogs are descended from something like a true toad , complete with warts. View image of Poison dart frogs may be descended from toads Credit: This common ancestor was probably "diurnal", meaning it was active during the day, says Santos.
Most of the known poison dart frogs are diurnal, whereas most other frogs, including all of the poison dart frogs' likely ancestors, are active at night. In that respect, modern poison dart frogs are similar to their last common ancestor. But in another respect, the ancestor was completely different: The poison evolved some time after the origin of the poison dart frog lineage, according to Santos' data, and different groups evolved it at different times.
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View image of Why are golden poison frogs so deadly? The first was around 30 million years ago, while the most recent was just 2. The key to the story is that the frogs don't make the poisons themselves. They get them from animals like ants that they eat. The ancestors of poison dart frogs may have started eating toxic ants by sheer chance, and begun harbouring the poisons in their bodies. Some of the key chemicals on the frogs' skin have been traced to ants, beetles and millipedes.
This seems to fit with Santos's claim that the frogs acquired the ability to make poison on several different occasions. View image of Rainforests are teeming with toxic insects Credit: These early poison dart frogs had a big problem: It is not yet clear how they managed to withstand and retain the poison, says Summers. One idea is that they had a high metabolic rate, meaning their bodies could process nutrients and other chemicals quickly.
In effect, the frogs were "pre-adapted". That may explain how the frogs became so poisonous, but why did they do it? Rainforests are dangerous places, with many predators out to eat a tasty frog.
Death’s Bright Dart | Cary Graphic Arts Collection
But many similarly small animals have found less extreme ways to survive, such as camouflaging themselves. There may have been something specific about the poison dart frogs' ancestors that made them predisposed to defend themselves using poison. Or it could be largely down to luck, says Summers. Whatever the truth, nowadays the frogs are not the only ones benefiting from their poisons.
Neuroscientists are studying the toxins in the hope of designing new drugs. There are some red herrings too, very cleverly inserted. So cleverly, that I though I'd picked out the murderer early on, but was proved wrong in the end.
Baddeley has a slightly Dickensian gift for names - just the lovely sort of thing I like to find in my English mysteries. There is Ada Trott, Mrs. Mostyn-Humphries has some peripheral involvement with the plot, but I just liked reading his name and saying it out loud. Davie has had to confront an unsavory bookseller straight out of Dickens named, Mr. Books are not the only thing Stumpf is selling or buying. In the small office the weedy young man was on guard by the tray of photographs and a respectable looking middle-aged man was endeavoring to pretend that he was only standing there by accident.
Unfortunately the young man would not take a hint. Outside Davie paused in the dazzling sunlight, watching a military pigeon strutting in the road tirelessly engaged on the quest for provender.
He was not aware that he, in his turn, was being inspected by Mr. Stumpf from the window above the shop. In view of what happened later it was a good thing that Davie turned left into Great Russell Street. At least he had not given Mr. Stumpf the impression that he was staying at the Gainsborough Hotel. He was in fact bound for L'Etoile in Charlotte Street, where he proposed to treat himself to an admirable luncheon.
The line about the pigeon's 'quest for provender' is perfection. To read a review of one of V. Posted by Yvette at Friday's Forgotten Books , V. Peggy Ann March 16, at 3: Anonymous March 16, at 4: When we value our stock we want our customers to be happy with the price, when we list our stock we want to describe everything you want to know before making a purchase, when dealing with customer service we will strive to make sure you?
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