Short natural history books
I've always been impressed by the intelligence of birds. Although we think of their tweeting as purely for mating and claiming territory, they are highly social animals. One time I came home from work and found a bird giving alarm calls in a nearby tree. It turned out there was a snake in the tree, and the bird was altruistically warning other birds to stay clear.
Another time I found a small bird tangled up in a net. Once again, there was another bird perched on a nearby bush, giving alarm calls. It was in obvious distress at the plight of its friend. When I cut the bird free, they both stopped making sounds and flew off together.
But crows always seemed like anarchists. They seemed to be nasty birds who ate roadkill, made unpleasant noises, and ripped apart garbage bags, spreading trash all over the sidewalk. This was virtually guaranteed to happen if the trash bag contained any bread, which they could smell from a large distance.
Since I moved to the countryside, I have come to realize how intelligent crows really are. Like other birds, they are social. But they're much smarter. One time I accidentally dropped a Cheez-It cracker on the ground only to find two blue jays (which are related to crows, being part of the same Corvid family) fighting over it ferociously a few minutes later. I tossed out a few more, but they were ignored; evidently they had discovered that it was not a Cheddar one as they thought, but the new Jack Cheese type, which was not as good.
Another time, while I was reading a book outside, I noticed a large number of crows gathered together in a field making strange “talking” noises to each other. This crow conference continued for several days in a row. When I approached to within 30 meters, they stopped talking, resumed their normal cawing sound, and flew away. I got the distinct impression that this was not fear, but embarrassment to have been caught practicing how to talk. We are just ordinary crows, they seemed to be saying. We're not talking, we don't have a language, and we're not planning an anarchist revolution, honest. The crows never returned. But clearly they had been up to something. Listen to my holy caws, they were probably saying.
This book by the late Lawrence Kilham, a professor of microbiology at Dartmouth, is the product of thousands of hours of close-up observation of crows. Writing in a clear naturalist style, Kilham describes their individual and collective behavior, territoriality, mating, and most of all, their intelligence. For example, he describes how crows act cooperatively to steal food from otters. One crow pulls the tail of an otter, using its beak as a pair of tweezers. When the otter turns around, a second crow will steal whatever food, typically a fish, the otter was carrying.
Crows do much more than caw; they make a huge variety of sounds, some of which can only be heard when close up. They use tools. They are highly territorial, and fight vigorously over territory with each other and with other species, particularly squirrels. Kilham describes how one group of crows acted cooperatively to expand their territory by walking 30 meters across the border and waiting for the other group to attack. The two groups then fought, no doubt quite noisily. Clearly crows are capable of premeditated, collective, purposeful action and, Kilham suggests, perhaps even thought.
He also relates how groups of crows would follow him around, making “cuckoo” noises and pecking on the ground to indicate that they would like some corn. Kilham formed kinship bonds with crows and especially ravens, which he says are even more intelligent than crows. Even so, crows are easily able to recognize individual humans by appearance and by their voice. Their ability to navigate at high speed through the complex three-dimensional maze of a forest is amazing. Corvids might never discover the second law of thermodynamics, but they're not just mindless animals either.
Most of this book consists of anecdotal observations about crow and raven behavior. There are many drawings, and a few sonograms of crow sounds, but no photographs and, disappointingly, little information on crow “language.” This book would have benefited by an audio CD. Kilham was, at heart, a naturalist, and loved crows. I suspect they miss him.
jul 20, 2014
“Every sound that every crow makes has a purpose,” says Michael Westerfield in this short book. Most of this book consists of anecdotes and observations made by visitors to his crows.net website. Most valuable is the accompanying CD which has recordings of the different types of calls, including alarm calls, rattling sounds, mobbing calls, mating vocalizations, and contact calls. Some of these are mixed with alarm calls with chipmunks or squirrels, which often come into conflict with crows, and vocalizations made by other bird species. The author says that crow language is more like music than a real language, and that crows in different areas have distinctly different and recognizable vocalization patterns.
Crows make a great variety of sounds, the most interesting being the “talking” or “rambling” sounds they make when in communal assemblies, though Westerfield says they can occur when the crow is alone. I've heard these before: they sound exactly like the crow is practicing how to talk. They are highly structured and polysyllabic vocalizations, but their meaning, if any, is totally mysterious.
Last month I discovered that if you play a recording of crow contact calls at half speed, it sounds exactly like a college student saying “Hey! Hey! Hey!” I felt like the guy in that famous Far Side cartoon who invented a canine decoder and became the first human being on Earth to hear what barking dogs are actually saying. Maybe that's all it is. But I suspect in their subtler vocalizations when we're not around they're also saying a lot more.
dec 04, 2016
Most people know the story about luciferase, the protein responsible for bioluminescence. But many people don't realize that luciferase and green fluorescent protein (GFP) work together in the jellyfish Aequorea to amplify the luminescent signal and shift it from blue (460 nm) to green (509 nm). This happens through a process called fluorescence resonance energy transfer, or FRET, which is used every day in biochemistry labs. (The authors actually call it BRET, bioluminescence resonance energy transfer, but it's basically the same thing).
Then there are fireflies. Even though fireflies emit yellow-green light, they don't use GFP. Their luciferin is quite different from the luciferin found in other species. All luminescent beetles use the same chemistry, but different beetles emit different colors because their luciferases are different.
Some dinoflagellates, krill, bacteria, and fungi are also bioluminescent. These simpler creatures use the vitamin riboflavin, along with a long-chain aldehyde, instead of luciferin to produce light. But even some of these simple creatures use FRET and a yellow fluorescent protein to increase the visibility of their flashes. In addition, the bacteria communicate chemically to decide when to produce their luciferase. Hawaiian bobtail squid absorb the bacteria and use their light to make themselves invisible: a type of active camouflage. The pony fish (Leiognathus nuchalis) does the same, and uses fiber optics to control the light.
According to the authors, while the oceans are full of luminescent creatures, there is only one luminous freshwater animal: the snail Latia neritoides, which lives only in the North Island of New Zealand. This one secretes glowing green slime that coats its predators, making them more vulnerable to their own predators. The millipede Motyxia emits light to warn predators that its body is full of cyanide.
This is great stuff to repeat at cocktail parties. The book has beautiful photos of luminescent animals and plants, and explains the light production in a non-technical way that's accessible to anyone with an exposure to basic chemistry and biology.
jun 20, 2014