December 20, 2005
Observatory
A Dog's Best Friend in Stormy Weather
By HENRY FOUNTAIN
A dog may be man's best friend, but for help in coping with stress, a dog's best friend may be another dog.
That's one finding of a study that measured stress levels in dogs that become anxious during thunderstorms. The study, by Nancy A. Dreschel and Douglas A. Granger of Penn State, showed that what an owner did to try to calm a dog had no effect, either positive or negative, on the animal's stress level. But dogs that lived in households with other dogs recovered faster from such stressful situations.
"There's been this thought that people make their dogs anxious," said Dr. Dreschel, an instructor in the department of dairy and animal science. "What we showed was that it didn't matter whether they were touching them or not touching them."
Dr. Dreschel became interested in studying stress in dogs during the 13 years she spent as a practicing veterinarian. "I saw a lot of dogs that had thunderstorm phobia," she said. Storm-phobic dogs pace, whine and hide under furniture, and in extreme cases can destroy furnishings or injure themselves.
Dr. Dreschel also set out to show that levels of a hormone, cortisol, in a dog's saliva could be used to measure stress, and that testing could be done relatively easily. Her experiments were conducted in dog owners' homes, and saliva was obtained simply by having owners hold small pieces of cotton rope in the dogs' mouths at 20-minute intervals. The owners' cortisol levels were also measured.
She tested the dogs by playing a five-minute recording of a storm and videotaping their reactions. In all, 19 storm-phobic dogs were tested, including 5 golden retrievers and 5 herding-type dogs.
All the dogs except one displayed signs of anxiety (the one that didn't, a small mixed-breed, fell asleep on its owner's couch). Cortisol levels rose markedly, but they increased less and fell back to normal faster in dogs that lived with other dogs.
Based on her experiences as a veterinarian, Dr. Dreschel said, she expected to see an effect on the dogs' owners as well.
But the owners' hormone levels stayed the same. That might be because the owners knew that the thunderstorm was not real and the recording would soon be over. If so, though, "the dogs weren't picking up from the owner that this was something not to be afraid of," Dr. Dreschel said.
The Long and Short of Dinosaurs
Imagine, if you can, a basketball team made up of five Tyrannosaurus rexes. On the one hand, such a team would be highly entertaining (they could easily dunk over Shaq, for one thing), but on the other, there would be something innately boring about them. They would all be about the same size.
That's because dinosaurs are thought to have grown fast and steadily, so that they reached a fairly standard size as adults, less influenced by variables like diet and climate. Modern reptiles, by contrast, grow relatively slowly, and adult sizes can vary based on local conditions. If there is a lot of food, for example, growth will speed up.
But paleontologists at the University of Bonn have discovered that one dinosaur, Plateosaurus englehardti, was more like a reptile. Studying growth rings in large bones of the dinosaur, the researchers found that the animals went through periods of slow and fast growth. Their report is published in the journal Science.
Plateosaurus lived about 200 million years ago in what is now Central Europe. With a usual length of 30 feet or more, they were among the earliest large dinosaurs (and probably could have held their own in a pickup game against a bunch of T. rexes, had they existed at the same time).
When an animal grows rapidly, the rings in its bones tend to be wider. When growth slows down, the rings get narrower. The researchers found varying wide and narrow rings, indicating nonuniform growth over the years.
Different growth rates also mean that the animals reach their full size at different times. Some of the dinosaurs the researchers studied reached full size at 12, while others were found to be still growing at 27. And full size varied: while most adults were about 30 feet long, others were barely half that.
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