In the early 1970s, wildlife biologists made history by attaching bulky radio collars to grizzly bears in Montana, polar bears in the Arctic and great pandas in China.
By tracking the radio beeps on foot and by air, they were able to gain insight into the animals' habits and habitats.
Now wildlife biologists are poised to make history again; the miniaturization of microcomputer technology has turned cumbersome equipment into devices so light that they can be epoxied onto the tail feather of a tiny bird.
In coming years, some predict, the transmitters may become light enough to be attached to the back of a bee.
And instead of following along on foot, biologists are beginning to rely on satellites to track animals, even those that wing their way along vast migratory routes.
Although the earlier techniques were useful only in tracking an animal's location, the improvements--in a field known as biotelemetry--have made it possible to measure the range of life's forces.
Today, the radio transmitters can measure blood pressure and pH, stress levels, body temperature, sleep cycles and even the exact moment a female ovulates.
"The window is opening on a new era for wildlife conservation," said Michael Hutchins of the American Assn. of Zoological Parks and Aquariums in Bethesda, Md.
"From what we now see, biotelemetry will almost certainly pave the way for the intensive management of wild animals that is going to be necessary to save endangered species as their critical habitat becomes threatened."
In that effort, biotelemetric devices are being used with increasing frequency for conservation, from monitoring the Kemp's ridley turtle as it migrates off the coast of Long Island, N.Y., to keeping current on the habits of the Puerto Rican crested toad, whose habitat has been reduced to a single parking lot near San Juan, where it is being threatened by a paving truck.
Both have been fitted with specially designed harnesses that contain the satellite transmitters.
The devices may one day be used to help with breeding and may even open the door to artificial insemination of animals in the wild, particularly those that live in fragmented pockets of wilderness and are threatened by inbreeding.
One such breeding experiment under way by the New York Zoological Society's Biotelemetry Studies Laboratory involves fitting transmitters in the gaur (rhymes with hour), a species of African cattle. These can be used to measure minute temperature variation over the course of the menstrual cycle. A small spike in the temperature chart signals ovulation. That's important because if a male and female are put together before the female is in heat, the male often gores her.
Some believe the devices may help sustain wild animals even as the world's wilderness areas become compressed into what biologists increasingly refer to as "mega-zoos."
"Someday we may see that a female of a species in the wild will have to be artificially inseminated with the sperm from another male that lives hundreds of miles away in another habitat," Hutchins said.
Biotelemetry--from the Greek words for life, distance and measure--literally means measuring life forces from far away. Or as Fred Koontz of the New York Zoological Society's biotelemetry lab describes it, "We take it to mean no wires."
The Zoological Society is planning to make biotelemetry a cornerstone in its $100-million Wildlife Crisis Campaign, a new fund-raising effort.
"Our role as a zoo is evolving," Koontz said of the biotelemetry laboratory, which was opened with a special grant from the Institute of Museum Services last fall and was developed with the assistance of two of the zoo's veterinarians, Robert Cook and William Karesh.
"We are using our collection (of animals) for research and development, to develop new tools to explore wildlife biology that will help both the zoo community and the in-nature community."
Koontz's involvement with the new biotelemetry began recently, when the zoo's curator of birds, Chris Sheppard, told him she was having difficulty trying to incubate eggs taken from the nests of captive white-naped cranes, a bird that is seriously endangered in the wild.
If the eggs could be taken from the nests and hatched in an incubator, the birds would then nest several times, thereby increasing by as much as five times the number of chicks hatched per season. The extra birds could be used to supplement the wild populations.
But although nearly 90% of the cranes' eggs hatch when left in the nest, the results drop to as low as 50% in the incubator.
Sheppard asked Koontz if he knew of a way to accurately measure the temperature and humidity of an active nest, as well as to record how often the cranes turn the egg with their beaks, to see if the incubator was anywhere near the ideal conditions.
The old method, said Koontz, would have required sticking temperature probes inside the nest, which is sometimes a hazard to the birds and can produce unreliable data. It also requires the 24-hour attention of a researcher from a staff that is already overextended.
Koontz came up with a solution: a biotelemetrical egg.
Working with epoxy and a plastic Easter egg, Koontz's cousin, Dr. George Stetten--who works with radio transmitters as a hobby--fashioned something that looks like a crane egg in size, weight and color.
Inside the egg, a battery-operated transmitter measures the temperature and humidity of the nest at seven locations, and a position sensor records how many times the egg is moved. The results are fed into a computer for instant processing.
To Koontz's surprise, the data showed that the egg under a brooding crane is nearly 10 degrees Celsius warmer at the top than at the bottom, a gradient that may be vital to what is called "hatchability."
The group is planning to track the forest elephant, a dwindling subspecies of the African elephant that has rarely been studied because of the ease with which it can disappear into the jungle.
In the coming months, six of the animals in a national park in Cameroon will be fitted with radio transmitters strong enough to beam a signal to a passing satellite controlled by the National Oceanic and Atmospheric Administration. The Navstar Global Positioning System, as it is called, is derived from military research.
"No one has ever really studied the forest elephant before because they were too difficult to track," Koontz said.
With biotelemetry, their day has come.