The Whooping Crane(Grus americanus) | 
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The Whooping Crane(Grus americanus) |
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The Whooper's name was inspired by its loud, distinctive call, audible up to two miles away! This breathtaking bugle is created by resonance in the bird's 5-foot-long trachea (half of which is looped within the keel of the breastbone). Cranes call to communicate danger, to defend territory, and to reinforce pair bonds.
The History of the Whooping Crane in North America
Biologists estimate that there were between 700 and 1,400 Whoopers alive in 1865. Their numbers dropped rapidly, however, and by 1890 the Whooping Crane had disappeared from the heart of its breeding range in the north central United States. By 1938, only two small flocks remained - one non-migratory flock in southwest Louisiana, and one migratory flock that nested in Canada and wintered in Texas.
By the winter of 1941-42, the migratory flock had dwindled to only 13 adult birds and 2 juveniles. Meanwhile, the Louisiana population was reduced from 13 to 6 birds following a severe storm in 1940. One by one, the remaining Louisiana birds disappeared, until Mac, the sole survivor, was captured in 1950. Shortly after his transport and release in Texas, however, Mac was attacked by local Whoopers defending their territory, and was later found dead.
The precarious status of the Whooping Crane prompted biologists to propose safeguarding the species through captive breeding. Beginning in 1967, eggs from the Arkansas/Wood Buffalo flock were collected by biologists and used to establish captive populations and support experimental releases.
Captive breeding began to pay dividends in 1975, when Whoopers at the U.S. National Biological Service's Patuxent Wildlife Research Center (near Laurel, Maryland) first produced eggs of their own. Artificial insemination helped increase fertility of eggs, while Sandhill Cranes were used as surrogate incubators to improve the hatching success of the Whooper eggs.
In 1989, Patuxent transferred 22 Whooping Cranes to the International Crane Foundation (ICF) in Baraboo, Wisconsin. Splitting the captive population between two locations reduced the chance that a single catastrophic storm or disease outbreak could wipe out the whole flock. As of early 1999, Patuxent's flock numbered 44, and ICF had 29. The breeding center at the Calgary Zoo had 21, the White Oak Conservation Center in Florida had two.
Experience has shown that Whooping Cranes do not breed successfully in captivity. Scientists are unsure as to whether this is due to a behavioral change when living in captivity, the lack of an environmental cue, or some completely unknown factor. In any case, scientists have taken to artificially inseminating whooping crane eggs to increase the whooping crane flocks. Results from the initial attempts using the semen from one male were not good.
Later experiments showed that an acceptable rate of egg fertility could be obtained by artificially inseminating the eggs with a mixture of semen from many potential fathers. This, however, presents one small problem if a mixture of semen from different potential fathers is used, just who is the real father?
This dilemma can be easily solved using molecular biology techniques. DNA samples from the offspring, the mother, and the potential fathers are taken and digested with restriction enzymes, creating different sized pieces of DNA. The exact size of all of the DNA fragments created by the digest is unique to each individual. This is known as a "DNA fingerprint."
Since the DNA of a child is a combination of the DNA contributions from its mother and father, the offspring's DNA fingerprint will have characteristics of both parents. We can use these similarities to determine paternity.
When the DNA digests are run on a gel, bands of DNA will form based upon the size of the DNA fragments. The smaller the band, the farther it will move on the gel. All of the bands produced by the offspring must have been obtained from either the mother, the father, or from both. When we run our gels, we will be looking at the bands produced by the offspring, the mother, and the potential fathers. Only a band which is unique to the offspring and only one father is useful in determining paternity.