Sidebar: Raptor Conservation at
the Zoo
by
Matt Olear
Perhaps the most daunting obstacle faced by Tom Cade and The Peregrine Fund when they first took up the cause of saving the peregrine falcon was the development of techniques to breed falcons in captivity. The difficulty of the task is illustrated by the fact that research into the captive breeding of raptors is still being conducted some 30 years later. By the late 1960s and early 1970s, no one had been able to breed raptors in captivity, and most people thought it was impossible—in large part because many raptors, and the peregrine falcon in particular, conduct elaborate courtship rituals that are not easily replicated in a captive setting. The Peregrine Fund was the first to breed raptors in captivity on a large scale, and the organization’s overwhelming success with peregrines and other birds of prey has set the standard for scientists the world over.
One tool The Peregrine Fund used to successfully breed falcons in captivity was artificial insemination. By inseminating female peregrines with sperm taken from males raised specially as breeders, scientists were able to significantly increase the productivity of their captive stock. About half of The Peregrine Fund’s falcons bred naturally; the others were artificially inseminated. Scientists were able to induce male peregrines to provide sperm through a fascinating process.
Scientists hand-raised males as selected breeders so they would imprint on people rather than on other peregrines and thus would recognize a human as a “sexual” partner. When these falcons reached breeding age, a scientist would imitate some aspects of the birds’ intricate courtship rituals. In peregrines, this includes the passing and sharing of food between partners and ledge displays in which the falcons bow their heads and make soft "ee-chup" sounds. After performing these rituals, the scientist then donned a special hat with rubber tubing around the crown and turned his or her back to the male, as a female peregrine does to initiate copulation. With much noise and flapping of wings, the male follows his instinct and copulates with the hat, which collects the semen in the rubber dam.
Scientists around the world, including the National Zoo’s David Wildt, Steven Monfort, and post-doctoral fellow Juan Manuel Blanco, are now conducting research to develop methods of preserving raptor semen through freezing, a process known as cryopreservation. By banking frozen raptor semen, scientists hope to save and use valuable genes from rare and dwindling populations of raptor species. Individuals of these species often fail to reproduce in captivity for unknown reasons. Artificial insemination can be used to overcome behavioral problems associated with poor breeding.
In September 2001, Wildt presented some of his team’s results on raptor hormones and sperm cryopreservation at the 4th Eurasian Congress on Raptors in Seville, Spain. Among other things, Wildt and his colleagues at the Centro de Estudios de Rapaces Ibericas, near Toledo, Spain, are studying how the sperm of several threatened raptor species are affected by freezing and thawing at various rates and temperatures. They have focused on the Bonelli’s eagle (Hieraaetus fasciatus), booted eagle (Hieraaetus pennatus), golden eagle (Aquila chrysaetos), Spanish imperial eagle (Aquila adalberti), and peregrine falcon. Their research has shown a marked variability in the temperatures and cooling rates the sperm of each species can withstand without suffering damage and reduced fertility. These basic data, along with new information on hormone patterns (measured noninvasively from feces), are already improving the success rate of artificial insemination. Just this past year, Blanco produced his first golden eagle chick through artificial insemination.
According to Wildt, the team has only scratched the
surface of what needs to be learned about the reproductive
biology of the world’s declining raptors. The
group plans to continue studying the relationship between
hormone levels and behavior to identify the best times
to inseminate birds. Also of interest is the affect
of stress on birds brought to the center. Injured birds
that cannot be rehabilitated and released are recruited
into the captive-breeding population, but the majority
of these fail to reproduce. The group hopes that by
measuring stress hormones in feces they can identify
ways to enrich the captive environment and improve reproduction
while increasing animal well-being overall.
ZooGoer 31(6) 2002.
Copyright 2002 Friends of the National Zoo.
All rights reserved.
