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Application of
PZP to Wildlife
Wild Horses
The vaccine has been used successfully to manage the wild
horse population of Assateague Island National Seashore under
the sponsorship and authority of the National Park Service
(NPS). The population has been treated for 16 years without
health problems, and the population has decreased slightly
since management-level application began in 1995 (from 173-to
165). Wild horses are also being treated on Cape Lookout National
Seashore (the Shackleford Banks) for the NPS, on Carrot Island,
on the Rachel Carson National Estuarine Reserve, in NC, on
Little Cumberland Island, GA (private), at Return to Freedom
Wild Horse Sanctuary, CA, and on theLittle Book Cliff National
Wild Horse Range, CO, Pryor Mountain National Wild Horse Range,
MT and on many areas of Nevada, for the Bureau of Land Management
(BLM). In addition to controlling the horse population on
Assateague Island, treatment has extended the lives and improved
the health condition of older mares, by removing the stresses
of pregnancy and lactation (see Kirkpatrick 1995; Kirkpatrick
and Turner 2002, 2003; Kirkpatrick et al. 1990, 1991, 1992,
1995a,1996a,b,1997; Liu et al. 1989; Turner et al. 1996a,
1997, 2001, 2002)
Zoo Animals
In order to prevent the production of "surplus"
animals, more than 112 species of zoo animals in more than
100 zoos have been treated with PZP. Thus far PZP has shown
contraceptive effects in more than 40 of these species, and
the results for the remainder will be clear after larger numbers
of animals have been treated. In all probability, PZP will
prove to contracept just about all mammalian species, excepting
some carnivores. For example, it works in bears but not in
felids and canids. We do note differences between species
in the size of dose necessary and the timing of the booster
inoculations. Porcine Zona Pellucida vaccine is now a standard
recommendation for many species by the Contraceptive Advisory
Group of the American Zoo and Aquarium Association (AZA).
The obvious advantage of the PZP vaccine for zoo animals is
that it can be administered without the stresses of restraint
(see Frisbie and Kirkpatrick 1998; Kirkpatrick et al. 1992b,
1995b).
Deer
The PZP vaccine was shown to block pregnancies in captive
white-tailed deer as early as 1990. Since that time, numerous
projects have been mounted with free-roaming deer in MD, NJ,
NY, CT, WA, VA and OH. The two largest projects are on Fire
Island National Seashore, NY, where approximately 215 deer
are treated annually over a 6 year period, and on the campus
of the National Institute of Standards and Technology, in
MD, where more than 150 deer have been treated over a 8 year
period. Studies and projects thus far have shown that contraception
with PZP will often extend the breeding season of the female
by one to two months, but that the energy cost is far less
than that of getting pregnant and nursing. Although they will
often follow the treated female deer, males do not carry on
fights or expend additional energy beyond the normal breeding
season (see Deigert et al. 2003; McShea et al. 1997; Turner
et al. 1992, 1995, 1996, 1997; Naugle et al. 2002; Rutberg
et al. 2004).
African Elephants
In order to eliminate the need to legally kill elephants in
African national parks to prevent rapid population increases,
the PZP vaccine has been tested in African elephants in The
Kruger National Park in South Africa. The vaccine was very
successful and the results paralleled those of horse contraception.
One of the most important findings was that the vaccine caused
no changes in the social behaviors of family groups or harassment
of cycling females by bulls. At least two other African nations
are interested in pursuing elephant contraception and new
projects are being planned (see Fayer-Hosken et al. 1999,
2000; Delsink et al. 2002).
Other Species
The PZP vaccine has also been used successfully in feral water
buffalo inhabiting the U.S. Naval Base in Guam, feral burros
in Virgin Islands National Park, (Turner et al. 1996b), Elk
on Point Reyes National Seashore (CA) (Shideler et al. 2002).
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