Vaccine that curbs jumbo population explosionComment on this story
COOPED up behind a wall of fences and human obstacles, Africa’s elephants have become more dependent on the will of man to determine whether they live or die – or get to breed.
There are some herds that still enjoy limited freedom in parts of the continent, but most of the SA elephants are trapped within finite boundaries of parks.
So, it is a matter of time before their population levels reach saturation point.
At some point, their numbers will reach levels which will force wildlife managers to reduce them.
In Kruger National Park, almost 17 000 elephants were shot between 1967 and 1995, when a moratorium on culling was put in place.
However, in 2008, the government re-opened the door to culling as the option of last resort to manage the increase in the park’s population.
Other options included shifting elephants to other public or private parks, or indirect methods such as reducing the number of artificial waterholes.
These were unlikely to offer much relief in the long-term.
Hunting or sterilisation could also work, but raised a whole set of ethical and political problems.
This made contraception an increasingly attractive option for several elephant managers, especially in smaller reserves where it is easier to identify individual elephant cows.
The conundrum of how to control elephant populations was just one of the issues facing ecologists and wildlife managers from 40 countries who gathered in Durban last week at the International Wildlife Management Congress.
Among the delegates were researchers involved in an ambitious elephant contraception project funded by the Human Society International.
The researchers have been busy for 15 years and believe they have demonstrated that immuno-contraception is an effective technique to control elephant population growth.
Their conclusion was based on results after “vaccinating” hundreds of elephant cows in 14 game reserves with a non-hormonal contraceptive developed from pig eggs.
Known as porcine zona pellucida (PZP), the technique is based on the same principle as disease prevention through vaccination.
The PZP vaccine, which is extracted from the outer layer of pig eggs, has been found to block reproduction by preventing sperm from penetrating mammal eggs.
The first PZP birth control experiments were done on wild horses on an island in the US and have been used on deer, buffalo and other mammals in several parts of the world.
In SA, the first PZP experiments began on elephants in Kruger National Park in 1996, with field trials showing success rates of between 56 and 80 percent, according to Audrey Delsink, an elephant ecologist and field director of the PZP project.
Since then, the project has been refined to a point where PZP has demonstrated an effectiveness of between 95 to 100 percent in preventing elephant pregnancies.
In KwaZulu-Natal, the vaccine is being used to control elephant numbers in the Tembe Elephant Park, along with the Phinda-Munyawana and Thanda private game reserves.
The Tembe elephant population has risen from about 80 in 1983 to more than 250 today, putting a strain on the park’s rare sand forest.
Ultimately, park managers in the 30 000 hectare reserve hope to drop the fences with neighbouring Mozambique so that the Tembe herd can migrate freely and join a similar-sized herd in the Maputo Elephant Park.
But until that happens, PZP has to help limit elephant numbers.
Delsink says the vaccine has also been used in Makalali private game reserve in Limpopo for the last 12 years to keep the population at about 70 animals.
Makalali warden Ross Kettles described the PZP project as a “resounding success” as well as the “least invasive and most humane” population control method.
In the reserve, the vaccine is administered only after cows have borne at least one calf.
“Due to the complex social structure of elephant societies and the important role that calves play in this society, it was never our objective to stop population growth, but rather to slow growth to a manageable target.”
Delsink says one of the major advantages of PZP is that the contraception is reversible if the treatment is discontinued and does not result in permanent sterilisation.
“After 16 years of investigation there has been no empirical data of harmful behavioural effects,” she told the congress.
One of biggest drawbacks, however, is the cost of treating cows on a regular basis.
To administer the vaccine, the PZP contraceptive is shot into the animal’s backside using a dart gun, either from the ground or from a helicopter.
Laboratory project head Professor Henk Bertschinger of the University of Pretoria says animals have to be darted three times during the first year of treatment (a primary vaccination followed by two booster shots).
Thereafter, a single booster is needed every year to maintain the contraceptive effect – although a new one-stop inoculation is being developed to reduce the number of dartings.
JJ van Altena, who manages the PZP darting project, believes that contraception for much larger elephant groups is now “definitely within reach”, especially with the development of a longer-lasting vaccination. “From the air, you can vaccinate a herd in a matter of five minutes or so.
“With the success demonstrated so far, the challenge of large populations is simply a matter of scaling up the efforts and resources,” says Van Altena.
All the same, managing a contraceptive programme in a 2 million hectare park such as Kruger could be hugely expensive and present major logistical challenges in darting up to 5 000 elephant cows every year.
At the moment, the first year of treatment alone stands at between R800 and R1 500 an animal (much of which is made up of helicopter costs but could be reduced significantly for large organisations like SanParks, which have their own helicopters and crews).
Although pilot trials were conducted in Kruger from 1996-2000, SanParks managers still appear to be wary about rolling out PZP on a large scale.
Eight years ago, SanParks came up with an estimate of R1.4 million a year to administer PZP to 75 percent of the breeding cows in Kruger, noting that similar costs could be expected every year thereafter.
“At this time it is not even certain that such an exercise, due to its complexity, is logistically feasible,” a senior SanParks researcher said at the time.
From a financial perspective, cash-strapped park managers might also find it more profitable to return to the old policy of culling elephants.
A separate study conducted in Kruger about a decade ago suggested that SanParks could realise at least R5.2m in profit from selling the meat and skins alone from 800 culled elephants a year.
This excludes potentially much larger profits from selling elephant ivory (which is still largely banned, with the exception of occasional once-off sales).