Or is hippo overpopulation even really the issue?
LUSAKA, Zambia––Why has Zambian tourism minister Charles Banda revived a five-year-old plan to cull up to 250 hippopotamuses per year from South Luangwa National Park, only two years after scrapping it?
“The South Luangwa National Park has a population of more than 13,000 hippos but the area is only ideal for 5,000 hippos,” Banda told media on October 22, 2018. “Moving the hippos to other water bodies would be very expensive. At the moment the only option we have is to do the culling.”
Zambia already promotes hippo hunting
Zambia already promotes trophy hunting of hippos, setting the trophy fee at $3,500, about the same as in neighboring Zimbabwe and the least accessible parts of Namibia, but about half the price for killing a hippo in the rest of Namibia and South Africa.
Thus the proposal to cull hippos in South Luangwa National Park appears to involve more than just an attempt to attract more trophy hunters, as opponents of the cull allege.
But hardly anyone seems persuaded that South Luangwa National Park genuinely has a hippo overpopulation crisis, not least because culling 250 hippos per year––about 2% of the estimated number of hippos in the park, and 1% of the total Luanga River herd––would not even keep up with the rate of hippo reproduction.
20% of the world’s surviving hippos
“The hippo population on the Luangwa River is currently the largest in the world,” conceded Guardian and Mongabay environmental correspondent Jeremy Hance. “The International Union for the Conservation of Nature notes that there may be as many as 42 hippos per square kilometer on the river at its highest density. In fact, around 20% of the world’s surviving hippos are found in this single river — a remarkable conservation achievement by Zambia.
“Currently,” Hance continued, “the IUCN Red List categorizes hippos as vulnerable. With 115,000-130,000 hippos in the world, they are significantly rarer than the African elephant. The hippo’s global population fell during the late 1990s and early 2000s, but has since plateaued. They remain imperiled by ongoing habitat loss and degradation as well as poaching for their meat and ivory — their teeth.
Trophy hunting could accelerate population growth
“If a cull is done,” Hance added, “the next question however is how best to do it. Currently, the Zambia government is outsourcing the cull to trophy hunting outfits,” as is already done with hippos in designated hunting areas.
“The problem with this is that they are also outsourcing which animals are shot,” Hance pointed out.
“Trophy hunters usually want to kill the biggest males possible. In some cases this can lead to catastrophic cascading effects, such as with lions when a male dies and its cubs are killed by rival males. But with hippos the exact opposite may happen: killing a bunch of males could actually lead to an increase in the population in coming years.”
Agreed a 2013 paper by Zambia Wildlife Authority scientist Chansa Chomba, “It has been documented that the act of culling removes excess males and frees resources for the remaining female individuals, leading to increased births and facilitating rather than suppressing population growth rate.”
Hunting mag alleges “dodgy deal” to settle lawsuit
The online periodical Africa Hunting has alleged since July 2018 that the hippo culling proposal “has a dodgy tender process at its core and appears to be an attempt by Zambian Government to cover up a contract-gone-wrong” citing “a source close to the Department of National Parks & Wildlife.”
According to the unidentified Africa Hunting source, the Zambian Department of National Parks & Wildlife “was sued by Mabwe Adventures Limited, the hunting company contracted to execute the cull [in 2016]. A recent court ruling in the Mabwe’s favor fueled the Department’s sudden backtracking on its 2016 anti-cull decision in order to avoid paying compensation.”
Banda “confirmed that a contract entered into with Mabwe Adventures in 2015 was still valid,” Africa Hunting said, going on to describe the arrangements in detail.
“The Luangwa Valley is not overpopulated as they claim,” Zambian Green Party president Peter Sinkamba told the Lusaka Times. “The hippo population in that conservation area has dwindled by about 14-20% in the last 20 years.
“In any case, Luangwa Valley is not the only game park in Zambia,” Sinkamba reminded Lusaka Times readers. We have about 20 National Game Parks and over 30 game reserves. In fact, most, if not all the parks require restocking. A serious environmentally-conscious government would have opted for relocation than culling. We must take a leaf from the Republics of Kenya and Tanzania that relocate their animals when conditions dictate.
“The culling policy is motivated by pure greed,” Sinkamba finished.
Born Free: no “robust scientific evidence”
The British-based Born Free Foundation, having led the 2016 campaign against the proposed hippo cull, argues that the Zambian government “has, to date, failed to provide robust, scientific evidence demonstrating that there is an overpopulation of hippos in the Luangwa River,” or that “previous hippo culls in the Luangwa Valley have been successful in reducing the hippo population over the long-term.”
The Born Free Foundation further argues that the Zambian government “has failed to provide data showing that river levels and water flow in the Luangwa River are abnormally low and cannot sustain the current hippo population,” or that “an indiscriminate hippo cull would prevent a future outbreak of anthrax,” a disease that often kills hippos, along with other African wildlife and domestic livestock, and has been mentioned as a rationale for culling.
Let hippos migrate?
If the South Luangwa National Park hippo population has actually reached carrying capacity, the options for control and stabilization are limited. Just allowing the hippos to expand their habitat downstream, into other wildlife areas, sounds easy, but hippos along the way would be moving through agricultural areas.
While hippos tend to remain submerged in rivers and lakes by day, they wander as far as five or six miles on their nocturnal foraging expeditions, raiding crops and sometimes killing people who encounter them unawares. Thus allowing hippos to migrate on their own is a politically unviable option.
Translocating hippos, as Sinkamba recommends, can be done, but is logistically more difficult than even moving elephants, and as Banda points out, expensive.
Are there other options besides culling?
Hippo birth control research
The late Jay F. Kirkpatrick (1940-2015), founder of the Science & Conservation Center at ZooMontana, as editor of Proceedings of the Fifth International Symposium on Fertility Control in Wildlife, in 2002 published a presentation by University of Guelph researcher Laura H. Graham on “Ovarian function in the Nile hippopotamus and the effects of Depo-Provera administration.”
Depo-Provera works to contracept captive hippos, Graham found, but administration is difficult, and a dose remains effective for only about 100 days.
Kirkpatrick subsequently developed a version of the wildlife contraceptive PZP for hippos. It is produced to order by the ZooMontana Science & Conservation Center.
Hard to inject
“We have a few zoos contracepting hippos and it does work in hippos, but it is very difficult to get a good intramuscular injection,” ZooMontana Science & Conservation Center director Kimberly M. Frank confirmed to ANIMALS 24-7.
“The recommendation for hippos is every three months in the caudal fold, or any other not so fatty area, so darting is really not going to work,” Frank added.
The caudal fold is below the tail, a region of the body––in any species––often hit accidentally by hunters who shoot just as the target animal whirls to run away.
But even if trophy hunters could be hired to dart hippos with PZP instead of killing them to mount their big heads on walls, merely hitting the hippo in the right part of the hindquarters is only just the beginning of successful PZP administration.
Crocodiles keep their distance
A PZP dart also has to penetrate the hippo’s thick hide and a fat layer worthy of a seat in Congress, cleanly enough to administer the drug without inflicting a wound that can easily become infected.
Just getting close enough to a wild hippo to deliver a PZP dart would be a considerable feat. Most hippos spend most of their time in water, in herds. Most hippos tend to stomp whoever disturbs them.
For this reason, while most hippos share their habitat with big Nile crocodiles, the crocodiles tend to keep their distance.
Yet another contraceptive that could potentially work in hippos is GonaCon, developed and registered for use in a variety of species by USDA Wildlife Services, but USDA Wildlife Services is not authorized to manufacture and sell it.
The Oklahoma-based organization SpayFirst! several years ago acquired the rights to make and sell GonaCon, and has for more than five years worked to perfect the procedures for using GonaCon in dogs. But SpayFirst! director Ruth Steinberger told ANIMALS 24-7 that she is unaware of any investigation so far of the use of GonaCon in hippos.
Assuming GonaCon can be used to contracept hippos, whether it could be administered to wild hippos any more easily than Depo-Provera or PZP is anyone’s guess.
Have wild hippos been vaccinated?
Vaccinating wild hippos against anthrax involves similar difficulties, but may have been done at least once. Logistic details, however, do not appear to have been published.
Specifically, the agriculture and environment ministries of Namibia in April 2018 media releases claimed to have used vaccination to contain an outbreak of anthrax in the western part of Bwabwata National Park in the Kavango East Region, bordering Angola, Botswana, and Zambia.
Discovered in October 2017, the outbreak reportedly killed about 120 hippopotamuses and 25 Cape buffalo, as well as hundreds of domestic livestock.
Namibian government announcements said that 3,000 cattle, 1,010 goats, and 216 wild animals had been vaccinated to quell the outbreak, but did not say which wild animals were vaccinated or how.
“Vaccinating 216 hippos and Cape buffaloes would have been exciting,” commented Program for Monitoring Emerging Diseases moderator Martin Hugh Jones, a professor emeritus at Louisiana State University who is regarded as one of the world’s leading experts on anthrax.
But if vaccinating hippos in the wild has in fact been done successfully, contracepting hippos in the wild may yet become possible.