南アの小規模保護区、ライオンの不妊手術　慎重に繁殖管理

【ホエドスプルートＡＦＰ＝時事】南アフリカ・ホエドスプルートにあるリエトスプルート保護区で、性成熟前の若い雌ライオンに対する不妊手術が行われている。小規模な同保護区内には３頭しかいない、父やおじに当たる雄との交配を防ぐためだ。（写真は南アフリカ・ホエドスプルートにあるリエトスプルート保護区のライオン）
　南ア各地の小規模保護区で暮らすライオンは、合わせて約７００頭。過剰繁殖や近親交配を避けるため、その個体数は慎重に管理する必要がある。
　大規模な保護区であれば、広さは最大１万２０００ヘクタールに及ぶ。ライオンは縄張りを守るために戦い、他の捕食動物とも餌を取り合うため、強い個体だけが生き残る。
　これに対し、５５００ヘクタールのリエトスプルート保護区にいる９頭のライオンが恐れるべきものは無きに等しい。クルーガー国立公園に近い同保護区には、天敵となるハイエナやヒョウ、チーターが少ない。３頭しかいない雄は仲良しの兄弟で、交代で雌と交わる。
　しかし、こうした恵まれた環境で自由にさせておくと、ライオンは続々と繁殖し、保護区内の獲物を食べ尽くした後は、近隣の牧場を狙うことになる。
　リエトスプルートで保護できるライオンは、現時点では９頭が限度だ。このため、母ライオンには避妊処置が施されており、若い娘４頭には不妊手術が行われる。もう１頭の雌も、既に手術を受けている。
　２０１０年、保護団体と各地の小規模保護区の代表らが「南アフリカ・ライオン管理フォーラム」を設立。全区のライオンを「メタ個体群」として共同管理していくためだ。
　同フォーラムでは、５９の保護区に生息する約７００頭のライオンを管理。繁殖率を調整したり、雄を入れ替えたりすることで、自然のプロセスを模倣する。慎重な管理により、このメタ個体群では年２％という維持可能な繁殖率を保っている。
　同フォーラムのサム・フェレイラ代表はＡＦＰに対し、「もし管理をしなければ、個体数は年２２％の割合で増えるだろう」と述べ、「非常に良い話に聞こえるが、問題は、南アフリカにはそれを受け入れられるだけの土地がないということだ」と説明した。
　野生ライオンの個体数は、世界全体で見ると急減しているが、南アフリカには世界の約１７％に当たる約３５００頭が生息しており、さらに増加傾向にある。
　リエトスプルート保護区の代表は「恐らく、小規模保護区では過去３０年間にライオンの個体数は５割増えた」と話している。
　今後も、同保護区の雄が年を取れば他の保護区の若い雄と入れ替えられ、同時に数頭の雌の避妊が解除されることになる。【翻訳編集ＡＦＰＢＢＮｅｗｓ】

〔ＡＦＰ＝時事〕（2021/12/21-12:42）

On the cusp of sexual maturity, a young lioness is about to be sterilised. It's to prevent mating with her father and uncles, the only three wild males on this small South African reserve.
Such parks protect about 700 lions in South Africa alone, but the prides must be carefully managed to avoid overpopulation and in-breeding.
Under natural circumstances, this would not happen because the males would have been displaced by other males, said manager Kevin Leo-Smith, hands on the wheel of an open-topped safari vehicle.
In large reserves, lions roam vast swathes of land, up to 12,000 hectares (30,000 acres).
Only the strongest survive, as prides fight for territory and compete against other predators for food.
Smaller carnivores prey on cubs, and males can maul each other to death.
But the nine lions of Rietspruit game reserve have very little to fear.
Antelope abound on its 5,500-hectares near Kruger National Park, and there are too few hyenas, leopards or cheetahs to pose a threat.
The only three males are inseparable brothers who happily take turns with the females.
The biggest problem is genetic diversity, said Leo-Smith. Lions breed very fast.
Left to their own in such a plentiful setting, they would rapidly multiply, eat through the reserve and then move on to nearby cattle farms.
Nine is all the reserve can accommodate for now.
The lion mother is on birth control, and her four teenage daughters have to be spayed. The remaining older female has already been snipped.
- 'She's big!' -
Wildlife veterinarian Peter Rogers cocks his dart rifle and aims it at the four young lionesses elegantly strewn with their mother in the shade of a tree, bellies bulging with a zebra killed overnight.
He settles on his target and pulls the trigger.
The startled pride grunts and disperses as a red-topped syringe filled with anaesthetic shoots into her neck.
One of her sisters pounces over and swats it to the ground.
Ten minutes later she's fast asleep, unresponsive to her peers' nudges.
Rogers drives up to the tree, shoos away the others and sets to work.
The team moves swiftly, blindfolding the animal to protect her eyes and fitting her with a drip.
They keep an eye on the horizon, as other lions lurk nearby, and heave the 140-kilogramme (300-pound) beast into a white four-wheel drive.
She's big! says one vet, huffing as she slams the boot shut and jumps into the front seat, barely glancing at the sleeping killer behind her.
The vehicle speeds through the reserve, lifting clouds of red dust and unsettling a tower of giraffe browsing treetops.
Two ostriches trail along for a few metres before it turns out the gate and takes the main asphalt road into town.
- 'Meta' population -

The surgery takes almost four hours, complicated by the lioness's swollen intestines.
They had just eaten a zebra so... she had a full stomach. It just made the (operation) a lot more difficult, said Rogers, standing by the enclosure where the animal woke up retching and groggy from the anaesthetic.
It's a very invasive technique, he conceded. But as soon as you have got four fences around a place you have to manage it.
Conservationists and small reserve managers in 2010 set up a forum to manage their wild lions as a meta population.
The Lion Management Forum South Africa (LiMF) oversees around 700 lions among 59 reserves.
They mimic natural processes by controlling reproduction rates and swapping males.
Careful management has allowed the meta population to grow at a sustainable two percent per year.
If we didn't do the management... the population would be increasing at 22 percent per year, LiMF chair Sam Ferreira told AFP.
Now that sounds really nice, but the trouble is we don't have lots of space for that in South Africa.
Globally, wild lions are disappearing fast, but South Africa has an abundant and growing population of around 3,500 -- about 17 percent of the world's total.
Smaller reserves have increased the lion range in the last 30 years probably by 50 percent, said Leo-Smith.
Rietspruit's males will be replaced with younger lions when they age, and then some females will be taken off contraception.
They remain king until then, golden manes framing their faces.
Other reserves will probably still take them when they grow old, said Leo-Smith.
They will be very desirable for photographic reasons.