The heinous act has been slammed by the Uganda Wildlife Authority, which launched an investigation after the entire pride was found dead at the Queen Elizabeth National Park.
Devastatingly, just 19 lions have been left, prompting warnings of potential extinction by furious experts.
The killings saw immediate calls for “domestic animals” to be banned from the park and for farmers to be compensated to stop future revenge attacks on more lions.
Wildlife boffins also fear lions’ natural prey has become scarce as the number of humans is rising and encroaching on their traditional roaming areas, leading to spats over land.
The Authority told The Independent: “Investigations will confirm the type of poison that was used.
“Investigations should lead to the identification, arrest and prosecution of the people behind this heinous act.”
The killings come weeks after a UN World Wildlife Day pushed its focus on big cats and their efforts to protect them.
The Queen Elizabeth National Park boasts 250 miles and spans the districts of Kasese, Kamwenge, Rubirizi, and Rukungiri.
The reserve is enveloped by the Maramagambo Forest and borders the Kigezi Game Reserve, the Kyambura Game Reserve, and the Kibale National Park in Uganda, and the Virunga National Park in the Democratic Republic of the Congo.
The park is also famous for its volcanic features, including cones and deep craters from which salt is extracted.
It also houses buffalos, hippos, crocodiles, leopards and chimpanzees as well as over 500 bird species.