Covered in dirt and excrement, the pair paced up and down their cramped cages. The stench of putrefying animal carcasses filled the air in this eastern neighbourhood of the war-torn Iraqi city.
Federal forces retook that side of Mosul last month from the Islamic State group after more than two years of tyrannical rule by the jihadist group and weeks of bitter combat.
Until Amir Khalil, a kind of 'roving war zone veterinarian', and his team of volunteers from the Four Paws animal welfare charity visited on Tuesday, nobody had entered the cages in weeks.
"It's very dirty, there is rubble. It is, I believe, inhuman to leave the king of the jungle, or the king of the animals, to be in this place," Khalil told AFP.
A surgical mask covering his face and mouth, he loaded sedative darts into a long blowgun and aimed it at Simba's side.
The sting drew a huge roar from the lion that briefly covered the distant explosions of artillery and air strikes targeting IS on the other bank of the Tigris River.
"When the war started, during the fight, half of the animals were gone. They either got sick and died, or some of them ate the others because of starvation," said Abu Omar, the owner of the small zoo.
"We couldn't even come to feed them. There was shelling and guns firing, and a curfew," he said. "And also, shelling have damaged some of the cages and some animals were killed because of that."
Only Lula, a female bear, and Simba, a male lion, survived. Some pets that used to live at the zoo had found a home with neighbourhood residents, but all the birds of prey have vanished.
The doctor and his aides lifted the sedated lion out of its cage and laid it on a plastic sheet for an examination.
Signup to our newsletter and follow us on Facebook and Twitter!
"During the war there was no food, nobody could reach them. So I feel very emotional to see them. It's heartbreaking," said Hakam Anas al-Zara, a 27-year-old Mosul resident volunteering with Four Paws.
Khalil inspected Simba as a group of giggling children and three intrigued soldiers looked on. Nobody flinched when a large explosion sent blast waves across the neighbourhood and silenced the birds.
It takes more to unsettle this 52-year-old Egyptian-Austrian who has been plying his trade in conflict zones for years to rescue neglected animals in abandoned zoos and elsewhere.
He was already in Iraq in 2003 after the US invasion to rescue nine lions at one of former president Saddam Hussein's palaces in Baghdad.
Khalil also travelled to Egypt and Libya during the upheaval there a few years ago and treated animals during a 2014 conflict in the Gaza Strip at a zoo he described as "the worst in the world."
In Mosul, hundreds of thousands of people face the risk of starvation and being used as human shields by the world's most violent jihadist group, but the vet was adamant animals should also receive attention.
"These animals were kept in captivity because of us. And they don't have the luxury to escape. And they deserve that somebody cares for them," he said.
After Simba, it was Lula's turn and the diagnosis was bad: "We see that the bear has diarrhoea due to nutrition problems, teeth problems, nose excretions."
Four Paws plans to provide food and medication to the animals for a month to give the zoo owner some time to find funds.
Paying to visit a zoo is hardly going to be a priority for residents rebuilding their homes and picking up their lives after jihadist rule. And on the west side of Mosul, the battle to drive out IS has not even started yet.
Abu Omar's male bear is still there, on the other side of the river, and Lula has not seen her partner since the jihadists took over the city in June 2014. "God willing, they will soon be reunited," he said.