Cecil the lion: One of Cecil's cubs killed by rival male

It is feared that one of Cecil the lion's cubs has been killed by a rival male.

The 13-year-old lion was illegally killed by trophy hunter Walter Palmer in Zimbabwe last month, prompting global outrage.

The killing of Cecil also sparked concerns for the potentially devastating repercussions for the cubs and tragically, the fears seem to have been confirmed.

The Mail Online reports that one of the cubs was killed by another male as he attempted to mate with its mother.

Cecil's remaining cubs were seen following along after the three lionesses in the Hwange National Park earlier this week.

A source at the Zimbabwe park told the Sunday Mirror that the small pride's lionesses had attempted to fight off the invading lion's advances, but warned that the big cats would not be able to protect the cubs for much longer.

"Sadly, the cubs are too young to trek over much distance," he told the Daily Mirror. "The females must become nomadic and keep running. The cubs only have a five per cent chance of survival. It is a disaster."

Cubs are typically killed by the next lion in the hierarchy who fathers his own offspring with the females in the pride.

It was hoped that Cecil's brother Jericho might step in and protect the cubs, however sources claim that he has now abandoned them, leaving them unprotected and vulnerable to attack.

Experts have warned that the remaining cubs too could have just days left to live.

Research project leader David Macdonald said: "The natural law in lion society is that when a male dies and his weakened coalition is usurped, the new incoming males kill their predecessors' cubs."

Macdonald had warned earlier this week that Cecil's death could lead to a 'cascade of other deaths'.

He said: "At a personal level as I have watched this lion... and gloried in his magnificence and beauty. I was very deeply saddened by this. To the extent that it was illegal it was completely reprehensible. But I hope that some good might come out of it in terms of raising the profile of lion conservation around the world."

Minnesota dentist Walter Palmer paid £35,000 to kill Cecil, the head of the pride, on 1 July.

The 55-year-old has been in hiding ever since and had been the focus of death threats and angry protests outside his dental practice.

He issued a statement stating that he "deeply regrets" the killing, but insisted he did not believe the hunt was illegal, adding that he had hired professional guides and believed all the necessary hunting permits were in order.

There have been calls for Palmer to be extradited from the United States to face the penalty for the illegal killing of the much-loved lion, who was lured out of Hwange National Park with bait before being shot, in contravention of Zimbabwean hunting regulations.

Two other men arrested for their part in the hunt -Theo Bronkhorst and Honest Ndlovu - appeared in court last month charged with poaching offences. Bronkhorst was granted bail by the Hwange court on Wednesday (29 July) after being charged with "failing to prevent an illegal hunt". If convicted, he faces a fine of $20,000 and up to 10 years in jail, according to Reuters.

Meanwhile, the PR firm that Dr Palmer hired to help him deal with the media onslaught following the killings has also deserted him.

The company, which specialises in 'crisis and issue management, special situations, transactions and transitions', has said they no longer represent the dentist.

Animal rights campaigners, celebrities and members of the public joined the public outcry decrying the brutal killing. Cara Delevingne, Ricky Gervais, Jimmy Kimmel, Mia Farrow, Kristin Davis, Judd Apatow, Debra Messing, Juliette Lewis and Virginia McKenna of the Born Free Foundation, were among the celebrities leading the furious response to the heartless killing.

Animal rights group PETA have condemned the brutal killings and have launched a petition demanding a ban on trophy hunting.