One of Cecil the lion's cub has been killed by a rival male triggering fears that the survivors may only have days to live.

The much-loved lion was slaughtered by American dentist Walter Palmer last month, sparking outrage around the world.

Now a further tragedy has befallen the pride after one of his cubs was killed by another male as he attempted to mate with its mother. And without a pride leader to protect them, locals fear that the remaining cubs could have just days left to live.

Scroll down for video

Father's cubs: Cecil the lion with his offspring before he was cruelly killed by an American dentist

Cecil's pride: A couple of Cecil's cubs relaxing in the Hwange national park back in 2012. One of his cubs has now been tragically killed by a rival lion

Experts had warned the trophy shooting of Cecil could trigger a 'cascade of deaths' as cubs are typically killed by the next lion in the hierarchy so he could father his own offspring with the females in the pride.

Local guides had given the pride - originally made up of three lionesses and now just seven cubs – just a five per cent chance of survival after solitary males were spotted prowling nearby their former den in Hwange National Park.

Hopes were raised when it appeared that the new pride leader - Cecil's brother Jericho - appeared to be looking after the cubs.

Many were relieved after a team at Oxford University's Wildlife Conservation Unit, which had been studying Cecil before he was shot dead, said the lion's brother had stepped in to safeguard the young.

Tragically, it was not to last and after local sources confirmed the cubs had now been abandoned by Jericho.

Now it appears a rival male has taken advantage of the unprotected pride to try and mate with one of the females - killing one if his competitor's offspring.

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.'

The much-loved lion was killed by American dentist Walter Palmer last month, sparking outrage around the world

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.'

A source at the Zimbabwe park told the Sunday Mirror that the small pride's three 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.

The news is likely to spark further fury towards Palmer who has been in hiding since reports of the shooting broke last month.

Since then, campaigners have protested outside his dentist surgery while he has even received death threats amid growing anger over the protected animal's slaughter.

Tributes to the butchered lion have poured in thousands of miles away at Dr Walter Palmer's office in Bloomington, Minnesota, where protesters dressed as 'dentist hunters' also threw stuffed lions at his house.

Celebrities including models Cara Delevingne and Candice Swanepoel have also blasted the dentist, calling him a 'poor excuse of a human being'.

The head of the pride Cecil was shot by Minnesota dentist Palmer, who paid £35,000 to shoot the 13-year-old lion on 1 July.

Palmer has admitted killing the 13-year-old predator, who was fitted with a GPS collar as part of the Oxford University study.

But he said in a statement he had hired professional guides and believed all the necessary hunting permits were in order.

He has not been sighted since his identity was revealed by Zimbabwean conservationists earlier this week.

Zimbabwe today called for Palmer to be extradited from the United States after accusing him of killing the much-loved animal illegally.

Environment minister Oppah Muchinguri said the dentist should be handed over to Zimbabwean officials to face justice, adding that she understood prosecutors had started the legal process to make that happen.

Referring to the 55-year-old trophy hunter from Minnesota as a 'foreign poacher', she said: 'We are appealing to the responsible authorities for his extradition to Zimbabwe so that he can be made accountable for his illegal actions.'

Brutal: Cecil the lion (right) fights with a rival male in May last year. Since his death, there have been fears that his cubs would be killed by a rival male

Cecil the lion (right, darker mane) fighting with a rival lion on safari at the Ngweshla Picnic site at the Hwange National Park in Zimbabwe

Muchinguri also said Palmer's use of a bow and arrow to kill the lion, who is said to have been lured out of Hwange National Park with bait before being shot, was 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.

Zimbabwean police are also hunting for Palmer who is believed to have returned to the US.

The dentist has since apologised for killing Cecil, claiming he thought the hunt was legal.

Since their pride leader's death, the pack has fled their former den at Ngweshla and have been hiding behind a water pan known as Kennedy Two.

The source said the female had been forced to stay on the run to avoid the advances of rival males but warned that the cubs would struggle to keep up.

'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.'

Jericho is now said to have taken over a different pride and is unlikely to attack his brother's cubs - some of which he may believe are his now.

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

Hunter: Palmer had is now under investigation after he admitted killing the lion (not pictured) in Zimbabwe this month

Sadly, they are not expected to survive past the age of three, when they are typically named by researchers.

Professional Zimbabwean hunter Theo Bronkhorst insisted he did nothing wrong on the hunt that killed Cecil the lion, telling AFP he was shocked to find the animal was wearing a tracking collar.

'I don't believe I failed in any duties at all, I was engaged by a client to do a hunt for him and we shot an old male lion that I believed was past his breeding age. I don't think that I've done anything wrong,' Bronkhorst said

He said: 'Both I and the client were extremely devastated that this thing had a collar on because at no time did we see a collar on this lion prior to shooting it.

'We were devastated... I left the collar there at the bait site and unfortunately that was stupid of me and negligent of me.'

Bronkhorst was granted bail by the Hwange court on Wednesday after being charged with 'failing to prevent an illegal hunt' when he led the expedition in early July.

Palmer, a life-long big game hunter, managed to return to the United States before the authorities were aware of the controversy around Cecil's death.

'It was too late to apprehend the foreign poacher because he had already absconded to his country of origin,' Muchinguri said.

Safe from harm: Cecil the lion's adorable cubs were being cared for by their late father's pride in Zimbabwe until recently

Sleeping soundly: The infant lions have since been abandoned by their uncle Jericho and one has been killed by a rival

The killing has sparked social media outrage against Palmer in the United States.

The White House said yesterday it would review a public petition of more than 100,000 signatures to have him extradited.

Safari Club International (SCI), which promotes big-game hunting and has about 55,000 members worldwide, has since issued a statement saying Dr Palmer and Mr Bronkhorst's memberships will be suspended and that it wants a 'full and thorough investigation'.

The club said: 'Those who intentionally take wildlife illegally should be prosecuted and punished to the maximum extent allowed by law.'

The dentist is a specialist bow and arrow hunter and has 43 registered kills on the SCI website.

And as his troubles escalate, even the PR firm that Dr Palmer hired to help him deal with the media firestorm has deserted him.

The company, which specialises in 'crisis and issue management, special situations, transactions and transitions' has said they no longer represent the dentist and said another, as-yet unidentified firm had taken on his case.

The much loved big cat was wounded by an arrow after he was allegedly lured out of the national park by the hunter's bait.

After tracking the injured beast, Cecil was eventually found and shot dead. His corpse was then skinned and the head hacked off as a trophy.

Dr Palmer said he was unaware of Cecil's fame and expressed regret but denied any illegality and laid any blame firmly at the door of his guides.

Protests outside his dental practice have escalated and he has advised his patients to go elsewhere for treatment.

Explaining that he was a 'life long hunter' who refrained from talking about his passion because he is aware of the deep passions it stirs, Dr Palmer said that he was sorry his dental practice had closed.

He expressed regret that he killed Cecil because he did not know about the lion's protected status.