One of Africa's largest wildlife preserves is marking a year without a single elephant found killed by poachers, which experts have labelled an extraordinary development in an area larger than Switzerland where thousands of the animals have been slaughtered in recent years.

Key points: The apparent turnaround comes after the introduction of rapid intervention police

The apparent turnaround comes after the introduction of rapid intervention police It could take many years for Niassa's elephant population to rebuild to former levels

It could take many years for Niassa's elephant population to rebuild to former levels Aggressive poaching cut elephant numbers from 12,000 to as little as 3,600 in 2016

The apparent turnaround in Niassa Reserve, in a remote region of northern Mozambique, comes after the introduction of a rapid intervention police force and more assertive patrolling and response by air, according to the Wildlife Conservation Society, which manages the reserve with Mozambique's government and several other partners.

Monitoring of the vast reserve with aerial surveys and foot patrols remains incomplete and relies on sampling, however.

And despite the sign of progress, it could take many years for Niassa's elephant population to rebuild to its former levels even if poaching is kept under control.

Aggressive poaching over the years had cut the number of Niassa's elephants from about 12,000 to little over 3,600 in 2016, according to an aerial survey.

Anti-poaching strategies from 2015 to 2017 reduced the number killed but the conservation group called the rate still far too high.

The new interventions have led partners to hope that Niassa's elephants "stand a genuine chance for recovery", the conservation group said.

"It is a remarkable achievement," said James Bampton, country director with the Wildlife Conservation Society.

He said he discovered the year free of poaching deaths while going through data.

An 'important development' that poaching has ceased

The last time an elephant in the Niassa Reserve was recorded killed by a poacher was May 17, 2018, he said.

Political will is a key reason for the success, Mr Bampton added, with Mozambique's president keen to see poaching reduced.

Mr Bampton acknowledged that the low number of remaining elephants was also a factor in the decline in poaching.

A year ago, he estimated that fewer than 2,000 elephants remained in Niassa, though he now says preliminary analysis of data from a survey conducted in October and not yet published indicated about 4,000 elephants are in the reserve.

Still, a year that appears to be free of elephant poaching in the sprawling reserve drew exclamations from some wildlife experts.

"It is a major and very important development that poaching has ceased," George Wittemyer, who chairs the scientific board for the Kenya-based organisation Save the Elephants, said.

"This represents a major success."

The new rapid intervention police force is an elite unit that is better-armed than the reserve's normal rangers and has "a bit of a reputation of being quite hard", Mr Bampton said, adding that no "bad incidents" have been reported in Niassa.

Members of the force are empowered to arrest suspected poachers, put together a case within 72 hours and submit it to the local prosecutor.

African elephant poaching has decline after reaching a peak in 2011. ( Reuters: Siphiwe Sibeko )

African elephant poaching has declined to pre-2008 levels after reaching a peak in 2011, according to the Convention on International Trade in Endangered Species.

But experts say the rate of annual elephant losses still exceeds the birth rate, and the encroachment of human settlements is reducing the animals' range.

Africa's elephant population has plummeted from an estimated several million around 1900 to at least 415,000, according to surveys in recent years.

AP