Stares and stripes: Can you tell how many zebras are in this photograph? You'll need to look very closely...

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Prepare to go cross-eyed over one photographer's mind-boggling optical illusion snap - as no one is sure how many zebras this image actually contains.

Retired mechanical engineer Robert Holmwood captured the gaggle of Burchell's zebra at the Kruger National Park in his native South Africa during one of the worst droughts in living memory.

And the 64-year-old, who retired two years ago, said everyone who views the confusing image has a different opinion on just how many zebras there are in the frame.

The gaggle of zebras in the Kruger National Park in South Africa - but can you tell how many animals are in the photograph?

Robert said: 'Zebras are gregarious by nature and normally move in herds. It was the coincidental positioning of the herd individuals that created the striped illusion and confusion as to the exact numbers present.

'I was both amused and amazed at the reaction to my photograph. I was amused at how many people posted guesses as to how many animals are depicted in the photograph. The guesses varied between four and seven.

'By sharing the photograph I intended to stimulate some thought on the reason for zebra's stripes - specifically the theory it confuses predators when they are in the herd.

'Images bring humour to the general public and the guesses on the number of zebras in this photograph were many and varied - even from humans with colour vision. Predators evidently see less colour than humans.

'Excluding the numerous guesses at how many zebras are depicted, there were other interesting comments. One retort to the question 'how many zebras do you see?' was 'all of them'.

'The riddle of why they have stripes has puzzled scientists for years. Five main hypotheses for stripes are to repel insects, to provide camouflage through some optical illusion, to confuse predators, to reduce body temperature or to help the animals recognise each other.'

Robert, who worked as an engineer in the mining industry, had always been interested in wildlife and has rekindled his passion for photography during his retirement.

He and his wife enjoy visiting Africa's game parks and combine spotting animals with snapping pictures.

Robert's image of the herd grazing on drought-ravaged veldt grass was taken in the early morning and did not take long to capture.

And while guesses on how many of the striped creatures feature in the frame have ranged up to seven, Robert said there are actually only four zebras which can be spotted in the photo.

South African photographer Robert Holmwood has had people guessing anything from four to seven after looking at the snap

He said: 'This image was taken early in the morning. In the wild, early morning is the best time as game is more active and the natural sunlight is the best for good images. We not only stop to observe predators, but all game, to observe their interesting behaviour.

'With feeding herds, they are always on the move and unpredictable in their movements. You need to make the most of the opportunity when it presents itself.

'I enjoy both photography and nature. Being retired, we can spend time in game parks and fulfil the passion for photographing and observing animals in their natural wild state.

'Taking a good photograph gives me a sense of satisfaction and I find wildlife photography very rewarding in a personal sense.'