This is the incredible moment a fearless baby deer takes on a two-tonne rhino in a real-life David and Goliath showdown.

Amusing footage shows Mundzak, a Chinese muntjac deer, butting heads with a seemingly unbeatable opponent, Marusia, a female rhinoceros, inside their shared enclosure at Wroclaw Zoo in Poland.

Moments later, the tiny animal charged and chased the beast across the enclosure, showing remarkable courage despite their size difference.

The pair even butted heads but Mundzak was unfazed and continued his pursuit of the bigger opponent.

Zookeepers explained that Mundzak's aggressive behaviour was driven by excess testosterone, as his female partner is in heat.

A zoo spokesman said: 'He needs to release his energy and show who's boss – even if his sparring partner weighs 1.7 tonnes. Who would have thought that such a warrior could be hidden in that tiny body?'

Officials added that Marusia is a greater one-horned Indian rhino, born in 2014 in Plzen, Czechia, and arrived from Touroparc Zoo in France in 2019.

A pair of Chinese muntjacs has lived in the Terai pavilion since 2012, when the Asian fauna exhibit opened. The zoo said Marusia shares her enclosure with gibbons and the muntjacs, using separate off-exhibit areas but sharing the outdoor space.

Zookeepers described Marusia as gentle and aware of her size, treating the encounter as play, while Mundzak was serious in his attempt to defend territory.