Laura Read, chief executive of Marwell Wildlife, said teams were working “around the clock” to find Samba.
Tango, another nine-month-old capybara, escaped at the same time but was found nearby – and the hope is that Samba will still be discovered around the zoo.
“We do think she probably is still quite close by,” said Read. “We’re not ruling out the fact she may have come back.”
She said the animal was not at risk from predators but urged drivers in the area to take care, particularly at night.
She added: “What she’ll probably do is find somewhere she feels safe and secure, potentially by a water body, and hunker down.”