Cooling boost for wildlife as heat blankets country

Kay, an Auckland Zoo giraffe, savours a giant iceblock. Picture / Greg Bowker

A water-cooling system has been cranked up for the sharks at Kelly Tarlton's Underwater World - and the giraffes at Auckland Zoo have been given carrot iceblocks to nibble as hot, humid weather blankets the country.

Kelly Tarlton's operations manager Andrew Baker said the sharks had adjusted their behaviour as the seawater flowing into tanks at its Tamaki Drive site edged up to an average of 23C over the past week.

The sharks are swimming in water between 22C and 23C, slightly above the 20C regarded as optimum.

"The sharks' response has been to eat slightly less and swim a bit slower than usual," Mr Baker said.

Staff had increased water-cooling operations - from a system used for the Antarctic Encounter attraction - by an extra 50 per cent to keep sharks, stingrays and other marine life happy.

"With the waters so warm outside right now, this is a critical function and we're having to use more electricity," Mr Baker said.

National Institute of Water and Atmospheric Research meteorologist Georgina Griffiths said that although a sea temperature of close to 23C was not unusual for this time of year, the ocean had warmed rapidly after summer's slow start.

Although the average sea temperature around Auckland is between 21C and 22C at this time of year, in late January at Leigh, north of Auckland, the ocean was still a chilly 15C.

"From around 15C at Leigh at the start of January it had hit 20C by the end of that month and that was a big rise in just over two weeks," she said.

At Auckland Zoo, staff fed the giraffes giant iceblocks with grated carrot frozen inside while the parrots and emus got a hose-down to help them to cope with the heat.

Nisha the Sumatran tiger simply lay in the shade but the zoo's reptiles became more active.

The subtropical air mass covering much of New Zealand saw temperatures soar in the South Island yesterday. Christchurch reached 29C and a severe thunderstorm hit Dunedin in the evening, blowing the roof off a house and causing surface flooding in the city.

Auckland and Wellington reached 24C but humidity at times climbed to more than 90 per cent.

The moist, northeast flow covering New Zealand is forecast to move away from today, bringing drier weather, but rain is forecast to return by Friday with a northwesterly flow.

Cold-blooded killers

* All sharks are ectothermic (cold blooded), which means that their body temperature depends on that of the surrounding water.

* Some fast-swimming sharks such as the great white and mako shark have higher body temperatures than the surrounding water.

* Kelly Tarlton's has school sharks, sevengills, Wobbegongs and bronze whalers.