Dave McFarland, a safari operator and coordinator of the new "Feed Mana" operation said "We saw four calves that never made it (in the last 10 days)."
"There's just nothing for these animals to eat. It's unbelievable."
Precise figures of animal deaths are hard to tally because of the vast distances within the 2,000 km squared park, which is popular with local and international tourists.
Zimbabwe, as with much of southern Africa, has seen less rainfall than usual this year. More than five million people, a third of the country's population, will need food aid before the next harvest is due in April.
Elephants are suffering too, particularly the youngest. Herds are fracturing as parents try to protect their young.
"They've all split up as individuals and the mothers walk with a calf 200 meters behind them on this hard journey, just looking for food," said McFarland. "Sometimes the calves lag behind too far and they get lost, the mothers can't find them, it's not good."
Five orphaned elephant calves have so far been rescued in the park and taken to a rehabilitation centre in Harare.
Volunteers and local donors working under the "Feed Mana" banner, which include the Veterinarians for Animal Welfare Zimbabwe, have over the past few weeks delivered around 9,000 bales of hay to the game park on the back of 30-tonne trucks.
With rains still 6-8 weeks away, elephants and other game have now congregated on a 40 kilometres squared flood plain in Mana, where there is still some grazing left.
Elephants are also starving in Hwange, the national park in the west of the country made famous by Cecil the Lion in 2015.
The Bhejane Trust, a conservation group that works in Hwange, has recorded broken elephant tusks near water holes. That could indicate that fights have broken out between big bulls over scarce water in the pans.
Water does not occur naturally in Hwange and needs to be artificially pumped into troughs and pans dotted around the park, which is seven times the size of Mana Pools.
But the park's 50,000-strong elephant population is putting pressure on scarce resources, said Trevor Lane of the Bhejane Trust, which helps to maintain the pumps. Elephants from Botswana are crossing over too to look for scarce water.