On Saturday, animals at the Oakland Zoo will suspend their diet plans and indulge in what could easily be this year’s largest animal party, feasting on servings of produce donated by Oakland residents, many of whom will come and watch the animals eat their hearts out between 9 am and 3 pm.

Dubbed “Feast for the Beasts,” Saturday’s party will allow members of the public to bring vegetables for the sanctuary’s devout vegetarians in the herbivore section and get a chance to watch zookeepers feed them.

Due to the vast biodiversity at the zoo, the larger cats and elephants will have meals worth tens of thousands of calories, while for those on the lower rungs of the food chain in the amphibian and invertebrate section, a binge meal may only register in the double digits.

Feast for the Beasts is expected to bring in enough food to last the zoo’s party of over 700 animals a few meals, although zookeepers caution that bringing too much could lead to waste. The event is an opportunity for the public to learn more about the animals while also contributing to the supply of readily available produce for them.

It costs the Oakland Zoo at least $800 to feed the animals each day— almost $315,000 a year—meaning that the produce brought by residents tomorrow may save the non-profit establishment a little cash, depending on how long it lasts.

The cost of feeding animals “actually varies a little bit seasonally because some animals eat more or during different times of the year,” said Zoological Manager Margaret Rousser. “For example, the alligators go on a self-imposed fast from November to February every year.”

A tiger at the Oakland Zoo, for example, eats $16,000 worth of food a year, nearly $1,300 a month, according to Rousser. Each day, keepers feed the tiger 10 bones at an annual cost of $3,978, at least 10 pounds of chicken parts at an annual cost of $2,883, and 17 pounds of meat three times a week at an annual cost of $3,580.

At least once each week, the tiger expects 17 pounds of turkey meat, which costs the zoo $2 per pound, or $1,768 each year. As a snack, the tiger gets five rabbits once a week, and for this special delicacy, the zoo foots a $1,560 annual bill.

Asked what they had planned for those animals that may have been watching their weight since the end of the winter, zoo spokesperson Nicky Mora said the annual feast has been known to spur even the most conservative of elephants into bouts of gourmandism. From the 11,000 pound bull elephant that eats 100 pounds of “browse,” or vegetation, each day, to the smallest animals in the sanctuary, zoologists keep a detailed log of each animal’s weight, adjusting dietary plans and introducing more incentives for physical exercise whenever an animal seems to be losing gaining too much weight.

“All animals are managed in such a way that we try to maintain healthy weights,” Rousser said. “This means that some of them get seasonal adjustments. All of them are weighed regularly so that we can catch weight gain or loss early, before it becomes a problem.”

Rousser said the animals have a range of what keepers consider a normal weight for each species, but individual animals will have their own fluctuations in body weight that may be seasonal, especially in the case of squirrel monkeys.

“Male squirrel monkeys nearly double in weight right before and during breeding season, but go back to normal in the off season,” Rousser said. “It is the keeper’s responsibility to weigh each animal regularly and request changes to the diets based on those weights. All diet changes must be approved by the area manager, a veterinarian, and the curator before being implemented.”

For animals that won’t stop eating, keepers have developed a system to encourage them to remain active by implementing “enrichment devices,” through which they increase feeding time without increasing food amounts, meaning the animals have to work more for the same amount of food. The squirrel monkeys, for instance, get much of their daytime rations in the form of treats handed out by the zookeeper, rather than just having the food deposited into trays.

Feast for the Beasts comes just a week after the Oakland Zoo announced the birth of over 200 new animals, including squirrel monkey Pythagoras, a newborn reticulated giraffe Maggi, and over newly hatched 200 milk frogs.

Mora said a must-see event for Saturday, especially for kids, is the “teddy bear check-up,” during which keepers inspect stuffed animals brought in by kids, teaching kids some basic veterinary procedures like checking heartbeat, pulse and body temperature.

Visitors will also be able to see the elephants eat the produce donated by the public. “The biggest highlight for eating will be at the elephant exhibit. The elephants pick up entire watermelons and crunch on them,” said Mora. “It’s so cool to see.”

A complete feeding list from 9:45 am t0 3:30 pm can be found here. More information about the event, as well as a list of foods the public is invited to bring for the animals, is here.