For wild animal lovers not content with watching tigers and gorillas during the day, a growing number of zoos are offering a more thrilling after-dark experience — overnight stays.
From Philadelphia to Denver, nocturnal visitors are learning what happens when the gates slam shut, the sun goes down and the moon rises over some of America's most well-known zoos.
"You get the zoo to yourself," said Jennifer Labows of the Philadelphia Zoo, which is America's first zoo and home to more than 1,300 animals.
"It is a unique experience for guests to see the animals at night."
The Philadelphia Zoo has been running its Roars and Snores Overnight Programs for about 20 years. The most popular theme program is the Night Flight Overnight Program where children aged five to 12 sleep in the zoo's tree house.
The overnight stays are not only popular with young children. Teen programs are offered at many zoos for those young adults interested in the zoo industry. They are also a favorite venue for birthday sleepovers, family trips and with scout troops.
"We customize the overnight to whatever badge the scouts are trying to complete that night," Labows said.
Most overnight stays include a night tour during which youngsters experience the mysterious sights and unusual sounds of the zoo without the usual distractions. A midnight snack and breakfast are also served.
"It is a unique experience to be at the zoo without the crowds and additional noise," explained Tracey Patterson, of the Denver Zoo, which has been running its Bunk with the Beasts program since 1998.
With nearly 4,000 animals and 700 species, the zoo attracts more than 1.8 million visitors a year.
"The things you hear and see in the zoo are completely different," said Patterson.
On Denver's two-hour tours, night vision scopes are provided so guests can see nocturnal animals such as owls, and indoor educational games enhance the learning experience.
Guests at the new overnight program at the Wildlife Conservation Society's Queens Zoo in New York make breakfast treats for parrots, bears, pigs, pumas and coyotes, and watch the keepers feed them to the animals the next morning, said Education Curator Tom Hurtubise.
With visitors at the Denver Zoo coming from as far away as Wyoming and Montana, Patterson said parents tend to be more worried about leaving their children than the children themselves. They have rarely had to call up a parent in the middle of the night.
"They love it," Patterson said about the children. "For many, it's their first overnight away from home. They are so excited that by the end of the day they are so tired that they have no opportunity to worry."
The growing popularity of overnights has prompted zoos that only cater to day-time visitors to think again. The Queens Zoo, which started their program this year, is so pleased with its success they want to continue it next year.
The profits from the overnight programs are used to improve other parts of the facility. At the Philadelphia Zoo, their programs cost up to $60 per person. Any profits go into their overall operating budget.
Patterson said prices for the Denver Zoo overnight program range from $45 to $65 per person depending on the group and program.
The newer programs, such as the one at the Queens Zoo, tend to be smaller and suited for families more interested in a more intimate experience. With only 36 people at their last weekend, the price tag came to $75 per person for Wildlife Conservative Society members and an additional $10 for non-members.
"The only problem was that the parents didn't realize the parrots could be so loud at 3:30 in the morning," Hurtubise said.