Many of the melancholy bouquets delivered to the Philadelphia Zoo this week are adorned with little bananas and apples, symbolic gifts to the 23 gorillas and gibbons, lemurs and orangutans that perished on Christmas Eve in the country's worst calamity for zoo animals.
Not quite human, the simian families that perished from a smoky fire have left behind not only an aching grief, but also potentially irreparable holes in the gene pool for the country's primate population.
I cannot think of anything comparable to this loss in North America," said Kevin Willis, a conservation biologist at the American Zoo and Aquarium Association, the agency that will oversee the arduous task of combing the genetic markers of primate populations at other collections to see if replacements can be found for Philadelphia's lost animals.
"Miami lost a lot of birds in Hurricane Andrew, but only one mammal died," Mr. Willis went on. "We lost some valuable birds in St. Louis when a heat lamp melted the insulation, there was a brush fire that ran all the way up to the perimeter fence at the San Diego Zoo a while ago. But nothing has happened like this before."
The lost animals died before dawn on Dec. 24 from the smoke of a smoldering fire in the roof of the World of Primates building. They were among the Philadelphia Zoo's 110 primates, simians that share their taxonomic order with humans.
The zoo's entire family of six gorillas, including a male and two females, which in 1967 were among the last wild-born low-country gorillas to be brought from the wilds into the United States, two of their infants and an unborn fetus, which the zoo counts as an individual, were all lost in the fire.
The smoke also took all three of the zoo's Bornean orangutans, including Rita, an all but irreplaceable wild-born female, all four white-handed gibbons, all six ring-tailed lemurs, both ruffed lemurs and two of six mongoose lemurs.
Replacing these animals, if it can be done, is no longer a matter of safaris into the jungle with nets and cages, as depicted by the British conservationist Gerald Durrell in the 1950's, said Andrew J. Baker, curator of primates and small mammals at the zoo.
To replace their lost primates, the zoo will apply to the Species Survival Program committees of the zoo association, each of which keeps complete genealogical records for an endangered or protected specimen in the United States and Canada. Those designations are set by various international agreements.
The committee records rank each captive animal according to its potential contribution to the gene pool's diversity, with the highest value accorded to wild-born specimens without offspring and the lowest to an animal with many siblings and cousins in collections elsewhere.
Each Species Survival Program committee of zoologists controls the breeding and distribution to insure that the captive population's genetic composition remains as diverse as possible. The system was first developed in 1908, to rebuild the North American buffalo herd from a handful of founders, Mr. Willis noted.
"Ironically, Philadelphia has a new pair of ruffed lemurs from Madagascar already waiting in quarantine, and the pair they lost was going to be sent to the Phoenix Zoo," said Ingrid Porton, a curator at the St. Louis Zoo and the Coordinator, or head, of the Ruffed Lemurs Species Survival Program.
"So the ruffed lemurs Philadelphia lost are already replaced, but I'll have to find another pair for Phoenix now," Dr. Porton said.
The Philadelphia Zoo is the country's oldest, and the loss has evoked grief and remorse among the zookeepers. The zoo has hired counselors from Jewish Family and Children's Services in the city to help the animals keepers, many of whom raised the lost animals from infancy, deal with the loss.
Two security guards at the zoo were suspended on Thursday morning pending investigations into the cause of the fire by the zoo's board and by its staff. The guards smelled smoke at the zoo late on Dec. 23 but did nothing for more than 2 1/2 hours, a spokeswoman for the zoo, Antoinette Maciolek, said.
The guards told fire officials earlier in the week that they had thought the smoke was from a fire at a nearby railroad yard. Fire investigators also faulted improperly installed wiring and smoke alarms that did not work.
The zoo was kept closed over the Christmas week, but will reopen on Tuesday and no admission will be charged for the month as an expression of gratitude for the concern and sympathy of city residents. A memorial exhibit for the animals will be created.
On a purely scientific basis, said Mr. Willis of the zoo association, the loss of the two mongoose lemurs represents the greatest potential depletion of the stock, because only 48 were in captivity in the United States and Canada, and the male was ranked second in terms of genetic scarcity.
There are 248 ruffed lemurs and 403 ring-tailed lemurs in other collections, with many relatives to the ones lost here, so the fire did not represent a great loss for that species, Mr. Willis said.
Not so, he added, for the loss of the three Bornean orangutans, Rita and her daughter Jingga.
"That was an important pair, Mr. Willis said. "They were ranked right at the top. There were 95 of them in North America, so numerically it not as big a loss as the mongoose lemurs, but genetically, this was a terrible loss for the population because the mother was born in the wild."
There are 321 low-land gorillas in the United States and Canada, Mr. Willis went on, so the loss of the loss of the six will not deplete the size of the population unduly, particularly since the three adults had sent four more offspring to the Bronx Zoo and to zoos in Columbus, Washington and San Diego.
Yet, the gorillas were distinct, not just for the place they held as the Philadelphia Zoo's most popular family, but because the group had been so stable, Dr. Baker, the primate curator, said. "They had been together all their lives, with the only additions coming for births," he said.
Zoo personnel are also beginning to measure how long they will feel the sting of loss.
"Its not going to end for us soon," Ms. Maciolek said. "We wait all winter long to hear Rita and Jingga hooting in the trees again, because that means it's spring. We open our windows and say, 'Listen!' That's going to hurt come springtime because they won't be there."
