Before that toddler fell, before Harambe was killed, before the outrage erupted, Harambe was a young gorilla on his way to meet some ladies. In September, 2014, the silverback gorilla, 15 years old at the time, traveled from Brownsville, Texas to the Cincinnati Zoo to meet the female Western Lowland Gorillas Chewie and Mara.

Last week zookeepers shot and killed Harambe because they feared he might hurt a four-year-old boy who slipped into the gorilla's enclosure. As the Internet outrage machine spews and sputters, Harambe’s death clearly means different things to different people. For zookeepers, his sad, unexpected death means a kink in the Gorilla Species Survival Plan.

Lowland gorillas are critically endangered, numbering just 100,000 in the wild. The Gorilla Species Survival Plan carefully manages breeding among the 353 gorillas in accredited US zoos to maintain genetic diversity. Like playing matchmaker in a very, very small town, matching silverbacks to the right troop can get tricky. “It’s like a really complex chess game,” says Kristen Lukas, chair of the Gorilla Species Survival Plan and director of conservation and science at Cleveland Metroparks Zoo.

The Cincinnati Zoo, which has a long track record of breeding gorillas, had planned to let Harambe father baby gorillas when he got a little older, again in accordance with the species survival plan. “It will be a loss to the gene pool of lowland gorillas,” zoo director Thane Maynard said at a press conference this weekend. After Harambe died, the zoo saved and froze his semen, but it's unclear if they'll use it to breed gorillas in the future.

Harambe was born at the Gladys Porter Zoo in Brownsville, Texas in 1999. In the wild, a male silverback leads a troop of several females. And since the ratio of male and female gorillas born are roughly equal, not all males get to lead and breed. Harambe was to be among the lucky few.

When he had gotten old enough to leave his family, facilities director Jerry Stones lobbied for Harambe to lead a troop. “I was positive he would make an excellent troop leader, so I pushed SSP to do it,” he says. Stones remembers Harambe being nurturing even as a youngster. When the zoo introduced a bottle-fed baby gorilla to his troop, his aunt Martha would pick her up each day and bring her to the troop. When Martha got too heavily pregnant to continue that, Harambe brought the baby to her each day.

The Species Survival Plan doesn't just take into account genetics; representatives from the zoos also consider personalities and age. “You have all these people with their individual gorillas, and your head is spinning,” says Lukas. “How can these people know all 350 gorillas? But they do.” The group meets to map out a two-year plan that determines who goes where and who breeds with whom. A typical plan might entail moving a total of ten to 18 gorillas, both male and female, every two years to different zoos.

The bigger and more complex the female relationships in a troop, the more challenging it can be to find the right male. He has to be both unrelated to the females and capable personality-wise. To that end at least, Chewie and Mara, the two females in Harambe's troop in Cincinnati, were two "socially savvy" and slightly older gorillas. The Cincinnati Zoo thought the pair could ease the teenager into adulthood, allowing time to cement those social relationships before he started fathering babies.

The Cincinnati Zoo has another male gorilla, Jomo, who leads a troop of five adult females. But Chewie and Mara no longer have Harambe. "The whole community's hearts go out to Cincinnati Zoo and the Brownsville zoo and anybody who knew or loved Harambe," says Lukas. Whether that troop gets another male and how soon will depend what the Cincinnati zoo wants, though Lukas says she has not heard from the zoo yet. (Cincinnati Zoo representatives did not respond to requests for comment.) Females who know each other well can get just fine without a male around. But if the zoo is to get another male, the whole matchmaking process must start anew.