We are propagating 13 of the most preferred Eucalyptus species, including Eucalyptus camaldulensis, Eucalyptus puntata, Eucalyptus rudis, and Eucalyptus robusta. A majority of theses species are not commonly available for purchase from nurseries, so that’s why we start the seeds in a greenhouse nursery. The seeds are sown in “conetainers,” which are long cylindrical containers that slide into trays. These specific containers allow the trees to establish good root development without the circling that occurs in some shallower pots. Each tray holds 200 containers that can be moved around and grouped together as the seeds germinate.The containers are first filled with a light propagation mix soil. Then the small Eucalyptus seeds are sprinkled on the surface of the soil. Finally, a layer of sand is added to cover the seeds, and they are watered in and misted once a day. The seeds germinate pretty readily; the ones sown on June 22 were already sprouting just six days later. The seedlings are now being transitioned from the greenhouse to a protected area in the nursery. Once the seedlings are large enough, they will be shifted to a larger container called a treepot (containers that are longer than they are wide). By spring 2010, the babies should be able to leave the nursery and settle into their new home at the browse farm. It will take several more years before browse will be able to be harvested from these new seedlings.
The San Diego Zoo has the largest koala population (11 currently at the Zoo, plus a dozen more on loan to other zoos) and the most successful koala breeding program outside of Australia. We were the first zoo in the United States to welcome a koala joey. The San Diego Zoo is fortunate to have such an ideal climate for growing fresh Eucalyptus for the koalas, because they eat a lot of it! Koalas eat about 1 to 1.5 pounds (454 to 680 grams) of leaves each day, which doesn’t include the several species they are offered but might not eat. Eucalyptus leaves are poisonous to most animals, but koalas have special bacteria in their stomachs that break down the toxic oils. Special cheek teeth grind the tough leaves. Koalas don’t get many calories from their diet, but they conserve energy by moving slowly and by sleeping as much as 20 hours each day.
The San Diego Zoo received its first two koalas, Snugglepot and Cuddlepie, in 1925, as a gift from the children of Sydney, Australia, to the children of San Diego. Koalas have few natural predators, although sometimes a dingo or large owl can take one. The most common direct causes of koala deaths are from motor vehicles and dogs. So they are definitely safest high up in trees. In the past, koalas were killed for their coats. In fact, from 1919 to 1924, eight million koalas were killed. Today, the koala is threatened by predation by domestic dogs and by a disease that has spread through most of the population. Unfortunately, some koalas get run over by cars. But the one thing that koalas and other wildlife can’t protect themselves against is the loss of their habitat. A combination of cooperative managed-care propagation programs, research, and support for habitat conservation projects continue to ensure the survival of koalas.
Christy Powell is a plant propagator at the San Diego Zoo.
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