When you hear the word “kangaroo,” you probably think about those big, clownish marsupials that hop around Australia and carry their young in pouches on their bellies.
Well there’s a lesser-known group of kangaroos that most people don’t know about. They’re called tree kangaroos. These smaller, arboreal kangaroos live in the rainforests of Australia and New Guinea. Some of them—there are about a dozen species—look quite similar to ‘roos on the ground. Others look more like fuzzy bears with long tails.
Almost all are threatened with extinction.
Case in point, Australia’s Lumholtz's tree kangaroo (Dendrolagus lumholtzi). These little guys—they average six or seven kilograms and measure about 60 centimeters from head to toe—live in the rapidly disappearing coastal rainforests of Queensland. The species has already lost much of its native habitat to development and agriculture, leaving populations in fragmented, unprotected pockets, mostly located on private land where the animals are more likely to encounter humans. All too frequently the tree kangaroos are killed when they descend from the trees to the ground to move between food trees. Many are struck by cars. More are attacked by pet dogs or feral canines (some of which have hybridized with dingoes).
More recently a new threat has emerged: drought. Recent reports from Queensland suggest that many tree kangaroos there are dying or otherwise suffering from the state’s extreme lack of rain over the past three years. Exactly why they’re dying is a mystery but some conservationists believe that the drought has increased the natural toxicity of some of the leaves the tree-kangaroos often eat. The animals eat a wide range of native plants, some of which have mild toxicity, but they have also been observed eating more dangerous invasive plants such as lantana and wild tobacco.
The toxicity, wherever it comes from, apparently doesn’t kill the animals immediately. First it blinds them. The Tree Roo Rescue and Conservation Centre recently told Queensland’s 9 News that blindness has been on the rise for the past three years and that nine of the 10 tree kangaroos being cared for at their facility were blind or visually impaired.
To help protect the species in the long run, a Queensland zoo called Dreamworld has started a Lumholtz’s tree kangaroo captive-breeding program. They just had one problem: They couldn’t get the ‘roos to reproduce.
Enter The University of Queensland reproductive biologist Tamara Keeley. It became her job to figure out what was going on.
Her tool for doing that? Poop.
Dreamworld started collecting fecal samples from a female named Mindy early in 2014. Next, Keeley tested the samples, looking for fecal progesterone metabolite concentrations that could be used to determine Mindy’s estrous cycle.
The data, at first, looked odd. “Initially her estrous cycles were occurring at an interval much longer than ever reported for any tree kangaroo species,” Keeley says. Tree kangaroos aren’t well studied, so there’s not a lot of information to go on, but Mindy’s cycles appeared to be about 90 days apart, 30 percent longer than had been observed in other individuals. This periodicity constrained successful mating to a very narrow window. Even though behavioral signs indicated that she was receptive to mating and did mate with a male, pregnancy did not occur.
The researchers kept looking. More tests after that first failed mating showed that her cycle had normalized to about 60 days. “Confirmation of ovulation using the fecal progesterone metabolite levels allowed us to predict the next potential window for her to mate again,” Keeley says. “The keepers used this advice to pair her again.”
This time mating was successful. A pouch check 45 days later revealed a tiny joey had, indeed, been born.
Flash forward to last week when the joey, head poking out of Mindy’s pouch (see it below), was revealed to the world. It will spend a total of six months in the pouch until it is big enough and strong enough venture out on its own.
Keeley says the poop test—something that’s been used with many other animals—could be of use as a technique for monitoring species in the wild without capturing them and taking blood or tissue samples. That’s especially valuable for studying tree kangaroos because they are nocturnal and easily startled.
Dreamworld’s small collection of Lumholtz’s tree kangaroos won’t be enough to save the species if the wild population continues to crash. Mindy probably won’t breed again for another year, and her joey won’t reach sexual maturity for about two years. Still, this is a start, and it is good news for a species that is likely to face greater losses in the wild in the near future.
Photos courtesy of Dreamworld