Giving back to nature

CONSERVATION

Giving back to nature

When done in a considered and informed way, human intervention can help animals survive and thrive.

WORDS Stephanie Convery

ILLUSTRATIONS Phil Constantinesco

The Crucifix Frog only mates during a rainstorm. The tiny, bright yellow amphibian – named for the multicoloured spots that speckle its back in the shape of a cross – lives most of its life underground, wrapped in a protective cocoon and burrowed in the soil of semi-arid floodplains. Until the rain comes, that is. Heavy downpours in their habitat – in south-western Queensland and northern New South Wales – flood the frogs’ desert burrows and rouse them from slumber, whereupon they shed their protective cocoons and head to the surface. There, they’ll feast on bugs and worms swimming in the temporary pools of rainwater – and find a companion frog to spend some quality time with.

Breeding Crucifix Frogs in captivity, however, has proven a challenge. How to recreate the rainstorm conditions that encourage the frogs to mate? At Melbourne Zoo, the Crucifix Frog population had remained stubbornly celibate until a friend suggested to keeper Raelene Hobbs that, rather than wait for an actual thunderstorm, she try playing the frogs an audio recording of a storm instead. She found a 10-hour YouTube track of a tempest and left it on for the frogs overnight. And before long, Raelene had three clutches of eggs. Humankind has been the cause of so much environmental trauma and loss, it’s easy to think that all people have been able to do when it comes to the natural world is wreck things. But with continued research, intervention can assist species under threat and save potentially critical populations in the wild. Positive human

POSITIVE INTERVENTION

intervention can be something as simple as planting a tree or constructing a fence around a wildlife reserve to keep out feral predators; or it can be as complex as developing a captive breeding program. Insurance programs are a particular form of breeding program focused on ensuring the survival of some of the most critically endangered species in Australia, says Dr Kim Miller, Life Sciences Manager, Conservation and Research, at Zoos Victoria. “The intention with an insurance population is that you have enough duplication of the wild population that if the species went completely extinct in the wild, the captive population would be demographically and genetically robust enough to start the whole population again.” But they’re not the only kind of breeding program targeted at maintaining wild populations of endangered species. The critically endangered Helmeted Honeyeater, a bright yellow passerine (song bird), is only found in one place in the wild: in narrow scraps of swampy stream-side forest along Woori Yallock, Cockatoo and Sheep Station creeks, about 45km east of Melbourne. The area has been a nature reserve since the 1960s, thanks to birding groups that noticed a marked decline in Helmeted Honeyeater numbers and lobbied the government for the conservation of its habitat. The establishment of what is now called Yellingbo Nature Conservation Reserve is one of the key reasons the bird survives in the wild today. Unfortunately, this remnant habitat is very limited – a particularly bad thing for birds as territorial as the Helmeted Honeyeater in breeding season – and degraded in some parts of the reserve. As a consequence, volunteers trek out there every single day to feed the birds. This supplementary feeding program isn’t the birds’ only source of food, but such human intervention is necessary for their survival. “There’s a lot of work going on to improve the habitat at Yellingbo,” says Craig Whiteford, Zoos Victoria’s General Manager, Threatened Species. And it’s not just habitat. Melbourne Water has undertaken work on the drainage

If we believe animals have the right to exist and that biodiversity is a goal, then there’s a role for captive breeding and for putting effort into it.

CRAIG WHITEFORD / GENERAL MANAGER, THREATENED SPECIES, ZOOS VICTORIA

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and water quality; Zoos Victoria has partnered with geneticists at La Trobe and Monash universities to help with a breeding program; and the community group, Friends of the Helmeted Honeyeater, coordinates tree planting programs. The population of Helmeted Honeyeaters is very small and vulnerable, consisting of approximately 200 birds. This figure actually represents huge strides towards the bird’s recovery; at its most critical, there were as few as 50 Helmeted Honeyeaters in the wild. The increase in numbers is thanks to a very carefully constructed captive breeding program run out of Healesville Sanctuary since 1989. “The remaining habitat doesn’t have capacity to support a large population of birds,” says Kim. “It requires a large amount of intervention. Because of the small population size, there are ongoing problems where you have occasional events of inbreeding, but what’s more common is that in a really small population over a long period of time, you lose genetic diversity.” The lack of genetic diversity compounds over generations of birds, culminating in far fewer birds hatching and, ultimately, population decline. One of the ways Helmeted Honeyeaters maintain a natural level of genetic diversity in the wild is through interbreeding with a closely related subspecies, the Yellow-tufted Honeyeater. Kim explains that these ‘migrant’ interbreeding events ought to occur about four times in every bird’s generation. They haven’t happened in the wild for a long time, most likely due to habitat fragmentation. The reserve at Yellingbo is surrounded by farmland, isolating it from other honeyeaters’ habitats. So, one of the key strategies for restoring that genetic diversity is a technique called genetic rescue. “What we do is take Yellow-tufted Honeyeaters from populations around Victoria that are no longer able to cross over with Helmeted Honeyeaters’ territory, and we breed those Yellow-tufted Honeyeaters with the Helmeted Honeyeaters here at the Sanctuary,” says Kim. The offspring of those birds are then released into the wild. “That mimics the natural migration of Yellow-tufted Honeyeaters into the population, and we can do it in such a way that we know just how much of that genetic material is being passed into the population.” This year, Healesville Sanctuary coordinated a release of 14 birds at the beginning of autumn, after the breeding season had ended. The onset of the coronavirus (COVID-19) pandemic and statewide lockdown added an extra logistical challenge to this year’s release and meant that Healesville Sanctuary staff who had bred the birds couldn’t be there when the boxes were opened. Nevertheless, the release went smoothly and the newly released birds are still being seen regularly about the reserve. The key thing researchers will be looking for, though, is how many of the released birds participate in breeding this spring – thereby working some of their diverse genetic material into the population at large. “The Helmeted Honeyeater program is quite unique in that we know the individual breeding history of almost every bird in the wild population and we have genetic samples of almost every bird from the last several decades,” says Kim. “We have more robust information than almost any other animal, and that’s because of the significant investment in research on this bird.” “We have to be judicial about intervening,” says Craig. “If we believe that animals have the right to exist and that biodiversity is a goal, then there’s a role for captive breeding and for putting effort into it.”

Support Zoos Victoria’s efforts to save the Helmeted Honeyeater by purchasing a Totes for Wildlife tote bag. For every tote sold, a tree will be planted for the Helmeted Honeyeater. Buy a tote at any of our zoos or online: zoo.org.au/totes-for-wildlife

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Contact Heather Kiley Relationship Manager Philanthropy 0408 515 380 | hkiley@zoo.org.au