Stories By Multilocus

The Northern Corroboree Frog in the Brindabella Ranges

Northern Corroboree Frog, Tidbinbilla Nature Reserve.

The Northern Corroboree Frog is listed as Endangered and is found as two genetically different populations, one in the Fiery Ranges in Kosciuszko National Park and the other in the Brindabella Ranges in Namadgi National Park.

In the late 1970s when I began bushwalking in the Brindabella Ranges I was told stories of how at certain times of the year you could see large numbers of Northern Corroboree Frogs sunning themselves in the subalpine sphagnum bogs. However, I was never fortunate enough to see one.

Following droughts in the 1980’s the population of the Northern Corroboree Frog in the Brindabella Ranges was observed to be declining so the ACT Government began monitoring their numbers. These annual surveys confirmed the downward trend with a major population crash being observed in 2002.

It was not known what was causing this decline but it was suspected one major contributor was Chytrid (pronounced ‘Kit-rid) fungus, which attacks the skin of frogs eventually killing them.

The Northern Corroboree Frog has a very slow reproductive rate taking five years to reach breeding age and then only laying 25 eggs a year. This combination along with the ongoing drought and Chytrid fungus gave a very poor prognosis. Without intervention all the evidence was the Brindabella Northern Corroboree Frog would be extinct within the next 3 to 10 years.

In late 2002 the decision was made to bring the species into captivity by collecting their eggs and raising the tadpoles and frogs at Tidbinbilla Nature Reserve. This captively raised colony would then be used as a source of frogs to boost the size of the wild population. The first egg collection was scheduled for April 2003.

On January 18, 2003, a major firestorm swept through Kosciuszko and Namadgi National Parks devastating the frog’s habitat. All expectations were this would be the last straw for the species and another textbook example of species extinction. In this case Chytrid and drought reducing the population to very low numbers which is then wiped out by a random unpredictable event, in this instance, a firestorm.

However, much to everyone’s relief, surveys in the months following the fire revealed small numbers of calling Northern Corroboree Frogs. The GPS location of each frog was marked and in April rangers returned to look for and collect the eggs. In that year nearly 200 eggs were collected. In the following years 50% of the known eggs were collected. By 2005 there were more Northern Corroboree Frogs in captivity than there were estimated to be in the wild.

With this in mind, in 2006 I was invited to be a guest on a three-day pilot eco tour, which gave a behind the scenes look at the Northern Corroboree Frog captive raising program. Since first hearing about the frog 35 years ago I was going to see the collecting of the eggs and possibly one of the few remaining frogs left in the wild.

This was when I began to follow and document their story.

In 2006 the emphasis was on maintaining the captively raised colony with rangers collecting eggs each year to increase the numbers in the facility at Tidbinbilla. Although attempts had been made at other institutions, no one had been able to breed the species and its related cousin the Southern Corroboree Frog in captivity.

When I interviewed staff in 2007 the prognosis was still very grim as it was clear that without the ability to breed the species in captivity it was still likely to become extinct.

In 2007 when the frogs, first collected as eggs in 2003, were reaching 4 years old the decision was made to trial different environmental strategies in an attempt to get them to breed. The frogs were still one year from breeding age so the emphasis was on creating and testing the different environmental conditions into which the frogs would be placed in 2009. To everyone’s surprise the 4-year-old frogs began to call and at the end of the trial ’breeding season’ they had produced 300 viable eggs, which hatched into tadpoles. By chance Tidbinbilla had found the right conditions to breed the frogs in captivity. In 2009 the breeding program was ramped up successfully producing close to 900 eggs.

The future was looking good, the program had progressed from captive rearing to a ‘survival assurance’ colony. This meant that if the wild population became extinct Tidbinbilla had the option to reintroduce the animals back into the wild.

Disaster struck in December 2009 when the refrigeration unit managing the temperature in the facility holding the 300 frogs and 700 tadpoles, from the last two years of breeding, failed, killing all the animals inside. This devastating news was broadcast all around the world. Luckily all the breeding stock recovered from the wild since 2003 were safe in a separate facility. This was a major emotional setback and the breeding had to commence all over again.

Jumping forward to 23 November, 2011, I am driving into the Brindabella Ranges to document the first ever release of the Northern Corroboree Frog. The plan is to release 100 one and two year old frogs today and then tomorrow another 100 frogs will be released at another location in front of the media. Today I had exclusive access to photograph the release and interview the staff involved!

Although the release was a joyous occasion for all those involved in the recovery of the Northern Corroboree Frog, this is not the end of the story. The 200 released frogs will not reach breeding age for at least another two years so it will be 2014 before they will start to call and make themselves heard during the annual Northern Corroboree Frog survey. That is if they survive!

With similar releases planned for subsequent years it will be ten years (or 2022), before we know if the program has had any impact in halting the decline of the wild Northern Corroboree Frog in the Brindabella Ranges.