Captive Breeding Proposal

Submitted by the Amphibian Research Centre for Recovery Team discussion in late 2001.

A recent meeting of the scientific advisory group for Corroboree frogs was held at the Australian Society of Herpetologists conference in Tasmania. The concerns of this group prompted the recent phone conference that included representatives of the recovery team. The result of the phone conference was to begin a program to increase the number of colonies of P. corroboree represented in captivity and therefore the genetic diversity of the captive colony in case the current trend of population decline continues. To achieve this eggs of P. corroboree were collected from a further four sites (20% of each clutch at each site) a fifth proposed site was found to have no eggs. The Snakey Plains colony was removed from the recruitment enhancement program (in accordance with an earlier decision to do so) but 20% of eggs from 10 clutches at Snakey Plains were included to represent this site in the captive colony. Implicit in the decision to collect these additional eggs was the need to hold these animals in the long-term. This action is a new initiative and has not been allowed for in current budgets.

Additional to this action is the need to consider the broader picture in light of the recent decline. The scientific advisory group is in agreement that the best remaining hope of recovering P. corroboree lies in a large-scale captive breeding and reintroduction program. Available demographic data (D. Hunter, unpublished data) indicates that ALL very small populations (less than 5 males) go extinct within an observable period of time, medium-size populations only get smaller over time, and there are no longer any large populations. Causal agents are yet to be identified and it is unlikely that they will be identified and alleviated before the frog becomes functionally extinct in the wild.

The proposal that we move in the direction of a large-scale captive program is an ambitious one. This species is not a good candidate for many reasons (low fecundity, slow to mature and unusual habitat requirements that are difficult to replicate in captivity).

Captive management at this point provides a three-point safety net:

1. While a large viable colony is held in captivity the species will not go totally extinct regardless of our knowledge of or ability to deal with the underlying causal agents in nature.
2. Captive breeding will provide stock for experimental reintroductions that may enable us to identify a means of recovering the species in the wild.
3. It will also be the ultimate source of stock from which the species is recovered if it has disappeared from nature.

The scale of what is required is unprecedented in the captive conservation of frogs and comparable to the most ambitious programs for any non-commercial animal species. The lead-time on this type of program is years, even after funding is found - if at all.

What we have committed to versus what we may need to do.

We currently have 439 eggs being held for the purposes of long term captive holding (these are in addition to the eggs collected this year for the ongoing recruitment enhancement program). They must be held until after we have additional monitoring data on the decline detected this year (by then they will have metamorphosed). To date we have not housed more than 50 young frogs. To house additional numbers will require augmented facilities. The scientific advisory group believes we should hold these animals indefinitely as the beginnings of the large-scale breeding program.

To develop a captive population that has the potential to produce stock for release will require supplementation of this group, from more sites and over a number of years. Again this is something we are not yet equipped to do.

To determine exactly what kind of captive program we need we must first consider what would be an appropriate overall goal. For example: to secure P. corroboree in the wild. We must then define appropriate objectives to achieve this. For example: to establish 5 sites each with 500 breeding adults. We must also specify a structure for these populations: 500 breeding adults released as 4 year olds yesterday is vastly different to a population that has been established slowly. For example we might specify 500 adults at a range of ages including sub-adults and juveniles coming through from previous years breeding or release.

Once we have agreed upon a goal and objectives we must decide how to achieve them. Do we build a multi-age population in captivity and then install it in the wild or do we release only one type of animal each year and keep doing this until the population reaches the desired level. If so what do we release - tadpoles, 2 year olds, adults? Do we do this at one site at a time or at several? It is almost certain that we will not know the answer to these questions until several years after we have been releasing animals at each life stage. It is therefore imperative that the captive breeding and release program is carried out, documented and monitored in such a way that we learn about what works and what does not work.