Release protocol and process

Reviews of relocation programs have revealed that the failure rate is very high (Short, 2009) and releases of captive-bred animals have especially low rates of success. (Griffith et al, 1989, Fischer and Lindenmayer, 2000)
Ringtails from care are not captive-bred but share similar issues as they lack fitness and the training provided by mothers, are humanised even under the best of conditions and are simply not familiar with a life in a ‘wild’ habitat with changing environmental conditions.
Hand-reared and to a lesser degree rehabilitated animals are moved from a relatively secure environment with the provision of all essentials to in most cases a new habitat that was previously unable to sustain a natural population or a population large enough to be viable. This partly also applies to officially translocated animals displaced by development as source habitats were usually far superior to the available conservation estate they were moved to. 
There is also evidence of post-release reductions in fecundity of captive-bred individuals (Canessa, 2015) which might or might not apply to hand-reared animals.

The successful establishment of a viable population of any target species may depend on a range of objectives and environmental and biological factors that are difficult to influence in a large, well organised and funded projects. They are definitely outside the scope of any community-led relocation effort.

Immediate release practices are used for various and obvious reasons; however in the case of our ringtails the release practice could have been one reason behind the many failures.
Immediate release has been successful for several other small to medium sized marsupials in Australia when foxes were either excluded or only present in very low densities.  (Langford and Burbidge, 2001, Hardman and Moro, 2006)
Predator control and in particular landscape scale control efforts are outside the scope of most community projects but we can soften the impact of confusion and unfamiliarity with threats and/or resources by allowing time to acclimatise to a new environment before release, in particular for those animals coming from care or environmental conditions dissimilar to that at the release site. Research with tammar wallabies showed that animals improved predator-avoidance behaviour once they were accustomed to their new habitat. (Kemp et al, 2015) This might apply to ringtail possums too as mortality due to predation was especially high in the first few weeks in translocation research. (Clarke, 2011)

Site assessment is usually the weak point of any community-led release program. We lack the skills and knowledge and the funds to employ a scientist who has them.
Any data collection is usually limited to the target species for release. Other species even those that might compete for a similar environmental niche, the sustainability of the habitat and the potential effects of releases into a current population are rarely taken into consideration.
Ongoing monitoring of not only the released animals, but of the habitat for effects and changes would necessitate a level of knowledge and skills and a large volunteer workforce that is not available.

Contradicting objectives such as the benefit of high release numbers to avoid Allee effects and quick extinction of the new population through environmental stochasticity on one side and the risk of overstocking habitat that has not been assessed for its values and carrying capacity on the other, proved too complex even for official translocations.

The decision as to how many animals to release and the group’s composition depends mainly on availability of animals.  Maximising release numbers for the sake of a project would only be possible for departmental releases but might cause negative impacts on source populations as there is currently no breeding program in place.
Any inclusion of this issue in community-led projects would depend on excellent cooperation between rehabilitators/groups but might still carry the risk of either maintaining animals in captivity for longer than appropriate, which can reduce the average fitness (Clubb and Mason, 2003), or of releasing animals too young.

A release of males prior to females is deemed beneficial as it might prevent males from dispersing quickly in search of a breeding partner. (Hayward et al, 2012)
Also, there is evidence that providing females with a choice of partners could result in offspring of higher reproductive viability compared with those assigned one partner. (Drickamer et al, 2000)
Rehabilitators usually aim at releasing in pairs or providing one male for 2 females. In an established population this would hardly matter, but if establishing a new colony this could create competition between females (personal observation – surplus females are driven away by the matriarch) or reduce genetic quality.

In general widely dispersing individuals have higher mortality rates than those staying in the release area and males that disperse large distances could be lost to the newly forming population (Clarke, 2011, Moseby et al, 2014) which would be particularly problematic when males are scarce. Clarke observed ringtails travelling long distances in search of a new partner after the death of a mate. (Clarke, 2011)

The term ‘soft release’ creates an impression that might not be factual as every relocation into unfamiliar territory is stressful and carries risks. I therefore prefer the more descriptive than bias inducing term ‘delayed release’.

Species with higher site fidelity such as western ringtail possums might be especially vulnerable when translocated and exposed to stress and sudden predation risk. Delayed release might soften that impact and also provide shelter before dreys can be built. However, the opposite effect, an increase in stress levels, could be possible for wild individuals that then have to adapt to yet another cage in a new environment and prolonged time in captivity. Any confinement in a cage also carries a risk of injury.

Assessment of a site offered for releases  should include but not be limited to:

The assessment outcome for our main release site was deemed promising as:

Releases there started in May 2012. 13 animals that were either rehabilitated after injury/disease or displaced e.g. by the Margaret River fires or hand-reared were released in groups of 4 – 2 – 4 and 3 with a gender ratio of 3:1 - 1:1 - 2:2 and 2:1. 8 females and 5 males were released in 4 distinct areas. The last of those animals were released in October 2012.
Between May 2013 and May 2014 further 28 animals (only 8 of them males as we had a shortage) were released in distinct areas. In November 2015 and 2016 further 6 animals (2 of them male) were added to new areas.

Site ARelease cages (see 'Release cage' and 'Release cage design') were provided in a group setting and walkways into surrounding trees and/or to adjacent cages established.
Camera monitoring started to check for curious resident possums and whether the cages attracted predators.
Release animals were then transferred into their cages and fed until they had settled in, were eating well and no inclement weather was expected in the near future.
This first acclimatisation phase usually takes up to a fortnight.

The roof of the release cage is then opened in the later afternoon when animals are still resting. There is a clear urge to leave the cage; even the most humanised animals tend to do so in the first night. They however have the opportunity to come back to the cages for day shelter and most ringtails have at least come back for the first few days. Surprisingly this also applied to wild rehabilitated adults.

Animals lose weight through stress and the sudden ‘need’ or urge to look for their own food while exploring their outer surroundings. By providing quality food for a period after release weight loss could be minimised and therefore the survival rate increased. Apart from quality browse, fresh water is always provided.
Spring releases tend to adapt quickly to the on-site food supply as it is at its best. If the natural food supply is rejected, the release site is obviously inappropriate. Spring is the preferred release season into a presumed empty habitat.
At later stages of population increases females have pouch young or young at foot at that time and are extremely competitive and protective of their territory.
Autumn releases face less aggression from protective females but also enjoy a less favourable food situation outside the cage. Experience shows that animals that were released in autumn tend to come back to the cages for longer to supplement their food supply.
Supplementary food has been recognised in the literature as helping dampen dispersal tendencies and boost physical condition. (Boutin, 1990)

Even constant baiting will not eliminate predation pressure and a shift in focus towards building resilience in prey populations seems more promising. Prey species with long-term low-level exposure to predators have reportedly benefitted from longer term food supplementation and shelter provision. By helping meet nutritional demands animals were larger, healthier, and more resilient and reproduced earlier which led to larger populations that withstood predation pressure better and ultimately led to higher survival rates.  (Moseby et al, 2015a)

Supplement feeding is gradually reduced but in accordance with observed requirements. Water is provided year-round.

After leaving for good, the cages seem to turn into infrastructure and a known feature of the environment. Some animals occasionally come back to rest in the box in the cage on very hot summer days when they offer a shaded, low refuge.
Water stations are situated on top of a cage or – after the cage is removed – in a tree near-by. Cages and water stations are kept under camera surveillance. Footage is checked and recorded at least weekly. 

Possum boxes in near-by trees are also provided.  

release cages