Project monitoring

No determination of  relocation or release outcomes is possible without targeted post-release monitoring.

Direct sampling methods rely on  the physical capture of individuals. Western ringtail possums are hard to catch as they rarely enter traps that are placed on the ground. (Jones et al, 1994a) Traps placed in trees about 1.8 m above the ground have been far more successful, but Wayne reported that in excess of 3000 trap nights were needed for less than 100 captures. (Wayne et al, 2005) Hand-catching during the day seems easier than this, if you know where the animals rest.

Physical capture of animals also has significant disadvantages such as causing stress for the trapped animal particularly if detained for several hours. We therefore never utilise physical capture unless the animal is injured and has to be taken into care or euthanized. In this case, hand-catching is the usual method.
All our monitoring methods are non-invasive.

Cage traps are however used on our release sites to catch predators such as cats and foxes. Unfortunately bandicoots, brushtail possums and bobtail lizards are more often caught then cats. Phascogale were also observed when entering a trap, but due to their small size they can usually release themselves. When traps are used, they are checked in the early morning so that non-target species are detained only for the shortest possible period.
Traps are also covered with a hessian bag or similar to provide a sense of security for the animal inside. A small piece of wood placed in the door that snaps shut would also limit the force and leave space for a smaller tail. I am not aware of any tail or other injuries caused by cage traps on the sites we use.  

Two years after the start of the project our main release site was professionally surveyed in May 2014. At that time 41 ringtails had been released in 9 areas. Winter counts in general tend to generate the lowest ringtail numbers and some areas where very dense, wet and inaccessible.
Also, our footage gives an indication that brushtail sightings in the peppermint dominated areas that were chosen as release sites are higher from late summer onwards.
Twenty brushtail possums were counted. They were clustered in the peppermint dominated area around the dwellings and spread out in the middle part of the property that has very few or no peppermints. 23 ringtails were seen mainly near the release areas and only in parts of the property with a high degree of peppermint. There was clear habitat partitioning between the species.
The latest release of 9 animals had only been 3 weeks ago. As there were only 2 ringtail sightings in that release area a morning possum box check after the survey night was done und revealed 5 animals in boxes. The extremely low rate of sightings - 2 out of 9 – shows the difficulty of surveys in large, dense bush habitats and the likelihood of severe underestimates. In an open suburban habitat such as a caravan park, it is possible to see almost all resident animals, in dense bush obviously not.
Only because the releases were so recent, was it possible and even likely to encounter more than half of them in possum boxes.

The survey was conducted as a direct count, not using distance sampling, and seems to justify criticism from distance sampling proponents.
The only published example  comparing direct counts and distance sampling in the same area, indicated far higher numbers when distance sampling was employed. However the 2 surveys were 3 years apart and the reason for the difference in numbers could have been unrelated to the technique employed and in my opinion does not justify the assumption of unreliable results when directly counting.  (see: Jones et al, 2007, De Tores and Elscott, 2010)
In 1998 one hundred ringtails were counted in Leschenault Peninsula. In 2002 only two ringtails were sighted in the same area. Changes in population sizes can obviously occur rapidly and figures might not reflect the reliability of the survey method.

In all community initiated programs a lack of people power is a major drawback.
We used the professional survey as a blue print for further surveys but limited them to the areas with actual ringtail sightings. However, in dense bush we sometimes experienced nights with only very few sighting of any kind of animals – not even kangaroos in an area with a very high density population. Due to this, there is a major risk that in low density areas this could lead to the false assumption that it is devoid of a ringtail population. For a reliable assumption that an area is free of ringtail possums (or other species) surveys on 3 non-consecutive nights seem necessary, however, for a very large target area this would prove very expensive and time consuming.

The scientific literature does not provide conclusive results whether moon phases influence counts. Our own experience indicates that the lowest counts will be generated in the moon-less periods of a night. However, there also seems to be a correlation between darkness and wind. Dark nights with no wind sometimes still produced good results.
Even nocturnal animals need some light to be able to see and ringtails seem reluctant to emerge in dark, dense bush during moonless phases.   
Full moon seems not to influence ringtail activity in bush areas, but this might be different in a very open suburban context.
Heavy rain seems  to be a clear deterrent for activity but the human factor could play a major role in this assumption as it is very hard to identify eye shine in heavy rain. Even very wet foliage could result in unreliable counts.
Strong winds also seem to lead to reduced ringtail activity, however, again, the higher sound level would limit a person’s ability to hear movement and calls which helps finding animals in a low density habitat.

Activity levels have been particularly low in warm nights, which surprises me as even a warm night in the Margaret River area is rarely warm enough to pose a risk of overheating when active. I would also assume that warm nights would lead to increased visitation of water stations but this also does not seem to be the case.  
Activity levels have been similarly low in very cold nights which can be explained by the risk of body heat loss which would necessitate greater food intake which is hard to safeguard in winter.
All those observations have a large margin of error as human and technical limitations might play a larger role than we expect. Camera monitoring fails in the same conditions as humans tend to fail and particularly in heat or very cold temperatures and in rain, cameras do not provide reliable insights into activity patterns.
The observer’s level of skill and experience also influences the results. However, even the most highly skilled and experienced surveyor will encounter severe difficulties in  inclement weather conditions and inaccessible areas. The relation between the survey speed and the size of the area might also affect reliability of results negatively.

In very large areas such as for instance a national park, scat scoring is my preferred monitoring method. Dense understorey or heavy litter on the ground would influence scores in a way that I would not be able to correlate scats to spotlighting counts. It can then only be a means of proving presence of ringtails and determining breeding home ranges. Experience plays a major role in detecting scats and your eyes will get used to picking them up.

Sand-plot monitoring is useful for predator identification (tracks) but of course of very little use for monitoring of arboreal species.

The most reliable, in the long-term cost-efficient and least staff-intensive monitoring technique with the lowest impact  of interference with animals is probably the use of remote, night-vision cameras. Unfortunately purchase of a sufficiently high number of cameras for population-size estimates is out of reach of any unfunded community project.

However, the use of camera monitoring techniques can have a positive side effect apart from providing useful insights about ringtails. Cameras can add a motivational and educational component to citizen science projects and engage landowners. If community engagement should be a strong motivation, cameras need to have an easy to follow program menu to eliminate frustrating technical problems. Support and training then need to be made available when required. Training is critical before embarking on a program that aims at providing more than an occasional nice photo or video on Facebook. It took us at least a year to work out an experimental design and how to use our cameras most effectively. Skills will improve  in the longer term but human error will stay a constant feature. The analysis of the generated data is usually limited by the available manpower for the project. 

A major problem with community projects is also the establishment of an agreed upon project set-up. Ideas will vary what should be tested and in the case of possum release by rehabilitators most are not interested in going further than to ‘prove’ that their animals survive after release.

In our increasingly litigious environment it is also necessary to become acquainted with privacy protection laws.
In WA people need to be notified that an area is under camera surveillance which could attract thieves or vandalism. (Meek and Butler, 2014)  
We only use cameras on private property and of course with the consent of the landowners. Whenever footage shows people, those photos will be immediately deleted.

For a community project we are fairly well equipped with cameras (currently 40), however they are of differing age/level of deterioration and quality. Whether more (cheaper) devices are of more use than fewer (more expensive) ones, is a question of the breadth of usage, the perceived length of the project and their specific role.

We mainly use our camera monitoring as a tool for ‘adaptive management’. Constant observation of a situation allows for quick reaction if needed.
We monitor release cages and water stations as they attract animals. To monitor bush areas would necessitate a much higher number of cameras and  produce an enormous quantity of – mostly irrelevant – photos.

Most newer cameras can be set to night operation only, which would reduce the number of photos that need to be checked and would extent battery life. However, cages and water stations potentially also attract predators. The vital information that a diurnal predator has checked them out, would be lost.
Monitoring of predators and of our target species would ideally have different set-ups, however with a limited number of devices simultaneous monitoring is unavoidable.
We also – in a limited way – monitor tracks and other areas such as rabbit warren areas that are likely to show which predators are present. This can inform and aid baiting and trapping activities. (cat or reptile?)

Cameras take photos,  they do not monitor animals! After release of a low number of possums into occupied territory, cameras will produce nice photos of unidentifiable individuals but no data on establishment or longer term survival. Western ringtail possums have only very limited morphological features that could help differentiate between individuals in a photo. A capture/re-capture (on photo) model to estimate abundance is unworkable.
Photos rarely have the quality to show special marks or the gender of the animal and the tail is the only feature that in some cases provides some chance for identification.

We only start a new population in very low density habitat – usually too low for spotlighting – however, new arrivals attract resident ringtails. A radio-collared animal might lead to residents but when cameras pick them up, it is unclear whether it is a resident or a release.
To build up a large enough population (from very low density) for long-term viability in an adequately sized habitat (depending on carrying capacity) the minimum requirement would be for about 30 cameras in operation (without those for predator monitoring).
Survival of the population and to a lower degree fluctuations in numbers in a population can be monitored by camera – not single animals.

Behavioural studies would necessitate long-term recording of observational data, preferably with 3 cameras to scan a wider area – one of them recording videos. The suggestion that cameras can also be used to prove absence of a species is questionable in my view as there will never be enough cameras to scan a larger area and deployment times are often too short. Cats for instance avoid cameras and the absence of footage does not equate to the absence of cats.
However, in a comparison between the output of a camera and the observations of a person night-spotlighting, the camera would produce more identifiable (species) data if it was well placed, while a person would be able to survey a wider area. 

Sightings will vary significantly with long-term and short-term environmental conditions. 2 winters with average rainfall were followed by 2 mild summers (with some rain) and breeding activity had been visibly high and double-breeding occurred.
The latest survey by a person was conducted on a pleasant, dry and calm night in February 2018 (approx. 18°C, after 27°C highest day temperature), 2 days after the new moon. The survey was limited to an area where 36 ringtails had been released between May 2012 and (the last animal) November 2016. Coincidentally the count returned 36 ringtail possum sightings.
When I examine the footage on the night of the count for those areas that were not covered by the survey, a definite count of 10 animals ensues. 11 animals had been released between April 2014 and April 2016.  
46 ringtail possums – plus those that stayed hidden and those that had spread out into unmonitored areas – have definitely occupied the habitat in mid-February 2018. Even if I assume that the count was conducted under unusual, optimal conditions and therefore the ratio of 1 sighting per 1 miss that seemed realistic for all other counts was far surpassed, I acknowledge that the occupation is at habitat carrying capacity or already above it.

The coincidence that the figures for releases and sightings are identical might actually not be a coincidence at all. My hypothesis would be that all chosen release spots were viable habitat and animals therefore stayed close by. However, as this is a low density habitat, offspring had to disperse as the food situation did not allow for more animals staying on and increasing density. A complete survey of the entire area – under similarly optimal conditions - would be very beneficial to find out whether there is now a more even distribution over the whole property and whether animals have taken up residency in the areas with less peppermint.

Radio telemetry allows for identification of individuals and gives insights into questions such as the home range of an animal, however their use is questionable (see 'Ethics?') and limited to official research projects.

External markers such as ear tags would at least allow determination whether the observed animal was one of the releases, however they can be scratched or ripped off and injure the ear, cause infections, get damaged or be misread. (Gibbons and Andrews, 2004).

Micro-chipping is safe and a chip can usually be scanned throughout the lifespan of the animal. However, the read range – the distance between the scanner/reader and the animal’s body – is small (20-30 cm) and very close encounters with a micro-chipped ringtail are rare. Costs (about $25) outweigh usefulness.
Microchips can also not be read through a wooden box – the most likely environment for  a close encounter.

Passive integrated transponder tags (PIT) are basically the new generation of micro-chips. The chips are cheaper (around $7 each) but the readers are far more expensive (US$800-1500 versus approximately A$200 for a microchip reader). Small tags are inserted via large-gauge needles similar to the application of microchips while larger tags are surgically implanted either subcutaneously or into a body cavity. (Smyth and Nebel, 2013)

PIT tags are dormant until activated by a (battery-powered) reader to transmit its unique code and therefore do not require any internal source of power.  A hand-held reader needs to pass over the tag or in automated monitoring systems the reading system antenna needs to be placed in the suspected path of the animal. (Smyth and Nebel, 2013).

Such an automated monitoring system had been trialled for micro-chipped animals during the rope bridge study in Busselton (Caves Road), however the system failed too consistently to produce reliable data (K. Yokochi, personal communication)

PIT tag technology could be more reliable but a limiting factor is that PIT tags and readers must function on the same radio frequency which might not be the case when readers and tags come from different manufacturers or if manufacturers produce equipment with a variety of frequencies. (Gibbons and Andrews, 2004)

Small, inexpensive PIT tags have a similarly low detection distance as micro-chips – up to 30 cm – but they can be read through wood. Metal can however cause interference between the electromagnetic communication of the reader and tag. Operation frequency, antenna power, tag orientation and interference from other devices will also have an influence on the ease of reading and the read range. (Gibbons and Andrews, 2004)

Larger tags tend to have a better read range and some can be read with a hand-held device from a distance of up to 45 cm which would still lead to only very few hits when monitoring arboreal animals.

Injection/implantation seems quite safe and studies usually reported no mortality caused by tagging and little incidence of infection. Tag loss, mostly within the first 10 days of implantation, was rare with proper implantation. Tags can however move within the body, which has been documented also in mammals. This would make reading difficult. (Gibbons and Andrews, 2004)

If animal encounters are rare or only at considerable distance the cost of PIT tagging is probably too high for the small realistic benefit. However, it is significantly cheaper than telemetry equipment and if automated scanning is possible, monitoring could be very time-efficient. It is questionable whether transmission distances can increase enough  with technological advances to make it worthwhile for monitoring arboreal animals such as our ringtails.