Water equals life

In most woodland areas water is only available as dew, rain on leaves or collected in tree hollows.
Ringtail possums (P. occidentalis and peregrinus) obtain a high percentage of their water requirements from foliage but also need access to fluids from more than leaves! (Hume, 2006)
This finding is not new but seems to not have found its way into newer research.

Water is constantly lost through urine and faeces and in hot temperatures by evaporative cooling for thermoregulation.
Ringtails thrive on young leaves after the trees’ growth flush. However in dry years the animals have to survive extended periods on suboptimal food – the percentage of indigestible matter and the toxicity is higher which can lead to critical impairment of the gut flora as dehydration inhibits the cleansing of increased toxic loads from the possum’s body. (B. Jones, personal communication)

Studies of wild western ringtail possums indicated that mortality rates were at their highest in late summer and autumn. All mortality events for which intact carcasses were retrieved showed evidence of significant loss of body condition. (Grimm and De Tores, 2009)
This is the time when most water sources have dried up and the time of the highest predation pressure. The poor body condition of the ringtails clearly increases their vulnerability to predation.

Ringtails are also prone to overheating and known to suffer physiologically at an ambient temperature of 35°C or above. (Yin, 2006, Yokochi, 2015)

Thermal extremes paired with resource limitations – both increasingly likely due to climate change – are recognised as major risk factor for chronic stress, disease and even mass mortality events in threatened wildlife species. (Hing et al, 2016)

The collapse of the ringtail population translocated to Leschenault Peninsula was detected in 2002 and has been ‘unexplained’. Changes in the baiting regimes were seen as a possible reason. However, Leschenault has no fresh water sources and 2001 (the year of the sharp decline) was the driest since releases in the early 1990s. (BOM weather data)

The almost complete disappearance of the largest ringtail possum population ever in the northern jarrah forest has also stayed unexplained but coincided with the driest decade on record.

Even if ringtails can survive without fresh water for a while (e.g. after a long wet winter), lactating females might be unable to support their young through the final stages of growth and development as mean daily water intake almost doubles during late lactation and water turn-over is faster no matter what season. (Hume, 2006)
Lack of access to water in the most important stages of life (reproduction) could result in a small transient sink population. (Tyndale-Biscoe, 2005)

At all our release sites we therefore provide fresh water year-round and it is used year-round.
Our camera monitoring data clearly shows that females with pouch young or dependent young come to drink particularly regularly at least every few days.

We hypothesise that this access to fresh water is the main reason for the successful establishment of animals at all release spots and for the clear evidence of breeding activity at all of them.

Water provision
We provided water from the start of the releases (May 2012), firstly only in the release cages, but placed the first outside water station on a cage roof in mid-October 2012.  From 2.1.14 onwards dedicated stations were established  in all (former) release spots. Unfortunately they were not always camera monitored because of a shortage of cameras.

In winter during wet spells we also had to retrieve the cameras for maintenance. Whenever a  water station was added or a camera reinstalled the uptake was immediate, mostly in the first night of deployment.

The implementation of water stations throughout the release property coincided with the very dry years 2014/2015. The measure might have avoided a similar downtrend as we experienced in Kookaburra Caravan Park, Busselton in 2016, where numbers halved.

Placing the waterer on top of a cage had the advantage that only one camera was needed to monitor both.
As water attracts all living creatures this however carried the risk that a predator might enter the cage while a ringtail takes refuge in there. Escape through a fairly narrow roof opening would then be problematic.

Water stations (mostly without food lures) on a trellis between trees are the preferred version as for instance cats would not be able to manoeuvre on it.  

Water dishes,  which can basically be all kinds of containers that are large enough to hold a minimum of 2 litre and are not too deep (7 cm maximum) so that young animals would not drown in them, can be used. In plastic containers holes can be drilled to hang them up otherwise a hanging basket needs to be fitted around the container.  

A major issue with these fairly small containers is that in hot weather waterers are heavily used as bird bath and can be empty in hours. Ringtails might then come for a drink but miss out.
Frequent service, at least every three nights, is needed in summer. Bees/wasps in spring/summer/autumn tend to collect water and often drown. There is a risk for humans and animals coming for a drink of being stung by a bee that cannot free itself but is not dead yet.

Birds also defecate into the water and they might carry diseases such as Psittacine beak and feather disease which could be spread to other birds.
The container need to be thoroughly cleaned at least on a week basis to avoid mosquito breeding. Ringtails are susceptible to Ross River Virus.

Big bird waterers hold more water and for longer in summer. Birds cannot take a bath in them and empty them quickly. However, they are harder for small animals to reach, also need frequent cleaning as  algae can form quickly in the bowl in heat and they tend to leak out if they get tilted. 
Monitoring water use is also less unambiguous as animals can sit behind the large bowl out of view when drinking.

If cages are still in place, water is also always available inside and even though visitation levels are much lower than at water stations, they are for instance used when outside stations are empty. For some animals it could also be a habit to drink from the dish that was used when the cage was closed.  Unfortunately monitoring water use inside cages would necessitate excessive numbers of cameras.  If there is also water available in a cage close to a water station , frequency of water usage cannot be quantified.

Water stations are highly frequented not only in hot weather (or nights after hot days).  In average between 80 and 90% of the events (1 event = 1 ringtail visit regardless of the number of photos) the animal will drink. This does not only apply to the hot summer months but also to the months May and June. Visitation reduces but the reason for a visit is clearly to drink.

Temperature seems to play a far less important role than the seasonal leaf quality and/or whether a female is raising/weaning offspring.

At times only the visit to a station is clearly captured on photo but not whether the animal is actually drinking. However, as there is no other incentive to come to that spot, it can be safely assumed.

Water attracts a variety of non-target species including brushtail possums, phascogale,  rats, birds and reptiles . (see ‘Attractant: Water’)
Brushtail sightings at water stations are significantly less frequent then ringtail sightings. We cannot estimate brushtail density for any of our release sites but assume that ringtail abundance is far higher at least for 2 of the 3 sites.

Fewer sightings in winter reflect the increased water availability everywhere but ringtails still come to drink. It might be habit, easy accessibility of stations, the clean water supply or increased safety due to the positioning in trees.

However camera function is equally reduced in very cold or wet weather as it is in heat. A lack of photo evidence does not necessarily mean animals do not come to drink.

Strangely ringtails seem to like hanging by the tail from a branch into a waterer. For some animals it seems to become a habit as it has been observed  on several  nights at the same spots and presumably by the same animals.

Ringtails seem unstressed when frequenting a water station and stay in average for 3-5 min for a drink but at times as long as 10-15 minutes.

In summer when parasite numbers might be high, water stations are not exclusively used for drinking but also for a bath. This also applies to brushtail possums.