OBSERVATIONS OF ECHIDNAS, ROYAL ARCH CAVE - CHILLAGOE 1990-1992
The Royal Arch cave is one of two regularly run (daily) show caves. The cave is a very flat horizontal maze which runs virtually at the same level as the outside plain. The cave floor has minor undulations throughout its one kilometre of constructed walkways with small rises and falls of up to 4 metres when the walk traverses debris from collapsed roofs. The cave extends upwards inside a 30 - 50 metre high jagged limestone hill which is classic tower karst. Horizontally the Royal Arch extends over an area of several hectares. Structurally the cave has dark corridors which break out into large daylight caverns about 20-30 metres high. The cave walls are virtually dry for the 8 month dry season, although large areas of the natural mud floors stay moist for much of the year. During the wet season from mid December to mid April about 5 - 10% of the walls become wet. Most of the speleothem deposits of cave coral and flowstones are permanently dry. Natural access into the cave is through holes in the roof or at the base of the bluff. Vertical descent through the daylight chambers is possible by abseiling, although several areas appear to be climable. Two walk-in entrances, one now fenced and the other gated, have provided easy access to visitors over the years.
The gated entrance permits access to echidnas through a 95mm gap under the gate. The fenced area has gaps of 110mm high but boulder rubble and drops would seem to make it difficult for them to climb out.
When I began with the Queensland National Parks and Wildlife Service in 1980, guides knew about the long cylindrical blackish grey droppings up to 7cm long and 1cm wide on cave floors. Every cave visitor did too, as a scat was especially common along the first half of a standard cave tour (i.e. the Entrance - Organ - Picnic - Cathedral routes). However what was not definite was what animal produced it. Some of the scat was thought to be from feral cats purely because of it's size (despite various attempts to rid the cave of cats they persisted until about 1988 and they were not seen again until 1990 for a short time).
Also at the time, echidnas were occasionally seen during cave tours so scat was (correctly) assumed to be echidna. The puzzling thing to some guides was that some droppings appeared to be to0 large to be echidna, but if they were a cat, why were they not buried?
Early on I noticed what appeared to be beetles and termites in some scats which were straight-sided and earthy. At the time I commenced, guides did not voluntarily talk a lot about the scats on tour and they were often dismissed as cat.
Not long after I began guiding I began to make a point about the droppings - their abundance, freshness and speculation as to what they were. It did not take very long before I had an offer of help from a visitor to have it identified by the Queensland Museum. After one tour I collected half a dozen scats covering a range of colours, shapes and sizes and sent it away with the visitor for identification. The results suggested it was all echidna. Apparently all had some termite remains although the scats were not composed exclusively of them.
From then on scats were considered to be from echidnas and I incorporated this into my interpretive message on cave tours. For example, visitors were regularly asked to guess what animal makes the droppings, keeping in mind that "they come from an Australian native animal which most people do not expect to be living voluntarily inside a dark cave. The animal appears to be living in the cave by choice and appears to be able to freely move into and out of the cave as it wishes". Many visitors become totally engrossed in attempting to guess the animal. Some spontaneously examined the scats and discovered the termite remain. Some occasionally saw the animal on tour and made the connection. Most however did not, but it never ceased to amaze me how a little bit of intrigue and enthusiasm can make visitors become so involved in trying to find out.
Perhaps they had never been challenged to look at the scats so entirely before.
For some time, guides accepted that most scat was echidna. However about the mid 1980s, cane toads (Bufo marinus), which had been quite rare in the caves, occasionally became a little more prominent. Although their droppings were generally tapered, compacted with beetle shells and smaller, some of the larger ones were initially thought to be too large for toads (7cms). Gradually toad droppings became more widespread. Coincidentally at the same time the amount of fresh echidna droppings dropped dramatically. At this time I was also interested in the composition of echidna scats which appeared to vary a little in amount and type of insects. Occasionally there appeared to be some insect remains which were not termites and ants. From memory there was a transparent wing fragment and what appeared to be small beetle wings in the odd scat. I can not remember if I sent these scats away for analysis, but I did get confirmation again that the scats sent were echidna. Later on I sent another batch of scats away to a long term entomologist friend, Ross Storey (Mareeba Department of Primary industries), who analysed the insect content of three (3) partly disintegrated scats, about June 1990. I do not know if they were a mixture of echidna and toad scats. His summary was:
Isoptera, Termitidae soldier heads of the soft bodied Nasutitermes
Hymenoptera,Formicidae - several species of ants (most common insects present)
Hemiptera,Cydnidae - several wing fragments
Coleoptera,Carabidae - 1 pair of elytra
Scarabaeldae - at least 4 species including 2 melolonthines and one hybsorine
Terebrionidae - at least 4 species including Eutherma sp, and 2 heleines
Curcullonidae - one hard bodied cryptorrhynchine (undigested)
Blattodea - 1 cockroach
Ross concluded his analysis by commenting "the majority of these insects I would expect to find outside the cave environment, though perhaps they stray in occasionally".
Echidna Versus Toad
In January 1993, I showed the analysis above to University of Queensland PhD student Chris Pavey, who felt that the scat composition indicated a degree of cane toad presence. Following this up Professor Grigg and assistant Lyn Beard, echidna researchers from University of Qld, agreed. Lyn's reply on behalf of the team was:
"At least some of the scats analysed would have probably been from cane toads. In our experience echidna scats very seldom contain anything but dirt, and termite remains. The only other things I have heard of being identified in echidna scats are scarab beetle larvae, and this only in the New England area. Of course this is not to prove that they are not echidna scats but I would have to say that the most likely explanation for the presence of so many beetle remains is that at least some of the scats were from cane toads.
I find it hard to imagine how an echidna could catch beetles unless it were scavenging dead ones. Cane toad scats certainly resemble echidna scats at first glance, but generally are not smooth sided. A dry echidna scat can be almost cement-smooth along its sides and is usually quite obviously broken on each end. Echidna scats can persist for a long time too, probably years, so an accumulation from a few animals can look like quite a lot over time."
Every guide was required to make a note of every echidna seen on every Royal Arch cave tour. This was to assist me to monitor any change in the frequency, abundance and time of year that they were seen. The size and condition of the animal was to be noted. When I first arrived guides would irregularly record sightings of echidnas. The frequency of written records for echidnas was directly proportional to a guide's personal interest and personality.
Additional details about location in cave, activity, sex, size etc was not recorded. Had every sighting been noted, then some correlation could have been possible between abundance and climatic seasonal conditions.
Summary of Observations
Specific data is presently being collated for sightings which were recorded. In lieu of this I have summarised my observations during and outside cave tours. These are recorded below:
- The frequency of sightings decreased from 1980 until 1992.
- Echidnas were more often seen in the early 1980s when there were "wetter" wet seasons.
- Echidnas can be seen at any time of the year, but are more likely to be seen in the wet season.
- Echidnas were seen on average about one month every year, regularly, until the late 1980s.
- Echidnas have not been seen since about 1989 by any guide.
- Guides are usually restricted to one sighting on a cave tour.
- The most number of sightings on the same tour was 3 (i.e. 2 different animals on a tour I had about mid-1980s)
- About 50% of the sightings involved sleeping animals rather than moving ones. Echidnas are rarely, if ever, seen in the same place on consecutive days.
- Echidnas prefer to sleep in a hollow where the cave wall meets the floor e.g. opposite the Leaning Tower of Pisa and near the phreatic tube, and in the Avon Chamber and to a lesser degree near the phreatic crawl at the entrance to the Stage Chamber.
- Most echidnas which were seen tucked up into a ball in a small hollow in the wall, and thought to be asleep, were gone by the time the guide returned at the conclusion of the tour.
- Echidnas were mostly seen in the Leaning Tower/Entrance chamber area, the Avon/Cathedral Chamber area and the Walrus/St Bernard/Stage area to a lesser degree.
- Echidnas have been seen (by me) in every daylight and dark passage except perhaps the Figtree, St Bernard and Ballroom Chambers. This includes sightings in the now non-visited area of the Swiss Cottage.
- Echidnas have probably left scats in every chamber and passage over the years including the non tourist areas.
- Echidnas, when seen, were large, healthy adult sized animals.
Presence In the Royal Arch
Ever since I guided, I was fascinated by the presence of echidnas in the caves. Why were they in the caves? How long had they been there? Why were they more common at some times of the year than others? For me it was not sufficient to be just told they were sleeping in the caves I wanted to know if there were other reasons why echidnas were visiting or living in them. I started to think about:
- Do the echidnas mostly live outside the cave and enter at a certain period of the year?
- Are the echidnas mostly cave inhabitants which leave at certain periods?
- Are they permanent inhabitants of the cave?
I knew answers could be easily provided by a simple tagging program, but until that occurred I knew I'd have to rely upon observation and scientific recording. Hopefully tagging will one day provide information about the following:
- number of sightings;
- are the sightings of different animals or the same individual
- movement of echidnas inside and outside the cave including distance, time of year, location etc;
- age of animal and sex.
Discussion of Observations
All animals have four requirements for survival: shelter; food; water and the ability to reproduce. These will be discussed in turn to explain the echidna's behaviour.
Most echidna sightings were made in the wet season. It seems reasonable to assume that the echidnas enter Royal Arch to escape the hot humid conditions of the wet season. Over a three year period in the early 1980s weekly maximum and minimum temperatures were recorded in a dark area near the Leaning Tower of Pisa. The temperature varied from about 22°C - 14°C (from memory) in that three year period and by only 0.5°C from week to week. External temperature measured at the QNPWS office 5km away ranged from about 42°C - 30°C during the corresponding period. (The thermometer was located 2m high under a tank stand.)
Beard commented the "echidnas cannot cope with heat. They will die at a body temperature of about 36°C. They have no sweat glands to dissipate body heat so they tend to avoid activity during the daylight hours in hot climates. Echidnas are known to use caves in many other areas (e.g. Western Australia and in our study area in south-east Queensland), presumably because of the relatively benign thermal environment they offer. Sleeping during the day and foraging during the night during the hot, wet season of North Queensland would be entirely consistent with what we know of echidna behavior. They are fairly timid and easily disturbed so it is not surprising that an apparently sleeping echidna is no longer in the same place on the return of a cave tour. We have also noticed in our tracking studies that echidnas dislike rain, which would be another season for them to shelter in caves during the wet season."
Echidnas were seen occasionally in the Royal Arch during the dry season (May - November). External temperatures are about 22°C Max - 10°C Min mid year. I presume shelter is not the reason for entering the caves then. Beard commented "Cool to cold temperatures in the cave would not be a problem in winter as echidnas, in our experience, are much more tolerant of cold than they are of heat." However during an unusually cold year in the early 1980s when the overnight temperature was 3°C, it would be interesting to know if the echidnas had entered the cave to escape the cold outside.
For about eight months of the year there is no surface water outside the cave, nor is there any visible water inside.
Echidnas do not appear to be drinking the water from the caves, although perhaps some of the dry season sightings might be animals looking for water. However this seems unlikely. Beard comments "Fresh water does not seem to be important to echidnas. They do not seem to need to drink very often, presumably conserving body water efficiently and gaining metabolic water from food."
Echidnas mostly eat termites and ants. Beard says they are not known to eat beetles apart from scarab beetle larvae. This is something I wish to verify in Royal Arch cave. Whether echidnas are permanently or temporarily living in Royal Arch cave, Beard says "The distance from food sources is no problem. Echidnas are surprisingly mobile, commonly moving from one side of their home range to the other side in a night's foraging (easily a kilometre distance).
They are also surprisingly good at negotiating rough terrain, so the termite mounds you describe 1 - 200m from the cave would present a perfectly adequate food source (I have even seen an echidna climb a few metres up a tree)."
Echidna scratchings at the base of termite mounds are quite common in the area.
Echidnas have been seen around the two possible entrances in Royal Arch i.e. the present gated entrance and the fenced off "old entrance". The Old Entrance would be difficult for echidnas to negotiate especially exiting as there are several large rocks, holes and a climb to cope with. However on one occasion I saw an echidna just inside the cave near the fence. A third possible entrance could be a connection with the fairy caves near the Royal Arch entrance. If echidnas exit under the gate, fortunately they have a 95mm clearance. Cave managers need to consider factors like clearance when developing caves so animal movement is not impeded.
Echidna food is almost non existent in caves. I expect if echidnas find food inside caves it is pure chance, although they might occasionally attempt to forage if trapped in a cave. I am interested in knowing, if an echidna is forced to, can they make do with other insects like small beetles?
I know termites and ants occur in caves although they are rarely seen. I placed a piece of ply in the entrance to Clam Cave in January 1990 and within a month it was covered by small termite tunnels. No termites had previously been seen in the cave. Several times over the last couple of years in the terminal chamber of Teeter Cave, I have seen a vertical termite tunnel on the bare cave wall. Very little organic matter was present in the area and no other evidence of termites was seen in the cave. I have also seen termite tunnels in other caves.
Strahan states mating occurs in July/August. Do echidnas enter the cave to mate? Beard comments "I suspect it is unlikely they use the cave to come together and mate. The males usually follow a female by scent trail (we think). It is possible, however, that the female echidnas use the caves as good nurseries for secreting young in the later part of the year."
Without having the advantage of data from a tagging study, it is possible to only speculate what the echidnas are doing in the caves. I tend to feel the animals are not permanent residents but enter the caves for part of the year, maybe when external conditions like heat and rain are unfavorable. During the dry season the reasons for entry may be a combination of positive and negative factors. These might include females positively seeking refuge for young, and negative factors causing a response to some stressful condition (e.g. looking for a temporary refuge from heat and rain due to unseasonal conditions).
I also expect some sightings are echidnas accidentally visiting the cave while others may be animals seeking refuge from fires outside.
Echidnas do not seem to be visiting the cave looking for water, food or a place to mate. Shelter appears to be the main reason for visiting the caves.
Beard, Lyn (1993) facsimile dated 21/05/93 in reply to reading 1990 draft of this paper (University of Queensland Researcher)
Strahan (1983) Complete Book of Australian Mammals
Pavey, Chris (1993) Letter dated 13/02/93 in reply to reading 1990 draft of this paper (PhD student, University of Queensland, Department of Anatomy and Entomology)