A salt lick used by kangaroos. Is this the first recorded observation in Victoria? Do other macropods make use of the site? Should provision of salt blocks be a factor in conservation planning? Tanya Loos explores unfamiliar paths.
I AM A BIT of a stay-at-home naturalist, padding up and down the same worn bush tracks in about a 30km radius of Daylesford, Victoria, with a lovely bush area called Porcupine Ridge as the epicentre, my bush block. I am in Grassy Dry Forest, on the very edge of the Central Victorian uplands bioregion, so we still get Narrow-leaf Peppermints and the mighty Messmates, and forest birds such as Gang Gang Cockatoos and the occasional Crescent Honeyeater.
Sharon and Dave are like me, exploring their area intimately, and they live down the road in the Goldfields area, past Mount Franklin or Leanganook, in the Yandoit bushlands. Dry open forests of box and Red Stringybark, and mammals such as Brush-tailed Phascogale.
“Come for a walk with us, Tanya, and we will show you the kangaroo lick” they said – and being a real enthusiast for animal tracks and signs such as owl and raptor pellets, burrows, scratching, prey remains and the like, I could not refuse. I am also very interested in finding out more about the lives of common animals.
It was a motley crew of kids, adults and mostly elderly little dogs who went on the walk that day. After an hour or so of walking and quite a few kilometres we came to the kangaroo lick. The strange little overhang had been noticed by Sharon and Dave some time ago, and there were obvious scratches and teeth marks in the clay walls of the lick. Taste tests could not really discern any saltiness in particular – so it wasn’t conclusive. Until one day – success! An Eastern Grey Kangaroo was observed with its head deep in the lick, and after it had moved on, fresh bites could be seen.
These photos show the position of the lick in the landscape and the size here is demonstrated by small terrier, Daisy.
Time for some scientific research! Many of you will understand the thrill when you find a scientific study that sheds light upon
a behaviour or species – in this case I had hit the jackpot. “Facultative geophagy at natural licks in an Australian marsupial” published in the Journal of Mammalogy in 2013. This study shed a lot of light on the Yandoit clay licks and has also raised some intriguing questions.
The paper’s lead author is Emily C Best from the University of Queensland. For her PhD Emily intensively studied a population of Eastern Grey Kangaroos (Macropus giganteus) and other large macropods in Sundown National Park, Queensland. The main object of study was female relationships and personality types within the group – looks like fascinating stuff! It obviously involved a lot of kangaroo watching and two very large natural licks and several smaller lick sites were identified during the study.
Geophagy is the technical term for eating soil. Many animals practice geophagy, including humans. Ever seen those amazing photos of Scarlet Macaws crowded at a river bank eating clay? The parrots are eating the clay to absorb toxins from poisonous fruits and seeds. In most grazing animals, geophagy is practised to compensate for dietary deficiencies, and replace essential minerals such as sodium and to a lesser extent, potassium, calcium and magnesium.
Before Emily’s publication, there were no documented cases of geophagy in marsupials – various indigenous people from around Australia must have seen the salt licks, and maybe even capitalised on them and hunted the roos there, or used the clay themselves (though nothing has been published about this). The Eastern Grey Kangaroo is one of the most intensively studied marsupials across its range, and this behaviour had previously not been observed by any researchers. If geophagy is noted in all of the eastern grey populations, it is clearly a requirement for their health and thus a widespread behaviour. Hence the term facultative rather than obligative was applied to Emily’s Eastern Greys – facultative implies ‘carried out when necessary’; so Emily
and colleagues tried to work out when and why geophagy occurred in these particular Eastern Greys.
The soil at the lick sites was tested for mineral content, Emily observed who was using the licks (sex, age class, reproductive state), and the mineral content of the kangaroos’ diets was assessed, and finally carried out some complicated statistical analyses.
The clay licks examined in their study had significantly higher levels of sodium, magnesium and sulphur than surrounding random soil samples.
The frequency of visits to the lick sites significantly increased during high temperatures. This is believed to be due to sodium loss from the arm licking behaviour that kangaroos use to keep cool on hot days.
The licks were visited most frequently by lactating females with young. Geophagy during lactation periods is also seen in other animals such as White-tailed Deer in the US and Sika deer in Southern China.
Finally the licks were visited the most in December and January, when the fresh green grass has really high potassium content, and hinders the kangaroos’ ability to absorb sodium.
The authors state that “geophagy is most likely to be found in areas with high temperatures that are naturally low in sodium”. They also note that the natural lick sites were used by all four macropod species in the study area: Eastern Grey Kangaroos, Eastern Wallaroos, Red-Necked Wallabies and Swamp Wallabies. Emily and team end the article by stating that: “It is possible that the minerals present in licks may be important for many threatened and endangered macropod species living in areas
naturally low in sodium. Therefore, especially given the ease of putting out salt blocks, sodium demand should be considered during conservation planning and translocations of threatened macropod species”.
So back to the Yandoit bushland lick. One wonders whether the Yandoit area is a low sodium area? Is Sharon and Dave’s observation of an Eastern Grey using a clay lick the first recorded instance in Victoria? Do the local Swamp Wallabies also use the lick? Sharon and Dave report another lick of a similar size nearby – and at 1-2m neither lick is even half the size of the two major licks in Emily’s study – both of which were some 12 metres across. Does this mean that the geophagy in the Yandoit area is not as crucial as in the hot inland areas of Queensland?
How wonderful that a Saturday afternoon stroll with kids and dogs and local naturalists can spark so many questions! I will be notifying Emily of this sighting, and staying in touch with Sharon and Dave in case they come across any other clay lick sites. If you know of any in Victoria, I would be most interested!
Tanya is a nature columnist for the Hepburn Advocate, and in 2013, published a book called Daylesford Nature Diary; six seasons in the foothill forests. Tanya is currently ‘Habitat for Bush Birds’ Project Coordinator with Connecting Country. Read more from Tanya on her blog From forest to forest https://tanyaloos.wordpress.com/author/tanyaloos/
Best, Emily C., Julia Joseph, and Anne W. Goldizen. “Facultative geophagy at natural licks in an Australian marsupial”. Journal of Mammalogy 94, no. 6 (2013): 1237-1247.