Yarra Flats Park Kangaroos
For over 10 years now 'The Mob' have been a highlight of Yarra Flats Park.
The young bucks are often play fighting with each other.
Then as evening approaches it is time to impress the girls with some sprinting, high jumping and other cool moves on the way back to the treed accomodation for the night.
The Swamp Wallabies should also be briefly mentioned. They are smaller than Eastern Greys, darker in colour and have a white cheek stripe. They are much more cryptic and seldom seen. There are around half a dozen in the park.
Important information about Yarra Flats Park's Kangaroos
The noted Australian expert on Kangaroos Graeme Coulson from Melbourne University has studied the subject of kangaroos in suburban settings for decades. He has largely concentrated on Eastern Grey Kangaroos, which naturally are of great interest to us at Yarra Flats Park with our mob of 30 of them - along with a dozen or more Swamp Wallabies.
They generally breed well when conditions are good and feed is plentiful. Summer is the height of joey production.
In these good times the main causes of death are disease, predation by foxes and dogs along with being hit by cars. (Probably dingos pre-European settlement). Over half of kangaroos born die in the first two years of life, often in winter.
Young kangaroos often “disperse” from the mob – usually in autumn and winter. Most young male kangaroos disperse, but only a few females do.
Dispersing kangaroos are the main ones hit by cars. 50% of peri-urban male kangaroo deaths and 20% of peri-urban female kangaroo deaths are due to being hit by cars.
Kangaroos can disperse large distances across Melbourne – even up to 20-30km through suburbs! He gave the example of some kangaroos being tracked from Lilydale ending up at Upper Ferntree Gully and Gembrook.
Kangaroos hate dogs and are easily scared by them. We know all about this of course from episodes in Yarra Flats Park. The panicked kangaroos can be seriously injured and killed when they run into things, however, they also are susceptible to a condition called “Stress Myopathy”.
Myopathy happens when the animal is under extreme stress, as is the case when it is being attacked or chased by a dog. The animal does not have to be injured directly to develop myopathy, which is a disintegration of the muscle fibres. From within 24 hours up to a few weeks after the incident, the kangaroo will show stiffness and paralysis mainly in the hindquarters, progressing to complete paralysis, it will also salivate excessively, death will occur within 2-14 days after the stressful incident. Usually we will not see an animal in this state, as it will go somewhere quiet and out of sight to die.
Occasionally kangaroos will attack humans. Often the cause is that the human has a dog with them and the dog has frightened the kangaroo.
Over-abundance of kangaroos can and does occur. During the “good times” they breed up to large numbers which are eventually too much for the environment to cope with – especially when “lean times” come. They then eat everything in reach but finally starve, often taking other herbivores and the environment with them. This is called “irruption”. It is particularly a problem in island populations which peri-urban ones usually are. Graeme has done a lot of work on this issue.
Not all urban populations undergo this irruption though. Graeme has been studying the Anglesea golf course population and their numbers have been stable for years.
What is a reasonable population for an area? This is quite hard to judge and is very variable. It does require long term monitoring of populations.
What is the carrying capacity of Yarra Flats Park? Their numbers have only very slowly increasing, however, if the numbers do build up significantly this will need to be delved into.