Most graziers who are applying rest in their planned grazing management have been frustrated with the follow on grazing by roos. In the interests of scholarship I decided to identify where and what the roos were grazing in relation to the cattle in a time controlled grazing system.
The survey was conducted in April and May 2009, on a property in the Charters Towers area that had been managed under time control grazing for 7 years. The previous 12 months had been very wet with the rolling 12 months rainfall of 1300mm being double the 100 year median. 350 Brahman cross heifers of 200-300 kg were rotating through 21 paddocks that averaged 65 hectares. Planned rest period at this time of the season was 90 days. In the Ironbark and Box woodland the dominant pasture was Indian couch however there was a good recovery/recruitment of preferred grazing species happening; Buffel, Black spear, Golden beard, Blue grasses and Stylos. The roos were Eastern Greys and Wallaroos.
Very early morning observations of roo numbers were made along transects in paddocks and later in the day observations of roo grazing, scats and tracks were made where:
- The cattle were currently grazing.
- Paddocks recently grazed with less than 20 days of rest.
- Paddocks that had received 20-60 days of rest.
- Paddocks that had received greater than 60 days of rest.
Where they were
Maximum numbers and highest stocking rates of roos were grazing in areas that had been rested for 20-60 days (Figure 1). 68% of kangaroos were observed in these areas. Individual plants in these paddocks had regrown a flag of grass leaf approximately 50mm long with 20 days of rest and up to 175mm with 60 days of rest. The rate of recovery varied from species to species with healthy tussock grasses recovering from grazing faster than equally grazed Indian couch.
Seventeen percent of the roos were in the paddocks that contained cattle or the paddocks from which cattle had just been moved. The remaining 15% were in lanes (that receive intermittent grazing), and paddocks that had received more than 60 days rest and were due to be grazed shortly. The noticeable point with this 15% is that they were grazing plants that had previously been grazed by their own species. This was detected by the fact that the roos were targeting the shorter grown plants and leaving those plants that had regrown past 100mm. So there was patch grazing happening on plant by plant basis as well as an area by area basis.
What they ate
The cattle and roos were eating the same species, mainly grasses, though NIRS indicated 44% of the cattle diet was non-grass. Most of this was stylo. Roos were also seen eating stylos (Photo 3). Roos were selecting the shoots of plants in an early stage of recovery after being grazed by cattle. They did not seem inclined to graze plants in upper phase 2 and phase 3. This was obvious in areas that had received more than 60 days of rest. The roos in these areas were grazing in localised pockets that they had previously grazed (Photos 1 and 2)
The roos and cattle were eating the same species of plants and legumes but targeting very different stages of growth. Roos were grazing in the paddocks and from plants more recently rested. Their narrow and rapid bite allows them to select at the leaf level while cattle with a large slow bite select at the plant level. This targeting by roos of early stage regrowth of plants is the “wicked problem” for the grazing manager. The roo is not in competition with the cow but with the grazing manager and our ability to rest plants.
As it is our provision of water and cattle grazing that sets the pasture up for optimal roo grazing it is our problem to solve. Numerous management tools have been used over many years; shooting, water exclusion, guardian dogs and exclusion fencing. No one of these alone have been a panacea for roo related issues. However a carefully planned and costed mix of these tools is working for some graziers. Whatever solutions are adopted requires a commitment to ongoing management.
Photos of the impacts of kangaroo grazing, in paddocks rested from cattle grazing for >60
Consultant and RCS Next Steps Coach
Other April Newsletter article
Which Grazing System?
By David McLean