Journal of the Department of Agriculture, Western Australia, Series 4 Volume 31 Number 1 1990 Article 4 1-1-1990 Can kangaroos survive in the wheatbelt? Graham Arnold Follow this and additional works at: https://researchlibrary.agric.wa.gov.au/journal_agriculture4 Part of the Biodiversity Commons, Environmental Monitoring Commons, and the Other Animal Sciences Commons Recommended Citation Arnold, Graham (1990) "Can kangaroos survive in the wheatbelt?," Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 31 : No. 1 , Article 4. Available at: https://researchlibrary.agric.wa.gov.au/journal_agriculture4/vol31/iss1/4 This article is brought to you for free and open access by Research Library. It has been accepted for inclusion in Journal of the Department of Agriculture, Western Australia, Series 4 by an authorized administrator of Research Library. For more information, please contact [email protected]. Can kangaroos survive in the wheaibelt? mm mmmm By Graham Arnold, Senior Principal Research Scientist, CSIRO Division of Wildlife and Ecology, Helena Valley One of the costs of agricultural development in Western Australia over the past 100 years has been the loss of most of the native vegetation and, consequently, massive reductions in the numbers of most of our native fauna. Thirteen mammal species are extinct and many bird and mammal species are extinct in some areas. These losses will increase as remnant native vegetation degrades under the impact of nutrients washed and blown from farmland, from the invasion by Western grey kangaroo grazing weeds and from grazing sheep. on pasture in the early morning. Even kangaroos are affected. Unless the community manages remnant vegetation to minimise degradation and enhance the regen­ eration of native plants, kangaroos and some other native species will disappear from much of the Western Australian wheatbelt over the next 100 years. Impact of land clearing on kangaroo numbers All the land cleared for farming in West­ ern Australia was habitat for one or more species of kangaroos, wallabies and their relatives. The sizes of the populations of western grey Today, five species are extinct throughout the kangaroos and euros have declined considera­ wheatbelt, four species are found only in a few bly in many areas because of fragmentation of locations, leaving the euro and western grey their habitat into small patches that are often kangaroos as the only two common species isolated in a sea of farmland. Numbers would (Table 1). be even lower if these species had not adapted The brush wallaby was found on five of 23 to eating crops and pastures. flora and fauna reserves (Bendering, West To what extent has this fragmentation affected Bendering, Dongolocking, Tarin Rock and Du- the remaining population? From 1985 to 1989, rakoppin) surveyed by the WA Museum in the CSIRO surveyed 1,700 sq. km of the central 1970s. It is certainly now close to extinction in wheatbelt in the Kellerberrin, Tammin, Trayn- the 1,100 ha Durakoppin Reserve near Keller- ing and Wyalkatchem shires. Each of the 446 berrin, and probably in some of the other four patches of bush was visited and kangaroo reserves. It, like the tammar wallaby, the rock densities estimated from the density of faecal wallaby and the wyolie, has declined because pellets present. The area of each patch was of loss of habitat and severe fox predation. measured from aerial photographs. Wildlife researchers would like to know the locations of surviving populations of brush The whole area was then divided into 100 sq. wallabies in the wheatbelt so that they can km areas. For each of these 100 sq. km areas the study them. total area of remnant bush and numbers of 14 W A JOURNAL OF AGRICULTURE Vo/JI. 7990 Table 1. Kangaroos, wallabies and their relatives that are, or were, found in the wheatbelt Species Present occurrence Western grey kangaroo Common in all areas Common wallaroo (euro) Common in central and northern wheatbelt Black-footed rock wallaby Rare Western brush wallaby Very rare (black-gloved wallaby) Tammar wallaby Very rare Quokka Extinct Brush-tailed bettong Very rare (wyolie) Burrowing bettong Extinct (boodie) The habitats of the two species do overlap, but Technician John Weeldenburg holds an adult female euro Rufous hare-wallaby Extinct only partly. Euros prefer rocky areas such as areas in York gum - jam country, and graze that has been captured to have an identity collar put on. Banded hare-wallaby Extinct more than they browse whereas western greys prefer heathland and browse a lot. Crescent nailtail wallaby Extinct In the 1,100 ha of bush that are in the Durakop- pin Nature Reserve, euros and western grey kangaroos was calculated. The results were kangaroos live much as their forebears did plotted to see whether the density of kangaroos before the surrounding country was settled. A was the same at all levels of bush left in a 100 few kangaroos feed at night on nearby farm­ sq. km area. It was not. The more bush left the land, but most depend entirely on the natural higher the kangaroo density. vegetation for food and shelter. In areas where only 1.5 to 6.0 per cent of the Each animal has an area in which it lives, often countryside was still bush, there were on with many other individuals. This living area, average 0.03 kangaroos per hectare of bush. or home range, can vary in size from 60 to 200 Above 6 per cent bush, densities increased to ha depending on how good the habitat is in about 0.06 per hectare, and in one area with a different parts of the range, and on the sex of large remnant of 1,100 ha the density was 0.11 the animal. The large males that do most of the kangaroos per hectare. breeding have large home ranges that span This means that kangaroo densities have been those of many females. reduced by 70 per cent in many areas. The Some parts of the range provide mainly shelter question is, what does this mean for their long- from heat and cold, others mainly grazing and term survival in the wheatbelt? To answer this browsing. There are seasonal changes in the question we have to know how kangaroos live use of different parts of the home range, but on normally and how far they can change their any one day an individual moves only 400 to living habits to survive in fragmented habitat. 500 m. Kangaroos have a strong affinity to their home ranges although they may make occa­ How do kangaroos live normally? sional forays into adjacent areas. Most animals Western grey kangaroos and euros both live will spend their lifetime in the one home range. for up to 20 years. Most females are three years old when they have their first joeys, and about A few animals move away from where they are 80 per cent will have a joey each year. Breeding born. These are most often two- to three-year- is seasonal, with joeys emerging from the old males, and they may move up to 20 km to pouch from October to March. Mortality is set up new home ranges. This dispersion usually high in the year after the joey leaves ensures that genetic diversity is maintained the pouch, so that in most areas populations do widely. not go through boom and bust periods as happens in more arid areas. W.A. IOURNAL OF AGRICULTURE Vol. 31.1990 15 In parts of the wheatbelt where clearing At the extremes, where only 2 to 3 per cent of finished 30 years or more ago, the kangaroo the land is still in bush, 100 sq. km may support numbers in reserves and large privately owned only 10 to 20 animals. If these bush patches are remnants of bush have come into balance with widely scattered with one or two animals in a the resources available in the bush. Between 1 patch, reproductive rate could be low because and 8 per cent of the populations in a large the males may not be present when females are remnant will be seen at night on the surround­ in oestrus. The long term chances for survival ing farmland, but they are not the same in this situation are low, given losses from road animals every night. Most will never visit kills, and predation by man and by foxes. It is farmland because their home ranges go possible, although we have little evidence, that nowhere near the edge of the bush. Some will foxes kill many young euros that have just left visit farmland only once a week, and some on their mother's pouch. two or three nights. In other areas with more bush, and especially Living in a small patch of bush where one or two large (150 to 300 ha) patches of good habitat can act as population sources, In the area around Kellerberrin, and the chances of survival are better. Although situation in the rest of the wheatbelt is similar, kangaroos move across open farmland they two-thirds of the patches of bush are less than prefer to keep in cover, using road verges and 10 ha. Only 8 per cent exceed 50 ha. This is bush along creeks and fencelines. The mainte­ shown in Figure 1. Many are rocky outcrops nance of these corridors is an important part of that could not be cultivated or small patches of the long-term management of the countryside trees, but they have a diverse enough habitat to to conserve kangaroos and many bird species sustain permanent resident populations. Thus in the wheatbelt. most patches do not provide normal home ranges for kangaroos.