Introduction

This chapter examines the relationship between the population dynamics of kangaroos and their food supply in an arid rangelands environment. The relationship is called the numerical response (Solomon, 1949) and was introduced to quantitative ecology by Holling (1959, 1961) to model one component of a predator-prey system. Trends in numbers of red and western grey kangaroos on Kinchega National Park and on surrounding properties were monitored every three months between 1973 and early 1984 by standardised aerial survey. Rates of increase of kangaroos were plotted as a function of rainfall and pasture biomass. Rainfall is the dominant influence on an arid zone grazing system (Noy-Meir, 1973) affecting the rate of increase of both the plants and the animals that eat them. However while rainfall is probably the ultimate factor determining rate of increase of kangaroos, the biomass of pasture available to the kangaroos as food is the proximate factor. Pasture biomass was measured on Kinchega and on an adjoining sheep station, Tandou, at three-monthly intervals coinciding with the aerial surveys between 1980 and early 1984 (Chapter 4).

There are few studies of the population dynamics of large mammalian herbivores, probably because most grazing systems are stable and so exhibit little dynamic behaviour. There are virtually no grazing studies that integrate the dynamic interaction of plants and animals, the exception being Sinclair's (1977) study on the African buffalo.

This chapter briefly summarises the findings presented in the previous chapters and attempts a synthesis.

Weather

The weather at the Menindee sites is a sample of that of the Australian sheep rangelands as a whole. Annual rainfall over 100 years has averaged 236 mm with a standard deviation among years of 107 mm, giving a coefficient of variation (CV) of 45%. Serial correlation of rainfall between successive years is very weak at r = 0.13.

Whereas daily temperature has a marked annual cycle it is not paralleled by a similar seasonality of rainfall. The serial correlation between rainfall in the same season across successive years was estimated as r = 0.05. Hence rainfall is unpredictable across a year and unpredictable from one year to the next. In three of ten years the annual rainfall is more than fifty percent above or below the annual average. Floods and droughts are common.

Plants

The high variability of rainfall leads to a much higher proportion of annuals in the pasture than on any other continent. The dominant perennials are low shrubs with deep roots. The pasture layer waxes and wanes according to rainfall. One suite of predominantly annual species germinates with rain in winter. Another suite responds to summer rain.

We saw in Chapter 4 that the pasture biomass could be predicted from rainfall over the previous six months. The relationship was largely independent of time of year and influenced only weakly by soil type.

Introduction

This chapter investigates the mobility, home range and habitat utilisation of red and western grey kangaroos on Kinchega National Park and Tandou between 1979 and 1982. Of particular interest was how far kangaroos moved within Kinchega, how this compared with movements outside Kinchega, and to what degree, if any, these movements were constrained by the fence surrounding Kinchega.

Red kangaroos inhabit the harsh dry environment of inland Australia. Australians think of them as highly nomadic creatures that regularly move hundreds of kilometres in search of greener pastures. This high mobility is consistently invoked to account for the marked changes that are sometimes observed in their dispersion.

Scientific evidence conflicts with this view. There is no doubt that some kangaroos move long distances. Bailey (1971) recorded that red kangaroos moved up to 216 km away from his study area in north-western New South Wales during a severe drought. Denny (1982) recorded that a red kangaroo moved from Tibooburra in New South Wales to Lake Frome in South Australia – a distance of more than 300 km. However, many kangaroos remain in the same area for several years. Frith (1964) sighted a conspicuous group of red kangaroos eight times from November 1960 to August 1961. All sightings were within a circle of 5 km diameter. Bailey (1971) tagged 143 kangaroos. Twenty-eight were sighted within 8 km of the release site after a period of six months.

The diets of herbivores have been studied by many people throughout the arid zone of Australia. Here their findings are synthesised and compared with those from red and western grey kangaroos on Kinchega National Park. Finally the role of kangaroos in the dispersal of seeds is examined.

Methods

The investigation of diet on Kinchega began in November 1980 and ended in February 1984. Plant species were collected throughout the park and the specimens milled to make reference slides. Diets were assessed periodically from faeces collected in the field (‘field faeces’ hereafter) and from the stomach contents and rectal contents of animals shot to provide data on condition and reproduction (Chapter 9).

The field faeces were collected only from animals that were seen to void and so there is no possibility of the faeces being ascribed to the wrong species. Caughley (1964) and Grant (1974) maintained that the kangaroo species producing a faecal sample could be determined from the size and shape of the pellets but I was often unable to identify pellets to species, particularly after rain had produced a lush pasture. In such conditions the faecal material maintained no characteristic shape.

Introduction

In this chapter body condition, nutritional intake, and recruitment of red and western grey kangaroos are related to trends in weather and vegetation. Some data relating to condition and recruitment of sheep are included for comparison. Body condition is also assessed as a wildlife management tool, with particular emphasis on assessment of kangaroo populations.

The kangaroo data are part of a long-term investigation that will not terminate until February 1986. Findings discussed here are mostly drawn from data collected between mid-1982 and the end of 1984. Methods will be published in detail elsewhere, but the essential information is provided below.

From June 1982 until December 1984 female kangaroos were sampled every three months on Kinchega and Tandou. Samples comprised 20 red kangaroos and 20 western grey kangaroos from Kinchega, and 20 red kangaroos from Tandou. An additional sample of 20 red kangaroos was taken on Kinchega midway between these three monthly samples; on one occasion (January 1983) this was extended to include 20 western grey kangaroos. These additional samples of red kangaroos from Kinchega were discontinued after February 1984 as was all sampling on Tandou. There are thus substantially more data on Kinchega reds than on either Tandou reds or Kinchega western greys. Western greys were not sampled on Tandou because they were at too low a density for samples to be readily obtained.

Introduction

Rainfall is the dominant factor controlling the growth of plants in arid lands throughout the world (Beatley, 1969; Ross, 1969, 1976; Noy-Meir, 1973; Ross & Lendon, 1973; Gutterman, 1981; Orr, 1981). Much of the variability of pasture biomass can be explained by rainfall (Noy-Meir, 1973; Chapter 4). Temperature also plays a role in the initiation and success of germination and the survival of seedlings (Beatley, 1967; Gates & Muirhead, 1967; Lendon & Ross, 1978). Hence, rain falling at different seasons in the arid zone stimulates the germination of different suites of plant species.

This chapter reports the effect of rainfall and temperature on changes in soil moisture, pasture biomass, pasture growth and species composition on the two major soil types of Kinchega National Park.

The study posed the following questions:

1. (1) What is the relationship between rainfall and soil moisture and how does it differ between the two major soil types within the Park?

2. (2) Can trends in soil moisture or a knowledge of rainfall and temperature be used to predict changes in pasture growth and biomass?

The study was conducted within two exclosures, one on each of the two major soil types within Kinchega National Park. A fence excluded mammalian herbivores. Hence, growth, dieback and trends in biomass are measured in the absence of grazing. There is considerable evidence that grazing affects the growth rate of plants, sometimes stimulating growth and sometimes depressing growth or killing the plant (Harper, 1977; McNaughton, 1979).

Introduction

There are only three ways that we can manage a population of wildlife. We can control it or even exterminate it, we can utilise it to provide a continuing yield, or we can cherish it for its intrinsic worth. The decision as to the right option will be determined mainly by what we consider the appropriate use of the land on which the animals live. A population of kangaroos living in a paddock of wheat will not be viewed in the same way as one living in an unutilised desert.

In this chapter we explore the options available for managing kangaroos on two classes of land – national parks and nature reserves, the perceived primary function of which is to conserve, and rangelands whose perceived primary function is to produce. Most people agree on the primary function of those classes of land, but when those broad functions are specified more fully they reveal an underlying layer of secondary objectives which may conflict with each other. These in turn, depending on the ranking assigned among them, generate a range of procedures whereby kangaroos might best be managed.

Management within national parks

The appropriate management is determined less by what is happening on the ground than by perceptions of what the national park is for. We will trace the history of these changing perceptions to show how they determine the ‘appropriate management’ of the soil, plants and animals within the parks.

ABSTRACT. Cancer incidence in northern Alaskan villages exposed to radioactive fallout from nuclear weapons testing in the late 1950s and early 1960s was assessed using data from the Alaskan Native Tumor Registry. Previous studies have shown that cancer incidence in Alaskan natives differs from that in residents of the rest of the United States: rates of cancer of the nasopharynx and liver are higher in Alaskan native men and rates of cancer of the nasopharynx, gallbladder, cervix, and kidney are higher in Alaskan native women. Leukemia, breast cancer and bone sarcoma are the cancers most likely to result from fallout exposure in the Arctic, but the incidence of these cancers in the North Slope villages appeared to be lower than in either the entire Inuit population or the US population.

The fallout radionuclides of potential health concern are cesium–137 and strontium– 90, because of their abundance, long half-life, and chemical characteristics that facilitate transport through and concentration in the food chain and accumulaton in sensitive tissues of the body. Radionuclide body burdens were determined in North Slope Inuit 25 years ago, because of their possible exposure to radioactive fallout via the lichen-caribou-man pathway. Cancer risk estimates have been calculated using highest average dose measurements from residents of Anaktuvuk Pass, under the assumption that peak exposure levels of the mid 1960s remained steady over the following 20 years. Worst-case estimates of expected cancer excess were calculated for leukemia, breast cancer and bone sarcoma.

ABSTRACT. Three laboratories in China, Japan, and the United States have initiated cooperative investigations of atmospheric aerosol formation and transport to the Pacific and Arctic. Both desert dust and air pollutants from urban or industrial areas have been sampled near their sources in China, at sites in Japan, above the marine boundary layer on Hawaii, and over the Arctic Ocean. Aerosols, sorted by particle size or temporally resolved using cascade impactors or time sequence filter samplers, were analyzed for elemental composition by proton-induced X-ray emission (PIXE). Dust storms in China greatly raised concentrations of very coarse particles, but particles finer than 1 fim (those of greatest human health concern) are raised much less. Dust carried over Japan during spring contains three components—soil particles, sea salts and air pollution sulfur—recognizable by element concentrations in filter samples collected sequentially. Hawaiian springtime aerosol contains particulate sulfur temporally coherent with soil dust, suggesting trans-Pacific Asian pollution and desert sources. Arctic aerosol, sampled in spring by aircraft-mounted cascade impactor, contains both fine pollution sulfur and soil elements mainly in ultra-coarse particles more than 16 μm in diameter, with Si/Al approximating that of shales or clay minerals but less than in average earth crust or Asian loess. Dust from a Chinese desert area shows Si/Al close to average earth crust or loess.