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'Stages in the spermatogenic cycle of Ningaui ridei, N. yvonneae and N. timealeyi are defined and the phenology of these stages is presented. In males of Ningaui spp. sexual maturity is reached in the first year, such that after the end of July of each year almost all male Ningaui spp. are considered reproductively mature. Male Ningaui spp. in the active spermatogenic phase are found during the entire season of births (August-January in N. ridei and N. timealeyi but perhaps terminating earlier in N. yvonneae); testes regress to an immature spermatogenic stage after January. There is no indication that in the field adult males die immediately following mating.

Slopes and elevation of the regression of lizard species richness versus area for small ( < 25 ha) isolated areas of 'natural' vegetation in the Western Australian wheatbelt are not significantly different from those for Western Australian continental island groups. Similar-sized coral islands in Houtman Abrolhos, however, have relatively few lizards, and their species richness is independent of area. This is not attributed to ecological instability of coral islands but to the homogeneous habitat of coral islands and the nature of 'strand' lizards. No family of lizards appears to be favoured in small isolates or islands. It is suggested that the ecologically more generalized species predominate in small areas.

Breeding, population dynamics and seasonal changes in physical and physiological parameters were examined in Isoodon macrourus at the Mitchell Plateau between September 1981 and November 1982. Females gave birth to litters of 2.5 1.0 (16) young between September and April. They produced up to three litters in a breeding season with an average interval between successive litters of 89.5 (51-108) days. Adult testosterone levels and scrota1 size began to increase in July and peaked in September 1982. The overall ratio of adult males to adult females was 1:0.54; it was 1:0.80 for pouch young. Females were more frequently trapped on sequential trips than were males. Density on the grids increased towards the end of the dry season (July and September 1982)-mostly as a result of increased numbers of females. Adult males and females moving onto the grids during the dry season tended to select different habitats. Adult males moved significantly more in the wet season (September 1981, January and April) than they did in the dry season (July and September 1982); they also moved significantly more than adult females in the wet season. Seasonal variations were recorded for most physical and physiological parameters. During the wet period from September 1981 to January 1982, body weight, haemoglobin, haematocrit and total plasma albumin declined, while total white blood cells and proportion of lymphocytes to granular leucocytes rose. This indicated that this period was one of change in condition for this species. Compared to adult females, adult males were larger and heavier, had higher values of haematocrit and lymphocytes, and lower values of granular leucocytes, free steroids, CBGBd and albumin bound corticosteroid. There was considerable between-year variability in condition of individuals and both sexes differed significantly in September 1981 and 1982 in their weight, haematocrit, total white blood cells, granular leucocytes, MCBC and testosterone. Individuals at disparate localities at the Mitchell Plateau showed similar seasonal physiological and physical responses, except for one grid where they were heavier.

The reproductive cycle of female Eptesicus regulus is outlined from histological techniques on museum specimens collected in south-western Australia over the last 15 years. E. regulus is monoestrous and gives birth to a single young in November or December. It copulates in autumn and stores sperm over winter. Ovulation and fertilization is at the end of winter. Both ovaries are functional but pregnancy occurs only in the right horn.

Reproductive organs of female C. gouldii and changes in the ovaries, uterine horns, corpus uteri and vagina during the reproductive cycle are described. In the south-west of Western Australia, C. gouldii is monoestrous with pro-oestrus from January to March or April. Females are inseminated at the beginning of winter (a late winter insemination may also occur). Sperm is stored over winter in the core of a vaginal plug, in uterine glands, and in the uterine part of the oviducts. Ovulation and fertilization begin at the end of winter, from two to nine ova being shed from each ovary. Corpora lutea may be deeply embedded in the ovaries and ovulation apparently causes considerable break-down of capillaries at the point of rupture. Pregnancies occur in both horns and twinning is the rule. Gestation lasts about 3 months. After parturition there is a rapid involution of uterine horns and vagina, followed by a brief lactation anoestrus. The beginning of the period of births varies with latitude. In the south-west region it commences late November or early December; in the central region late (and possibly early) October or early November; in the northern region late September or early October.

This paper presents the background for a series on the biology of small mammals in the Mitchell Plateau region, an area characterised by a wet-dry tropical climate. From June 1981 to December 1982, 19 species of small terrestrial mammals were captured at Mitchell Plateau. Of 17 species captured on eight mark-release grids, 13 clustered into four significant groups which reflected the major habitats of the region: (1) Sminthopsis virginiae, Leggadina sp. and Pseudomys nanus in riparian and plateau escarpment sites; (2) Phascogale tapoatafa, Trichosurus arnhemensis and Pseudomys laborifex in plateau open forest; (3) Conilurus penicillatus and Mesembriomys macrurus in open woodland and coastal mosaics; (4) the commoner species Dasyurus hallucatus, Isoodon macrourus, Melomys sp. cf. burtoni, Zyzomys argurus and S. woodwardi in an array of habitats. Rattus tunneyi, Pseudantechinus sp., Wyulda squamicaudata and Planigale maculata did not cluster significantly with other species. Two species, Pseudomys delicatulus and Mesembriomys gouldii, were represented by single specimens captured outside the capture-mark-release grids, in sandstone and plateau woodland respectively. Open forests, particularly on the lateritic plateau surfaces, had the richest and most diverse mammal assemblage over the entire study period. The vine thickets and sandstone contained relatively stable populations of fewer species, and several habitats had seasonally variable populations and species.

Phenetic and phylogenetic analyses of skull morphology for 14 geographic groups of Ningaui indicate the existence of three species. Within species, both classifications show decreasing morphological similarity with increasing separation of geographic groupings. Sexual dimorphism is marked within each species. Discriminant analysis allows accurate identification of individuals to a species by means of skull characters, although this is not possible from external body characters.

The reproductive cycle of female T, australis is outlined from examination of reproductive organs in situ and from histological techniques on museum specimens collected in Australia, south of latitude 22S., over the last 88 years. Features of the reproductive tract and ovaries during important repro- ductive phases are described. There is a marked asymmetry of the reproductive organs, only the right ovary and uterine horn being functional. T. australis is monoestrous; there is no indication of marked differences in the timing of reproductive phases between regional populations. A single, deeply embed- ded corpus luteum occupies up to 60% of the ovary and degenerates at about the time of parturition. Apparently, most females, including young of the year, become pregnant each year, and give birth to a single young, usually between mid-December and late January, although occasionally as late as the end of February. Most young are weaned by early May. There is a short anoestrus, which is probably restricted to early lactating females, followed by a relatively long pro-oestrus. Copulation, ovulation and fertilization occur around late August. There is no evidence of hibernation.

Individual adult quokkas in the field were studied in relation to their choice of shelter sites on hot summer days and to their physiological response to heat stress and physical condition. Metabolic rate, evaporative water loss and rectal temperature were measured under laboratory conditions. The extent to which male quokkas moved to better shelter on hot days is significantly and positively correlated with their metabolic rate at T*a 37C; movement of females is significantly but negatively correlated with their rectal temperature. It is concluded that individual quokkas moving more frequently to better shelter on hot days (males) were physiologically less able to tolerate heat stress. Indices of physical condition and indicators of health and age were not correlated with movement. It is suggested that physiological variation in quokkas, both between and within sexes, effectively reduces intraspecific competition for a limiting resource (shelter). This expands their realised niche, increasing the carrying capacity of their environment.

The reproductive cycle of C. morio is outlined from examination of reproductive organs in situ and from histological techniques on Museum specimens collected in south-western Australia over the last 46 years. Changes in ovaries, endometria (and glands), epithelia lining tracts and Bartholin's glands are described. C. morio is monoestrous. It copulates in autumn and stores sperm in oviducts and uterine glands until ovulation in winter. Both ovaries are functional. Trans-uterine migration of the developing zygote is recorded. It normally gives birth to a single young, although occasionally to twins, between mid-September and mid-November. In the case of twins both uterine horns are gravid, otherwise only the right horn is gravid.

Analyses of morphological divergence in male and female Eptesicus in Western Australia are detailed. Phenetic differences between individuals at each locality, or nearby groups of localities, are examined for males and females separately, by canonical variate analysis. Populations can be roughly grouped into those of the South-west, North-west-Desert, Pilbara, Kimberley and the Peninsulas. Trends are evident from the analysis of the regional data for external morphological measurements. The South-west populations are referable to Eptesicus regulus Thomas, 1906. The moderately large Northwest-Desert populations are considered part of a general cline of Eptesicus pumilus extending north through the intermediate-sized Pilbara populations to the small Kimberley populations. The Peninsula populations have their greatest phenetic affinities with Eptesicus douglasi. In all populations examined, female Eptesicus tend to be larger than males.

The reproductive and associated organs of both male and female T. georgianus are briefly described. In females, only the right ovary is functional and pregnancies occur only in the right horn. They are monovular and the corpus luteum occupies most of the ovary and is deeply embedded in its stroma. Females are monotocous and the gestation period is probably about 4 months, young being born from October to February. They are monestrous and there is an autumn and early winter dioestrousanoestrous period. Spermatozoa are not stored in the reproductive tract of females and copulation appears to coincide with the oestrous condition. In males, spermatogenesis proceeds throughout the year and spermatozoa are present in the epididymis and vas deferens in all months that males were collected (no records for December). Spermatozoa are also found in the ampulla of Henle and vesicula seminalis in most months of the year. The position of the testes varies with season: in summer they descend to the scrota1 sacs; in autumn, winter, and spring they are more abdominal.

Quokkas aggregate about the patches of vegetation providing them with shelter. As days become hotter some quokkas cool themselves by moving from bushes that have a high heat load to those with a lesser one. Of the bushes with lower heat loads, the quokkas prefer those that are slightly hotter but which have drier atmospheres. Juveniles move to bushes with lower heat loads on more hot days than adults, and adult males move on more hot days than adult females. In the field, quokkas have a well-developed social organization in which adult males are dominant and adult females and juveniles have no social rank. Males form a linear hierarchy in which the older adults rank higher than the younger. Male quokkas defend a personal space and this defence is most marked in the vicinity of their rest sites. The social status of individual quokkas does not appear to determine the type of shelter they use on hot days. Numbers of quokkas in the study area increased when shelter was added experimentally during later summer, which shows that shelter is a limiting resource.