Rattus colletti (Rodentia: Muridae) in the Australian wet-dry tropics: Seasonal habitat preferences,population dynamics and the effects of buffalo (Bubalus bubalis)

Population dynamics and habitat preferences of the dusky rat, Rattus colletti, were examined in the seasonal wetlands of the South Alligator River. Northern Territory, between late 1979 and 1982. Demographically, the species is characterized by short-term seasonal shifts between habitats superimposed on a longer-term irregular pattern of prolonged breeding and population irruption, followed by periods of relative rarity. These patterns are determined by the train of climatic events. The flexible life history strategy and movement patterns of R. colletti reflect fine-scale adaptation to a climatic regimen which is markedly seasonal, but also highly variable between years in the amount and temporal patterning of rainfall. The distribution of R. colletti amongst vegetation types is influenced by two sets of environmental factors, both reflecting a gradient in elevation, soil type and vegetation. The primary factors are vegetative cover and height, and the extent and duration of flooding; the secondary set comprises buffalo-induced features such as the degree of pugging and grazing. These factors are interrelated, and their relative importance to R. colletti varies greatly between seasons. Feral buffalo appear to exacerbate the harsh effects of the wet and dry seasons. The removal of these animals may ameliorate environmental conditions considerably, both temporally and spatially, resulting m generally higher, more stable and spatially less variable populations of R. colletti.     

Reproduction in the agile wallaby Macropus agilis (Gould) in the tropical lowlands of the Northern Territory: opportunism in a seasonal environment

The agile wallaby, Macropus agilis, abounds on the tropical lowlands of the Northern Territory (12° 30′-13°S). The climate is markedly monsoonal and has an annual mean rainfall of 135 cm. During the rainy season, much of the wallaby's major habitat, the extensive coastal plains adjacent to the rivers, becomes flooded. The agile wallaby breeds continuously in captivity but not necessarily so in the wild, although fecundity was very high indeed. Reproduction was more successful on fertilized, nitrogenous pastures of farmland than on grasses of lower nutritive value. Breeding declined least (5%) in the dry season droughts as pastures dwindled and dried out, and most (> 45% in one year) during the rainy season in bushland where the dry season feeding grounds were inundated. The more quickly that the open riverine plains were flooded after the rains began, the higher the loss of breeding and the mortality of pouch-young. The mortality rates of young were similar on both improved and native pastures, however, with only about 35% of new-born surviving to 7 months in the pouch. Wallabies on the improved pastures were at higher densities than on the native pastures which may have influenced that mortality. That females became anoestrous during pregnancy, subsequently gave birth but did not have the usual post-partum oestrus makes the agile wallaby similar to the desert red kangaroo, M. rufus, in its method of entering anoestrus. Also as in that species, anoestrous lactating females can return to oestrus later. The agile wallaby is only the second macropodid marsupial for which these adaptations have been described. Such an adaptation in a desert species has a clear reproductive advantage which is not obvious in this tropical macropodid. Unlike the agile wallaby, the Asiatic waterbuffalo, (Babulis babulus) and domestic cattle, (Bostaurus and B. indicus) which have been introduced to its range breed and give birth on the rains. Such is the reproductive pattern in the tropical ruminants of East Africa also. Seasonal breeding is phylogenetically possible in macropodid marsupials because southern species. M fuliginosus, M. Eugenii, M. r. rufogriseus and Setonix brachyunis, do so in the mediterranean environment there. They time their breeding so that young leave the pouch when pastures are flush after the winter rains. The suggested reason for these differences in breeding of macropodids is seasonal unpredictability. Despite the enormous difference in rainfalls, weekly variability in pasture growth throughout the year is actually the same in monsoonal northern Australia as in the desert, and greater than in southern Australia. Environmental unpredictability may therefore be as important as the overall level of pasture growth in determining reproductive strategies of macropodid marsupials. For the tropical agile wallaby, the unpredictability can cause an absolute shortage or absolute abundance of food in the usual dry season depending on the length of the rainy season and on unseasonal cyclonic weather. It can also cause a relative shortage of food in the rainy season due to flooding of the best feeding grounds. It is concluded that reproduction in the wild mainly depends on the quantity and quality of the food supply.     

BREEDING SEASONS OF BIRDS IN DECIDUOUS WOODLAND AT ZIMBABWE,RHODESIA, FROM 1970 TO 1974

Vernon, C. J. 1978. Breeding seasons of birds in deciduous woodland at Zimbabwe, Rhodesia, from 1970 to 1974. Ostrich 49:102-115.

The birds in Brachystegia woodland bred in the spring and 98% of 1645 breeding records occurred between September and November. 90% of the records, and 43 of the 71 breeding species, were of insectivorous passerines. The breeding seasons of individual species lasted for between less than two months to more than three months, and their peak breeding periods varied between early September and the middle of October. The breeding season started earliest in 1974 and latest in 1973, and the start of two species was related to the timing of leaf emergence of the dominant tree in the woodland and to rainfall the previous rainy season. Food supply may be the proximal factor influencing the onset of breeding.     

Distribution and abundance of magpie geese,Anseranas semipalmata,in the Alligator Rivers Region,Northern Territory

Aerial surveys from 1981 to 1984 were used to identify monthly changes in the abundance of magpie geese on Jive floodplains in the Alligator Rivers Region of the monsoonal Northern Territory, and ground surveys were conducted during the same period on one of the plains to provide more detailed distributional information. The aerial surveys showed that the Magela floodplain was inhabited by few geese during the wet season (November-March), but that numbers then increased to an estimated average peak of 80 000 in the late dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) exhibited a similar pattern, except that the peaks occurred 2–3 months before the end of the dry season and comprised many more geese (an estimated average of 350 000 birds). In contrast, geese were uncommon on the East Alligator floodplain except during the wet season, and densities and numbers were lower than on the three previous plains. The Cooper floodplain was occupied intermittently, and numbers and densities were always relatively low. Geese appeared to return from their breeding localities to the floodplains of the Alligator Rivers Region progressively during the dry season, concentrating first on the extensive Eleocharis swamps of the Nourlangie floodplain and then waiting out the remainder of the dry on the substantial permanent waters of the Magela floodplain and other nearby wetlands. Ground surveys on the Magela floodplain suggested that geese were highly mobile, apparently seeking suitable nesting habitat in the late wet season, and then a sequence of feeding areas during the dry season. Aerial surveys underestimated densities; on the basis of ground surveys, average peak numbers on the Magela plain were calculated to be 500 000. We estimate that the Alligator Rivers Region supported an average of about 1.6 million geese in the dry season, but very many fewer during the wet season.     

Breeding ecology of Kori Bustard Ardeotis kori strunthiunculus in the Serengeti National Park

The breeding ecology of the Kori Bustard Ardeotis kori strunthiunculus was studied in the plains of the Serengeti National Park, Tanzania in 2014 and 2015. Random transects were used to search for male courtship displays, nests, chicks and subadults. GPS satellite collars were used to locate nesting females. Linear regression analyses and post hoc tests were used to determine the predictors that contributed most to the variation of the dependent variables (courtship display, nest, chicks and subadults). The results indicate that courtship behaviour peaks during the short dry and short rainy season before the peaks in nests and chicks. The highest nest frequency was found in short grass habitats. Female Kori Bustard may undergo repeated nestings within a single breeding season. The adult sex ratio was female skewed during the breeding season. The Kori Bustard breeding season in the Serengeti plains is relatively long, lasting for almost nine months, and taking place during all seasons except for the long dry season. We recommend that management authorities conduct assessments of Kori Bustard recruitment as well as habitat suitability in the Serengeti ecosystem to develop future conservation strategies.     

Drought acclimation among tropical forest shrubs (Psychotria,Rubiaceae)

Summary Mechanisms of dry-season drought resistance were evaluated for five evergreen shrubs (Psychotria, Rubiaceae) which occur syntopically in tropical moist forest in central Panama. Rooting depths, leaf conductance, tissue osmotic potentials and elasticity, and the timing of leaf production were evaluated. From wet to dry season, tissue osmotic potentials declined and moduli of elasticity increased in four and five species, respectively. Irrigation only affected osmotic adjustment by P. furcata. The other seasonal changes in leaf tissue properties represented ontogenetic change. Nevertheless, they made an important contribution to dry-season turgor maintenance. Small between-year differences in dry season rainfall had large effects on plant water status. In 1986, 51 mm of rain fell between 1 January and 31 March, and pre-dawn turgor potentials averaged <0.1 MPa for all five Psychotria species in March (Wright 1991). In 1989, 111 mm of rain fell in the same period, pre-dawn turgor potentials averaged from 0.75 to 1.0 MPa for three of the species in April, and only P. chagrensis lost turgor. The relation between leaf production and drought differed among species. P. limonensis was buffered against drought by the lowest dry-season conductances and the deepest roots (averaging 244% deeper than its congeners) and was the only species to produce large numbers of leaves in the dry season. P. chagrensis was most susceptible to drought, and leaf production ceased as turgor loss developed. For the other species, water stress during severe dry seasons may select against dry-season leaf production.     

The effects of rainfall on different components of seasonal fecundity in a tropical forest passerine

Seasonal fecundity is a composite metric that is determined by component parameters such as clutch size, nest survival and re‐nesting probability. Many of these component parameters are known to vary with environmental conditions, in particular rainfall prior to or during the breeding season. In some species, seasonal fecundity is positively related to rainfall, but little is known about which component parameters of seasonal fecundity respond most strongly to rainfall. We used intensive nest monitoring of a multi‐brooded tropical forest passerine, the Montserrat Oriole Icterus oberi, to examine the effects of rainfall during the pre‐breeding season on component parameters of annual fecundity. We monitored all nests of a total of 42 pairs over 5 years in which rainfall varied substantially. We then related clutch size, nest survival, onset and length of the breeding season, re‐nesting probability and re‐nesting interval to pre‐breeding season rainfall using generalized linear mixed models that accounted for random variation across sites and individual pairs, and incorporated other variables known to affect the response. Higher pre‐breeding season rainfall led to an increase in clutch size and a decrease in re‐nesting interval, but nest survival, re‐nesting probability and length of the breeding season were not affected by variation in rainfall. The onset of the breeding season was delayed in very dry years. We conclude that higher rainfall is likely to increase food availability and thus body condition of female Montserrat Orioles, leading to an increase in fecundity due to larger clutch sizes.     

The biology of the ground beetle Harpalus rufipes in a strawberry field in Northumberland

Harpalus rufipes (Degeer) was studied in a strawberry plot in Northumberland from 1973 to 1978 by pitfall trapping, and in the laboratory. Adults were active from April until November. Overwintered male beetles predominated at the beginning of each season until May, followed by overwintered females in June and July. Newly emerged, mainly female, beetles were active from August onwards. Overwintered females matured during early summer and laid eggs in August with a fecundity of 10–15 eggs/female. In the laboratory about 30% of beetles survived from one breeding season to the next. First- and second-instar larvae were caught in pitfall traps in autumn; in the laboratory they made approximately vertical burrows in which they stored seeds taken from the soil surface. Third-instar larvae fed on these seeds and were not active on the surface. Preferred seeds were those of grasses and Chenopodium album L. Larvae were usually aggregated in the soil at densities of 3–20/m².     

The impact of experimental fire regimes on seed production in two tropical eucalypt species in northern Australia

Abstract This study investigated the effect of three experimental fire regimes on the fecundity, ovule development and seedfall of two common wet-dry tropical savanna eucalypts, Eucalyptus minima and Eucalyptus tetrodonta, in northern Australia. Both species flower early in the dry season and ovule development occurs during the dry season. This coincides with a period of frequent fires. The three fire regimes considered were applied for four years between 1990 and 1994. These regimes were (i) Unburnt, (ii) Early, fires lit early in the dry season, and (iii) Late, fires lit late in the dry season. The treatments were applied to nine catchments (15–20 km²) with each fire regime replicated three times. Fire intensity typically increases as the dry season proceeds. Therefore, early dry season fires generally differ from late dry season fires in both their intensity and their timing in relation to the reproductive phenology of the eucalypts. Late dry season burning significantly reduced the fecundity of both species, whereas Early burning had no significant effect. Ovule success was significantly reduced by the Early burning for both species. The Late burning significantly reduced ovule success in E. tetrodonta, but not in E. miniata. The results suggest that fire intensity and fire timing may both be important determinants of seed supply. Fire intensity may be a determinant of fecundity, whereas fire timing in relation to the reproduction phenology may have a significant impact on ovule survival. Both fire regimes resulted in a substantial reduction in seed supply compared with the Unburnt treatment. This may have a significant impact on seedling regeneration of these tropical savanna eucalypts.     

Rainfall and rats: Climatically-driven dynamics of a tropical rodent population

A five-year mark–recapture study of dusky rats (Rattus colletti) on the Adelaide River floodplain, within the Australian wet–dry tropics, revealed substantial spatial and temporal variation in demographic characteristics (abundance, condition, and rates of survival, growth, and reproduction) of the rats. Our data suggest that annual variation in the intensity and timing of monsoonal rainfall during the ‘wet-season’ is the main factor driving the demography of the rats. When total rainfall figures are modified to reflect the magnitude and duration of inundation of the floodplain each year, a link is evident between rainfall patterns and the rat population dynamics. Minor spatial variations in elevation (and hence, in the duration of inundation) across the floodplain engender large differences in rat growth rates, condition factors, survival rates, and the duration of reproductive activity each year. Because these rats have very high reproductive rates, small rain-induced differences in the duration of their reproductive season (i.e. number of litters per year) can cause massive differences in subsequent rat abundances. Hence, rat numbers can be predicted from rainfall patterns during the preceding wet-season. Similar links between rainfall, the duration of breeding, and fluctuations in abundance may typify many rodent populations in tropical and arid regions of the world.     

THE BREEDING OF HEUGLIN'S MASKED WEAVER AND ITS NESTING ASSOCIATION WITH THE RED WEAVER ANT

Grimes, L. G. 1973. The breeding of Heuglin's Masked Weaver and its nesting association with the Red Weaver Ant. Ostrich 44: 170–175.

The breeding season of Heuglin “s Masked Weaver Ploceus heuglini at Legon began in the latter half of the major dry season in January and February; continued through the main wet season and ceased in late August and for the rest of the year. The Accra colony had a similar breeding activity but in addition was active for a short period in November which had ended by mid-December. Although the majority of males formed colonies in which the number of males ranged from two to twenty, solitary breeding occurred equally frequently. Most males within the Legon colony, and possibly this is true for all colonies, were polygynous while most solitary males were monogamous. More nests were built by each male than the number of females involved in the polygyny.

A close nesting association with the Red Weaver Ant Oecophylla longinoda existed and the data suggested that the weaver sought the ant. Two cases were found of nesting association with the wasp Belanogaster grisens.     

Rat kappa-chain allotypes

The presence of rat kappa-chain allotype specificities (RI-1a and b) has been studied in 13 subspecies of the seven native Australian species ofRattus. RI-la reactivity was not detected among these rats. On the other hand, extensive cross-reactivity was seen with RI-1b, some sera cross-reacting totally (R. leucopus cooktownensis), some not at all (R. colletti), and the remainder showing at least two distinct levels ofpartial cross-reactivity, confirming the existence of multiple specificities for Rl-lb. Three subspecies show polymorphism with respect to Rl-lb cross-reactivity (R. sordidus, R. colletti, andR. l. leucopus) and in one case (leucopus) breeding studies have indicated that there is allelic inheritance of this trait. The segregation of RI-1b reactivity has been studied in crosses and backcrosses made between species differing in their RI-1b reactivity, and the results are consistent with the existance of codominant alleles at a single locus. The fact that these species differ extensively in their karyotype opens the door to possible chromosomal localization of this and other genetic traits.     

A surplus of seeds: High rates of post-dispersal seed predation in a flooded grassland in monsoonal Australia

Abstract Oryza meridionalis is an annual emergent wetland grass which produces between 26 and 260 kg seeds ha^-1 annually. Seed shed occurs at the end of the wet season, when the plains are usually still partially flooded. The juvenile recruitment of key native vertebrate species, such as the Magpie Goose (Anseranus semipalmata) and the Dusky Plains Rat (Rattus colletti), coincides with seed shed. This study investigated predation of O. meridionalis seeds at two sites on the South Alligator River floodplain in monsoonal Australia. The effects of inundation and the presence of a background density of seeds on seed removal were investigated by stratified sampling with respect to position down the topographic slope, to include the ‘dry’ floodplain margin, ‘damp’Oryza zone, and ‘flooded’Oryza zone. The effect of seed lot size on the proportion of seed removed was also investigated, and exclosures were used to identify the principal predator group. The proportion of seeds removed was not affected by the presence/absence of a background of seeds nor the number of seeds placed in experimental ‘lots’. The majority of seeds (75%) was consumed by vertebrate predators (most likely the abundant Dusky Plains Rat). Inundation afforded some protection from predation. Despite high losses of seeds exposed to predators, O. meridionalis is an abundant and widespread species on these floodplains, possibly because of the protection from predation afforded by inundation to those seeds which are shed into the water column. It is likely that there is a complex interaction between topography, rainfall and predator and prey relationships, which ultimately determines the importance of seed removal for the maintenance of populations of O. meridionalis. These high losses of seeds to predation have implications for wetland rehabilitation where seed broadcasting is proposed.     

POPULATION,DIET AND THE ANNUAL CYCLE OF THE LAUGHING DOVE AT BARBERSPAN,PART 4. BREEDING DATA AND POPULATION ESTLMATES

Dean, W. R. J. 1980. Population, diet and the annual cycle of the Laughing Dove at Barber-span, Part 4: Breeding data and population estimates. Ostrich 51:80-91.

From 1974–1976, Laughing Doves Streptopelia senegalensis raised an observed total of 436 young in 619 nest attempts, giving a breeding success of 0,70 young per pair nest attempt, or an overall success of 0,35 young per egg. Breeding success, estimated by computing the probability of survival of an egg through the incubation period, and of a chick through the nestling period suggest that the breeding success is about 0,33 young per egg. Nests were found in every month of the year, though there was a tendency for breeding to be concentrated during the late rainy season and the dry season. The mean annual population size of the Laughing Dove in the study area was estimated at 221 adults and juveniles by one method and at 237 adults and juveniles by another method. The number of young produced each year is correlated with the estimated population size for each year.     

Water resource partitioning,stem xylem hydraulic properties,and plant water use strategies in a seasonally dry riparian tropical rainforest

This study investigated seasonal variation in the origin of water used by plants in a riparian tropical rainforest community and explored linkages between plant water source, plant xylem hydraulic conductivity and response to the onset of dry conditions. The study focused on five co-dominant canopy species, comprising three tree species (Doryphora aromatica, Argyrodendron trifoliolatum, Castanospora alphandii) and two climbing palms (Calamus australis and Calamus caryotoides). Stable isotope ratios of oxygen in water (¹⁸O) from soil, groundwater, stream water and plant xylem measured in the wet season and the subsequent dry season revealed water resource partitioning between species in the dry season. Measurement of stem-area-specific hydraulic conductivity (K_S) in the wet season and subsequent dry season showed a significant dry-season loss of K_S in three of the five species (Castanospora alphandii, Calamus australis and C. caryotoides) and a decrease in mean K_S for all species. This loss of hydraulic conductivity was positively correlated with the difference between wet-season and dry-season midday leaf water potentials and with leaf carbon isotope discrimination, indicating that plants that were less susceptible to loss of conductivity had greater control over transpiration rate and were more water-use efficient.     

The cost of reproduction in the glaucous-winged gull

Summary Experimental enlargement of brood size in the glaucous-winged gull (Larus glaucescens) resulted in increased adult foraging time, decreased adult body weight at the end of the breeding season, and decreased over-winter adult survival. The decreased survival of breeding adults was associated with reduced body condition at the end of breeding (resulting from physiological costs of reproduction). Decreased survival was not due to an increased risk of injury or predation during the breeding season. Brood size did not directly affect the fecundity of surviving birds in the subsequent year. However, brood size may have an indirect effect on subsequent fecundity because the probability of mate loss increased among birds with large broods and the reproductive performance of birds with new mates was reduced. Based on estimates of life-time fitness calculated from fecundity and survivorship, birds with two- or three-chick broods (the normal brood size) have higher fitness than birds with one- or four-chick broods. However, the decreased fitness of birds with four-chick broods was slight, and probably not a sufficient explanation for the absence of natural four-chick broods in the glaucouswinged gull.     

Sex,reproductive cycle and variations in the fecundity of the family schilbeidae (Osteichthyes : Siluriformes) in Lake Kainji,Nigeria.

The sex, reproductive cycle and variations in the fecundity of the family Schilbeidae (Osteichthyes : Siluriformes) in Lake Kainji, were investigated. Sexual differences in size and morphology were found to exist in all species. Sex ratio varied with species and season. There were more females than males in the population. Size at maturity varied from species to species with the males attaining maturity at a slightly lower length than the females. Breeding condition was attained mainly during the rains in Eutropius niloticus, Schilbe mystus and Siluranodon auritus and in the dry and rainy seasons in Physailia pellucida. Spawning occurred once during the breeding season in E. niloticus and S. mystus; and more than once during the prolonged breeding season in P. pellucida. Condition factors did not show any correlation with maturation of gonads. Fecundity was found to vary from species to species.     

Physiological ecology of frillneck lizards in a seasonal tropical environment

The frillneck lizard, Chlamydosaurus kingii, is a conspicuous component of the fauna of the wetdry tropics of northern Australia during the wet season, but it is rarely seen in the dry season. Previous studies have demonstrated that during the dry season the field metabolic rate (FMR) is only about one-quarter of the wet-season rate, and one factor involved in this seasonal drop is a change in the behavioural thermoregulation of the species such that lower body temperatures (T _bs) are selected during dry-season days. Here we examine other factors that could be responsible for the seasonal change in FMR: standard metabolic rates (SMR) and activity. Samples from stomach flushing revealed that the lizards in the dry season continued to feed, but the volume of food was half as much as in the wet season. SMR in the laboratory was 30% less in the dry season. During the dry season, the energy expended by the lizards is 60.4 kJ kg^-1 day^-1 less than during the wet season. Combining laboratory and field data, we determined the relative contribution of the factors involved in this energy savings: 10% can be attributed to lower nighttime T _b, 12% is attributable to lower daytime T _b, 12% is attributable to decreased metabolism, and the remaining 66% is attributable to other activities (including e.g. locomotion, reproductive costs, digestion). Calculations indicate that if FMR did not drop in the dry season the lizards would not survive on the observed food intake during this season. Seasonal analysis of blood plasma and urine indicated an accumulation of some electrolytes during the dry season suggesting modest levels of water stress.     

SHORT NOTES

Earlé, R. A. 1981. Factors governing avian breeding in Acacia savanna, Pietermaritzburg, Part 3: Breeding success, recruitment and clutch size. Ostrich 52:235-243.

The clutch size and breeding success of eight species of birds were monitored over a two year period in Acacia savanna. The mean clutch size fluctuated within the breeding season and four patterns of clutch size variation were noted. A smaller proportion of large clutches were laid in the 1979 season when less food was available. Breeding success was higher in the dry 1979 season but fewer breeding attempts were made and the overall recruitment was thus lower. At the peak of the breeding season, in mid-November, breeding success was at its lowest. Predation on nests was the greatest factor reducing breeding success although rain and strong winds affected some species.     

Chromosome evolution in Australian rodents

A total of 219 wild caught specimens representing 12 of the currently recognised 13 species and subspecies of Australian Rattus have been karyotyped. No two species possessed karyotypes in common, most species and several subspecies differing markedly in chromosome number. While the diploid number varied from 2n=32 to 2n=50, the fundamental number (FN) varied only from 60 to 62, suggesting that Robertsonian rearrangements have played a major role in karyotypic evolution in the group. — Karyotypically the Australian species of Rattus fall into two groups. — the R. lutreolus group and the R. sordidus group. Of the karyotypic forms encountered in the former group, that of R. lutreolus is probably most ancestral because it is identical to that of many Asian species of Rattus. Other karyotypic forms in the R. lutreolus group can be derived as follows: That of (1) R. tunneyi tunneyi and R. t. culmorum by a single fixed pericentric inversion; (2) R. fuscipes fuscipes, R. f. greyi, R. f. assimilis and R. f. coracius by two fixed fusions; (3) R. leucopus cooktownensis by three fixed fusions; and (4) R. leucopus leucopus by four fixed fusions. Of the R. sordidus group, R. s. villosissimus may possess the most ancestral karyotype with 2n=50 (FN=60), from which R. s. colletti (2n=42; FN=60) is derived by four fusions and R. s. sordidus (2n=32; FN=60) by nine fusions, four of which appear to be homologous with those R. s. colletti. — The karyotypic data are in accord with Taylor and Horner's (1973) suggestions that (1) R. t. tunneyi and R. t. culmorum belong to one species; (2) R. lut. lutreolus and R. lut. velutinus belong to one species; (3) R. leu. leucopus and R. leu. cooktownensis belong to one species and (4) R. f. fuscipes, R. f. greyi, R. f. assimilis and R. f. coracius belong to one species. However, the large karyotypic difference between R. s. sordidus and R. s. colletti and R. s. villosissimus may indicate that these groups belong to different biological species. — Supernumerary or B-chromosomes were found in R. f. assimilis and R. t. tunneyi. A single R. t. culmorum was heterozygous for a centric fusion.