Some Population characteristics of Perameles gunnii in Victoria

1991 ◽  
Vol 18 (3) ◽  
pp. 355 ◽  
Author(s):  
AC Dufty
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Initial Point ◽  
Acid Soils ◽  
Ground Cover ◽  
Adult Mortality ◽  
Early Spring ◽  
Population Characteristics ◽  
Home Ranges ◽  
Juvenile Mortality

On the Australian mainland, the eastern barred bandicoot is now restricted to the city of Hamilton in western Victoria. Mark-recapture data from four main population areas, used in a Petersen index, gave a population estimate of about 134 individuals in 1988. When areas not sampled for population abundance were included, the total estimate of abundance for Hamilton was 246 individuals. Sex ratio was significantly male-biased for adults (68%), whereas the sex ratio for pouch young was about equal (45% male). The subadult age class constituted 8.2% of the captures, and accounted for only 10% of the total number of pouch young produced. Mean litter size was 2.11. The number of lactating females and the litter size were greatest during early spring. Eighty per cent of the offspring were produced in litters of 2 or 3. Nests were observed in various substrates, including man-made structures. Selected foraging areas had few native grasses, high ground cover, tall plant height and acid soils of low to medium compaction. Bandicoots were observed feeding on invertebrates, with some orchard fruits also being eaten. Foraging patches were actively defended. Adult home ranges of males (mean 12.94 ha) were larger than those of females (mean 2.38 ha). No female moved more than 150 m whereas males moved up to 2.3 km from their initial point of capture. The major cause of adult mortality observed was road kills. Life-expectancy is probably less than 2 years. Juvenile mortality was high.

Morphometrics, demographics, and genetic viability

2017 ◽  
Author(s):  
M.G.L. Mills ◽  
M.E.J. Mills
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Genetic Data ◽  
Adult Mortality ◽  
Healthy Population ◽  
Adult Males ◽  
Age At Death ◽  
Morphometric Data ◽  
Common Cause

Morphometric data showed that southern Kalahari male cheetahs are larger than females and coalition males are larger than single males. Both tend to be smaller than cheetahs from other regions. The estimated density was 0.7 adult cheetahs/100 km2. Adult males were either single (43.2%) or in two-male (35.8%) or three-male (20.9%) coalitions. Only two out of seven two-male coalitions were full siblings. Litter sizes at birth and emergence were similar to those in the Serengeti, but age at independence and at first litter were older, and litter size at independence larger. Cub sex ratio was equal, but there was a predominance of males amongst adults. Age at death was 6.7 ± 2.1 years, and the oldest known animal died at 12 years of age. The most common cause of adult mortality, especially for males, was injuries inflicted by conspecifics or competitors. Genetic data showed a stable and genetically healthy population.

Ecology of the western barred bandicoot (Perameles bougainville) (Marsupialia: Peramelidae) on Dorre and Bernier Islands, Western Australia

1998 ◽  
Vol 25 (6) ◽  
pp. 567 ◽  
Author(s):  
Jeff Short ◽  
J. D. Richards ◽  
Bruce Turner
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Substantial Reduction ◽  
Female Dominance ◽  
Home Ranges ◽  
Island Populations ◽  
Median Distance ◽  
Average Litter Size ◽  
Significant Difference ◽  
System Body

Population structure, reproduction, condition, movements and habitat preference were assessed for western barred bandicoots (Perameles bougainville) on Dorre and Bernier Islands over seven trapping sessions between 1988 and 1995. Data comes from 372 captures of bandicoots in 2535 trap-nights (an average of 14·7 captures per 100 trap-nights). Trap success was 5.7–25.8% on Dorre and 5.7–7.6% on Bernier. Recaptures within a trip made up 29% of bandicoot captures. The overall sex ratio (excluding recaptures) was skewed heavily towards males at 1.7: 1 for trapped animals, but varied between male and female dominance at any time according to reproductive status of females. Sex ratio of pouch young was 1.2: 1. Production of young was concentrated in the wetter winter months. The smallest western barred bandicoot with pouch young weighed 175 g. Bandicoots showed a pattern of increasing litter size with size of mother. Females with young had an average litter size of 1.8, with young reaching independence at about 100 g body weight. Large testes size relative to body size in males suggested a promiscuous mating system. Body condition could be predicted by sex (females were typically in better condition than males) and by rainfall over the previous 2 months. Some sexual dimorphism was evident, with females having longer heads and typically being heavier than males. There was no detected dimorphism between island populations. Movements of bandicoots appeared limited, with the median distance moved by animals captured more than once within a 9–11-day trapping session being 154 m. There was no significant difference in movements between the sexes, with males moving a median distance of 160 m and females 138 m within trapping sessions. The greatest movement by a male was 1020 m while the greatest distance moved by a female was 490 m. Only 13% of recorded movements were greater than 400 m. Home ranges overlapped, with 51% of traps catching more than one individual and as many as five males being caught at the same trap site. Bandicoots were widely dispersed through all habitats surveyed. Bandicoots appeared to suffer a substantial reduction in numbers on Dorre Island in a prolonged drought extending from October 1986 to April 1989, reducing overall trap success to less than 6% in the 1988 survey.

scholarly journals Reproductive performance in a cat colony over a 10-year period

1970 ◽  
Vol 4 (1) ◽  
pp. 99-112 ◽  
Author(s):  
Roy Robinson ◽  
H. W. Cox
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Reproductive Performance ◽  
Late Summer ◽  
Early Spring ◽  
Inverse Relation ◽  
Future Studies ◽  
Reproductive Life ◽  
Subsequent Loss ◽  
The Mean

Various aspects of reproductive performance in a cat colony are analysed in order to provide a basis for future studies. The aspects considered are: effect of mortality on litter size at different stages, and differential effect of losses on sex ratio of kittens reared; trend in litter size for successive parities; monthly variation in frequency of litters and litter size; output of kittens per queen per year. The sex ratio for live kittens was found to be 99.3 males per 100 females. Significant lower sex ratios of 65.6 and 79.7 were found in stillborn and in kittens which died between birth and weaning respectively. The mean litter size was 4.20 born (4.07 after deducting stillbirths), 3.65 at weaning. An inverse relation was found between incidence of stillbirths and subsequent loss before weaning. The mortality rate in each case was 1.5 kittens per affected litter. The mean litter size was smaller for the first litter but then increased to a constant 'plateau' until almost the end of the queen's reproductive life. Litters were produced throughout the year, but with greater frequency in the early spring months and again in the late summer. Litter size was greater in the summer months. Kitten mortality was lower in the summer than in the winter. A mean of 10.8 kittens were born per queen per year, and the mean number weaned was 9.4, representing a survival rate of 87 per cent.

Ambient Temperature and Rainfall: An Effect on Sex Ratio and Litter Size in Deer Mice

1985 ◽  
Vol 66 (2) ◽  
pp. 289-298 ◽  
Author(s):  
P. Myers ◽  
L. L. Master ◽  
R. A. Garrett
Keyword(s):  
Sex Ratio ◽  
Ambient Temperature ◽  
Litter Size ◽  
Deer Mice

Demography and home range of the eastern barred bandicoot (Perameles gunnii) in south-eastern Tasmania

2000 ◽  
Vol 27 (1) ◽  
pp. 103 ◽  
Author(s):  
Stephen A. Mallick ◽  
Michael M. Driessen ◽  
Gregory J. Hocking
Keyword(s):  
Body Weight ◽  
Sex Ratio ◽  
Home Range ◽  
Home Ranges ◽  
Sexually Dimorphic ◽  
South Eastern ◽  
Small Width ◽  
Live Trapping ◽  
Dry Conditions ◽  
Two Populations

We used live-trapping to study the demography and movement of two populations of the eastern barred bandicoot, Perameles gunnii, in south-eastern Tasmania from 1992 to 1996. Densities were 0.35–2.35 animals ha–1. Sex ratios were male-dominated on Grid I and female-dominated on Grid II. The average body weight for sexual maturity was 700g for males and 680g for females, while the lowest recorded weight for a breeding female was 570g. Perameles gunnii was sexually dimorphic, with males having a greater body weight and pes length than females. Recruitment was 25.4–32.1%, residence 46.7–100.0%, and emigration 16.5–25.5% of the population. Three juveniles were recruited to the Grid I population, 55 to Grid II, with a steady decline in the number of juveniles recruited to Grid II over the four years of the study. Breeding occurred year-round. Mean litter size was 2.53, with 78.2% of all litters having either 2 or 3 young. Mean longevity for male and female P. gunnii was 7.91 and 10.54 months, respectively. Home ranges of males (4.29 ha) were significantly larger than those of females (2.34 ha), although this may represent a significant underestimate due to the small width of our grids (200m) relative to the home-range area. There was only moderate overlap (19.3%) between home ranges of males and females. The overlap between male/male home ranges (4.4%) was significantly less than the overlap between female/female home ranges (15.8%). Perameles gunnii carried both ticks and fleas, with flea infestation being significantly higher on Grid I than on Grid II. Both populations underwent a significant decline over the study period, apparently the result of the unusually dry conditions over the first 3 years of the study. A deterioration in conditions was associated with a steady loss of resident adults, declining recruitment of juveniles and an increase in the male/female sex ratio. The sex ratio of P. gunnii populations may provide a convenient index of habitat quality, with poor or deteriorating conditions apparently associated with a high or increasing numbers of males to females.

2006 Southern brown bandicoots Isoodon obesulus obesulus in Belair National Park.

2006 ◽  
Vol 28 (2) ◽  
pp. 147 ◽  
Author(s):  
K. J. Sanderson ◽  
J. Kraehenbuehl
Keyword(s):  
Litter Size ◽  
National Park ◽  
Rattus Rattus ◽  
Ground Cover ◽  
Control Program ◽  
Water Courses ◽  
Fox Control ◽  
North Western ◽  
Black Rats

A population of southern brown bandicoots (Isoodon obesulus obesulus) in Belair National Park (NP) and neighbouring areas was studied from 1995 to 2002. From 1997 to 2002, 181 bandicoots (91 females, 89 males, one unknown) were microchipped. Many animals were captured only once or twice, but data from a few animals showed that bandicoots may live up to four years. Breeding occurred year round, with a mean litter size from 33 litters of 1.8. Bandicoots were trapped close to water courses in areas with thick ground cover. Black rats (Rattus rattus) were active nocturnally in all areas of Belair NP which were trapped, and may be in competition with bandicoots for food and shelter resources. Bandicoots have recently been seen in north-western areas of Belair NP where they have not been seen in years. This expansion of their distribution in the park may be related to a translocation to this area in 1998 and a fox control program which has been carried out since 1988.

A quantitative assessment of the reproductive biology of Cyclonaias tuberculata (Bivalvia: Unionidae)

1995 ◽  
Vol 73 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Thomas M. Haggerty ◽  
Jeffrey T. Garner ◽  
George H. Patterson ◽  
Lannis C. Jones Jr.
Keyword(s):  
Sex Ratio ◽  
Reproductive Biology ◽  
Reproductive Performance ◽  
Quantitative Assessment ◽  
Late Summer ◽  
Early Spring ◽  
Short Term ◽  
Tennessee River ◽  
Early Fall

Two hundred and thirty-three purple wartyback unionids (Cyclonaias tuberculata) were collected approximately monthly over a 31-month period from Kentucky Reservoir (Tennessee river mile 201.3), Tennessee, between August 1988 and February 1991. An equal sex ratio and only one case of hermaphroditism were discovered. Histological examinations showed that spermatogenesis and oogenesis occurred throughout the year except during late summer and early fall. "Typical" spermatogenesis was most evident between May and July. Spawning occurred between early spring (March–April) and late summer (August). Brooding variation among females was shown by the presence of embryos in the suprabranchial chambers and gills between early April and late August. Brooding was short term, as indicated by mature larvae being found in the outer demibranchs between early July and late August. Full demibranchs were never found, possibly indicating that the study took place during years of poor reproductive performance.

Maximization of long-term productivity in a rat colony

1972 ◽  
Vol 6 (2) ◽  
pp. 203-206 ◽  
Author(s):  
N. T. Gridgeman ◽  
J. M. Taylor
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Albino Rats ◽  
Mathematical Treatment ◽  
Production Time ◽  
Time Curve ◽  
Intensive Breeding

Maximization of intensive breeding in the animal colony can be approached using a simple mathematical treatment of the production-time curve. It has been found that in a colony of specified-pathogen-free albino rats whose breeding dams were averaging litters of 11 at 6-week intervals, the stock should be entirely replaced at intervals of 27-28 weeks to maximize the output of weanlings. Some data on litter size and sex ratio are also presented.

Population effects of shrimp trawl bycatch on Atlantic croaker

2000 ◽  
Vol 57 (10) ◽  
pp. 2010-2021 ◽  
Author(s):  
Sandra L Diamond ◽  
Lindsay G Cowell ◽  
Larry B Crowder
Keyword(s):  
Negative Impact ◽  
Population Level ◽  
Adult Mortality ◽  
Atlantic Croaker ◽  
First Year ◽  
Population Declines ◽  
Micropogonias Undulatus ◽  
Population Growth Rates ◽  
Juvenile Mortality ◽  
Shrimp Trawl

We used stage-within-age based matrix models of Atlantic croaker (Micropogonias undulatus) in the Gulf of Mexico and the South and Mid-Atlantic bights to explore the population-level impacts of shrimp trawl bycatch on estuarine-dependent fishes and to investigate tradeoffs between directed adult fisheries and bycatch mortality. The Gulf model reflected a rapidly declining population, while the Atlantic population showed a modest decline. Elasticity analyses indicated that both populations were more sensitive to the summed survival of adults than first-year survival, particularly in the Gulf. Contrary to our expectations, bycatch mortality on late juveniles was not the most important factor affecting either population of Atlantic croaker, and this result was robust to uncertainty in both adult and late juvenile mortality estimates. Both populations were most sensitive to ocean larva mortality, followed by mortality of estuary larvae and adults in the Gulf and of early juveniles and adults in the Atlantic. Nonetheless, bycatch mortality did have a large negative impact on population growth rates, and reducing late juvenile or adult mortality by about 35% in the Gulf or 5% in the Atlantic should reverse population declines. Bycatch reduction devices currently in use can achieve these desired reductions.

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