Observations on Variations in the Sex Ratios of Wild Rabbits, Oryctolagus cuniculus (L.), in Victoria

1981 ◽  
Vol 8 (2) ◽  
pp. 361 ◽  
Author(s):  
RCH Shepherd ◽  
JW Edmonds ◽  
IF Nolan
Keyword(s):  
Sex Ratio ◽  
Breeding Season ◽  
Oryctolagus Cuniculus ◽  
Sex Ratios ◽  
European Rabbit ◽  
Male Preponderance

There was a preponderance of females in wild rabbits collected in Victoria before 1974. This preponderance was established in subadults; in adults the sex ratio tended towards equality or a preponderance of males. The preponderance of females was most marked after the breeding season. A change to male preponderance in the Mallee region coincided with the establishment of the European rabbit flea.

scholarly journals Myxomatosis: the occurrence of antibody to a soluble antigen of myxoma virus in wild rabbits, Oryctolagus cuniculus (L.), in Victoria, Australia

1978 ◽  
Vol 81 (2) ◽  
pp. 245-249 ◽  
Author(s):  
J. W. Edmonds ◽  
Rosamond C. H. Shepherd ◽  
I. F. Nolan
Keyword(s):  
Breeding Season ◽  
Infection Rate ◽  
Oryctolagus Cuniculus ◽  
Myxoma Virus ◽  
European Rabbit ◽  
Soluble Antigen ◽  
Relative Timing ◽  
North West ◽  
The North ◽  
Semi Arid

SummaryThe occurrence of antibody to myxoma virus in wild rabbits following epizootics is highest in the semi-arid north-west of Victoria and lowest in temperate southern Victoria. Occurrence ranges up to about 90% in the north-west and to about 70% in the south except on the Western Plains where epizootics are rare and antibody occurrence seldom exceeds 30%.The establishment of the European rabbit flea may be changing the pattern of occurrence of antibody in the north-west by causing spring outbreaks of myxomatosis. It is suggested that the effects of the replacement of a simple recurring system of epizootic and breeding season several months apart by the occurrence of myxomatosis twice in the same year, once coincident with the breeding season, will be complex. The occurrence of detectable antibody may be less dependent on the infection rate and may be dependent to some extent on the relative timing of spring myxomatosis and the breeding season.

The Establishment and Spread of Spilopsyllus Cuniculi (Dale) and Its Location on the Host, Oryctolagus Cuniculus (L.), In the Mallee Region of Victoria.

1976 ◽  
Vol 3 (1) ◽  
pp. 29 ◽  
Author(s):  
RCH Shepherd ◽  
JW Edmonds
Keyword(s):  
Breeding Season ◽  
Oryctolagus Cuniculus ◽  
Myxoma Virus ◽  
The Body ◽  
European Rabbit ◽  
Initial Release ◽  
Breeding Seasons

European rabbit fleas (Spilopsyllus cuniculi) (Dale)) were released into a population of wild rabbits at 7 sites on Pine Plains in the Mallee district of Victoria, Australia, and their establishment and distribution observed monthly for 4 years. After 12 months, including one breeding season, the fleas were found on some rabbits up to 0.8 km from some release sites. By the end of the second breeding season, the distance of spread had doubled, and 4 years after the initial release, including 5 breeding seasons, about 95% of rabbits caught carried S. cuniculi. The furthest spread was about 13 km. When the initial release was made during the summer months, the non-breeding season, spread was slow; in one area, it took 2 years for S. cuniculi to become firmly established. When examples of S. cuniculi infected with myxoma virus were released, no establishment of the disease was observed. The numbers of S. cuniculi per rabbit were low during the first breeding season, but they were high, up to 500/rabbit, after 4 years. In most cases, the fleas were seen on the ears, pinnae and head of the rabbit and occasionally in the body fur. The highest numbers were usually found on pregnant lactating does about to litter, but some bucks also carried a large number.

scholarly journals Field studies of a Brazilian seahorse population, Hippocampus reidi Ginsburg, 1933

2008 ◽  
Vol 51 (4) ◽  
pp. 543-551 ◽  
Author(s):  
Natalie Villar Freret-Meurer ◽  
José Vanderli Andreata
Keyword(s):  
Sex Ratio ◽  
Home Range ◽  
Breeding Season ◽  
Protected Area ◽  
Rocky Shore ◽  
Sex Ratios ◽  
Field Studies ◽  
Reproductive State ◽  
Fixed Population

This study was carried out to fill the gaps that remain under Hippocampus reidi biology. Analysis of variations of sex ratio, density, breeding season, distribution and home range of a population of the endangered Brazilian seahorse H. reidi from a rocky shore on Araçatiba beach, Ilha Grande, Brazil were carried out. Araçatiba beach is a tourist Environmental Protected Area, suffering antropic pressure. A fixed population of H. reidi was studied, where al lthe individuals were visually tagged and sex, reproductive state and location on site were identified from December 2002 to November 2004. A total of 20 individuals were visually tagged with a mean density of 0.18 m-2. Sex ratios were skewed, with more females than males. All the males brooded during 13 months and presented smaller home range than the females during the breeding season. The highest densities were found on shallowest areas.

Observations on the dispersal of the European rabbit flea, Spilopsyllus cuniculi (Dale), through a natural population of wild rabbits, Oryctolagus cuniculus (L.)

1971 ◽  
Vol 19 (2) ◽  
pp. 129 ◽  
Author(s):  
RT Williams ◽  
I Parer
Keyword(s):  
Natural Population ◽  
Breeding Season ◽  
Oryctolagus Cuniculus ◽  
Social Groups ◽  
European Rabbit ◽  
Previous Suggestion ◽  
Rabbit Population ◽  
Data Support ◽  
Breeding Seasons ◽  
Time Away

The dispersal of the European rabbit flea, S. cuniculi, through a population of wild rabbits in a 550-acre enclosure was studied. It took 18 months (June 1968 until November 1969), and two rabbit breeding seasons before S, cuniculi was found throughout the population. The number of fleas observed on individual rabbits was much higher during each rabbit bieeding season than in the non-breeding periods. In most cases, the spread of fleas into the various social groups of rabbits occurred during the rabbit breeding season, and appeared to take the form of fleas from an infested group of rabbits being dispersed to a neighbouring uninfested one. This dispersal of S, cuniculi coincided with the dispersal of juvenile rabbits, which were most heavily infested with rabbit fleas at the end of each rabbit breeding season. Three instances of fleas being dispersed to non-neighbouring social groups of rabbits were observed, and these occurred between the 1968 and 1969 rabbit breeding seasons. It is possible that in these cases the fleas were introduced by the dispersal of adult rabbits from warrens infested with S, cuniculi. The data support a previous suggestion that these fleas, on a non-breeding rabbit population, spend most of their time away from the host. in the rabbit burrows.

Habitat and Warren Utilization by the European Rabbit, Oryctolagus cuniculus (L.),as Determined by Radio-Tracking

1981 ◽  
Vol 8 (3) ◽  
pp. 581 ◽  
Author(s):  
SH Wheeler ◽  
DR King ◽  
MH Robinson
Keyword(s):  
Breeding Season ◽  
Oryctolagus Cuniculus ◽  
European Rabbit ◽  
Native Vegetation ◽  
Radio Tracking ◽  
Radio Transmitters ◽  
Below Ground

'Rabbits equipped with miniature radio transmitters were located when at rest during the day at Cape Naturaliste, W.A. The study site was open pasture with numerous warrens, surrounded by and containing patches of native vegetation in which there were few warrens. Rabbits for instrumentation were live-trapped on the pasture and were located by radio once per day during each of four tracking periods in February, March-April (non-breeding season), May, and June (breeding season). A total of 31 individuals provided 284 locations, 263 (93%) of which were in the scrub. Of 216 locations in the scrub where the position of the rabbit (above or below ground) was known, 164 (765%) were above ground. Individual rabbits were found at several places within their resting areas, some of which were over 100 m into the scrub. The relevance of these results to current methods of rabbit control is discussed.

The ecology of the European rabbit (Oryctolagus cuniculus) in coastal southern Western Australia

1998 ◽  
Vol 25 (2) ◽  
pp. 97 ◽  
Author(s):  
Laurie E. Twigg ◽  
Tim J. Lowe ◽  
Gary R. Martin ◽  
Amanda G. Wheeler ◽  
Garry S. Gray ◽  
...  
Keyword(s):  
Breeding Season ◽  
Adult Female ◽  
Western Australia ◽  
Oryctolagus Cuniculus ◽  
European Rabbit ◽  
Demographic Changes ◽  
High Rainfall ◽  
Nonbreeding Season ◽  
Exponential Rates ◽  
Free Ranging

Demographic changes in three free-ranging rabbit (Oryctolagus cuniculus) populations were monitored over 4 years in southern Western Australia. Peak densities followed periods of high rainfall and pasture biomass. The breeding season was prolonged, often extending from at least April to November, with some pregnancies occurring outside this period. Fecundity, determined by the autopsy of pregnant offsite rabbits and the known length of each breeding season, appeared to be relatively high, with the potential for 34–39 kittens doe-1 year-1; however, because not all females are pregnant in all months, the overall productivity of these populations was estimated at 25–30 kittens adult female-1 year-1. Exponential rates of increase varied from 0.13 to 0.30 during the breeding periods and –0.05 to –0.14 during the nonbreeding season. Kitten survival was generally low whereas some adults lived for more than 5 years. Two patterns of myxomatosis were observed: annual epizootics of the disease (3 of 4 years) and an epidemic that slowly spread over many months. European rabbit fleas were most abundant during winter–spring and attained highest densities on adult female rabbits.

scholarly journals Sex-specific deaths in Norway and Sweden during the COVID-19 pandemic: Did mandates make a difference?

2021 ◽  
pp. 140349482110100
Author(s):  
Ralph Catalano
Keyword(s):  
Sex Ratio ◽  
Infection Control ◽  
Temporal Variation ◽  
Risky Behavior ◽  
Control Strategies ◽  
Sex Ratios ◽  
Female Mortality ◽  
All Cause Mortality ◽  
Societal Expectations ◽  
Male To Female

Aims: To determine whether differences between Norway’s and Sweden’s attempts to contain SARS-CoV-2 infection coincided with detectably different changes in their all-cause mortality sex ratios. Measuring temporal variation in the all-cause mortality sex ratio before and during the pandemic in populations exposed to different constraints on risky behavior would allow us to better anticipate changes in the ratio and to better understand its association with infection control strategies. Methods: I apply time Box–Jenkins modeling to 262 months of pre-pandemic mortality sex ratios to arrive at counterfactual values of 10 intra-pandemic ratios. I compare counterfactual to observed values to determine if intra-pandemic ratios differed detectably from those expected as well as whether the Norwegian and Swedish differences varied from each other. Results: The male to female mortality sex ratio in both Norway and Sweden increased during the pandemic. I, however, find no evidence that the increase differed between the two countries despite their different COVID-19 containment strategies. Conclusion: Societal expectations of who will die during the COVID-19 pandemic will likely be wrong if they assume pre-pandemic mortality sex ratios because the intra-pandemic ratios appear, at least in Norway and Sweden, detectably higher. The contribution of differences in policies to reduce risky behavior to those higher ratios appears, however, small.

scholarly journals Sex Ratios in a Warming World: Thermal Effects on Sex-Biased Survival, Sex Determination, and Sex Reversal

2021 ◽  
Vol 112 (2) ◽  
pp. 155-164
Author(s):  
Suzanne Edmands
Keyword(s):  
High Temperature ◽  
Sex Ratio ◽  
Sex Determination ◽  
Heat Tolerance ◽  
Sex Ratios ◽  
Sex Reversal ◽  
Survival Sex ◽  
Ratio Distortion ◽  
Warming World ◽  
Sex Ratio Distortion

Abstract Rising global temperatures threaten to disrupt population sex ratios, which can in turn cause mate shortages, reduce population growth and adaptive potential, and increase extinction risk, particularly when ratios are male biased. Sex ratio distortion can then have cascading effects across other species and even ecosystems. Our understanding of the problem is limited by how often studies measure temperature effects in both sexes. To address this, the current review surveyed 194 published studies of heat tolerance, finding that the majority did not even mention the sex of the individuals used, with <10% reporting results for males and females separately. Although the data are incomplete, this review assessed phylogenetic patterns of thermally induced sex ratio bias for 3 different mechanisms: sex-biased heat tolerance, temperature-dependent sex determination (TSD), and temperature-induced sex reversal. For sex-biased heat tolerance, documented examples span a large taxonomic range including arthropods, chordates, protists, and plants. Here, superior heat tolerance is more common in females than males, but the direction of tolerance appears to be phylogenetically fluid, perhaps due to the large number of contributing factors. For TSD, well-documented examples are limited to reptiles, where high temperature usually favors females, and fishes, where high temperature consistently favors males. For temperature-induced sex reversal, unambiguous cases are again limited to vertebrates, and high temperature usually favors males in fishes and amphibians, with mixed effects in reptiles. There is urgent need for further work on the full taxonomic extent of temperature-induced sex ratio distortion, including joint effects of the multiple contributing mechanisms.

scholarly journals Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1169-1180 ◽  
Author(s):  
Daven C Presgraves ◽  
Emily Severance ◽  
Gerald S Willrinson
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Operational Sex Ratio ◽  
Genetic Modifiers ◽  
Ratio Distortion ◽  
The Impact ◽  
Sex Ratio Distortion

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (Xd). Relatively high frequencies of Xd in C. dalmanni and C. whitei (13–17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of Xd. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with Xd, modifying Y chromosomes (Ym) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of Xd on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.

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