scholarly journals Studies on the Sex-Ratio and Related Phenomena

1926 ◽  
Vol 4 (1) ◽  
pp. 93-104
Author(s):  
A. S. PARKES
Keyword(s):  
Seasonal Variation ◽  
Sex Ratio ◽  
Recent Work ◽  
Litter Size ◽  
Annual Variation ◽  
Average Litter Size ◽  
Average Size

(1) 1872 normal mice bred during November 1922-October 1925 had an average litter-size of 6.18, and a male percentage of 51.7 ± .77, both of which figures are lower than the corresponding ones found for 1921-2. (2) The annual variation in the sex-ratio is, however, not very appreciable, the figures for the four years running 54.2 ± 1.04, 50.4 ± 3.22, 52.2 ± 1.18, 51.4 ± 1.09. The average size of litter during these four periods ranged from 6.65 to 5.93. (3) Considerable seasonal variation in both fertility and sex-ratio occurred, the highest figures being fertility 6.46 and male percentage 55.9 ± 1.83 in the October-December quarter, and the lowest being fertility 5.82 and male percentage 48.2 ± 1.46 in the April-June period. (4) Litter-size appeared to be uncorrelated with any sort of definite variation in the sex-ratio. (5) Recent work on the mouse is discussed.

scholarly journals Effect of inbreeding on fertility traits in five dog breeds

2019 ◽  
Vol 64 (No. 3) ◽  
pp. 118-129 ◽  
Author(s):  
Joanna Kania-Gierdziewicz ◽  
Sylwia Pałka
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Fixed Effects ◽  
Female Offspring ◽  
German Shepherd ◽  
Male And Female ◽  
Litter Traits ◽  
Average Litter Size ◽  
Inbreeding Level ◽  
Fertility Traits

The aim of the study was to analyze retrospectively the influence of inbreeding on fertility traits in five dog breeds: German Shepherd dog (GSD), Golden (GR) and Labrador (LR) Retrievers, Beagle and the Tatra Shepherd dog (TSD). The data were 436 litters, with the total of 2560 puppies: 1307 males and 1206 females. The parents of the litters were 163 dogs and 228 bitches. For each litter the litter size, number of male and female puppies, sex ratio, and sex difference were calculated. The fixed effects of breed, of litter birth year and linear regression coefficients on litter and parents’ inbreeding were included in the linear model for litter traits. The correlations between litter traits and litter parents’ inbreeding were also estimated. The average litter size was 5.87 (± 2.53) for all breeds. GSD had the smallest average litter size differences in years and the lowest fluctuations of sex ratio with litter size. In other dog breeds those differences were much bigger. The difference between the number of male and female offspring in a litter depended on the breed. The lowest percentage of inbred parents was found for LR, and the highest for TSD. Mating non-inbred animals, in most cases also unrelated, was frequent in all breeds. The inbreeding level of parents had significant influence on the litter traits only for TSD. For the Beagles low, positive and significant correlation between the number of female offspring in a litter and the dam’s inbreeding level and the sex ratio below 0.5 suggests sex ratio disturbance. The correlation coefficients between litter inbreeding and litter size for majority of examined dog breeds were positive but not significant. The conclusion is that in Poland at first obligatory monitoring of the inbreeding level for all breeds should be applied.

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 Intensive Breeding of Rats 1. Crossfostering

1968 ◽  
Vol 2 (1) ◽  
pp. 35-39 ◽  
Author(s):  
W. Lane-Petter ◽  
Marjorie E. Lane-Petter ◽  
C. Wendy Bowtell
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Average Litter Size ◽  
Intensive Breeding ◽  
Weight For Age

The sex ratio of CFE rats as born is approximately 1:1, but the demand is usually for many more males than females. Litter size as born is variable, with resulting variation in weight for age at weaning and subsequently. The average litter size born is lower than that which the dams are capable of rearing. By a system of crossfostering pups at about two days of age, and killing surplus female pups at this age, litter size may be standardized, the sex ratio of animals raised can be adjusted to the demand, and larger litters can be reared.

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

Seasonal Variation in Litter Size of the Meadow Vole in Southern Ontario

1963 ◽  
Vol 44 (4) ◽  
pp. 467 ◽  
Author(s):  
Edward Kott ◽  
William L. Robinson
Keyword(s):  
Seasonal Variation ◽  
Litter Size ◽  
Meadow Vole ◽  
Southern Ontario

REPRODUCTIVE POTENTIAL AND SEX RATIOS OF SNOWSHOE HARES IN NORTHERN ALBERTA

1956 ◽  
Vol 34 (4) ◽  
pp. 273-281 ◽  
Author(s):  
Wm. Rowan ◽  
L. B. Keith
Keyword(s):  
Litter Size ◽  
Sex Ratios ◽  
Reproductive Potential ◽  
Post Mortem ◽  
Comparable Data ◽  
Snowshoe Hares ◽  
Average Litter Size ◽  
Northern Regions ◽  
Two Factors ◽  
Northern Alberta

In conjunction with studies of the "10-year cycle" of snowshoe hares, almost 900 hares were collected in the Anzac district of Alberta during the period May, 1949, to April, 1956. Embryo numbers and sex ratios were among the data gathered from post-mortem examinations of these hares. It was found that the average litter size was 3.82; the modal litter size was four and the range was from one to seven. The average number of litters each season was calculated at 2.75. The annual reproductive potential is thus 10.51 (3.82 × 2.75) young per female hare. This is more than 50% greater than that indicated by comparable data from Minnesota. It is suggested that herein lies the cause of higher peak populations in northern regions. Sex ratios shifted from a marked excess of females in the year 1949–1950 to about even numbers of both sexes during the two subsequent years. Since the change in sex ratio occurred at the peak of the cycle, the two factors are believed to be in some manner correlated.

Development of a Strain of Rabbits with Congenital Simple Nonsyndromic Coronal Suture Synostosis Part I: Breeding Demographics, Inheritance Pattern, and Craniofacial Anomalies

1994 ◽  
Vol 31 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Mark P. Mooney ◽  
H. Losken Wolfgang ◽  
Michael I. Siegel ◽  
Janice F. Lalikos ◽  
Albert Losken ◽  
...  
Keyword(s):  
Litter Size ◽  
Rabbit Model ◽  
Pedigree Analysis ◽  
Human Populations ◽  
Incomplete Penetrance ◽  
Coronal Suture ◽  
Inheritance Pattern ◽  
Average Litter Size ◽  
Midfacial Hypoplasia ◽  
Congenital Condition

The lack of an animal model of congenital coronal suture (CS) synostosis has prompted the widespread use of an experimental rabbit model using adhesive Immobilization of the CS. Such postnatal models have helped make significant scientific contributions but may still not fully represent all aspects of the human congenital condition. In the March 1993 issue of The Cleft Palate-Craniofacial Journal we reported a female rabbit born in our laboratory with complete bilateral CS synostosis. This follow-up study presents our attempts to breed this animal and establish a strain of cranlosynostotic rabbits. To date, we have accomplished 10 back- and intercrosses with these animals and have produced a total of 71 live offspring; 10 animals exhibited complete nonsyndromic unilateral (plagiocephalic) or bilateral (brachycephalic) CS synostotic deformities at birth, and 19 animals exhibited partial CS synostosis that showed more than 75% growth retardation across the CS (well below the 95% confidence interval for normals). Results revealed that gestational time and litter size averages were consistent with those reported for the strain, although the average litter size decreased with increased inbreeding. By 1.5 weeks of age the completely synostosed animals already exhibited brachycephalic cranial vaults and midfacial hypoplasia compared to unaffected siblings. Initial pedigree analysis suggested an autosomal dominant inheritance pattern with incomplete penetrance and variable expressivity. The development of such a congenital rabbit model may prove useful In helping to understand the etiopathogenesis of this condition In human populations.

scholarly journals Seasonal variation in the sex ratio of Arctodiaptomus salinus (Copepoda: Calanoida): does it agree with the “cheaper-sex” hypothesis?

2014 ◽  
Vol 36 (6) ◽  
pp. 1413-1418 ◽  
Author(s):  
Raquel Jiménez-Melero ◽  
Juan Diego Gilbert ◽  
Francisco Guerrero
Keyword(s):  
Seasonal Variation ◽  
Sex Ratio

Characterization of Western Painted Turtle Bycatch in Fyke Nets During Freshwater Fish Population Assessments

2015 ◽  
Vol 7 (1) ◽  
pp. 222-230 ◽  
Author(s):  
Tyrel S. Moos ◽  
Brian G. Blackwell
Keyword(s):  
Sex Ratio ◽  
Freshwater Fish ◽  
Significant Relationship ◽  
Annual Variation ◽  
Size Structure ◽  
Fish Population ◽  
Painted Turtle ◽  
Nontarget Species ◽  
Catch Rates ◽  
Fyke Nets

Abstract In fisheries management, fish populations are assessed using various net types that invariably also capture nontarget species. Although the bycatch of turtles tends to be a common occurrence, data describing the bycatch of turtles during freshwater fish sampling are lacking. To improve the available knowledge base concerning the bycatch of turtles during fish sampling, we characterize the dynamics of western painted turtle Chrysemys picta bellii bycatch in unbaited modified fyke nets used in fish population sampling in northeastern South Dakota. We collected data from June to September during fish population assessments in 39 lakes and nine impoundments between 2007 and 2012. We characterize western painted turtle bycatch relating to water type (lake and impoundment) including catch rates (number of turtles/net night), size structure, and sex ratio. Catch rates were higher in impoundments than lakes. Total mean annual catch rates ranged from 1.07 to 3.28 for lakes and from 0.70 to 6.63 for impoundments and the variation among years was significant for both water types. We observed no annual variation in water surface area or mean depth, precluding either from explaining the variation in annual catch rates. We observed a significant relationship between mean depth and catch rate for lakes, but not impoundments. We observed no significant relationship relating surface area to catch rate for lakes or impoundments. Catch rates differed significantly from June to September for lakes but not impoundments. Annual variation in catch rates was best explained by the previous winter precipitation for both water types. The sex ratio was skewed toward males and differed significantly from June to September for lakes but not impoundments. The size structure was skewed toward large turtles. Understanding bycatch dynamics during fish population assessments is a critical first step to understanding the impact of biological sampling on nontarget species and may prove useful in minimizing future bycatch of western painted turtles.

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