Offspring sex ratio in moose Alces alces in relation to paternal age: an experiment

Abstract Over a 14 year period, we determined offspring sex ratios in a population of Savannah Sparrows (Passerculus sandwichensis) breeding on Kent Island, an isolated 80 ha island in the Bay of Fundy, New Brunswick, Canada, based on morphological measurements of 318 independent juveniles and 361 returning adults of known parentage. The mean annual offspring sex ratio was exactly 1.00 (±0.23, range= 0.61–1.41, n = 14). In no year did offspring sex ratio deviate significantly from 50:50, regardless of the sex ratio of breeding adults. Offspring sex ratio did not vary as a function of the timing of breeding, maternal or paternal age, or parental mating status (monogamy vs. polygamy). Overall, our data provide strong support for 50:50 offspring sex ratios at the population level (Fisher 1930), but no support for the notion of adaptive modification of offspring sex ratios by individuals (Trivers and Willard 1973).

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Pregnancy and offspring sex ratio following insemination with SexedULTRA and conventional semen in cows in a commercial beef operation

Reproduction in Domestic Animals ◽

10.1111/rda.14008 ◽

2021 ◽

Author(s):

R. Kasimanickam ◽

V. Kasimanickam ◽

K Ratzburg

Keyword(s):

Sex Ratio ◽

Offspring Sex Ratio ◽

Offspring Sex

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Offspring sex ratio of subfertile men and men with abnormal sperm characteristics

Human Reproduction ◽

10.1093/humrep/15.11.2369 ◽

2000 ◽

Vol 15 (11) ◽

pp. 2369-2370 ◽

Cited By ~ 19

Author(s):

R. Jacobsen

Keyword(s):

Sex Ratio ◽

Offspring Sex Ratio ◽

Abnormal Sperm ◽

Sperm Characteristics ◽

Offspring Sex

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Offspring sex ratio in men exposed to electromagnetic fields

Journal of Epidemiology & Community Health ◽

10.1136/jech.2004.025304 ◽

2005 ◽

Vol 59 (4) ◽

pp. 339-339 ◽

Cited By ~ 5

Author(s):

M. Saadat

Keyword(s):

Sex Ratio ◽

Electromagnetic Fields ◽

Offspring Sex Ratio ◽

Offspring Sex

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Breeding system can affect the offspring sex ratio in Syrian hamsters

Laboratory Animals ◽

10.1258/la.2010.010099 ◽

2011 ◽

Vol 45 (1) ◽

pp. 55-57 ◽

Cited By ~ 3

Author(s):

M O M Chelini ◽

N L Souza ◽

E Otta

Keyword(s):

Sex Ratio ◽

Breeding System ◽

Offspring Sex Ratio ◽

Syrian Hamsters ◽

Offspring Sex

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Is biasing offspring sex ratio adaptive? A test of Fisher's principle across multiple generations of a wild mammal in a fluctuating environment

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.1251 ◽

2018 ◽

Vol 285 (1891) ◽

pp. 20181251 ◽

Cited By ~ 1

Author(s):

Andrea E. Wishart ◽

Cory T. Williams ◽

Andrew G. McAdam ◽

Stan Boutin ◽

Ben Dantzer ◽

...

Keyword(s):

Sex Ratio ◽

Tamiasciurus Hudsonicus ◽

Red Squirrels ◽

Offspring Sex Ratio ◽

Offspring Sex ◽

Adult Sex Ratio ◽

Secondary Sex Ratio ◽

North American Red Squirrels ◽

Negative Frequency Dependent Selection ◽

Fisher’S Principle

Fisher's principle explains that population sex ratio in sexually reproducing organisms is maintained at 1 : 1 owing to negative frequency-dependent selection, such that individuals of the rare sex realize greater reproductive opportunity than individuals of the more common sex until equilibrium is reached. If biasing offspring sex ratio towards the rare sex is adaptive, individuals that do so should have more grandoffspring. In a wild population of North American red squirrels ( Tamiasciurus hudsonicus ) that experiences fluctuations in resource abundance and population density, we show that overall across 26 years, the secondary sex ratio was 1 : 1; however, stretches of years during which adult sex ratio was biased did not yield offspring sex ratios biased towards the rare sex. Females that had litters biased towards the rare sex did not have more grandoffspring. Critically, the adult sex ratio was not temporally autocorrelated across years, thus the population sex ratio experienced by parents was independent of the population sex ratio experienced by their offspring at their primiparity. Expected fitness benefits of biasing offspring sex ratio may be masked or negated by fluctuating environments across years, which limit the predictive value of the current sex ratio.

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