A study of some effects of increased population density on reproduction in two inbred lines of mice : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University of Manawatu, New Zealand
The Theory of Regulation of Reproductive Rate within Populations
The original hypothesis considered that soeiopsychological pressure
might act as a stressing stimulus in some proportion to population density,
which would activate the complex hypothalamo-hypophyseal-adrenocorticalgonadal
system (Selye, 1939, 1954; Harris, 1956). This proposal was based
on field data reported in the literature and on the results of experiments
in the laboratory with the pituitary-adrenocortical system.
A relationship between reproductive endocrine function and population
density was foreshadowed by Pearl and Surface (1909), who demonstrated
decreased egg production by domestic fowl with increased population size
even though the area per bird was kept constant. Crew and Mirskaia (1931)
and Retzlaff (1938) demonstrated a similar inverse relationship between
population size and reproductive performance in albino mice. These authors
recognized the importance of behavioural factors in producing these effects.
Retzlaff observed that socially dominant female mice gave the best
Selye (1939) demonstrated that stimuli evoking a response of the
pituitary-adrenocortical system also suppressed the reproductive function
of female rats. He postulated that the decreased reproductive activity
might result from a shift in pituitary function to produce an increased
amount of adrenocorticotrophin (ACTH) at the expense of the production
of gonadotrophins although an actual decrease in the production of
gonadotrophins was not shown.
[From the Introduction]