Psychobiological studies of social behavior in Aves. I. The effect of complete and incomplete gonadectomy on the primary sexual activity of the male pigeon.

Abstract

A time-limited systematic observational technique with uniform optimal situations for expression of sexual behavior was used, eliminating all possible subjective factors. In A-tests, members of each pair were separated for a time before observation, but not in B-tests. Ready mated pairs of known sexual phase were observed, undisturbed, at the same time each day, after hunger and thirst were satisfied. Primary sexual activity includes copulation + associated adjustments; secondary, a group of social integrated activities correlated temporarily with, and probably provocative of, copulation (billing, preening, charging, and wing-plucking, which precede copulation). No seasonal cycles were found. A cycle of about 35 days had 5 stages, mating, nest-building, laying (taking 10.3 days), brooding (15.6 days), rearing young (to about 30 days of age). Tests covered mating, nest-building, and first phase of laying, while primary and secondary sexual activities were dominant. I. Complete or partial castration did not change overt primary sexual behavior pattern, in the age groups studied. Reduction to 15% of normal testis tissue failed to preclude normal frequency and vigor of sexual behavior, but, below that, frequency of copulation was somewhat reduced, gradually, not suddenly. Partial castration below a critical range delayed development of sexuality, both primary and secondary. Mean frequency of copulation and amount of residual testis tissue correlated +0.21 [plus or minus] 0.11 (N = 23), and 65% of "complete castrates" showed minimal primary sexual behavior. "Provocative scores" distinguished normal, partial, and complete castrates. Duration of "provocative period'' correlated with frequency of copulation [long dash]0.81 [plus or minus] 0.04. So length of "provocative period" and frequency of copulation were taken to be "indicative of degree of sexual motivation" in male pigeons (a truism ?).[long dash]II. Partial and complete castration, in increasing order, tended to dissociate, temporarily, billing from copulation, and reduced billing frequency, but did not essentially change the form of billing pattern nor eliminate it completely except in 3/14 of "complete castrates." This behavior as a whole was compensated for by increased aggressiveness of [female][female] associated with some partial and all complete castrates. Provocative scores of billing were increased by partial and complete castration and in normal birds they correlated with frequency scores,[long dash]0.61 [plus or minus]0.08 (N = 28X2 series). Hetero-preening was least, and charging most, affected by castration. Gonad fragments at autopsy were sometimes normal histologically, sometimes degenerated. Degeneration progressively affected spermatids, secondary spermatocytes, primary spermatocytes, spermatogonia, sperms embedded in Sertoli cells, and, finally, Sertoli cells. Regeneration and growth may recur after partial degeneration of testis fragments, which may enlarge after operation, and seminiferous tubules become divided by septa into "immature tubules." General increase of interstitials in partial castrates was rare. Interstitial tissue was most abundant in young adults; but all ages up to 5 years had some. Correlations between amounts of testis tissue recovered from partial castrates and frequencies of copulation and of billing were low but positive ( + 0.21, for copulation).