Observations on social relations between territorial adult male and adult female A. forsteri were made on the Open Bay Islands, Westland, New Zealand, during the breeding season 1970-71. Threats comprised about 80% of all social encounters between males and females. Attempted and successful olfactory investigations of females by males, herding of females by males, and 'peace-keeping' by males accounted for about 18% of all encounters, and such interactions usually had agonistic overtones. Less than 2% of all encounters were not agonistic from their inception. Herding responses of males were vigorous and frequent, and are interpreted as serving two functions: containment of females and communication of certain of the herding males' characteristics to the females. Because herding occurs throughout the Otariidae, and is rarely effective in containing females, the second function is probably more important. Males showed much individual variation in their herding tendencies. The frequency of herding behaviour was depressed at warm temperatures. Olfactory investigations of facial and perineal regions of females were common and were not restricted to peri-oestrous females. Only oestrous females were sexually receptive to and showed little aggression toward territorial males, and males detected their physiological state mainly through olfaction. A few oestrous females solicited males with mock threats or by rubbing against them. Precopulatory and early copulatory behaviour was characterized by a moderate amount of mutual contact-seeking behaviour, multiple mounts by the male, and 'activation' of the female by the male biting her. Copulations appeared to be terminated through physical resistance by the female, which resulted in ejaculation and subsequent dismounting by the male. At the time of female resistance, the male commonly had to physically control her. The sudden return to aggressive behaviour typical of non-oestrous females may be mediated through a neural inhibitory process resulting from cervico-vaginal stimulation, as has been proposed for the guinea pig.

The effects of thyroid suppression induced during the rearing period by providing various dietary thiouracil (TU) regimens on plasma thyroxine (T4) concentrations, growth, and subsequent egg production (EP) and eggshell quality were determined in Single Comb White Leghorn chickens. Thiouracil was provided in the feed at levels of 0, .1, and .2% from 0 to 6 wk of age in Experiment 1, and at levels of 0, .05, and .1% from 6 to 16 wk of age in Experiment 2. In both experiments, T4 concentrations were reduced during TU treatment. However, T4 later became elevated at 12 and 20 wk in both dosage level groups in Experiment 1. Additionally, BW and egg weights were suppressed by both TU treatments, and EP was reduced up to Week 23 in the .1% TU-treated birds and through Week 25 in the .2% TU-treated birds. No effects on EP were noted in Experiment 2, but feed consumption (FC) was reduced during Week 6 in birds fed .05% TU and during Weeks 6, 10, and 19 in birds fed .1% TU. Both liver and thyroid weights were increased in .1% TU-treated birds relative to controls at Week 16. Eggshell quality was affected only in Experiment 2, in which birds given .05% TU had a higher relative conductance, or maximum rate of water loss, at Week 38 than 0 and .1% TU dosage levels, and .1% TU-treated birds had a higher breaking strength than 0 and .05% TU-treated birds at Week 22.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of consecutive exposures to dietary thiouracil (TU) in juvenile and adult Single Comb White Leghorn chickens on plasma thyroxine (T4) concentrations, egg production (EP), egg weight (EW), concentrations eggshell quality were determined. Thiouracil was provided in the feed at levels of 0, 0.1, or 0.2% (PTRT) from 0 to 6 wk of age and at levels of 0 or 0.1% (TRT) from 32 to 38 wk of age. Body weight gain was simulated but T4, EW, EP, and eggshell quality were generally reduced by 0.1% TU TRT. However, TU PTRT alleviated a latent depressing effect of TU TRT on BW after 38 wk of age. Thiouracil PTRT, particularly at the 0.2% level, induced significant decreases in EW but increased EP between 32 and 50 wk. The effects of early thyroid suppression in juveniles with TU PTRT on the subsequent reproduction of adults were primarily in response to a delay in the onset of sexual maturity, and not directly to prolonged responses in T4 or BW that extended into lay.

Because ascorbic acid (AA) and the thyroid hormones are known to influence eggshell formation, the effects of AA on body weight, total plasma thyroxine (T4), egg production, and eggshell quality of Single Comb White Leghorn (SCWL) hens concurrently and previously treated with thiouracil (TU) were determined. Hens were provided feed containing either 0 or 100 ppm AA from 47 to 67 wk of age and either 0 or .1% TU from 47 to 57 wk of age. A three-way split-plot analysis was employed to test for the effects of AA, TU, and time, and their interactions. Dietary TU increased body weight between 53 and 59 wk, and increased thyroid weight at 67 wk; however, TU only depressed plasma T4 level at 51 wk. Dietary TU depressed egg production from 50 to 56 wk and egg weight at 49, 51, and 57 wk. Dietary TU depressed eggshell weight per unit surface area at 49 wk. There was no significant effect due to AA and no AA by TU interaction for any of the parameters examined. It was concluded that .1% dietary TU from 47 to 57 wk of age did not alter eggshell quality and that dietary AA at the 100 ppm level did not influence the effects of .1% TU on body weight, egg production, or egg weight of SCWL hens.