The British Journal of Animal Behaviour最新文献

Twenty-two cockerels were scored singlyfor sexual activity in 2 pens of hens, and then scored for aggressiveness. Two measurements of aggression were obtained by observing each cockerel in 6 individual encounters with six special cockerels that had been trained to fight. These measurements were (i) the number of fights started with one fight per encounter, and fights started with one fight per encounter, and (ii) the time taken to start fighting in each encounter.

After the data had been examined for any possible conditioning effects on the 22 cockerels, the scores for aggression were found to be highly correlated with one another but not with the sexual activity of the male

The number of fights won, drawn or lost were also recorded and the fighting score of each male was found to be significantly correlated with the measurements of aggression, but not with sexual activity.

The cockerels were then divided into three groups, penned, and the peck order position of each cockerel determined. No correlation was found to exist between the peck order position of a cockerel and his score for sexual activity. The practical implications of this are discussed.

The development of the aggressive andsexual drives in young male chicks is briefly described and the relationship between the two drives was examined in young male chicks treated with testosterone propionate. It is suggested that the relative aggressiveness and sexual activity are also uncorrelated in immature cockerels.

In Buntings, fear responses express five main tendencies: to flee, to hide, to watch the feared object, and to give certain calls.

Alarm, mobbing, freezing and hiding are discussed. Fear responses to predators near the nest, and distraction displays are described.

Resting attitudes occur irrelevantly during fear in the Buntings. They have a submissive function, but are not always caused by fear of another bird. The crest feathers (and more rarely those of the back) are sometimes raised in fear. Possible causes of these types of behaviour are considered.

Young gonadectomized males and females C57BL/10 mice were given one 0.5 mg. injection of testosterone propionate at 40 days of age and tested for their aggressive responses on the succeeding 10 days. The males responded more aggressively towards each other than did the females. The two most likely explanations of these results are that either the nervous systems of both sexes respond differentially to testosterone or that females do not provide as adequate a stimulus for releasing aggressive responses as do the males.

Two hundred and ninety-five nests of a Black-headed gull colony were inspected for eggs once, twice or three times daily from 14th April till 6th May, and at irregular intervals later. In 196 nests first clutches appeared over a period of more than three weeks. In the first week only 13 per cent. of the birds started laying. Darling's (1938) suggestion that discrete parts of a big colony behave as he thought isolated colonies did, could not be verified. Slightly more a-, b- and c-eggs are laid during the day than during the night but the differences are not significant. No significant difference was found for the number of eggs laid in the afternoon and in the morning. Of 184 clutches 70 per cent. consisted of 3 eggs. This figure is almost certainly too small, because it does not include the clutches which had been robbed before they were inspected. The most common interval between the laying of successive eggs of a clutch is 1 1/2–2 days. The mean interval between the laying of the a- and b-eggs is not significantly different from the mean interval between the b- and c-eggs. The Black-headed gull lays its clutch in a shorter time than do Common and Herring gulls.

If the a-egg was removed within 12 hours after it was laid the ♂ laid a d-egg 2 days after the c-egg. If both a- and b-eggs or all 3 eggs were removed immediately after each was laid protracted laying occurred in a number of cases. In one nest 7 eggs were obtained from one ♂. Therefore, the Black-headed gull also is an indeterminate layer as Salomonsen (1939) and Paludan (1951) proved for the Herring gull and the Lesser Black-backed gull. Reducing the number of eggs had no effect on egg-laying if one egg was left in the nest. It is thus not the size of the clutch but the gull's brooding which causes the cessation of egg-laying. Removing both eggs immediately after the b-egg was laid caused protracted laying in a number of cases. If, however, all eggs were removed after the c-egg was found no further egg was laid immediately but a full second clutch appeared after 8–13 days.

By adding eggs several days before the gulls laid it was possible to suppress egg-laying completely or partially: 13 pairs never laid though many brooded our wooden eggs for 2 months. In 4 nests one egg was laid after 5–7 days' sitting, in 13 nests we found 2 eggs and in 4 nests where the birds had only sat for one day all 3 eggs appeared.

Five ovaries were inspected at various times during the egg-laying cycle. Around the time the first egg is laid, the second and third are successively smaller and a tiny fourth follicle was found, apart from the still smaller reserve eggs. In two birds killed after the b-egg had been laid this d-egg was degenerating. It is concluded, as it was for the Herring gull (Paludan, 1951), that incubating has an inhibitory influence on the growth of follicles and causes them to degenerate as long as they have not