|
| Giant pandas are as adept as bears at tree climbing. Females often see tree climbing as the only way to escape over-ardent suitors |
Appendix: What is the difference between "r-selected" and "k-selected" species?
Period of Oestrus
Giant panda liaisons are the ultimate in short-lived passions. Females come into heat only once a year for about twelve to twenty-five days, with a critical peak of about two to seven days. It is in this short peak of oestrus that a pair must mate if it is to do it at all. The oestrus period starts around mid-March, when the snows still whiten the ridges and ravines of panda country, and continues to about mid-May, with a peak in April and early May. In the Qinling, Liang and Min Mountains, there may also be a second oestrus period between September and November. Captive animals may also show weak signs of oestrus in autumn. Females that fail to conceive in spring may show signs of a weak heat in September or October, but coupling occurs in spring.
|
| During the courtship phase of mating the partners sometimes indulge in play |
Male and female giant pandas undergo noticeable behavioural changes during this period of peak heat. From being shy animals that shun direct contact they become sociable creatures earnestly seeking out other members of their species. They also become noisy. Females about to come into oestrus often take up a position on an exposed ridge, from which sound carries into surrounding valleys. These sounds attract other males and so increase male competition for the female. A female consequently improves her chances of mating with the healthiest and strongest male, the best available father for her cub. Now the green bamboo world is full of barks, roars, bleats and chirps of courting excitement. The researchers heard wild pandas on thirty-two occasions and 87.5 per cent of these fell between March and May. Almost half of these were emitted during meetings of two animals and are likely to have been the sounds of courtship.
There are also definite physiological changes. The testes of males enlarge and the level of androgens in their urine rises in the presence of females. Males also become much more active and scent mark more frequently and vigorously, seeking out the females whose home ranges overlap with theirs. One to two weeks before peak receptivity, females lose their appetite and become more restless, bleating often and chirping once in a while as their thoughts turn to mating. A female will scent-mark more frequently and begins to produce sounds that are not heard at other times of the year. Most noticeable and unbearlike of these is the bleat, very similar to the sound of a domestic goat. as her vulva swells and reddens, she will rub it against objects or with her paw. Urine levels of oestrone, a by-product of oestrogen, increase as these changes occur and reach a maximum during the two- to three-day period of peak receptivity. The behaviour of the female during this pre-oestrus period may be in important in stimulating hormonal changes in the male, bringing him into reproductive condition. When a captive male is introduces to an oestrous female, the level of male hormones in his urine rises, reaching a sudden peak when the female is at her most receptive and decreasing just as rapidly after mating is over.
Males and females do not come face to face as soon as the females become receptive. They first of all have to sound out each other's suitability which they do by calling and by reading each other's scent messages. Once the male discovers that the female is about to reach her peak of receptivity, he will spend several days ‘keeping company’ with her, following around her home range, renewing old acquaintances or, if the resident individual has been replaced by someone new, forging a new relationship. This pre-courtship period allows the partners to build a sound relationship and to coordinate their activities and test each other for compatibility. Without it, mating would not occur.