Title. What is the geometric probability of mating success in the giant panda, Ailuropoda. melanoleuca? Author. Khrysteen Madera

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1 Title What is the geometric probability of mating success in the giant panda, Ailuropoda melanoleuca? Author Khrysteen Madera 1

2 Abstract The giant panda, Ailuropoda melanoleuca, is an endangered carnivorous mammal and a member of the bear family. In this study, I calculated the random probability of mating success and compared it to the actual mating success for the giant panda. The random probability of mating success was estimated to be 0.4%. The actual probability of mating success in the giant panda increases to 100% for males when they are able to find a female within the first 1-3 days of which she is able to reproduce; the success also increases when he is a taller. Once a male has attracted and courted a willing female, he inseminates her by inserting his penis into the vagina while in the 'doggy style' position. 2

3 Introduction The giant panda, though endangered, is native to some mountainous regions in China. The giant panda is mainly nomadic and are very solitary animals. Giant pandas primarily eat bamboo, despite being considered carnivorous. It is among the first birds to sing at dawn, and its song consists of several discrete units that are repeated. Young pandas are the main targets of predators which are very few and include jackals, leopards, and the yellow-throated marten. They are able to defend themselves from these creatures, but are endangered by the actions of humans: such as poaching and habitat invasion. The giant panda gives birth to live young, they begin to breed in the winter and this extends well into spring. Since giant pandas are an endangered species, much of their breeding occurs in captivity. Captivity has played a role in mating success. Because giant pandas lose interest in mating once captured, a male who is able to remain in their natural habitat is more likely to be successful in producing offspring than a male who is in captivity; artificial insemination may be necessary for breeding in captivity. In this study, using a method of geometric probability, I compared the random mating success with the actual mating success of the giant panda. Method Random mating means: if you closed your eyes and threw 100 darts at the rear of a female giant panda, what would be the chance of hitting the vagina bull s-eye? Random mating success was calculated based on two geometric figures (Fig. 1 and 2). The surface area of the female s rear was represented by a rectangle. The vagina bull s-eye was represented by a smaller rectangle. The bull s-eye is where the male s penis has to deposit sperm to accomplish a 3

4 successful mating. Random mating success was calculated as the surface area of the vagina divided by the total surface area of the female s rear as presented to the male. Figure 1: This image of a giant panda was obtained from Google images. The rectangle represents the surface area of the female giant panda as a male would see her. The smaller rectangle represents her vagina. Results Target surface area (rectangle): 5.6 x 7.4 = cm 2 Total target surface area: cm 2 4

5 Bull s-eye surface area: 0.4 x 0.4 = 0.16 cm 2 Random probability of mating success (bull s-eye / target): 0.16/41.44 = x 100 = 0.4%. According to my geometric calculations, the surface area of the bull s-eye is only 0.4% of the total surface area of the target. Thus, by chance alone, only >1 out of 100 darts would hit the bull s-eye. Discussion In this study, I found that, unless the timing, body size, availability and willingness of a partner is just right, there is about less than 1 chance out of 100 that males could find, mount and successfully inseminate females with their eyes (or noses) closed. How do males and females increase the 0.4% random mating success to a 100% actual mating success? Giant pandas only mate either in the winter or spring and the females gestation period can last anywhere from 95 to 160 days. A female chooses a mate based on his song, his sexual secretion, or the bite marks he has left on trees. The male courts a female by singing, emitting sexual secretions, and by leaving bite marks on trees. Both partake in leaving their scent in order to attract a mate; they do this by emitting hormones or even urinating on trees. When the giant panda finds a mate, the male mounts the female 'doggy style' in order to reach the vagina and deposit his sperm. After mating, the male panda abandons the female. The female is left to be a single mother until the panda is able to fend for themselves since the giant panda is primarily a solitary animal. 5

6 Each pair of pandas can produce up to two cubs. However, it is likely that the mother can only provide for one of the cubs in order for them to live to adulthood. 6

7 References Charlton, B. D., Huang, Y., & Swaisgood, R. R. (2009). Vocal discrimination of potential mates by female giant pandas (Ailuropoda melanoleuca). Biology Letters, 5(5), doi: /rsbl Platz, C. C., Wildt, D. E., Howard, J. G., & Bush, M. (1983). Electroejaculation and semen analysis and freezing in the giant panda (Ailuropoda melanoleuca). Journal of the Society for Reproduction and Fertility, 67(1), doi: /jrf Sarich, V. M. (1973). The giant panda is a bear. Nature, 245, doi: /245218a0 Swaisgood, R. R., Lindburg, D. G., Zhou, X., & Owen, M. A. (2000). The effects of sex, reproductive condition and context on discrimination of conspecific odours by giant pandas. Animal Behaviour, 60(2), doi: /anbe Zhou, Z., & Pan, W. (1997). Analysis of the viability of a giant panda population. Journal of Applied Ecology, 34(2), doi: /