Behavior of the Giant Panda (Ailuropoda melanoleuca): Reproduction and Captivity. Tanya Hunter

Transcription

1 Behavior of the Giant Panda (Ailuropoda melanoleuca): Reproduction and Captivity Tanya Hunter April 5, 2006

2 The giant panda (Ailuropoda melanoleuca) is indigenous to the forests of China. Their populations have been in decline for many years, and they are now considered an endangered species. Many panda reserves and breeding centers, all located in China, have been created to protect what is left of their population and to help increase their numbers (WWF, 2006). Reproduction in the panda is complex, and not much is known about it. This is believed to be one of the many contributions to the decline in panda populations, as well as to problems in breeding in captivity. Understanding panda physiology and behavior is crucial for ensuring reproductive success. The ability to identify a female panda in estrus can increase the probability of a successful mating. This is helpful for male pandas as well as breeders. Maintaining a pregnancy is required to ensure the birth of healthy offspring. Once an infant is born, the mother must adequately care for the young. If she is not able to, then sufficient human intervention is required. However, pandas have trouble adapting to the presence of humans and captive living conditions. Pandas in captivity are often physically inactive and stressed, so successful mating is relatively low (Liu, et al., 2003; Swaisgood, et al., 2003). Continuing research is needed to improve enclosure conditions and improve the survival of the giant panda. The diet of the giant panda consists primarily of many different species of bamboo, although they also eat other plants and sometimes animals, such as fish. Since their digestive system resembles that of a carnivore, they are unable to digest the plants very efficiently, and as a result must eat large amounts of it and spend most of the day eating (WWF, 2006). Pandas live in solidarity, except during mating season. They are seasonally monoestrous, with the mating season taking place between March and May. During this time, the female may only be fertile for a few days with spontaneous ovulation (Durrant, et al., 2003). Male pandas will compete for

3 access to multiple females, a form of mating known as polygamy. After mating, the male will leave the female and she will raise the offspring alone (Durrant, et al., 2003). Birthing takes place in the early fall of the next year, from August to November. Usually a female will give birth to one or two cubs, however, if she does give birth to two she will usually abandon one and raise the other (WWF, 2006). Newborn cubs are very small and weak. They weigh around 200g and have very little fur. Infants feed on their mother s milk (Durrant, et al.; Milius, 2001). A panda cub will grow at a relatively fast rate, especially during it s first year, until it reaches sexual maturity at about 4-5 years old. The cub will leave its mother when it is about two years old (WWF, 2006). Understanding estrus behaviors and their relationship with estrogen levels is important to the success of breeders and artificial insemination techniques. During breeding season, females experience a peak in estrogen levels, after which ovulation occurs. High estrogen levels also appear to trigger mating behavior, such as scent markings, rear presentations and tail-up display towards males, and vocalizations such as bleating and chirping. These behaviors can occur at all times during the year, but during estrus the frequency increases, perhaps to help provide an indication of fertility. While the increase in these behaviors is triggered by estrogen, they do not appear to be completely maintained by it, so these behaviors continue for a few days afterwards as well (Lindburg, et al., 2001). Knowing when a female is pregnant is essential for developing effective breeding programs. It can help breeders figure out the most efficient methods of impregnating a female, as well as what factors are needed for its success. However, it can be difficult to determine if and when pregnancy occurs in a female panda. After fertilization an egg will remain in the female reproductive tract for a period of time without implantation. During this time it is speculated that

4 the development of the embryo is suspended. This is referred to as delayed implantation (Sutherland-Smith, et al., 2004). Pandas can also experience pseudopregnancy, in which they express behavioral and hormonal changes similar to an actual pregnancy (Sutherland-Smith, et al., 2004). As a result of this, the precise length of the gestation period is not exactly known. It is estimated to be an average of 146 days, but the range can be vast (Sutherland-Smith, et al., 2004; WWF, 2006). In captivity the estimated range of gestation is between 84 to 160 days (WWF, 2006). It is believed that, considering their short gestation period, most of the mother s energy and resources are spent in the time following birth. This is shown through a relatively insignificant change in weight during pregnancy, as well as through her rather extreme behavior after giving birth. Also, if a mother gives birth to twins, she will abandon one, allowing her to concentrate on raising the other. Newborn cubs are weak and fragile, and depend largely on their mother for survival. The mother may fast at first, eating and drinking very little as she cares for her cub. The infant feeds off of its mother s milk for about a year and a half, further adding to the stress and demands of the mother (Milius, 2001). Its mother s milk provides essential nutrients and proteins, and its composition is unlike other animal (Xuanzchen, et al., 2005). This information is important for panda cubs raised by humans in captivity, as pandas experience a substantial amount of growth in the first few years of life (WWF, 2006). As with other mammals, such as rats, newborns has very little fur and will usually have problems with thermoregulation, showing behavior similar to ectotherms (Alberts, 1978). Therefore the mother is also responsible for maintaining the body temperature of her young by holding and covering it to prevent exposure to the external environment.

5 However, regardless of this attention and care, pandas in captivity experience high rates of neonatal mortality, with only about 50% of the offspring living for more than a month (Zhang, et al. 2000). One issue is that some pandas in captivity will simply refuse to provide any maternal care for her offspring, leaving human intervention as the only option. This can be problematic on a number of levels. Firstly, maternal behavior is primarily the response of hormones released during parturition, but it is maintained through contact and exposure to the infant. If the cub is separated from its mother, then any attempt to reintroduce them at a later time will prove difficult, as the mother may then be even more unwilling to accept the child. Secondly, mother-reared cubs are more likely to exhibit adequate social behaviors as an adult. This increases their likelihood of contributing more to future breeding programs, and of surviving if released into the wild (Zhang, et al. 2000). One instance of a cub being successfully reintroduced with its mother after initially being rejected was extensively studied (Zhang, et al. 2000). While it is not entirely known which component of infant exposure is most significant, it has been discovered that a combination of different stimuli can illicit maternal behavior. Such stimuli includes exposure to infant vocalizations and urine, at first through a surrogate, toy cub. This eventually lead to holding and nursing of the cub itself as it was gradually integrated into the mother s environment. Eventually, the mother began to display normal maternal behavior towards to the infant. Due to ethical issues, subsequent studies of this matter will be limited, but this example provides promise and encouragement that such an issue can be resolved in captivity, hopefully leading to an increase in offspring survival. This can also be helpful in situations that require human intervention, such as a twin being abandoned by its mother. However, as pandas do not adapt to the presence of humans very well, most breeding centers and habitat enclosures strive to keep human interaction

6 with pandas to a minimum. It is only done under extreme circumstances, and maintaining maternal care is given the upmost importance (Zhang, et al. 2000). There are numerous reasons as to why breeding pandas is difficult, particularly in captivity. For example, while the ova in the panda appear to be normal, the follicles undergo unusually high amounts of atresia and cysts during development (Liao, et al., 2001). Another concern is that the pituitary cells can be underdeveloped, resulting in an insufficient amount of gonadotropins needed for normal reproduction (Liao, et al., 2001). Other problems and concerns for captive pandas involve their behavior. Pandas have trouble adjusting to captivity. This is because the environment in the wild is constantly changing, which provides challenges for the panda as it forages for food and explores the terrain. In captivity, the enclosures are small and contain little variation, usually consisting of a highly predictable routine. For example, pandas in captivity do not engage in normal eating behaviors because feedings are controlled by human caregivers. Food is provided at the same time every day and the panda does not have to work to acquire it (Swaisgood, et al., 2003). Furthermore, the animals have little or no control over what occurs around them. Although pandas are solitary, access to other pandas is important. For example, cubs should remain with their mother until they are ready to leave, and if the mother cannot raise the cub, then interaction with other cubs is important. Pandas also require the option of being able to remove themselves from other pandas, which in small enclosures is not always sufficiently possible (Swaisgood, et al., 2003). As a result of these factors, as well as many others, captive pandas tend to be highly inactive and may engage in stereotypical behaviors, such as pacing. Such behavior reflects an inadequate environment and is often accompanied by stress and poor physiological well-being (Swaisgood, et al., 2003). This can have an immense impact on reproductive success for pandas in captivity. For example, many males pandas are

7 uninterested in mating and are often aggressive towards other pandas. Females display weak estrus behavior and have trouble conceiving (Zhang, et al., 2004). To help improve the reproductive success of pandas in captivity, measurements need to be taken to change their environment. One crucial aspect is that the animals must be provided with choices and variation in regards to food and activities. They must also be given more control of their surroundings (Swaisgood, et al., 2003). This can be done on a number of ways. They include: providing larger enclosures with areas of different trees, shrubs and terrain; changing feeding times and locations; allowing pandas to hear, smell and see neighboring animals while keeping them in separate inclosures; and providing objects and devices that require the pandas to work for their food. These methods have proven to decease stereotypic behaviors and stress, and increase overall activity (Lui, et al., 2003; Swaisgood, et al., 2003). In an endeavor to protect and maintain the remaining giant panda (Ailuropoda melanoleuca) populations, knowledge of reproduction and behavior can provide many answers and solutions. The ability to identify a female panda that is pregnant or in estrus can indicate which breeding programs are effective. Understanding maternal behavior and being able to accurately mimic it can help infants survive and remain healthy. As we increase our understanding of reproductive physiology and behavior, as well as the effect of humans and enclosures, improvements can be made to maintain the well-being of pandas in captivity.

8 Literature Cited Alberts, J. R Huddling by rat pups: group behavioral mechanisms of temperature regulation and energy conservation. Journal of Comparative and Physiological Psychology. 92 (2): Durrant, B. S., Olsen, M., Amodeo, D., Anderson, A., Russ, K. D., Campos-Morales, R., Gual- Sill, F., and Garza, J. R Vaginal cytology and vulvar swelling as indicators of impending estrus and ovulation in the giant panda (Ailuropoda melanoleuca). Zoo Biology Liao, M. J., Zhu, M. Y., Zhang, Z. H., Zhang, A. J., Li, G. H., Sheng, F. J Cloning and sequence analysis of FSH and LH in the giant panda (Ailuropoda melanoleuca). Animal Reproduction Science Lindburg, D. G., Czekala, N. M., and Swaisgood, R. R Hormonal and behavioral relationships during estrus in the giant panda. Zoo Biology Liu, D., Wang, Z., Tian, H., Yu, C., Zhang, G., Wei, R., and Zhang, H Behavior of giant pandas (Ailuropoda melanoleuca) in captive conditions: gender differences and enclosure effects. Zoo Biology Milius, S. The Lives of Pandas Science News. 159 (4). 61. < Sutherland-Smith, M.., Morris, P. J., and Silverman, S Pregnancy detection and fetal monitoring via ultrasound in a giant panda (Ailuropoda melanoleuca). Zoo Biology

9 Swaisgood, R. R., Ellis, S., Forthman, D. L., and Shepherdson, D. J Commentary: improving well-being for captive giant pandas: Theoretical and practical issues. Zoo Biology World Wide Fund for Nature. Panda Central: Panda Q & A. WWF China. March 22, < Xuanzhen, L., Mingxi, L., Jianqui, Y., Zhihe, Z., Xiangming, H., Jingchao, L., and Zhi, Y Composition of captive giant panda milk. Zoo Biology Zhang, G. Q., Swaisgood, R. R., Wei, R. P., Zhang, H. M., Han, H. Y., Li, D. S., Wu, L. F., White, A. M., and Lindburg, D.G A method for encouraging maternal care in the giant panda. Zoo Biology Zhang, G., Swaisgood, R. R., and Zhang, H Evaluation of behavioral factors influencing reproductive success and failure in captive giant pandas. Zoo Biology