Behavior of the Giant Panda ( Ailuropoda melanoleuca )

							Behavior of the Giant Panda (Ailuropoda melanoleuca):

             Reproduction and Captivity




                                                    Tanya Hunter

                                                        April 5, 2006
       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
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
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.
       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
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
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.
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