Giant Panda (Ailuropoda melanoleuca) Fact Sheet: Reproduction & Development

Polygynous mating

• One male with two or more females (Reid & Gong 1999); multiple females sequentially ("scramble competition polygyny") (Swaisgood et al. 2016)
• Strong competition for access to females mating season (Schaller et al. 1985)
  • Brief, spring mating season
  • Courting pair often attracts more males, creating a competitive/combative situation
    • Viewing competition may be vital for female's receptivity
• Details of male reproductive strategy (Nie et al. 2012)
  • Intense male competition for females about to be fertile
  • After dominant status is established among males, aggression declines
    • Testosterone levels do not correlate with levels of aggression or with outcomes of competition
    • Large body size was primary reason a male became dominant

Courtship

• Scent marking, visual displays and vocalizations important in advertising to and assessing potential mates (Owen et al. 2013; Wei et al. 2015)
  • Individuals produce bleating sounds
    • Appear to rely more on sound to coordinate mating than other bears (Stirling and Derocher 1990)

Mating season

• Late February to early April

Female behavior

• Social conditions influence how some female pandas communicate reproductive status (Owen et al. 2016)
  • Use odor in presence of other females; use sound and visual displays when few females nearby

Reproductive success

• High reproductive rates in the wild (Pan et al. 2014, Swaisgood et al. 2016)
  • Pandas in managed care judged harshly as showing little interest in mating
• Lifetime reproduction
  • A single female capable of producing c. 5-10 litters in her lifetime (Wildt et al. 2004)
• Factors effecting reproduction
  • Food supply available to mother
  • Presence of young
    • Lactation suppresses estrus

Estrus

• Duration
  • Lasts 1-3 weeks with peak receptivity from 2-7 days
• Occurs March-May
  • Females without young may also go into heat in September - October

Fertilization and implantation

• Delayed development and implantation of embryo
  • Development of the fertilized egg may be suspended
  • Implantation in the uterus can also be delayed

Gestation and birth

• Gestation
  • Duration highly variable
    • Ranges 84-184 days
    • Average 138.6 ± 19.8 (Zhu et al. 2001)
• Timing of birth
  • Usually occurs August-October
• Mother's behavior prior to birth
  • Female may descend to lower elevations in the wild (Zhu et al. 2001)
    • Often followed by reduced levels of activity (Zhu et al. 2001)
• Mother's behavior after birth
  • Begins to fast, as occurs in other bears
    • One mother was observed to neither feed or defecate for 25 days
    • Both managed and wild females exhibit this behavior, which seems unrelated to availability of food
  • She does not leave infant
    • Mother remain with infant continually to keep it warm
• Litter size
  • 1-2 cubs (very rarely 3)
    • Only one cub is raised in wild; reports of twins being reared not well documented
      • It is extremely difficult for a female panda to hold, suckle and carry 2 young and eat extra bamboo
    • Managed care breeding now successfully removes one cub, and switches out the twins to give both a chance for mother's care and milk
• Denning (Zhu et al. 2001) (Zhang et al. 2007b)
  • Not having adequate den sites may limit population growth by pandas
  • Female gives birth in a den (rock cave or hollow tree)
    • Often close to water (Swaisgood et al. 2016)
  • Birthing nest is of simple construction with little bedding
  • Females occupy several dens as the cubs grow
  • Reducing exposure to parasites and predators may explain use of several dens
  • Dens abandoned when cub is around 94 days old and can thermoregulate (Zhu et al. 2001)
    • Mothers abandon dens around 112 days after birth

Interbirth interval

• Do not reproduce annually
  • c. 2.2 years for pandas studied in wild (Pan et al 2001) (Garshelis 2004)

Infant characteristics

• Appearance of newborn
  • Pink and naked with sparse covering of white hair
    • At 8-10 days, skin turns gray in areas where fur will be black (Zhu et al. 2001)
  • Tail at birth disproportionately long (1/5-1/3 body length)
  • Eyes closed, don't open fully until 75 or 76 days (but other reports cite 35-48 days; Zhang et al. 1996)
• Size of newborn
  • Extremely small and the most helpless of all placental mammals (85-140 grams/3-5 oz) (Zhu et al. 2001)
    • Size of all newborn bears is quite small compared to the mother's weight
      • A black bear cub, for example, is only 0.36% of the mother's weight
    • Pandas are the extreme example of this trend
      • A cub, for example, may be only 0.12 % of mother's weight

Birth - Infant (1.5 years) (Schaller et al. 1985)

• Interaction with mother
  • A wild infant spends almost all its time for first weeks directly on mother's body
  • Cubs squall loudly and often in first 2 or 3 months
  • Mother uses mouth rather than a clumsy paw to pick up newborn (Swaisgood et al. 2003)
  • Mother stimulates waste elimination by young cub by licking anogenital area and consumes all waste to eliminate smells and thwart predators
  • Infants suckle often, 6-14 times/day, for up to 30 minutes each time
  • Infants remain with mother up to 18 months
• Developmental milestones
  • Crawling attempts begin at 2 months
  • Eyes fully open between 2 - 3 months
  • Teeth begin to erupt in 3rd month (Edwards et al. 2006)
  • Begin to vocalize less around 3 months; mothers become less responsive (Swaisgood et al 2003b)
  • Begin walking efficiently until 3 - 5 months
  • Begin to sample bamboo around 5 - 6 months (Edwards et al. 2006)
  • Fully weaned at 18-24 months in wild (Edwards et al. 2006b)

Sub adults: 1.5-5 years

• Juveniles travel with mothers until about 18 months (Schaller et al. 1985)
• Thought that higher mortality occurs among subadults and females (Li et al. 2017)

Adults:  (Howard et al. 2006)

• Males are of reproductive age from around 6 to 26 years
• Females can reproduce between 6 and 20 years

Wild populations

• Not reported

Managed care

• No AZA estimates

A giant panda mother protectively cradles her helpless newborn against her body.

Cubs develop quite slowly. Teeth begin erupting during the third month but nursing continues for 8 or 9 months.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Garshelis (2004)
Howard et al. (2006)
Nie et al. (2012)
Owen et al. (2016b)
Pan & Lü (1993)
Reid & Gong (1999)
Schaller et al. (1985)
Snyder et al. (2004)
Swaisgood et al. (2003b)
Zhang et al. (2007b)
Zhu et al. (2001)