Successful captive breeding of a Malayan pangolin population to the third filial generation

Pangolins are the world's only scaly mammals (Order Pholidota, Family Manidae), comprising eight extant species across Asia and Africa. They are the most trafficked group of wild mammals, with an estimated 895,000 individuals involved in international trafficking between 2000 and 2019, leading to dramatic declines in wild populations. Malayan pangolins (Manis javanica), distributed in Southeast Asia and parts of China, have been listed as Critically Endangered (CITES Appendix I) since 2017. Reported gestation lengths range from about 168 to 188 days, but reproductive biology in captivity remains poorly understood. Over the past 150 years, repeated attempts to maintain pangolins in captivity largely failed, with most individuals dying within months due to environmental stressors and diseases (e.g., pneumonia, gastrointestinal disorders), likely linked to a weakened immune system. While isolated captive breeding events have been reported, consistent production beyond the first filial generation (F1) has been rare, with a notable exception in Chinese pangolin (Manis pentadactyla) at Taipei Zoo producing F2. There is limited knowledge on female reproductive biology, including oestrus cycles, gestation period, age at sexual maturity and weaning in captivity. The purpose of this study is to report the first successful captive breeding program for Malayan pangolins achieving a third filial generation (F3) between 2016 and 2020, and to provide data on reproduction, survival, and husbandry that can inform conservation and management.

Prior work documents extensive historical difficulty in maintaining pangolins in captivity, with high mortality attributed to disease and stress. Reported gestation periods vary (approximately 168–188 days) and female reproductive biology is poorly characterized. Captive breeding successes have generally been limited to F1, with rare F2 cases (e.g., Taipei Zoo Chinese pangolin). Previous studies inferred possible early sexual maturity (~6–12 months) based on observations of wild individuals. Captive populations of many mammals often display male-biased sex ratios; female-biased ratios are rare (e.g., pygmy hippopotamus). These gaps and challenges motivated systematic investigation into captive breeding, survival, and reproductive parameters for Malayan pangolins.

Ethics and permits: Approved by the Forestry Department of Guangxi Zhuang Autonomous Region (Permit A2016008) and Biology Ethics Committee of the Guangxi Forestry Research Institute [GXFI (A2016006)]. Animals: 33 confiscated wild-origin Malayan pangolins (Manis javanica) were housed and managed at a rescue and breeding center. Females were coded (WF1, WF2, etc.). To control the study, the center stopped receiving new wild pangolins from 2016 onward. Housing and husbandry: Pangolins were kept in indoor cages composed of an activity area, insulated wooden shelter, and associated spaces. Throughout the study, husbandry protocols were refined; from December 2019, stricter hygiene measures were implemented, including increasing cage cleaning frequency (1–2 times per month), flame disinfection of shelters, immediate cleaning if appetite loss was observed, regular replacement of nest matting, reduced indiscriminate medication, targeted antibiotic use (Amikacin + Kanamycin 0.1 mL/kg each) if no appetite for 3 days, improved food storage with desiccants, and environmental sanitation. Mating design and observations: For assessing female fertility in captivity, 11 wild females and subsequently captive-born females (F1 and F2) were paired with males for cohabitation. Cohabitation events and observed matings were recorded. For male mating willingness, 14 adult wild males (and 5 captive-born males) were tested during cohabitation; willingness was defined by courtship behaviors (following, touching, mounting) leading to mating. Random pairing was used, and some cohabitations occurred during pregnancy. Reproductive metrics: Conceptions were attributed to cohabitation windows; for captive-born females, mating was completed within 5 days of cohabitation. Gestation length per pregnancy was defined as the interval from the first observed mating to parturition and from the last observed mating to parturition (reported as a range). To increase resolution, wild cases with mating spans exceeding 7 days were excluded in a subset analysis to align with captive-born females (≤7-day mating windows). Survival and mortality analyses: Annual survival rates were computed for wild and captive-born pangolins. Mortality was classified by age relative to weaning (pre- vs post-weaning). Weaning in this colony was extended to ~150 days. Autopsies (n=11 adults) were conducted to investigate causes of death; tissues underwent bacterial 16S rDNA amplification and sequencing to identify pathogens. Data and documentation: Reproductive histories, cohabitation records, offspring outcomes, and survival data were compiled (Supplementary Data/Tables). Growth measurements were recorded for selected individuals (e.g., FG6).

• Scale and generations: From 2016–2020, 33 wild pangolins produced 49 captive-born offspring across three filial generations (F1–F3); 20 individuals were alive at study end.
• Female fertility and conception efficiency: • Wild females: 10/11 females had 29 pregnancies yielding 30 offspring (including one twin). Excluding 10 cohabitations during pregnancy, 16/20 counted cohabitations resulted in conception (80%). Of these pregnancies, 13/16 (81%) were conceived during the first cohabitation. • Captive-born females (12 tested: 10 F1, 2 F2): 11/12 (91.7%) produced 18 viable offspring; overall conception rate 18/22 (82%) when excluding cohabitations during pregnancy. Of these pregnancies, 14/18 (78%) were conceived during the first cohabitation; all 18 conceptions occurred within 5 days of cohabitation mating.
• Sexual maturity: Captive-born females reached sexual maturity as early as 7–9 months (n=4 conceived before or around weaning); seven of 11 conceived within a year. One male successfully mated and fertilized a female at 9 months of age (n=1).
• Postpartum conception: Females could conceive shortly after parturition or pup death: examples include conception 8–11 days postpartum (5–8 days after pup death) and 53 days postpartum.
• Mating during pregnancy: Approximately half of pregnant captive-born females mated during pregnancy; observed acceptance of mating 32–53 days before delivery in examples.
• Male mating willingness: Low among males—only 5/14 wild males showed full mating behavior during cohabitation; 4/5 captive-born males showed no intention to mate (i.e., 1/5 willing).
• Sex ratio: Among 38 sexed captive-born offspring, 24 females and 14 males (~2:1; 63% female), indicating a female-biased sex ratio at birth.
• Survival rates: Wild pangolin annual survival improved from 81.8% (2016) to 100% (2020). Captive-born annual survival rates were 85.7% (2016; small n), 60% (2018), and 76.9% (2020); combined survival increased from 80% (2016) to 85.7% (2020). Mortality was higher pre-weaning (65.5% of 29 captive-born deaths occurred before birth or pre-weaning); post-weaning survival was higher.
• Causes of death: Adult necropsies showed lung hepatisation; two had gastric ulcerations. 16S analyses detected bacteria including Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Morganella morganii (formerly Morgenia) in multiple cases, suggesting bacterial infections as a major cause of death.
• Gestation length: Overall (wild + captive-born) gestation 154–203 days (n=39) with a peak at ~185 days. Restricting to ≤7-day mating windows yielded 182–195 days in wild (n=10) and 177–192 days in captive-born (n=17); combined 177–195 days (n=27) with a peak at ~185 days.

This study demonstrates that Malayan pangolins can be successfully maintained and bred in captivity to a self-sustaining level, achieving three filial generations and high conception rates under managed cohabitation. Early sexual maturity (as early as 7 months), frequent conception during the first cohabitation, rapid postpartum return to fertility, and mating during pregnancy suggest an efficient reproductive strategy. The high rate of conception shortly after mating supports the hypothesis of copulation-induced ovulation, akin to induced ovulators such as rabbits, which could contribute to reproductive efficiency in this species. Implementing enhanced hygiene and husbandry measures coincided with marked improvements in adult survival, especially among wild-origin animals, implicating infectious disease control as central to captive success given pangolins’ potentially weakened immune defenses. The observed female-biased sex ratio at birth contrasts with common male-biased ratios in captive mammals and, if confirmed in larger samples, could facilitate faster population growth in captivity. Conversely, low male mating willingness represents a constraint on natural mating success, paralleling challenges seen in other captive species (e.g., giant panda) and indicating a need to address environmental or genetic factors influencing male behavior. Higher pre-weaning mortality highlights the importance of optimizing neonatal care, maternal support, nutrition, and nursery conditions. Overall, the findings address key knowledge gaps in pangolin reproductive biology (gestation length, maturity, mating dynamics) and provide a foundation for conservation breeding and potential reintroduction strategies.

The study establishes the first self-sustaining captive population of Critically Endangered Malayan pangolins and documents breeding to the third filial generation. It quantifies efficient reproductive parameters (early sexual maturity, high first-cohabitation conception rates, rapid postpartum fertility) and a gestation peak around 185 days, alongside improved survival with enhanced husbandry. These advances offer practical guidance for pangolin conservation breeding and management and contribute critical biological insights. Future work should: (1) assess genetic diversity and structure of the captive population relative to wild counterparts; (2) mitigate inbreeding and investigate determinants of low male mating willingness; (3) refine neonatal and maternal care to reduce pre-weaning mortality; and (4) develop and evaluate staged reintroduction protocols following IUCN guidelines, incorporating disease screening and genetic assessments.

• Sample size constraints for some analyses (e.g., sex ratio based on 38 sexed offspring) limit generalizability; the observed female bias requires confirmation in larger cohorts.
• Initial uncertainty in cohabitation duration led to broad gestation ranges in early wild cases; restricting to ≤7-day mating windows improved resolution but reduced sample size.
• Causes of death were inferred from a limited number of adult necropsies (n=11) and may not represent all mortality drivers, particularly in neonates.
• High pre-weaning mortality indicates unoptimized neonatal and maternal care; specific environmental, nutritional, or genetic contributors were not dissected experimentally.
• Low male mating willingness was observed but not mechanistically investigated; roles of environment, management, and genetics remain to be clarified.
• Housing and husbandry details were evolving; some methods (diet specifics, exact environmental parameters) are not fully detailed in the excerpt and may influence outcomes.