Captive breeding in giant pandas – Bridging between innovative ART and reproductive biology

We aim to elucidate the secrets of giant panda reproductive biology - particularly the regulation of diapause - employing assisted reproduction techniques (ART) and subsequent in vitro modelling. The acquired knowledge will help to develop embryo transfer protocols in pseudo pregnant females.

The success of the conservation breeding program for giant pandas (Ailuropoda melanoleuca) has increased significantly in recent decades thanks to artificial insemination, hormonal monitoring, and improved reproductive management. In 2025, approximately 800 giant pandas were living in human care worldwide. Nevertheless, not all animals reproduce successfully, meaning that genetically valuable individuals may remain underrepresented in the population. At the same time, key aspects of reproductive biology, particularly diapause and pseudopregnancy, are still poorly understood.

Pandas undergo a temporary interruption of embryonic development, also known as embryonic diapause. In pandas, this is temporally flexible and dependent on environmental factors; in contrast, the diapause of the native roe deer (Capreolus capreolus) is temporally determined. In vitro investigation of diapause can elucidate fundamental mechanisms responsible for the inhibition and reactivation of embryonic development.

The research is conducted in close collaboration with the Department of Reproductive Biology at Ghent University and the Chengdu Research Base of Giant Panda Breeding, and is based on the management of the panda breeding program at Berlin Zoo and other zoos. High-resolution ultrasound procedures, modern endocrinological methods, and newly developed assisted reproductive technologies (ART) are combined to better understand the estrous cycle, diapause, embryonic development, and pregnancy.

Goals of Assisted Reproduction and Endocrinological Monitoring

• Expanding knowledge of panda reproductive biology through improved endocrinology and diagnostics,
• Linking endocrine profiles with embryonic development stages determined by ultrasound,
• Developing diagnostic tools for on-site birth monitoring,
• Supporting the panda breeding program through hormonal monitoring, AI and ultrasound training, and pregnancy diagnostics
• Development of strategies for the diagnosis and treatment of fertility disorders

Goals of diapause research

• Development of innovative assisted reproductive technologies (ART) for minimally invasive egg retrieval
• Establishment of methods for the in vitro generation of embryos from these eggs,
• Induction of diapause in vitro and identification of the factors involved (maternal and fetal)
• Establishment of embryo transfer techniques
• Investigation of whether corpus luteum dormancy and pseudopregnancy can be utilized for the management of genetic diversity,
• Establishment of the roe deer as a model species for diapause research in collaboration with international partners and at the Leibniz-IZW field station

Achieved project goals and outlook

Seven pandas were born following successful artificial inseminations with direct involvement of the IZW team: These include the two births of panda twins at Berlin Zoo in 2019 and in 2024, as well as a male cub at Taman Safari in Indonesia in 2025. The cycles and pregnancies were predicted 24 days before birth through hormonal monitoring (PGFM) and monitored via ultrasound one week before birth.

Based on the oocytes obtained via minimally invasive procedures in Chengdu in January 2019, an in vitro model for panda diapause was developed for the first time. In the future, embryos and embryonic stem cells are to be generated from these oocytes. In the long term, the project aims to enable the transfer of embryos to pseudopregnant females at a suitable stage of the cycle. This would allow even genetically less valuable or overrepresented females to be used in the future to carry genetically valuable offspring.

Prof. Hildebrandt is a member of the Academic Committee of the Chengdu Research Base of Giant Panda Breeding and was named “Giant Panda Personality of the Year” in 2019.

Ulbrich SE, Elsafadi S; Giacometti R; Bernal-Ulloa S; Holtze S; Ortmann S; Bosi D; Saenz de-Juano MD; Leonard AS; Pausch H; Göritz F; Hildebrandt TB (2025): First Successful Cervical Artificial Insemination in the European Roe Deer (Capreolus Capreolus). THERWI-D-25-00010First  

Elsafadi S, Bernal-Ulloa SM, Giacometti R, Göritz F, Hildebrandt TB, Ulbrich SE (A case report: Documenting intrauterine single twin death in the European roe deer (Capreolus capreolus). Theriogenology Wild Elsevier BV published: 2025 https://doi: 10.1016/j.therwi.2025.100130

Wauters J, Wilson KS, Cools T, Vancsok C, Bouts T, Mulot B, Leclerc A, Haapakoski M, Kok J, Kühne R, Ochs A, Duncan WC, Girling SJ, Hildebrandt TB, Zhou Q, Li R, Zhou Y, Cai1 K, Liu Y, Hou R, Rae M, Valentine I, Vanhaecke L, Li D (2023): Pregnancy length and health in giant pandas: What can metabolic and urinary endocrine markers unveil? Theriogenology Wild 3 (2023) 100063, https://doi.org/10.1016/j.therwi.2023.100063.

van der Weijden VA, Bick JT, Bauersachs S, Rüegg AB, Hildebrandt TB, Goeritz F, Jewgenow K, Giesbertz P, Daniel H, Derisoud E, Chavatte-Palmer P, Bruckmaier RM, Drews B, Ulbrich SE. (2021). Amino acids activate mTORC1 to release roe deer embryos from decelerated proliferation during diapause. Proc Natl Acad Sci USA 118:e2100500118. doi: 10.1073/pnas.2100500118.

Wauters J, Jewgenow K, Göritz F, Hildebrandt TB (2020): Could embryonic diapause facilitate conservation of endangered species? Bioscientifica Prodeedings 3rd International Symposium on Embryonic Diapause

Wilson KS, Wauters J, Valentine I, McNeilly A, Girling S, Li R, Li D, Zhang H, Rae MR, Howie F, Andrew R, Duncan WC (2019). Urinary estrogens as a non-invasive biomarker of viable pregnancy in the giant panda (Ailuropoda melanoleuca). Scientific Reports. 9: 12772. https://doi.org/10.1038/s41598-019-49288-6.

Loi P, Galli C, Lazzari G, Matsukawa K, Fulka J, Goeritz F, Hildebrandt TB (2018). Development to term of sheep embryos reconstructed after inner cell mass/trophoblast exchange. Journal of Reproduction and Development, 64(2), 187-191.

Hildebrandt TB, Brown JL, Göritz F, Ochs A, Morris P, Sutherland-Smith M (2006). Ultrasonography to assess and enhance health and reproduction in the giant panda. In: Giant Panda Biology, Veterinary Medicine and Management, eds. Wildt DE, Zhang A, Zhang H, Janssen DL, Ellis S. Cambridge University Press, 410-439.

Hermes R, Hildebrandt TB, Göritz F, Jewgenow K, Lengwinat T, Hofmann RR (2000). Ultrasonography of the ovaries and uterus and grey scale analysis of the endometrium during embryonic diapause in European roe deer (Capreolus capreolus). Acta Theriologica 45: 559-572.