“Twin Swapping” a Technique Developed for the Successful Rearing of Giant Panda Twins
The captive population of giant pandas has soared over the last 10 years. In 2002 there were 152 animals in 19 institutions and as of November 2013, there were 375 animals in 72 institutions. The genetic diversity of the captive population is 97.4%. This dramatic change has been due in part to improved husbandry practices and increased cub survival rate. Giant panda cubs are altricial and rely heavily on proper maternal care for survival. Even though the birth of twin cubs is not uncommon, the dam can normally only care for one cub, resulting in the death of the second one unless there is human intervention.
In July 2013 giant panda twins were born at Zoo Atlanta. The zoo’s staff, in cooperation with Chinese colleagues from the Chengdu Research Base of Giant Panda Breeding, Chengdu, China, implemented a “twin swapping” technique to assist the dam in successfully rearing both cubs. This technique allowed for the rotation of cubs between the dam and nursery. The cubs’ birth weights were 99.1 and 145.3 grams, and they were born within two minutes of each other. The giant panda nursery had been set up prior to the expected birth window. Within a few minutes of birth, the second cub born was removed from the birth den and taken into the nursery for examination. Within two hours, the first cub was then also removed from the dam to be examined and the second born was returned to the dam. Initially, this pattern of swapping the cubs was done every 1–1.5 hours. During the first week, the incubator temperature and humidity were 95° F (35° C) and 55–65% respectively. As the cubs grew and their ability to thermoregulate improved, these settings were adjusted and were aimed at maintaining a body surface temperature between 96.8–99.5° F (36–37.5° C).
Over the following weeks the interval between cub swaps was increased and was dictated by the cubs feeding habits and weight gains. Every time a cub was in the nursery, it was stimulated to urinate and defecate, and weights were recorded at the time they were removed from the dam and immediately before being returned to the dam. Formula supplementation was started on day 83, at which time the cubs’ body weights were 3,285 and 3,475 grams. The daily formula supplementation average was 1–2% of their body weight and the decision on when to start formula supplementation was made based on a decreased rate of growth as compared to previous cubs. The formula used consisted of Esbilac®a (12.5 grams), Enfamil® (Gentlease)b (12.5 grams) and water (75 ml).1 Between days 85 and 230 the cubs’ weights were below their siblings at a similar age, but by day 231 the weights were similar to their siblings, all of which had been exclusively mother reared. Even though “twin swapping” is an intense and time-consuming endeavor, it has the great advantage of raising both cubs on maternal milk during the first few months. It also allows for proper social interaction between dam and cub.
The target population for giant pandas in captivity is 500 animals in order to maintain 90% genetic diversity for 200 years. Given the great improvements in the management of this species in captivity, the future of the captive population appears bright.
aPetAg Inc., Hamshire, IL, USA
bMead Johnson and Co, Evansville, IN, USA
The authors would like to thank the entire Zoo Atlanta staff for their support and understanding during the rearing of the giant panda cubs. We are also grateful to the staff at the Chengdu Giant Panda Research Base.
1. Edwards MS, Wei R, Hawes J, Sutherland-Smith M, et al. The neonatal giant panda: hand-rearing and medical management. In: Wildt DE, Zhang A., Zhang H., et al., eds. Giant Pandas Biology, Veterinary Medicine, and Management. Cambridge, UK: Cambridge University Press; 2012:315–333.