What’s more exciting than a polar bear cub? Two polar bear cubs! The birth of any animal here at the Detroit Zoo is exciting, but polar bears offer special cause for celebration. The Detroit Zoo is proudly home to the Arctic Ring of Life – one of North America’s largest state-of-the-art polar bear habitats. These rambunctious new cubs will grow up exploring the more than 4 acres of outdoor and indoor habitats and are the latest polar bears to call the Detroit Zoo home.

Astra and Laerke were born to mom, Suka, and dad, Nuka, on November 17, 2020. Staff from all over the Zoo watched specially equipped cameras in Suka’s maternity den with bated breath, waiting for the arrival of little Astra and Laerke. Once the cubs made their appearance, it was all hands on deck. Even with expert care, polar bear cubs have a high mortality rate in captivity. With this in mind, the question at the forefront of everyone’s mind was a relatively straightforward one – how do we give these cubs the best shot at long, happy and healthy lives?

Newborn polar bears are blind, thinly haired and weigh only around one pound. Despite being born between November and December, mothers and newborn cubs usually remain in the maternal den until late March or even early April. What happens in those five months is largely unknown. There has been very little long-term monitoring on polar bear cubs due to obstacles such as camera placement and staffing availability, which make observing activity in the maternal den challenging. With the combined efforts of team members with diverse skills and backgrounds, the Detroit Zoological Society has undertaken to monitor and report on the growth and development of Astra and Laerke through their first full year of life. With this project, Detroit Zoological Society staff hope not only to ensure that Astra and Laerke thrive, but also to provide a crucial resource for other zoological institutions around the world endeavoring to rear polar bear cubs.

In order to pursue this goal, the Detroit Zoological Society staff needed to come up with a plan that would grow and change alongside Astra and Laerke. Additionally, we needed to be able to monitor the well-being of the cubs from multiple perspectives, both physical and emotional. Phase One of this project has been championed largely by the Arctic Ring of Life staff, mammal curators, veterinarians and the Center for Zoo and Aquarium Animal Welfare and Ethics (CZAAWE). Just a few days after birth, Laerke appeared to need extra support. After careful consideration, we made the difficult decision to remove Laerke from Suka’s care and continue rearing her in the veterinary hospital. With staff never more than a radio call away, Laerke spent her first few months growing and thriving in a behind-the-scenes nursery before transitioning to her own living space at the Arctic Ring of Life. During this time, we were able to weigh Laerke, measure her, and monitor milestones in her growth. It is important to establish normal developmental ranges so that veterinary staff can assess the health and well-being of the animals under their care. Data gathered by tracking Laerke’s growth spurts and noting her key developmental milestones will go a long way towards understanding the needs of baby polar bears. Meanwhile, using cameras in the behind-the-scenes maternal den, we were able to observe Suka and Astra 24-hours a day, 7 days a week. While the presence of cameras in zoological settings is not unusual, prolonged 24/7 monitoring certainly is! Detroit Zoological Society staff came together to share this monumental task for a full 12 weeks. Animal care staff watched more than 2,000 hours of recorded video (120,960 minutes!) and gathered invaluable data on mother-cub denning behavior.

With hundreds of hours of video data, scientists from CZAAWE offered to help with data analysis, freeing up animal care staff to focus on the growing needs of the cubs. Using this valuable dataset, we have been able to answer questions critical to early polar bear development. How frequently does a baby polar bear nurse? When does a baby polar bear leave the nest for the first time? What does maternal behavior look like for a polar bear? With recent transitions to live observations, we have been able to watch as the cubs become increasingly confident and exploratory. We continue to work together to provide peak care and ensure excellent welfare for Astra and Laerke as they approach their eighth month. We look forward to keeping you updated on their progress!

– Dr. Kylen N. Gartland is manager of applied animal welfare science for the Detroit Zoological Society.