[ECO]Understanding, Monitoring, and Protecting Polar Bear Families

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Understanding, monitoring, and protecting polar bear families

After the 24-hour darkness of the polar night, the return of the sun to Svalbard also signals the beginning of the field season for Polar Bears International’s

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. I arrived in Svalbard only a few days ago to support this long-running project, and the change in daylight in this short time has been staggering. As our days increasingly shift from darkness to light, it’s easy to imagine the polar bear cubs about to experience a similar change. Around this time of year, polar bear mothers and their new cubs will emerge from the dark, snow-covered dens and experience the world outside for the very first time.

Maternal dens are essential to keeping these fragile newborns – born in mid-winter and weighing little over 600g  – warm and safe, tucked away under drifting snow.The interior of a den can be more than 20 degrees Celsius warmer than the external environment. However, it’s a challenging time for their mother. 

While her cubs feed on the fattiest milk found in any mammal on land – equivalent to whipping cream – a mother bear doesn’t eat for the entire time she is in the den. Despite this impressive fast, the female polar bear will typically defer moving her cubs straight to the sea ice once they emerge from the den in the spring. Instead, she’ll remain at the den site for several weeks after her first foray outside, allowing her cubs to gradually acclimatize to life outside the den and grow stronger, before the family makes their final departure towards the sea ice.

Given hungry mothers are strongly motivated to return to hunting seals from the ice, this ******* must play an important role in the development of cubs. Yet due to the difficulties in accessing and monitoring secluded polar bear dens across the vast Arctic, this post-den emergence ******* is a phase that we still know relatively little about. 

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Polar Bear mom and cubs. Image: Simon Gee, Polar Bears International

Since 2016 in Svalbard, and even earlier in Alaska, Polar Bears International has been testing ways to better understand, monitor, and protect polar bear families as they emerge from their dens during this critical time. Detecting where a den has been dug into the snow is the first challenge. Often, researchers rely on GPS data from satellite collars worn by female polar bears for 1-2 years to identify exactly where a bear is denning.

Although that data can give a good estimate of when a bear enters and finally abandons a den, they tell us little about how mothers and cubs behave during the post-emergence *******. To better understand this phase, we have been deploying remote camera systems across the last decade at sites where females are suspected to be denning (identified from their satellite collars), with the aim of capturing footage of polar families as they emerge from their den. 

After approaching a den on ski or by foot to minimize disturbance of the denning bears, we leave the cameras in place to record for several weeks until the family has departed the area, and the equipment can be retrieved – keeping our work as non-invasive as possible.

The study is by its nature collaborative: Arctic fieldwork requires high-level safety and logistics, facilitated by our partners at the Norwegian Polar Institute while designing high-quality camera systems that are light enough to transport but can withstand the frigid Svalbard spring (and the attentions of curious polar bears) is made possible by collaborators at San Diego Zoo and Wildlife Alliance’s conservation technology lab.

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Researchers setting up a remote camera in Svalbard’s mountains in 2022. Image: Kt Miller / Polar Bears International

In new research published on

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, we highlight some of the insights into polar bear behaviour that we have gained from this study. Although the polar bears in our study first exited their dens on average on March 9^th and remained at the den for a further 12 days, the diversity of strategies we recorded was particularly surprising. One family abandoned the den just two days after emerging, whereas another family remained in place for a full month.

Two mothers decided to move their families to new dens that they excavated close to the original. In general, cubs rarely left the den without their mother and remained close to her while outside. We were also more likely to see cubs emerge from the den when temperatures were warmer, underscoring that this post-emergence ******* serves to allow cubs to acclimatize and to further mature. We also noted that bears tended to depart the den site earlier than has previously been recorded in Svalbard, which requires further monitoring to see if this is an emerging trend. 

Beyond insights into behaviour and den emergence timelines, we also combined photos from the remote cameras with data from the satellite collars that were worn by the denning mothers. By linking the data from the collar with behaviours observed on the cameras, we could identify signals in the collar data that indicated when various denning-related activities had taken place. 

Since time spent in the den and around the den site after emergence can have positive impacts on subsequent cub survival, accurately monitoring denning behaviours could be an increasingly important tool in population monitoring. This issue is becoming all the more pressing as a warmer, more icy Arctic means greater human expansion and industrialization in the region and bringing humans and denning habitats into greater overlap and risking disturbance of polar bear families during this vulnerable time. 

Here in Svalbard, we are ramping up for this year’s deployment. Building on our earlier work, we hope to build out a longer time series to better understand how denning polar bears are faring in this region, which has been experiencing some of the fastest rates of warming on the planet. By enhancing our ability to protect mothers and cubs during the critical denning *******, we give the next generation the best chance to thrive in a rapidly changing world.

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