Polar bear attacks on humans: Implications of a changing climate

The important thing to remember is: People will die!~ctm

First published: 2 July 2017 Full publication history

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ABSTRACT

Understanding causes of polar bear (Ursus maritimus) attacks on humans is critical to ensuring both human safety and polar bear conservation. Although considerable attention has been focused on understanding black (U. americanus) and grizzly (U. arctos) bear conflicts with humans, there have been few attempts to systematically collect, analyze, and interpret available information on human-polar bear conflicts across their range. To help fill this knowledge gap, a database was developed (Polar Bear-Human Information Management System [PBHIMS]) to facilitate the range-wide collection and analysis of human-polar bear conflict data. We populated the PBHIMS with data collected throughout the polar bear range, analyzed polar bear attacks on people, and found that reported attacks have been extremely rare. From 1870–2014, we documented 73 attacks by wild polar bears, distributed among the 5 polar bear Range States (Canada, Greenland, Norway, Russia, and United States), which resulted in 20 human fatalities and 63 human injuries. We found that nutritionally stressed adult male polar bears were the most likely to pose threats to human safety. Attacks by adult females were rare, and most were attributed to defense of cubs. We judged that bears acted as a predator in most attacks, and that nearly all attacks involved ≤2 people. Increased concern for both human and bear safety is warranted in light of predictions of increased numbers of nutritionally stressed bears spending longer amounts of time on land near people because of the loss of their sea ice habitat. Improved conflict investigation is needed to collect accurate and relevant data and communicate accurate bear safety messages and mitigation strategies to the public. With better information, people can take proactive measures in polar bear habitat to ensure their safety and prevent conflicts with polar bears. This work represents an important first step towards improving our understanding of factors influencing human-polar bear conflicts. Continued collection and analysis of range-wide data on interactions and conflicts will help increase human safety and ensure the conservation of polar bears for future generations. © 2017 The Wildlife Society.

Polar bears (Ursus maritimus) have evolved to exploit the biologically productive Arctic sea ice niche by using it as a platform to prey upon marine mammals (Amstrup 2003). Before European exploration, this habitat specialization likely kept them separated from most people, and thus helped reduce human-bear conflicts. However, the extent of human-polar bear interactions began to change in the sixteenth century with the advent of widespread maritime exploration. Historical records provide some insight into the nexus between human and bear behavior and help inform current efforts to reduce human-polar bear conflict.

Although the Arctic has been inhabited by Indigenous people in relatively low numbers for thousands of years, the first recorded polar bear attack we found dates to 1595 when 2 members of William Barent’s second expedition were reportedly killed and eaten by a polar bear in the Russian Arctic (de Veer 1876). The incident occurred on 6 September on an islet near Vaygach Island. Two men were lying in a wind-free depression resting, when:

“a great leane white beare came sodainly stealing out, and caught one of them fast by the necke, the beare at the first faling vpon the man, bit his head in sunder.” The ship’s crew rallied, and tried to drive the bear off of the victim: “hauing charged their peeces and bent their pikes, set vpon her, that still was deuouring the man, but perceiuiug them to come towards her, fiercely and cruelly ran at them, and gat another of them out from the companie, which she tare in peeces, wherewith all the rest ran away (de Veer 1876:63).”

Eventually the crew was able to again rally, and finally killed the bear as it continued to devour its victims. The vivid account provided by de Veer demonstrates the potential danger of polar bears, and is consistent in many respects with what we have learned from more recent attacks.

Continued European expansion into the Arctic led to increased conflict with, and exploitation of, polar bears (Conway et al. 1904). For example, a commercial expedition to Svalbard in 1610 reported killing 27 polar bears and catching 5 cubs (Lønø 1970). Commercial polar bear hunting continued through the centuries. In the early decades of the twentieth century, hundreds of bears were harvested on Svalbard annually. In 1924 alone, at least 901 polar bears were harvested on Svalbard (Lønø 1970). The widespread use of fossil fuels further accelerated human access to remote areas of the Arctic, resulting in significant hunting pressure on polar bears throughout their range after World War II. As a result, by the 1960s, the most significant threat facing polar bears was over-hunting, and populations in some areas were considered to be substantially reduced (Larsen 1975).

To address these and other conservation concerns, in 1973 the 5 polar bear countries (Canada, Denmark [on behalf of Greenland], Norway, the former Soviet Union, and the United States) signed the Agreement on the Conservation of Polar Bears (1973 Agreement). The 1973 Agreement requires the 5 signatory countries (the Range States) to restrict the taking of polar bears and manage polar bear subpopulations in accordance with sound conservation practices based on the best available scientific data (DeMaster and Stirling 1981, Prestrud and Sterling 1994, Larsen and Stirling 2009). It also allows harvest by local people using traditional methods in the exercise of their traditional rights and in accordance with the laws of that Party (1973 Agreement). Subsequent to 1973, measures implemented by the Range States, such as increased research and monitoring, cooperative harvest management programs, and establishment of protected areas, were presumed to have either stabilized, or led to the recovery of, subpopulations that had experienced excessive unregulated harvest (Amstrup et al. 1986, Prestrud and Sterling 1994). Today, polar bears are legally harvested by Indigenous peoples in Alaska, Canada, and Greenland, and harvest levels in most subpopulations are well managed and occur at a rate that does not have a negative effect on population viability (Obbard et al. 2010, Regehr et al. 2015).

However, polar bears now face a new and unprecedented threat due to the effects of climate change on their sea ice habitat (Stirling and Derocher 1993, 2012; Derocher et al. 2004; U.S. Fish and Wildlife Service 2008; Atwood et al. 2016a). Although the current status of polar bear subpopulations is variable, all polar bears depend on sea ice for fundamental aspects of their life history (Amstrup et al. 2008), including access to their primary prey, ice seals (Stirling 1974). Arctic sea ice extent and thickness have declined over the last 4 decades (Stroeve et al. 2014, Stern and Laidre 2016), leading some to conclude that the Arctic Ocean in summer may be largely ice free (i.e., <1,000,000 km²) as early as 2020 (Overland and Wang 2013).

In some parts of the polar bear range, diminishing summer sea ice has resulted in the increased use of terrestrial habitat by polar bears (Stirling et al. 1999, Schliebe et al. 2008, Gleason and Rode 2009, Cherry et al. 2013, Rode et al. 2015b). Longer ice-free periods (Stern and Laidre 2016) shorten polar bear hunting opportunities during the critical hyperphagic period of late spring and early summer (Ramsay and Stirling 1988), when hunting conditions are most favorable (Stirling and Øritsland 1995), and extend the duration of the on-land period through which polar bears must survive on finite stores of body fat (Cherry et al. 2013). The resultant increased fasting has significant negative effects on polar bear body condition (Stirling et al. 1999, Rode et al. 2010a) and the increasing ice-free period has been linked to declines in survival (Stirling and Derocher 1993; Stirling et al. 1999; Regehr et al. 2010, 2007; Bromaghin et al. 2015). Longer periods of fasting and increased nutritional stress (Cherry et al. 2009; Molnár et al. 2010, 2014; Rode et al. 2010a; Regehr et al. 2010) have also been attributed to incidents of infanticide, cannibalism, and starvation in some polar bear subpopulations (Lunn and Stenhouse 1985, Derocher and Wiig 1999, Amstrup et al. 2006, Stirling et al. 2008a), although Taylor et al. (1985) suggested that cannibalism is not an uncommon phenomenon in polar bear biology. When on shore, some nutritionally stressed bears are highly motivated to obtain food however they can, and appear more willing to risk interacting with humans as a result (e.g., Stirling and Derocher 1993, Derocher et al. 2004, Stirling and Parkinson 2006, Towns et al. 2009). Increased frequency of hungry bears on land due to retreating sea ice, coupled with expanding human activity in the polar bear range, is expected to result in a greater risk of human-polar bear interaction and conflict (Stirling and Derocher 1993, Derocher et al. 2004, Stirling and Parkinson 2006).

To date, polar bear attacks on humans have been rare. When they do occur, they evoke negative public reaction, often to the detriment of polar bear conservation. In some communities, those negative reactions can persist for decades and result in less social tolerance for polar bears and increased defense kills (Löe and Röskaft 2004, Voorhees et al. 2014). Recurrent conflicts not only undermine the well-being of people and wildlife (Madhusudan 2003), they also negatively affect local support for conservation (Naughton-Treves et al. 2003). Therefore, the effective management of human-bear conflict is an essential precondition for the coexistence of bears and people across the Arctic (Madden 2004).

A primary management goal of the Range States is to ensure the safe coexistence of polar bears and people. In 2009, the Range States recognized the need to develop comprehensive strategies to minimize human-bear conflicts resulting from expanding human activities in the Arctic and a continued increase of nutritionally stressed bears on land due to reductions in sea ice (Directorate for Nature Management 2009). However, one of the difficulties in understanding and managing human-polar bear conflicts is that they are often poorly documented, particularly at the circumpolar level (Vongraven et al. 2012). Although considerable attention has been focused on understanding black (U. americanus) and grizzly (U. arctos) bear-human conflicts (Herrero 2002), there have been few attempts to systematically collect, analyze, and interpret available information on human-polar bear conflicts across their range (but see Fleck and Herrero 1988, Stenhouse et al. 1988, Gjertz and Scheie 1998, Dyck 2006, Towns et al. 2009). As a result, the public is left with misconceptions and misinformation regarding polar bears and their behavior, most of it driven by sensational media coverage. For example, it is commonly asserted that polar bears are the most aggressive of bears and polar bears are the only large predator that will actively hunt people (e.g., The Daily Mail 2008). An important factor that fuels such common folklore is that only a small fraction of the interactions between polar bears and people are reported; the exceptions are attacks that lead to human injuries or death.

To address these knowledge gaps and public misperceptions, the Range States tasked the United States and Norway with leading an effort, in collaboration with other polar bear experts and managers, to develop a system to collect and analyze data on human-polar bear conflicts (Directorate for Nature Management 2009). The result was the Polar Bear-Human Information Management System (PBHIMS), a database designed to document, quantify, and help evaluate human-bear interactions and other information relevant to bear management. We analyzed data entered into PBHIMS to characterize the occurrence of polar bear attacks on humans. We used this information to suggest methods to minimize the risk of future polar bear attacks to promote both human safety and polar bear conservation. We also identified data needed to best inform future management of conflicts. Although the PBHIMS includes other types of data that can be used to mitigate conflicts, we initially focused on attacks because they are the most extreme and undesirable encounters between humans and polar bears.

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