Polar bear diet in the face of Arctic climate change

The pole-warming effects of ongoing climate change and the position polar bears (Ursus maritimus) as top predators Arctic ecosystem meet at a precarious nexus, making this large mammal modern day “canary in mine.” Petherick et al. (2021) take pulse bear diet by examining key signatures microscopic attritional patterns on surface dental enamel. Through novel application well-developed tool, they provide four-dimensional perspective how has affected food choices through time. family, Ursidae, includes eight living species found mostly northern continents South America. Like other large-bodied members Carnivora, group that most terrestrial their relatives, have borne brunt shifts set motion prehistoric habitat destruction. Local extinctions or extirpations already been evidenced such grizzly arctos) California giant pandas (Ailuropoda melanoleuca) southeast Asia, plus several ursids were among casualties end-Pleistocene megafaunal (the short-faced Arctodus cave Ursus spelaeus lineage) across Holarctic. It is with backdrop come into focus vulnerable ursid an equally environment. Previous research shown are under attack from multiple threats to population ecological viability, genetic bottleneck (Miller al., 2012) masticatory system specialized for soft tissue-based adapted consuming only last 600,000 years so (Slater 2010). Thus, data can be used monitor important understanding changes ecology sea ice continues melt. Challenges associated monitoring several. Conventional tagging/tracking proven difficult environment (Durner 2009). Ad hoc observations kill feeding sites offer firsthand but partial view dietary (Brook & Richardson, 2002). On these challenges, longitudinal not easily deciphered, because historical collections specimens comprise processed prepared skeletons skins amenable all types analyses too rare warrant destructive analysis. A nondestructive methodology directly measures both desired advance our populations. One tool microwear texture analysis (DMTA), quantify enamel test hypotheses about Dental its roots mammalian herbivore (Walker 1978). In conventional analysis, 2D images tooth surfaces generated scanning electron microscopy (SEM) examined stereomicroscopes represent main sources; involves counting scratches pits summarizing numbers ratios those features spectrum grazers browsers. relatively simple conduct museum varying conditions, method requires quantification interobserver error make comparable studies researchers. DMTA provides two major advances over First, minimized sampling entire sections using confocal computed scale-sensitive indices topography rather than subjective counts vary appearance different magnifications. Second, could captured three dimensions, providing planar textural properties, also measurements topographic relief heterogeneity. Textural roughness (Asfc), uniformity feature directions (epLsar), relative size (tfv) replace small pits. These summarize physical (including ingested nonfood environmental particulates well tooth–tooth contact) recorded surface. timely practical heuristic reasons. Polar largest spend majority time land one few preferentially feed carnivores (DeMaster Stirling, 1981). Their unique niche makes them model organisms tertiary consumer interactions within webs, it means services cannot readily replaced predators. lineage relict sense, considering origin during Pleistocene glacial–interglacial intervals alongside very (e.g., bears, bears), being Ice Age extinct extirpated geographic range. Lastly, macroevolutionary terms, specialist carnivore lineages exhibit reduced evolvability periods abrupt (termed “macroevolutionary ratchet”; Van Valkenburgh, 2007), thus may predisposed exacerbated consequences rapid, anthropogenic perturbations given niche. Putting characteristics context, findings reported consistent scenario where hard-food consumption Alaskan remained low throughout times despite fluctuations temperatures 1000 ago end 20th century. lack significant signal pre-21st century suggests history operated bounds skull functional morphology This more alarming when authors report statistically increase 21st specimens. results reminiscent what was thought similarly tough Late hypothesis postulates late dire wolves mismatched magnitude deterioration decreased prey availability compounded increased competition, based elevated breakage frequency (Van Valkenburgh Hertel, 1993). However, do show increases gray bulk, time-averaged sample (DeSantis 2015). would interesting see if additional lines evidence gross-level landward harder tougher foods. Continued therefore prime push populations uncertain future. extent which undergo selection ability incorporate (i.e., harder) sources will pitted race against overlap between habitats former home ranges inland toward latter. Will rely hybridization adaptation changing environment, successfully shift hunting strategy reduce competition sister species, become casualty extinction event accelerating century? No matter outcome, future inextricably tied broader momentum “tipping point” Earth's biota managed here now. Data sharing applicable article no datasets analysed current study.