MSGID: 1:317/3 6273535a   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Cold-survival strategies in animals: A spectrum, not either-or    
      
     Date:   
         May 4, 2022   
     Source:   
         University of Michigan   
     Summary:   
         Animals have three main strategies to survive the freezing   
         temperatures of winter: migrating, remaining in place and resisting   
         the cold, and reducing body temperature and metabolic rate in a   
         state called torpor.   
      
      
      
   FULL STORY   
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   Animals have three main strategies to survive the freezing temperatures   
   of winter: migrating, remaining in place and resisting the cold, and   
   reducing body temperature and metabolic rate in a state called torpor.   
      
      
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   These cold-survival strategies are often studied in isolation by   
   biologists and treated as mutually exclusive alternatives: An animal   
   species is described as either migrating or hibernating (torpor includes   
   both dormancy and hibernation), for example.   
      
   But in reality, many animals combine multiple strategies to beat the cold,   
   University of Michigan evolutionary biologist Giorgia Auteri explains   
   in the journal Biology Letters.   
      
   Warm-bloodedness is a cold-resistance strategy used by mammals and birds,   
   but some of these creatures also use a combination of migration and   
   torpor. For example, many high-latitude bats and birds such as swallows,   
   hummingbirds and warblers use both migration and torpor, Auteri said.   
      
   Sometimes, strategies are split among members of a species. Some blue   
   jays may migrate south while most state put, and individual eastern   
   chipmunks may shift from torpor to cold resistance when food caches are   
   abundant. The common green darner dragonfly exhibits tradeoffs between   
   migration and torpor, with more northern populations being exclusively   
   migratory.   
      
   "Each cold-survival strategy exists not as a binary but on a spectrum,"   
   said Auteri, who proposes an integrated conceptual framework for   
   examining cold- survival strategies in the Biology Letters article,   
   which was published online May 4.   
      
      
      
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   "Separate treatment of these strategies misses opportunities to identify   
   broader patterns and mechanisms and eliminates the possibility of   
   discoveries that require comparisons across strategies," said Auteri, who   
   primarily studies bats. She received her doctorate from U-M's Department   
   of Ecology and Evolutionary Biology this spring and will join the Missouri   
   State University faculty in the fall.   
      
   Among other applications, the proposed conceptual framework helps resolve   
   discrepancies in Bergmann's rule, which refers to the trend of larger   
   animal body size at higher latitudes. This trend purportedly facilitates   
   cold resistance due to the lower surface area-to-volume ratio among   
   larger animals.   
      
   However, small mammals and migratory birds deviate from Bergmann's   
   rule. A reassessment of this deviation under an integrated framework   
   for cold-survival strategies recognizes that species can use seasonal   
   migration or torpor as alternatives to cold resistance.   
      
   "This proposed framework, which considers cold-survival strategies   
   collectively, resolves the mystery of why some taxa 'break' the rule,"   
   Auteri said. "Small mammals do not follow the rule well because they often   
   use torpor instead of resistance. Migratory birds conform less strongly   
   because, like small mammals, they use an alternative -- migration."   
   Freezing temperatures are inherently challenging for life, which is   
   water- based. Cold-survival strategies for animals are fundamentally   
   about surviving energy deficits imposed by reduced solar energy in the   
   winter, with freezing temperatures and subsequent reduced productivity --   
   including food availability.   
      
      
      
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   How species cope with these conditions fundamentally shapes ecological   
   and evolutionary processes. But until now, there has been no comprehensive   
   conceptual framework for cold-survival strategies, according to Auteri.   
      
   In her Biology Letters article, Auteri proposes a framework with   
   four components for conceptualizing and quantifying cold-survival   
   strategies. She argues that cold-temperature resistance, torpor and   
   seasonal migration should be considered collectively; that species   
   can, and commonly do, use multiple strategies; that each of the three   
   strategies exists on a spectrum, permitting partial use; and that   
   species can exhibit proportional use, where the use of one strategy   
   correspondingly decreases other strategies.   
      
   Auteri said the new integrated conceptual framework can also be applied   
   to the study of animal responses to anthropogenic climate change.   
      
   For example, expected species range shifts are often evaluated based   
   on whether an animal uses hibernation or resistance or torpor as its   
   cold-survival strategy. The proposed framework encourages biologists to   
   study those strategies together when assessing a species' sensitivity   
   to climate change.   
      
   In addition, the new conceptual framework can be leveraged to answer   
   questions involving capacities for colonizing high latitudes, adaptive   
   tradeoffs, disease dynamics, niche partitioning, bioenergetics and how   
   changes in seasonal regimes impact ecological networks, Auteri said.   
      
   During part of the time Auteri spent working on the framework, she was   
   supported by the Helen Olsen Brower Memorial Fellowship, awarded by the U-   
   M Department of Ecology and Evolutionary Biology.   
      
      
   ==========================================================================   
   Story Source: Materials provided by University_of_Michigan. Note:   
   Content may be edited for style and length.   
      
      
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   Related Multimedia:   
       * Diagram_of_cold-survival_strategies_in_animals_and_photos_of_bats   
   ==========================================================================   
   Journal Reference:   
      1. Giorgia G. Auteri. A conceptual framework to integrate cold-survival   
         strategies: torpor, resistance and seasonal migration. Biology   
         Letters, 2022; 18 (5) DOI: 10.1098/rsbl.2022.0050   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220504110432.htm   
      
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