Drent, R. H.

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Life in the polar winter - epilogue
Drent, R. H.
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Arctic
DOI:
10.14430/arctic1533
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1991
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Drent, R. H. (1991). Life in the polar winter - epilogue. Arctic, 44(2), 163-164.
https://doi.org/10.14430/arctic1533
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EPILOGUE / 163 
Epilogue 
Although the papers presented here do not have the 
pretension  of  exhaustively  reviewing the adaptations enabling 
survival  through the polar winter, the range of  organisms 
covered  nevertheless  allows one to discern recurring themes. 
For the endotherms it is  tempting to set the current views 
against the background  of the generalizations arrived at by 
Scholander and his  co-workers (Scholander et al., 1950) in 
their key papers cited repeatedly during the Life in the Polar 
Winter  conference. We can ask why the paradigm  of New- 
tonian cooling advanced at  that time has been  such a suc- 
cessful  approach to the problem  of  cold adaptation  and to 
what  extent the conclusions  based on  the wide-ranging  survey 
undertaken then are still valid  today. 
The  simple  physical  model  (Newtonian  cooling)  employed 
by the Scholander  team  had the great virtue of  reducing the 
characterization of  physiological adaptations to a small  set 
of values (conductance, resting metabolic rate, the lower 
critical temperature and core  body temperature), allowing 
prediction of cost at defined ambient conditions. More 
important, species could be  readily  compared  using these 
basic  measurements,  which  could  be  achieved using modest 
resources during relatively short-term trials with animals 
brought in from the wild. 
The  basic  tenet  of the Scholander view  was that adaptation 
to arctic  life  primarily  entailed the acquisition (or perfection) 
of  effective insulation, thus allowing  cold  exposure  without 
excessive  costs. This basic  realization has been  brought  home 
dramatically by empirical  measurements  presented at this sym- 
posium  and  is  exemplified  by the small  arctic  fox,  whose  pelage 
thickness  is the most  effective  insulator  known.  Although  these 
measurements  confirm the utility  of  using  fox furs for caps, 
hit  upon by trial and error by the earliest  Europeans to winter 
in the polar regions, it is  difficult for us  (as transplants from 
a tropical pedigree) to appreciate that these  small  mammals 
can  withstand  temperatures  down to -25OC without  shivering, 
indeed  without  added  metabolic  cost. 
The metabolic savings are complemented by an absolute 
economy in exposure to the elements. The smaller arctic 
endotherms  demonstrate a mastery in exploiting  shelter, and 
indeed the winter  biology  of the ringed seal is intimately 
bound up with the utilization of  chambers  under the sea ice. 
Presence  of suitable shelters defines local distribution of the 
arctic  fox,  and  survival through the harsh  winters  of northeast 
Asia, with temperatures of -4OOC, is feasible for willow 
ptarmigan  because  they  shelter  beneath the snow and venture 
to  the surface for only brief foraging forays. 
The accumulation  of fat deposits as  an emergency supply 
in the ensuing winter has been explored quantitatively in 
several  species. In ptarmigan and the arctic fox  these  supplies 
suffice as  an emergency supply only, and  the detailed work 
reported in Oritsland (1986) points to a similar role for fat 
in reindeer, sufficient only to bridge catastrophic conditions 
during the Spitsbergen  winter.  These  findings  imply that over- 
winter survival cannot be assured simply by anticipatory 
energy  accumulation but must  depend  primarily  on the ability 
to maintain a balance between intake and expenditure 
throughout. In some  species (notably the arctic fox) an addi- 
tional buffer in the form  of  cached  food  can  be  drawn upon 
when hunting conditions are unfavourable. 
The ultimate economy  is  entailed by  lowering  of locomotor 
activity, often hand in hand with the use  of shelters alluded 
to earlier when discussing Andreev’s work on  the willow 
ptarmigan. In  the related  rock ptarmigan, Mortensen and 
Blix (1989) found that when  birds  caught on Spitsbergen were 
maintained in outdoor  enclosures in arctic  Norway,  food  con- 
sumption at midwinter was in fact only half that during 
summer, and these  workers  surmised that changes in activity 
costs accounted for part of  these  savings. In the wild, the 
necessity  of  economizing during winter  is  emphasized  by the 
dramatic fall in food quality available for browse (willow 
ptarmigan, see Brittas, 1988). 
The salient features enabling successful  wintering  by  man 
(use  of  shelter,  food  caches,  effective clothing with  high but 
adjustable insulative  value and avoidance  of  excessive  expen- 
iture) are thus themes recurring among  the wild fauna. 
Apparently the use  of external heat (fire)  is the only feature 
unique to man.  The  ultimate  reliance  on  cached  food  is  vividly 
brought to mind  by  Richardson’s  account  of the return of 
Franklin’s exploring party to the arctic coast of central 
Canada  in  the fall of 1822. The caloric budgets worked out 
by Houston (1984) make  it  clear that a successful  crossing 
of the area appropriately known as the barrens at this time 
of  year  was only possible by boiling moccasins and caribou 
hides left behind  from a previous  winter  camp. 
The need for avoidance strategies was thus early 
appreciated but only recently has their effectiveness  been 
quantified. Features requiring redoubled attention include 
the scope of  energy  savings incurred during prolonged star- 
vation by lowering the metabolic rate, an adaptation 
emphasized in discussing  survival  of the arctic fox  under 
inhospitable conditions. The fact that hibernation as an 
escape strategy is  available to only few members  of the arctic 
fauna was also brought up during the conference. The 
impressive  ability  of  arctic fauna to cope  with the polar winter 
must not blind us to  the fact that from time to time a combi- 
nation of  extreme cold and unfavourable feeding conditions 
leads to  an exhaustion of the short-term bridging fat supply 
and massive mortality may  result  (see Oritsland, 1986, for 
documentation). 
These observations imply that carrying these  emergency 
supplies has a very  real  cost  (indeed  some 15% of current 
energy  expenditure in the rock ptarmigan, according to Mor- 
tensen and Blix, 1989) and  that only “average” interruptions 
in the food supply can  be  accommodated. The disaster years 
familiar to anyone  working in the Arctic - exemplified by 
near total failure of reproduction in the hardy Svalbard 
reindeer,  coupled  with  heavy  overwinter  mortality  of the adult 
animals (80% starvation) - emphasize that  the challenge 
of arctic survival  resides not only in surmounting  extreme 
cold but in withstanding an unpredictable variance in con- 
ditions. In the economy  of  survival the margins are narrow. 
The  vivid accounts of  ongoing  research  presented during 
the symposium and in this issue underline the shifting 
emphasis away from  relatively short-term incursions to the 
arctic  environment to capture specimens for subsequent  study 
towards long-term work  by  teams  of  investigators  following 
individual animals over long periods (maintaining contact 
by an impressive array of telemetric devices). The challenge 
of the years  ahead  will  be to trace the web of adaptation 
through the food chain by close collaboration among 
specialists. In  the case of  herbivory, cooperation between 
botanists and zoologists alluded to by Sonesson has already 
164 / EPILOGUE 
revealed the intimate links  connecting animal numbers  with 
their food supply and especially  with the persistence  of the 
preferred  vegetation  (see  also  Jefferies, 1988). The close fit 
between the overall  standing crop of  vegetation and peak 
reindeer biomass across a range of arctic sites,  even 
extrapolating to an accurate prediction of the carrying 
capacity of the sub-Antarctic  island South Georgia,  argues 
for  the pervasive  influence  of  food  supply as against  the tradi- 
tional  interpretation of populations  kept  in  check by predators 
(Leader-Williams,  1988). It is against  this  background that 
the exploitation patterns of man must  be  viewed.  From the 
recent  physiological  work  undertaken on the  members  of the 
Finnish polar expedition, it is reassuring to note that urban 
man has not lost the ability to acclimatize to the dramatic 
extent  envisaged  by  Hammel(1964), and more  surprises may 
be in  store for us. 
REFERENCES 
BRITTAS,  R. 1988. Nutrition  and  reproduction  of  the  willow  grouse Lagopus 
lagopus in  central  Sweden.  Ornis  Scandinavica 1949-57. 
H A " E L ,  H.T. 1964. limestrial animals in cold Recent  studies  of  primitive 
man.  In:  Dill,  D.B.,  ed. Handbook of  physiology.  Section 4 Adaptation 
to the  environment.  Washington, D.C.: American  Physiological  Society. 
413-434. 
HOUSTON,  C.S.,  ed. 1984. Arctic  ordeal:  The  journal of John  Richardson, 
surgeon-naturalist  with  Franklin, 1820-1822. Kingston:  McGill-Queen's 
University  Press. 
JEFFERIES, R.L. 1988. Vegetational  mosaics,  resources and  plant  growth 
in response to grazing.  In:  Gottlieb,  L.D.,  and  Jain,  S.K.,  eds.  Plant  evolu- 
tionary biology.  London: Chapman & Hall. 
LEADER-WILLIAMS,  N. 1988. Reindeer on South  Georgia.  Cambridge: 
Cambridge  University  Press. 
MORTENSEN,  A.,  and  BLIX,  A.S. 1989. Seasonal  changes  in  energy  intake, 
energy  expenditure,  and  digestibility  in  captive  Svalbard  rock  ptarmigan 
and Norwegian  willow  ptarmigan. Ornis  Scandinavica 2022-28. 
ORITSLAND,  N.A.,  ed. 1986. Svalbardreinen  og  dens  livsgrunnlag.  Oslo: 
SCHOLANDER,  P.F.,  HOCK,  R.,  WALTERS,  V., and IRVING,  L. 1950. 
Universitetsforlaget. 
Adaptation  to cold  in arctic  and  tropical  mammals  and  birds  in  relation 
to  body  temperature,  insulation,  and  basal  metabolic  rate.  Biological 
Bulletin 99259-269. 
SCHOLANDER, P.F., HOCK, R., WALTERS, V., JOHNSON, F., and 
IRVING, L. 1950. Heat  regulation  in  some  arctic  and  tropical  mammals 
and  birds.  Biological  Bulletin W237-258. 
SCHOLANDER, P.F.,  WALTERS,  V.,  HOCK,  R.,  and  IRVING,  L. 1950. 
Body insulation of  some arctic  and  tropical  mammals  and  birds.  Bio- 
logical  Bulletin 99225-236. 
R.H. Drent 
Biology  Centre 
University of Groningen 
Groningen, The Netherlands 


Life in the polar winter - epilogue

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