Cuddling Saves Lives – Mammal edition

Cuddling Saves Lives

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If you have ever found yourself in a tent on a cold winter's night or even your home when the heat gives out, cuddling for warmth always became part of the conversation. Though it is true that we humans always have the option to put on an extra pair of wool socks or multiple sweatshirts to keep in the heat, cold weather can and does claim the lives of many humans and animals. Now, I hope none of you has ever needed to pick an extended bear hug over not waking up the next morning. Cuddling can be shown to reduce body heat loss by up to 1/3, where without the embrace of a conspecific friend, winters tight grip would be too much to handle alone. Here I cover the many strategies mammals use to fight cold (and brutally cold) environments.

 

But First, Some definitions:

Lower Critical Temperature (LCT)

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Basically,

Your ability to withstand a cold temperature. 1° colder and you will not be able to keep your body warm enough to survive. We can increase this Temperature by putting on more and more clothing.

Torpor

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Think

Of it as a mini-hibernation, lasting less than 24 hours and comes in two flavours. 

Spontaneous Daily Torpor (SDT) - Triggered by short daylight hours 

Fasting-induced Torpor (FIT)- Triggered by thinking the keto diet is good for your kidneys. Ok, that's a lie, but it is triggered by prolonged bouts of burning bodyfat for energy. 

Hibernation

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True hibernation

Involves a decrease in body temperature, a reduction in respiration, and a decreased heart rate. It has been found that brain activity in animals that hibernate becomes so inactive that, they need to go through periods of arousal just to catch some sleep!² A true hibernator like the Columbian ground squirrel (Urocitellus columbianus) can decrease their normal body temperature from 90°F (32°C) to 39°F (4°C).  Remarkably, they stay in this state for up to 250 days out of the year.¹

Supercooling

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Allowing

Your core body temperature to drop below freezing.

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Mammal Examples

Click on the icons to see the adaptation

Orca

(Orcinus orca)

orca full

Large size - Reduced surface area relative to size. Minimizes heat loss

Blubber - Composed of connective tissue and fat, blubber helps keep heat from escaping. 

Reduced Breathing - Breathing less often reduces the amount of heat loss when breathing.

Countercurrent Heat exchange - Arteries in the limbs are surrounded by veins, Transfering heat from the arteries to the veins. then back to the core again.

Pika

Genus: (Ochotona)

pika

Small features - small ears, small nose, small feet all help reduce surface area.

Round Bodies - The perfect shape to minimise surface area to body mass, helping to minimize heat loss.

Thick hair - With thick undercoat, air cannot move easily close to the body, further reducing heat loss.

Love to be together - The ability to breed twice a year and large communal family groups allow pika to cuddle and conserve copious amounts of body heat.

Arctic ground squirrel

(Urocitellus parryii)

arctic ground squirel1

Supercooling - Coor temperature drops to as low as -2.9°C, Major organs slow down or even stop completely, making them appear dead.

Brown Fat - Located between their shoulder blades aids in warming their body during hibernation, keeping their head at a cozy 0.7°C, keeping them from becoming completely brain dead.

Time to Warm up - Every 3 weeks their body begins to shake like a Caribean maraca  (for 12-15 hours at a time). This brings their body temperature back to 36.4°C, enabling them to go through normal sleep cycles and other critical body functions.

White-footed mouse

(Peromyscus leucopus)

deet mouse

Cuddling - Normally a solitary and very territorial species. This mouse will gather into cuddling groups when the temperature begins to drop towards freezing. This cuddling behaviour helps them retain up to 1/3 of the body heat that they would have otherwise lost.

Shrinking organs - Male testicles decrease in size when exposed to short day lengths. This helps conserve energy by removing the interest in mating and calory consumption of large testicles.³

Nest Building -  Exposure to cold temperatures prompts the building of larger nests to keep in body heat.

Spontaneous Daily Torpor (SDT) - When the days get short, it's all about saving energy, even if there is plenty of food to go around. 

About Author

Evan Ogden

Writer for and owner of Search Wildly, Evan has devoted himself to bringing the wild into focus through accounts of his wildlife interactions and development of the search Wildy Application (on IOS and Android).

  1. Verts, B.J.; Carraway, Leslie N (1998). Land mammals of Oregon. Berkeley: University of California Press. ISBN 9780520211995. Retrieved 20 February 2015.
  2. Gail R. Michener, Seasonal Use of Subterranean Sleep and Hibernation Sites by Adult Female Richardson's Ground Squirrels, Journal of Mammalogy, Volume 83, Issue 4, 1 November 2002, Pages 999–1012.
  3. Young KA, Zirkin BR, Nelson RJ. Short photoperiods evoke testicular apoptosis in white-footed mice (Peromyscus leucopus). Endocrinology. 1999 Jul;140(7):3133-9.

 

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