Frozen Critters

Ponds in the winter time appear to be lifeless, with little wildlife around. The air is cold, weather poor and water frozen, but living things may be found. As a follow-up to Pondering, this module will investigate the pond life in the winter, looking for any signs of wildlife around or in the pond. Students will record the status of the pond and compare it to the pond in the fall, discussing any changes or similarities between the seasons. The main activity for this module will be journaling but various games can be played that relate to pond life.

Where did the pond life go?

Amphibian - become dormant; hibernate for the winter 

Green Frog - go to bottom of pond, stream or lake

Leopard Frog - go to bottom of pond, stream or lake

Pickerel Frog - go to bottom of pond, stream or lake

Spring Peeper - winter on land; hide under leaf litter on forest floor

Wood Frog - winter on land; hide under leaf litter on forest floor 

American Toad - burrow on land; below frost line

Red-spotted Newt - burrow on land; below frost line

Spotted Salamander - burrow on land; below frost line

Blue-spotted Salamander - burrow land; below frost line

Freeze Tolerant Frogs

Just like salamanders, newts and toads, wood frogs and spring peepers hibernate on land during the winter months. Unlike salamanders, newts and toads, wood frogs and spring peepers are not very good at digging. So while the other terrestrial hibernators are buried below the frost line beneath layers of soil, wood frogs and spring peeper are just hidden beneath leaf litter as far as they can dig, usually above the frost line. In order to survive the winter exposed to frost these little organism have become freeze tolerant; the ability to endure formation of ice in the body.

There are many dangers to allowing ice to form within the body.

  • blood vessels can puncture; cells squeezed and deformed
    • damage organs
  • severe dehydration can result
    • 65% of the frogs total water is gone to ice
  • delivery of oxygen and nutrients can be interrupted
    • blood stops flowing
    • no breathing, heart beat or muscle movement
      • appears to be dead; a "frogsicle"

A benefit to hibernating on land is as soon as the snow melts these amphibians can begin to breed in temporary ponds and ditches. The aquatic hibernators are trapped underwater until the ice melts. 

To avoid damage the freezing has been confined to extracellular spaces; outside of cells, tissue and organs. Therefore the extracellular spaces must be freeze tolerant and intracellular must be freeze avoidant.  

  • body freezes slowly to allow time for adjustment
  • high amount of sugar and sugar alcohols remains in tissues; glucose
    • acts as antifreeze
    • cells, tissues, organ do not freeze, only extracellular spaces around them
  • have enhanced the ability for organs to survive without oxygen
  • when thawing the level of clotting protein increase therefore if bleeding starts; clotting take place much quicker

Click here to watch a video on this phenomenon.

The ability of the spring peeper and wood frog to tolerate freezing is quite incredible. While it is a risky move, these frogs have adapted in this way to survive frost and a get a jump on reproduction.

Birds

American Black Duck 

  • northern population migrate south 
  • PEI is both a wintering and breeding area
  • groups are seen in open water
    • possible to see some on pond; depends on ice 

Invertebrates

Dragon Flies

  • overwinter as larvae
  • emerge in early summer

Water Boatman and Backswimmers

  • overwinter as adults
  • can be seen swimming, even under layer of ice

Go visit a pond. Take note of the wildlife you see. Listen for birds, look of invertebrates and just enjoy the tranquility of the area!

Back to Frozen Critters.