Monsters of the Not-So-Deep

The myth of the large larvae is vindicated: we've found a second one! 
       About two weeks ago, we were wading across a very shallow, algae-covered South Platte River.  The air temperature was wavering around the high 90's, and even a few inches of cool flowing water provided refreshing relief from the heat!  The kids in the program were unsurprisingly hesitant to leave the river, and one boy was dragging his net as well as feet.  When we were at the point bar half way across the river, he suddenly gave a shout.
      "Hey, Miss E!  I caught you something!  What is it?"  The weird thing he held in his hand was a new find amongst a year's worth of poking under rocks for aquatic invertebrates*.  The creature was about two and a half inches long and the thickness of a very squashy pencil--HUGE for an aquatic larvae in this river.  For reference, most larvae we find in the river around 1/4 of an inch long. This one looked like nothing so much as a smooth, very large brown caterpillar with tiny tentacles coming out of one end, which end we weren't sure.
         Back in the office we excitedly made use of the internet to confirm the identity of the stranger.  Based on verbal descriptions (the river beast was left to cozy back up to his (her, its?) rock), we determined that the larvae was most likely that of a crane fly. 
      Like many of the tiny inhabitants we find on the underside of river rocks, the crane fly larvae go through amazing changes before they become adults, and by the time they are fully grown up, they have wings and are living entirely on land and in the air!  As adults, crane flies look like a large, elegant version of a mosquito.  The good news, though, is these bugs won't bite.  Crane flies feed on plants, plant debris, or other insects, depending upon the species.

Photo from the EPA public domain http://www.epa.gov/bioiweb1/html/craneflies.html

     The Jr. Rangers (10-12 year olds) turned up another crane fly larvae in the river today.  We're glad to find them here, and not just because they make for a curious creature to inspect.  Aquatic invertebrates serve an important role in our park.  They are the bottom of our food chain and provide a meal for larger animals such as fish.  In turn, those fish become food for even larger animals such as herons and other birds.  
     The teeny-tiny animals in our river also help us to know how healthy our river is.  Some aquatic invertebrates do not survive well if the water is polluted, too warm, or low in oxygen.  Crane fly larvae can only survive in water that is moderately clean^.  You'll have to look closely to find them though.  Crane flies and other larvae blend in well with the rocks that are their homes, but when you take the time to inspect with care, you never know what or who you might find!



*aquatic invertebrates: underwater insects and other underwater animals that do not have a backbone.  This group includes larvae, water spiders, crawdads, and many others!

^This is according to the EPA webiste, which states that crane fly do not survive well in polluted waters.

Discussion Questions:
1. What is the most surprising animal you have ever come across in the wild?  Where did you see it?

2. What are some factors that can make a river polluted?  Are there little ways you can help to keep a river clean?

Snake Awake!

western terrestrial garter snake

Warmer temperatures are bringing old friends wriggling out from under the rocks!  In school programs last week, someone spotted a garter snake on each day!  All the snakes spotted were near their holes, apparently sunning themselves on the rocks and getting ready to begin another active season.
 
So what have these snakes been doing all winter long?  Sleeping?  Not exactly.  Imagine if you decided that you disliked winter and curled up in your bed to sleep the entire season away from November through March.  What would happen?  You would wake up in need of food and water!  No matter how cozy your comforter may feel, humans are not designed to hibernate. 

Animals that hibernate must be specially adapted to do so.  In order to survive for an entire winter without food, they must use very little energy over the entire course of that time.  Mammals tend to build up fat reserves by eating lots in the fall.  This fat helps them survive through the long cold months.   When reptiles like snakes hibernate, they cope with the long period without food by loweing their body temperatures and heart rates.  Hibernating mammals may do this as well.  This is why it is important not to disturb hibernating animals that you may discover during the winter.  Reacting to you and attempts to escape may use up energy that animal needed in order to survive until spring.

Although garter snakes will allow their body temperatures to drop while they hibernate, they still must stay above a certain temperature to survive.  Hiding in a den underground is one way to stay warm.  A den like this is called a hibernaculum.  Another way to stay warm is to share the hibnernaculum with other snakes.  Garter snakes hibernate in aggregate, that means lots of them all together.  Sometimes they will even share a hibernaculum with snakes of a different species! 

In the spring, the snakes will become active once again, venturing outside the hibernaculum and eventually hunting for food and looking for mates. Since they have been hibernating in aggregate, you may see several snakes all close together as they emerge.  So next time you are in the park, keep your eyes open for snakes and other newly active hibernators!

Grazers of the Field

The field in front of the nature center has a new set of inhabitants this month: a lively flock of Canada Geese! 
     Winter is a stressful time to be a wild animal.  Colder temperatures, scarcity of food, and freezing water sources increase the difficulty of survival.  Most wild animals follow one of three methods to make it through the winter: tolerate, hibernate, or migrate.  Even within the same species, different groups of that animal may remain in different locations for the winter.
     Canada geese are great example of one kind of bird with several different winter options.  Canada geeses are usually migratory.  That means that
every fall they leave their summer homes and fly hundreds (or even thousands!) or miles south to spend the winter somewhere warmer.  In the spring, they must fly all the way back from their winter grounds to return to their summer homes to build nests and lay eggs. 
      Canada geese can tolerate a certain amount of cold weather (those down feathers are very warm!). To stay where they are all year long, however, open water where they can feed or find safety from predators is very helpful.  As a result, geese living far north in Canada or the northern United States may have to migrate south to find a lake that isn't frozen over for the winter.  If the geese live somewhere with a lake large enough and weather mild enough that there is open water even in the winter, then the geese can stay there year round.
    Colorado has winters that can be chilly and snowy.  Some geese that live here in the summer migrate down to New Mexico to escape the lower temperatures others stay and tolerate the cold.  In comparison to parts of Canada, Colorado winters are milder.  Most Canadian geese that live Canada migrate.  Some flocks stop and stay in Colorado all season, while other flocks continue further south for even milder weather.  As a result Colorado acts as a winter-only home for some geese, a summer-only home for others, and a year round home for some geese who do not migrate at all!
      Next time you are at a park or field, keep your eyes open for Canada geese.  South Platte Park has a flock of its own right now, if you want an idea of where to look.  Try to remember if you have seen this flock there before.  Do you think they are vistors, just stopping in on a migratory break, or year-round residents?  Chances are, they may have been flapping over mountains and valleys, rivers and dry plains just to be where they are today!

Check out our pages below for related ideas for classroom activities, parent/child activities, or crafts.
Upcoming programs related to this topic:
02/12/12-Home School Day: Winter Ecology, Ages 6-11,10am-12pm
02/14/12-Cooley Lake Hike
02/16/12-MLK Day Camp: Winter Wonders, Ages 6-11, 8:30am-4:30pm

By Request: Animal Detectives (School, Scout, and Group Programs)

ssprd.org/nature