Friday Field Notes: On Bergmann's Rule, Ratios, and the Art of Staying Warm in Northern Climates

When MNHC's distinguished naturalists enter elementary school classrooms throughout western Montana this February for their monthly visit/natural history lesson, they will be discussing a fairly important ecological principle with 4th graders: Bergmann's rule. First articulated by German biologist Christian Bergmann (hence the name), the principle states that within a broadly distributed species or taxonomic group, an organism's body mass tends to increase with an increase in latitude (and the corresponding colder climate). While this principle has been most widely applied to mammals and birds, there are also examples of cold-blooded species that conform to the rule.

Why is such a principle observed in nature, you ask? Fundamentally, it is a function of larger animals exhibiting a decreased surface-area-to-volume ratio. Thus, larger-bodied animals lose less heat per unit of body mass, a characteristic that becomes vitally important in places like Montana where winters are long and cold. The following graphic helps better display this relationship:

Graphic displaying the mathematics underlying Bergmann's rule.

The important thing to note is the red text: While the larger cube has a considerably higher surface area, its volume has increased proportionately even more, thus lowering the surface-area-to-volume ratio.

Now, I know what you're thinking: Surface-area-to-volume ratios are a bit much for 4th graders. Most of us hadn't even heard of Bergmann's rule until our first college-level ecology course. But the science and mathematics underlying this stalwart of ecology can be easily explained and visualized. Consider this simple experiment, best suited for a brisk (32 degrees F or less) Montana winter day:

• Simultaneously fill up two cans of different sizes (i.e., a coffee can and a soup can) with near-boiling water. Place a thermometer in each can, and record the initial temperature.
• Place both cans outside. Record the temperature of each can every minute for approximately ten minutes.
• Afterwards, compare the change in temperature of the cans. The larger can should be significantly warmer than the smaller one, a result of its lower surface-area-to-volume ratio.

This simple experiment is a great way to test and conceptualize Bergmann's rule, and sheds light onto why being bigger is better when you live in northern latitudes. This fundamental relationship between surface area and volume explains why animals such as deer, elk, moose, and bears get larger as you move further north within their range. In some cases, the size difference can be quite dramatic. Male grizzly bears, for example, whose average weight is in the range of 500-1000 pounds in the Interior West, can reach up to 1,500 pounds in Alaska! In white-tailed deer, an incredibly far-ranging species, a similarly dramatic change is observed:

Bergmann's rule exhibited in white-tailed deer

So, if you're feeling guilty about those extra pounds you're still carrying around from holiday feasts or winter vacations, look on the bright side: You're going to stay much warmer this winter than you would without them!

Discover ways to involve yourself with MNHC this Fall!

photo by Merle Ann Loman

Visiting Naturalist Program

We're kicking off the program with introducing 3rd-grade students to bird beaks and feet and 4th- and 5th-grade students to the idea of naturalist as scientist, artist, and writer.  Staff naturalists visit the classrooms once per month throughout the school year, and lead activities that incorporate creativity with a scientific study of the natural world.  Volunteers are always needed (and appreciated) to help assist with classroom activities. 

miniNaturalist Program
Youngsters can come and discover the natural world all year round with our miniNaturalist program.  As brand-new naturalists, kids engage in nature with a series of sensory, imaginative and (sometimes) musical activities.  Last week, we talked about squirrels--what they eat, where they live and who might eat them.  Our miniNaturalists taste-tested seeds, learned about squirrel habitats and became a squirrel in their own Squirrel Play Production. The miniNaturalist Program is offered every first and third Thursday at MNHC from 10 a.m. to 11 a.m.  Admission is $3/non-member and $1/member.   

A Forest for Every Classroom
Don't worry, teachers, we won't let the kids have all the fun.  MNHC offers teachers a unique opportunity to learn about place-based education through seminars and workshops.  In the past, teachers have traveled to various places around western Montana, including Tarkio, the Blackfoot Valley, Seeley Lake, and the Bitterroot Valley, and met with various scientists, ecologists, forest service specialists, naturalists, ranchers, and conservationists.  This year-long program has two- three-day workshops in every season, which are designed to inform educators about what is going on in Montana's natural environment and how they can incorporate place-based education within their own curriculum. Educators are provided with supplemental course materials which offer a range of activities that can be used to teach children about anything from the wildlife diversity to patterns of change within the environment. We are currently recruiting interested educators  to be a part of our new workshop session which will begin in April 2013.

Fall Celebration and Auction
Celebrate with us on October 5 at the DoubleTree Hotel starting at 5 p.m.  There will be a silent and live auction with items graciously donated from artists, restaurants, designers, jewelry makers, and businesses throughout Montana.  Don't worry if you get tired from all that auction bidding, because the dinner menu includes salad, your choice of entree and a cookie sundae with Big Dipper Ice Cream.  If you're interested in attending we've made it easy!  Log onto our website at http://www.montananaturalist.org/ and follow the link to register and reserve your spot.

Interested in volunteering, learning about our programs or checking to see what's new?
Please contact MNHC Tuesday-Friday 12-5 at 406.327.0405

VNS May Field Trips: Insects, Part 2--Beetles!

There are 450,000 species of beetles, and they make up 40% of all insects. So, I hope you'll forgive me for not being able to identify all of the species we saw on our field trips! We caught some amazing specimens: brightly colored ones, iridescent ones, and just plain adorable ones. The kids were superb insect collectors, and only a few bugs were accidentally crushed in the excitement (one of which, I will admit sadly, was a sneaky common cricket that I was trying to recapture). I will do my best at telling you what I know about the beetles I got pictures of--or about beetles in general.

Here are the basic body parts of beetles, which I will refer to below. What isn't illustrated in the diagram is a section called the pronotum, or a portion of the front-most surface of the thorax. The shape and size of this feature is often very helpful in the identification of beetles.

Beetle #1: The lime green one on a pencil. 

Truly, I do not know what kind of beetle this is. It was a vivid, lovely color, though, and the kids who found it were ecstatic. 

 Beetle #2: The funny-colored lady beetle. Or, what reminds me of a Colorado Potato Beetle.

 This one came and landed right on my bracelet. He is shaped just like a lady-beetle--and there are 150 species of "ladybugs" in the U.S., so he very well could be one!

Entomologists think that lady-beetles may have spots to warn predators that they taste bad and can make them sick. See, ladybugs make a little bit of poison--just a little--and birds may be able to learn that a spotted beetle equals a terrible taste and illness.    

I'll admit, being a girl from a farm, my first thought was, wow, what a funny little, spotted Colorado potato beetle. Thankfully, this guy's pronotum and coppery-brown color set him off as something different. He's lovely, isn't he?

Beetle #3: A metallic-colored ground beetle (perhaps?)

 

If you Google the colors of this beetle (metallic green and copper-brown), you will get results for the notorious Japanese beetle--but this guy's colors are inverted and his shape is not the same. 

Do you know any of these beetles? If you do, tell us about them in the comments! We'd love to know!

VNS May Field Trips: Insects, Part 1.

The insects station is, by far, the most active one in the spring. Sure, the hikes have lots of walking, but at the insect station, we wander around, run with nets, dump and scoop bugs with caution and speed, and work hard to draw and inspect. We don't really try to ID, but, as you will find, it is difficult not to know what to call a specimen we find. Naming something, however, is only part of the process, and  being able to describe it or draw it in detail is also important. Simply observing and marveling at something is worthwhile, too!

Christine W. helping with a multitude of bugs!

After the sometimes cold and often surprising weather of the first two weeks of field trips, things warmed up, the sun came out, and jackets were shed or tied around waists and we were able to focus on the bugs in the nets and crawling around on us. At least, in theory, we could focus. Sometimes we had insects in a bunch of places, which led to a multitude of things going on all the time.

This little guy is an Anthocharis stella, or a Stella orangetip, butterfly. Along the Pacific coast, the subspecies is a Sara orangetip, and the Stella was thought to be a subspecies; but recently, scientists discovered that the two (Sara and Stella) will cohabitate without hybridizing. You can tell the difference, I've learned, by the color of their marbeled underwing: Saras are darker grey-green, and Stellas are pale mossy-green.

In general, though, you can just call them all orangetip butterflies, if you'd like.

They are such beautiful little creatures! Variations of this species are found all over the world. In some, the females are white, like cabbage moths. In others, like these, both males and females have orange tips, but males have more pronounced dark borders on white wings, while females have a yellowish tint and lighter mottling on the underside of their wings.

Isn't that wing marbling neat?

Look at this grasshopper we found! He was bright green with brown legs, wings, and eyebrows. No really--he had eyebrows! It was very cool.

Now, there are at least 11,000 verified species of grasshoppers (Kevan 1982; Günther, 1980, 1992; Otte 1994-1995; subsequent literature), but still, I'm going to go out on a limb and try to identify him. I think he's some sort of band-winged grasshopper. I didn't stretch out his wings, but if I had, I bet I would have found bands of color on them.

The kids absolutely had a blast! Look at these little naturalists!

VNS May Field Trips: Solo Hike.

Students on the solo hike get to put their naturalist skills they've learned to practice--all on their own. I heard many students say that they were surprised by how much they enjoyed being alone on a trail. A few times, they insisted they walk back along the solo hike trail in the opposite direction, again all alone.

Some discoveries:

A tiny, blue egg. I found it along the trail at Fort Missoula, and have yet to get a confirmation of what kind of bird it belongs to! Of course, it is most probable that it was a robin's egg--but it was definitely no bigger than a quarter. Could it have belonged to someone else?

 Here's a chart I found of the sizes of eggs (some of which are blue) from someone in Connecticut. An Eastern bluebird egg is the same size, approximately, as a Western or mountain bluebird.

http://www.sialis.org/nests.htm

European Starlings can also have blue eggs. Their eggs are darker and smaller than robins' eggs, a little larger than a bluebird egg, and glossy, but without any spotting. If you want to have a go at IDing the egg we saw, do so in the comments!

 

 This group of kids at Council Groves enjoyed walking alone, and really loved skipping rocks along the river afterwards. They seemed so enthralled by being alone that I had to run around to gather them back togther to share their discoveries from the solo hike!

 

 At Fort Missoula, kids ate their snacks all crammed into the big log. These girls were all telling each other about things they had seen, and it from a ways off it seemed like the log itself was chattering.

Spring at the MNHC!

As Allison said, so many exciting things have been happening this spring!

May ushered in the time of the year when we hold field trips for our Visiting Naturalist in the Schools program. This year, I had the opportunity to help with field trips held at Council Groves, Maclay Flats, and the Native Plant Garden at Fort Missoula, but field trips were also going on at a few other places. All hands were on deck. The warm weather (or, mostly warm) brought lots of exciting animals and plants out and about for all the naturalists to see.

For those of you who don’t know, Visiting Naturalist in the Schools is a program for grade schoolers (mostly fourth graders) aimed at helping young students develop their artistic, writing, and scientific skills to explore the world as naturalists. We do two “field study” sessions; the first is in October and the second is in May. Slightly different stations occur depending on the season. In May, we have three stations: the wildlife hike, the solo hike, and the insect study. These stations at the end of the year are especially exciting because we get to put all of the lessons we learned throughout the school year into practice. 

The next few posts are all about a few of the very exciting things we saw and experienced during VNS field trips in May!