You've got a lot a gall....

Wouldn't it be great if a teacher and students could study a plant, its herbivore, and the predators of the herbivore?  Ideally you'd want to study these three trophic layers of the system in a single class session, or perhaps two.  Of course, as an educator, you'd want all of this to happen very cheaply, or better yet, for free.

Warren G. Abrahamson, his colleagues, and a host of students have been working with just such a system for many years.  They have generously provided all of the tools necessary for teachers to share this system with their students.

Goldenrod species are found in most places in the United States and in many locations they are unwitting hosts to the goldenrod gall fly.  Female flies lay eggs into the growing tip of the goldenrod.  Chemicals released by the hatchling larva cause the plant to form a corky spherical gall about the diameter of a quarter coin.  The larva spends about 50 weeks in the gall feeding on plant tissue, growing, and pupating, before emerging as an adult to complete the life cycle.

Students in my evolution class collect a sample of about 250 galls during the first week of class in mid January.  For two years in a row now we have completed the task without the need for snowshoes.  We number and then measure the diameter of each gall using a plastic artist's templates designed for drawing circles of increasing diameters.  Next we carefully split the galls using pruning shears and use Dr. Abrahamson's online key to determine the outcome of the gall fly's efforts. I would say that the pruning shears are perhaps the most important tool for success with this research project; asking 20 students to cut hard spherical objects using knives might be a recipe for disaster.  As much as I respect and admire the work of the Saint Michael's College Rescue Crew, I'd rather not set myself up to need their services.

Gall fly larvae represent a high-protein meal when most other insects are underground.  A number of predators and parasitoids take advantage of the bounty.  Woodpeckers, chickadees, beetles, and wasps all partake in the fly larva feast.  In our most recent foray into the world of gall fly biology, we observed that already by January, 70% of the galls no longer housed gall fly larvae.

The entire sample of galls serves as a 'before predation' example; the subset that still contains viable fly larvae represents the 'after predation' survivors.  The data set is perfectly amenable to graphing using histograms and statistical analysis.

As predicted in the published literature, my students found that 2 bird species accounted for most of the larger galls, and many of the smaller galls hosted wasp rather than fly larvae.  The student data set shows strong evidence of stabilizing selection.  It seems that it is in this case better to be average than to be exceptionally large or small. 

By coincidence, my daughter's first-grade class used galls as a study system for life cycles and food webs during the same time period.  The first graders did not want to kill the larvae and so I was assigned to release them to 'the wild'.  The larvae sat in my car in a paper cup during a day when the temperature dipped to several degrees below freezing.  The larvae were as soft and squishy as when they were removed from the galls, despite the fact that my water bottle in the same car was frozen solid.  It was a nice illustration of the antifreeze properties of the larval tissue.

We will revisit the gall fly population on campus late in the semester to see if additional months of exposure to bird predation has further reduced the proportion of surviving flies. Dr Abrahanson's generosity in sharing what he has learned serves as an example to all of us academics studying our sometimes obscure topics.  We have each in our own way figured out how to wring data from all sorts of bizarre systems.  There are tricks that we have learned from colleagues or gleaned from conferences.  We should share these tips! 

The images used on this page are from Wikimedia Commons:
http://commons.wikimedia.org/wiki/File:SolidagoGall-AcheneSK.jpg 
http://commons.wikimedia.org/wiki/File:GoldenrodGallFlyLarva.jpg

Digital Coyote

Large natural history museums typically display only a tiny fraction of the specimens that they house.  Unlike art museums, natural history museums frequently place replicas in the public view while the real specimens are stored under the watchful eyes of curators and back-room researchers.  Access to stores of research specimens is tightly controlled and can involve a written application that is vetted by other scientists.

Much of the research and education that could be done on preserved specimens requires large numbers of replicate individuals so that statistical analysis can be used to support the conclusions we may draw.  Hands-on access to a large collection is beyond the reach of many small institution researchers and out of the question for most teachers.

To address this disconnect between education and museum collections in a small way, I decided to create a virtual museum.  I first accumulated enough coyote skulls from diverse locations to provide a hands-on activity for my own students.  Next I recruited two bright hard working students to very carefully photograph each skull with a scale bar in place.  From an initial collection of about 10 found skulls, I have expanded by contacting taxidermists and ebay sellers from around the country.  I now have more than 60 carefully numbered and curated coyote skulls.

The virtual museum is slowly coming together.  We photograph each from left, right, top, and bottom and include a ruler in each photograph.  Thus far we have uploaded 35 sets of photographs and made them available on Wikieducator.  We have found that the skulls can be measured from the photographs within 1mm of accuracy.  A small number of the skulls were treated using bleach and will deteriorate to dust over time.  For these crumbling skulls our photographic record may be the only one that survives.

Using the online collection, it is possible to compare populations from east and west and also to look at latitudinal gradients.  The site may also be applicable to statistical courses in that students can generate their own data rather than relying on fake data.  We hope to also add a collection of domestic dog skulls to illustrate the difference between naturally selected species and an artificially selected domestic species.  The chiwawa skull photographed next to a grey wolf above is an example from that collection.

What will I be when I grow up?

At some level I have always been fascinated by living things.  All through my childhood I collected frog spawn and watched the tadpoles emerge in plastic buckets in my back yard.  Hedgehogs that wandered near our house were frequently detained and kept as pets.  I grew cactus plants in a shed my father built for the purpose and my brother kept, and continues to keep cage birds.  For me, the Natural History Museum in Dublin was essentially a place of pilgrimage.

I suppose that many children go through phases like this, but not all of them end up as professional biologists.  As a child, it never occurred to me that one could really get paid to collect caddisflies, skulls, and pressed flowers.  The only contact I had with scientists was through the Regional Veterinary Laboratory where we dutifully sent the little feathered carcasses of departed birds from my brother's aviary.

But it turns out that it is indeed possible to get paid and indeed have a career observing birds, sampling lizards, or collecting insects.  What makes it possible for a youngster to realize such a strange fantasy and make a living studying the amazing organisms that share the planet?  This question occurred to me recently when reading a blog written by a 10 year old.  Jake's bones was started by a Scottish school boy when he was seven. Jake photographs and documents skulls and bones he has collected.  He takes an amazingly sophisticated scientific approach to his collection and his blog.  One page includes advice for others interested in collecting skulls and skeletons and he has one prank page devoted to the "wild haggis".

On reflection, I can see what Jake has in common with a boy who grew up in Athlone in Ireland.  Both of us were encouraged by excited parents to pursue our interests.  Each of were given the support and space explore hobbies that less enlightened parents may have dismissed as weird.  And let's be frank and honest here, collecting pinned insects, or dealing with the stinky process of cleaning skulls, if not weird, is a tad unusual.  But what's so bad about being unusual?

So, my suggestion for parents everywhere is that you encourage your child's passion for the unusual or the ordinary.  Whatever holds her attention for longer than average is a potential avocation.  Your son writes poetry?  Cherish those poems; frame them on the fridge; submit them to a newspaper!  The hobby that may simply appear to be a time filler could be a life-long passion that becomes a career.  And what better career could one have than to get paid for something one chooses as a hobby.  I tell my students that they should regularly have a few moments in their job when they can smile and say "yes, I get paid for this".  Not every hobby becomes a career, but every hobby adds color to our lives and makes us more interesting and interested human beings.

Head first

A student recently found a nearly intact coyote skull near campus.  He did a nice job cleaning it up and agreed to sell it to me for teaching.  I was impressed by it's large size and it started me on a minor quest.  I needed a lab activity to look at geographic variation in a species.  Any species would do and coyotes seemed to be a as viable a candidate as any other.  They occur in 49 out of 50 US states; Hawaii being the exception.  There are no hunting restrictions and in many places they are killed as pests.  So I have made it my business to accumulate some more specimens.  It goes along with my brother's suggestion to name my blog "dead things" I suppose.

The size of the first skull struck me as unusual.  I had considered coyotes to be somewhere in the range between foxes and wolves, and I had naively considered them to be nearer the fox end of the scale.  Red foxes top out in the 15kg range.  Coyotes, I learned can be more than twice as large as the largest red fox.  There are good reasons to expect a Vermont coyote to be larger than average.  Coyotes in the northeast United States are generally considered to be the product of hybridization between western coyotes and wolves.  The hybrids colonized the northeast during the early part of the last century and have expanded their range since then.

Bergmann's rule is a reason to expect coyotes in the north in general to be larger than those in the south.  The idea is based on thermoregulation.  If an animal gets longer in one dimension, it's skin surface area gets larger by a square function of that linear dimension.  Body mass increases by a cube function of the linear dimension and so overall, larger animals have a larger surface to volume ratio.  Bergmann's logic was simple: large mammals can better thermoregulate in cold conditions and so we should expect to find the larger examples farther north.

So, are coyotes in the northeast larger than western coyotes?  Do we find the largest coyotes as we travel farther north?  These are the questions my students will answer during my spring course.  To answer questions such as this requires a large sample of skulls.  I have accumulated more than 30 specimens thus far from 14 states from Texas to Alaska and a single specimen from New Brunswick Canada (based on all logic it should the largest one; it is not...).

You may wonder how one goes about acquiring 30+ skulls?  Is there some professional network of biologists bartering skulls for insect specimens?  Perhaps a biological supply house meets the demand?  It turns out that the source is far more pedestrian......Ebay!  And I should point out that I have had skulls donated by trappers in Texas and New Mexico.

What's down there?

Beyond the bounds of the scientific questions I like to ask about biological communities, I frequently just want to know what organisms live where. In shallow streams and ponds I can simply reach down with a net for the answer. Deeper lakes present a slightly larger challenge. Biologists before me have risen to the challenge and designed an array of amazing devices to get to the bottom of things.

A collaborator recently needed benthic samples from 5m deep in Lake Champlain. My petite Ponar dredge was the obvious tool for the job. It's called 'petite', because the full size version must be lifted using a winch. The petite version can be lifted, deployed, and recovered with just a little elbow grease.

The device is lowered on a line into the lake and consists of two weighted jaws held apart by a sprung pin. When the sampler embeds in the lake floor and the line goes slack, the pin springs out. A tug on the retrieval line brings the jaws together and a sample of the lake floor is collected. The lake floor organisms can be seen after some washing in a sieve bucket to remove the fine sediment.

So what's down there? Well, the sample I took in November was overwhelmingly dominated by striped mollusks native to the Baltic region of Europe. Zebra mussels came to Lake Champlain via the Laurentian Great Lakes. Because of their filter feeding activity, they shift food resources from the water column to the lake floor. One result of this is increased abundance of other benthic organisms. The other organisms in my sample included the larvae of midges, caddisflies, and mayflies along with 2 snail species. That's quite a bit of diversity for a square of lake floor measuring just 9cm on each side.

An important lesson can be learned from this sample. Zebra mussels are extraordinarily abundant and can easily attach to any equipment used in an infested lake. To contain these invaders, it is essential to clean and then dry all equipment between uses in different water bodies.

Birds eat pumpkins?

This seemed like an appropriate posting for today. My family and I carved pumpkins yesterday and left them outside overnight for the big day. At around lunch time today I noticed that most of our pumpkins had been attacked! I found small triangular dents, suggestive of bird beaks on most of them. The gourds that form the eyes of one pumpkin had fairly deep holes in them; I actually liked the effect. One pumpkin lid was entirely missing.

I took a quick look around online to see if this is a widespread phenomenon and it does not seem to be the case. A host of six-legged pests is listed along with snails and slugs on several pest management sites, but I can find no mention of birds. Perhaps the birds have focused just on me......or not.

I found a couple of blogs discussing pumpkin seeds as bird food with an array of advice (cook them ; don't cook them; sprout them...). One site recommended pumpkins as a source of beta carotene for birds. I can't say I have ever tried to feed pumpkin to birds, but it seems that the birds have helped themselves to them. My kids seemed oblivious to the vandalism, so all was well for the festivities.

Has anyone else had birds feasting on their pumpkins? I see that one person has had squirrels eating his pumpkins and with rather convincing documentation

Spied a spider?

I recently had the pleasure of spending the night on an island in Indian Lake in the Adirondacks. While foraging for firewood on the northeast end of our island, my son and I found a large fishing spider sitting on a rock. She was carrying an egg mass under her body and sat still for some photographs.

Somewhere I had read that fishing spiders ran across the water surface to prey upon invertebrates trapped in the surface film. I assumed that with a 6.7 cm leg span, this must be the largest spider in our region. But with a little digging, I learned that at least one local wolf spider species is larger.

Far more interestingly, the fishing spider does not limit its menu to invertebrate prey. While they typically consume invertebrates, they are occasionally true to their name and can actually catch fish more than four times their body weight (Bleckmann and Lotz 1987). The spiders use ripples on the water surface to detect prey, including water striders. They move rapidly across the water surface by rapidly retracting their legs and then gliding before again making water contact. All of this happens so rapidly that Gorb and Barth (1994) who described the behavior could see it only using high-speed photography.

View Indian Lake in a larger map