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There’s been a lot of fuss about caddisflies lately, thanks to the item on BuzzFeed (http://www.buzzfeed.com/babymantis/10-beautiful-things-created-by-animals-1opu) with pictures of caddisfly-assembled jewelry.
I was poking around my old saved blogdrafts, and found this from some years back that seemed appropriate. It’s a scan I made of some of my caddisfly case collection.
Caddisflies are insects in the Order Trichoptera, which means “hair winged” — and indeed they have tiny little hairs on their wings. They are rather related to the Lepidoptera — butterflies and moths. Adult caddisflies basically look like little tiny moths with long skinny antennae, while caddisfly larvae look like little caterpillars, and they also spin cocoons to pupate.
Except that caddisfly larvae live underwater, in streams and lakes. Not all build cases — some go around naked, some form little silk tunnels, while others build little nets with rocky goalposts to trap debris and food from the flowing current, like these Hydropsyche larvae I had in my aquarium once.
You can see this one using its silk glands to connect strands from one rock to another, and back and forth. (No word on what kind of web the crack-dealing caddis spins.)
A black-crowned night heron perches near the lighthouse on Alcatraz Island. Image courtesy of Roger Hothem/USGS.
Some of my great USGS ecology researchers will be giving a free public lecture this Saturday, October 29, 1:30 p.m. PDT in San Francisco as part of the Bay Area Science Festival.
Titled “Life and Death on Alcatraz Island: The Secret Life of Nesting Birds on ‘The Rock’” and hosted at 201 Fort Mason by the National Park Service, our biologists will share their knowledge from 20-plus years of research on Alcatraz.
We’ll focus in particular on the black-crowned night-heron, a secretive, twilight hunter that’s particularly useful in environmental contaminant studies, due to its position in the food chain. Additionally, herons have to coexist with nesting gulls and ravens on Alcatraz… and can often end up as raven food.
- Blogpost: http://www.werc.usgs.gov/outreach.aspx?RecordID=110
- News Release: http://www.usgs.gov/newsroom/article.asp?ID=3011
- Facebook Event Page: https://www.facebook.com/event.php?eid=203249386407172
Interestingly, a lot of these nest monitoring surveys requires the use of remote cameras hooked up to — you guessed it, DVRs.
So we’ve pretty much got these birds on TiVo and have to sit through a bajillion hours of footage to quantify behavior…
Fun activities for educators and kids include:
- Owl pellet dissections (from which kids get to keep the bones and goodies), which are similar to what we do to study raven diets.
- Ask a biologist Q&A session on what field work is like.
- Field work tools and props that kids can touch and hold, including the remote nest cameras and DVRs that we use to monitor nest behavior.
- Coloring sheets of some of the seabird species we work with.
For the more advanced geeks, we’ll have some technical posters and reprints of research articles on hand. Some of this data also will be presented at The Wildlife Society 2011 Annual Meeting the following week.
The first-ever Bay Area Science Festival has already made a big splash this week, and USGS will also host other hikes and even science pub crawls later next week. Details at the USGS news release.
Hope to see some of you there on Saturday! Follow at #basf11 and @bayareascience and of course @younglandis.
A parasitic isopod almost one centimeter long, which infests estuary crabs via "parasitic castration" and blocking the host animal's ability to reproduce. Image courtesy of Ryan Hechinger/UC Santa Barbara.
An old theory in ecology is that in any ecosystem, a small-sized animal species will be more populous than a large species.
All you need is a summer picnic to prove the point: your barbecue might end up attracting thousands of tiny ants — but only a few rotund squirrels.
Equations based on ecological theories like this one help scientists and wildlife managers predict resource abundance and the health of animal populations, such as to understand which species are naturally rare and approximately how rare they should be. But a new analysis published today in the journal Science has revised this particular rule of thumb.
“The theory should really also say ‘depending on your position in the food chain,’” says Ryan Hechinger, lead author of the study and an associate research biologist at the University of California, Santa Barbara.
Hechinger conducted the study along with Kevin Lafferty, a lead scientist at WERC’s Santa Barbara/Channel Islands Field Station, and colleagues from other universities.
Study authors Armand Kuris (back left) and Ryan Hechinger (back right) of UC Santa Barbara and Kevin Lafferty (front) of USGS. Image courtesy of George Foulsham/UC Santa Barbara.
Animal populations are often limited by their food supply and metabolic rate. A tiny animal burns fewer calories than a big animal, says Hechinger, so it needs to consume less food than a large animal to stay alive. “This is why small animals are usually more common than big ones,” adds Hechinger. “But the food chain is also important. There’s less food to go around the higher up the food chain you go. This is why top consumers like mountain lions are relatively rare.”
But ecologists know that despite being tiny, parasites also feed high up in food chains. “For example, a tapeworm that infests a deer feeds at the same food chain position as a mountain lion,” Hechinger says. “So we wondered whether parasite populations might be less common than you’d expect given the old rule.”
To explore whether tiny parasites exhibit the abundance patterns of top consumers, Hechinger, Lafferty and colleagues studied three estuary ecosystems: Carpinteria Salt Marsh in Santa Barbara County, CA, and Estero de Punta Banda and Bahía Falsa in Baja California, Mexico.
They counted and weighed parasites and other animals before confirming that parasites were indeed less populous than other similarly sized animals.
“But once we accounted for the food chain factor, a single, revised equation was able to explain observed population patterns for both parasites and other animals,” says USGS ecologist Kevin Lafferty, the study’s second author.
The findings also led to another profound revelation: regardless of species body size, species occupying the same position in the food chain can have the same rate of biomass production — annual yields in terms of weight. By this logic, a deer tapeworm population biomass and a mountain lion population biomass can grow at similar rates.
Shining, translucent eggs with little frog embryos await their release. Image courtesy of Ken Bohn/San Diego Zoo.
With Easter around the corner, Southern California biologists are playing bunny and hiding some 300 eggs in the wild.
But these are tiny, gelatinous eggs that belong to Rana muscosa — the mountain yellow-legged frog (also know as the Sierra Madre yellow-legged frog). And biologists are hiding these eggs in a chilly stream in the James San Jacinto Mountains Reserve near Idyllwild, California, in an ongoing, collaborative effort to preserve this endangered amphibian.
On April 14, researchers from USGS and the San Diego Zoo will release these eggs, which were laid by captive frogs at a zoo laboratory 90 miles away. This field expedition is part of a larger USGS-led partnership to study the Southern California population of the mountain yellow-legged frog, which is federally listed as endangered with only 200 adult frogs remaining in the wild.
