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Thursday, May 31, 2012

Black Rats, Brown Rats, and the Plague

I've been spending a lot of time thinking about rats. Thankfully, it is not because I have a problem in my apartment! Unfortunately, for many people in L.A., rats are a serious pest, and it's not just one type of rat. The most serious rodent offenders in our cities are the brown (aka Norway) rat, Rattus norvegicus, and the black rat, Rattus rattus.

What species of rat is this?

Here on the North Campus we have camera trap images and footage of rats hanging out underneath the bridge. But what type of rat is this? Since Jim Dines, our Mammalogy Collections Manager, wasn't available, I decided to try and figure it out myself. Doing a Wikipedia search for brown rats, I came across a nice diagram that helped me to make an identification. What species do you think it is?

Comparison of the physique of a black rat, Rattus rattus
with a brown rat, Rattus norvegicus, from wikipedia


Using this diagram I looked closely at the ears and the eyes of the rat. Based on the relatively large size of the ears and the eyes, I determined the above image was of a black rat rather than a brown rat. I showed the image to Jim and he confirmed that it was indeed a black rat!


Black rat (top) and brown rat (bottom) from the Museum collection.
Note the tail to body length ratio.

Regardless of the species, why do people hate rats? As I referenced in the introductory paragraph, rats are sometimes pests in our homes, but what exactly do people think about rats? I did a Google search for, "why do people hate rats," and this is what I found. "Cute or not they're germ-ridden disease carrying vermin who in addition, can cause untold damage. THAT'S WHY." I also found this: "Rats are pests to humanity, but I personally believe that people especially hate rats because they subconsciously identify with them and see them as a reminder of themselves." Finally, someone else wrote: "A lot of rat-hatred goes back as far as plague. Rats were responsible for the disease that killed thousands of people."

But, is plague a worry for us today in L.A.? Not really here in the city (I hear a collective YAY)! Firstly, according to the Centers for Disease Control and Prevention the last cases of urban, rat-associated plague occurred in L.A. in the 1920s. However, plague is present in L.A. County, and the principal mode of infection is from infected fleas living on wild rodents in rural areas. These rodents include California ground squirrels (remember the recent blog post?) and chipmunks! According to L.A. public health officials, "the major threat of plague to humans is in the rural, recreational and, wilderness areas of the Angeles National Forest, as well as the Santa Monica and San Gabriel Mountains." But, before you swear off recreating in our lovely parks forever, know that there have only been four cases of the plague in L.A. since 1979, none of which were fatal (another YAY for antibiotics and modern medicine).

P.S., Plague is actually caused by a bacteria, Yersinia pestis, that lives in the blood and other bodily fluids of fleas, rodents, and other mammals.




Friday, May 25, 2012

Kindergartner Finds Greater Yellow Underwing Moth on North Campus

This past weekend the Museum hosted the 26th annual Bug Fair. Over the course of 72 hours, more than 10,000 people visited us. These lucky visitors got to see, do, and taste many things. At Curator of Entomology Brian Brown's table, visitors were able to see the world's smallest fly from Thailand (oh and it just happens to be a brand new species in the genus Euryplatea). On our insect stage, they could meet Western Exterminator's bed bug sniffing dogs. If people were hungry, they could head outside and taste some insectuous delights including Orthopteran Orzo, a la Bug Chef David George Gordon, or wax worm salad prepared by entomophagy expert Dave Gracer. If they were interested in hunting bugs rather than eating them, we also held bug hunts out in the Erica J. Glazer Family Home Garden.

Everyone was bug hunting

With over 300 people participating in the hunts on both Saturday and Sunday, you won't be surprised that we found a lot of insect diversity. There were many European honeybees, ladybugs, flower flies, and Argentine ants. There were also some insects that I'd never seen before, including an impressive underwing moth that was collected by Kindergartner! It just goes to show that Citizen Scientists are just as likely to make cool and scientifically interesting discoveries as our Museum scientists are. The moth is now our latest addition to the North Campus species list.

Chris Weng, age 6
 One of our newest Citizen Science converts

Check out those underwings!

The moth Chris found is a Greater Yellow Underwing, Noctua pronuba. Although you would expect the hind wings of this moth to be yellow, they in fact range in color from yellow to orange depending on the individual. This moth is native to Europe and was accidentally introduced into Nova Scotia in 1979 (the year I was born). Over the last 33 years the moth has spread throughout much of North America and can now be found here on the West Coast in many areas including Alaska, California, and British Columbia. This spread is not looked upon kindly by many gardeners and farmers, as the caterpillar is a pest. They feed extensively on a variety of herbaceous plants including grapes, strawberry, tomato, potato, carrot, cabbage, beet, lettuce, and many grasses. Over the last week, I've found many more of these moths around the North Campus. One of our Gallery Interpreters, Vanessa Vobis, also found one in her garden at home. Are they in your yard too?

Thursday, May 17, 2012

Pond Babies: Dragonflies and Diving Beetles

Two weeks ago I told you I'd fill you in when I found dragonfly nymphs in our pond. I wasn't expecting to be able to give you this update so quickly, but SURPRISE, nature moves fast, people! In the last few weeks, I've found more than 50 dragonfly exuviae (the papery exoskeletons shed between molts) attached to the rocks of the pond. Of course, this prompted me to take out my dip net and look for nymphs in the water.

Here's a picture of one I found:

Variegated Meadowhawk, Sympetrum corruptum, nymph
Found May 5, 2012

While I was dipping for the dragonfly nymphs, I found a lot of other macro-invertebrates. The list isn't very long, yet, but includes immature mosquitoes, chironomid midges, mayflies, and predacious diving beetles!

Mayfly nymph found May 5, 2012

 Predacious diving beetle larva found in pond
May 4, 2012

I also found an adult predacious diving beetle
on
May 5, 2012






Thursday, May 10, 2012

Who's Visiting the Pond?

On the tails (mammal and bird tails that is) of last week's post, I thought I'd continue to focus your attention on our wonderful new pond. Sam Easterson has set up some of his trusty camera traps next to the waterfall to see who might be visiting the pond. Check out the following images to see what he has found so far.


Nighttime is busy at the pond!
 Stray cat...sorry, there aren't any fish in the pond yet
and no you can't eat them when there are!

Although these night time endeavors are interesting, I think the action during the light of day is even more so. Over the last few weeks, Sam's traps have captured over 50 images of birds hanging out by the pond.

American Crow, Corvus brachyrhynchos
That is one good bath!
Black-headed Grosbeak, Pheucticus melanocephalus,
 stops by for a moment.
 Western Gull, Larus occidentalis, going in for a drink.
Camera shy Swainson's Thrush, Catharus ustulatus.

Male Western Tanager, Piranga ludoviciana

For the grand finale, watch three bird species drinking from the pond at once! We've got a Mourning Dove, Zenaida macroura, on the far left, a Western Kingbird, Tyrannus verticalis, center frame, and a Warbling Vireo, Vireo gilvus, doing a fly-by.

video

 
Want to see more creatures caught on camera trap? No problem, check out lots more pictures and videos on our flickr pool.

Thursday, May 3, 2012

InSEX: Mating's Risqué Business in the Insect World

Last night I hosted an InSEX dinner at an undisclosed and secret location. No, we weren't eating insects (in fact, we had a lovely vegetarian meal). Instead, we were discussing their weird, wonderful, and various reproductive strategies!


Vietnamese Walking Stick, Baculum extradentatum
A great example of asexual reproduction


I also took some impressive beetles to show off

Here's an excerpt:

Sperm Wars-Unlike honeybees, dragonflies don't have exploding penises. Instead, they have an equally impressive mode of sperm competition. When a male dragonfly grabs a mateclasping her roughly behind the headhe carries her away for a nuptial flight. After some brief struggling, the male bends his abdomen around and inserts his aedeagus (that's insect for penis) into her reproductive tract. With his impressively spiked member he scoops out the sperm left over from a previous mating, thus ensuring it is his sperm and no other's that will fertilize the eggs she is about to lay...

But how does this all relate to the North Campus and L.A.'s urban nature? Simplewe found our first dragonfly at the pond! According to Museum Ornithologist, Kimball Garrett (yes, he does dragonfly identification too), this is a male Variegated Meadowhawk, Sympetrum corruptum. He was sunning himself on a rock, possibly waiting for a female dragonfly to make an appearance. Unfortunately for him, none showed up while I was there.

Over the next few months, the pond will attract more and more adult dragonflies and, soon enough, we'll have them mating. In tandem, the coupled dragonflies will approach the water's surface and the female will lay her eggs. Unbeknownst to many, the immature form of dragonflies actually live underwater! After the eggs hatch, the dragonfly nymphs will find a cozy spot to hide in the reeds. It's a dangerous and murky life down there, I mean who would want to get eaten by a fish? One way that dragonflies can evade predators is through jet propulsion. They pull water into their rectal chamber and eject it at high speed, thereby propelling themselves in a forward direction, and hopefully out of harm's way.

When they're not trying to evade their own predators, dragonfly nymphs are voracious predators themselves! They have extendable mouthparts that can be "shot" out of their heads in less than three one-hundredths of a second. This is very fast indeed, and allows the nymphs to sit and wait until something comes within mouth's reach. As you can tell, dragonflies are much more than just pretty insects good for putting on greeting cards and tattooing onto various bodyparts. I mean, what other creature can you think of that has jaws of death, rectal propulsion, and a highly modified penis for sperm removal?

Male Variegated Meadowhawk basking in the sun