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Native Californian, biologist, wildlife conservation consultant, retired Smithsonian scientist, father of two daughters, grandfather of 4 small primates. INTJ. Believes nature is infinitely more interesting than shopping malls. Born 100 years too late.

Wednesday, September 12, 2007

Hairy entanglements

Bwah-ha-ha-ha . . . I tricked you with that title, didn't I!

And then you saw another blasted skunk picture. Well, I know you're tired of seeing skunks on this blog, and I'd much rather be writing about pictures of California quail, red tree mice, or kit foxes. But these seedy skunks delivered a story.

Skunks tank up at the water trough nightly, so the camera trap gives me a pretty good idea of who's coming and going. Seedy skunks started to show up back in July. A week later they were gone, and only well-groomed skunks were making appearances.

I can't tell you what kind of seeds they were, but the skunks, I suspect, dispersed the seeds far and wide as they grubbed about on their nocturnal beat. I imagine a lot of the seeds just dropped off, but carnivores are pretty persistent at grooming seeds out of their fur, too.

Epizoochory is an old story. Grass parts were recently discovered in dinosaur dung, so Juarrasic park might have been seeded by giant reptiles, but that's endozoochory.

We're talking about the first plants to hitch-hike "on" rather than "inside of" mammals (epizoochory). The earliest evidence for seed dispersal by hairy entanglement comes from the Dominican Republic in the late Eocene. A grass spikelet attached itself to some mammalian hair, a blob of tree pitch snared the entanglement, and the pitch was transformed to amber. The spikelet had hooked hairs on the lemma, which means that hairy entanglement had been going on for some time.

When the middle Miocene (c.20-10Ma) rolled around, prairies and savannas were widespread, and it is likely that mammals, especially migratory ungulates contributed to their spread. In seasonal climates sheep, bison, antelope, camels, and horses cover large distances moving between summer and winter ranges, and bushy manes and hair capes can carry a lot of seed. In domestic sheep the area between the shoulders is particularly prone to collect seeds and plant rubbish, and sheep growers refer to it as the "bird's nest".

You have to marvel at the myriad and frustrating ways that plant seeds stick to your sneakers and bury themselves in your socks. It's not just a chance thing.

So when my daughters had to do a science fair project in middle school, I suggested "Furs and burrs"! Our working hypothesis was that mammalian fur differs in its ability to catch burrs. The experimental design was simple. After school, the girls suited up with fur leggings of cottontail, woodchuck and deer skin (patches held on with rubber bands), and then traipsed through a measured track of weeds in the field next to the house. Afterwards, they combed the furs, and sorted the seeds for counting.

I just called them on the telephone to learn the results, and guess what? They didn't remember! They said it was great fun wearing the leggings and combing the furs, but they couldn't remember the results! Oh well, it was a fun if not elegant experiment.

I was pleased to find that just a few years ago some researchers did the experiment more scientifically. They tested seeds of 66 species on seven mammals to develop a "seed adhesivity score", but before I go any farther, let me state that I had to be satisfied with the limited information contained in the abstract of their publication -- the codger wasn't willing to pay $30 for a pdf file of the article.

As reported in the abstract: "Deep furs with long, rough, undulated hairs implanted at a large angle were most suited for seed adhesion, while seeds adhered less well to shallow furs with short, smooth, straight hairs implanted at small angles." Clearly we are talking about all kinds of bushy tails, and skunk tails fit the billing to a T.

The authors go on to say, however, that there was "an interaction effect between certain seed and fur types", which I take to mean that some furs and seeds were meant for each other. They also learned that though seed structure is a good predictor of hairy entanglement, less specialized seed types can still get a good grip on fur. In other words, all the species they tested seem able to disperse as hairy entanglements.

As frustrating as seeds may be in boots, pants, and mittens, they offered society a wonderful invention. It didn't take George de Mestral much time to figure out the hook and fastener principle that plants evolved millenia ago. That's how we got Velcro.


Couvreur M, B. Vandenberghe, K. Verheyen, and M. Hermy. 2004. An experimental assessment of seed adhesivity on animal furs. Seed Science Research, 14(2):147-159.

Manzano, P. and J.E. Malo. 2006. Extreme long-distance seed dispersal via sheep. Frontiers in Ecology and the Environment, 4(5):244–248.

Milton, S.J., W.R. Siegfried, and W.R.J.Dean. 1990. The distribution of epizoocoric plant species: a clue to the prehistoric use of arid karoo rangelands by large herbivores. Journal of Biogeography, 17(1)25-34.

Poinar Jr, G. O. and J. T. Columbus. 1992. Adhesive grass spikelet with mammalian hair in Dominican amber: First fossil evidence of epizoochory. Journal of Cellular and Molecular Life Sciences, 48(9):906-908.



Owlman said...

Another great blog Chris.
I feel like I've been taking a biology class again and I can't wait to get to class. I'm hooked and now looking for a camera and need your advice. Are the "Trail" cameras worth the money?

Anonymous said...

They are a bit expensive, but I'd recommend the Cuddeback Excite or, if your budget can handle it, the Cuddeback Expert (it can be set to take video in addition to still images and my conservancy group has caught some great videos of a big cinnamon-colored black bear scratching his back and of a cub scurrying up a tree in southwestern Arkansas' Ouachita Mountains).
If you are going to be using them in bear country I think it is worthwhile to invest in the bear box, as we've gotten many images of bears mouthing the cameras, but our group uses both and we've been very pleased with the quality of the cuddeback's images.

Anonymous said...

How does the Cuddeback do on closer range objects? Are the animals still in focus? Do they wash out with the flash? The materials I read about the camera seem to be mostly about deer. That may be because the market is deer hunters, but are the cameras in fact mostly just designed for deer?

Thanks for any advice.

Camera Trap Codger said...

I've heard that the Cuddebacks are fast, and a few years ago I used an early Cuddeback -- it was a 1 or 2 MP model. I haven't reviewed the commercial scouting cameras lately, so am not up to date on others. But an important consideration is resolution. I'd say a 3 MP cam will give you some pretty nice pictures. Frogman seems to be up on them. As for price, the higher MP cams are a little pricey, and it costs about $250 to make your own using an Sony s600 bought on EBay.

Owlman said...

Thanks for all your help.
I will look into the Cuddleback and compare it with a few others. How difficult is it to make your own when you are not a computer nerd?

Camera Trap Codger said...

You buy the parts, Terry, and I'll help you put it together. Reno Taini wants to make his own too. He'll be coming up in the fall when we'll have a "workshop" in the garage.

Jayla said...

You got me curious which fur collected the most burrs. I looked in my file of science fair reports, but didn't find it. (I did get a perfect score on my Homing in White-Footed Mice project, though.) I have a feeling it was the groundhog fur that collected the most burrs, which seems to be consistent with what you mentioned in your blog, since deer and rabbit fur is smoother and shorter than groundhog fur.

Owlman said...

Hey Chris now I might just take you up on that offer and would even drive down to your place.
It would be great to see you and Reno but I doubt that either one of remember me. Maybe I could talk Rich into coming over and it would be a small reunion. I'll also bring the wine.

Camera Trap Codger said...

We remember you well, Terry (and the biology department stockroom, of course). Let's do it. Early November would be good for us. I'll check with Reno, he was in Africa last I heard. Then I'll be back in touch. Send an e-mail to Chindwin@sbcglobal.net.