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Friday, February 17, 2012

Otter latrines and zebra dung middens

River otter scat
(Muller Field Station, Richmond NY 2/12)
Today's post ain't pretty, but IMO it is interesting. The last time I was at our Muller Field Station, we visited an active river otter latrine. This is exactly what it sounds like: a place where river otters repeatedly defecate. They are sometimes called toilet sites or just toilets. I always make sure I tell my students that otters do not exclusively defecate at toilet sites, but they do so often and for a purpose. Think of the amount of information that can be conveyed in scat. Certainly one animal could tell what another individual was eating, but the vast majority of information is chemical (largely scent). And don't think of the scat itself as the main source of info, but rather the other products that are left behind probably tell the story better. Cells from the intestines mixed into the scat, hair left behind either through the process of ingestion or through the animal rubbing and rolling, scent from glands on the animals body (often anal glands that purposely deposit scent with the scat), etc. etc. What a waste to think of scat as just, well, waste!. At left is a photo of some river otter scat. There is a large quantity of undigested fish scales mixed in with a few aquatic inset parts. We resisted the temptation to pull it apart as our guests from Jamestown Community College were there to collect such items for later DNA extraction. This particular scat was part of a very active latrine site. The next photo shows the whole latrine. Notice the muck that has been pulled up from the channel. At least river otter and beaver do that and it is often hard for me to be 100% certain which species is responsivble. Even at this latrine site, I would not be suprised to find that a beaver had done this.
River otter latrine site
(Muller Field Station, Richmond NY, 2/12)
River otter latrines are particularly interesting for several reasons. As seen above, the scats often contain lots of interesting stuff that provide information regarding the diet of the animals. Second, the latrines make great places for camera traps and last, otters often leave behind another substance besides scat: jelly. In 2009, I volunteered for a week on a river otter research project in British Columbia. Our main task was to find fresh jelly (called otter or anal jelly in the literature) and collect it for analysis. The jely is actually produced by the otters so it is 100% otter DNA as opposed to the scat itself that has the DNA of the animal(s) that were consumed to help confuse the issue. As a general rule, otter jelly is preferred for DNA analysis for that reason. Here is one particularly interesting photo of fresh otter jelly from British Columbia:
River otter scat and jelly
(Victoria, BC 7/09)
Have a look at that string of jelly. I have always imagined that the otter was standing in one spot and gave a mighty squeeze rather than the otter moving as it emitted the jelly. Regardless, that is what fresh jelly looks like (although it can come in slightly different colors as well as in clumps rather than strings -- we even found depostis that looked as if the scat and jelly were combined that were dubbed jelly-scats).

On our family vacation to Africa this summer, we witnessed a different species of mammal deposting scat in piles. The very first Grevy's zebra we saw showed us an interesting behavior. He walked right up to a large pile of scat, sniffed and then added his own to the accumulation. This is a common behavior among zebra males as a way of marking their territories. The books (and our guide William) say that these are created along the boundaries of two males' territories. They are called "dung middens" rather than latrines...
JVN:"Hey! A Grevy's!"
DVN: "Is eating that poop?"
DVN:"DAD! Stop taking pictures. This is gross."
In truth, not everyone was as excited to see this behavior as I was...

1 comment:

  1. Is there a particular fish that the otters seem to prefer?
    Do the female zebras participate in marking territory, or is that left to the males?
    Also, is there any intraspecific competition between the zebras? There does not seem to be any secondary sexual characteristics, so is simply marking territory or chasing others out enough for them?

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