Location: N. California, Sutter County, Sutter Buttes, valley oak woodland
March 5, 2012 2:27 pm
What is the story behind this photo? Taken Feb 2012 in a small valley in the Sutter Buttes, Sutter County, Northern California. I was thinking solitary bee or trapdoor spider?
Signature: JD

Mud Ball Mystery

Dear JD,
While we are not certain what created this Mud Ball Mystery, we are relatively confident it is neither a Trapdoor Spider nor a Solitary Bee.  Could you tell us a bit more about the terrain?  Was this an area that floods in the spring?  It reminds us a bit of a Crayfish burrow.

Some Comments
I cannot imagine that this is a crayfish burrow.  As I remember both of the burrows we saw are in a veg area classified as California Prairie or Blue Oak in rather stony (about 30% up to fist sized cobble sub angular to angular) areas that I do not think flood in the spring.  Would you agree with me Michael and Zack?  Thanks for following up on this Jim.  Leslie

Definately not crayfish, I saw two more at about 1000 feet elevation the other day.

Hi Daniel,
I concur with comments below (Ed. Note:  comments above) that this is far too dry environment for a crayfish.  I will be in the field soon to get more photos with a ruler for scale, some capture tools.  What additional information is needed and how do I go about obtaining it – e.g. pour water into the hole to encourage the critter up to show itself?  I would rather not be too destructive in the investigation, so I am a bit reluctant to excavate the hole unless you think the animal will be OK to dig another.
Jim Dempsey
Environmental Scientist
California Department of Parks and Recreation, Northern Buttes District

Hi Jim,
We didn’t really think it was a crayfish, but that was a thought.  We do not believe it is a Bee or a Spider. 

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Location: California

10 Responses to Mud Ball Mystery

  1. Ken K says:

    Was it ever determined what caused these mud balls? My cousin has the same mysterious hole and mud balls in her California home.

  2. JSharma says:

    I see these same mud balls while hiking in damp places in Central Florida.

  3. Cyndi says:

    Maybe it is a type of mold? Funny how mold can look like a lot of different things.

  4. Jim Dempsey says:

    I concluded these mud balls were formed by a Calisoga spider excavating it’s hole. We observed this in action at the Sutter Buttes, Ça.

  5. Gustaf fredell says:

    It may be earth worm poo or mounds

  6. Gustaf fredell says:

    It may be earth worm poo or mounds

  7. Jim Dempsey says:

    Hi Gustaf – I am familiar with earthworm burrow mud mounds which are linear extrusions into ball-like mounds something like a ball or rather wad of string or from a dessert cake decorating tool; rather, these moist dirt piles consist of perfectly round balls that are carefully and consistently granular in texture – no, as I mentioned in April the definitive explanation in this case (California dry foothills) as we directly observed was a Calisoga (large spider related to trap door spiders) excavating it’s burrow, assembling little leg scoops of moist dirt onto a sticky ball of consistent maximum size held below thorax then rolling the dirt ball up and out of the burrow. I’m familiar with crayfish burrow mud mounds (personal observation in wetland locations of California and Valdivia, Chile), which I suppose could explain what JSharma above observed in damp places of central Florida (but I defer to someone more familiar with that area).

  8. larry Hiatt says:

    I have the same phenomena in my yard in Red Bluff,Ca Tehama co. the balls are approximately just slightly larger than 1/4 inch and quite spherical. They are around a hole in the ground that I presumed were large earth worm holes (about 1/2″ in diameter and not necessarily round in shape. There are several within a 30′ area.

  9. Brian says:

    I am a bit further north, but I have seen the same with spider burrows. I can’t say if it is a Tarantula or a Calisoga as they are skittish and back into their hole quickly. I can see their legs at night if I try. For scale, the ones in my yard have a hole roughly the size of a nickel to a quarter.

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