Ground penetrating radar application to
resolve burrow complexity in modern Marmota monax burrows:
implication for the recognition of mammal burrows in the rock
record
Specific criteria permit the assignment of burrows in the rock
record to mammal or non-mammalian digging behavior. These criteria
revolve around mammalian burrow complexity that contrasts with
simple burrows of non-mammalian excavators, typically amphibians or
reptiles. Modern large burrow systems lack study because of the
extensive disruption of the land surface required to determine the
true extent of the system. Ground Penetrating Radar (GPR) provides a
non-invasive technique that has the potential to expand our
understanding of burrow systems. Surveys were conducted at 3
locations of known Marmota monax burrows using a SIR 3000 GPR system
from GSSI with 400 and 900 MHz antennas and upper reaches probed
with an endoscope.
The 400 MHz antenna was used to identify positions of possible
subsurface burrow features in clay-rich soils in surveys performed
with a line spacing of 25-50cm. Burrow positions were ground truthed
with an endoscope; abrupt turns in the burrow tunnels hampered
intrusion of the total burrow length. Burrows were further examined
with a 900 MHz antenna with a line spacing of 10 cm. The 900 MHz
traverses resolved the burrow position more accurately in 3D space
and revealed features which have been interpreted as additional
offshoots from the main tunnel. Both antennas resolved a flat,
dipping reflector suggestive of a ramp in the middle of the tunnel
and a possible terminal chamber of that burrow. The 900MHz antenna
constrained the tunnel width. Endoscopic examination showed tunnel
deflection around roots that was not resolved by GPR. The observed
burrow geometry is consistent with the criteria proposed to identify
mammal burrows in the rock record.
Ground penetrating radar application to
resolve burrow complexity in modern Marmota monax burrows:
implication for the recognition of mammal burrows in the rock
record