Rock Piles

http://www.wsdot.wa.gov/NR/rdonlyres/9093EB40-A81E-4094-BAA9-C376435A8D06/0/Mit_HabitatStructure.pdf

1. Intent: To mimic accumulations as might occur in rocky areas along streams,
outcrops, and talus fields. The rocks absorb daytime heat and slowly release it
during the cooler night.
2. Target species: The heated rocks provide a relatively stable thermal source and
will attract ectothermic reptiles for nesting and foraging. Rock piles with sufficient
mass may serve as reptile overwintering sites. Small mammals, particularly
rodents, will forage, nest, and receive some protection from predators in rock
piles. Rodents in turn may also serve as a food source for predatory species
such as weasels, mink, snakes, and coyotes.
3. Location: Rock piles should be placed in upland sites with little or no chance of
being inundated by water. If there are slopes in the site it may be beneficial to
bury half the pile into them, particularly south facing slopes.
4. Quantity: It is recommended to have at least five rock piles per acre.
5. Construction: Rocks should be cleaned and sized from two inch diameter to two
man rock (approximately two square feet) with some jagged edges. Jagged
edges are used by molting reptiles and provide secure footing for small
mammals. It is important to maintain a variety of interstitial spaces not exceeding
six inches. The piles should be at least five feet diameter and four feet tall.
Partially bury piles below the ground surface in upland areas. A perch log can be
added to expand habitat opportunities for birds. If large rocks are encountered
on site they may be grouped and partially buried to create burrows
(approximately one square foot or greater) for larger species such as coyotes.