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. . 6. We assumed that any adjacent or nearby patches would be considered adjacent only if a) they are in the same valley floor reach, i.e., a patch closer than one mile away, but in a different drainage (valley floor reach) was not considered in the same valley floor reach, or b) the linear distance to the patch along a ditch course was one mile or less. In other words the linkage has to be along a watercourse and not across "watersheds". We assumed that if there is less than or equal to I mile between occupied patches and >/= 0.25 ac. then the habitat patch was potentially occupied. [The reasoning here is that the proximity to other nearby patches within the reach of nightly movement may compensate for the inadequate resources of a distant patch < 0.25 ac.] This is a very simplified model that in reality occurs in a complex landscape. For example, if a habitat patch occurs in a "string of pearls down a system" they are likely to decrease in biological significance (for the mouse) with increasing distance from a large source of habitat. However, we are assuming that all suitable patches are equally significant. The perpendicular distance of activity from a ditch is considered to be 300 ft on each side of the ditch. 7. 8. 9. II. ISSUE 2 Maximum Allowable Disturbance Area in Continuous or Contiguous Habitat . The USFWS also asked the Science Team to evaluate the maximum allowable disturbance area in occupied habitat, that if altered, even temporarily, could be considered of no significance. This issue arises as persons maintaining or using ditches need to gain access or manipulate the PMlM habitat in order to deliver water or maintain/repair infrastructure. The potential activities include cleaning, mowing, weeding, burning, and repairing headgates (among others). In this case the assumption is that the vegetation is occupied. Therefore, the issue centers around how much shrub habitat could be removed/altered without having an impact on the individual resident PMlM? Or what is the probability that a given activity will directly or indirectly impact a mouse. Diagnosis . Theory: Theory to guide the analysis of this issue is sparse. However, a minimum home range was again agreed upon as a baseline. It follows that we are seeking theory that will suggest how much of a minimum home range could be removed without impairing the resident individual's ability to reproduce successfully. For an animal to be able to survive long enough to reproduce necessitates there being adequate resources available to support the individual. The Science Team agreed that there was little applicable theory other than that 5