determine if depressed peripheral counts are caused by a block in the synthesis of certain cells or a reduction in the number of circulating cells. We do not have an explanation for the reduced number of residents tn the High Activity Stratum. Beatley (1976) reported that 2D, merriami replaced D, microps Table 4. as a dominant rodent in some disturbed areas of NTS. Whereas the low number of D, microps may be explained by habitat alteration around GZ, it does not explain the absence of resident A. leucurus or O. torridus. Whereas a reduced number of some species of rodents may be expected when native habitat is altered, experience by the investigators in the Mohave desert suggests that many rodents, particularly A. leucurus, are likely to be more numerous in disturbed habitats with sufficient vegetation cover. We do not believe, therefore, that the depauperate rodent fauna of Area 11-C, GZ, can be explained satisfactorily strictly on the basis of mechanical disturbance, as the area is not denuded of vegetation. We are not suggesting at this time that this phenomenon is related directly to Pu or Am levels; however, it is a hypothesis worthy of further investigation. onMnn ula 81S A : OO TF lM Bla o — 5 gd ae Hid vg a o ale Where a Mio & 44 ° na eo a . Aan et MON . en ~t oni]r mM oe . . . a . n a wo . ~ woWMWNoOonwerttim é a A aA wo N ra he U1] > B|S tr a 25 u om aH au 20 5 Ww o a Se a o -e*a oO % AS Aya vw EIS BIg ~ On A Oo ca owolor eo S -& aju Ele & u aA 21g 8 x wao N Tonto aN a i N MH = e ae qa ° osal}n or ta Vim Dl v g a z|2 48 oH OF mwo a 8 a ah yw zw ON o a ojar als al 6 ° = & 3 Ss 3Q ~ o | E 7-_ 2o a to 4 A wy 5 a & w & age & & a ‘a Oy a: ‘28 A FE oS on . oO 9 | 869 Qo Ege + S ® S&S FE & > 8 a8 § 5, aU 3 au a 9 & 8 8 8 = z o #8 oov Ww oa ~ a fo bw ov yw FF mo 9 § So =< E gq 4 w a © 8 ow 8 GS aR 5 § es E Sane Sa 399 398 8 2 ALO Wa sc 6 A 4 8 BZ a 9 oa a *Represents 23.5% of trapping grid (>25,000 CPM 24] Am). Table 4 presents data on total number of captures and number of resident rodents encountered in the High and Low activity strata of the inner grid during eighteen months of study in Area 11-C. If we assume random distribution of animals in the grid, an assumption which is probably met only under ideal conditions, an estimate of the number of animals captured in the High Activity Stratum can be made by multiplying the total number of captures (447) by the proportion of the area encompassed by the High Activity Stratum (23.5%). One hundred and five captures are expected using these calculations which are not Significantly different than the number actually captured in this stratum (£03). Ail species shown in Table 4 were captured in both High and Low Activity Strata. The number of resident animals expected in the High Activity Stratum can be estimated in the same manner. There were eighty-two resident animals in the grid of which nineteen were expected from the High Activity Stratum. Only nine resident animals, however, were recorded from this stratum, a signi-" ficantly (P<.01) lower number than expected. Of the six resident species, only four were found in the High Activity Stratum. In addition, of these resident animals, only one species, D. merriami, was represented by more than two individuals. These data shédw a reduced species richness, species diversity (H') and population density of resident rodents in the High Activity Stratum near GZ and illustrate the problems of collecting adequate samples of most species of rodents. ® Chi squared. eaSignificantiy different than expected (P<.01); One particularly difficult problem in evaluating tissue burdens of small vertebrates occupying different trophic levels and inhabiting defined activity strata is the apparent reduced resident rodent populations in the vicinity of GZ. 4 of Area 11-C, NTS (Moor et al., 1976). RESIDENT RODENT POPULATIONS OF AREA 11-C in Relation to Activity Strata A Comparison of Trapping Success and Residency of Rodents ° B |B