peaks and 30 days following (n = 20) weighed 9346109 g. Those cubs born 30–60 days after the ungulate birth peak (n = 31) weighed 1,1746100 g, whereas cubs born .60 days after the ungulate birth peak (n = 13) weighed 11726102 g. Cub survival No difference was documented in sex-specific survival (Male, n = 42, S(i) = 0.55, SE = 0.08; Female, n = 36, S(i) = 0.58, SE = 0.08; 2-sample t76 = 0.264, 2-sided P.0.50); therefore, we pooled sexes in subsequent analyses. We found no support (evidenced by overlap in confidence intervals) for our hypothesis that survival was greater for cubs born within the birth pulse (n = 47, S(i) = 0.55, 95% C.I. = 0.41–0.69) compared to those born outside the pulse (n = 31, S(i) = 0.58, 95% C.I. = 0.41–0.74). However, we found an increasing trend in survival relative to prey abundance and vulnerability (Fig. 2). Cubs born before the ungulate birth period or ,30 days afterward (April–June, n = 30, S(i) = 0.50, SE = 0.09) had mean survival rates lower than those born 30–60 days after the ungulate birth peak, but before winter (Jul–Sep, n = 32, S(i) = 0.53, SE = 0.09; Oct–Nov, n = 12, S(i) = 0.67, SE = 0.14). Dispersal age We obtained dispersal ages for 22 juvenile mountain lions (14M, 8F). Male mountain lions dispersed at a mean age of 14.7 months60.84 (SE) and females dispersed at 15.361.15 months. While accounting for variation in timing of birth, we found no sex- related differences in natal dispersal age (F1,20 = 1.420, 2-sided P = 0.50). There was evidence that cubs born during the birth pulse dispersed when 2.5 months younger (61.3 SE) than those born outside the pulse (Extra sums-of-squares F1, 17 = 3.92, 2-sided Birth Timing for Mountain Lions P = 0.120). However, there was stronger evidence (Extra sums-of- squares F1, 15 = 8.971, 2-sided P = 0.018) that cubs born during spring, early-, and mid-pulse (1 April–30 July, n = 9) dispersed 461.3 months younger than cubs born in the last month of the birth pulse and winter (1 August–31 January, n = 13). When we excluded cubs born in July (i.e., middle month of pulse), there was strong evidence of a mean 461.5 month difference in dispersal ages (Extra sums-of-squares F1, 15 = 7.405, 2-sided P = 0.032). All cubs that were born in early or mid-pulse dispersed during the summer (June–August) or autumn (September–November) after attaining an age of 1-year. All cubs born late in the birth pulse dispersed during winter (December–February) or spring (March–May) after becoming 1-year of age. Mother and first litters We documented 31 litters that were born to females that we had recorded evidence of previous nursing [25]. Birth timing period was narrower for females that had not previously nursed cubs (n = 11) and occurred mostly in July (n = 6), and few occurred in June or August (n = 3, Fig. 3). Birth timing for females that had previous litters (n = 20) were dispersed throughout the year, while still exhibiting a pulse in June–August (Fig. 3). Discussion Logan and Sweanor [1] hypothesized that cub survival might be higher for cubs born within the birth pulse, than those born outside the pulse, because the pulse in their central New Mexico study area generally coincided with ungulate birthing periods. Laundre´ and Herna´ndez [4] summarized available data on birth Figure 2. Mountain lion (Puma concolor) cub survival in relation to neonate ungulate presence and age in the Black Hills, South Dakota, USA. doi:10.1371/journal.pone.0044625.g002 PLOS ONE | www.plosone.org 3 September 2012 | Volume 7 | Issue 9 | e44625