Correlates of reproductive success in a population of nine-banded armadillos

We used microsatellite DNA markers to identify the putative parents of 69 l itters of nine-banded armadillos (Dasypus novemcinctus) over 4 years. Male and female parents did not differ in any measure of body size in comparison s with nonparents. However, males observed paired with a female were signif icantly larger than unpaired males, although paired females were the same s ize as unpaired females. Females categorized as possibly lactating were sig nificantly larger than females that were either definitely lactating or def initely not lactating. There was no evidence of assortative mating: body-si ze measurements of mothers were not significantly correlated with those of fathers. Nine-banded armadillos give birth to litters of genetically identi cal quadruplets. Mothers (but not fathers) of female litters were significa ntly larger than mothers of male litters, and maternal (but not paternal) b ody size was positively correlated with the number of surviving young withi n years, but not cumulatively. There were no differences in dates of birth between male and female litters, nor were there any significant relationshi ps between birth date and maternal body size. Body size of either parent wa s not correlated with the body sizes of their offspring. Cumulative and yea rly reproductive success did not differ between reproductively successful m ales and females. Average reproductive success (which included apparently u nsuccessful individuals) also did not differ between males and females. The majority of adults in the population apparently failed to produce any surv iving offspring, and even those that did usually did so in only 1 of the 4 years. This low reproductive success is unexpected, given the rapid and suc cessful range extension of this species throughout the southeastern United States in this century.