Data from: Alternative reproductive tactics in female striped mice: heavier females are more likely to breed solitary than communally

1. Alternative reproductive tactics (ARTs) are discrete reproductive
phenotypes governed by decision rules called strategies. ARTs are fixed
for life in species with alternative strategies, while tactic expression
is plastic in species with a single strategy. ARTs have been investigated
in males of many species, but few studies have tested whether the same
theoretical framework applies in females. 2. Female striped mice
(Rhabdomys pumilio) employ three ARTs: communal breeders give birth in a
nest shared with female kin and a breeding male and show allo-parental
care; returners give birth away from the shared nest and later return to
it; and solitary breeders give birth away from the shared nest and do not
return to the group. 3. Here, studying free-living female striped mice
over six breeding seasons, we tested whether ARTs arise from alternative
strategies or a single strategy. 4. We also asked to what extent
stochastic extrinsic factors explain whether individuals become solitary
rather than group living. 5. Females switched tactics, consistent with a
single strategy, so we tested whether this represented a mixed or
conditional single strategy. Only the latter predicts differences between
ARTs in traits indicating competitive ability, such as body mass or age,
before individuals adopt a tactic. We weighed females at conception when
they were still group living to eliminate potential confounding effects of
gestation and subsequent social tactic (solitary versus group living) on
body mass. 6. Females that went on to use a solitary ART were heavier than
those that became communal breeders and returners, in support of a
conditional strategy. 7. Solitary breeders also arose through extrinsic
factors (mortality of all adult female group members). They weighed less
than females that became solitary while relatives were alive, but did not
differ in body mass from communal breeders and returners. 8. We conclude
that ART theory applies to both sexes, with female striped mice following
a conditional single strategy. Future studies should consider the
possibility that phenotypes that superficially resemble evolved tactics
might also arise through non-adaptive extrinsic causes.