Reproductive and resource benefits to large female body size in a mammal with female-biased sexual size dimorphism
H.
Bobby Fokidis1, Thomas S. Risch1, and Travis C.
Glenn2
1Department of Biological Sciences, Arkansas State University,
State University, AR 72467, USA
2Savannah River Ecology Laboratory, The University of Georgia,
Aiken, SC 29802, USA
Abstract
Factors
underlying the evolution of female-biased sexual size dimorphism in mammals
are poorly understood.
In an effort to better understand these factors we tested whether larger
female southern flying squirrels,
Glaucomys volans, gained reproductive advantages (larger litters
or more male mates) and direct resource benefits, such as larger home
ranges or access to more food (i.e. mast-producing trees). As dimorphism
can vary with age in precocial breeding species, we compared females during
their first reproduction and during a subsequent breeding attempt. Females
were not significantly larger or heavier than males at first reproduction,
but became about 7% heavier and 22% larger than males at subsequent breeding.
Larger females produced larger litters and had home ranges containing
a greater proportion of upland hardwood
trees. Female body size was not associated with either multiple male mating
or home range size, but females with larger home ranges had higher indexes
of body condition. Females in precocial breeding flying
squirrels initiate reproduction before sexual size dimorphism is evident,
and thus, may be allocating resources to both reproduction and growth
simultaneously, or delaying growth entirely. Larger females produce more
pups and have access to more food resources. Thus, selection for increased
female size may
partly explain how female-biased sexual size dimorphism is maintained
in this species.
Keywords
benefits of age, body condition and body size; female-biased sexual size
dimorphism; Glaucomys volans;
multiple paternity; precocial breeding; home range size; southern flying
squirrel
SREL Reprint #3037
Fokidis, H.
B., T. S. Risch, and T. C. Glenn 2007. Reproductive and resource benefits
to large female body size in a mammal with female-biased sexual size dimorphism.
Animal Behavior 73:479-488.
