Demography and Life History of a Manitoba, Delta Marsh Population of Franklin’s Ground Squirrels (Poliocitellus franklinii)

Posted on May 8, 2017

Author

Ellen M. PERO, and James F. HARE

CWBM 6 (1): 42–52.

Correspondence: E. M. Pero, 6624 Mountview Ct., Brighton, Michigan 48116, USA. 

Email: elmpero@gmail.com


Abstract

Concerns over population declines and disappearances persist for Franklin’s ground squirrels (Poliocitellus franklinii) throughout the American Midwest, yet little is known about even basic aspects of this species’ ecology. We live-trapped a free-living population of Franklin’s ground squirrels near Delta Marsh, Manitoba over the course of 4 years. We analyzed population demographics and life history traits, including adult density and sex ratio, adult survival, adult growth and fecundity, as well as juvenile mass, litter sex ratio and recruitment to the yearling age cohort. Seasonal patterns of mass change for maternal and non-maternal females and males in Delta Marsh population of this obligatorily hibernating species were similar across seasons and largely consistent with those reported among other Franklin’s ground squirrel populations. Adult females (≥1 year) outnumbered adult males by roughly 2:1, while litter sex ratio at juvenile emergence was consistently close to 1:1 in this population. Maternal females at our Delta Marsh site had a lower average litter size (6.31) than reported elsewhere for Franklin ground squirrels, and juvenile males weighed more than females at emergence. Survival varied between sexes and among years in the Delta Marsh population. Low survival between 2000 and 2001 followed detrimental agricultural practices and flooding, and subsequently led to a sharp population decline in 2001. The population eventually crashed in 2004 but rebounded by 2014. While population disappearances fuel concern over Franklin’s ground squirrel population status in the Midwest, apparent losses may reflect periodic fluctuations typical of this species’ demography, or population relocation rather than loss proper.

Key Words: Key Words: Demography, Franklin’s Ground Squirrels, Life History, Poliocitellus franklinii, Population Fluctuations

 

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