Disappearance and Mortality Causes in Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus) Juveniles

Juvenile survival curves in a solitary ground squirrel with a prolonged hibernation: effects of individual characteristics, environment, and maternal investment

“…The dramatic decline in juvenile numbers between the natal emergence and immergence into hibernation ( Figure 1 ) is similar to other solitary ground squirrel species with long hibernation: Only 17% of young survived their first summer, which is less but comparable to S. citellus : 32% ( Hoffmann et al 2004 ), I. tridecemlineatus : 32%, ( Freeman and Bachman 2016 ), in contrast to more social species such as Urocitellus parryii (about 40–75%— Byrom and Krebs 1999 ; about 80%— Wilbur et al 2022 ), U. columbianus (not less than 45–70%— Bennett 1999 ; Neuhaus et al 2004 ), prairie dogs or marmots, where young survival is high as well ( Van Vuren and Armitage 1994 ; Farand et al 2002 ; Farid et al 2022 ). Thus, sociality appears to be beneficial for early juvenile survival in ground squirrels, which conforms to the previous findings on its positive effect on the annual survival of the young ( Bhumstein and Armitage 1998 ).…”

“…After the onset of dispersal, the mortality rate decreased and was minimal at the 28–48 days after emergence ( Figures 1 and S3 ). This pattern does not correspond to data from other ground squirrel species: For example, in Arctic ground squirrels U. parryii , dramatic loss of the juveniles was observed after the 20th day after emergence ( Byrom and Krebs 1999 ); in 13-lined ground squirrels, a weekly loss of juveniles peaked about 3–4 weeks after emergence ( Ictidomys tridecemlineatus ; Freeman and Bachman 2016 ); in European ground squirrel Spermophilus citellus , most juveniles died during 4–7 decades after emergence ( Hoffmann et al 2004 ). In these and some other ground squirrel species, young females survived better than males ( Michener, 1989 ), which is often attributed to male-biased dispersal and male risky behavior.…”