Beyond the enclosure: A decade of monitoring reveals altered traits in a European ground squirrel colony with implications for a recovery program

Effective integrated conservation programs critically depend on
high-quality animals from ex situ breeding, specifically those that are
genetically diverse and physically healthy, yet insufficient scientific
rigor in husbandry protocols can lead to unintended, detrimental
consequences that compromise reintroduction success. Drawing on over a
decade of long-term monitoring data for the European ground squirrel
(Spermophilus citellus), we compared a semi-captive, predator-free and
supplementary-fed colony with an adjacent free-ranging population to
assess the effects of enclosure management on key population traits such
as body mass and female reproduction. We found that the semi-captive
system, despite one of its goals of producing animals for release,
unintentionally altered traits in ways that could negatively impact its
long-term viability and condition of released animals, particularly in
terms of body mass and reproductive success While males tended toward
higher body mass (though not significantly), only non-lactating females
exhibited a statistically significant difference, with a mean increase
of  28.4% compared to free-ranging counterparts. Conversely,
juveniles born inside the enclosure were significantly lighter, suggesting
they might be outcompeted by adults for limited resources such as food and
space. Furthermore, a high proportion of non-lactating females inside the
enclosure suggests that either high density or surplus food resources may
negatively affect breeding success, though the distinct ecological impacts
of these factors require further investigation. Practitioners need to
implement science-based husbandry protocols and develop feeding strategies
that minimize adult-juvenile competition, emphasizing that these
recommendations are derived from empirical evidence presented in this
study. A rigorous, integrated approach including systematic long-term
monitoring must be adopted to mitigate unintended negative consequences,
thereby maximizing conservation outcomes and preventing resource waste,
with particular attention to adaptive management informed by ongoing
scientific evaluation.