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. 2023 Feb 16;18(2):e0271083.
doi: 10.1371/journal.pone.0271083. eCollection 2023.

Using a substitute species to inform translocation of an endangered territorial mammal

Marina Morandini  1 , John L Koprowski  2
Affiliations

Using a substitute species to inform translocation of an endangered territorial mammal

Marina Morandini et al. PLoS One. .

Abstract

Substitute species can inform management strategies without exposing endangered species to unacceptable risk. Furthermore, experimental approaches may help to identify the causes of translocation failures, improving the chances of success. We used a surrogate subspecies, Tamiasciurus fremonti fremonti to test different translocation techniques to inform on potential management actions with regards to the endangered Mt. Graham red squirrel (Tamiasciurus fremonti grahamensis). Individuals of both subspecies defend year-round territories in similar mixed conifer forests at elevations between 2650-2750 m, where they store cones to survive over winter. We fitted VHF radio collars to 54 animals, and we monitored their survival and movements until individuals settled on a new territory. We considered the effect of season, translocation technique (soft or hard release), and body mass on survival, distance moved after release, and time to settlement of translocated animals. Survival probability averaged 0.48 after 60 days from the translocation event and was not affected by season or translocation technique. 54% of the mortality was caused by predation. Distance moved and number of days to settlement varied with season, where winter was characterized by shorter distances (average of 364 m in winter versus 1752 m in fall) and a smaller number of days (6 in winter versus 23 in fall). The data emphasized on the potential of substitute species to provide valuable information for possible outcomes of management strategies to closely related endangered species.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Number of red squirrels Tamiasciurus fremonti fremonti per different fate by sex and season (winter and fall), after translocation.
The different fate has been identified as dead, establish (settled in a new area, different from the original home range), missing (when the animals was not trackable by telemetry and not possible to locate again), home (animals able to homing after being translocated).
Fig 2
Fig 2. Survival curve of red squirrels Tamiasciurus fremonti fremonti after translocation, from the first day of release until 60 days after the release (usually corresponding also to the end of the field season).
On the x-axis is represented the time in days after translocation, while on the y-axis is represented the survival probability, starting as 1 the day of the animal release and decreasing until just below 0.5 after 40 days.
Fig 3
Fig 3. The variation in body mass of translocated red squirrels Tamiasciurus fremonti fremonti (N = 10), expressed as percentage of body mass change after translocation in respect to the weight at release.
In dark color the variation in body mass of non-translocated animals (N = 9), expressed as percentage of body mass change between two trapping sections in respect to the weight of the first trapping event (as a control group).
Fig 4
Fig 4. Plot of mean, sd, minimum and maximum distance of settlement site to release site (fall: mean 1752, sd 1472, maximum 5162, minimum 233).
Winter: mean 364, sd 421, maximum 1494, minimum 0 (one squirrel stayed at the release site), and number of days passed before squirrel (Tamiasciurus fremonti fremonti) settled (Fall: mean 23, sd 13.6, maximum 57, minimum 8. Winter: mean 6, sd 2.45, maximum 11, minimum 3).
See this image and copyright information in PMC

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