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22001199 SOUTHEASTERN NATURALIST 1V8o(2l.) :1289,7 N–3o0. 22
Movement and Fate of Translocated and In Situ
Southeastern Pocket Gophers
J.T. Pynne1,*, Jonathan M. Owens2, Steven B. Castleberry1, Nikole L. Castleberry3,
and Robert Brinkman4
Abstract - Geomys pinetis (Southeastern Pocket Gopher) is absent from much of its historic
distribution due to reductions in suitable habitat, which consists largely of open Pinus (pine)
systems. Restored open pine habitat represents an opportunity to reestablish Southeastern
Pocket Gophers into areas within their historic distribution through translocation. Using
radio telemetry, we documented evidence of avian predation on experimentally translocated
Southeastern Pocket Gophers and no predation on non-translocated individuals. Translocated
individuals exhibited greater movement rates, including aboveground movements,
likely exposing them to increased predation risk.
Introduction
Geomys pinetis Rafinesque (Southeastern Pocket Gopher) (hereafter, Pocket
Gopher) historically occurred in the Coastal Plain of Alabama, Georgia, and Florida
(Pembleton and Williams 1978). Although historically common in appropriate
habitat, the current distribution consists of small, scattered populations isolated
by habitat fragmentation (GDNR 2015). In response to declining populations, all
3 states in the range list the Pocket Gopher as a high-priority species in their state
wildlife action plans (GDNR 2015).
Pocket Gophers are largely associated with the Pinus palustris Mill. (Longleaf
Pine)–Aristida stricta Michx. (Wiregrass) ecosystem (Golley 1962), which has
been reduced to less than 3% of its previous extent (Landers et al. 1995). Recent focus
on restoring Longleaf Pine and other open pine communities of the southeastern
Coastal Plain (Van Lear et al. 2005) represents the opportunity to reestablish Pocket
Gopher populations. However, given the fragmentation of current populations and
limited dispersal abilities (Warren et al. 2017), natural recolonization into restored
habitat is unlikely. Translocation may represent a viable option for establishing
Pocket Gopher populations into restored pine habitat (Griffith et al. 1989). Herein,
we report observations on the movements and fate of translocated compared to nontranslocated
southeastern Pocket Gophers.
Methods
We conducted our study in the Sandhills ecoregion of the southeastern Coastal
Plain at Plant Vogtle in Burke County, GA. We identified 2 Pocket Gopher source
1D.B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA
30602. 2Durham, NC 27703. 3Georgia Museum of Natural History, University of Georgia,
Athens, GA 30602. 4Oglethorpe Power Corporation, Waynesboro, GA 30830. *Corresponding
author - jtp19715@uga.edu.
Manuscript Editor: Andrew Edelman
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populations and a translocation site with suitable habitat but no sign of an extant
population (Fig. 1). The translocation site was separated from both source sites by
≥5 km.
We trapped Pocket Gophers from 14 December 2010 to 25 January 2011 using
traps, as described by Connior and Risch (2009a) and Hart (1973). While gophers
were anesthetized under continuously inhaled sevoflurane, we surgically implanted
4-g VHS radio transmitters (Model V1/116, Sirtrack Tracking Solutions, New
Zealand) subcutaneously between the scapulae (Connior and Risch 2009b). We
performed capture, handling, and surgery under Georgia Department of Natural
Resources scientific collection permit number 29-WBH-10-191 and University of
Georgia Institutional Animal Care and Use Committee proposal number A2010 11-
582-Y1-A0.
Figure 1. Locations of Southeastern Pocket Gopher capture and relocation sites at Plant
Vogtle, Burke County, GA, 2010–2011. Inset map shows the historical species distribution.
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2019 Vol. 18, No. 2
We released 5 randomly selected radio-tagged Pocket Gophers at the translocation
site and released 4 back into their source burrow (hereafter, in situ). We
released translocated individuals into a 0.5-m diameter by 0.5-m deep hole provisioned
with carrots, potatoes, and turnips. We located all Pocket Gophers weekly
for up to 16 weeks post-release using a telemetry receiver (TRX-2000S, Wildlife
Materials Inc., Carbondale, IL) and a 3-element Yagi antenna, and recorded
individual locations using a hand-held GPS unit. We used ArcGIS 9.3 (ESRI,
Redlands, CA) to determine 3 movement metrics for each individual: initial
movement (distance from the release point to the first telemetry location taken ~1
week later), movement rate (mean distance between all recorded locations), and
farthest distance moved from release point. Sex determination in Pocket Gophers
based on external morphology is unreliable (Baker et al. 2003); thus, we did not
consider sexes separately.
Results
We were able to locate the telemetry signal of all 5 translocated individuals
upon our initial location attempt except for 1 individual, for which we did not
observe any evidence of mounding activity. We were unable to detect the telemetry
signal of 1 translocated individual after the initial location, but we continued
to observe mounding activity, suggesting transmitter failure. We did not attempt
to re-trap any individual due logistical constraints and the difficulty of trapping
Pocket Gophers (Connior and Risch 2009a). For the remaining 3 translocated
individuals, we documented evidence of 2 predation events 7 d and 17 d postrelease.
We recovered the carcass of 1 individual and observed that the surgical
incision had been reopened and muscle had been picked from bone suggesting
avian predation. Although unlikely, it is possible the individual died aboveground
and was consumed post mortem. We found only the transmitter from the other
individual at the base of a large tree. We successfully located the 5th translocated
individual several times; it continued mounding activity after an above-ground
dispersal movement. This individual was still alive at the end of the tracking
period (16 weeks). We documented no evidence of predation on in situ Pocket
Gophers, but excavated a transmitter that was apparently extruded from the surgery
site from 1 individual. We do not know the fate of this individual, but we
documented no mounding activity following transmitter recovery, suggesting
that it died from transmitter-related complications. We were unable to detect the
signal from another in situ Pocket Gopher after 9 weeks, but observed continued
mounding activity, suggesting transmitter failure. Our movement analyses were
based on Pocket Gophers with ≥5 locations (mean = 9.3, range = 5–15; n = 3
translocated, n = 4 in situ). Mean initial movement distance (translocated = 78.6
± 34.3 m [mean ± SE], in situ = 23.2 ± 5.6 m), movement rate (translocated = 4.8
± 3.3 m, in situ = 1.9 ± 0.9 m), and farthest distance moved (translocated = 98.4
± 24.6 m, in situ = 44.5 ± 15.2 m) were all greater for translocated compared to in
situ Pocket Gophers.
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Discussion
Although Pituophis spp. (pine snakes) are thought to be the primary predators
of Pocket Gophers (Miller et al. 2012, Rudolph et al. 2002), other studies suggest
that avian predation may also be common. Warren et al. (2017) documented Pocket
Gopher mortality suggestive of avian predation. Several species of owls have been
documented preying on Thomomys talpoides Richardson (Northern Pocket Gopher)
(James and Barss 1985, Tyron 1943). Given their poor above-ground locomotory
abilities, it is unlikely that the individual we failed to locate after translocation
moved beyond detection. We surmise that either this individual was also predated
and carried beyond transmitter range or the transmitter failed, though we never
documented mounding by this individual.
We observed no predation on in situ Pocket Gophers. Difference in predation
rates observed may be due to increased movements exhibited by translocated individuals,
exposing them to greater risk (Brown 1971, Van Vuren et al. 1997). Two
translocated individuals made initial movements of 147 m and 57 m, respectively,
which were the farthest movements recorded for those individuals. We suspect
that initial movements of all translocated individuals were above ground, as all
made movements >39 m and there was no mounding activity between the release
site and the initial location. In contrast, initial movements of in situ gophers were
smaller and likely underground in the existing burrow system. Other studies have
indicated that translocated and in situ Pocket Gophers make aboveground dispersal
movements (Connior and Risch 2010, Warren 2014). Another fossorial mammal,
Otospermophilus beecheyi (Richardson) (California Ground Squirrel), makes extensive
movements and lacks release-site fidelity after translocation (Van Vuren et
al. 1997). Warren et al. (2017) documented only 2 predation events out of 17 radiotracked
in situ Pocket Gophers. Although not quantified in this study, direction of
initial movements in translocated individuals were not suggestive of homing. Homing
attempts can lower translocation success (Van Vuren et al. 1997), but homing in
Pocket Gophers is uncommon (Hansler et al. 2017, Warren 2014).
Although based on a small sample size, our results suggest that predation due
to increased aboveground movements of translocated Pocket Gophers may limit
translocation success. If translocations are used to relocate agricultural nuisance
individuals or repopulate extirpated areas, soft-release measures could reduce
aboveground movements and lower predation risk (Van Vuren et al. 1997). Softrelease
techniques may include construction of an extensive starter burrow prior
to release, a wire cage or wooden coverboard placed over the starter hole, and
fencing placed around the initial release area (Hansler et al. 2017). However, these
measures are likely temporary because Pocket Gophers would eventually burrow
below containment measures. Furthermore, Pocket Gophers would disperse below
ground for foraging opportunities. Seasonal timing of translocation also may affect
initial movements, and ultimately, translocation success (Bright and Morris 1994),
but additional research is needed to determine optimal timing.
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Acknowledgments
We thank Sonia Hernandez and Shaun Boone for implanting transmitters. John Jensen,
Lara Mengak, Mike Murphy, Mike Odom and Sharon Swagger assisted with trapping and
radiotelemetry. Mike Conner provided an early manuscript review.
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