Soft Release Translocation of Texas Horned Lizards (Phrynosoma cornutum) on an Urban Military Installation in Oklahoma, United States

Abstract

Wildlife translocation is an often-used technique to augment populations or remove animals from harm’s way. Unfortunately, many translocation efforts fail to meet their goals for myriad reasons, particularly because translocated animals make large, erratic movements after release, which can result in high mortality rates. Soft release, holding animals in acclimation pens for some period of time at the recipient site before release, has been proposed as a technique to reduce these large movements and increase the survival of translocated animals. Here, we compared the survival and movement patterns of soft-released Texas horned lizards (Phrynosoma cornutum) with resident lizards, as well as hard-released lizards from a prior study. Juvenile lizards that were soft-released had high survival rates similar to resident lizards, despite still moving more frequently and occupying larger home ranges than residents. Conversely, soft-released adult lizards had survival rates similar to those that were hard-released, and much lower rates than resident adults. Curiously, soft-released adults did not have significantly higher movement rates or home range sizes than residents. Our results suggest that caution should be used before adult Texas horned lizards are translocated. However, juveniles responded well to soft release, and future research should explore whether they are more resilient to translocation in general, or if soft release provided a specific survival advantage. Contrary to our predictions, the survival of translocated animals was not related to their post-release movement patterns, and the mechanism underlying the observed survival patterns is unclear.

Survivorship and Spatial Patterns of an Urban Population of Texas Horned Lizards

“…One notable exception is that our 2019 estimate was 72% higher than the estimate made by Wolf et al (2013) of 32.9 ± 4.7 lizards in 2011. Construction of a housing development adjacent to WR3 in 2008development adjacent to WR3 in -2011 resulted in a loss of 7.4 ha of lizard habitat, and 17 adult horned lizards were translocated in 2008 from the housing site to another, noncontiguous prairie at TAFB approximately 1.6 km away (Wolf et al 2013, DeGregorio et al 2020). The construction site and WR3 were separated by an existing gravel road; thus, WR3 itself remained constant in area with only the northern boundary area affected directly by land disturbance.…”

Demographic evidence that development is not compatible with sustainability in semi‐urban freshwater turtles

“…Additionally, we searched for dead turtles by driving and walking along the primary roads daily, and other roads surrounding the study area 3–4× per week. We considered the recovery rate of tagged road‐killed turtles as a crude carcass detection rate because turtle carcass recovery from road surveys likely underestimates the true number of road mortalities as injured animals may move off the road before they die or road‐killed turtles may be removed by scavengers or residents (DeGregorio, Moody, & Myers, 2020).…”

Evaluating mitigation translocations for better biodiversity outcomes

“…Recent studies (in New Zealand and globally) continue to experiment with techniques to improve biodiversity outcomes of mitigation translocations (for herpetofauna, particularly). These include, habitat enhancement at receptor sites (Fitzgerald et al, 2015;Nafus et al, 2017;Harper et al, 2018;Lennon, 2019), conducting 'soft -releases' (DeGregorio et al, 2020;Flynn-Plummer & Monks, 2021), evaluating post-release dispersal (Knox & Monks, 2014;Angeli et al, 2018;Nash & Griffiths, 2018), continuing to evaluate determinants of success (Miller et al, 2014;Bradley et al, 2020) and publishing results (even of failed translocations, such as Nash et al, 2020).…”