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

Brett DeGregorio,Hannah Myers,Raymond Moody

doi:10.3390/ani10081358

Abstract

Simple SummaryWildlife are moved (translocated) for numerous reasons, whether it is to establish a new population for conservation purposes or to move animals out of harm’s way. Unfortunately, animals that are moved often fail to survive in their new homes. Soft release is a technique of penning animals at the release site before letting them free, which allows them to become acclimated to their new surroundings and prevents them from immediately trying to return to their capture location. We soft-released Texas horned lizards at an urban military installation in Oklahoma, United States. While soft-released adults did have reduced post-release movements, they also had low survival, suggesting that they do not respond well to translocation. However, post-release survival of juveniles was high and equivalent to resident juveniles. Translocation efforts of Texas horned lizards may be most successful if they focus on relocation of juveniles rather than adults.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.

Highlights

As wildlife populations decline and their habitat is encroached upon by humans, land managers are adopting techniques like wildlife translocation to maintain or augment viable populations [1].Translocation is the intentional release of captive-propagated or wild-caught animals into the wild for the purpose of establishing a new population, augmenting a critically small population, or managing animals that are in harm’s way [2,3]
Our results suggest that translocation has mixed utility for Texas horned lizard conservation
Soft release is a promising technique for improving the success of wildlife translocation programs; further empirical research is needed

Summary

Introduction

As wildlife populations decline and their habitat is encroached upon by humans, land managers are adopting techniques like wildlife translocation to maintain or augment viable populations [1]. Translocation is the intentional release of captive-propagated or wild-caught animals into the wild for the purpose of establishing a new population, augmenting a critically small population, or managing animals that are in harm’s way [2,3]. Despite substantial investments of time, energy, and resources, these endeavors often fail to establish wild populations (33–52% failure rate [1]), yet the practice is becoming more common on private, state, and federal lands [3,4]. If animals were translocated short distances, their likelihood of returning to their point of capture (i.e., homing) can be quite high [11], which may return them to harm’s way

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