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Title:Thinking outside the box: Effects of environmental enrichment and rearing duration on head-starting success of box turtles
Author(s):Tetzlaff, Sasha James
Director of Research:Sperry, Jinelle H.
Doctoral Committee Chair(s):Schooley, Robert L.
Doctoral Committee Member(s):DeGregorio, Brett A.; Ward, Michael P.; Kingsbury, Bruce A.
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):conservation, reintroduction, reptile, translocation, wildlife management
Abstract:Translocation is the deliberate movement and release of animals and a common management technique in wildlife conservation programs. However, efforts are often unsuccessful because relocated animals have low survival, precluding population establishment. I reviewed studies using antipredator training, environmental enrichment, and soft release as pre- release behavioral conditioning in translocation programs, and I quantitatively synthesized how these approaches affect post-release success. I then conducted experiments using captive-reared juvenile eastern box turtles (Terrapene carolina) raised with or without naturalistic environmental enrichment to better understand mechanisms influencing habitat preferences in captivity. Next, I investigated if enrichment encouraged natural behaviors before turtles were released into the wild and how being raised in enriched environments affected growth over differing rearing periods (nine vs. 21 months). Finally, I examined how enrichment and captive- rearing duration affected the turtles’ post-release growth, behavior, and survival. Meta-analysis conducted on 108 effect sizes from 41 studies investigating the effects of pre-release behavioral conditioning on translocation outcomes revealed conditioned animals had higher survival, reduced movement, and greater site fidelity than unconditioned individuals. Notably, antipredator training, environmental enrichment, and soft release all resulted in improved survival. This suggests pre-conditioning is likely an important tool for improving future wildlife translocations. When I provided environmental enrichment to captive-born eastern box turtles, they preferred enriched environments, regardless of prior housing experience, suggesting this preference is innate. Thus, enrichment likely enhances welfare of captive box turtles by satisfying an instinctive desire to occupy complex habitat. However, pre-release trials revealed enriched turtles performed no better in ecologically relevant foraging tasks than unenriched turtles. In a predator recognition test, eight-month-old enriched turtles avoided raccoon (Procyon lotor) urine more than unenriched turtles of the same age, but this difference was not apparent one year later. These findings suggest any behavioral benefits conferred by enrichment were modest. Enriched turtles also attained smaller body sizes overall than unenriched turtles pre- release. Enrichment had minimal effects on post-release behavior and survival. However, turtles raised for 21 months moved farther from the release site and had higher post-release survival than those raised for only nine months, regardless of rearing environment. Although raising animals in enriched captivity can increase translocation success for several taxa, my experiments with box turtles and similar previous studies indicate enrichment might have limited utility for enhancing reptile translocations. Instead, implementing a longer rearing period to maximize body size before release appears to most benefit survival by reducing susceptibility to predation, which is commonly cited as a hindrance to post-release success.
Issue Date:2019-11-06
Rights Information:Copyright 2019 Sasha Tetzlaff
Date Available in IDEALS:2020-03-02
Date Deposited:2019-12

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