Gopher Tortoise Movement; Boyd Hill Nature Preserve 2024-2025

1. A central topic in spatial ecology is identifying what determines animal movement patterns, including both exogenous and endogenous factors. Given that there are different sex-based selection pressures in mating and reproduction, movement patterns often vary between males and females in predictable manners; males of polygynous species typically move more than females to maximize mating opportunities. In female polygynous animals, selection is generally thought to favor movement patterns with smaller home ranges and high spatial site fidelity. Physiology may also constrain movement patterns in a way that can obscure sex-specific selection.
2. We used GPS loggers and physiological assays to study Gopher Tortoise (Gopherus polyphemus) movement patterns to determine how movement patterns depend on physiology (as measured by plasma lactate concentration and body condition) and movement strategy (total distance traveled over the course of the study, daily distance traveled, maximum daily displacement, home range area, burrow use) by sex.
3. Total distance traveled was positively related to body condition and negatively related to baseline lactate concentration (which is an inverse metric of aerobic fitness). Thus, total distance traveled was physiologically constrained. Home range area and burrow use were not related to any physiological metrics.
4. There was not a significant difference in total distance traveled nor daily distance traveled between male and female Gopher Tortoises, but males had larger maximum daily displacements than females. Males also had a larger home range area. Male and female Gopher Tortoises thus used different movement strategies that likely maximize fitness consistent with different selection pressures by sex in a scramble competition mating system.

1. 空间生态学（spatial ecology）的核心议题之一是明确驱动动物移动模式的各类因素，包括外源性因素与内源性因素（exogenous and endogenous factors）。鉴于交配与繁殖过程中存在基于性别的选择压力差异，雌雄个体的移动模式往往呈现出可预测的性别差异：一雄多雌物种（polygynous species）的雄性通常会比雌性移动更多，以最大化交配机会。对于一雄多雌的雌性动物而言，演化选择通常倾向于让其拥有更小的家域（home range）与较高的空间位点忠实性（spatial site fidelity）的移动模式。此外，生理状态也可能对移动模式形成限制，这种限制可能会掩盖基于性别的选择信号。
2. 本研究借助GPS记录仪（GPS loggers）与生理学检测（physiological assays），对哥法地鼠龟（Gopher Tortoise，学名Gopherus polyphemus）的移动模式展开研究，旨在明确其移动模式如何随生理状态（以血浆乳酸浓度（plasma lactate concentration）与体况（body condition）衡量）以及移动策略（本研究周期内的总移动距离（total distance traveled）、日移动距离（daily distance traveled）、每日最大移动距离（maximum daily displacement）、家域面积（home range area）与洞穴利用模式（burrow use））呈现性别差异。
3. 总移动距离与体况呈正相关，与基础乳酸浓度（baseline lactate concentration，即有氧适配性（aerobic fitness）的反向衡量指标）呈负相关，可见总移动距离受到生理状态的约束。而家域面积与洞穴利用模式则未与任何生理指标存在显著关联。
4. 雌雄哥法地鼠龟的总移动距离与日移动距离均无显著差异，但雄性的每日最大移动距离显著大于雌性，且雄性拥有更大的家域面积。由此可见，雌雄哥法地鼠龟采用了不同的移动策略，这与扩散竞争型交配系统（scramble competition mating system）中基于性别的选择压力差异相契合，进而最大化各自的适合度。