Tschopp Ayelen, Ferrari Mariano A, Crespo Enrique A, Coscarella Mariano A
Centro Para el Estudio de Sistemas Marinos, Centro Nacional Patagónico-CONICET, Puerto Madryn, Chubut, Argentina.
Facultad de Ingeniería, Universidad Nacional de la Patagonia San Juan Bosco, Puerto Madryn, Chubut, Argentina.
PeerJ. 2018 May 9;6:e4782. doi: 10.7717/peerj.4782. eCollection 2018.
Site fidelity is considered as an animal's tendency to return to a previously occupied place; this is a component of animal behaviour that allows us to understand movement patterns and aspects related to the animal's life history. Although there are many site fidelity metrics, the lack of standardisation presents a considerable challenge in terms of comparability among studies.
This investigation focused on the theoretical development of a standardised composite site fidelity index and its statistical distribution in order to obtain reliable population-level site fidelity comparisons. The arithmetic and harmonic means were used as mathematical structures in order to create different indexes by combining the most commonly used indicators for site fidelity such as Occurrence, Permanence and Periodicity. The index performance was then evaluated in simulated populations and one real population of Commerson's dolphins ( (Lacépède 1804)). In the first case, the indexes were evaluated based on how they were affected by different probability values such as the occurrence of the individual within the study area (φ) and capture probability (). As a precision measure for the comparison of the indexes, the Wald confidence interval (CI) and the mean square error were applied. Given that there was no previous data concerning the distribution parameters of this population, bootstrap CIs were applied for the study case.
Eight alternative indexes were developed. The indexes with an arithmetic mean structure, in general, had a consistently inferior performance than those with a harmonic mean structure. The index IH4, in particular, achieved the best results in all of the scenarios and in the study case. Additionally, this index presented a normal distribution. As such, it was proposed as a standardised measure for site fidelity (Standardised Site Fidelity Index-SSFI).
The SSFI is the first standardised metric that quantifies site fidelity at a populational level. It is an estimator that varies between zero and one and works in situations where detection is not perfect and effort can be constant or not. Moreover, it has an associated CI that allows users to make comparisons.
地点保真度被认为是动物返回先前占据地点的倾向；这是动物行为的一个组成部分，使我们能够了解与动物生活史相关的运动模式和方面。尽管有许多地点保真度指标，但缺乏标准化在研究之间的可比性方面带来了相当大的挑战。
本研究聚焦于标准化综合地点保真度指数的理论发展及其统计分布，以获得可靠的种群水平地点保真度比较。算术平均数和调和平均数被用作数学结构，通过结合地点保真度最常用的指标（如出现率、持久性和周期性）来创建不同的指数。然后在模拟种群和一个柯氏喙鲸（Lacépède 1804）的真实种群中评估指数性能。在第一种情况下，根据指数受不同概率值（如个体在研究区域内的出现率（φ）和捕获概率（））的影响程度来评估指数。作为指数比较的精度度量，应用了 Wald 置信区间（CI）和均方误差。鉴于此前没有关于该种群分布参数的数据，在研究案例中应用了自助法 CI。
开发了八个替代指数。一般来说，具有算术平均数结构的指数性能始终不如具有调和平均数结构的指数。特别是指数 IH4，在所有情景和研究案例中都取得了最佳结果。此外，该指数呈现正态分布。因此，它被提议作为地点保真度的标准化度量（标准化地点保真度指数 - SSFI）。
SSFI 是第一个在种群水平上量化地点保真度的标准化指标。它是一个在零和一之间变化的估计量，适用于检测不完美且努力程度可以恒定或不恒定的情况。此外，它有一个相关的 CI，允许用户进行比较。
