基于标记-重捕模型开展野生动物红外相机种群监测的方法及案例

红外相机技术的广泛应用推动了动物种群生态学研究方法的发展和革新, 特别是基于标记-重捕模型框架通过非损伤取样方式对物种数量和密度等种群参数的可靠估计, 为保护濒危物种和评估保护成效提供了有力的科学依据。对于身体上具有独特天然标记的动物(如多数猫科动物), 可依据红外相机拍摄身体上的独特斑点或条纹鉴别个体, 再运用标记-重捕模型, 估计动物种群数量、密度等参数。本文概述了标记-重捕模型的基本原理、特点以及国内外的应用, 特别是近年来发展出的空间标记-重捕模型。总结了从相机布设到数据分析的具体流程、操作原则, 并以青城山家猫为实例, 展示了应用红外相机数据通过空间标记-重捕模型估计种群密度和数量的基本步骤。最后展望了该模型在种群动态、景观廊道设计、资源选择等方面的应用和发展趋势。     

中华白海豚生态学研究进展

中华白海豚(Sousachinensis)是国家一级重点保护水生野生动物,处于食物链的顶端,是近岸海洋生态系统健康状况的指示物种和海洋生物多样性保护的旗舰物种,具有重要的生态、科学和文化价值。自20世纪90年代开始,中华白海豚的研究逐渐兴起;近年来,随着3S技术、生态模型及分子生物学等技术方法的发展应用,在中华白海豚种群生态学、行为生态学、分子生态学等领域的研究取得了长足发展。国内外学者利用截线抽样法和标志重捕法,调查研究了全球范围内已知的中华白海豚种群的分布、数量等生态信息;在物种保护的背景下,开展了对中华白海豚栖息地的选择偏好、栖息地质量评价及潜在栖息地的预测研究;探究了中华白海豚的觅食行为和繁殖行为的规律和其他行为的生态意义;分子生物技术的应用,初步揭示了中华白海豚的遗传分化规律,以及该物种对气候变化表现出的脆弱性;涉海工程、水下噪声、水体污染、渔业活动等人类活动仍是目前中华白海豚面临的主要威胁。本文在总结已有研究的基础上,对未来该物种的生态学研究与保护提出了以下展望:(1)建立国家层面的动态基线数据库,以更好地追踪中华白海豚的种群动态及栖息地环境变化;(2)构建栖息地识别及保护...     

大足鼠种群动态的非线性模型及逐步回归分析

本文提出了一种从原始数据中获取关于种群动态机制的基本信息的,以非线性模型为基础的逐步回归逐步预测的种群动态分析法。并以作者１９８９－１９９１年间于四川邛崃定点进行示志重捕以及夹捕解剖所得的关于农田大足鼠种群生态学特征的数据为例,对大足鼠和种群密度与年龄组成,各年龄组性比、繁殖特征以及气象等因子的关系进行了初步的分析,定量地确定了当前的各生态因子对未来的大足鼠种群密度的作用,并对数量了初步的分析的讨     

三种方法对天山马鹿喀拉乌成山种群数量的比较

为了获得天山马鹿Cervuselaphus songaricus喀拉乌成山种群数量,并评估不同种群数量统计方法之间的差异。2010～2012年利用样线法、粪堆计数法以及非损伤性标记重捕法对喀拉乌成山的天山马鹿种群数量进行研究,发现样线法估计的种群数量最低,仅为1.316～1.656头/km2;而非损伤性标记重捕法获得的种群数量最高,为2.075～3.11头/km2;粪堆计数法获得的数据居中,为1.422～2.844头/km2,说明不同的方法之间很难具有可比性。     

大中型兽类种群数量估算的研究进展

大中型兽类种群数量的估算是动物生态学中重要的基本问题, 受到研究者、管理者和公众的共同关注。国际上从20世纪中期开始研究该问题, 已出现了多种研究方法和相应案例, 且还在快速发展, 但世界各地仍有很多物种的种群数量尚未知晓。在我国, 从20世纪80年代开始调查大中型兽类种群数量, 取得了重要进展, 也还有很多物种的种群数量尚不清楚。因此, 有必要归纳国际上种群数量估算的研究进展, 同时, 总结国内研究的现状、优势和趋势, 供研究者参考。本文首先选择估算大中型兽类种群数量的原理、数据来源和模型这3个要素归纳出简明的研究框架, 将现有的多种方法置于其中予以阐述。在该框架下, 根据估算原理分为4大类方法, 为距离取样法、标志重捕法、基于遇见率法和遥感影像直接计数法。针对每一大类方法, 论述其基本原理模型和模型假设, 说明能实现该原理的相应数据来源(视觉观测、红外相机拍摄、DNA微卫星识别、卫星定位跟踪、声音监测或遥感影像)的特点及如何实现该原理, 评价其适用性及优缺点, 并选择其中具有可比性的方法予以比较评价。其次, 参照该研究框架, 总结我国的研究现状, 分析未来发展的优势和趋势: 我国的红外相机数据积累充分, 可以发展以此为数据源的距离取样法、标志重捕法和基于遇见率法; 发展以粪便样品为数据来源的距离取样法和粪便DNA标志重捕法; 相比地面调查数据, 获取高分辨率遥感影像数据更容易, 尽量以此估算符合适用条件的大中型兽类的种群数量。最后, 本文提出了适用于我国大中型兽类种群数量的估算方法的选择流程, 供研究者参考。     

被动式电子标签用于花鼠种群动态研究的可行性

在野生动物研究过程中经常需要对动物个体进行标记。传统的标记方法存在着标记物易脱落、可能影响被标记动物的生理和行为、难于进行个体识别等缺点。被动式电子标签(passive integrated transponder, PIT)是基于射频识别技术的电子标签,可用于体内标记,具有不易脱落消失且能够进行个体识别的优点。我们在凉水国家级自然保护区以PIT标签为标记物,采用标志重捕技术开展花鼠(Eutamias sibiricus)的种群动态研究,同时对应用PIT标签的可靠性进行了研究。2011年秋季至2012年春季共标记花鼠个体140只,其中86只被重捕至少1次。2011年秋季标记的72只个体中有38只在2012年春季被重捕。重捕的花鼠个体注射口愈合完好,体重无明显降低。结果表明PIT标签是一种安全可靠、识别迅速、数据准确、不易丢失、可循环使用的体内标记电子标签,适用于基于个体识别的小型哺乳动物生态学研究。     

二个区域的封闭种群的标记重捕模型

通过引入区域的初始比例因子,考虑了二个区域A与B的封闭种群标记重捕模型,再利用完整的极大似然函数和多项分布函数的性质,给出了当个体在不同区域的个体捕捉率相等时的二个区域之间的转移概率与各区域的初始比例的求法,推导出在不同区域的个体捕捉率不相等但个体低转移率条件下二个区域的封闭种群的标记重捕模型的参数表达式,并用实例说明。     

三江源国家级自然保护区内云塔村雪豹种群动态

种群监测可为物种研究和保护提供关键信息和依据。雪豹(Panthera uncia)作为亚洲高山生态系统的顶级捕食者和旗舰种, 一直是研究和保护的重点, 但其难以到达的栖息地、隐秘的行踪和广阔的家域使其监测工作开展难度较大, 雪豹种群动态研究较为匮乏。本研究在2013年10月至2019年1月期间, 使用当地社区维护的红外相机, 监测三江源国家级自然保护区通天河沿保护分区内青海省玉树州哈秀乡云塔村雪豹种群的密度和动态, 共识别出35只雪豹个体。基于数据质量较好的2015、2016、2017年连续3年的红外相机数据各年截取3个月数据, 使用空间标记-重捕模型估算种群数量和密度, 发现当地雪豹种群和成年个体密度基本维持稳定, 种群增长率为1.02, 但监测期间雪豹个体更替明显, 平均个体更替率为0.44, 并且围绕两片雪豹核心利用区域发生了领域取代。推测雪豹种群具有较多个体更替和领域取代是因为种群处在雪豹潜在扩散通道上, 或调查范围未覆盖完整种群。本研究是国内首次对雪豹进行较为长期的种群动态监测和分析, 研究结果体现了动态监测的重要性, 也显示出以当地社区为主体监测哺乳动物种群的可能性。     

基于红外相机数据评估华南地区豹猫的种群密度和活动节律

可靠的种群密度数据对野生动物的保护和管理十分重要。豹猫(Prionailurus bengalensis)是中国分布最广且常见的猫科动物, 但野生种群密度估算的研究并不多。本研究于2020年6月至2021年5月在香港新界嘉道理农场暨植物园开展红外相机调查, 利用空间标记-重捕法估算当地豹猫的种群密度并用核密度估计方法分析其活动节律。本次调查以网格方式布置红外相机, 在约1.5 km²的研究范围之内设置了19个相机位点, 每个位点安装2台相机以获取豹猫身体两侧花纹来进行个体识别。连续12个月调查共捕获113次有效的豹猫拍摄事件, 当中仅61次事件的照片足够清晰以进行个体识别。基于种群封闭的要求, 我们以2个月为单位将12个月的数据分为6个采样期去分析豹猫种群密度, 结果显示仅两个采样期的估算值最为准确, 分别为0.64 ± 0.31 (0.26-1.55)只/km²和0.87 ± 0.48 (0.31-2.40)只/km², 是已知全球豹猫密度最高的地点之一。结果还发现, 雨季研究地点的豹猫并无明显的日活动节律, 在旱季则偏夜行-晨昏行性多一些, 但也有一定的日间活动; 雨季和旱季的日活动节律无显著差异。本研究是首次以个体识别配以空间标记-重捕模型对中国大陆地区豹猫种群密度调查的研究; 我们也提出一些关于红外相机架设方法的建议, 以提高照片个体识别的准确度并增加重捕次数, 最后提高密度估算的准确度。本研究也进一步证明豹猫适应性极强, 在活动节律上表现出极高的可塑性, 在严格保护下可以恢复健康的种群。     

陆桥岛屿环境下社鼠种群数量的估算方法

根据2010年3月—11月在千岛湖地区2个岛屿上社鼠(Niviventer confucianus)的标志重捕数据,分别用Jolly-Seber法、修正Lincoln指数法、Schnabel法和MNA法计算两个岛屿上社鼠种群数量,并深入探讨在陆桥岛屿环境下估算社鼠种群数量的适用方法。研究结果显示,在满足Jolly-Seber法的条件下,通过该方法计算的结果与修正Lincoln指数法无显著差异。但在野外实验中,并不是所有的重捕数据都满足Jolly-Seber法的条件,而且该方法不能估算头尾两月的数量。因此,修正Lincoln指数法更适于估算陆桥岛屿环境下社鼠的种群数量。可为今后开展陆桥岛屿环境下鼠类种群生态学研究奠定基础。     

Demographic consequences of changing body size in a terrestrial salamander

Changes in climate can alter individual body size, and the resulting shifts in reproduction and survival are expected to impact population dynamics and viability. However, appropriate methods to account for size‐dependent demographic changes are needed, especially in understudied yet threatened groups such as amphibians. We investigated individual‐ and population‐level demographic effects of changes in body size for a terrestrial salamander using capture–mark–recapture data. For our analysis, we implemented an integral projection model parameterized with capture–recapture likelihood estimates from a Bayesian framework. Our study combines survival and growth data from a single dataset to quantify the influence of size on survival while including different sources of uncertainty around these parameters, demonstrating how selective forces can be studied in populations with limited data and incomplete recaptures. We found a strong dependency of the population growth rate on changes in individual size, mediated by potential changes in selection on mean body size and on maximum body size. Our approach of simultaneous parameter estimation can be extended across taxa to identify eco‐evolutionary mechanisms acting on size‐specific vital rates, and thus shaping population dynamics and viability.     

ABUNDANCE OF BOTTLENOSE DOLPHINS IN THE BAYS, SOUNDS, AND ESTUARIES OF NORTH CAROLINA

We conducted a mark-recapture survey of bottlenose dolphins Tursiops truncatus in the bays, sounds, and estuaries of North Carolina during July 2000, using photographic identification techniques. During this survey we took 7,682 photographs of dolphins and, of these, 3,457 images were of sufficient quality for analysis. We identified 306 dolphins from distinctive nicks and notches on their dorsal fins. Eighry-six dolphins were photographed on more than one occasion during the course of the survey; one dolphin was photographed on four separate days. We then applied the results of our photographic analyses to several mark-recapture models and examined potential violations of the assumptions of these models, including an unexpected correlation between photo quality and mark distinctiveness. Our analysis suggests that our results are robusr to possible violations of these assumptions. The resulting estimates were then scaled to account for the proportion (0.46) of unmarked dolphins in the population. Our best estimate of the number of dolphins present in the inshore waters of North Carolina during July 2000 is 1,033 with a 95% Confidence Interval of 860–1,266 (CV = 0.099). Most dolphins were found in the northern part of the study area, which includes the second largest estuarine system in the United States.     

An integrated population model for a long‐lived ungulate: more efficient data use with Bayesian methods

We develop an integrated population model for Svalbard reindeer Rangifer tarandus platyrhynchus, and demonstrate how this type of model can be used to extract more information from the data and separate different sources of variability in population estimates. Our model combines individual mark–recapture data with population counts and harvesting data within a Bayesian model framework, and accounts for observation error, environmental and demographic stochasticity, and age structure. From this model we obtain annual estimates of age‐specific population size, survival and fecundity. The model provides estimates of age structure at a finer scale than that found in the census data, and enables us to estimate survival for the period before calves are first caught and marked, i.e. before they enter the individual mark–recapture data. The modeling framework provides an improved approach to studying age‐structured populations that are imperfectly censused and where the demography of only a sample of individuals is known. We use data from independent censuses of the same population to evaluate population estimates obtained from the model, and show that it is successful at correcting for different types of observation error. Based on our model results, we suggest that allocating resources to the collection of supplementary mark–recapture data could improve the reliability of population projections more than making regular population censuses as exhaustive as possible. Our work demonstrates how integrated Bayesian population modeling can be used to increase the amount of information extracted from collections of data, identifying and disentangling sources of variation in individual performance and population size. This represents an important step towards increasing the predictive ability of population growth models for long‐lived species experiencing changes in environmental conditions and harvesting regimes.     

Effect of Tooth Removal on Recaptures of Raccoons

Abstract: Researchers have extensively used mark—recapture techniques to obtain information on demographic parameters of wildlife populations. However, researchers have recognized that a number of factors can influence capture probabilities of wildlife species, which in turn can bias mark—recapture estimates of demographic parameters. Tooth extraction, which is a commonly used technique in studies of mesopredator species to obtain precise age estimates and to monitor the use of vaccine baits, is an aspect of animal handling that clearly might affect the recapture probability of individuals. However, the effect that tooth removal has on the individual recapture probabilities of wildlife species is unknown. During 2005, we trapped and marked 91 raccoons (Procyon lotor) in northern Indiana, USA, as part of a mark—recapture study designed specifically to determine if tooth extractions have an effect on recapture probabilities of individuals. We performed tooth extractions on 50% of the raccoons at the time of capture, and we attempted to balance tooth extractions with respect to sex and age of raccoons. We used logistic regression to model the effects of sex, age, and tooth removal on recapture probabilities, and we used Mann—Whitney U-tests to examine the effect of tooth removal on the number of times we recaptured individuals. The probability of recapture differed between sexes but did not differ as a function of tooth removal or among age classes. In addition, we failed to detect any difference in the mean number of times that we recaptured raccoons between the tooth removed and non—tooth-removed groups. Our results suggest that managers can use tooth extractions as an effective management tool without biasing population estimates or compromising other management objectives.     

Combining capture–recapture data and known ages allows estimation of age‐dependent survival rates

In many animal populations, demographic parameters such as survival and recruitment vary markedly with age, as do parameters related to sampling, such as capture probability. Failing to account for such variation can result in biased estimates of population‐level rates. However, estimating age‐dependent survival rates can be challenging because ages of individuals are rarely known unless tagging is done at birth. For many species, it is possible to infer age based on size. In capture–recapture studies of such species, it is possible to use a growth model to infer the age at first capture of individuals. We show how to build estimates of age‐dependent survival into a capture–mark–recapture model based on data obtained in a capture–recapture study. We first show how estimates of age based on length increments closely match those based on definitive aging methods. In simulated analyses, we show that both individual ages and age‐dependent survival rates estimated from simulated data closely match true values. With our approach, we are able to estimate the age‐specific apparent survival rates of Murray and trout cod in the Murray River, Australia. Our model structure provides a flexible framework within which to investigate various aspects of how survival varies with age and will have extensions within a wide range of ecological studies of animals where age can be estimated based on size.     

Who are we sampling? Apparent survival differs between methods in a secretive species

Survival is a fundamental parameter in population dynamics with increasing importance in the management and conservation strategies of wildlife populations. Survival probability in vertebrates is usually estimated by live‐encounter data obtained by means of physical mark–capture–recapture protocols. Non‐invasive acoustic marking relying on individual‐specific features of signals has been alternatively applied as a marking technique, especially in secretive species. Nevertheless, to date no research has compared survival rate estimates obtained by acoustic and physical marking. We estimated half‐yearly and annual survival and recapture rates of a secretive and threatened passerine, the Dupont's lark Chersophilus duponti, using two separate live‐encounter data sets of males collected simultaneously by physical and acoustic marking in the same study area. The separate analysis of both methods led to different model structures, since transient individuals had to be accounted for in the acoustic marking but not in the physical marking data set. Furthermore, while reencounter probabilities did not differ between methods, survival estimates employing physical marking were lower than those obtained acoustically, especially between the postbreeding and the breeding period when the apparent survival of colour‐banded birds was twice as low as for acoustic marking. The combination of marking methods suggested the existence of different subsets of individuals differentially sampled within the population: whereas colour‐banded males seemed to represent the territorial fraction of the population, both resident and floater individuals were probably detected by acoustic marking. Using traditional mark–recapture methods exclusively could have misled our estimates of survival rates, potentially affecting prospective predictions of population dynamics. Acoustic marking has been poorly applied in mark–recapture studies, but might be a powerful complement to obtain accurate estimates of fundamental demographic parameters such as survival and dispersal.     

MULTISITE MARK-RECAPTURE FOR CETACEANS: POPULATION ESTIMATES WITH BAYESIAN MODEL AVERAGING

Mark-recapture techniques are widely used to estimate the size of wildlife populations. However, in cetacean photo-identification studies, it is often impractical to sample across the entire range of the population. Consequently, negatively biased population estimates can result when large portions of a population are unavailable for photographic capture. To overcome this problem, we propose that individuals be sampled from a number of discrete sites located throughout the population's range. The recapture of individuals between sites can then be presented in a simple contingency table, where the cells refer to discrete categories formed by combinations of the study sites. We present a Bayesian framework for fitting a suite of log-linear models to these data, with each model representing a different hypothesis about dependence between sites. Modeling dependence facilitates the analysis of opportunistic photo-identification data from study sites located due to convenience rather than by design. Because inference about population size is sensitive to model choice, we use Bayesian Markov chain Monte Carlo approaches to estimate posterior model probabilities, and base inference on a model-averaged estimate of population size. We demonstrate this method in the analysis of photographic mark-recapture data for bottlenose dolphins from three coastal sites around NE Scotland.     

Assessing population parameters and trends of Guiana dolphins (Sotalia guianensis): An eight‐year mark‐recapture study

This study represents the first attempt to study the population dynamics of Guiana dolphins (Sotalia guianensis), by evaluating a set of demographic parameters. The population of the Caravelas River estuary, eastern Brazil, was systematically monitored through a long‐term mark‐recapture experiment (2002–2009). Abundance estimates revealed a small population (57–124 dolphins), comprised of resident dolphins and individuals that temporarily leave or pass through the study area. Temporary emigration from the estuary to adjacencies (γ″= 0.33 ± 0.07 SE) and return rate (1 ?γ′= 0 .67) were moderate and constant, indicating that some dolphins use larger areas. Survival rate (?= 0.88 ± 0.07 SE) and abundance were constant throughout the study period. Power analysis showed that the current monitoring effort has high probability of detecting abrupt population declines (1 ?β= 0.9). Although the monitoring is not yet sensitive to subtle population trends, sufficient time to identify them is feasible (additional 3 yr). Despite such apparent stability, this population, as many others, inhabits waters exposed to multiple human‐related threats. Open and closed population modeling applied to photo‐identification data provide a robust baseline for estimating several demographic parameters and can be applied to other populations to allow further comparisons. Such synergistic efforts will allow a reliable definition of conservation status of this species.     

When is enough … enough? Effective sampling protocols for estimating the survival rates of seabirds with mark-recapture techniques

Capsule: Lower intensity mark-recapture studies, such as those undertaken by citizen scientists, provide an opportunity to improve the spatial representation of survival estimates for birds. Colonial nesting birds are particularly suited to this because, for many species, large numbers of breeding birds and chicks can be located relatively easily. The minimum level of recapture effort required to accurately estimate true survival rates and detect temporal variation largely depended on the respective ringing effort. Therefore, mark-recapture studies should consider both aspects of the field study when setting or adjusting minimum effort guidelines. Furthermore, achieving reliable estimation with short time-series required more intensive survey designs, highlighting the importance of longevity when planning these studies.

Aims: To provide minimum guidelines of field effort that can be used to manage smaller projects that monitor survival rates, such as those reliant on citizen scientists.

Methods: We conducted a sensitivity analysis that evaluated the statistical power associated with using different mark-recapture survey designs to estimate a fixed ‘true’ survival rate and detect sources of temporal variation and individual heterogeneity within the population.

Results: Isolating temporal variation with a good degree (90%) of certainty required the highest levels of survey effort. Based on the assessed survey designs, we recommend studies that have a ten-year trajectory and a recapture rate of 0.6, aim to mark at least 200 new adults per year. The recommended number of marked individuals will decrease if it is possible to achieve higher rates of recapture. Lower rates of juvenile survival and delayed reproduction mean that seabird mark-recapture survey designs that target both chicks and adults offer only marginal improvements in resolving the survival rates of adults, when compared to designs targeting adults only. However, collecting juvenile mark-recapture data provide access to age-specific vital rates that are also valuable for assessing the population dynamics of seabirds.

Conclusion: The addition of chicks is unlikely to improve the resolution of adult survival rates markedly, although for species with low natal dispersal and earlier ages of maturity, these data may allow the estimation of other vital rates, such as juvenile survival rates and age of maturity. Implementing minimum effort guidelines potentially enables the effective management of smaller mark-recapture studies, thus minimising the risk that studies fail to achieve the data conditions necessary for robust estimation of survival rates.     

Are we overestimating recovery of sturgeon populations using mark/recapture surveys?

Mark‐recaptures studies are often conducted to monitor trends in sturgeon populations. However, many of these studies experience low recapture rates, minimal movement between marking‐recapture phases suggesting that sturgeon as a group are not conducive to mark‐recapture techniques. In this study, two mark‐recapture studies that were conducted differently were reviewed. A study was conducted on the Mattagami River using random nets set throughout the study area in both the mark and recapture phases. The other study was conducted on Lake of the Woods and marked sturgeon in tributaries during the spawning period and the recapture phase within the lake and river during the summer foraging period using random nets sets. Sturgeon's conduciveness to mark‐recapture studies was assessed on the Mattagami River mark‐recapture study by determining detection probability (p) using a hierarchical Bayesian model with data augmentation among three effects: individual effect, temporal effects, and behavioural response effects. Detection probability was constant over individuals and temporally suggesting model M₀ (Otis, Burnham, White, & Anderson, 1978 ) was suitable for lake sturgeon in the Mattagami River; only the M₀ would converge for the Lake of the Woods study. For this study, the assumption that “all individuals have the same probability of being captured during the marking phase” was believed to have been violated given approximately 16%–20% of adult Lake Sturgeon from a population spawn within a year. A population estimate accounting for p provided estimates 56% lower than calculated by a Chapman modification of the Peterson estimate for a closed population. Bias was believed to have been introduced as the Lake of the Woods population did not account for the non‐spawning adults that were encountered during the recapture phase and not vulnerable during the initial marking phase. This was not unique to the Lake of the Woods study as other sturgeon studies, especially multi‐year, assumes a closed population which potentially biased estimates and overestimated their recovery.