Dramatic shifts in Hawaiian monk seal distribution predicted from divergent regional trends

Total estimated abundance of Hawaiian monk seals was just 1,161 individuals in 2008 and this number is decreasing. Most monk seals reside in the remote Northwestern Hawaiian Islands (NWHI) where the decline is approximately 4%/yr, whereas relatively fewer seals currently occupy the main Hawaiian Islands (MHI). It is widely accepted that the MHI population is increasing, although there are no formal estimates of total abundance, population growth rate or vital rates. This lack of information has hampered efforts to anticipate future scenarios and plan conservation measures. We present the first estimates of MHI monk seal survival and age‐specific reproductive rates. Using these rates, a conservative estimate of current MHI abundance and a previously published stochastic simulation model, we estimate the MHI population growth rate and projected abundance trend. Analogous estimates for the NWHI are derived from a much richer data set. Estimated survival from weaning to age 1 yr is 77% in the MHI, much higher than recent NWHI estimates ranging from 42% to 57%. Moreover, MHI females begin reproducing at a younger age and attain higher birth rates than observed in the NWHI. The estimated MHI intrinsic rate of population growth is 1.07 compared to a 0.89–0.96 range in the NWHI. Assuming an initial abundance of 152 animals in the MHI, projections indicate that if current demographic trends continue, abundance in the NWHI and MHI will equalize in approximately 15 yr. These results underscore the imperative to mitigate the NWHI decline while devoting conservation efforts to foster population growth in the MHI, where documented threats including fishery interactions, direct killing, and disease could rapidly undo the current fragile positive trend.     

Distribution and frequencies of shark-inflicted injuries to the endangered Hawaiian monk seal (Monachus schauinslandi)

I analyzed the frequencies of wounds inflicted by sharks to the endangered Hawaiian monk seal Monachus schauinslandi at three colonies in the Northwestern Hawaiian Islands between 1990 and 2000. I applied specific criteria typical of shark bites to all injuries to avoid bias. Pooling data from all years and the three colonies revealed several patterns. Sharks injured more pups (nursing and weaned) and juveniles (1–2 years old) than adults and subadults. More female pups and male juveniles than any other size classes were injured by sharks. Almost all (97%) of the injured pups were from French Frigate Shoals. More juveniles than expected were wounded at Laysan Island and Lisianski Island. Most shark wounds were between the diaphragm and the pelvic girdle, but pups were bitten most often just behind the pelvis compared with adults who were bitten more often near the head and neck.     

Population-level impacts of natural and anthropogenic causes-of-death for Hawaiian monk seals in the main Hawaiian Islands

Identifying, assessing, and ranking the impact of individual threats is fundamental to the conservation and recovery of rare and endangered species. In this analysis, we quantify not only the frequency of specific causes-of-death (CODs) among Main Hawaiian Island (MHI) monk seals, but also assess the impact of individual CODs on the intrinsic growth rate, λ, of the MHI population. We used gross necropsy results, histopathology, and other evidence to assign probabilities of 11 COD types to each mortality and then used Monte Carlo sampling to evaluate the influence of each COD on λ. By right censoring realizations involving specific CODs, we were able to estimate λ (and its associated uncertainty) when CODs were selectively removed from influencing survival. Applying the analysis to all known and inferred deaths believed to have occurred 2004–2019, the CODs with the largest influence on λ were anthropogenic trauma, anthropogenic drowning, and protozoal disease. In aggregate, anthropogenic CODs had a larger effect on the growth rate than either natural or disease CODs. Possible bias associated with differential carcass detection, recovery, and COD classification are discussed.     

Movements and home ranges of monk seals in the main Hawaiian Islands

Hawaiian monk seals (Neomonachus schauinslandi) began recolonizing the main Hawaiian Islands (MHI) roughly 20 yr ago. The species’ abundance is still declining, but the subpopulation in the MHI is increasing by 6.5% per year. This difference may be due to differences in prey availability or habitat quality between the northwest (NWHI) and main Hawaiian Islands, which could be reflected in the movements and behavior of the seals. For example, foraging trip durations may be shorter in areas with higher forage quality. From 2007 to 2014 we deployed GPS phone tags on the islands of Molokai (n = 7), Kauai (n = 6), and Oahu (n = 6) to study movements and dive behavior. Foraging trips typically lasted 0.57 d (IQR: 0.34–0.83) and seals traveled 18 km (IQR: 10.2–30.5) per trip. Seals began benthic dives shortly after entering the water, with most dives to depths of 12–32 m. The median 95% and 50% kernel density isopleths for seals in the MHI were 149.2 km² and 23.2 km², respectively. The duration and distance of foraging trips in the MHI were shorter than that observed in other studies from the NWHI, suggesting that foraging habitat is currently better in the MHI.     

Survey for Selected Pathogens and Evaluation of Disease Risk Factors for Endangered Hawaiian Monk Seals in the Main Hawaiian Islands

A recently reestablished and increasing population of Hawaiian monk seals in the main Hawaiian Islands (MHI) is encouraging for this endangered species. However, seals in the MHI may be exposed to a broad range of human, pet, livestock, and feral animal pathogens. Our objective was to determine the movement and foraging habitats of Hawaiian monk seals in the MHI relative to the potential exposure of seals to infectious diseases in near-shore marine habitats. We captured 18 monk seals in the MHI between January 27, 2004 and November 29, 2005, tested them for various infectious diseases, and then monitored the foraging movements of 11 of them using satellite-linked radio transmitters for the next 32–167 days. All seals tested negative for canine adenovirus, calicivirus, four morbilliviruses, phocine herpes virus, Leptospira sp., and feline and canine heartworm antigen/antibody. Six of the seals tested positive on complement fixation for Chlamydophila abortus (formerly Chlamydia psittaci). Four seals demonstrated positive titers to Sarcocystis neurona, two to Neospora caninum, and two to Toxoplasma gondii. Fecal cultures showed approximately half (n = 6) positive for E. coli 0157, no Salmonella sp., and only one with Campylobacter sp. Satellite monitored seals spent considerable time foraging, traveling, and resting in neritic waters close to human population centers, agricultural activity, and livestock ranges, and sources of land-based water runoff and sewage dispersal. Consequently, Hawaiian monk seals in the MHI may be at risk of exposure to several infectious disease agents associated with terrestrial animals that can contaminate marine habitats from runoff along drainages and that are known to cause disease in marine mammals. Further, some seals overlapped substantially in their use of coastal habitats and several moved among islands while foraging and were seen on beaches near each other. This suggests that diseased seals could infect healthy conspecifics throughout the MHI.     

Prehistoric and historic distributions of the critically endangered Mediterranean monk seal (Monachus monachus) in the eastern Atlantic

The present Atlantic range of the Mediterranean monk seal (Monachus monachus), a critically endangered species, comprises two populations in the Desertas Islands and Cape Blanco region. The species is currently the subject of an action plan that encourages the recolonization of its former range. I investigated their causes of its disappearance using species records from paleo‐archeological sites and historical sightings/toponyms. I hypothesize that the species' prehistoric range extended from the continental coasts of North Africa to the Iberian Peninsula, an area larger than its current known range. It is further hypothesized that the historic range included at least 13 colonies, seven more than the present number; and that the original optimal breeding habitat was open beaches, while sea caves were a suboptimal, marginal habitat. It is suggested that hunting and the disappearance of two islands due to a historical tsunami event explain the disappearance of the other populations, leaving only those at the Desertas Islands and Cape Blanco that were sheltered in sea caves. Furthermore, the use of sea caves, in conjunction with effective legal protection in the 20th century, explains the present‐day survival of these Atlantic colonies of M. monachus.     

Odontocete spatial patterns and temporal drivers of detection at sites in the Hawaiian islands

Successful conservation and management of marine top predators rely on detailed documentation of spatiotemporal behavior. For cetacean species, this information is key to defining stocks, habitat use, and mitigating harmful interactions. Research focused on this goal is employing methodologies such as visual observations, tag data, and passive acoustic monitoring (PAM) data. However, many studies are temporally limited or focus on only one or few species. In this study, we make use of an existing long-term (2009–2019), labeled PAM data set to examine spatiotemporal patterning of at least 10 odontocete (toothed whale) species in the Hawaiian Islands using compositional analyses and modeling techniques. Species composition differs among considered sites, and this difference is robust to seasonal movement patterns. Temporally, hour of day was the most significant predictor of detection across species and sites, followed by season, though patterns differed among species. We describe long-term trends in species detection at one site and note that they are markedly similar for many species. These trends may be related to long-term, underlying oceanographic cycles that will be the focus of future study. We demonstrate the variability of temporal patterns even at relatively close sites, which may imply that wide-ranging models of species presence are missing key fine-scale movement patterns. Documented seasonal differences in detection also highlights the importance of considering season in survey design both regionally and elsewhere. We emphasize the utility of long-term, continuous monitoring in highlighting temporal patterns that may relate to underlying climatic states and help us predict responses to climate change. We conclude that long-term PAM records are a valuable resource for documenting spatiotemporal patterns and can contribute many insights into the lives of top predators, even in highly studied regions such as the Hawaiian Islands.     

庙岛群岛南五岛生态系统净初级生产力空间分布及其影响因子

净初级生产力(NPP)估算对于海岛碳源/汇研究具有重要意义。以庙岛群岛南五岛为例,结合CASA模型和区域特征构建NPP估算模型,借助RS和GIS技术进行NPP估算,进而分析南五岛NPP空间分布特征及其影响因子。结果表明:南五岛NPP总量为11043.52 t C/a,平均密度为340.19 g C m~(-2)a~(-1),处于全国平均水平,高于同纬度的西部地区,低于东部沿海大陆地区;夏季NPP总量占全年的80%左右,春季和秋季分别占11%和7%,冬季仅占1.3%;不同海岛的NPP平均密度由大到小依次为大黑山岛、北长山岛、庙岛、南长山岛和小黑山岛,各岛NPP平均密度与建设用地比例呈明显负相关;不同地表覆盖类型的NPP平均密度由大到小依次为阔叶林、针叶林、农田、草地、建设用地和裸地,林地具有较高的NPP值,说明南五岛的人工林建设具有重要生态作用;NDVI和地表覆盖类型是NPP最主要的影响参数,地形参数通过影响NDVI和地表覆盖类型间接作用于NPP结果;NPP与土壤p H、有效磷、全磷、全钾呈显著负相关,与全氮、总碳、总有机碳呈显著正相关,与含水量、速效钾和含盐量之间相关关系不明显。     

棉田十一星瓢虫种群动态及空间分布

通过田间系统调查,对棉田十一星瓢虫CoccinellaundecimpanctataL.种群动态及空间分布方面进行研究,探明捕食性天敌十一星瓢虫各虫态在南疆棉区的种群消长趋势,分析表明该虫4种虫态在棉田中均为聚集分布,成虫、幼虫和蛹的聚集原因主要是由棉蚜密度等引起,而其卵的聚集主要是由于其习性及环境因素引起。     

Predators ofLymantria dispar (Lep. lymantriidae) egg masses: Spatio-temporal variation of their impact during the 1988–89 pest generation in the mamora cork oak forest (Morocco)

In the Mamora cork oak forest (Morocco), oophagous predators of the gypsy mothLymantria dispar (L.) (Lepidoptera: Lymantriidae) are one of the main mortality factors influencing pest population dynamics. The predators destroy egg masses more by disrupting their cohesiveness than by predation. From 1987 to 1990, the impact of oophagous enemies significantly contributed to the collapse of a localized gypsy moth outbreak. Variation of egg mass dislocation intensity was greater between trees than among the different strata of a tree. The number of gypsy moth egg masses and egg predator attacks increased when oaks were large and unhealthy. Forest degradation probably explains why egg mass destruction rates were so high (60 to 90% of the eggs) in the infested forest. Oophagous predators find food and shelter under the dehiscent bark of unhealthy cork oaks.     

Modeling the spatial and temporal dynamics of riparian vegetation induced by river flow fluctuation

River flow fluctuation has an important influence on riparian vegetation dynamics. A temporally segmented stochastic model focusing on a same‐aged population is developed for the purpose of describing both spatial and temporal dynamics of riparian vegetation. In the model, the growth rate of population, rather than carrying capacity, is modeled as the random variable. This model has explicit physical meaning. The model deduces a process‐based solution. From the solution process, the probability density of spatial distribution can be derived; therefore, the spatial distribution of population abundance can be described. The lifespan of a same‐aged population and the age structure of the species‐specific population can also be studied with the aid of this temporally segmented model. The influence of correlation time of river flow fluctuation is also quantified according to the model. The calibration of model parameters and model application are discussed. The model provides a computer‐aided method to simulate and predict vegetation dynamics during river flow disturbances. Meanwhile, the model is open and allows for more accurate and concrete modeling of growth rate. Because of the Markov property involved in the process‐based solution, the model also has the ability to deal with cases of nonstationary disturbances.     

Simulation of climate‐tick‐host‐landscape interactions: Effects of shifts in the seasonality of host population fluctuations on tick densities

Tick vector systems are comprised of complex climate‐tick‐host‐landscape interactions that are difficult to identify and estimate from empirical observations alone. We developed a spatially‐explicit, individual‐based model, parameterized to represent ecological conditions typical of the south‐central United States, to examine effects of shifts in the seasonal occurrence of fluctuations of host densities on tick densities. Simulated shifts in the seasonal occurrence of periods of high and low host densities affected both the magnitude of unfed tick densities and the seasonality of tick development. When shifting the seasonal densities of all size classes of hosts (small, medium, and large) synchronously, densities of nymphs were affected more by smaller shifts away from the baseline host seasonality than were densities of larval and adult life stages. When shifting the seasonal densities of only a single size‐class of hosts while holding other size classes at their baseline levels, densities of larval, nymph, and adult life stages responded differently. Shifting seasonal densities of any single host‐class earlier resulted in a greater increase in adult tick density than when seasonal densities of all host classes were shifted earlier simultaneously. The mean densities of tick life stages associated with shifts in host densities resulted from system‐level interactions of host availability with tick phenology. For example, shifting the seasonality of all hosts ten weeks earlier resulted in an approximately 30% increase in the relative degree of temporal co‐occurrence of actively host‐seeking ticks and hosts compared to baseline, whereas shifting the seasonality of all hosts ten weeks later resulted in an approximately 70% decrease compared to baseline. Differences among scenarios in the overall presence of active host‐seeking ticks in the system were due primarily to the degree of co‐occurrence of periods of high densities of unfed ticks and periods of high densities of hosts.     

Type and spatial structure of distribution data and the perceived determinants of geographical gradients in ecology: the species richness of African birds

Aim Studies exploring the determinants of geographical gradients in the occurrence of species or their traits obtain data by: (1) overlaying species range maps; (2) mapping survey‐based species counts; or (3) superimposing models of individual species’ distributions. These data types have different spatial characteristics. We investigated whether these differences influence conclusions regarding postulated determinants of species richness patterns. Location Our study examined terrestrial bird diversity patterns in 13 nations of southern and eastern Africa, spanning temperate to tropical climates. Methods Four species richness maps were compiled based on range maps, field‐derived bird atlas data, logistic and autologistic distribution models. Ordinary and spatial regression models served to examine how well each of five hypotheses predicted patterns in each map. These hypotheses propose productivity, temperature, the heat–water balance, habitat heterogeneity and climatic stability as the predominant determinants of species richness. Results The four richness maps portrayed broadly similar geographical patterns but, due to the nature of underlying data types, exhibited marked differences in spatial autocorrelation structure. These differences in spatial structure emerged as important in determining which hypothesis appeared most capable of explaining each map's patterns. This was true even when regressions accounted for spurious effects of spatial autocorrelation. Each richness map, therefore, identified a different hypothesis as the most likely cause of broad‐scale gradients in species diversity. Main conclusions Because the ‘true’ spatial structure of species richness patterns remains elusive, firm conclusions regarding their underlying environmental drivers remain difficult. More broadly, our findings suggest that care should be taken to interpret putative determinants of large‐scale ecological gradients in light of the type and spatial characteristics of the underlying data. Indeed, closer scrutiny of these underlying data — here the distributions of individual species — and their environmental associations may offer important insights into the ultimate causes of observed broad‐scale patterns.     

太岳山主要树种空间分布格局及其维持机制研究

该研究于2014年太岳山植被保护完好地区建立了CTFS技术规范的4hm2森林监测样地,调查并鉴定了样地内胸径(DBH)大于1cm的木本植物,分析样地内的群落组成,对样地中的主要乔木树种分为幼树(1cm≤DBH≤10cm)、小树(10cmDBH≤30cm)和成年树(DBH30cm)3个生长阶段,并在去除空间异质性的基础上,采用不规则区域中的点格局分析方法,定量分析样地中主要树种在0~100m尺度上的空间分布格局;用双关联函数^g(r)研究了种群不同生长阶段的格局类型,探讨太岳山主要树种的空间分布格局产生和维持的机理,以明确该区物种的生态适应对策和种群动态。结果显示:(1)样地内共有木本植物9 698株,其中包括枯立木209株;该区群落的主要优势物种为辽东栎(Quercus wutaishanica)、白桦(Betula platyphylla)、油松(Pinus tabulaeformis)、鹅耳枥(Carpinus turczaninowii)、野山楂(Crataegus cuneata)、色木槭(Acer mono)。(2)研究区主要树种以聚集型分布为主,加入枯立木后,种群聚集程度降低并趋于随机分布。(3)^g(r)函数分析表明,样地内种群不同生长阶段的个体呈现出随年龄增加聚集程度降低的规律,这种变化过程是对种群本身的生物学特性和环境条件的综合反应。研究结果初步确定,太岳山研究区存在一定程度的密度制约效应。