Estimating fecundity and density dependence from mark-recapture data for making population projections

Forecasting changes in size and distributions of populations is at the forefront of ecological sciences in the 21st century. Such forecasts require robust estimators of fecundity, survival and density-dependence. While survival estimation is the main focus of mark-recapture modelling, fecundity and density dependence are rarely the subject of these models. Here, we demonstrate that these parameters can be simultaneously estimated in a Bayesian framework using only robust design mark-recapture data. Using simulated capture histories, we show that this framework (which we named CJS-pop) can estimate vital rates and their density dependence with little bias. When CJS-pop is applied to capture history data from Brown Creeper (Certhia americana), it provides estimates of fecundity that is expected from the breeding biology of this species. Finally, we illustrate that density dependence, even when estimated with uncertainty in the CJS-pop framework, regularizes population dynamics and reduces the frequent population extinctions and explosions observed under density-independent models. While CJS-pop as a whole is a useful addition to the current mark-recapture modelling toolbox, we argue that the independent components of this framework in estimating fecundity and density dependence can be integrated to other CJS frameworks, potentially creating models capable of population projections.

Generating Realistic Stock Market Order Streams

We propose an approach to generate realistic and high-fidelity stock market data based on generative adversarial networks (GANs). Our Stock-GAN model employs a conditional Wasserstein GAN to capture history dependence of orders. The generator design includes specially crafted aspects including components that approximate the market's auction mechanism, augmenting the order history with order-book constructions to improve the generation task. We perform an ablation study to verify the usefulness of aspects of our network structure. We provide a mathematical characterization of distribution learned by the generator. We also propose statistics to measure the quality of generated orders. We test our approach with synthetic and actual market data, compare to many baseline generative models, and find the generated data to be close to real data.

Lietuvos kodas: Istorijos fragmentai Vilniaus miestovaizdyje

Straipsnyje analizuojami Vilniaus paminklai kaip praeities reprezentacijos. Paminklai istorinėms asmenybėms ir įvykiams pateikia identiteto konstravimo medžiagą. Palaikomi istorijos vadovėlių ir turistų vadovų, jie kuria valstybės identitetą tiek miestiečiams, tiek ir miesto svečiams. Kita vertus, paminklai atkreipia dėmesį į istorinius įvykius ir asmenybes, vienus primindami, kitus palikdami užmarštyje.Kaip ir kitų šalių, kurios buvo okupuotos ir kuriose keitėsi valdžios, Lietuvos miestuose, ypač Vilniuje, buvo naikinami lietuviški simboliai bei statomi okupacinių valdžių monumentai. Atkūrus nepriklausomybę, Vilniaus, kaip ir kitų Lietuvos miestų, miestovaizdyje mažėja okupacinių valdžių ir daugėja Lietuvos istorijai svarbias istorines asmenybes ir įvykius ženklinančių paminklų.Lithuanian code: Captures of history in Vilnius cityscapesViktorija Žilinskaitė SummaryThe article analyses the monuments that capture history in Vilnius cityscapes. Monuments for historical personalities and events are material for the construction of identity. Supported by knowledge of history books and tourist guides they construct identity both for inhabitants and visitors. On the other hand, they are spotlights pointing to history moments, reminding about some and keeping in silence other events and personalities.Like in other countries that experienced change of powers and occupational totalitarian regimes, cityscapes of Lithuanian towns, especially of its capital Vilnius, experienced destruction of Lithuanian monuments and erection of symbols of occupational powers. After restoration of Lithuanian Independence, the Lithuanian capital, as well as other cities and towns, is going through the processes of re-Lithuanisation.Key words: urban representation, visual culture, symbols of history, cultural heritage

Mark-recapture estimates of daily survival rates of two damselflies (Coenagrion puella and Ischnura elegans)

Male-biased operational sex ratios are very common in sexually mature dragonflies. These may be due to differential survival or differences in time spent at the breeding site by the sexes. Because most studies are carried out at the breeding site, these two processes can be measured as survival rates or recapture rates using modern capture–mark–recapture methods. We marked 66 female and 233 male Coenagrion puella, and 137 female and 347 male Ischnura elegans during three capture periods spread over 18 days. Each time an animal was recaptured it was re-marked so that the capture history of any captured animal could be readily identified. We recaptured 131 C. puella and 55 I. elegans at least once. We used the Cormack–Jolly–Seber model to estimate the daily probability of survival and recapture. The probability of recapture was, on average, more than three times higher for male C. puella (0.489) than females (0.133) with significant day to day variation. The daily probability of survival did not differ significantly between the sexes (0.860), with no significant variation among days. In contrast, in I. elegans the probability of recapture did not differ between the sexes (0.139 for the first 5 days; between 0.032 and 0.287 for the final 3 days), but the daily probability of surviving was much higher for males (0.812) than for females (0.579). Assuming that the sex ratio was unity at sexual maturity, the recapture and survival rates predicted well the sex ratio of the sample of C. puella but predicted more males than were observed in the sample of I. elegans. This suggests that male I. elegans may suffer higher mortality than females in the immature stage.

Population dynamics of, and habitat use by, Austrlian native rodents in wet sclerophyll forest, Tasmania I. Rattus lutreolus velutinus (Rodentia : Muridae)

A local population of velvet-furred rats, Rattus lutreolus velutinus, was studied for 15 months in wet sclerophyll forest in south-eastem Tasmania using mark-recapture techniques. Individuals in the trappable population were readily caught with 90% of captures being recaptures (73 individuals caught 706 times). During winter and the summer breeding season, all individuals had an equal likelihood of recapture, irrespective of sex, age, season or previous capture history. Habitat use was investigated by analysing floristic and structural variation within a 4-ha trapping grid using TWINSPAN. Four heterogeneous habitat groups were defined and population data are compared among these groups. Areas of densest ground cover were preferred by R. 1. velutinus; open areas were avoided. Throughout the study, female rats were captured in the areas with most cover to 50 cm in height; during winter, males were caught in areas of the trapping grid with more sparse ground cover, in lower numbers than females. At the onset of breeding in summer, numerous males were captured in the areas of thickest ground cover occupied by females. These data are discussed in relation to social spacing, habitat utilisation and female choice.