Effect of Net-Gun Capture on Survival of Mule Deer

Capture techniques to deploy radio-collars often risk mortality and injury to the animal. Capture-induced mortality can affect population sizes but also introduces bias in survival estimates based on data from captured animals. In recent years, a large-scale research and monitoring project in Utah, USA, has involved capturing and radio-collaring hundreds of mule deer (Odocoileus hemionus), a species of great interest in large parts of North America. Our objective was to investigate how the survival rates of these mule deer were affected by capture and handling. During winters of 2014–2018, an experienced capture crew net-gunned and fitted 1,805 animals with global positioning system (GPS)-collars. We estimated survival rates during the first 6 weeks after capture using Cox proportional hazard regression, and compared the survival rates of animals that were captured in a particular year to those of animals that were not captured but fitted with a GPS-collar in a previous year. We used a model selection framework to evaluate how long survival rates of captured animals were different from those of animals that were not captured. Our results indicated that weekly survival rates of captured animals were 0.985 ± 0.003 (SE), 0.988 ± 0.002, and 0.990 ± 0.001 in weeks 1, 2 and 3, respectively. Weekly survival rates of captured deer during weeks 4–6 were 0.993 ± 0.001, the same as those of deer that were not captured at the same time. Furthermore, post-capture survival rates were positively influenced by body size and negatively influenced by age. We conclude that the mortality resulting from helicopter capture was low but recommend comparing newly captured and previously captured individuals to examine what proportion of observed mortality is likely capture-related. © 2020 The Wildlife Society.     

The effects of capture spiral composition and orb-web orientation on prey interception

Cribellar prey capture threads found in primitive, horizontal orb-webs reflect more light, including ultraviolet wavelengths, than viscous threads found in more derived, vertical orb-webs. Low web visibility and vertical orientation are each thought to increase prey interception and may represent key innovations that contributed to the greater diversity of modern, araneoid orb-weaving spiders. This study compares prey interception rates of cribellate orb-webs constructed by Uloborus glomosus (Uloboridae) with viscous orb-webs constructed by Leucauge venusta (Tetragnathidae) and Micrathena gracilis (Araneidae). We placed sectors of cribellar and viscous threads side by side in frames that were oriented either horizontally or vertically. The webs of both U. glomosus and L. venusta intercepted more prey when vertically oriented. In each orientation L. venusta webs intercepted more insects than did U. glomosus. Although this is consistent with the greater visibility of cribellar threads, the more closely spaced capture spirals of L. venusta may have contributed to this difference. Micrathena gracilis webs intercepted more prey than did U. glomosus webs, although web orientation did not affect the performance of this araneoid species. The stickier and more closely spaced capture spirals of M. gracilis may have enhanced the interception rates of this species and accounted for the greater number of smaller dipterans retained in its webs. The tendency for these slow, weak flight insects to be blown into both horizontal and vertical webs may account for similar interception rates of horizontal and vertical M. gracilis webs. These observations support the enhanced prey interception of vertically oriented orb-webs, but offer only qualified support for the contributions of lower visibility viscous capture threads.     

Capturing Common Loons during prenesting and nesting periods

ABSTRACT Several techniques have been used to capture Common Loons (Gavia immer), but effectiveness is limited during periods of the breeding season when loons do not have chicks. From 2005 to 2008, we studied loons in northern Wisconsin and used night lighting to capture loons on nests and also designed a lift net for capturing loons prior to nesting. At night, incubating loons were approached by boat and, when within about 30–60 m, we focused a spotlight on the loon and, once at the nest, captured loons using a landing net. Using this technique, we captured 23 loons in 29 attempts (79%). In addition, taped calls and loon decoys were used to entice prenesting, territorial loons into a shoreline‐based, lift‐net trap at a capture efficiency of 67% (10 captures in 15 attempts) during the second year of use. Our diurnal lift‐net trap and night‐light nest‐capture techniques allowed us to capture adult Common Loons during periods of the breeding season when previous investigators have found loons difficult to catch. These techniques may also be useful for capturing other species of territorial waterbirds, especially other species of loons.     

Incidental capture of American Crows in coyote‐sized box traps

ABSTRACT American Crows (Corvus brachyrhynchos) are difficult to capture. I used a simple technique (box traps) to capture 151 crows incidental to my eastern coyote (Canis latrans) research at two study sites in eastern Massachusetts. Crows were captured at a higher rate during the spring (winter = 33 captures, spring = 70, summer = 22, and fall = 26). Among months, capture efficiency ranged from 0.7% in August to 8.5% in May, with an overall average of 4.1 crows captured per 100 trap days. Although other capture methods (e.g., net launchers and Australian crow traps) have been used to capture crows in greater numbers, box traps can be an important complement to the other capture techniques because they are transportable, easy to use, relatively cheap, and easy to obtain.     

A comparison of food capture and ingestion in juveniles of two flatfish species, Pleuronectes platessa and Limanda limanda (Teleostei: Pleuronectiformes)

Juvenile plaice, Pleuronectes platessa ( n =6, 151–197 mm SL) and dab Limanda limanda ( n =6, 119–180.5 mm SL) feeding on pieces of mussel flesh were studied by high-speed (200 fields s⁻¹) videophotography at 11) C. Prey capture cycles (involving jaw protrusion and opercular expansion) were described in both species. The capture cycle was followed by at least one cycle (similar to the capture cycle in all respects except food intake) which is believed to transport food to the oesophagus. The transport cycle (or cycles) was followed by a species-specific number of normal respiratory cycles (7 or 8 in plaice, 11 or 12 in dab) and a final single cycle when food debris was violently ejected from the opercular cavity. The respiratory cycles and ejection cycle cleansed the orobranchial/opercular cavities and gills. Differences between the species were relatively minor, but plaice captured and transported food more quickly than dab.     

Netguns: a technique for capturing Black‐backed Woodpeckers

ABSTRACT Effective capture techniques are essential for studying bird populations, but commonly used techniques have proven ineffective for capturing Black‐backed Woodpeckers (Picoides arcticus) during the nonbreeding period. As a result, little is known about the winter ecology of Black‐backed Woodpeckers. We used two netguns, one powered with a 0.308 cartridge and another with CO₂ propellant, to capture 101 Black‐backed Woodpeckers (N= 75 initial captures and 26 recaptures) in the Black Hills of South Dakota from 2008 to 2011. Captures with the 0.308 netgun resulted in an impact mortality probability of 0.061 ± 0.034 (SE), whereas no impact mortalities were associated with the CO₂ netgun. We also tracked birds for 72 h post‐release, and determined a capture‐related mortality rate of 0.102 ± 0.04 with the 0.308 netgun and 0.038 ± 0.027 with the CO₂ netgun. With the CO₂ netgun, we captured woodpeckers in 31 of 43 net deployments (72%), with an average of 7.2 ± 0.4 h of capture effort for each bird. Many unsuccessful attempts were caused by tree branches that prevented net deployment. Netguns powered by CO₂ provide an effective capture technique that we recommend for studies of Black‐backed Woodpeckers and possibly other species of birds that forage low on trees.     

Improved methods for estimating abundance and related demographic parameters from mark‐resight data

Over the past decade, there has been much methodological development for the estimation of abundance and related demographic parameters using mark‐resight data. Often viewed as a less‐invasive and less‐expensive alternative to conventional mark recapture, mark‐resight methods jointly model marked individual encounters and counts of unmarked individuals, and recent extensions accommodate common challenges associated with imperfect detection. When these challenges include both individual detection heterogeneity and an unknown marked sample size, we demonstrate several deficiencies associated with the most widely used mark‐resight models currently implemented in the popular capture‐recapture freeware Program MARK. We propose a composite likelihood solution based on a zero‐inflated Poisson log‐normal model and find the performance of this new estimator to be superior in terms of bias and confidence interval coverage. Under Pollock's robust design, we also extend the models to accommodate individual‐level random effects across sampling occasions as a potentially more realistic alternative to models that assume independence. As a motivating example, we revisit a previous analysis of mark‐resight data for the New Zealand Robin (Petroica australis) and compare inferences from the proposed estimators. For the all‐too‐common situation where encounter rates are low, individual detection heterogeneity is non‐negligible, and the number of marked individuals is unknown, we recommend practitioners use the zero‐inflated Poisson log‐normal mark‐resight estimator as now implemented in Program MARK.     

An improved, simple nest-box trap

ABSTRACT.   The success of ornithological studies often hinges on a researcher's ability to capture individuals quickly and efficiently. Sometimes it is necessary to capture the same individual multiple times, as is the case in many metabolic, ecotoxicological, and immunocompetence studies. Several methods of capturing cavity-nesting birds at their nest boxes have been described. However, these methods proved inefficient when attempting to catch wary individuals that had already been captured previously. Here we describe a simple and inexpensive method for capturing cavity-nesting birds using a square plate of sheet metal (5.8 × 5.8 × 0.2 cm), a drinking straw, a piece of duct tape, and a monofilament line. This method has the advantages of allowing selective capture of one, but not both members of a pair and being nearly invisible to trap-shy birds.     

Field-Assessed Injury to Wolves Captured in Rubber-Padded Traps

Abstract: Minimizing and understanding the causes of capture-related injury should be a goal of every project that catches animals. We investigated the influence of age, weight, and sex on the field-assessed foot injury of 96 wolves (Canis lupus) captured in rubber-padded foothold traps. We then compared our results with those of 6 other types of wolf traps as reported in the literature. Injury from rubber-padded traps was lower than that of other traps, and age, weight, or sex did not influence foot damage. Rubber-padded foothold traps appear to be humane, and managers should consider their use for live capture of wolves.     

Strong nuclear differentiation contrasts with widespread sharing of plastid DNA haplotypes across taxa in European purple saxifrages (Saxifraga section Porphyrion subsection Oppositifoliae)

The purple saxifrages, Saxifraga section Porphyrion subsection Oppositifoliae, comprise the closest relatives of the arctic–alpine model plant S. oppositifolia and have a centre of diversity in the central and southern European mountain ranges. Many taxa have been described and taxonomic concepts vary among different treatments. Using amplified fragment length polymorphism (AFLP) fingerprinting, we show that some taxa form strongly supported genetic entities best recognized at the species level (S. biflora, S. blepharophylla, S. retusa, S. rudolphiana and S. speciosa), whereas others (S. murithiana and S. paradoxa) are not genetically divergent at all. Saxifraga oppositifolia s.s. is phylogenetically incoherent. Plastid DNA sequence data show limited congruence with the predominantly nuclear‐derived AFLPs. Several co‐distributed taxa (S. biflora, S. blepharophylla, S. oppositifolia s.s. and S. retusa) share the same set of haplotypes. In the widespread S. oppositifolia and S. retusa, highly divergent haplotype lineages were discovered which exhibit a geographical rather than taxonomic structure. Recent and ancient hybridization and/or lineage sorting are probably responsible for the strong incongruence between data derived from nuclear and plastid genomes. Hybridization, which is known to occur among almost all taxa of this group when growing in sympatry, however, seems to be insufficient to break down species barriers. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 622–636.     

结膜吸吮线虫中间宿主冈田氏绕眼果蝇的诱捕和鉴定

为大量采集和鉴定冈田氏绕眼果蝇,特将水果（苹果,梨等）切碎经发酵后,打成包并悬挂于树干,吸引果蝇进行诱捕或者置入蚊帐内诱捕,自1989-2000年9月经过数次现场实验,均可大量捕获冈田氏绕归果蝇,依据该种果蝇的形态结构和行为特征进行种的鉴定,尤其是雄外生殖器的特征和冈田氏绕眼果蝇腹部第3-5节的背面各有一似“山”形黑褐色斑纹及足的胫节上,有3个黑褐色环以及雄性生殖器的形态等可作为该种果蝇的外形特征。     

Kinematic analysis of over-determinate biomechanical systems

In this paper, we introduce a new general method for kinematic analysis of rigid multi body systems subject to holonomic constraints. The method extends the standard analysis of kinematically determinate rigid multi body systems to the over-determinate case. This is accomplished by introducing a constrained optimisation problem with the objective function given as a function of the set of system equations that are allowed to be violated while the remaining equations define the feasible set.

We show that exact velocity and acceleration analysis can also be performed by solving linear sets of equations, originating from differentiation of the Karush–Kuhn–Tucker optimality conditions.

The method is applied to the analysis of an 18 degrees-of-freedom gait model where the kinematical drivers are prescribed with data from a motion capture experiment.

The results show that significant differences are obtained between applying standard kinematic analysis or minimising the least-square errors on the two fully equivalent 3D gait models with only the way the experimental data is processed being different.     

MOSHFIT: Algorithms for occlusion-tolerant mean shape and rigid motion from 3D movement data

This work addresses the use of 3D point data to measure rigid motions, in the presence of occlusion and without reference to a prior model of relative point locations. This is a problem where cluster-based measurement techniques are used (e.g. for measuring limb movements) and no static calibration trial is available. The same problem arises when performing the task known as roving capture, in which a mobile 3D movement analysis system is moved through a volume with static markers in unknown locations and the ego-motion of the system is required in order to understand biomechanical activity in the environment. To provide a solution for both of these applications, the new concept of a visibility graph is introduced, and is combined with a generalised procrustes method adapted from ones used by the biological shape statistics and computer graphics communities. Recent results on shape space manifolds are applied to show sufficient conditions for convergence to unique solution. Algorithm source code is available and referenced here. Processing speed and rate of convergence are demonstrated using simulated data. Positional and angular accuracy are shown to be equivalent to approaches which require full calibration, to within a small fraction of input resolution. Typical processing times for sub-micron convergence are found to be fractions of a second, so the method is suitable for workflows where there may be time pressure such as in sports science and clinical analysis.     

Stress induced by hooking, net towing, elevated sea water temperature and air in sablefish: lack of concordance between mortality and physiological measures of stress

In a series of laboratory studies designed to simulate bycatch processes, sablefish Anoplopoma fimbria were either hooked for up to 24 h or towed in a net for 4 h and then subjected to an abrupt transfer to elevated sea water temperature and air. Mortality did not result from hooking or net towing followed by exposure to air, but increased for both capture methods as fish were exposed to elevated temperatures, reflecting the magnifying effect of elevated temperature on mortality. Hooking and exposure to air resulted in increased plasma cortisol and lactate concentrations, while the combination of hooking and exposure to elevated temperature and air resulted in increased lactate and potassium oncentrations. In fish that were towed in a net and exposed to air, cortisol, lactate, potassium and sodium concentrations increased, but when subjected to elevated temperature and air, no further increases occurred above the concentrations induced by net towing and air, suggesting a possible maximum of the physiological stress response. The results suggest that caution should be exercised when using physiological measures to quantify stress induced by capture and exposure to elevated temperature and air, that ultimately result in mortality, since the connections between physiological stress and mortality in bycatch processes remain to be fully understood.     

Effects of helicopter net-gunning on survival of bighorn sheep

Wildlife capture, and the data collection associated with it, has led to major advancements in ecology that are integral to decision making pertaining to wildlife conservation. Capturing wildlife, however, can cause lethal and non-lethal risks to animals. Understanding the factors that contribute to the level of risk involved in wildlife capture is therefore important for the development and implementation of the safest and most effective methodologies. We used data from 736 animal captures of 389 individuals for 2 subspecies of female bighorn sheep (Rocky Mountain bighorn [Ovis canadensis canadensis], Sierra Nevada bighorn sheep [O. c. sierrae]) in Wyoming and California, USA, in 2002–2020 to evaluate the degree and extent of time that capture via helicopter net-gunning affects survival. We compared pre- and post-capture survival during a 10-week window centered on a capture event, and post-capture survival between captured animals and animals that were monitored but not captured during the 10-week window. Additionally, we evaluated the effects of handling techniques (number of times captured, season of capture event, handling time, chase time, and body temp) and biological factors (age and nutritional condition) on probability of capture mortality. Mean daily survival was 0.9992 during a 5-week pre-capture window, dropped to 0.9864 on the day of capture, and rebounded within 3 days of capture to pre-capture levels and that of sheep that were not captured. Overall, direct mortality resulting from capture was 1.36%, with 0.54% mortality occurring within the 3 days following a capture event for an overall 1.90% capture-related mortality. The only handling and biological metrics that influenced the probability of capture mortality were rectal temperature and nutritional condition; high initial rectal temperatures and poor body condition were associated with increased risk of mortality in the days following capture. Overall, helicopter net-gunning imposed low and short-term risk to survival of female bighorn sheep. To reduce bias in survival estimates, we recommend using a 3-day censorship window for post-capture mortalities as opposed to the common practice of a 2–5-week censor window. Helicopter net-gunning, including annual or seasonal recaptures, remains an effective and comparatively safe technique for capture and associated data collection of bighorn sheep.     

Accuracy map of an optical motion capture system with 42 or 21 cameras in a large measurement volume

Optical motion capture is commonly used in biomechanics to measure human kinematics. However, no studies have yet examined the accuracy of optical motion capture in a large capture volume (>100 m³), or how accuracy varies from the center to the extreme edges of the capture volume. This study measured the dynamic 3D errors of an optical motion capture system composed of 42 OptiTrack Prime 41 cameras (capture volume of 135 m³) by comparing the motion of a single marker to the motion reported by a ThorLabs linear motion stage. After spline interpolating the data, it was found that 97% of the capture area had error below 200 μm. When the same analysis was performed using only half (21) of the cameras, 91% of the capture area was below 200 μm of error. The only locations that exceeded this threshold were at the extreme edges of the capture area, and no location had a mean error exceeding 1 mm. When measuring human kinematics with skin-mounted markers, uncertainty of marker placement relative to underlying skeletal features and soft tissue artifact produce errors that are orders of magnitude larger than the errors attributed to the camera system itself. Therefore, the accuracy of this OptiTrack optical motion capture system was found to be more than sufficient for measuring full-body human kinematics with skin-mounted markers in a large capture volume (>100 m³).     

Capture thread extensibility of orb-weaving spiders: testing punctuated and associative explanations of character evolution

Spider orb-webs contain sticky prey capture threads and non-sticky support threads. Primitive orb-weavers of the Deinopoidea produce dry cribellar threads made of thousands of silk fibrils that surround supporting axial fibres, whereas the viscous threads of modern Araneoidea orb-weavers produce adhesive threads with an aqueous solution that coalesces as droplets around the axial fibres. We have previously shown that the greater diversity of the Araneoidea is phylogenetically significant and attributed this disparity to a number of advantages, considered key innovations, that adhesive thread has over cribellar thread. An important putative advantage of adhesive thread demonstrated by Kohler and Vollrath in their 1995 study is its greater extensibility, a feature that better adapts it to absorb the kinetic energy of a prey strike. However, this conclusion is based on a two-species comparison that does not take advantage of the modern comparative method that requires hypotheses to be tested in a phylogenetic context. Using a transformational analysis to examine threads produced by nine species, our study finds no support for the punctuated explanation that adhesive thread has a greater extensibility than cribellar thread. Instead, it strongly supports the associative null hypothesis that capture thread extensibility is tuned to spider mass and to architectural features of the web, including its capture area, capture spiral spacing, and capture area per radius.