Impacts of Mesquite Distribution on Seasonal Space Use of Lesser Prairie-Chickens

Loss of native grasslands by anthropogenic disturbances has reduced availability and connectivity of habitat for many grassland species. A primary threat to contiguous grasslands is the encroachment of woody vegetation, which is spurred by disturbances that take on many forms from energy development, fire suppression, and grazing. These disturbances are exacerbated by natural- and human-driven cycles of changes in climate punctuated by drought and desertification conditions. Encroachment of honey mesquite (Prosopis glandulosa) into the prairies of southeastern New Mexico has potentially limited habitat for numerous grassland species, including lesser prairie-chickens (Tympanuchus pallidicinctus). To determine the magnitude of impacts of distribution of mesquite and how lesser prairie-chickens respond to mesquite presence on the landscape in southeastern New Mexico, we evaluated seasonal space use of lesser prairie-chickens in the breeding and nonbreeding seasons. We derived several remotely sensed spatial metrics to characterize the distribution of mesquite. We then used these data to create population-level resource utilization functions and predict intensity of use of lesser prairie-chickens across our study area. Home ranges were smaller in the breeding season compared with the nonbreeding season; however, habitat use was similar across seasons. During both seasons, lesser prairie-chickens used areas closer to leks and largely avoided areas with mesquite. Relative to the breeding season, during the nonbreeding season habitat use suggested a marginal increase in mesquite within areas of low intensity of use, yet aversion to mesquite was strong in areas of medium to high intensity of use. To our knowledge, our study is the first to demonstrate a negative behavioral response by lesser prairie-chickens to woody encroachment in native grasslands. To mitigate one of the possible limiting factors for lesser prairie-chickens, we suggest future conservation strategies be employed by land managers to reduce mesquite abundance in the southern portion of their current range.     

Unintended consequences of climate-adaptive fisheries management targets

Climate change is projected to affect the productivity of global fisheries. Management based on maximum sustainable yield (MSY) has been effective at eliminating overfishing in many regions. However, continuing to use yield-maximizing targets under climate-driven changes in productivity can result in higher anthropogenic pressure on populations subject to climate-related stress than maintaining status quo management targets. We demonstrate this effect using a theoretical example and case studies from snow crab in the eastern Bering Sea and a global marine fisheries database. In these examples, the conservation gain (i.e. biomass in the ocean) of maintaining status quo management targets is larger than the small gain in harvest made through climate adaptation in MSY-based management. The aggregate conservation gain of maintaining management targets increases as the harmful impacts of climate change on productivity worsen. Instead of climate-adaptive MSY-based targets, new management tools are needed to balance conservation and food production in ecosystems of populations displaying non-stationary productivity.     

The efficacy of monepantel against naturally acquired inhibited and developing fourth-stage larvae of Teladorsagia circumcincta in sheep in the United Kingdom

The inhibition of Teladorsagia and other nematode genera at the early fourth-stage is a biological process that allows the parasites to survive in their host in a dormant state when prevailing conditions may otherwise kill them or prevent their progeny from surviving in the external environment. A study was conducted in Scotland to evaluate the efficacy of monepantel, an amino-acetonitrile derivative, against natural infections of inhibited fourth-stage Teladorsagia spp. larvae. At necropsy it was determined that the untreated control sheep were additionally infected with developing fourth-stage Teladorsagia spp. larvae and this is the first published evidence on the efficacy of monepantel against natural infections of this parasite and stage. The study sheep, which had grazed on naturally contaminated pastures since birth, were transferred to indoor housing after a subset of animals was examined to confirm the presence of inhibited larvae within the study population prior to the experiment. After 14 days of housing, monepantel was orally administered at 2.5 mg/kg to half of the animals. The sheep were necropsied seven days later and their parasite burdens recovered for the determination of efficacy, which was 99.7% for the inhibited stages and 99.3% for the developing fourth-stages. In conclusion, monepantel dosed orally at 2.5 mg/kg is a highly effective treatment against naturally acquired infections of inhibited and developing fourth-stage larvae of Teladorsagia spp.     

Comparative effects of milbemycin oxime-based and febantel-pyrantel embonate-based anthelmintic tablets on Toxocara canis egg shedding in naturally infected pups

The effect of two treatment programmes on egg shedding in dogs naturally infected with Toxocara canis, one based on a milbemycin oxime-praziquantel-lufenuron combination (SENTINEL) Spectrum; Group 1) and the other based on a febantel-pyrantel embonate-praziquantel combination (DRONTAL) Plus; Group 2), was compared in a study involving 104 suckling pups from three different kennels. The animals in Group 1 were treated at a minimum milbemycin oxime dose of 0.5 mg/kg bw starting at 2 weeks of age and subsequently every 4 weeks until reaching 26 weeks of age. The animals in Group 2 were treated every 2 weeks from week 2 until week 12 of age and then once at week 26 at a minimum febantel and pyrantel embonate dose of 15.0 and 14.4 mg/kg bw, respectively. Toxocara egg counts were determined fortnightly starting at 2 weeks of age and continuing until 26 weeks of age for every pup. Any adverse drug event was recorded during the trial. Both treatment programmes significantly reduced the zoonotic Toxocara egg shedding and were well tolerated by the pups. The pups in Group 1 showed lower average faecal egg counts and were found more frequently shedding no eggs than the pups in Group 2.     

Syringohydromyelia in horses: 3 cases

Syringomyelia and hydromyelia are cavitary lesions of the spinal cord that may be acquired or congenital. These lesions are not frequently reported in large animal species. The presenting complaints, clinical, gross pathological, and histopathologic findings of 2 cases of syringomyelia and 1 case of hydromyelia in horses are described.     

A novel spatiotemporal stock assessment framework to better address fine‐scale species distributions: Development and simulation testing

Characterizing population distribution and abundance over space and time is central to population ecology and conservation of natural populations. However, species distribution models and population dynamic models have rarely been integrated into a single modelling framework. Consequently, fine‐scale spatial heterogeneity is often ignored in resource assessments. We develop and test a novel spatiotemporal assessment framework to better address fine‐scale spatial heterogeneities based on theories of fish population dynamic and spatiotemporal statistics. The spatiotemporal model links species distribution and population dynamic models within a single statistical framework that is flexible enough to permit inference for each state variable through space and time. We illustrate the model with a simulation–estimation experiment tailored to two exploited marine species: snow crab (Chionoecetes opilio, Oregoniidae) in the Eastern Bering Sea and northern shrimp (Pandalus borealis, Pandalidae) in the Gulf of Maine. These two species have different types of life history. We compare the spatiotemporal model with a spatially aggregated model and systematically evaluate the spatiotemporal model based on simulation experiments. We show that the spatiotemporal model can recover spatial patterns in population and exploitation pressure as well as provide unbiased estimates of spatially aggregated population quantities. The spatiotemporal model also implicitly accounts for individual movement rates and can outperform spatially aggregated models by accounting for time‐and‐size varying selectivity caused by spatial heterogeneity. We conclude that spatiotemporal modelling framework is a feasible and promising approach to address the spatial structure of natural resource populations, which is a major challenge in understanding population dynamics and conducting resource assessments and management.     

Induction of lateral branches in tree fruit nursery stock with propyl 3-t-butylphenoxy acetate (MB 25, 105) and Promalin (GA4+7 + 6-benzyladenine)

Sprays with 250–2000 mg l^?1 propyl 3-t-butylphenoxy acetate (MB 25,105) and 250 and 500 mg l^?1 GA₄₊₇ + 6-benzyladenine (Promalin) were applied to scion growth of first nursery trees of ‘Bartlett’ pear (Pyrus communis L.), ‘Bing’ cherry (Prunus avium L.) and ‘Oregon Spur II Delicious’ apple (Malus domestica Borkh.) to stimulate lateral branching in the nursery. Most treatments significantly increased branching compared to untreated controls. Combination sprays of the two chemicals were usually better than either used alone. Chemical treatment usually produced greater branching and wider branch angles than mechanical heading. Both chemical and mechanical treatments reduced tree height and caliper, but the decrease was not always statistically significant.