Physiological responses of Populus przewalskii to oxidative burst caused by drought stress

We measured dry matter accumulation and allocation to the roots, leaf gas exchange, chlorophyll fluorescence, antioxidant enzymes, and ABA and polyamine (PA) contents in Populus przewalskii under three different watering regimes (100, 50, and 25% of the field capacity) to investigate the morphological and physiological responses to water deficit in woody plants. The results showed that drought stress retarded P. przewalskii as evident from a decreased biomass accumulation and the reduced increment of shoot height and basal diameter. Drought stress also affected the biomass partition by higher biomass allocated to the root systems for water uptake. The contents of ABA and PAs especially were increased under stressful conditions. Drought stress caused oxidative burst indicated by the accumulation of peroxide (H₂O₂), and fluorimetric detection also confirmed the increased accumulation of H₂O₂. The antioxidant enzymes, including superoxide dimutase, peroxidase, ascorbate peroxidase, and reductase, were activated to bring the reactive oxygen species to their homeostasis; however, oxidative damages to lipids, proteins, and membranes were significantly manifested by the increase in total carbonyl (C=O) and electric conductance (EC).     

Male infanticide and paternity analyses in a socially natural herd of Przewalski's horses: Sexual selection?

The sexual selection hypothesis explains infanticide by males in many mammals. In our 11-year study, we investigated this hypothesis in a herd of Przewalski's horses where we had witnessed infanticidal attacks. Infanticide was highly conditional and not simply linked to takeovers. Attacks occurred in only five of 39 cases following a takeover, and DNA paternity revealed that, although infanticidal stallions were not the genetic fathers in four cases out of five, stallions present at birth did not significantly attempt to kill unrelated foals. Infanticide did not reduce birth intervals; only in one case out of five was the infanticidal stallion, the father of the next foal; mothers whose foals were attacked subsequently avoided associating with infanticidal stallions. Therefore, evidence for the sexual selection hypothesis was weak. The “human disturbance” hypothesis received some support, as only zoo bred stallions which grew up in unnatural social groups attacked foals of mares which were pregnant during takeovers.     

Dietary Overlap of Przewalski's Gazelle,Tibetan Gazelle,and Tibetan Sheep on the Qinghai-Tibet Plateau

Abstract: We studied food composition and overlap among sympatric Przewalski's gazelle (Procapra przewalskii), Tibetan gazelle (P. picticaudata), and Tibetan domestic sheep (Ovis aries) in the Upper Buha River, Qinghai-Tibet Plateau, using microscopic fecal analysis. The 2 gazelles forage mainly on plants from Leguminosae and Compositae families and domestic sheep feed mainly on Gramineae and Cyperaceae. The dietary overlap index between the 2 gazelles and Tibetan domestic sheep increased from 0.43 to 0.58 during the plant-growing period to 0.76–0.77 during the plant-withering period, which indicated competition for foods intensified during the food-limited season. Although the 2 gazelle ate similar diets, they might avoid food competition by occupying different foraging areas. We suggest reducing numbers of overwintering Tibetan domestic sheep on pastures to lessen survival pressure on the endangered gazelles during winters.     

不同生境下青海湖裸鲤(Gymnocypris przewalskii)两亚种鳃形态差异及其功能适应

该研究比较观察青海湖裸鲤(Gymnocypris przewalskii)两亚种(青海湖裸鲤指名亚种(Gymnocypris przewalskii przewalskii)和青海湖裸鲤甘子河亚种(Gymnocypris przewalskii ganzihonensis))鳃的形态及显微结构。结果显示,指名亚种的第一鳃弓鳃耙数多、密集且较长,而甘子河亚种则耙数少、稀疏且短;两者的鳃丝间距及鳃小片间距无明显差异,指名亚种的鳃丝较长;指名亚种扁平上皮细胞形态以不规则椭圆形为主,鳃丝表面有黏液细胞,其上分布的氯细胞数量多于甘子河亚种,而甘子河亚种扁平上皮细胞的形态以六边形为主,鳃丝表皮未观察到黏液细胞。由此推测,青海湖裸鲤两亚种鳃形态的差异与其食性和栖息环境相适应。     

Sexual Dimorphism of Head Size in Phrynocephalus przewalskii: Testing the Food Niche Divergence Hypothesis

Sexual size dimorphism （SSD） is a general phenomenon in lizards, and can evolve through sexual selection or natural selection. But natural selection, which was thought to operate mainly through reducing the competition be- tween the two sexes （niche divergence hypothesis）, gave rise to a lot of controversy. We tested the niche divergence hypothesis in the toad-headed lizard Phrynocephalus przewalskii by comparing diet composition and prey sizes between males and females. The species was found to be sexual dimorphic, with males having relatively larger snout-vent length, head width, head length, and tail length, while females have relatively larger abdomen length. Based on analysis of 93 studied stomachs, a total of 1359 prey items were identified. The most common prey items were formicid, lygaeid and tenebrionid. The two sexes did not differ in the relative proportions of prey size categories they consumed and the dietary overlap based on prey species was high （O = 0.989）. In addition, the meal size, the volume or any maximal dimension of the largest prey item in the stomach was not explained by the sexes. According to our results, food niche divergence might not play an important role in the SSD evolution ofP. przewalskii.     

Feral Horse Population Model and Body Condition: Useful Management Tools in Tornquist Park,Argentina?

Feral invasive mammals challenge management strategies worldwide including the feral horse (Equus caballus) population in Tornquist Park, Argentina. In this study, I constructed population matrix models using demography data collected between 1995 and 2002. I validated the models with independent counts from 2008 to 2016. I individually identified feral horses and recorded them as I walked a fixed path that covered 20 km². I performed an elasticity analysis to estimate the influence of the demographic parameters on population growth rate. In addition, I explored whether body condition score could be a proxy for carrying capacity. Model projections with the highest values of fecundity and survival exhibited by females of all ages during 1995–2002 fit the counts from 2008 to 2016, when growth rate was moderate (λ = 1.10), very well. Elasticity of adult female survival (0.54) was 4 times higher than for fecundity and survival of all other ages. Body condition of adult females at the end of winter, 2012–2013, after reductions in density, was improved compared with 2001–2002 when the population approached carrying capacity. The validated population model together with body condition score could allow managers to take more informed decisions when planning the control of feral horses in Tornquist Park. This approach could also be applied to other small, closed, feral horse populations and other large-mammal populations. © 2020 The Wildlife Society.     

Ecological Interactions Involving Feral Horses and Predators: Review with Implications for Biodiversity Conservation

For many ecosystems, feral horses are increasingly becoming an important if not dominant component of ungulate biomass and hence influence on community dynamics. Yet we still know little of how horses contribute to key ecological interactions including predator-prey and indirect competitive relationships at a community level. Notably, feral species like horses can exhibit life-history traits that differ from that of native (mainly artiodactyl) herbivore competitors. Artificial selection for traits like increased, early, or extended reproduction that have yet to be reversed by natural selection, coupled with naturally selected differences in anatomy and behavior, in addition to unique management objectives for horses compared to other species, means that the dynamics of feral horse populations are not likely to align with what might be expected of other large herbivores. Unexpected population dynamics and inherent biological asymmetries between native ungulates and feral horses may therefore influence the former via direct competition for shared resources and through enemy-mediated interactions like apparent competition. In several localities feral horses now co-exist with multiple native prey species, some of which are in decline or are species at risk. Compounding risks to native species from direct or indirect competitive exclusion by horses is the unique nature and socio-political context of feral horse management, which tends towards allowing horse populations to be limited largely by natural, density-dependent factors. We summarize the inherent asymmetries between feral horse biology and that of other ungulate prey species with consequences for conservation, focusing on predator-prey and emerging indirect interactions in multi-prey systems, and highlight future directions to address key knowledge gaps in our understanding of how feral horses may now be contributing to the (re)structuring of food webs. Observations of patterns of rapid growth and decline, and associated skews in sex ratios of feral horse populations, indicate a heightened potential for indirect interactions among large ungulate prey species, where there is a prevalence of feral horses as preferred prey, particularly where native prey are declining. In places like western North America, we expect predator-prey interactions involving feral horses to become an increasingly important factor in the conservation of wildlife. This applies not only to economically or culturally important game species but also at-risk species, both predators (e.g., wolves [Canis lupus], grizzly bears [Ursus arctos]) and prey (e.g., woodland caribou [Rangifer tarandus caribou]), necessitating an ecological understanding of the role of horses in natural environments that goes beyond that of population control. © 2021 The Wildlife Society.     

Sage-Grouse Population Dynamics are Adversely Affected by Overabundant Feral Horses

In recent decades, feral horse (Equus caballus; horse) populations increased in sagebrush (Artimesia spp.) ecosystems, especially within the Great Basin, to the point of exceeding maximum appropriate management levels (AML_max), which were set by land administrators to balance resource use by feral horses, livestock, and wildlife. Concomitantly, greater sage-grouse (Centrocercus urophasianus; sage-grouse) are sagebrush obligates that have experienced population declines within these same arid environments as a result of steady and continued loss of seasonal habitats. Although a strong body of research indicates that overabundant populations of horses degrade sagebrush ecosystems, empirical evidence linking horse abundance to sage-grouse population dynamics is missing. Within a Bayesian framework, we employed state-space models to estimate population rate of change (λ) using 15 years (2005–2019) of count surveys of male sage-grouse at traditional breeding grounds (i.e., leks) as a function of horse abundance relative to AML_max and other environmental covariates (e.g., wildfire, precipitation, % sagebrush cover). Additionally, we employed a post hoc impact-control design to validate existing AML_max values as related to sage-grouse population responses, and to help control for environmental stochasticity and broad-scale oscillations in sage-grouse abundance. On average, for every 50% increase in horse abundance over AML_max, our model predicted an annual decline in sage-grouse abundance by 2.6%. Horse abundance at or below AML_max coincided with sage-grouse λ estimates that were consistent with trends at non-horse areas elsewhere in the study region. Thus, AML_max, as a whole, appeared to be set adequately in preventing adverse effects to sage-grouse populations. Results indicated 76%, 97%, and >99% probability of sage-grouse population decline relative to controls when horse numbers are 2, 2.5, and ≥3 times over AML_max, respectively. As of 2019, horse herds exceeded AML_max in Nevada, USA, by >4 times on average across all horse management areas. If feral horse populations continue to grow at current rates unabated, model projections indicate sage-grouse populations will be reduced within horse-occupied areas by >70.0% by 2034 (15-year projection), on average compared to 21.2% estimated for control sites. A monitoring framework that improves on estimating horse abundance and identifying responses of sage-grouse and other key indicator species (plant and animal) would be beneficial to guide management decisions that promote co-occurrence of horses with sensitive wildlife and livestock within landscapes subjected to multiple uses. Published 2021. This article is a U.S. Government work and is in the public domain in the USA. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

Science and Knowledge of Free-Roaming Donkeys—A Critical Review

The emergence of free-roaming donkey (Equus asinus) populations globally has brought novel challenges for conservationists, land managers, and those concerned about animal welfare. We provide a review of the scientific literature pertaining to the place and role of free-roaming donkeys from 1950 until 2020. Using quantitative and qualitative techniques, namely categorical and thematic analysis and critical discourse analysis, to review >100 articles, we critically examine the logics and rationales that are used to either support or denounce donkey presence in particular landscapes and discuss their place and role in different ecological contexts. Free-roaming donkeys are largely understudied and clouded by dichotomous points of view, different conservation agendas, and the presence of other species in donkey habitat. There is an important need for more in-depth, site-specific studies on free-roaming donkeys that draw on tools and techniques from across the social and natural sciences. Such efforts would offer a richer, more holistic, and comprehensive picture of free-roaming donkeys that consider both human and animal perspectives and the wider environment. This has important implications for generating long-term sustainable management solutions for free-roaming donkeys. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.