The Combined Effects of Warming and Body Size on the Stability of Predator-Prey Interactions

Environmental temperature and body size are two prominent drivers of predation. Despite the ample evidence of their independent effects, the combined impact of temperature and predator-prey body size ratio on the strength and stability of trophic interactions is not fully understood. We experimentally tested how water temperature alters the functional response and population stability of dragonfly nymphs (Cordulegaster boltonii) feeding on freshwater amphipods (Gammarus pulex) across a gradient of their body size ratios. Attack coefficients were highest for small predators feeding on small prey at low temperatures, but shifted toward the largest predators feeding on larger prey in warmer environments. Handling time appeared to decrease with increasing predator and prey body size in the cold environment, but increase at higher temperatures. These findings indicate interactive effects of temperature and body size on functional responses. There was also a negative effect of warming on the stability of predator and prey populations, but this was counteracted by a larger predator-prey body size ratio at higher temperatures. Here, a greater Hill exponent reduced feeding at low prey densities when predators were much larger than their prey, enhancing the persistence of both predator and prey populations in the warmer environment. These experimental findings provide new mechanistic insights into the destabilizing effect of warming on trophic interactions and the key role of predator-prey body size ratios in mitigating these effects.

A seasonal pulse of ungulate neonates influences space use by carnivores in a multi-predator, multi-prey system

The behavioral mechanisms by which predators encounter prey are poorly resolved. In particular, the extent to which predators engage in active search for prey versus incidentally encountering them is unknown. The distinction between search and incidental encounter influences prey population dynamics with active search exerting a stabilizing force on prey populations by alleviating predation pressure on low-density prey and increasing it for high26 density prey. Parturition of many large herbivores occurs during a short and predictable temporal window in which young are highly vulnerable to predation. Our study aims to determine how a suite of carnivores responds to the seasonal pulse of newborn ungulates using contemporaneous GPS locations of four species of predators and two species of prey. We used step-selection functions to assess whether coyotes, cougars, black bears, and bobcats actively searched for parturient females in a low-density population of mule deer and a high-density population of elk. We then assessed whether searching carnivores shifted their habitat use toward areas exhibiting a high probability of encountering neonates. None of the four carnivore species encountered parturient mule deer more often than expected by chance suggesting that predation of young resulted from incidental encounters. By contrast, we determined that cougar and male bear movements positioned them in proximity of parturient elk more often than expected by chance which is evidence of searching behavior. Although both male bears and cougars searched for neonates, only male bears used elk parturition habitat in a way that dynamically tracked the phenology of the elk birth pulse suggesting that maximizing encounters with juvenile elk was a motivation when selecting resources. Our results support the existence of a stabilizing mechanism to prey populations through active search behavior by predators because carnivores in our study searched for the high45 density prey species (elk) but ignored the low-density species (mule deer). We conclude that prey density must be high enough to warrant active search, and that there is high interspecific and intersexual variability in foraging strategies among large mammalian predators and their prey.

Human Wildlife Conflict and Impacts on Livelihood: A Study in Community Forestry System in Mid-Hills of Nepal

Human wildlife conflict (HWC) impacts the livelihood of many rural communities worldwide. This study investigated the impact of HWC on people living near community forests (CF) in Nepal. Using databases provided by the Division of Forest Offices and data obtained from surveys between October 2019–March 2020, we quantified the financial loss of HWC to the local people. Between 2015 and 2019, 3315, or 27%, of the livestock owned by the survey respondents were killed by wild predators in the Kaski and Tanahun Districts. Chicken (Gallus spp.) was the most common prey taken (80%), followed by sheep (Ovis spp.) and goats (Capra spp.) (15%), cows (Bos spp.) (2%), pigs (Sus spp.) (2%), and buffalo (Bubalus spp.) (1%). Leopards (Panthera pardus) were the primary predators, followed by golden jackals (Canis aureus), jungle cats (Felis chaus), yellow-throated martens (Martes flavigula), and Himalayan black bears (Ursus thibetanus). The financial loss of livestock during this period was USD $115,656.00, equivalent to USD $142.61 per household. Crops were also damaged and eaten by wildlife, and 2165 crop-raiding events were recorded between 2015 and 2019. Rice (Oryza sativa), followed by maize (Zea mays), millet (Panicum miliaceum), and potatoes (Solanum tuberosum) were the main crops lost. Rhesus monkeys (Macaca mulatta) were the most common crop raiders, causing 74% of the damage, followed by Indian field mice (Mus booduga) (12%). From 2015 to 2019, crop losses equated to USD $83,424.00. Forest regeneration on abandoned agricultural land expanded wildlife habitats, enabling wild animals to come within reach of human settlements, which increased the likelihood of HWC events. Although the success of the community forest restoration program resulted in increased forest-cover, marginally increasing biodiversity, the reduced distance between human settlements and wildlife habitat, compounded by a lack of natural prey, may have unwittingly exacerbated HWC in this region. We recommend surveying predator and prey populations in the forest habitat, and implementing a habitat management program to improve prey populations within the community forests. Meantime, we propose establishing a financial relief and insurance program for crop and livestock losses at the local community level to alleviate any financial difficulties to the local communities caused by HWC.

Stability analysis of two predators and one prey population model with harvesting in fisheries management

The discussion is focussed in the interaction between two predators and one prey population model in fishery management. Mathematically model is built by involving harvesting with constant efforts in the two predators and one prey populations. The positive equilibrium point of the model is analyzed via linearization and Routh-Hurwitz stability criteria. From the analysis, there exists a certain condition that makes the positive equilibrium point is asymptotically stable. The stable equilibrium point is then related to the maximum profit problem. With suitable value of harvesting efforts, the maximum profit is reached and the predator and prey populations remain stable. Finally, a numerical simulation is carried out to find out how much the maximum profit is obtained and to visualize how the trajectories of predator and prey tend to the stable equilibrium point.

Predatory Bacteria Select for Sustained Prey Diversity

Predator impacts on prey diversity are often studied among higher organisms over short periods, but microbial predator-prey systems allow examination of prey-diversity dynamics over evolutionary timescales. We previously showed that Escherichia coli commonly evolved minority mucoid phenotypes in response to predation by the bacterial predator Myxococcus xanthus by one time point of a coevolution experiment now named MyxoEE-6. Here we examine mucoid frequencies across several MyxoEE-6 timepoints to discriminate between the hypotheses that mucoids were increasing to fixation, stabilizing around equilibrium frequencies, or heading to loss toward the end of MyxoEE-6. In four focal coevolved prey populations, mucoids rose rapidly early in the experiment and then fluctuated within detectable minority frequency ranges through the end of MyxoEE-6, generating frequency dynamics suggestive of negative frequency-dependent selection. However, a competition experiment between mucoid and non-mucoid clones found a predation-specific advantage of the mucoid clone that was insensitive to frequency over the examined range, leaving the mechanism that maintains minority mucoidy unresolved. The advantage of mucoidy under predation was found to be associated with reduced population size after growth (productivity) in the absence of predators, suggesting a tradeoff between productivity and resistance to predation that we hypothesize may reverse mucoid vs non-mucoid fitness ranks within each MyxoEE-6 cycle. We also found that mucoidy was associated with diverse colony phenotypes and diverse candidate mutations primarily localized in the exopolysaccharide operon yjbEFGH. Collectively, our results show that selection from predatory bacteria can generate apparently stable sympatric phenotypic polymorphisms within coevolving prey populations and also allopatric diversity across populations by selecting for diverse mutations and colony phenotypes associated with mucoidy. More broadly, our results suggest that myxobacterial predation increases long-term diversity within natural microbial communities.

Community and single cell analyses reveal complex predatory interactions between bacteria in high diversity systems

A fundamental question in community ecology is the role of predator–prey interactions in food-web stability and species coexistence. Although microbial microcosms offer powerful systems to investigate it, interrogating the environment is much more arduous. Here, we show in a 1-year survey that the obligate predators Bdellovibrio and like organisms (BALOs) can regulate prey populations, possibly in a density-dependent manner, in the naturally complex, species-rich environments of wastewater treatment plants. Abundant as well as rarer prey populations are affected, leading to an oscillating predatory landscape shifting at various temporal scales in which the total population remains stable. Shifts, along with differential prey range, explain co-existence of the numerous predators through niche partitioning. We validate these sequence-based findings using single-cell sorting combined with fluorescent hybridization and community sequencing. Our approach should be applicable for deciphering community interactions in other systems.

Stability Analysis and Harvesting Effort Predator Prey Populations Model Holling Type III with Maximum Profit

In this paper discussed stability analysis and harvesting effort at second predator prey populations model Holling type III with maximum profit. The step this research is to determine the equilibrium point, linearize the model, stability analysis of the equilibrium point, and numerical simulation. Result shows that obtained an interior point T𝐸2∗(𝑁1∗,𝑁2∗) that asymptotic stable based on Hurwitz stability test then obtained maximum profit from exploitation harvesting effort of second predator prey populations. This second populations will always exist, even though exploited with harvesting effort done by humans. Harvesting effort of second predator-prey populations given maximum profit (𝜋𝑚𝑎𝑥) that occur on critical points of surface profit function