Squirrel Control Research Articles

An Intelligent Optimized Control System for Induction Heating Application

In the modern era, induction heating (IH) technology is utilized for industrial functions like medical applications and domestic applications. Furthermore, efficient uses such as control topologies, magnetic component design, and power electronics have high demand as well as cost-effective with respect to advanced technology. However, IH technology directly targets the power converter and coil so it has wasted higher amount of heat. Also, high power dissipation in an IH system leads to high energy costs and reduced system performance. Hence, various approaches are developed to minimize power dissipation. However, they cannot reduce power dissipation in the induction coil. Thus, a novel Decision-based Squirrel Control System was developed in this article to decrease the power wastage in induction coil optimally. The developed model’s squirrel fitness function monitors power wastage and compensates them by tuning it. The developed model is executed in MATLAB/Simulink, and the results are determined. In terms of rising time, settling time, overshoot, and error rate. Here, the proposed work can achieve 0.075s resting time, 1.02s settling time, 0.05s overshoot, and 0.29% of error rate. The comparative assessment proves that the presented approach attained better results than others.

A camera trap method for estimating target densities of grey squirrels to inform wildlife management applications

Effective wildlife population management requires an understanding of the abundance of the target species. In the United Kingdom, the increase in numbers and range of the non-native invasive grey squirrel Sciurus carolinensis poses a substantial threat to the existence of the native red squirrel S. vulgaris, to tree health, and to the forestry industry. Reducing the number of grey squirrels, is crucial to mitigate their impacts. Camera traps are increasingly used to estimate animal abundance, and methods have been developed that do not require the identification of individual animals. Most of these methods have been focussed on medium to large mammal species with large range sizes and may be unsuitable for measuring local abundances of smaller mammals that have variable detection rates and hard to measure movement behaviour. The aim of this study was to develop a practical and cost-effective method, based on a camera trap index, that could be used by practitioners to estimate target densities of grey squirrels in woodlands to provide guidance on the numbers of traps or contraceptive feeders required for local grey squirrel control. Camera traps were deployed in ten independent woods of between 6 and 28 ha in size. An index, calculated from the number of grey squirrel photographs recorded per camera per day had a strong linear relationship (R2 = 0.90) with the densities of squirrels removed in trap and dispatch operations. From different time filters tested, a 5 min filter was applied, where photographs of squirrels recorded on the same camera within 5 min of a previous photograph were not counted. There were no significant differences between the number of squirrel photographs per camera recorded by three different models of camera, increasing the method’s practical application. This study demonstrated that a camera index could be used to inform the number of feeders or traps required for grey squirrel management through culling or contraception. Results could be obtained within 6 days without requiring expensive equipment or a high level of technical input. This method can easily be adapted to other rodent or small mammal species, making it widely applicable to other wildlife management interventions.

Interactions between native and invasive species: A systematic review of the red squirrel-gray squirrel paradigm

The eastern gray squirrel (Sciurus carolinensis) has been labeled as one of the 100 worst invasive alien species by the IUCN. In Europe, the species has been introduced to Britain, Ireland and Italy, and its subsequent spread has resulted in wide-scale extinction of native Eurasian red squirrels (Sciurus vulgaris) from the areas colonized by the gray squirrel. This replacement of a native by an alien competitor is one of the best documented cases of the devastating effects of biological invasions on native fauna. To understand how this replacement occurs, we present a systematic review of the literature on competition and interactions between red and gray squirrels. We describe the patterns of red and gray squirrel distribution in those parts of Europe where gray squirrels occur and summarize the evidence on the different processes and mechanisms determining the outcome of competition between the native and alien species including the influence of predators and pathogens. Some of the drivers behind the demise of the red squirrel have been intensively studied and documented in the past 30 years, but recent field studies and mathematical models revealed that the mechanisms underlying the red-gray paradigm are more complex than previously thought and affected by landscape-level processes. Therefore, we consider habitat type and multi-species interactions, including host-parasite and predator-prey relationships, to determine the outcome of the interaction between the two species and to better address gray squirrel control efforts.

On the dynamics and control of a squirrel locking its head/eyes toward a fixed spot for safe landing while its body is tumbling in air.

An arboreal mammal such as a squirrel can amazingly lock its head (and thus eyes) toward a fixed spot for safe landing while its body is tumbling in air after unexpectedly being thrown into air. Such an impressive ability of body motion control of squirrels has been shown in a recent YouTube video, which has amazed public with over 100 million views. In the video, a squirrel attracted to food crawled onto an ejection device and was unknowingly ejected into air by the device. During the resulting projectile flight, the squirrel managed to quickly turn its head (eyes) toward and then keeps staring at the landing spot until it safely landed on feet. Understanding the underline dynamics and how the squirrel does this behavior can inspire robotics researchers to develop bio-inspired control strategies for challenging robotic operations such as hopping/jumping robots operating in an unstructured environment. To study this problem, we implemented a 2D multibody dynamics model, which simulated the dynamic motion behavior of the main body segments of a squirrel in a vertical motion plane. The inevitable physical contact between the body segments is also modeled and simulated. Then, we introduced two motion control methods aiming at locking the body representing the head of the squirrel toward a globally fixed spot while the other body segments of the squirrel were undergoing a general 2D rotation and translation. One of the control methods is a conventional proportional-derivative (PD) controller, and the other is a reinforcement learning (RL)-based controller. Our simulation-based experiment shows that both controllers can achieve the intended control goal, quickly turning and then locking the head toward a globally fixed spot under any feasible initial motion conditions. In comparison, the RL-based method is more robust against random noise in sensor data and also more robust under unexpected initial conditions.

Estimating Reduction in Standing Crop Biomass from California Ground Squirrels in Central California Rangelands

California ground squirrels (Otospermophilus spp.) cause more economic damage to California rangelands than any other rodent. Damage comes in many forms, although forage loss is typically the greatest concern. These losses are believed to be significant for ranchers, particularly given the economically marginal environment in which they exist, yet our understanding of these economic losses is limited. Furthermore, current public opinion is often not supportive toward ground squirrel control on many public grazing lands. Information on the damage that ground squirrels cause to rangelands may be needed to justify management actions in the future. Therefore, we evaluated the amount of standing crop removed by California ground squirrels across 16 sites at four different ground squirrel density categories in central California rangelands from 2019 through 2020. We also included precipitation and livestock grazing intensity to help account for their potential effect on forage production. We found that ground squirrel abundance negatively affected standing crop biomass, with available forage reduced by 27.2 kg ha−1 per individual ground squirrel at the end of the growing season. Likewise, precipitation influenced standing crop, with each cm of precipitation yielding a 16.6 kg ha−1 increase in available forage. We did not observe any effect of livestock grazing intensity, an interaction between livestock grazing intensity and ground squirrel abundance, or an interaction between precipitation and ground squirrel abundance on residual standing crop. Collectively, this information will be useful to ranchers to help determine when control efforts may be needed for California ground squirrels given relative abundance of ground squirrels on their rangeland properties.

Natural strongholds for red squirrel conservation in Scotland

The Eurasian Red Squirrel (Sciurus vulgaris) is under threat from the invasive North American eastern Grey Squirrel (Sciurus carolinensis) with 80% of the remaining red squirrel populations in the British Isles found in Scotland. In this study we develop a spatially explicit mathematical model of the red and grey squirrel system and use it to assess the population viability of red squirrels across Scotland. In particular, we aim to identify existing forests – natural strongholds for red squirrels – that can successfully support red squirrels under UK Forestry Standard management and protect them from potential disease-mediated competition from grey squirrels. Our model results indicate that if current levels of grey squirrel control, which restrict or reduce the distribution of grey squirrels, are continued then there will be large expanses of forests in northern Scotland that support viable red squirrel populations. Model results that represent (hypothetical) scenarios where grey squirrel control no longer occurred indicated that grey squirrel range expansion and the process of red squirrel replacement would be slow. Model results for an assumed worst-case scenario where grey squirrels have expanded to all regions in Scotland identified forest regions – denoted natural strongholds – that could currently support red squirrels under UK Forestry Standard management practice. The results will be used to inform forest management policy and support a strategic review of red squirrel management by land management agencies and other stakeholders.

Reinstating trophic cascades as an applied conservation tool to protect forest ecosystems from invasive grey squirrels (Sciurus carolinensis)

Red squirrel (Sciurus vulgaris) range within the United Kingdom (UK) has retracted significantly due to the spread of an Invasive Alien Species, the North American Eastern grey squirrel (Sciurus carolinensis). Where grey squirrels are sympatric, red squirrel populations decline through inter-specific competition and squirrelpox virus (SQPV) infection. Grey squirrel eradication from the island of Anglesey facilitated the complete restoration of native red squirrels. Although native species recovery delivered significant ecological and economic benefits, the eradication extended only to a narrow sea-channel boundary, across which grey squirrel dispersal continues to occur. Hence, the long-term sustainability of Anglesey's red squirrel population is vulnerable to grey squirrel re-establishment without continuous intervention. Recent research has demonstrated that as pine marten (Martes martes) landscape use intensity increases, so too does red squirrel occupancy, likely linked to parallel declines in grey squirrel occupancy. Restoration of this mustelid predator is a potential tool to deliver sustainable grey squirrel control by restoring a missing trophic component, depressing grey squirrel incursion rates onto Anglesey, reducing red squirrel exposure to SQPV. Recent UK pine marten translocations have sourced animals under licence from wild Scottish populations. We explore the alternative use of captive-bred founders, simultaneously introducing new genetic variability against a limited diversity within extant populations. A current conservation translocation is paired with an ongoing assessment of founder behaviour and ‘personality’ measured before release. We then highlight the multi-disciplinary approach to delivering applied red squirrel conservation programmes in the face of invasive species.

Are reports of reduced field efficacy of diphacinone and chlorophacinone in California ground squirrels (Otospermophilus beecheyi) due to elevated rodenticide metabolism?

Anticoagulant rodenticides are commonly used by agricultural producers to control California ground squirrels, Otospermophilus beecheyi, in a variety of crops. With this widespread use, producers are reporting reductions in the efficacy of diphacinone and chlorophacinone for ground squirrel control. Reductions in efficacy have been shown to be related to increased metabolism of compounds to non-toxic metabolites. This study examined liver metabolism of diphacinone and chlorophacinone using microsome isolations from squirrels captured in areas that had never used anticoagulants and areas with a history of prior use. Only male squirrels from anticoagulant exposed areas had a significant reduction in metabolic activity when compared to males from unexposed locations. Based on these data, the cause of the decreased anticoagulant rodenticide efficacy in ground squirrels does not seem to be related to anticoagulant rodenticide metabolism, but may be a result of other physiological (i.e. genetic resistance) or behavioral (bait avoidance) factors.

An application of the impulsive CSOH model for managing squirrels in the coconut farm

In this work, we formulate the mathematical model that incorporates two equations to represent the ultimate goal and controlling strategy to the traditional prey-predator model so that we can investigate the interaction between preys and predators. The model is shortly called the CSOH model. The impulsive practice is added into the model for squirrel control purposes. In particular, we are interested in pulsing the squirrel hunters into the system for every fixed period to control squirrels at the level allowing farmers to have sufficient amount of coconuts so that they can continue their business. We establish the conditions for the squirrel-free periodic solution exists and is globally stable. The numerical simulations reveal that squirrels in the coconut farm could be entirely eradicated by the pulsing strategy. However, the disappearance of squirrels on the farm is not an ecological desire because all species should be allowed to coexist in the system. Consequently, we recommend that the number of squirrel hunters pulsed into the coconut farm should be properly set by considering the time of intervention, expenditure, ecological reasons, and emotional sensitivity of village members.

Mathematical models for invasive species management: Grey squirrel control on Anglesey

The control of invasive species and protection of threatened native species require well-developed policy and species management strategies. Mathematical models provide a key tool that can be used to test, develop and optimise strategies to manage invasive species. We use the native red squirrel and invasive grey squirrel system on the Island of Anglesey, UK, as a case study system in which to parameterise a mathematical model that includes the control of grey squirrels. We develop a stochastic, spatial model that represents the real habitat structure, distribution and linkage on Anglesey and the neighbouring mainland and includes the key population and epidemiological dynamics of the red-grey-squirrelpox system. The model also includes a representation of the trapping and removal of grey squirrels which is parameterised from field data on Anglesey in which grey squirrel were removed and red squirrels reintroduced between 1998–2013. The model is used to assess different management procedures to protect red squirrels from island re-invasion by grey squirrels, including the threat of squirrelpox spread posed by endemic mainland grey populations. The findings have important implications for the conservation of threatened red squirrels throughout the UK and in Europe. Moreover, the modelling framework is based on well-understood, classical models of competitive and epidemiological interactions and therefore the techniques can be adapted and applied more generally to manage the threat of invasive species in a wide range of natural systems.

A preliminary comparison of Magnum 116 bodygrip traps with a live capture trap design during the control of grey squirrels (Sciurus carolinensis)

ABSTRACTThe grey squirrel is an invasive pest species in the United Kingdom and populations are controlled to protect timber crops and native fauna. Although animals are culled using a variety of methods, there are few data available on the relative efficiency of different trap designs, and in particular spring traps. We compared grey squirrel captures in Magnum 116 spring-traps set within Fineren boxes against captures in a single entry live capture trap design. Trapping was conducted in mature mixed woodland in North Wales. No significant difference in the frequency of grey squirrel captures or body mass of trapped individuals between trap designs was observed. Despite the Fineren box design limiting access by non-target species, by-catch was recorded. We make recommendations for future research to minimise this and also compare our results for Magnum 116 traps with data available on captures in Fenn IV spring traps. The findings have broad relevance to the control of grey squirrels across their wider international invasive range.

Knowledge, management and optimization: the use of live traps in control of non-native squirrels

AbstractThis study identifies techniques to maximize trap efficiency and minimize trapping effort when using live traps to capture the invasive alien Pallas’s squirrel (

Landscape scale impacts of culling upon a European grey squirrel population: can trapping reduce population size and decrease the threat of squirrelpox virus infection for the native red squirrel?

The control of grey squirrels (Sciurus carolinensis) is widely undertaken as a conservation measure to protect red squirrel (Sciurus vulgaris) populations in the UK. However, inconsistencies and omissions in data collection, as well as fluctuating financial resourcing of control efforts, have meant that it has to date proved difficult to quantify the impact of any regional control initiative upon populations. Here we have scrutinized a 13 years period (1998–2010) within an ongoing grey squirrel control project that reflects the resource challenges typically faced by red squirrel conservation programmes. We present evidence that despite variation in grey squirrel control intensity, the abundance of grey squirrels ultimately decreased significantly. Trapping success was significantly higher in spring and summer months and a greater abundance of grey squirrels was found in deciduous woodland and hazel dominated scrub relative to other habitats; two findings that reinforce existing guidance within national control best practice. Grey squirrels carry an infection that causes epidemic pathogenic disease if spread to the native red squirrel. We observed that the proportion of seropositive grey squirrels decreased constantly from 2003 to 2010 when only 4 % of sampled animals were seropositive. This discovery indicates that culling can in parallel remove both the competitive and disease threat posed to red by grey squirrels. The historical paucity of scientific data on the effectiveness of grey squirrel control as a tactic in UK red squirrel conservation means that the findings of this study will significantly advance conservation best practice and inform the development of future national strategy.

The Applicability of Burrow Fumigants for Controlling Belding’s Ground Squirrels in Alfalfa

Rodenticides are often used to control burrowing rodents but have not been overly efficacious for Belding’s ground squirrels due to poor bait acceptance. This has left alfalfa growers searching for alternative options for controlling this rodent species. As such, we tested aluminum phosphide and gas cartridge burrow fumigation in an alfalfa field in Butte Valley, CA, to determine if either of these approaches were efficacious and cost effective for controlling Belding’s ground squirrels. A comparison of the number of burrows treated and the number of burrows reopened 48-hours post-treatment indicated that both burrow fumigants were highly effective (aluminum phosphide = 94-98%, gas cartridges = 100%). The average cost per application was $1.05 and $2.92 for aluminum phosphide and gas cartridges, respectively. Given the almost 3-fold difference in cost of application between the two approaches, aluminum phosphide appears to be the more practical approach for Belding’s ground squirrel control. Although we currently lack an approach for estimating the amount of damage that Belding’s ground squirrels are likely to cause to an alfalfa field, it seems plausible that burrow fumigation could be a cost effective approach to reduce damage caused by this species, particularly if long-term control can be obtained. Possible long-term management options for Belding’s ground squirrels are discussed.

Implementation of proportional integral (PI) controlled DSP based cost effective inverter fed speed control of induction motor drive with VisSim/ embedded controls and developer (ECD)

Real-time implementation of PI controller based cost effective inverter fed speed control of induction motor drive using high performance TMS320F2812 DSP with VisSim/ embedded controls and developer (ECD) is presented in this paper. The four switch three-phase inverter (FSTPI) fed drive system consists of a power circuit having an insulated gate bipolar junction transistor (IGBT) based bridge inverter module feeding a 5 hp three-phase squirrel cage induction motor and control circuits that comprises of digital signal processor (DSP), processor board, driver circuit, sensor (for sensing speed signals), interfacing circuits and PC with VisSim/ECD software. The PI controller block and PWM generation block of this drive system are designed using VisSim/ECD to control the speed of induction motor in closed loop. Observations are made by changing speed of motor at different loads. Results obtained from this experimental work are satisfactory and shown using GUI of VisSim /ECD software and digital storage oscilloscope. Key words: Four switch three-phase inverter (FSTPI), digital signal processor (DSP), proportional integral (PI), Sinusoidal pulse width modulation (SPWM) and VisSim/ embedded controls and developer (ECD).

Fumigation of California Ground Squirrels Revisited: Are Fumigants an Effective Method for Controlling Ground Squirrels?

Fumigation with either gas cartridges or aluminum phosphide is often considered to be an effective method for controlling California ground squirrel populations, although few studies have corroborated their effectiveness. Additionally, utilizing aluminum phosphide in combination with gas cartridges could increase effectiveness of both fumigants by indicating additional burrow openings through escaping smoke from gas cartridges and allowing for treatment of these additional openings with aluminum phosphide, which is a cheaper and potentially more effective material. Therefore, we compared the efficacy of gas cartridges, aluminum phosphide, and a combined treatment on ground squirrel populations from mid-April through early May 2009 to determine which was most effective. We established 4 plots (3 treatments plus control) at each of 2 treatment sites in Madera County, California. All plots were between 1 and 2 ha in size with survey areas of 0.3 - 0.5 ha centrally located within the plot. Ground squirrels were visually counted within survey areas for 3 consecutive days prior to treatment. Following counting, treatments were applied. Forty-eight hours post-treatment, squirrels were again counted within survey areas to determine percent control. These counts were repeated the following 2 days. All treatments were then reapplied for the same plots, with similar surveys again following 48 hours post-treatment. We found that all fumigation methods resulted in marginal to exceptional control of ground squirrels (percent control: gas cartridges = 62 - 86%, aluminum phosphide = 97 - 100%, gas cartridges + aluminum phosphide = 59 - 71%). We suggest aluminum phosphide use could be expanded to increase ground squirrel control in California, given its high efficacy combined with its relatively cheap material cost.

Strychnine for the Control of Richardson’s Ground Squirrels: Efficiency and Selectivity Issues

S trychnine has recently been made available in Canada under an emergency registration program for the control of Ri chardson's ground squirrels. From 2007 to 2009, we tested the control efficacy of this poison using >1,year,old and newly produced strychnine on hulless oats, canary seed, and alfalfa pellets. Newly produced 2% liquid strychnine, mixed with hulless oats to formulate 0.4% strychnine freshly mixed baits, controlled ≥70% of adult and juvenile ground squirrels in spring and summer. Other types of strychnine baits were not as reliable from one season to the other. At 0.2% concentration, strychnine,treated oats were relatively inefficient. When >1 year old, the control efficacy of strychnine baits dropped significantly. Independent of the age of the product, strychnine killed non,target animals. This paper recommends a series of measures to ensure quality control and greater selectivity.

Ground Squirrel Control Training and Certification using an Interactive Computer Kiosk System

Author(s): Newman, Peter; Salmon, Terrell P. | Abstract: This study was undertaken to demonstrate and assess the efficacy of a new outreach education tool, an interactive touch-screen computer (kiosk) for ground squirrel control education. The target audience for the concept is the California agricultural industry and urban members of the public who are dealing with ground squirrel problems. Users of the computer kiosk are able to access various learning tools: a learning library, a quiz, video learning, an interactive decision-making tool, and they are able to print information and certificates. The computer kiosks are available at select California County Agricultural Commissioner offices. They are networked (computer linked) so that the education content is capable of being added to or amended from remote locations. In addition, the kiosks seamlessly gather statistical data and also collect voluntary information from users (i.e. email addresses and comments). The success of the computer kiosks demonstrated their potential for use in statewide continuing education and pesticide applicator certification efforts related to vertebrate pest control.

Live-Trapping California Ground Squirrels is for the Birds

California ground squirrels are known to inhabit different landscapes and terrains. Farms and ranches with ground squirrels are often at an advantage over other types of locations such as schools and public parks, where squirrel control options are more limited. Many private companies and public agencies dealing with squirrel problems experience public opposition to the use of poisons in public areas and must find other workable solutions. Live-trapping California ground squirrels is one control method that is being considered by many agencies. City and county parks, public and private schools, horse boarding stables, and organic farms are some of the locations appropriate for use in this type of program. The use of live-traps for safety and target-specific reasons, and the use of CO2 as the most humane method of euthanasia for rodents, are widely accepted by most people, even when the trapping is done openly in public. Live trapped ground squirrels can have a benefit beyond the reduction of squirrel damage. Using trapped squirrels as a natural food source for hawks, owls, and eagles at raptor rehabilitation facilities makes this approach an effective, safe, and acceptable control method in specific places.

Modelling the Expansion of a Grey Squirrel population: Implications for Squirrel Control

A recently discovered population of the North American grey squirrel (Sciurus carolinensis), introduced to Ticino Park, Lombardy (N Italy), is likely to spread into continuous prealpine broadleaf forests of Lombardy and the south of Switzerland. We used Spatially Explicit Population Dynamics Models (SEPMs), successfully used to predict the spread of grey squirrels in England and Piedmont, Italy, to examine the effects of different control scenarios on grey squirrel expansion in a 20000 km2 area around Ticino Park. Without control, grey squirrels will invade Switzerland within the next two decades, and, concomitantly, the size and distribution of local populations of native red squirrels will be reduced. Simulating different grey squirrel control or removal scenarios suggests that: (i) efficient control is possible and mainly determined by the spatial distribution and woodland size of the ‘target’ control areas; and (ii) immediate actions must be taken, since delay in grey squirrel control will result in the population increasing and spreading, which makes the problems of successful containment more difficult. Model scenarios were based on surveys that may underestimate the real distribution range and current population size of grey squirrels. Therefore, a combination of hair–tube monitoring and a public participation survey to detect grey squirrel presence, which may also help to increase public awareness, is recommended. Successful containment of further grey squirrel spread will require local co-operation between Italian and Swiss authorities involved in wildlife management.