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Evaluation of tick control tube month of placement and modifications to increase visitation by small mammals
Abstract
Tick control tubes are a host-targeted tick control method targeting immature Ixodes scapularis ticks attached to mice or found within mouse burrows and nests. Tick control tubes contain permethrin-treated cotton inside cardboard tubes that mice use as nesting material. Ticks attached to mice or present in their burrows are exposed to the treated cotton. However, there have been variable results using these tubes for tick control. Rodent visitation and use of these tubes may influence their effectiveness. The aim of this study was to evaluate small mammal use of tick control tube cotton and to evaluate whether cotton size or odor attractants changed small mammal tube visitations and cotton removal. For the cotton size experiment, three different cotton sizes were used. In the odor attractant experiment, three different odor attractants were used (peanut butter, safflower oil, and vanillin) along with a commercially available tube as a control. A negative control group that had no cotton present in the tube was used for both experiments. Cotton loss was determined by weighing cotton in deployed tubes weekly, and mouse and nontarget species interactions were evaluated using camera-trap data collected at each site. While the tested cotton sizes and odor attractants did not affect cotton use, mice did increasingly use cotton during cooler fall months, with the highest use of cotton in October and least use in July. These results suggest that mouse use of cotton was not related to cotton size or odor attractants but was dependent on season. This warrants future research on temporal small mammal use of tick control tubes to determine optimal deployment times for tick control.
INTRODUCTION
Lyme disease is the most frequently diagnosed zoonotic disease in the United States, with an estimated 476,000 cases diagnosed and treated annually (Kugeler et al., 2021). Lyme disease is endemic in North America, and with no human vaccinations currently available, the most effective method for preventing Lyme disease and other tick-borne illnesses is to reduce human exposure to infected ticks. The primary vector of this tick-borne disease is the blacklegged tick (Ixodes scapularis), which feeds on infected rodents and can transmit the causative agent of Lyme disease to humans through infected tick bites (Piesman, 1989). Mice in the genus Peromyscus are important vertebrate reservoirs for several prevalent zoonotic and vector-borne diseases in North America, including the causative agents of Lyme disease (Borrelia burgdorferi), babesiosis (Babesia spp.), and anaplasmosis (Anaplasma spp.) (Bishopp & Trembley, 1945).
There are several strategies available to reduce exposure to tick bites. These can be used separately or in tandem to reduce exposure and include strategies such as reducing overall tick abundance, reducing the number of infected ticks in the population, or modifying human behaviors to reduce tick encounters. Various tick control methods have been studied as potential solutions in reducing overall tick abundance, including habitat modification (such as the removal of leaf litter), broadcast acaricide application, and controlled burns (White & Gaff, 2018). While all of these strategies have been effective in reducing tick abundance within large, treated areas for one to two seasons, they also have significant ecological impacts on nontarget species (Gleim et al., 2014; Ostfeld et al., 2006). While host-specific tick control methods, such as four-poster deer feeders and rodent bait boxes, can significantly reduce tick infestation on target vertebrate species, these treatments can also have negative ecological impacts due to supplemental feeding of wildlife (Machtinger & Li, 2019) and are not feasible for broad-scale use due to the high cost of installation and upkeep (Dolan et al., 2004; Schulze et al., 1995). In addition, many tick control strategies require certified pest control operators for installation and maintenance.
Tick control tubes are a host-targeted method for control of immature I. scapularis ticks parasitizing rodents. They consist of permethrin-treated cotton inside cardboard tubes. Rodent use of the treated cotton as nesting material reduces the number of ectoparasites on the rodents and in their nests and burrows. Tick control tubes are inexpensive compared to many other tick control options and easy to use, but results have varied on their effectiveness in reducing tick infestations on rodents and reducing the total abundance of ticks in the treatment area (White & Gaff, 2018). Early studies in Massachusetts showed a significant reduction in I. scapularis infestations on Peromyscus spp. with tick control tube deployment (Mather et al., 1987), but others have shown varied effects of treatment on host infestation and on the abundance of host-seeking ticks (Daniels et al. 1991; Stafford III, 1991, 1992). These studies varied in the length of tick control tube deployment and surveillance of rodent visitations and cotton usage, with some deploying the tick control tubes once per year and others deploying tick control tubes twice, coinciding with the nymphal and larval feeding stages of immature ticks. However, in each of these studies tick infestations consistently decreased when the majority of the treated cotton was removed from the tubes, suggesting tick control tubes have the potential to be an effective control option for tick infestations on rodents if the treated cotton is consistently used by Peromyscus spp.
There is a need to assess animal interactions with tick control tubes to improve recommendations as a tick control strategy. Timing of deployment and use of the tick tube cotton has not been previously evaluated. The current study objectives were to (1) evaluate whether changing cotton size or adding an odor attractant affected small mammal visitation of tubes and amount of cotton removed from the tubes by weight, and to (2) evaluate target and nontarget species use of tick tube cotton using camera-trap data. This information can be used to improve recommendations for deployment and increase efficacy of tick control tubes as a tick control method.
METHODS
Study areas
The study was conducted from 12 June to 27 October 2020 at four sites in Centre County, PA, USA, within Pennsylvania State Game Lands No. 103 (SGL 103, 40.97 N, 77.91 W) and 176 (SGL 176, 40.78 N, 77.96 W) and Pennsylvania State University properties located in University Park (site Animal Diagnostics Laboratory [ADL], 40.82 N, 77.85 W) and Pennsylvania Furnace (site Ag Progress Days [APD], 40.70 N, 77.96 W) (Figure 1). SGL 103 is a northern hardwood forest characterized by drought-prone and acidic soils, with a history of prescribed burns and contains a mix of red maple (Acer rubrum), chestnut oak (Quercus montana), striped maple (Acer pennsylvanicum), and mountain laurel (Kalmia latifolia). SGL 176 is a scrub oak–pitch pine barren characterized by drought-prone and acidic soils and contains a mix of pitch pine (Pinus rigida), jack pine (Pinus banksiana), white pine (Pinus strobus), dense scrub oak (Q. ilicifolia), and mountain laurel. ADL is a northern hardwood forest surrounded by urban areas and is characterized by moist and fertile soil and contains a mix of red maple, chestnut oak, witch-hazel (Hamamelis virginiana), and northern hackberry (Celtis occidentalis). APD is a northern hardwood forest characterized by wet meadow areas and a history of regenerative management practices containing a mix of red maple, eastern hemlock (Tsuga canadensis), white pine, invasive multiflora rose (Rosa multiflora), and Japanese barberry (Berberis thunbergii).
Trail cameras
The tick control tubes were deployed at each of the four sites for 1 week each month for the cotton size experiment and 1 week each month for the odor attractant experiment. Each study site had two plots (Site A and Site B). Paired plots were set 25 m from each other, 5–10 m from roads in brushy forest edge areas, and at least 100 m from other paired plots (Figure 2). Trail cameras (30-MP Bushnell Core DS No-Glow trail camera, Bushnell Outdoor Products, Overland Park, KS, USA) were moved between paired plots. Cotton size and odor treatments were switched between Site A and Site B paired sites for each data collection period to reduce variation in mice cotton use based on habitat, population, and mouse habituation to tubes. Vegetation interfering with camera traps was cleared and maintained throughout the study. Trail cameras were secured on a mounting stick set to 1 m (Stealth Cam trail camera mounting stick, GSM Outdoors, Irving, TX, USA). Cameras were placed approximately 1 m from the tick control tubes and aimed toward the tick tube on the ground to capture small mammal visitations and cotton usage (Figure 3).
Both photo bursts (in sets of 3) and videos were recorded. Photographs were taken for animal visitations less than 3 s, after which videos were taken for 60 s at a time. All animal visitations were recorded (target and nontarget species), as well as foraging time in the camera field, and cotton removal success. Camera data were analyzed by the number of visitations where mice actively investigated the cotton and either removed or did not remove the cotton, as well as other animals that either investigated the tick control tube (showed interest but did not damage or change the tube) or interfered with the tube (disturbed or destroyed the tube or cotton). Nontarget species interactions observed on trail cameras were recorded by type of disturbance and damage to the tick control tube.
Cotton size experiment
Four different treatment groups were used to assess cotton use. Three different sizes of cotton were used along with one negative control; “small” (0.45 g per cotton ball; Damminix Tick Tubes, EcoHealth Inc., Brookline, MA, USA), “medium” (positive control; 1.5 g per cotton ball; Thermacell tick control tubes, Thermacell Repellents, Inc., Bedford, MA, USA), and “large”—a size that was larger than commercially available tick control tubes (2.5 g per cotton ball; provided specifically for this experiment by Thermacell Repellents), and lastly, a negative control that consisted of a “medium” Thermacell tick tube without any cotton present (Thermacell tick control tubes) (Figure 4). The negative control was used to determine target and nontarget species' interest in the tube itself compared to interest in use of the cotton present in the other three treatments. Treatments were randomly assigned to one plot in each of the four sites for the entirety of the study. Tick control tubes were given unique identifiers, staked into the ground, and marked with a utility flag. In total, 80 tick control tubes were divided evenly between treatment groups with four tick control tubes of each treatment deployed for 1 week each month, resulting in 20 tubes of each type deployed over the entire study period from June to October 2020.
Before deployment, the tubes were placed in a temperature-controlled room for 24 h, after which the cotton was weighed and recorded prior to being placed in the field. After the tick control tubes were deployed for a week and recovered from the field sites, the cotton was dried in an oven at approximately 60°C for 24 h, removed, and placed in the same temperature-controlled room for another 24 h before final weights were recorded to account for natural humidity rehydration. The amount of cotton loss was determined by comparing predeployment and postdeployment weights for the week the tick control tube was at the field site.
Odor attractant experiment
Five treatment groups were used for the odor attractant experiment, with three odors: peanut butter odor (Indigo Fragrance #406, Necedah, WI), vanillin odor (Sigma-Aldrich #121-33-5, MilliporeSigma, Burlington, MA), and safflower oil odor (Sigma-Aldrich #S8281, MilliporeSigma), at approximately 0.8 g/cm2 per tick control tube. The other two treatment groups consisted of commercially available Thermacell tick control tube with no odor attractant (odor control) and an odor negative control that consisted of a commercially available Thermacell tick control tube without cotton or odor present. Each odor was on a 2.54 × 2.54 cm cellulose mat provided by Thermacell, with the cellulose mat encased in 10-mesh size wire mesh and installed in the tube with twist ties (Figure 5). The control tube had cotton and an odor packet installed with an unscented cellulose mat, while the odor negative control did not contain cotton or an odor packet. The negative control was used for the same purpose as for the cotton size experiment. Odor treatments were randomly assigned to one plot in each site for the entirety of the study. In total, 100 tick control tubes were divided evenly between treatment groups with 5 tick control tubes of each treatment deployed for 1 week each month, resulting in 20 tubes of each type deployed over the entire study period from June to October 2020 (IACUC Protocol Number: 202101818, PAGC Special Use Permit: 45936). Cotton use and field camera settings were the same as in the cotton size experiment.
In August 2020, 20 additional tick tube plots were added at SGL 176 without field cameras to increase the number of replicates for odor treatment tick control tubes and cotton size tick control tubes, with cotton use determined via cotton weights pre- and postfield deployment. The additional sites were used at the same time as all other sites for August, September, and October adding an additional 48 cotton size tick tube replicates and 60 odor treatment tick tube replicates.
Statistical analyses
To determine whether cotton size had an effect on whether mice collected cotton at all, a 2 × 2 χ2 test of independence was used to compare cotton sizes to the commercially available Thermacell tick control tubes (“medium” tick tube in cotton size experiments). This was also calculated for the odor types.
To determine whether nightly cotton removal by mice was influenced by different sizes of cotton, a linear mixed model was created using the “nlme” package (Pinheiro et al., 2020). Cotton size was treated as a fixed effect. Sampling sites were considered the random effect to account for their repeated observation over time. Month was not included in this model as too few replicates produced nonzero results in cotton loss. A similar model was built for the different odors and control. Due to an insufficient number of tubes that had cotton loss, the months of June and July were excluded from the odor model. Fixed effects were the odor treatment and month of treatment. For both the cotton size and odor treatment models, correlograms confirmed no temporal autocorrelation among the months. Normality of residuals and homogeneity of variance were also assessed, and data were log transformed to meet these assumptions when necessary.
To determine whether there was an effect of cotton size or month on the frequency of mice visits when tick tubes were visited at all, a series of generalized linear mixed models were built using the “lme4” package (Bates et al., 2015), with cotton size treatment and month as fixed factors and sampling sites as a random factor to account for their repeated measure. A Poisson distribution with a log link function was used in each model. The significance of each fixed effect in each model was assessed with likelihood ratio tests in a step-down process. The same type of models was built for odor treatments.
To determine whether there was an effect of cotton size on the frequency of nonmouse visitations when tick tubes were visited at all, a series of generalized linear mixed models were built using the “lme4” package (Bates et al., 2015), with cotton size as a fixed factor and sampling sites as a random factor to account for their repeated measure. The same type of models was constructed for the odor treatments. A binomial distribution with a logit link function was used in each model. The significance of the parameters in each model was assessed with likelihood ratio tests in a step-down process.
When appropriate, pairwise comparisons of least-squares (LS) means of cotton loss in sequential months (e.g., June vs. July and August vs. September) were conducted using the “emmeans” package (Lenth, 2020). Least-squares means were used in lieu of arithmetic means because they take into account imbalances in the data (Lenth, 2016).
To test whether damage severity was dependent on cotton size or odor type in the tick control tubes, a Fisher's exact test was used with Monte Carlo simulation using 1 million replicates.
RESULTS
Cotton use by size
Across all sampling times and locations, whether mice collected cotton at all were independent of cotton size compared to the control tube (commercially available Thermacell tick control tube) (all χ2 < 0.38 and all p > 0.536; Table 1). Removal of cotton at all was independent between sequential months except between August (37.5% of tubes had cotton removed) and September (73.9% of tubes had cotton removed) (χ2 = 4.91, p = 0.027; Figure 6). Although the large cotton treatment had more cotton loss than the other treatments in 3 of the 5 months, cotton size did not significantly affect the amount of cotton removed per night by mice (F = 2.59, p = 0.085; Table 1).
| Cotton size | June | July | August | September | October | Cotton presence (% tubes/treatment)a |
|---|---|---|---|---|---|---|
| Small | 0.517 ± 0.058 (3) | 0.070 (1) | 0.160 ± 0.120 (2) | 0.060 ± 0.026 (8) | 0.277 ± 0.071 (6) | 60.6 |
| Medium | 0.120 (1) | 0.063 ± 0.040 (4) | 0.655 ± 0.005 (2) | 0.390 ± 0.190 (3) | 0.240 ± 0.0780 (8) | 58.1 |
| Large | 0.340 (1) | 0.245 ± 0.085 (2) | 0.296 ± 0.149 (5) | 0.448 ± 0.0660 (6) | 0.299 ± 0.080 (8) | 68.8 |
| Cotton presence (% tubes/month)b | 38.5 | 58.3 | 37.5 | 73.9 | 91.7 |
- Notes: Cotton sizes were large = 2.5 g, medium = 1.5 g, and small = 0.45 g per piece. Values in parentheses are the number of tick control tubes that had any cotton missing. The greatest observed cotton loss per day by treatment within each month is in boldface.
- a Percentage of tubes per treatment in which cotton was used at all.
- b Percentage of tubes per month in which cotton was used at all.
Cotton size did not explain the patterns of mice visits to the tubes (Akaike information criterion [AIC]; AICnull = 823.72, AICsize = 827.23; χ2 = 2.49, df = 3, p = 0.478), but month was significant in explaining how many mice visited nightly (AICmonth = 767.94; χ2 = 67.30, df = 4, p < 0.001; Figure 7). July had the fewest visitations by mice (LS mean ± SE; 0.33 ± 0.198 visits per night), and August had the highest number of visitations (1.44 ± 0.172 visits per night), followed closely by October (1.38 ± 0.170 visits per night). Between sequential months, there was a significant pairwise comparison between June and July (p < 0.001), July and August (p < 0.001), August and September (p = 0.001), and September and October (p = 0.005).
Cotton use by odor and month
Whether cotton was taken at all from tick control tubes was independent of odor type compared to the control (all χ2 < 1.20, p > 0.274), although nearly 25% more peanut butter tick tubes had cotton removed than the tick tubes without odor. Cotton was removed from tick tubes with peanut butter odor in four of the five treatment months. Whether cotton was removed at all was independent between sequential months except for September and October (χ2 = 6.18, p = 0.013; Figure 8). Less than 50% of tick tubes had cotton loss in June and July. This increased to over 70% in August and September, and over 90% in October. When cotton was removed by mice, there was no difference in the amount removed among odor types or control (F = 1.63, p = 0.192; Table 2). The amount of cotton removed by mice significantly differed among the months sampled (F = 3.69, p = 0.030; Figure 9). There was a significant pairwise difference between September and October (p = 0.009), with the amount of cotton removed in October (LS mean ± SE; 0.235 ± 0.0436 g) greater than in August (0.127 ± 0.0471 g) or September (0.135 ± 0.0475 g).
| Treatment | June | July | August | September | October | Cotton presence (% tubes/odor type)a |
|---|---|---|---|---|---|---|
| Peanut butter | 0.048 ± 0.0301 (4) | 0.375 ± 0.295 (2) | 0.140 ± 0.061 (6) | 0.174 ± 0.118 (5) | 0.133 ± 0.065 (8) | 78.1 |
| Safflower oil | 0.025 ± 0.005 (2) | 0.335 ± 0.325 (2) | 0.093 ± 0.025 (6) | 0.090 ± 0.038 (6) | 0.150 ± 0.074 (8) | 75.0 |
| Vanillin | 0 (0) | 0.010 (1) | 0.077 ± 0.016 (6) | 0.172 ± 0.117 (5) | 0.371 ± 0.094 (7) | 61.3 |
| Thermacell control (no odor) | 0.01 (1) | 0.150 ± 0.110 (2) | 0.084 ± 0.029 (5) | 0.018 ± 0.006 (5) | 0.173 ± 0.088 (7) | 62.5 |
| Cotton presence (% tubes/month)b | 46.7 | 43.8 | 71.9 | 65.6 | 93.8 |
- Notes: Odor treatments were volatile odors saturated on a cellulose pad provided by Thermacell, encased in mesh, and suspended in the tick tube using twist ties. Values in parentheses are the number of tick control tubes that had any cotton missing. The greatest observed cotton loss per day by treatment within each month is in boldface.
- a Percentage of tubes per odor type in which cotton was used at all.
- b Percentage of tubes per month in which cotton was used at all.
Odor did not appear to explain patterns of mice visits (AICnull = 1447.0, AICodor = 1446.3; χ2 = 8.71, df = 4, p = 0.069), but month did (AICmonth = 1390.4; χ2 = 63.90, df = 4, p < 0.001; Figure 9). Mouse visitations were the lowest in June (LS mean ± SE; 0.87 ± 0.141 visits per night) and the highest in October (1.61 ± 0.100 visits per night). Between sequential months, September and October were significantly different (p < 0.001).
Tube damage and animal interference
There was a significant effect of cotton size on nontarget animals that interfered with tick control tubes (AICnull = 225.09, AICodor = 222.21; χ2 = 8.88, df = 3, p = 0.031; Figure 10). More nontarget animal interference was observed with large cotton tick tubes compared to small cotton tick tubes (p = 0.009), control tick tubes (p = 0.019), and tick tubes without cotton (p = 0.019).
There was a significant effect of odor on nontarget animal interference with tick tubes (AICnull = 427.47, AICodor = 408.95; χ2 = 26.52, df = 4, p < 0.001; Figure 10). Interestingly, more nontarget animal interference was observed on the control tubes than tubes with peanut butter odor (p < 0.001), safflower oil odor (p = 0.027), vanillin odor (p = 0.007), and tubes with no cotton and no odor (p = 0.001). There was also more nontarget animal disturbance of tubes with safflower oil odor than peanut butter odor (p = 0.008). Nontarget animal disturbance was classified into three categories based on camera-trap observations (Table 3). Of the 14 nontarget species observed interfering with tick control tubes, 5 of these species chewed on the outside of the tubes, which did not directly affect the ability of mice to retrieve treated cotton from the tick tubes as the tubes were checked and collected weekly. Northern raccoons were recorded causing the greatest amount of interference with the tick control tubes, both due to the number of visitations to the tubes and the extent of damage.
| Species | Tick control tube interference | ||
|---|---|---|---|
| Chewed tube | Removed cotton | Destroyed tube | |
| Eastern chipmunk (Tamias striatus) | × | × | |
| Eastern cottontail (Sylvilagus floridanus) | × | × | |
| Eastern gray squirrel (Sciurus carolinensis) | × | ||
| Groundhog (Marmota monax) | × | × | |
| Virginia opossum (Didelphis virginiana) | × | ||
| Northern raccoon (Procyon lotor) | × | × | × |
| Striped skunk (Mephitis mephitis) | × | ||
| American black bear (Ursus americanus) | × | ||
| Vole (Myodes or Microtus spp.) | × | ||
| Northern flying squirrel (Glaucomys sabrinus) | × | ||
| Gray catbird (Dumetella carolinensis) | × | ||
| House wren (Troglodytes aedon) | × | ||
| American robin (Turdus migratorius) | × | ||
| Hermit thrush (Catharus guttatus) | × | ||
- Notes: Some individuals did not interfere with tick tubes in ways that affected the treated cotton within the tube (“chewed portion of tube”), while others directly removed cotton from the tick tubes or destroyed the tick tube entirely, affecting the treatment available. “Chewed tube” behavior was defined as observed gnawing of the tube by the animal. “Destroyed tube” was defined as an animal ripping the tube cardboard shell so that it was not functional for its intended purpose.
During cotton size trials, tick tube damage severity was independent of cotton size (p = 0.418) and month (p = 0.495; Appendix S1: Figure S1). During the odor trials, damage severity of tick tubes was independent of odor type (p = 0.137). There was also no difference in tick tube damage by month (p = 0.525).
Overall, nightly mice visitations and amount of cotton removed were independent of both odor and cotton size, with the month being the only factor showing significant effect on both measures.
DISCUSSION
Tick control tubes exploit the natural foraging and nesting behavior of mice by providing a nesting material treated with a tick repellent that the mice bring back to their nesting sites. However, effectiveness of tick control tubes has varied in previous studies. Changes in materials, time and length of deployment, and placement could affect mouse use of cotton from tick control tubes. Modifications that could increase mouse use of cotton in tick control tubes could increase their effectiveness as a tick control method. The purpose of this study was to determine whether an odor attractant or whether differences in cotton size changed mouse use of tick control tubes, but additional covariates demonstrated the influence of seasonal deployment on tick control tube use by mice.
Different cotton sizes were investigated as size may influence ease of accessibility and use for mice visits. When foraging for nesting materials, mice tear pieces of nesting material from the source and carry the shredded material in their mouths back to their nest. Smaller cotton balls may be easier for mice to use, and thus, mice may be more likely to use this cotton (Deacon 2006). However, while cotton size did not significantly contribute to mouse visitation or cotton use in this study, the large-sized cotton did result in higher cotton loss in three out of five months of the study. This may be due to a larger amount of cotton able to be removed at one time with the large-sized cotton balls. These results could indicate that cotton size may have a greater influence on total cotton removal during times of the year when nest foraging behaviors are high.
Peromyscus spp. use odors when foraging by associating the scents with food sources or with predation. While overall there was no significant difference in whether mice visited tick control tubes more frequently or removed more cotton with an odor attractant present, mice did remove cotton more frequently from tick tubes with peanut butter odor compared to all other treatments. While these results were not statistically significant, this pattern of mouse use with peanut butter odor should be explored in greater depth in future studies. Increase in odors or modifications for greater volatility may increase effectiveness. A larger sample size may better clarify if peanut butter odor attracts these target species and increases mouse use of cotton in tick control tubes. Mice also removed cotton from peanut butter tick control tubes 4 out of 5 months during the experiment. Because mice associate scents with previous experiences, mice that have associated peanut butter odors with food may be more likely to be attracted to the scent of peanut butter (Drickamer, 1972). However, it is unclear whether mice would increase visitations to odors associated with nonfood resources (i.e., nesting material).
It is critical to consider mouse ecology and tick phenology in the placement timing of tick control tubes. In this study, there was less cotton use during the summer months of June and July, but cotton use increased during the months of August and September and substantially increased in October. Mice were also more frequently seen on trail cameras exploring the tick control tubes in the fall, with the highest number of visitations in October, and least frequently visited the tick control tubes in the summer, with the lowest number of visitations in June. Studies have previously shown peak mice populations are between late summer and late fall, which could contribute to the increase in cotton use (Burt, 1940; Rintamaa et al., 1976). Seasonal behaviors may also contribute to increased cotton use. Nests are primarily used by rodents as a method of heat conservation, of most importance during the cooler months in fall and winter (Glaser & Lustick, 1975). With less of a need to build insulated nests during the summer months, the energy allocation of foraging for food is higher than the energy allocated to building a nest and foraging for nesting materials. The need for a warmer nest is more critical in September and October when temperatures begin to drop in the northeast United States, potentially leading to an increase in cotton use as more energy is allocated to finding warm nesting materials. While it is also possible that mouse visitations increased as a result of continuous placement of the tubes with mice more likely to visit tick control tubes as they became more familiar with them over the course of the study, this is likely negligible as tick control tubes were removed after each week-long deployment followed by 2 weeks without tick control tubes present between each experiment.
Previous studies have found that tick control tubes were ineffective as a tick control method for rodents. In these studies, tick control tubes were deployed once in the spring and once in the summer to coincide with nymphal feeding and the larval stage of ticks (White & Gaff, 2018). Based on our findings, tick control tubes deployed on this schedule would be ineffective and would be influenced by low cotton use during the summer and an inadequate tube replacement schedule when cotton was depleted. More tubes may need to be placed in the earlier spring and summer months to increase encounter rates when mouse populations are lower. In addition, increased tube numbers or frequency of replacement may be necessary in August through October to coincide with high cotton use by mice during the breeding season and increased nest-building in the fall. This could potentially increase the effectiveness of tick control tubes in reducing tick burdens the following spring season, but this would need further study to determine the longevity of permethrin effects.
Interestingly, tube damage and interference by nontarget species were not related to odor treatment nor to seasonality and nontarget interference was more prevalent with control tubes without odor compared to tick control tubes with odors present. This indicates that if the peanut butter odor is used as an attractant to mice in future tick control tubes, particularly during these times of high use in the fall months of September and October, peanut butter will not act as an attractant to nontarget species and may even attract fewer nontarget species compared to not using an odor attractant. This is exciting as the possibility to increase target use and decrease nontarget use of tick control tubes is critical in adequate small mammal treatment and tick control. Potentially, other odors can be used that mimic food sources for specific locales, such as fruit odors native to the geographic region.
Tick control tubes have the potential to be effective if the treated material in the tick control tubes is available to tick hosts. Based on these results, cotton size and supplemental odors did not influence mouse use of treated cotton. However, additional exploration of odors is warranted. Tick tube deployment should be based on tick phenology as well as host use of tick tubes. Current recommendations may need to be modified to increase mouse encounters with treated cotton when use of cotton by mice is low and to increase treated cotton availability during times of highest cotton use by mice, shown here to be September and October. The use of tick control tubes in small areas, such as around homes or urban areas, could reduce the exposure of humans to Lyme disease by reducing the tick burdens of mice within highly trafficked areas. Additional studies to improve tick control tube use are still needed, including studies evaluating frequency and timing of deployment and replacement of tick control tubes for adequate mouse use of tick tube cotton for effective tick control, as well as population-level effect on tick burdens.
AUTHOR CONTRIBUTIONS
Erika T. Machtinger conceived the study; Erika T. Machtinger, Kylie D. Green, Hannah S. Tiffin, and Jessica E. Brown contributed to study design; Kylie D. Green, Jessica E. Brown, and Hannah S. Tiffin collected data; Kylie D. Green with input from Hannah S. Tiffin and Erika T. Machtinger evaluated camera-trap data; Edwin R. Burgess IV performed statistical analyses; Kylie D. Green and Hannah S. Tiffin, with critical revisions and review of final manuscript provided by all authors initially drafted the manuscript. All authors contributed to final interpretations of data analyses and have read and approved the manuscript. Kylie D. Green and Hannah S. Tiffin contributed equally and are considered co-first authors of the final manuscript.
ACKNOWLEDGMENTS
The authors would like to thank Cera Dickerson, Jesse Evans, Chloe Roberts, and Anna-Marie Wise for their contributions during fieldwork conducted for this project. We thank the Pennsylvania Game Commission for use of the Pennsylvania State Game Lands and Penn State University for use of Penn State properties for this research.
CONFLICT OF INTEREST
Funding was graciously provided by Thermacell Repellents, Inc., to ETM to support tick ecology research.
Open Research
DATA AVAILABILITY STATEMENT
Data (Green et al., 2022) are available from Data Commons: https://doi.org/10.26208/nhyz-3s33.
