Good Nature© piston trap trial on farms in Delta Fall 2020/Spring 2021 Written by Sofi Hindmarch 1 Table of Contents Acknowledgement ........................................................................................................................................ 3 Executive Summary....................................................................................................................................... 3 Introduction .................................................................................................................................................. 4 Methods ........................................................................................................................................................ 5 Study Area ................................................................................................................................................. 5 Piston Trap Trial ........................................................................................................................................ 6 Results and Discussion .................................................................................................................................. 9 Deer mice attracted to the piston traps ................................................................................................. 10 Non-target species attracted to the piston trap ..................................................................................... 12 Case Studies: ........................................................................................................................................... 13 Example one – Hobby hen farmer who implemented preventive actions during the trial. ............... 13 Example two – Certified organic vegetable and egg farmer was able to curb the rat infestation after the hens had left the coop. ................................................................................................................. 15 Example three – Preventive measures not followed. ......................................................................... 17 Lack of preventive measures and misapplication of anticoagulant rodenticides .................................. 19 Conclusion ................................................................................................................................................... 20 Literature Cited ........................................................................................................................................... 21 2 Acknowledgement This project was made possible with funding provided by Environment and Climate Change Canada. The support of the local farmers in Delta was critical to the success of this project. I am very grateful to the farmers who allowed me to access their properties to trial the piston traps. Executive Summary Secondary rodenticide poisoning of raptors, including species at-risk, is an ongoing issue in southern British Columbia. Controlling rodents using non-toxic options would reduce the amount of rodenticides applied on the landscape and ultimately reduce the risk of exposing non-target species. The intent of this project was to assess the viability of using the Goodnature© piston trap to control rats on farms. The trial was conducted on 10 farms in Delta, British Columbia between October 2020, and February 2021. The piston traps were deployed at nine of the ten sites after documenting the presence of rodents using the Goodnature© lure. Of these nine sites, the piston trap was successful at trapping rodents at eight sites. At four sites rats were humanely destroyed and at the other four sites deer mice were trapped. At site nine, video monitoring only documented feral cats, i.e., no rodents were triggering the cameras or the traps. The video monitoring documented non-target species attracted to the traps when the piston traps were placed outdoors. It is therefore recommended that the Goodnature© blocker be used when the traps are placed outdoors along the perimeter of buildings or fenceposts. The piston traps were most effective at farms where preventive measures were being followed, such as removing food sources and shelter for the rats. The preventive aspect is imperative for the success of any rodent control and was an important outreach message as part of this project. At farms permanently using rodenticides, misapplication and lack of preventive measures were documented. This highlights the ongoing need to work with pest control operators, vendors and farmers providing education on the proper use of rodenticides. 3 Introduction Rodents are a group of pests that are notoriously known for damaging crops and stored grained, in particular in developing countries but also industrialized ones with significant agricultural exports (Geddes 1992; Stenseth et al. 2003; Singleton 2003; Jacob and Buckle 2018). The primary method for controlling rat infestations worldwide, including within the agricultural sector, is through the use of anticoagulant rodenticides (ARs) (Corrigan 2001; Dawson et al. 2004; Lima and Salmon 2010; Jacob and Buckle 2018). The first generation anticoagulant rodenticides (FGARs: warfarin, diphacinone, and chlorophacinone) were introduced commercially in the 1940s, and since then, their widespread use has led to genetic resistance in some rodent populations (Boyle 1960; Buckle et al. 1994; Berny et al. 2018). Second generation anticoagulant rodenticides (SGARs: brodifacoum, bromadiolone and difethialone), introduced in the 1970s, are considerably more toxic, persistent and bioaccumulative compared to FGARs, and are capable of killing target rodents after a single feeding (Eason et al. 2002; Fisher et al. 2003). Currently, SGARs are the most widely used compounds, especially by professional rodent control operators and farmers (Corrigan 2001; Elliott et al. 2016; Hindmarch et al. 2018). Annual sales of rodenticide products are projected to surpass one billion dollars this year (Zion Market Research 2021). The toxic and persistent nature of SGARs and their widespread use has had consequences beyond controlling rodents. Exposures and poisoning of non-target wildlife, particularly the secondary poisoning of raptors is increasingly being documented worldwide (Eason et al., 1999, 2002; Stone et al. 1999; Brakes 2005; Riley et al. 2007; Walker et al. 2008; Albert et al. 2010; Murray, 2011, 2020; Thomas et al., 2011; Christensen et al. 2012; Nakamaya et al. 2018). Secondary exposure of raptors has also been well documented in the Fraser River Delta in southwestern British Columbia (Albert et al. 2010; Elliott et al. 2014; Huang et al. 2016). During the mid-19th century, the low-lying lands in the region were diked and converted to agricultural fields that were primarily used for pasture and hay production. However, during the past 60 years, significant amounts of farmland has been converted to greenhouse vegetable production and berries (Elliott et al. 2011; Metro Vancouver 2012). Both crop types require more intensive rodent control than grass fields to ensure that plants and produce are not damaged when being produced and stored. Since 2008, vegetable farmers and greenhouse facilities are obligated to maintain rodent control programs as part of government administered food safety standards (CanadaGAP 2021). Hindmarch et al. (2018) surveyed farmers in Delta, British Columbia and found that 94% of farmers applied ARs to control rodents, of which 37% were applying SGARs permanently as part of their food safety program. Consequently, barns processing vegetables and greenhouses are often permanently baited with the SGAR bromadiolone along the outdoor perimeter. The Fraser River Delta agricultural landscape is home to several listed predators such as barn owls (Tyto furcata), long-eared owls (Asio flammeus), and great blue herons (Ardea herodias), all of which depend on rodents as a key food source. Barn owls in particular are closely tied to the agricultural landscape and nest inside barns, riding arenas or other barn structures. They were recently upgraded to threatened in southwestern British Columbia, primarily due to the loss of habitat, but AR exposure/toxicosis is identified as a threat to the western population of barn owls (SARA 2018, COSEWIC 2010). Huang et al. 4 (2016) showed that barn owls sampled between 2006 – 2013 had significantly higher AR residue concentration when compared to individuals sampled in 1992 – 2003. Barn owls and other raptors are rodent specialists and can be the farmers’ allies in combating rodent problems, hence there is a need to find rodent control methods where raptors can be part of an integrated pest management solution, without the risk of being poisoned. Ensuring that non-toxic control options are considered first, and rodenticides are only used as a last resort will help reduce this threat. The objective of this trial was to assess the effectiveness of using a non-chemical, instant kill, self- resetting piston trap (A24 Goodnature© trap) on farms in Delta, BC. The piston trap works by shooting a CO2 powered piston into the head of a rodent that climbs inside the trap. The rodent triggers the piston when trying to eat the lure inside the cap of the trap and once dead will drop down to the ground where it can be safely scavenged by other animals. The trap automatically resets and can trigger up to 24 times on one CO2 -cylinder. Specifically, this trial will evaluate: • whether piston traps can reduce the damage and presence of rats on farms, • the most effective way to install and attract rats to the piston trap, and • risk of non-target bycatch Methods Study Area I conducted the trial in Delta, British Columbia, a municipality that has been one of the main areas where raptors have been tested routinely for ARs since the early 2000s (Albert et al. 2010; Huang et al. 2016). Delta lies at the mouth of the Fraser River and consists predominantly of low-lying floodplains, with some forested areas further inland (Fig. 1). In the 1850s, European immigrants settled in the area and claimed land for farming by diking the foreshore (North and Teversham 1983). Delta is also recognized as an important bird area, as it includes some of the main stop-over sites for birds migrating on the Pacific flyway (Important Bird Areas 2021). Further, important wildlife areas such as the Alaksen National Wildlife Area, Burns Bog and Boundary Bay provide vital year-round habitat for resident raptors and overwintering birds. However, low lying productive shoreline habitats often face strong development pressures (McKinney 2002), and Delta is no exception. Ongoing infrastructure and housing projects continue to encroach on and fragment the land, making it less viable for farming. Development pressure and speculation has also increased the cost of land and triggered a shift from traditional grassland-associated agriculture to more intensive cash crops such as greenhouse and berry production, which has resulted in less grass vegetation, and therefore decreased habitat for raptors (Metro Vancouver 2012). 5 Piston Trap Trial The piston trap (aka A24) was developed by the New Zealand company Goodnature© in 2011, with the intent of providing a humane and toxin free control option for invasive rats and possums in New Zealand (Fig 1). The company has expanded its operations and has currently distributors in North America, Europe and Australia, in addition to New Zealand. Figure 1. The Goodnature© rodent trap works by attracting the rat to the trap using a long-life rodent lure. To access the lure, the rat triggers a sensitive pin (in red) that sets the trap in motion and a CO2 pressurised piston (in orange) strikes the rodent’s head killing it instantly and then retracts on a light spring. The dead rodent falls to the ground and the trap automatically resets itself ready for the next rat to arrive. In total 20 piston traps were installed on farms in Delta and monitored weekly. The sites chosen were not currently using rodenticides, but five had previously deployed rodenticides and two farms were using snap traps during the trial. The deployment of the piston traps followed the recommendations set by Goodnature©. The initial step was to identify where the rats felt comfortable eating. Unlike rodenticides placed inside a bait station, the piston traps do not provide the rat with an enclosed and safe area to eat. Goodnature© recommends pre-applying their long-life lure (toxin-free, tastes sweet and smells of chocolate) in several locations so you can identify where a rat feels comfortable eating. The piston trap kit comes with six small lure packs that can be installed in and outside structures where there is evidence of rats (i.e., rat tunnel openings, feces, gnawing and damage to structures). At each farm site lure packs were installed at 5-6 locations and monitored weekly for uptake (Fig 2). Lure packs that had been completely eaten were replaced with piston traps. The traps were not initially set, but lure was added in the lure cap and added in small portions next to the piston trap to continue to get the rats interested in the lure and comfortable with the traps (Fig 3). After 1-2 weeks of lure baiting the 6 piston traps were set, and lure was only applied to the base of the trap and inside the lure cap. To create a sense of safety for the rats, I would in some locations place a small piece of plywood on an angle over the lure and the piston traps (Fig 4). A selected 2-3 lure packs or traps at each site were monitored with wildlife cameras to help determine the presence of rats and the behaviour exhibited by rats at the traps. The video monitoring also allowed me to assess whether non-target animals would access the traps. The cameras were set to record for 10 seconds when triggered with a 10 second rest period in between. Figure 2. Lure pack on post. 7 Figure 3. Piston trap set-up with camera. Figure 4. To provide the rats with a sense of security, I placed a small piece of plywood over the lure pack or piston trap in exposed locations. This also prevented hens from pecking on the equipment. 8 Results and Discussion Between October 2020 and February 2021, the trial was conducted on 10 farms in Delta (six livestock farms, three vegetable/berry farmers, and one equestrian facility, with hens for their own egg consumption. The farmers that were interested in participating had experienced (n=6) or were currently dealing with a severe rat infestation on their farm (n=4). Nine of ten identified farms were suitable for trap deployment. At the 10th site, the farmer followed preventive measures such as keeping the perimeter of the barn clean, and the barn was currently being used for equipment storage, so there were no food attractants in the barn. None of the lure packs were chewed and there were no signs of rodents. At all sites, rats where the main pest rodent, however, at five sites the farmers would also control for mice when needed. In total, the piston traps were triggered by rats at four farms (n=19), all of which were placed inside hen coops and deer mice triggered the piston traps at another four farms (n=14). At one farm, none of the piston traps were set off and the camera was only triggered by feral cats (Table 1). The video footage did confirm cannibalism by both deer mice and rats (Fig 5). Figure 5. Cannibalism was documented by both rats and deer mice, as depicted on this picture, a deer mouse is eating a dead conspecific. 9 Deer mice attracted to the piston traps The video monitoring showed that deer mice did not hesitate to eat the Goodnature© lure and enter the piston trap, demonstrating that the trap was also effective at controlling for deer mice. In general, at sites where both rats and deer mice were present, the mice were more frequently seen eating the lure on video footage than rats and were more commonly observed entering the piston trap (Fig 6). Initially, the piston traps were triggered by deer mice at two sites. Therefore, I removed the set piston traps, as deer mice were not a target species at either farm. However, I continued video monitoring at the sites with piston traps that were not set, to see whether other non-targets were attracted to the trap. To prevent deer mice, songbirds and other non-targets from entering the traps I trialled the A24 blocker, which is intended to prevent non-targets from entering the piston trap. However, video monitoring of the piston traps with the blocker showed that the deer mice were not deterred from entering the trap. The blocker seemed to prevent grey squirrels and possums, and would, as suggested by Goodnature©, also prevent smaller pets from entering the traps. There was one farm site where deer mice were an issue, as they were getting inside the barn where vegetables were being stored, and one piston trap placed strategically by the cold storage unit killed 10 deer mice over a four-week period. As a side note, post deployment, some of the traps that were set and could not be disarmed due to pressurized CO2 inside the trap, were stored in a cardboard box in my garage. Within two days of being stored, three deer mice had found their way into the box and triggered two of the three traps. Figure 6. Deer mouse eating the lure around the piston trap. Deer mice were less hesitant than rats to enter the piston traps and were more frequently seen on video footage compared to rats. 10 Table 1. Summary of sites where the piston trap trial was conducted and the number of rats and deer mice that were humanely destroyed using the piston trap. Site Type Piston Rats Deer Preventive Comments Traps Mice measures1 Deployed 1 Vegetables Yes 9 0 Somewhat 2 Vegetables Yes 0 10 Good 3 Vegetables Yes 1 Not followed & Berries 4 Equestrian Yes 2 0 Implementing and Hens/Eggs 5 Dairy Yes 0 0 Somewhat No rodents documented on camera 6 Hay Yes 0 2 Not followed 7 Hens/Eggs Yes 4 0 Good 8 Hay Yes 0 1 Not followed 9 Hens/Eggs Yes 4 0 Implementing 10 Cows No 0 0 Good No lures eaten SUM 19 14 1 Categories: Not followed, somewhat, good, implementing. 11 Non-target species attracted to the piston trap Video monitoring documented other non-target species attracted to the lure in the piston trap. For example, a grey squirrel and a possum were seen eating the lure. In both instances, the blocker prevented the larger mammals from entering the piston trap (Fig 7). At one site, a winter wren was seen on several occasions around the piston trap and at another site a song sparrow. Neither species was observed eating the lure. However, a concurrent project trialing the piston traps in berry fields did document a junco being humanely destroyed when the attractant in the piston trap was peanut butter. As songbirds and other mammals might enter the piston traps, I would recommend using the blocker when the trap is placed outdoors along the perimeter of buildings or on fenceposts. Figure 7. Video footage of non-target species seen around the piston trap (i.e., winter wren and song sparrow) or eating the Goodnature© lure (i.e., grey squirrel and possum). Clockwise from top left: winter wren, grey squirrel, possum, song sparrow. 12 Case Studies: Example one – Hobby hen farmer who implemented preventive actions during the trial. The farmer has laying hens for personal egg consumption and local sales and had never had any previous problems with rats until the fall of 2020. The rats were getting into the hen coop and chewing their way into other parts of the barn. The farmer was initially using a bromadiolone rodenticide product to control the rats, but the rats were not eating the bait. During my initial site visit, I recorded several large burrows dug by the rats along the perimeter of the hen coop, providing the rats with easy access to the fenced outdoor area for the hens. Fortunately, the farmer was already in the process of implementing various preventive measures such as blocking entry points into the barn area where the hens were fed and locked up overnight with metal sheeting. This prevented the rats from entering the barn and having access to the hen food overnight. I installed five lure cards during my initial site visit, and after two weeks all the lure cards were completely eaten (Fig 8). I subsequently installed three piston traps at locations where the chew cards had been eaten, but did not set the traps, and continued pre-baiting the traps with the lure as recommended by Goodnature©. Rats are neophobic and wary of new things in their environment, so continuing to pre-bait the piston traps would allow the rats to get used to and comfortable eating from the piston traps. After ten days the traps were set, and four rats were killed the first week of deployment. On the first night of deployment the camera footage revealed that one rat carcass was removed by another rat, 30 minutes after it had been killed (Fig 9). It is interesting to note that no more rats were killed after the initial week of deployment, even though rats were still detected on the cameras. We also tried baiting the piston traps with the hen food, as this was a food source the rats were familiar with, but none of the piston traps were triggered. Regardless, the farmer did find that the rats were now manageable and continued to ensure that the rats were not able to access the inside of the barn. We removed the piston traps two months after initial deployment. Figure 8. The chew cards were completely eaten after two weeks and the hens were more than happy to help with the deployment of the piston traps. 13 Figure 9. Rat killed the evening the piston traps were set, dead rat was dragged away from trap site 30 minutes after it was killed, and new rat emerges. 14 Example two – Certified organic vegetable and egg farmer was able to curb the rat infestation after the hens had left the coop. The farm is a certified organic vegetable and egg farm. The rats had been an issue in the hen coop for the last three months, and they had managed to get inside the walls and eaves resulting in them eating spilled food at night (Fig 10). The farmer was actively trying to trap the rats and had some success with snap traps, but not enough to curb the infestation. Figure 10. Camera footage documented that the rats were getting inside the hen coop at night eating spilled food. Three rats can be seen in this picture. Only two of the six lure cards were eaten after they had been in place for a week, but this helped guide the installation of two piston traps, each monitored with a camera. The piston traps were set when they were initially installed, as this was prior to my conversation with Goodnature© about pre-baiting the piston traps before setting them (i.e., to get the rats used to the trap and comfortable eating inside the trap where the metal pin that triggers the trap is located). The camera revealed that there were lots of rats around, one camera had been triggered over 600 times in two weeks, often documenting two or three rats during the 10 second recording interval. The rats were eating the Goodnature© lure around the trap but did not want to enter inside the piston trap, and consequently neither trap had been triggered. The rats’ hesitancy to enter the piston traps could also be explained by the fact that there was a lot of spilled hen feed available to them inside hen coop, and hence no incentive for them to further 15 investigate the piston traps. However, this changed two months post deployment, as the hens were culled on December 22nd, 2020 and the hen coop was left empty. The rats started to enter the piston traps January 10th onwards and a total of nine rats were killed over a three-week period (Fig 11). The farmer also noted an uptake in snap traps during the same period and as of mid-February no more rats were seen in the hen coop and the traps were removed. The intent is to have a new batch of hens in the coop in the future, so I highly recommended that this would be a good time to perform preventive actions such as sealing up the eaves and walls, making the hen coop rat proof. This will reduce the likelihood of a future rat infestation and make it easier to trap rats that are trying to access the coop. Figure 11. After the hens were culled and there was no more hen feed the rats started to take to the piston traps with a total of nine rats killed in a three-week period. 16 Example three – Preventive measures not followed. This site is an equestrian facility with a small hen flock for own egg consumption. The facility was currently experiencing a rat infestation in the room they stored horse feed and in the hen coop. On my initial site visit I noted that the rats had easy access to the horse feed room during the day when the door was open, but camera footage also revealed that the rats were able to access the room at night (Fig 12). The horse food was stored in plastic and metal containers but there was spillage providing the rats with an abundant and desirable food source. There was a similar situation in the hen coop, as the hens were feed outside in a fenced area and rats were observed eating alongside the hens in the daytime and there were several rat tunnels and burrows underneath the hen coop (Fig 13). I do not think the rats had access to the hen house where the hens slept overnight, but in all likelihood the spillage of hen food in the fenced day coop provided the rats with sufficient food overnight. Figure 12. The rats were able to acces the horse feed room and rat feces was observed on shelving, and the presence of rats was also confirmed on camera footage. I installed five lurecards in the horse feed room and four in the hen coop. Interestingly, throughout the trial period none of the lurecards placed in the horse feed room were chewed. The video monitoring documented at least three rats, but the abundance of spilled horse feed provided the rats with ample food options, and no incentive to try out the lure cards. The four lure cards placed in the hen coop were all eaten in one week, and four piston traps were installed in the fenced area of the hen coop. Two rats were killed in a two week period, but then there was no uptake and rats were still seen in the daytime and on video footage taken at night. During this trial period none of the preventive measures were introduced, and the rat infestation is ongoing. I discussed preventive options with the owner, such as rat proofing the horse feed room, and options for reducing the spillage of hen feed. She was considering implementing some of these measures in the near future. 17 Figure 13. Rat eating spilled hen food in fenced area of hen coop alongside songbirds. 18 Lack of preventive measures and misapplication of anticoagulant rodenticides Rat control is most effective and sustainable if preventive measures such as removal of food sources, litter and rat proofing structures are implemented before any form of rodent control is conducted (Corrigan 2001: CRRU 2015). However, in many instances, preventive actions intended to reduce the carrying capacity of rats in the environment were not conducted prior to rodent control. During this pilot project, I documented three instances where rodenticides had been applied. Two of which were not following best management practices. At the first site, which was managed by a professional pest control company, adequate preventive actions were not implemented (Fig 14). The second site had an ongoing rat infestation and the landowner had purchased a bucket of a rodenticide product that was for indoor use only (active ingredient: brodifacoum) but was recommended by the vendor to use this product to control rats outside. Lack of preventive actions both by landowners and hired pest control operators, and misapplication of rodenticides has been previously documented in Delta (Hindmarch et al. 2018). Figure 14. Bait station seen in background, which was serviced bi-weekly by pest control operator but no preventive actions such as removal of litter and rodent proofing structures was conducted. 19 Conclusion Overall, the piston traps were triggered at eight of the nine sites they were deployed, and no rats or deer mice were documented at the ninth site. The most important factor to increase the success of the piston traps was to ensure that preventive measures were followed, such as removing food sources and shelter for the rats. Rats are neophobic and will not try new food sources if they already have a steady supply of food available to them through familiar and easily accessible stored/spilled animal feed or food waste (Fig 15). This was also apparent from this study, as in all cases the success rate of trapping rats increased when food sources and hiding places were eliminated. The most successful trap sites had excluded rats from entering the hen coop, or the hen food was no longer available to the rats. The study demonstrated that piston traps were also effective when controlling for deer mice. Based on our video monitoring they were the most frequently documented species eating the Goodnature© lure and entering the piston trap at farms where rats were also present. Figure 15. Rats will not be interested in the Goodnature© lure pack as seen here fastened to the side of this pallet if they already have a safe and proven food source in easily accessible animal feed. Non-target species such as squirrels, possums and songbirds might be attracted to the piston trap if they are installed outdoors along the perimeter of buildings or fenceposts. In such cases, I would highly recommend using the Goodnature© blocker on the piston trap as this will discourage non-target species, including pets from entering the trap. As has been previous documented in this region (Hindmarch et al. 2018), anticoagulant rodenticides were in some cases permanently used as a first line of defense against rodents. At one site, preventive measures such as removal of litter and rodent proofing the structure were lacking, which was concerning given that the site was managed by a professional pest control operator. Applying indoor only products outdoors was also documented at another site where spilled animal feed was readily available for the rats. These examples point to two ongoing challenges: ensuring that preventive 20 measures are the first line of defense against rodents, and that vendors selling rodenticide products are well informed on product application and regulations. One drawback with the Goodnature© trap, which was noted by a couple of farmers, is the cost. A Goodnature© trapping kit presently sells for 278$, which is considerably more expensive than rat snap traps of which the cheapest retails for ~ 10$. However, the appeal of the Goodnature© piston trap is that it is self resetting up to 24 times on one CO2 cylinder, which means that it requires minimal maintenance and there is no need to remove dead rodents from the trap before it can be reset. In conclusion, the piston trap is a viable control option that can be used to successfully control rodents on farms in Southern British Columbia. 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