Academic literature on the topic 'Bait aversion'

Development of aversions, or learned ‘bait-shyness’, in frequently poisoned possum (Trichosurus vulpecula) populations is becoming increasingly detrimental to the efficacy of pest-control operations in New Zealand. This experiment aimed to identify the effects of prefeeding, a common management procedure, on the subsequent development of aversions in possums. Wild possums (n = 96) were captured and acclimatised, then allocated to one of three treatments groups that for seven days received either (i) no prefeed, (ii) plain RS5 cereal baits, or (iii) green-dyed and cinnamon-lured RS5 cereal baits. The possums were then offered a standard green-dyed and cinnamon-lured RS5 bait that contained a sublethal dose (0.4 mg kg-1) of the toxin sodium monofluoroacetate (1080). The possums were tested for development of an aversion towards a toxic RS5 1080 bait, a prefeed bait, and a prefeed bait containing an alternative toxin, brodifacoum. Most (96%) of the non-prefed possums became averse to the 1080 bait after two exposures, compared with only 55% and 9% of the two prefed groups. Similarly, 90% and 92% of the non-prefed possums were averse to prefeed and brodifacoum baits, respectively, compared with 8% and 14% of the prefed possums. This suggests that pest managers can reduce the risk of ‘bait shyness’ by prefeeding. A further advantage of prefeeding is that if poison shyness develops, use of an alternative toxin such as brodifacoum in the original bait base may still be successful.

The proportion of possums with cyanide-shyness was assessed in four populations and ranged from 12 to 54%. These results supported anecdotal evidence of cyanide-shyness and showed that the problem could be significant in some populations. Non-toxic baiting with rhodamine dye as a marker indicated that more than 90% of possums were willing to accept the bait material, and pen trials showed that possums were able to eat the bait material but reject the cyanide paste placed in the bait. Shyness was therefore not a result of bait aversion but of direct rejection of the toxin. Attempts to induce shyness in possums by feeding them sublethal doses of cyanide, and the history of cyanide use in the trial areas, support the theory that at least in some areas cyanide-shyness is not a result of previous exposure (learned aversion) but of primary aversion. Current research to produce cyanide formulations with low emission rates of hydrogen cyanide aims to make the toxin effective even in areas where cyanide-shyness has developed.

The behavioural responses of captive possums (Trichosurus vulpecula) were observed during first encounters with non-toxic and toxic carrot and pellet baits used in pest control programmes. Possums confronted with new baits first used smell in a highly discriminating way, and then taste, which sometimes changed their initial response. Toxic carrot baits were rejected by 27.5% of possums, equally by smell and taste aversion, and toxic pellet baits by 34% of possums, mainly by taste aversion. Few (5-7%) rejected non-toxic baits. Such non-learned aversion mechanisms therefore have an important role in the feeding behaviour of possums. A range of flavours tested, using barley as a food base, showed that only orange-flavored barley was significantly preferred to non-flavoured barley; 19 flavours had no significant effect, and 19 others significantly reduced barley consumption. Orange and cinnamon, which was ranked fourth and repels some bird species, were tested as masks for 1080 baits. Both flavours effectively masked the aversive smell and taste of 1080. The levels of toxic flavoured bait rejection were low and did not differ from those of non-toxic (flavoured or non-flavoured) baits. Very few possums were observed vomiting, a behaviour in other species that may assist survival.

Currently, most cockroach control in urban environment relies on bait application. Aversion of some commercial bait by cockroach cause failure to control cockroach problems. Developing local bait can improve this situation. This research was aimed to find proper combination of some cockroach diet to be formulated in effective bait. Research was conducted in Department of Plant Protection, Bogor Agricultural University, since November 2007-March 2008. Combination of peanut butter, chicken egg, and strawberry jam seem to be a candidate of effective bait for local cockroach.

Context Poison baits are often used to control both foxes and feral cats but success varies considerably. Aims This study investigated the influence of bait type, placement and lures on bait uptake by the feral cat, red fox and non-target species to improve baiting success and reduce non-target uptake. Methods Six short field trials were implemented during autumn and winter over a five-year period in northern South Australia. Key results Results suggest that poison baiting with Eradicat or dried kangaroo meat baits was inefficient for feral cats due to both low rates of bait detection and poor ingestion rates for baits that were encountered. Cats consumed more baits on dunes than swales and uptake was higher under bushes than in open areas. The use of auditory or olfactory lures adjacent to baits did not increase ingestion rates. Foxes consumed more baits encountered than cats and exhibited no preference between Eradicat and kangaroo meat baits. Bait uptake by native non-target species averaged between 14 and 57% of baits during the six trials, accounting for up to 90% of total bait uptake. Corvid species were primarily responsible for non-target uptake. Threatened mammal species investigated and nibbled baits but rarely consumed them; however, corvids and some common rodent species ingested enough poison to potentially receive a lethal dose. Conclusions It is likely that several factors contributed to poor bait uptake by cats including the presence of alternative prey, a preference for live prey, an aversion to scavenging or eating unfamiliar foods and a stronger reliance on visual rather than olfactory cues for locating food. Implications Further trials for control of feral cats should concentrate on increasing ingestion rates without the requirement for hunger through either involuntary ingestion via grooming or development of a highly palatable bait.

Shyness to sodium monofluoroacetate (1080) in cereal bait can persist in sub-lethally poisoned possum (Trichosurus vulpecula) populations for at least 2 years. We investigated the use of non-toxic cereal ‘prefeed’ and ‘postfeed’ as ways of inhibiting and overcoming such shyness. The postfeed result was also compared with changing to a non-cereal, gel-based 1080 bait. Prefeeding had a significant effect on the number of possums that became ‘bait shy’ following an approximate LD20 1080 dose, with 97% of non-prefed possums developing an aversion to 1080 cereal bait compared with only 22% of prefed possums. In contrast, postfeeding with cereal was relatively ineffective in reducing the number of 1080 bait-shy possums, with mortality of these possums being 30% compared with 0% of non-postfed possums. In contrast, the gel 1080 bait killed 64% of 1080 cereal bait-shy possums. These results suggest that 1080 bait shyness can be markedly reduced by prefeeding non-toxic bait to possums prior to each control operation. However, this may not be the most cost-effective control option, given the observed efficacy of follow-up baiting with 1080 gel.

‘Bait-resistance’ is defined as progressive decreases in bait efficacy in controlled pest species populations. Understanding the mechanisms by which bait-resistance can develop is important for the sustainable control of pests worldwide, for both wildlife conservation programs and agricultural production. Bait-resistance is influenced by both behavioural (innate and learned bait-avoidance behaviour) and physiological aspects of the target pest species (its natural diet, its body mass, the mode of action of the toxin, and the animal’s ability to biochemically break down the toxin). In this review, we summarise the scientific literature, discuss factors that can lead to innate and learned aversion to baits, as well as physiological tolerance. We address the question of whether bait avoidance or tolerance to 1080 could develop in the red fox (Vulpes vulpes), an introduced predator of significant economic and environmental importance in Australia. Sublethal poisoning has been identified as the primary cause of both bait avoidance and increased toxin-tolerance, and so, finally, we provide examples of how management actions can minimise the risk of sublethal baits in pest species populations.

Aerial control using 1080 (sodium monofluoroacetate) baits is widely used in New Zealand for the control of introduced brushtail possums (Trichosurus vulpecula), with the aim of protecting national conservation and agricultural values from these damaging pests. This thesis integrates research, completed over 25 years, that was motivated by growing recognition in the 1970s of the extent of possum impacts and the need to improve the effectiveness and efficiency of the control operation. Field research assessed the palatability of three types of cereal-based pellet baits and carrot baits in different regions, habitat types and seasons. Palatability was assessed by the consumption of the different bait types presented independently of each other on 15-30 plots, with rotation of bait types at plots on successive nights to provide equal exposure to each bait type. There was regional variation in possums' bait preferences, possibly reflecting genotypic differences, whereas seasonal variation was less evident. Carrot bait was preferred or equally preferred to cereal bait in 14 out of 20 field trials. The proportion of possums eating baits was then investigated by, firstly, developing a technique for tracing bait acceptance using rhodamine B, a UV-fluorescent dye. In four field trials, more than 95% of possums accepted three types of dye-marked bait, eliminating bait refusal as a major reason for low kills in winter control operations. In a fifth trial, conducted in summer, only 68% of possums accepted bait suggesting that seasonal availability of favoured foods may influence bait acceptance. Since possums must encounter baits before deciding whether to eat them, field studies were undertaken to assess the coverage achieved in normal aerial baiting operations. Large gaps, up to 400 m in width, were often found between baiting swaths; these could allow some possums to survive. A controlled field experiment, using acceptance of rhodamine-dyed bait as a measure of effectiveness, showed that bait distribution was least accurate where flight paths were not marked. Where gaps of 100 m between flight paths were deliberately created, bait acceptance was slower and less than where coverage was complete. Sowing baits at 3 kg/ha was as effective as at 10 kg/ha, indicating the potential for substantially reducing operational costs by using machinery capable of faultlessly distributing baits at low rates. Navigational guidance systems were evaluated and found to improve the accuracy of bait distribution. During 1993-1997, when a lower sowing rate of 5 kg/ha was adopted operationally by regional managers, control effectiveness was unchanged but annual savings of around $9 million accrued. Because of the lack of suitable sowing machinery, a bucket was developed to permit faultless distribution of baits at lower rates, demonstrating the possibility of yet further cost-savings. The possibility of seasonal food availability affecting bait acceptance was investigated in three different forest habitats. Dyed baits were aerially distributed on 100 ha at each site in each season over two years. In each trial, fat-based condition indices of possums were calculated and the abundance of possum-preferred plant foods described. Bait acceptance was consistently high (85-100%) in the 24 trials, and was not influenced by either condition or availability of preferred foods. It seems likely that seasonal variation in operational effectiveness is caused by either the availability of sharply seasonal, scarce foods that possums may feed on intensively for brief periods, or by warmer temperatures that render 1080 less effective. The influence of 1080 on acceptance of (rhodamine-dyed) baits was investigated in a field trial. Examination of possums for dye-marking showed that 25% of possums refused to eat either a lethal quantity of bait or any bait at all, compared with 98% of possums eating non-toxic bait. This indicated that 1080 is aversive to possums, which is a potential major reason for their surviving control operations. Pen trials were therefore conducted to further examine the problem and to seek solutions. Toxic carrot baits were rejected by 27.5% of possums, equally by smell and taste aversion, whereas toxic cereal pellets were rejected by 34%, mainly by taste aversion. Orange and cinnamon were shown to be among the most preferred of 42 flavours tested and, when applied to toxic baits, 1080 was effectively masked. Bait refusal was reduced to ≤7%, the same as that recorded for possums presented with flavoured non-toxic baits. For long-term control of possum populations, aerial 1080 baiting can be used sequentially with other poisoning methods. However, the compatibility of these methods is dependent on the likelihood of possums developing bait shyness if sublethally dosed. Studies were therefore conducted to characterise and compare the four main toxicants used (1080, cyanide, cholecalciferol and brodifacoum) for induction and mitigation of bait shyness. Shyness was induced in approximately 80% of possums sublethally dosed with cyanide, 60% with 1080, 20% with cholecalciferol, and 0% with brodifacoum. Cyanide and 1080 shyness were found to persist in many possums for at least 12 and 24 months, respectively. Use of alternative bait types, and of baits containing an alternative slow-acting toxin (brodifacoum) were shown to be effective ways of overcoming shyness. This, and other related research, is reviewed to provide operational specifications that maximise the likelihood that all targeted possums will (i) encounter bait, (ii) eat it, and (iii) die. The likely future use of aerial 1080 baiting is described and the technological, economic, environmental and social constraints on its sustainability are discussed. Finally, the uptake of the research by possum managers is considered, and areas identified in the thesis where information is incomplete are summarised as prioritised topics for further research.

In Canada, bail supervision programs were developed, in partnership with community-based organizations, to promote bail compliance and provide supervision to accused persons who would otherwise have been detained in remand custody. While many of these programs use traditional risk assessment tools to guide supervision, limited research has been conducted on their effectiveness in the bail supervision context. Adopting a quantitative as well as qualitative methodology, this study uses a representative sample of 100 supervision clients from one Ontario bail program to examine the validity of its risk tool – Service Planning Instrument™ (SPIn) Pre-Screen – as well as demographic and criminal justice factors, in predicting bail supervision outcomes. Analyses suggest that SPIn lacks predictive validity in the bail supervision setting. These findings are discussed within the broader context of net widening, as well as the greater bail/remand crisis and the culture of risk aversion that pervades the Canadian criminal justice system.

Thesis (M. Sc.)--York University, 2001. Graduate Programme in Biology.
Typescript. Includes bibliographical references (leaves 31-38). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ66401.

The relationship between gender and bail is an important yet understudied area of research. Studies that have found a relationship between gender and bail generally overlook important differences that shape how men and women enter into crime and the types of conditions imposed on their recognisances. This study utilizes 115 bail cases from the Provincial Courthouse in Kitchener, ON to examine the effect of accused gender on bail outcome. Results show that accused gender did influence decisions to grant or deny bail. While almost all accused persons required a surety and/or bail conditions to be released, the regression analysis suggests that women were more likely to be released compared to men. Based on the deep sample exploratory analysis, gender differences emerged around issues of mental health and drug use. Theoretical and policy implications from this study are discussed as are avenues for future research.

The question of whether or not to release an accused on bail pending case resolution involves an evaluation of the risk the accused poses to the community. In addition to this evaluation, the risk posed to the reputation of the criminal justice system should the accused re-offend while on bail has come to influence the timeliness of the bail decision as well as the conditions of the release order. It appears that questions of institutional risk have intensified strategies of process, whereby the bail decision making process has come to take considerably longer as court actors postpone making the release decision. This organizational culture of risk aversion is evidenced in the growing remand population, the dominance of adjournment requests, the presumption of surety supervision, as well as the imposition of numerous restrictive conditions of release that are questionably related to the grounds for detention and allegations of the offence. Due to the additional protections contained in the Youth Criminal Justice Act (YCJA), the expectation is bail should be more liberally used for youths. However, despite the additional legislated protections, bail practices for both adults and youths are operating in remarkably similar ways. Indeed, it appears that routine bail practices for both adults and youths are inconsistent with the essential principles of the bail process. In Canada there is a presumption in favour of release on bail and a presumption of release on the least restrictive form of release appropriate in the circumstances. Despite these principles there has been a relatively steady increase in the size of the remand population in Canada. Focusing on the situation in Ontario, this dissertation examines the bail process in an effort to understand how the remand population has come to exceed the population of sentenced prisoners in provincial prisons for both adults and youths.